vendor/llvm/llvm-trunk-r300422

61 files changed, 3068 insertions, 1173 deletions

diff --git a/lib/MC/CMakeLists.txt b/lib/MC/CMakeLists.txt
index 2f1b39e58e33..a86fd383003d 100644
--- a/lib/MC/CMakeLists.txt
+++ b/lib/MC/CMakeLists.txt
@@ -6,6 +6,7 @@ add_llvm_library(LLVMMC
   MCAsmInfoCOFF.cpp
   MCAsmInfoDarwin.cpp
   MCAsmInfoELF.cpp
+  MCAsmInfoWasm.cpp
   MCAsmStreamer.cpp
   MCAssembler.cpp
   MCCodeEmitter.cpp
@@ -34,17 +35,21 @@ add_llvm_library(LLVMMC
   MCSectionCOFF.cpp
   MCSectionELF.cpp
   MCSectionMachO.cpp
+  MCSectionWasm.cpp
   MCStreamer.cpp
   MCSubtargetInfo.cpp
   MCSymbol.cpp
   MCSymbolELF.cpp
   MCTargetOptions.cpp
   MCValue.cpp
+  MCWasmObjectTargetWriter.cpp
+  MCWasmStreamer.cpp
   MCWin64EH.cpp
   MCWinEH.cpp
   MachObjectWriter.cpp
   StringTableBuilder.cpp
   SubtargetFeature.cpp
+  WasmObjectWriter.cpp
   WinCOFFObjectWriter.cpp
   WinCOFFStreamer.cpp
 
diff --git a/lib/MC/ConstantPools.cpp b/lib/MC/ConstantPools.cpp
index 9608c2c656b7..8c94e2780998 100644
--- a/lib/MC/ConstantPools.cpp
+++ b/lib/MC/ConstantPools.cpp
@@ -1,4 +1,4 @@
-//===- ConstantPools.cpp - ConstantPool class --*- C++ -*---------===//
+//===- ConstantPools.cpp - ConstantPool class -----------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -10,13 +10,16 @@
 // This file implements the ConstantPool and  AssemblerConstantPools classes.
 //
 //===----------------------------------------------------------------------===//
-#include "llvm/ADT/MapVector.h"
+
 #include "llvm/MC/ConstantPools.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCStreamer.h"
+#include "llvm/Support/Casting.h"
 
 using namespace llvm;
+
 //
 // ConstantPool implementation
 //
diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp
index a8c88dda6936..ee9c25cda94f 100644
--- a/lib/MC/ELFObjectWriter.cpp
+++ b/lib/MC/ELFObjectWriter.cpp
@@ -11,29 +11,49 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCELFObjectWriter.h"
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallString.h"
-#include "llvm/ADT/StringMap.h"
-#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCExpr.h"
-#include "llvm/MC/MCFixupKindInfo.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCSymbolELF.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/MC/StringTableBuilder.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/Compression.h"
-#include "llvm/Support/Debug.h"
 #include "llvm/Support/ELF.h"
 #include "llvm/Support/Endian.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/SMLoc.h"
 #include "llvm/Support/StringSaver.h"
+#include "llvm/Support/SwapByteOrder.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <map>
+#include <memory>
+#include <string>
+#include <utility>
 #include <vector>
 
 using namespace llvm;
@@ -42,6 +62,7 @@ using namespace llvm;
 #define DEBUG_TYPE "reloc-info"
 
 namespace {
+
 typedef DenseMap<const MCSectionELF *, uint32_t> SectionIndexMapTy;
 
 class ELFObjectWriter;
@@ -99,8 +120,7 @@ class ELFObjectWriter : public MCObjectWriter {
 
   DenseMap<const MCSymbolELF *, const MCSymbolELF *> Renames;
 
-  llvm::DenseMap<const MCSectionELF *, std::vector<ELFRelocationEntry>>
-      Relocations;
+  DenseMap<const MCSectionELF *, std::vector<ELFRelocationEntry>> Relocations;
 
   /// @}
   /// @name Symbol Table Data
@@ -144,6 +164,8 @@ public:
                   bool IsLittleEndian)
       : MCObjectWriter(OS, IsLittleEndian), TargetObjectWriter(MOTW) {}
 
+  ~ELFObjectWriter() override = default;
+
   void reset() override {
     Renames.clear();
     Relocations.clear();
@@ -152,8 +174,6 @@ public:
     MCObjectWriter::reset();
   }
 
-  ~ELFObjectWriter() override;
-
   void WriteWord(uint64_t W) {
     if (is64Bit())
       write64(W);
@@ -222,18 +242,18 @@ public:
 
   void writeRelocations(const MCAssembler &Asm, const MCSectionELF &Sec);
 
+  using MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl;
   bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
                                               const MCSymbol &SymA,
                                               const MCFragment &FB, bool InSet,
                                               bool IsPCRel) const override;
 
-  bool isWeak(const MCSymbol &Sym) const override;
-
   void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
   void writeSection(const SectionIndexMapTy &SectionIndexMap,
                     uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size,
                     const MCSectionELF &Section);
 };
+
 } // end anonymous namespace
 
 void ELFObjectWriter::align(unsigned Alignment) {
@@ -297,9 +317,6 @@ void SymbolTableWriter::writeSymbol(uint32_t name, uint8_t info, uint64_t value,
   ++NumWritten;
 }
 
-ELFObjectWriter::~ELFObjectWriter()
-{}
-
 // Emit the ELF header.
 void ELFObjectWriter::writeHeader(const MCAssembler &Asm) {
   // ELF Header
@@ -370,22 +387,6 @@ uint64_t ELFObjectWriter::SymbolValue(const MCSymbol &Sym,
 
 void ELFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
                                                const MCAsmLayout &Layout) {
-  // Section symbols are used as definitions for undefined symbols with matching
-  // names. If there are multiple sections with the same name, the first one is
-  // used.
-  for (const MCSection &Sec : Asm) {
-    const MCSymbol *Begin = Sec.getBeginSymbol();
-    if (!Begin)
-      continue;
-
-    const MCSymbol *Alias = Asm.getContext().lookupSymbol(Begin->getName());
-    if (!Alias || !Alias->isUndefined())
-      continue;
-
-    Renames.insert(
-        std::make_pair(cast<MCSymbolELF>(Alias), cast<MCSymbolELF>(Begin)));
-  }
-
   // The presence of symbol versions causes undefined symbols and
   // versions declared with @@@ to be renamed.
   for (const MCSymbol &A : Asm.symbols()) {
@@ -900,6 +901,8 @@ void ELFObjectWriter::computeSymbolTable(
 
   StrTabBuilder.finalize();
 
+  // File symbols are emitted first and handled separately from normal symbols,
+  // i.e. a non-STT_FILE symbol with the same name may appear.
   for (const std::string &Name : FileNames)
     Writer.writeSymbol(StrTabBuilder.getOffset(Name),
                        ELF::STT_FILE | ELF::STB_LOCAL, 0, 0, ELF::STV_DEFAULT,
@@ -1037,10 +1040,10 @@ void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
   setStream(OldStream);
 
   SmallVector<char, 128> CompressedContents;
-  zlib::Status Success = zlib::compress(
-      StringRef(UncompressedData.data(), UncompressedData.size()),
-      CompressedContents);
-  if (Success != zlib::StatusOK) {
+  if (Error E = zlib::compress(
+          StringRef(UncompressedData.data(), UncompressedData.size()),
+          CompressedContents)) {
+    consumeError(std::move(E));
     getStream() << UncompressedData;
     return;
   }
@@ -1151,8 +1154,8 @@ void ELFObjectWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
   case ELF::SHT_RELA: {
     sh_link = SymbolTableIndex;
     assert(sh_link && ".symtab not found");
-    const MCSectionELF *InfoSection = Section.getAssociatedSection();
-    sh_info = SectionIndexMap.lookup(InfoSection);
+    const MCSection *InfoSection = Section.getAssociatedSection();
+    sh_info = SectionIndexMap.lookup(cast<MCSectionELF>(InfoSection));
     break;
   }
 
@@ -1172,9 +1175,11 @@ void ELFObjectWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
     break;
   }
 
-  if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
-      Section.getType() == ELF::SHT_ARM_EXIDX)
-    sh_link = SectionIndexMap.lookup(Section.getAssociatedSection());
+  if (Section.getFlags() & ELF::SHF_LINK_ORDER) {
+    const MCSymbol *Sym = Section.getAssociatedSymbol();
+    const MCSectionELF *Sec = cast<MCSectionELF>(&Sym->getSection());
+    sh_link = SectionIndexMap.lookup(Sec);
+  }
 
   WriteSecHdrEntry(StrTabBuilder.getOffset(Section.getSectionName()),
                    Section.getType(), Section.getFlags(), 0, Offset, Size,
@@ -1298,7 +1303,8 @@ void ELFObjectWriter::writeObject(MCAssembler &Asm,
     // Remember the offset into the file for this section.
     uint64_t SecStart = getStream().tell();
 
-    writeRelocations(Asm, *RelSection->getAssociatedSection());
+    writeRelocations(Asm,
+                     cast<MCSectionELF>(*RelSection->getAssociatedSection()));
 
     uint64_t SecEnd = getStream().tell();
     SectionOffsets[RelSection] = std::make_pair(SecStart, SecEnd);
@@ -1351,34 +1357,13 @@ bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
   const auto &SymA = cast<MCSymbolELF>(SA);
   if (IsPCRel) {
     assert(!InSet);
-    if (::isWeak(SymA))
+    if (isWeak(SymA))
       return false;
   }
   return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
                                                                 InSet, IsPCRel);
 }
 
-bool ELFObjectWriter::isWeak(const MCSymbol &S) const {
-  const auto &Sym = cast<MCSymbolELF>(S);
-  if (::isWeak(Sym))
-    return true;
-
-  // It is invalid to replace a reference to a global in a comdat
-  // with a reference to a local since out of comdat references
-  // to a local are forbidden.
-  // We could try to return false for more cases, like the reference
-  // being in the same comdat or Sym being an alias to another global,
-  // but it is not clear if it is worth the effort.
-  if (Sym.getBinding() != ELF::STB_GLOBAL)
-    return false;
-
-  if (!Sym.isInSection())
-    return false;
-
-  const auto &Sec = cast<MCSectionELF>(Sym.getSection());
-  return Sec.getGroup();
-}
-
 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
                                             raw_pwrite_stream &OS,
                                             bool IsLittleEndian) {
diff --git a/lib/MC/MCAsmBackend.cpp b/lib/MC/MCAsmBackend.cpp
index 570f764f6642..fc0aa788f6d3 100644
--- a/lib/MC/MCAsmBackend.cpp
+++ b/lib/MC/MCAsmBackend.cpp
@@ -1,4 +1,4 @@
-//===-- MCAsmBackend.cpp - Target MC Assembly Backend ----------------------==//
+//===- MCAsmBackend.cpp - Target MC Assembly Backend ----------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,14 +7,19 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/ADT/None.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCFixupKindInfo.h"
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+
 using namespace llvm;
 
-MCAsmBackend::MCAsmBackend() {}
+MCAsmBackend::MCAsmBackend() = default;
 
-MCAsmBackend::~MCAsmBackend() {}
+MCAsmBackend::~MCAsmBackend() = default;
 
 Optional<MCFixupKind> MCAsmBackend::getFixupKind(StringRef Name) const {
   return None;
diff --git a/lib/MC/MCAsmInfo.cpp b/lib/MC/MCAsmInfo.cpp
index 3eb8f50de5a8..b9be685cedc4 100644
--- a/lib/MC/MCAsmInfo.cpp
+++ b/lib/MC/MCAsmInfo.cpp
@@ -1,4 +1,4 @@
-//===-- MCAsmInfo.cpp - Asm Info -------------------------------------------==//
+//===- MCAsmInfo.cpp - Asm Info -------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -16,29 +16,14 @@
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCStreamer.h"
-#include "llvm/Support/DataTypes.h"
 #include "llvm/Support/Dwarf.h"
-#include <cctype>
-#include <cstring>
+
 using namespace llvm;
 
 MCAsmInfo::MCAsmInfo() {
-  PointerSize = 4;
-  CalleeSaveStackSlotSize = 4;
-
-  IsLittleEndian = true;
-  StackGrowsUp = false;
-  HasSubsectionsViaSymbols = false;
-  HasMachoZeroFillDirective = false;
-  HasMachoTBSSDirective = false;
-  MaxInstLength = 4;
-  MinInstAlignment = 1;
-  DollarIsPC = false;
   SeparatorString = ";";
   CommentString = "#";
   LabelSuffix = ":";
-  UseAssignmentForEHBegin = false;
-  NeedsLocalForSize = false;
   PrivateGlobalPrefix = "L";
   PrivateLabelPrefix = PrivateGlobalPrefix;
   LinkerPrivateGlobalPrefix = "";
@@ -47,10 +32,6 @@ MCAsmInfo::MCAsmInfo() {
   Code16Directive = ".code16";
   Code32Directive = ".code32";
   Code64Directive = ".code64";
-  AssemblerDialect = 0;
-  AllowAtInName = false;
-  SupportsQuotedNames = true;
-  UseDataRegionDirectives = false;
   ZeroDirective = "\t.zero\t";
   AsciiDirective = "\t.ascii\t";
   AscizDirective = "\t.asciz\t";
@@ -58,40 +39,8 @@ MCAsmInfo::MCAsmInfo() {
   Data16bitsDirective = "\t.short\t";
   Data32bitsDirective = "\t.long\t";
   Data64bitsDirective = "\t.quad\t";
-  SunStyleELFSectionSwitchSyntax = false;
-  UsesELFSectionDirectiveForBSS = false;
-  AlignmentIsInBytes = true;
-  TextAlignFillValue = 0;
-  GPRel64Directive = nullptr;
-  GPRel32Directive = nullptr;
   GlobalDirective = "\t.globl\t";
-  SetDirectiveSuppressesReloc = false;
-  HasAggressiveSymbolFolding = true;
-  COMMDirectiveAlignmentIsInBytes = true;
-  LCOMMDirectiveAlignmentType = LCOMM::NoAlignment;
-  HasFunctionAlignment = true;
-  HasDotTypeDotSizeDirective = true;
-  HasSingleParameterDotFile = true;
-  HasIdentDirective = false;
-  HasNoDeadStrip = false;
-  HasAltEntry = false;
   WeakDirective = "\t.weak\t";
-  WeakRefDirective = nullptr;
-  HasWeakDefDirective = false;
-  HasWeakDefCanBeHiddenDirective = false;
-  HasLinkOnceDirective = false;
-  HiddenVisibilityAttr = MCSA_Hidden;
-  HiddenDeclarationVisibilityAttr = MCSA_Hidden;
-  ProtectedVisibilityAttr = MCSA_Protected;
-  SupportsDebugInformation = false;
-  ExceptionsType = ExceptionHandling::None;
-  WinEHEncodingType = WinEH::EncodingType::Invalid;
-  DwarfUsesRelocationsAcrossSections = true;
-  DwarfFDESymbolsUseAbsDiff = false;
-  DwarfRegNumForCFI = false;
-  NeedsDwarfSectionOffsetDirective = false;
-  UseParensForSymbolVariant = false;
-  UseLogicalShr = true;
 
   // FIXME: Clang's logic should be synced with the logic used to initialize
   //        this member and the two implementations should be merged.
@@ -107,12 +56,9 @@ MCAsmInfo::MCAsmInfo() {
   //   - The target subclasses for AArch64, ARM, and X86 handle these cases
   UseIntegratedAssembler = false;
   PreserveAsmComments = true;
-
-  CompressDebugSections = DebugCompressionType::DCT_None;
 }
 
-MCAsmInfo::~MCAsmInfo() {
-}
+MCAsmInfo::~MCAsmInfo() = default;
 
 bool MCAsmInfo::isSectionAtomizableBySymbols(const MCSection &Section) const {
   return false;
diff --git a/lib/MC/MCAsmInfoCOFF.cpp b/lib/MC/MCAsmInfoCOFF.cpp
index 5b9dd2009f8b..85104484fd40 100644
--- a/lib/MC/MCAsmInfoCOFF.cpp
+++ b/lib/MC/MCAsmInfoCOFF.cpp
@@ -1,4 +1,4 @@
-//===-- MCAsmInfoCOFF.cpp - COFF asm properties -----------------*- C++ -*-===//
+//===- MCAsmInfoCOFF.cpp - COFF asm properties ----------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -13,9 +13,11 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCAsmInfoCOFF.h"
+#include "llvm/MC/MCDirectives.h"
+
 using namespace llvm;
 
-void MCAsmInfoCOFF::anchor() { }
+void MCAsmInfoCOFF::anchor() {}
 
 MCAsmInfoCOFF::MCAsmInfoCOFF() {
   // MingW 4.5 and later support .comm with log2 alignment, but .lcomm uses byte
@@ -41,13 +43,10 @@ MCAsmInfoCOFF::MCAsmInfoCOFF() {
   UseLogicalShr = false;
 }
 
-void MCAsmInfoMicrosoft::anchor() { }
-
-MCAsmInfoMicrosoft::MCAsmInfoMicrosoft() {
-}
+void MCAsmInfoMicrosoft::anchor() {}
 
-void MCAsmInfoGNUCOFF::anchor() { }
+MCAsmInfoMicrosoft::MCAsmInfoMicrosoft() = default;
 
-MCAsmInfoGNUCOFF::MCAsmInfoGNUCOFF() {
+void MCAsmInfoGNUCOFF::anchor() {}
 
-}
+MCAsmInfoGNUCOFF::MCAsmInfoGNUCOFF() = default;
diff --git a/lib/MC/MCAsmInfoDarwin.cpp b/lib/MC/MCAsmInfoDarwin.cpp
index e95cf488cd30..4b2001764e97 100644
--- a/lib/MC/MCAsmInfoDarwin.cpp
+++ b/lib/MC/MCAsmInfoDarwin.cpp
@@ -1,4 +1,4 @@
-//===-- MCAsmInfoDarwin.cpp - Darwin asm properties -------------*- C++ -*-===//
+//===- MCAsmInfoDarwin.cpp - Darwin asm properties ------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -13,9 +13,10 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCAsmInfoDarwin.h"
-#include "llvm/MC/MCContext.h"
-#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCSectionMachO.h"
+#include "llvm/Support/MachO.h"
+
 using namespace llvm;
 
 bool MCAsmInfoDarwin::isSectionAtomizableBySymbols(
diff --git a/lib/MC/MCAsmInfoELF.cpp b/lib/MC/MCAsmInfoELF.cpp
index 26e5608d8733..e44c08b50d76 100644
--- a/lib/MC/MCAsmInfoELF.cpp
+++ b/lib/MC/MCAsmInfoELF.cpp
@@ -1,4 +1,4 @@
-//===-- MCAsmInfoELF.cpp - ELF asm properties -------------------*- C++ -*-===//
+//===- MCAsmInfoELF.cpp - ELF asm properties ------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -16,9 +16,10 @@
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/Support/ELF.h"
+
 using namespace llvm;
 
-void MCAsmInfoELF::anchor() { }
+void MCAsmInfoELF::anchor() {}
 
 MCSection *MCAsmInfoELF::getNonexecutableStackSection(MCContext &Ctx) const {
   if (!UsesNonexecutableStackSection)
@@ -31,5 +32,4 @@ MCAsmInfoELF::MCAsmInfoELF() {
   WeakRefDirective = "\t.weak\t";
   PrivateGlobalPrefix = ".L";
   PrivateLabelPrefix = ".L";
-  UsesNonexecutableStackSection = true;
 }
diff --git a/lib/MC/MCAsmInfoWasm.cpp b/lib/MC/MCAsmInfoWasm.cpp
new file mode 100644
index 000000000000..aa26616dda36
--- /dev/null
+++ b/lib/MC/MCAsmInfoWasm.cpp
@@ -0,0 +1,27 @@
+//===-- MCAsmInfoWasm.cpp - Wasm asm properties -----------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines target asm properties related what form asm statements
+// should take in general on Wasm-based targets
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCAsmInfoWasm.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSectionWasm.h"
+using namespace llvm;
+
+void MCAsmInfoWasm::anchor() { }
+
+MCAsmInfoWasm::MCAsmInfoWasm() {
+  HasIdentDirective = true;
+  WeakRefDirective = "\t.weak\t";
+  PrivateGlobalPrefix = ".L";
+  PrivateLabelPrefix = ".L";
+}
diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp
index 817009a65363..9e5553fa8d42 100644
--- a/lib/MC/MCAsmStreamer.cpp
+++ b/lib/MC/MCAsmStreamer.cpp
@@ -103,7 +103,10 @@ public:
   void AddComment(const Twine &T, bool EOL = true) override;
 
   /// AddEncodingComment - Add a comment showing the encoding of an instruction.
-  void AddEncodingComment(const MCInst &Inst, const MCSubtargetInfo &);
+  /// If PrintSchedInfo - is true then the comment sched:[x:y] should
+  //    be added to output if it's being supported by target
+  void AddEncodingComment(const MCInst &Inst, const MCSubtargetInfo &,
+                          bool PrintSchedInfo);
 
   /// GetCommentOS - Return a raw_ostream that comments can be written to.
   /// Unlike AddComment, you are required to terminate comments with \n if you
@@ -130,7 +133,7 @@ public:
   void ChangeSection(MCSection *Section, const MCExpr *Subsection) override;
 
   void EmitLOHDirective(MCLOHType Kind, const MCLOHArgs &Args) override;
-  void EmitLabel(MCSymbol *Symbol) override;
+  void EmitLabel(MCSymbol *Symbol, SMLoc Loc = SMLoc()) override;
 
   void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
   void EmitLinkerOptions(ArrayRef<std::string> Options) override;
@@ -278,7 +281,8 @@ public:
   void EmitWinEHHandler(const MCSymbol *Sym, bool Unwind, bool Except) override;
   void EmitWinEHHandlerData() override;
 
-  void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI) override;
+  void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
+                       bool PrintSchedInfo) override;
 
   void EmitBundleAlignMode(unsigned AlignPow2) override;
   void EmitBundleLock(bool AlignToEnd) override;
@@ -392,12 +396,13 @@ void MCAsmStreamer::emitExplicitComments() {
 void MCAsmStreamer::ChangeSection(MCSection *Section,
                                   const MCExpr *Subsection) {
   assert(Section && "Cannot switch to a null section!");
-  Section->PrintSwitchToSection(*MAI, OS, Subsection);
+  Section->PrintSwitchToSection(
+      *MAI, getContext().getObjectFileInfo()->getTargetTriple(), OS,
+      Subsection);
 }
 
-void MCAsmStreamer::EmitLabel(MCSymbol *Symbol) {
-  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
-  MCStreamer::EmitLabel(Symbol);
+void MCAsmStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
+  MCStreamer::EmitLabel(Symbol, Loc);
 
   Symbol->print(OS, MAI);
   OS << MAI->getLabelSuffix();
@@ -1503,7 +1508,8 @@ void MCAsmStreamer::EmitWinCFIEndProlog() {
 }
 
 void MCAsmStreamer::AddEncodingComment(const MCInst &Inst,
-                                       const MCSubtargetInfo &STI) {
+                                       const MCSubtargetInfo &STI,
+                                       bool PrintSchedInfo) {
   raw_ostream &OS = GetCommentOS();
   SmallString<256> Code;
   SmallVector<MCFixup, 4> Fixups;
@@ -1576,7 +1582,11 @@ void MCAsmStreamer::AddEncodingComment(const MCInst &Inst,
       }
     }
   }
-  OS << "]\n";
+  OS << "]";
+  // If we are not going to add fixup or schedul comments after this point then
+  // we have to end the current comment line with "\n".
+  if (Fixups.size() || !PrintSchedInfo)
+    OS << "\n";
 
   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
     MCFixup &F = Fixups[i];
@@ -1587,16 +1597,19 @@ void MCAsmStreamer::AddEncodingComment(const MCInst &Inst,
 }
 
 void MCAsmStreamer::EmitInstruction(const MCInst &Inst,
-                                    const MCSubtargetInfo &STI) {
+                                    const MCSubtargetInfo &STI,
+                                    bool PrintSchedInfo) {
   assert(getCurrentSectionOnly() &&
          "Cannot emit contents before setting section!");
 
   // Show the encoding in a comment if we have a code emitter.
   if (Emitter)
-    AddEncodingComment(Inst, STI);
+    AddEncodingComment(Inst, STI, PrintSchedInfo);
 
   // Show the MCInst if enabled.
   if (ShowInst) {
+    if (PrintSchedInfo)
+      GetCommentOS() << "\n";
     Inst.dump_pretty(GetCommentOS(), InstPrinter.get(), "\n ");
     GetCommentOS() << "\n";
   }
@@ -1606,6 +1619,16 @@ void MCAsmStreamer::EmitInstruction(const MCInst &Inst,
   else
     InstPrinter->printInst(&Inst, OS, "", STI);
 
+  if (PrintSchedInfo) {
+    std::string SI = STI.getSchedInfoStr(Inst);
+    if (!SI.empty())
+      GetCommentOS() << SI;
+  }
+
+  StringRef Comments = CommentToEmit;
+  if (Comments.size() && Comments.back() != '\n')
+    GetCommentOS() << "\n";
+
   EmitEOL();
 }
 
diff --git a/lib/MC/MCAssembler.cpp b/lib/MC/MCAssembler.cpp
index 83fcec92e2b5..c2bb7b277181 100644
--- a/lib/MC/MCAssembler.cpp
+++ b/lib/MC/MCAssembler.cpp
@@ -7,36 +7,49 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCAssembler.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAsmLayout.h"
+#include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCCodeView.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCFixupKindInfo.h"
+#include "llvm/MC/MCFragment.h"
+#include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCValue.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/LEB128.h"
-#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cstring>
+#include <cassert>
+#include <cstdint>
 #include <tuple>
+#include <utility>
+
 using namespace llvm;
 
 #define DEBUG_TYPE "assembler"
 
 namespace {
 namespace stats {
+
 STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
 STATISTIC(EmittedRelaxableFragments,
           "Number of emitted assembler fragments - relaxable");
@@ -55,8 +68,9 @@ STATISTIC(FragmentLayouts, "Number of fragment layouts");
 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
-}
-}
+
+} // end namespace stats
+} // end anonymous namespace
 
 // FIXME FIXME FIXME: There are number of places in this file where we convert
 // what is a 64-bit assembler value used for computation into a value in the
@@ -73,8 +87,7 @@ MCAssembler::MCAssembler(MCContext &Context, MCAsmBackend &Backend,
   VersionMinInfo.Major = 0; // Major version == 0 for "none specified"
 }
 
-MCAssembler::~MCAssembler() {
-}
+MCAssembler::~MCAssembler() = default;
 
 void MCAssembler::reset() {
   Sections.clear();
@@ -114,10 +127,16 @@ bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const {
   if (!Symbol->isVariable())
     return false;
 
-  // FIXME: It looks like gas supports some cases of the form "foo + 2". It
-  // is not clear if that is a bug or a feature.
   const MCExpr *Expr = Symbol->getVariableValue();
-  const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr);
+
+  MCValue V;
+  if (!Expr->evaluateAsRelocatable(V, nullptr, nullptr))
+    return false;
+
+  if (V.getSymB() || V.getRefKind() != MCSymbolRefExpr::VK_None)
+    return false;
+
+  const MCSymbolRefExpr *Ref = V.getSymA();
   if (!Ref)
     return false;
 
@@ -219,7 +238,6 @@ bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
       Value -= Layout.getSymbolOffset(Sym);
   }
 
-
   bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
                          MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
   assert((ShouldAlignPC ? IsPCRel : true) &&
@@ -641,7 +659,7 @@ std::pair<uint64_t, bool> MCAssembler::handleFixup(const MCAsmLayout &Layout,
 
 void MCAssembler::layout(MCAsmLayout &Layout) {
   DEBUG_WITH_TYPE("mc-dump", {
-      llvm::errs() << "assembler backend - pre-layout\n--\n";
+      errs() << "assembler backend - pre-layout\n--\n";
       dump(); });
 
   // Create dummy fragments and assign section ordinals.
@@ -671,14 +689,14 @@ void MCAssembler::layout(MCAsmLayout &Layout) {
       return;
 
   DEBUG_WITH_TYPE("mc-dump", {
-      llvm::errs() << "assembler backend - post-relaxation\n--\n";
+      errs() << "assembler backend - post-relaxation\n--\n";
       dump(); });
 
   // Finalize the layout, including fragment lowering.
   finishLayout(Layout);
 
   DEBUG_WITH_TYPE("mc-dump", {
-      llvm::errs() << "assembler backend - final-layout\n--\n";
+      errs() << "assembler backend - final-layout\n--\n";
       dump(); });
 
   // Allow the object writer a chance to perform post-layout binding (for
@@ -714,8 +732,8 @@ void MCAssembler::layout(MCAsmLayout &Layout) {
         uint64_t FixedValue;
         bool IsPCRel;
         std::tie(FixedValue, IsPCRel) = handleFixup(Layout, Frag, Fixup);
-        getBackend().applyFixup(Fixup, Contents.data(),
-                                Contents.size(), FixedValue, IsPCRel);
+        getBackend().applyFixup(Fixup, Contents.data(), Contents.size(),
+                                FixedValue, IsPCRel, getContext());
       }
     }
   }
@@ -741,6 +759,10 @@ bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
   MCValue Target;
   uint64_t Value;
   bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, Value);
+  if (Target.getSymA() &&
+      Target.getSymA()->getKind() == MCSymbolRefExpr::VK_X86_ABS8 &&
+      Fixup.getKind() == FK_Data_1)
+    return false;
   return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF,
                                                    Layout);
 }
diff --git a/lib/MC/MCCodeEmitter.cpp b/lib/MC/MCCodeEmitter.cpp
index c122763b2fe5..ca69478ed10d 100644
--- a/lib/MC/MCCodeEmitter.cpp
+++ b/lib/MC/MCCodeEmitter.cpp
@@ -1,4 +1,4 @@
-//===-- MCCodeEmitter.cpp - Instruction Encoding --------------------------===//
+//===- MCCodeEmitter.cpp - Instruction Encoding ---------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -11,8 +11,6 @@
 
 using namespace llvm;
 
-MCCodeEmitter::MCCodeEmitter() {
-}
+MCCodeEmitter::MCCodeEmitter() = default;
 
-MCCodeEmitter::~MCCodeEmitter() {
-}
+MCCodeEmitter::~MCCodeEmitter() = default;
diff --git a/lib/MC/MCContext.cpp b/lib/MC/MCContext.cpp
index 4798991ceed6..4628d0ab88f3 100644
--- a/lib/MC/MCContext.cpp
+++ b/lib/MC/MCContext.cpp
@@ -7,30 +7,43 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCContext.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAsmInfo.h"
-#include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCCodeView.h"
+#include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCDwarf.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCLabel.h"
 #include "llvm/MC/MCObjectFileInfo.h"
-#include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSectionCOFF.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCSectionMachO.h"
+#include "llvm/MC/MCSectionWasm.h"
 #include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCSymbolCOFF.h"
 #include "llvm/MC/MCSymbolELF.h"
 #include "llvm/MC/MCSymbolMachO.h"
+#include "llvm/MC/MCSymbolWasm.h"
+#include "llvm/MC/SectionKind.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/COFF.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ELF.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/SourceMgr.h"
+#include <cassert>
+#include <cstdlib>
+#include <tuple>
+#include <utility>
 
 using namespace llvm;
 
@@ -40,19 +53,14 @@ AsSecureLogFileName("as-secure-log-file-name",
                  "AS_SECURE_LOG_FILE env variable)"),
         cl::init(getenv("AS_SECURE_LOG_FILE")), cl::Hidden);
 
-
 MCContext::MCContext(const MCAsmInfo *mai, const MCRegisterInfo *mri,
                      const MCObjectFileInfo *mofi, const SourceMgr *mgr,
                      bool DoAutoReset)
-    : SrcMgr(mgr), MAI(mai), MRI(mri), MOFI(mofi), Allocator(),
+    : SrcMgr(mgr), InlineSrcMgr(nullptr), MAI(mai), MRI(mri), MOFI(mofi),
       Symbols(Allocator), UsedNames(Allocator),
-      CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0), DwarfLocSeen(false),
-      GenDwarfForAssembly(false), GenDwarfFileNumber(0), DwarfVersion(4),
-      AllowTemporaryLabels(true), DwarfCompileUnitID(0),
-      AutoReset(DoAutoReset), HadError(false) {
+      CurrentDwarfLoc(0, 0, 0, DWARF2_FLAG_IS_STMT, 0, 0),
+      AutoReset(DoAutoReset) {
   SecureLogFile = AsSecureLogFileName;
-  SecureLog = nullptr;
-  SecureLogUsed = false;
 
   if (SrcMgr && SrcMgr->getNumBuffers())
     MainFileName =
@@ -80,7 +88,6 @@ void MCContext::reset() {
   MCSubtargetAllocator.DestroyAll();
   UsedNames.clear();
   Symbols.clear();
-  SectionSymbols.clear();
   Allocator.Reset();
   Instances.clear();
   CompilationDir.clear();
@@ -124,18 +131,6 @@ MCSymbol *MCContext::getOrCreateSymbol(const Twine &Name) {
   return Sym;
 }
 
-MCSymbolELF *MCContext::getOrCreateSectionSymbol(const MCSectionELF &Section) {
-  MCSymbol *&Sym = SectionSymbols[&Section];
-  if (Sym)
-    return cast<MCSymbolELF>(Sym);
-
-  StringRef Name = Section.getSectionName();
-  auto NameIter = UsedNames.insert(std::make_pair(Name, false)).first;
-  Sym = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
-
-  return cast<MCSymbolELF>(Sym);
-}
-
 MCSymbol *MCContext::getOrCreateFrameAllocSymbol(StringRef FuncName,
                                                  unsigned Idx) {
   return getOrCreateSymbol(Twine(MAI->getPrivateGlobalPrefix()) + FuncName +
@@ -162,6 +157,8 @@ MCSymbol *MCContext::createSymbolImpl(const StringMapEntry<bool> *Name,
       return new (Name, *this) MCSymbolELF(Name, IsTemporary);
     case MCObjectFileInfo::IsMachO:
       return new (Name, *this) MCSymbolMachO(Name, IsTemporary);
+    case MCObjectFileInfo::IsWasm:
+      return new (Name, *this) MCSymbolWasm(Name, IsTemporary);
     }
   }
   return new (Name, *this) MCSymbol(MCSymbol::SymbolKindUnset, Name,
@@ -182,7 +179,7 @@ MCSymbol *MCContext::createSymbol(StringRef Name, bool AlwaysAddSuffix,
   SmallString<128> NewName = Name;
   bool AddSuffix = AlwaysAddSuffix;
   unsigned &NextUniqueID = NextID[Name];
-  for (;;) {
+  while (true) {
     if (AddSuffix) {
       NewName.resize(Name.size());
       raw_svector_ostream(NewName) << NextUniqueID++;
@@ -275,7 +272,6 @@ MCSectionMachO *MCContext::getMachOSection(StringRef Segment, StringRef Section,
                                            unsigned TypeAndAttributes,
                                            unsigned Reserved2, SectionKind Kind,
                                            const char *BeginSymName) {
-
   // We unique sections by their segment/section pair.  The returned section
   // may not have the same flags as the requested section, if so this should be
   // diagnosed by the client as an error.
@@ -316,18 +312,53 @@ void MCContext::renameELFSection(MCSectionELF *Section, StringRef Name) {
   const_cast<MCSectionELF *>(Section)->setSectionName(CachedName);
 }
 
+MCSectionELF *MCContext::createELFSectionImpl(StringRef Section, unsigned Type,
+                                              unsigned Flags, SectionKind K,
+                                              unsigned EntrySize,
+                                              const MCSymbolELF *Group,
+                                              unsigned UniqueID,
+                                              const MCSymbolELF *Associated) {
+  MCSymbolELF *R;
+  MCSymbol *&Sym = Symbols[Section];
+  // A section symbol can not redefine regular symbols. There may be multiple
+  // sections with the same name, in which case the first such section wins.
+  if (Sym && Sym->isDefined() &&
+      (!Sym->isInSection() || Sym->getSection().getBeginSymbol() != Sym))
+    reportError(SMLoc(), "invalid symbol redefinition");
+  if (Sym && Sym->isUndefined()) {
+    R = cast<MCSymbolELF>(Sym);
+  } else {
+    auto NameIter = UsedNames.insert(std::make_pair(Section, false)).first;
+    R = new (&*NameIter, *this) MCSymbolELF(&*NameIter, /*isTemporary*/ false);
+    if (!Sym)
+      Sym = R;
+  }
+  R->setBinding(ELF::STB_LOCAL);
+  R->setType(ELF::STT_SECTION);
+
+  auto *Ret = new (ELFAllocator.Allocate()) MCSectionELF(
+      Section, Type, Flags, K, EntrySize, Group, UniqueID, R, Associated);
+
+  auto *F = new MCDataFragment();
+  Ret->getFragmentList().insert(Ret->begin(), F);
+  F->setParent(Ret);
+  R->setFragment(F);
+
+  return Ret;
+}
+
 MCSectionELF *MCContext::createELFRelSection(const Twine &Name, unsigned Type,
                                              unsigned Flags, unsigned EntrySize,
                                              const MCSymbolELF *Group,
-                                             const MCSectionELF *Associated) {
+                                             const MCSectionELF *RelInfoSection) {
   StringMap<bool>::iterator I;
   bool Inserted;
   std::tie(I, Inserted) =
-      ELFRelSecNames.insert(std::make_pair(Name.str(), true));
+      RelSecNames.insert(std::make_pair(Name.str(), true));
 
-  return new (ELFAllocator.Allocate())
-      MCSectionELF(I->getKey(), Type, Flags, SectionKind::getReadOnly(),
-                   EntrySize, Group, true, nullptr, Associated);
+  return createELFSectionImpl(
+      I->getKey(), Type, Flags, SectionKind::getReadOnly(), EntrySize, Group,
+      true, cast<MCSymbolELF>(RelInfoSection->getBeginSymbol()));
 }
 
 MCSectionELF *MCContext::getELFNamedSection(const Twine &Prefix,
@@ -340,21 +371,20 @@ MCSectionELF *MCContext::getELFNamedSection(const Twine &Prefix,
 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
                                        unsigned Flags, unsigned EntrySize,
                                        const Twine &Group, unsigned UniqueID,
-                                       const char *BeginSymName) {
+                                       const MCSymbolELF *Associated) {
   MCSymbolELF *GroupSym = nullptr;
   if (!Group.isTriviallyEmpty() && !Group.str().empty())
     GroupSym = cast<MCSymbolELF>(getOrCreateSymbol(Group));
 
   return getELFSection(Section, Type, Flags, EntrySize, GroupSym, UniqueID,
-                       BeginSymName, nullptr);
+                       Associated);
 }
 
 MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
                                        unsigned Flags, unsigned EntrySize,
                                        const MCSymbolELF *GroupSym,
                                        unsigned UniqueID,
-                                       const char *BeginSymName,
-                                       const MCSectionELF *Associated) {
+                                       const MCSymbolELF *Associated) {
   StringRef Group = "";
   if (GroupSym)
     Group = GroupSym->getName();
@@ -375,22 +405,16 @@ MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
   else
     Kind = SectionKind::getReadOnly();
 
-  MCSymbol *Begin = nullptr;
-  if (BeginSymName)
-    Begin = createTempSymbol(BeginSymName, false);
-
-  MCSectionELF *Result = new (ELFAllocator.Allocate())
-      MCSectionELF(CachedName, Type, Flags, Kind, EntrySize, GroupSym, UniqueID,
-                   Begin, Associated);
+  MCSectionELF *Result = createELFSectionImpl(
+      CachedName, Type, Flags, Kind, EntrySize, GroupSym, UniqueID, Associated);
   Entry.second = Result;
   return Result;
 }
 
 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {
-  MCSectionELF *Result = new (ELFAllocator.Allocate())
-      MCSectionELF(".group", ELF::SHT_GROUP, 0, SectionKind::getReadOnly(), 4,
-                   Group, ~0, nullptr, nullptr);
-  return Result;
+  return createELFSectionImpl(".group", ELF::SHT_GROUP, 0,
+                              SectionKind::getReadOnly(), 4, Group, ~0,
+                              nullptr);
 }
 
 MCSectionCOFF *MCContext::getCOFFSection(StringRef Section,
@@ -462,6 +486,80 @@ MCSectionCOFF *MCContext::getAssociativeCOFFSection(MCSectionCOFF *Sec,
                         "", 0, UniqueID);
 }
 
+void MCContext::renameWasmSection(MCSectionWasm *Section, StringRef Name) {
+  StringRef GroupName;
+  assert(!Section->getGroup() && "not yet implemented");
+
+  unsigned UniqueID = Section->getUniqueID();
+  WasmUniquingMap.erase(
+      WasmSectionKey{Section->getSectionName(), GroupName, UniqueID});
+  auto I = WasmUniquingMap.insert(std::make_pair(
+                                     WasmSectionKey{Name, GroupName, UniqueID},
+                                     Section))
+               .first;
+  StringRef CachedName = I->first.SectionName;
+  const_cast<MCSectionWasm *>(Section)->setSectionName(CachedName);
+}
+
+MCSectionWasm *MCContext::createWasmRelSection(const Twine &Name, unsigned Type,
+                                               unsigned Flags,
+                                               const MCSymbolWasm *Group) {
+  StringMap<bool>::iterator I;
+  bool Inserted;
+  std::tie(I, Inserted) =
+      RelSecNames.insert(std::make_pair(Name.str(), true));
+
+  return new (WasmAllocator.Allocate())
+      MCSectionWasm(I->getKey(), Type, Flags, SectionKind::getReadOnly(),
+                    Group, ~0, nullptr);
+}
+
+MCSectionWasm *MCContext::getWasmNamedSection(const Twine &Prefix,
+                                              const Twine &Suffix, unsigned Type,
+                                              unsigned Flags) {
+  return getWasmSection(Prefix + "." + Suffix, Type, Flags, Suffix);
+}
+
+MCSectionWasm *MCContext::getWasmSection(const Twine &Section, unsigned Type,
+                                         unsigned Flags,
+                                         const Twine &Group, unsigned UniqueID,
+                                         const char *BeginSymName) {
+  MCSymbolWasm *GroupSym = nullptr;
+  if (!Group.isTriviallyEmpty() && !Group.str().empty())
+    GroupSym = cast<MCSymbolWasm>(getOrCreateSymbol(Group));
+
+  return getWasmSection(Section, Type, Flags, GroupSym, UniqueID, BeginSymName);
+}
+
+MCSectionWasm *MCContext::getWasmSection(const Twine &Section, unsigned Type,
+                                         unsigned Flags,
+                                         const MCSymbolWasm *GroupSym,
+                                         unsigned UniqueID,
+                                         const char *BeginSymName) {
+  StringRef Group = "";
+  if (GroupSym)
+    Group = GroupSym->getName();
+  // Do the lookup, if we have a hit, return it.
+  auto IterBool = WasmUniquingMap.insert(
+      std::make_pair(WasmSectionKey{Section.str(), Group, UniqueID}, nullptr));
+  auto &Entry = *IterBool.first;
+  if (!IterBool.second)
+    return Entry.second;
+
+  StringRef CachedName = Entry.first.SectionName;
+
+  SectionKind Kind = SectionKind::getText();
+
+  MCSymbol *Begin = nullptr;
+  if (BeginSymName)
+    Begin = createTempSymbol(BeginSymName, false);
+
+  MCSectionWasm *Result = new (WasmAllocator.Allocate())
+      MCSectionWasm(CachedName, Type, Flags, Kind, GroupSym, UniqueID, Begin);
+  Entry.second = Result;
+  return Result;
+}
+
 MCSubtargetInfo &MCContext::getSubtargetCopy(const MCSubtargetInfo &STI) {
   return *new (MCSubtargetAllocator.Allocate()) MCSubtargetInfo(STI);
 }
@@ -510,13 +608,15 @@ CodeViewContext &MCContext::getCVContext() {
 void MCContext::reportError(SMLoc Loc, const Twine &Msg) {
   HadError = true;
 
-  // If we have a source manager use it. Otherwise just use the generic
-  // report_fatal_error().
-  if (!SrcMgr)
+  // If we have a source manager use it. Otherwise, try using the inline source
+  // manager.
+  // If that fails, use the generic report_fatal_error().
+  if (SrcMgr)
+    SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
+  else if (InlineSrcMgr)
+    InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
+  else
     report_fatal_error(Msg, false);
-
-  // Use the source manager to print the message.
-  SrcMgr->PrintMessage(Loc, SourceMgr::DK_Error, Msg);
 }
 
 void MCContext::reportFatalError(SMLoc Loc, const Twine &Msg) {
diff --git a/lib/MC/MCDisassembler/MCDisassembler.cpp b/lib/MC/MCDisassembler/MCDisassembler.cpp
index 3a4f7382bd3c..2f1275d00b86 100644
--- a/lib/MC/MCDisassembler/MCDisassembler.cpp
+++ b/lib/MC/MCDisassembler/MCDisassembler.cpp
@@ -1,4 +1,4 @@
-//===-- MCDisassembler.cpp - Disassembler interface -----------------------===//
+//===- MCDisassembler.cpp - Disassembler interface ------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -8,13 +8,12 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCDisassembler/MCDisassembler.h"
-#include "llvm/MC/MCDisassembler/MCExternalSymbolizer.h"
 #include "llvm/Support/raw_ostream.h"
+#include <algorithm>
 
 using namespace llvm;
 
-MCDisassembler::~MCDisassembler() {
-}
+MCDisassembler::~MCDisassembler() = default;
 
 bool MCDisassembler::tryAddingSymbolicOperand(MCInst &Inst, int64_t Value,
                                               uint64_t Address, bool IsBranch,
diff --git a/lib/MC/MCDisassembler/MCRelocationInfo.cpp b/lib/MC/MCDisassembler/MCRelocationInfo.cpp
index 1612562497d9..5805fd7007d2 100644
--- a/lib/MC/MCDisassembler/MCRelocationInfo.cpp
+++ b/lib/MC/MCDisassembler/MCRelocationInfo.cpp
@@ -1,4 +1,4 @@
-//==-- MCRelocationInfo.cpp ------------------------------------------------==//
+//===-- MCRelocationInfo.cpp ----------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -8,17 +8,14 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCDisassembler/MCRelocationInfo.h"
-#include "llvm-c/Disassembler.h"
 #include "llvm/Support/TargetRegistry.h"
+#include "llvm-c/Disassembler.h"
 
 using namespace llvm;
 
-MCRelocationInfo::MCRelocationInfo(MCContext &Ctx)
-  : Ctx(Ctx) {
-}
+MCRelocationInfo::MCRelocationInfo(MCContext &Ctx) : Ctx(Ctx) {}
 
-MCRelocationInfo::~MCRelocationInfo() {
-}
+MCRelocationInfo::~MCRelocationInfo() = default;
 
 const MCExpr *
 MCRelocationInfo::createExprForCAPIVariantKind(const MCExpr *SubExpr,
diff --git a/lib/MC/MCDisassembler/MCSymbolizer.cpp b/lib/MC/MCDisassembler/MCSymbolizer.cpp
index c0f707d356c1..78e611e3ddda 100644
--- a/lib/MC/MCDisassembler/MCSymbolizer.cpp
+++ b/lib/MC/MCDisassembler/MCSymbolizer.cpp
@@ -1,4 +1,4 @@
-//===-- llvm/MC/MCSymbolizer.cpp - MCSymbolizer class -----------*- C++ -*-===//
+//===-- llvm/MC/MCSymbolizer.cpp - MCSymbolizer class ---------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -11,5 +11,4 @@
 
 using namespace llvm;
 
-MCSymbolizer::~MCSymbolizer() {
-}
+MCSymbolizer::~MCSymbolizer() = default;
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index a7551a3283a3..cc32e90ad36e 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -7,27 +7,41 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCDwarf.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Hashing.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/None.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Config/config.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCObjectStreamer.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
-#include "llvm/Support/Debug.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/Endian.h"
 #include "llvm/Support/EndianStream.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/LEB128.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstdint>
+#include <string>
+#include <utility>
+#include <vector>
 
 using namespace llvm;
 
@@ -592,7 +606,6 @@ static void EmitGenDwarfAranges(MCStreamer *MCOS,
   // And the pair of terminating zeros.
   Length += 2 * AddrSize;
 
-
   // Emit the header for this section.
   // The 4 byte length not including the 4 byte value for the length.
   MCOS->EmitIntValue(Length - 4, 4);
@@ -661,7 +674,14 @@ static void EmitGenDwarfInfo(MCStreamer *MCOS,
   // The 2 byte DWARF version.
   MCOS->EmitIntValue(context.getDwarfVersion(), 2);
 
+  // The DWARF v5 header has unit type, address size, abbrev offset.
+  // Earlier versions have abbrev offset, address size.
   const MCAsmInfo &AsmInfo = *context.getAsmInfo();
+  int AddrSize = AsmInfo.getPointerSize();
+  if (context.getDwarfVersion() >= 5) {
+    MCOS->EmitIntValue(dwarf::DW_UT_compile, 1);
+    MCOS->EmitIntValue(AddrSize, 1);
+  }
   // The 4 byte offset to the debug abbrevs from the start of the .debug_abbrev,
   // it is at the start of that section so this is zero.
   if (AbbrevSectionSymbol == nullptr)
@@ -669,11 +689,8 @@ static void EmitGenDwarfInfo(MCStreamer *MCOS,
   else
     MCOS->EmitSymbolValue(AbbrevSectionSymbol, 4,
                           AsmInfo.needsDwarfSectionOffsetDirective());
-
-  const MCAsmInfo *asmInfo = context.getAsmInfo();
-  int AddrSize = asmInfo->getPointerSize();
-  // The 1 byte size of an address.
-  MCOS->EmitIntValue(AddrSize, 1);
+  if (context.getDwarfVersion() <= 4)
+    MCOS->EmitIntValue(AddrSize, 1);
 
   // Second part: the compile_unit DIE.
 
@@ -885,7 +902,7 @@ void MCGenDwarfInfo::Emit(MCStreamer *MCOS) {
     }
   }
 
-  assert((RangesSectionSymbol != NULL) || !UseRangesSection);
+  assert((RangesSectionSymbol != nullptr) || !UseRangesSection);
 
   MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
 
@@ -1003,6 +1020,7 @@ static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
 }
 
 namespace {
+
 class FrameEmitterImpl {
   int CFAOffset = 0;
   int InitialCFAOffset = 0;
@@ -1050,10 +1068,10 @@ void FrameEmitterImpl::EmitCFIInstruction(const MCCFIInstruction &Instr) {
     Streamer.EmitULEB128IntValue(Reg2);
     return;
   }
-  case MCCFIInstruction::OpWindowSave: {
+  case MCCFIInstruction::OpWindowSave:
     Streamer.EmitIntValue(dwarf::DW_CFA_GNU_window_save, 1);
     return;
-  }
+
   case MCCFIInstruction::OpUndefined: {
     unsigned Reg = Instr.getRegister();
     Streamer.EmitIntValue(dwarf::DW_CFA_undefined, 1);
@@ -1087,7 +1105,6 @@ void FrameEmitterImpl::EmitCFIInstruction(const MCCFIInstruction &Instr) {
 
     return;
   }
-
   case MCCFIInstruction::OpDefCfaRegister: {
     unsigned Reg = Instr.getRegister();
     if (!IsEH)
@@ -1097,7 +1114,6 @@ void FrameEmitterImpl::EmitCFIInstruction(const MCCFIInstruction &Instr) {
 
     return;
   }
-
   case MCCFIInstruction::OpOffset:
   case MCCFIInstruction::OpRelOffset: {
     const bool IsRelative =
@@ -1145,11 +1161,11 @@ void FrameEmitterImpl::EmitCFIInstruction(const MCCFIInstruction &Instr) {
     Streamer.EmitIntValue(dwarf::DW_CFA_restore | Reg, 1);
     return;
   }
-  case MCCFIInstruction::OpGnuArgsSize: {
+  case MCCFIInstruction::OpGnuArgsSize:
     Streamer.EmitIntValue(dwarf::DW_CFA_GNU_args_size, 1);
     Streamer.EmitULEB128IntValue(Instr.getOffset());
     return;
-  }
+
   case MCCFIInstruction::OpEscape:
     Streamer.EmitBytes(Instr.getValues());
     return;
@@ -1444,10 +1460,12 @@ void FrameEmitterImpl::EmitFDE(const MCSymbol &cieStart,
 }
 
 namespace {
+
 struct CIEKey {
   static const CIEKey getEmptyKey() {
     return CIEKey(nullptr, 0, -1, false, false);
   }
+
   static const CIEKey getTombstoneKey() {
     return CIEKey(nullptr, -1, 0, false, false);
   }
@@ -1457,23 +1475,28 @@ struct CIEKey {
       : Personality(Personality), PersonalityEncoding(PersonalityEncoding),
         LsdaEncoding(LsdaEncoding), IsSignalFrame(IsSignalFrame),
         IsSimple(IsSimple) {}
+
   const MCSymbol *Personality;
   unsigned PersonalityEncoding;
   unsigned LsdaEncoding;
   bool IsSignalFrame;
   bool IsSimple;
 };
-} // anonymous namespace
+
+} // end anonymous namespace
 
 namespace llvm {
+
 template <> struct DenseMapInfo<CIEKey> {
   static CIEKey getEmptyKey() { return CIEKey::getEmptyKey(); }
   static CIEKey getTombstoneKey() { return CIEKey::getTombstoneKey(); }
+
   static unsigned getHashValue(const CIEKey &Key) {
     return static_cast<unsigned>(
         hash_combine(Key.Personality, Key.PersonalityEncoding, Key.LsdaEncoding,
                      Key.IsSignalFrame, Key.IsSimple));
   }
+
   static bool isEqual(const CIEKey &LHS, const CIEKey &RHS) {
     return LHS.Personality == RHS.Personality &&
            LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
@@ -1482,7 +1505,8 @@ template <> struct DenseMapInfo<CIEKey> {
            LHS.IsSimple == RHS.IsSimple;
   }
 };
-} // namespace llvm
+
+} // end namespace llvm
 
 void MCDwarfFrameEmitter::Emit(MCObjectStreamer &Streamer, MCAsmBackend *MAB,
                                bool IsEH) {
diff --git a/lib/MC/MCELFObjectTargetWriter.cpp b/lib/MC/MCELFObjectTargetWriter.cpp
index de645cac7370..68fb5e7cbb3d 100644
--- a/lib/MC/MCELFObjectTargetWriter.cpp
+++ b/lib/MC/MCELFObjectTargetWriter.cpp
@@ -7,10 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/ADT/STLExtras.h"
 #include "llvm/MC/MCELFObjectWriter.h"
-#include "llvm/MC/MCExpr.h"
-#include "llvm/MC/MCValue.h"
 
 using namespace llvm;
 
diff --git a/lib/MC/MCELFStreamer.cpp b/lib/MC/MCELFStreamer.cpp
index 0ef1b2a8bdca..c8e0223c0573 100644
--- a/lib/MC/MCELFStreamer.cpp
+++ b/lib/MC/MCELFStreamer.cpp
@@ -11,30 +11,31 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCELFStreamer.h"
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/MC/MCAsmBackend.h"
-#include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCELFStreamer.h"
 #include "llvm/MC/MCExpr.h"
-#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCObjectFileInfo.h"
-#include "llvm/MC/MCObjectStreamer.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbolELF.h"
 #include "llvm/MC/MCSymbol.h"
-#include "llvm/MC/MCValue.h"
-#include "llvm/Support/Debug.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/ELF.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstdint>
 
 using namespace llvm;
 
@@ -42,9 +43,6 @@ bool MCELFStreamer::isBundleLocked() const {
   return getCurrentSectionOnly()->isBundleLocked();
 }
 
-MCELFStreamer::~MCELFStreamer() {
-}
-
 void MCELFStreamer::mergeFragment(MCDataFragment *DF,
                                   MCDataFragment *EF) {
   MCAssembler &Assembler = getAssembler();
@@ -95,11 +93,19 @@ void MCELFStreamer::InitSections(bool NoExecStack) {
     SwitchSection(Ctx.getAsmInfo()->getNonexecutableStackSection(Ctx));
 }
 
-void MCELFStreamer::EmitLabel(MCSymbol *S) {
+void MCELFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) {
   auto *Symbol = cast<MCSymbolELF>(S);
-  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
+  MCObjectStreamer::EmitLabel(Symbol, Loc);
+
+  const MCSectionELF &Section =
+      static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
+  if (Section.getFlags() & ELF::SHF_TLS)
+    Symbol->setType(ELF::STT_TLS);
+}
 
-  MCObjectStreamer::EmitLabel(Symbol);
+void MCELFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc, MCFragment *F) {
+  auto *Symbol = cast<MCSymbolELF>(S);
+  MCObjectStreamer::EmitLabel(Symbol, Loc, F);
 
   const MCSectionELF &Section =
       static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
@@ -147,17 +153,8 @@ void MCELFStreamer::ChangeSection(MCSection *Section,
   if (Grp)
     Asm.registerSymbol(*Grp);
 
-  this->MCObjectStreamer::ChangeSection(Section, Subsection);
-  MCContext &Ctx = getContext();
-  auto *Begin = cast_or_null<MCSymbolELF>(Section->getBeginSymbol());
-  if (!Begin) {
-    Begin = Ctx.getOrCreateSectionSymbol(*SectionELF);
-    Section->setBeginSymbol(Begin);
-  }
-  if (Begin->isUndefined()) {
-    Asm.registerSymbol(*Begin);
-    Begin->setType(ELF::STT_SECTION);
-  }
+  changeSectionImpl(Section, Subsection);
+  Asm.registerSymbol(*Section->getBeginSymbol());
 }
 
 void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
@@ -361,13 +358,6 @@ void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
                                          ValueSize, MaxBytesToEmit);
 }
 
-// Add a symbol for the file name of this module. They start after the
-// null symbol and don't count as normal symbol, i.e. a non-STT_FILE symbol
-// with the same name may appear.
-void MCELFStreamer::EmitFileDirective(StringRef Filename) {
-  getAssembler().addFileName(Filename);
-}
-
 void MCELFStreamer::EmitIdent(StringRef IdentString) {
   MCSection *Comment = getAssembler().getContext().getELFSection(
       ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
@@ -630,15 +620,6 @@ void MCELFStreamer::FinishImpl() {
   this->MCObjectStreamer::FinishImpl();
 }
 
-MCStreamer *llvm::createELFStreamer(MCContext &Context, MCAsmBackend &MAB,
-                                    raw_pwrite_stream &OS, MCCodeEmitter *CE,
-                                    bool RelaxAll) {
-  MCELFStreamer *S = new MCELFStreamer(Context, MAB, OS, CE);
-  if (RelaxAll)
-    S->getAssembler().setRelaxAll(true);
-  return S;
-}
-
 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
   llvm_unreachable("Generic ELF doesn't support this directive");
 }
@@ -647,22 +628,6 @@ void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
   llvm_unreachable("ELF doesn't support this directive");
 }
 
-void MCELFStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
-  llvm_unreachable("ELF doesn't support this directive");
-}
-
-void MCELFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
-  llvm_unreachable("ELF doesn't support this directive");
-}
-
-void MCELFStreamer::EmitCOFFSymbolType(int Type) {
-  llvm_unreachable("ELF doesn't support this directive");
-}
-
-void MCELFStreamer::EndCOFFSymbolDef() {
-  llvm_unreachable("ELF doesn't support this directive");
-}
-
 void MCELFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
                                  uint64_t Size, unsigned ByteAlignment) {
   llvm_unreachable("ELF doesn't support this directive");
@@ -672,3 +637,12 @@ void MCELFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
                                    uint64_t Size, unsigned ByteAlignment) {
   llvm_unreachable("ELF doesn't support this directive");
 }
+
+MCStreamer *llvm::createELFStreamer(MCContext &Context, MCAsmBackend &MAB,
+                                    raw_pwrite_stream &OS, MCCodeEmitter *CE,
+                                    bool RelaxAll) {
+  MCELFStreamer *S = new MCELFStreamer(Context, MAB, OS, CE);
+  if (RelaxAll)
+    S->getAssembler().setRelaxAll(true);
+  return S;
+}
diff --git a/lib/MC/MCExpr.cpp b/lib/MC/MCExpr.cpp
index bcc43a54d620..8149aa27327c 100644
--- a/lib/MC/MCExpr.cpp
+++ b/lib/MC/MCExpr.cpp
@@ -7,28 +7,35 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCExpr.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCValue.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstdint>
+
 using namespace llvm;
 
 #define DEBUG_TYPE "mcexpr"
 
 namespace {
 namespace stats {
+
 STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations");
-}
-}
+
+} // end namespace stats
+} // end anonymous namespace
 
 void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI, bool InParens) const {
   switch (getKind()) {
@@ -44,7 +51,7 @@ void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI, bool InParens) const {
     // Parenthesize names that start with $ so that they don't look like
     // absolute names.
     bool UseParens =
-        !InParens && Sym.getName().size() && Sym.getName()[0] == '$';
+        !InParens && !Sym.getName().empty() && Sym.getName()[0] == '$';
     if (UseParens) {
       OS << '(';
       Sym.print(OS, MAI);
@@ -129,21 +136,24 @@ void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI, bool InParens) const {
   llvm_unreachable("Invalid expression kind!");
 }
 
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MCExpr::dump() const {
   dbgs() << *this;
   dbgs() << '\n';
 }
+#endif
 
 /* *** */
 
 const MCBinaryExpr *MCBinaryExpr::create(Opcode Opc, const MCExpr *LHS,
-                                         const MCExpr *RHS, MCContext &Ctx) {
-  return new (Ctx) MCBinaryExpr(Opc, LHS, RHS);
+                                         const MCExpr *RHS, MCContext &Ctx,
+                                         SMLoc Loc) {
+  return new (Ctx) MCBinaryExpr(Opc, LHS, RHS, Loc);
 }
 
 const MCUnaryExpr *MCUnaryExpr::create(Opcode Opc, const MCExpr *Expr,
-                                       MCContext &Ctx) {
-  return new (Ctx) MCUnaryExpr(Opc, Expr);
+                                       MCContext &Ctx, SMLoc Loc) {
+  return new (Ctx) MCUnaryExpr(Opc, Expr, Loc);
 }
 
 const MCConstantExpr *MCConstantExpr::create(int64_t Value, MCContext &Ctx) {
@@ -153,8 +163,8 @@ const MCConstantExpr *MCConstantExpr::create(int64_t Value, MCContext &Ctx) {
 /* *** */
 
 MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind,
-                                 const MCAsmInfo *MAI)
-    : MCExpr(MCExpr::SymbolRef), Kind(Kind),
+                                 const MCAsmInfo *MAI, SMLoc Loc)
+    : MCExpr(MCExpr::SymbolRef, Loc), Kind(Kind),
       UseParensForSymbolVariant(MAI->useParensForSymbolVariant()),
       HasSubsectionsViaSymbols(MAI->hasSubsectionsViaSymbols()),
       Symbol(Symbol) {
@@ -163,8 +173,8 @@ MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind,
 
 const MCSymbolRefExpr *MCSymbolRefExpr::create(const MCSymbol *Sym,
                                                VariantKind Kind,
-                                               MCContext &Ctx) {
-  return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo());
+                                               MCContext &Ctx, SMLoc Loc) {
+  return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo(), Loc);
 }
 
 const MCSymbolRefExpr *MCSymbolRefExpr::create(StringRef Name, VariantKind Kind,
@@ -205,6 +215,7 @@ StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
   case VK_SECREL: return "SECREL32";
   case VK_SIZE: return "SIZE";
   case VK_WEAKREF: return "WEAKREF";
+  case VK_X86_ABS8: return "ABS8";
   case VK_ARM_NONE: return "none";
   case VK_ARM_GOT_PREL: return "GOT_PREL";
   case VK_ARM_TARGET1: return "target1";
@@ -275,6 +286,7 @@ StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
   case VK_Hexagon_IE: return "IE";
   case VK_Hexagon_IE_GOT: return "IEGOT";
   case VK_WebAssembly_FUNCTION: return "FUNCTION";
+  case VK_WebAssembly_TYPEINDEX: return "TYPEINDEX";
   case VK_AMDGPU_GOTPCREL32_LO: return "gotpcrel32@lo";
   case VK_AMDGPU_GOTPCREL32_HI: return "gotpcrel32@hi";
   case VK_AMDGPU_REL32_LO: return "rel32@lo";
@@ -314,6 +326,7 @@ MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
     .Case("imgrel", VK_COFF_IMGREL32)
     .Case("secrel32", VK_SECREL)
     .Case("size", VK_SIZE)
+    .Case("abs8", VK_X86_ABS8)
     .Case("l", VK_PPC_LO)
     .Case("h", VK_PPC_HI)
     .Case("ha", VK_PPC_HA)
diff --git a/lib/MC/MCFragment.cpp b/lib/MC/MCFragment.cpp
index 8ff8f8aba1c1..90b44177cf5e 100644
--- a/lib/MC/MCFragment.cpp
+++ b/lib/MC/MCFragment.cpp
@@ -7,30 +7,29 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCFragment.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAssembler.h"
-#include "llvm/MC/MCAsmBackend.h"
-#include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCContext.h"
-#include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCExpr.h"
-#include "llvm/MC/MCFixupKindInfo.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCSection.h"
-#include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCValue.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/LEB128.h"
-#include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstdint>
+#include <utility>
+
 using namespace llvm;
 
-MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
-  : Assembler(Asm), LastValidFragment()
- {
+MCAsmLayout::MCAsmLayout(MCAssembler &Asm) : Assembler(Asm) {
   // Compute the section layout order. Virtual sections must go last.
   for (MCSection &Sec : Asm)
     if (!Sec.isVirtualSection())
@@ -145,14 +144,14 @@ const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
   MCValue Value;
   if (!Expr->evaluateAsValue(Value, *this)) {
     Assembler.getContext().reportError(
-        SMLoc(), "expression could not be evaluated");
+        Expr->getLoc(), "expression could not be evaluated");
     return nullptr;
   }
 
   const MCSymbolRefExpr *RefB = Value.getSymB();
   if (RefB) {
     Assembler.getContext().reportError(
-        SMLoc(), Twine("symbol '") + RefB->getSymbol().getName() +
+        Expr->getLoc(), Twine("symbol '") + RefB->getSymbol().getName() +
                      "' could not be evaluated in a subtraction expression");
     return nullptr;
   }
@@ -164,8 +163,7 @@ const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
   const MCSymbol &ASym = A->getSymbol();
   const MCAssembler &Asm = getAssembler();
   if (ASym.isCommon()) {
-    // FIXME: we should probably add a SMLoc to MCExpr.
-    Asm.getContext().reportError(SMLoc(),
+    Asm.getContext().reportError(Expr->getLoc(),
                                  "Common symbol '" + ASym.getName() +
                                      "' cannot be used in assignment expr");
     return nullptr;
@@ -234,7 +232,7 @@ uint64_t llvm::computeBundlePadding(const MCAssembler &Assembler,
 
 void ilist_alloc_traits<MCFragment>::deleteNode(MCFragment *V) { V->destroy(); }
 
-MCFragment::~MCFragment() { }
+MCFragment::~MCFragment() = default;
 
 MCFragment::MCFragment(FragmentType Kind, bool HasInstructions,
                        uint8_t BundlePadding, MCSection *Parent)
@@ -295,8 +293,6 @@ void MCFragment::destroy() {
   }
 }
 
-/* *** */
-
 // Debugging methods
 
 namespace llvm {
@@ -308,10 +304,11 @@ raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
   return OS;
 }
 
-}
+} // end namespace llvm
 
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MCFragment::dump() {
-  raw_ostream &OS = llvm::errs();
+  raw_ostream &OS = errs();
 
   OS << "<";
   switch (getKind()) {
@@ -449,7 +446,7 @@ LLVM_DUMP_METHOD void MCFragment::dump() {
 }
 
 LLVM_DUMP_METHOD void MCAssembler::dump() {
-  raw_ostream &OS = llvm::errs();
+  raw_ostream &OS = errs();
 
   OS << "<MCAssembler\n";
   OS << "  Sections:[\n    ";
@@ -469,3 +466,4 @@ LLVM_DUMP_METHOD void MCAssembler::dump() {
   }
   OS << "]>\n";
 }
+#endif
diff --git a/lib/MC/MCInst.cpp b/lib/MC/MCInst.cpp
index 2da8ecc4ff6a..f6d1d3cffca0 100644
--- a/lib/MC/MCInst.cpp
+++ b/lib/MC/MCInst.cpp
@@ -10,6 +10,7 @@
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInstPrinter.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 
@@ -34,10 +35,12 @@ void MCOperand::print(raw_ostream &OS) const {
   OS << ">";
 }
 
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MCOperand::dump() const {
   print(dbgs());
   dbgs() << "\n";
 }
+#endif
 
 void MCInst::print(raw_ostream &OS) const {
   OS << "<MCInst " << getOpcode();
@@ -63,7 +66,9 @@ void MCInst::dump_pretty(raw_ostream &OS, const MCInstPrinter *Printer,
   OS << ">";
 }
 
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MCInst::dump() const {
   print(dbgs());
   dbgs() << "\n";
 }
+#endif
diff --git a/lib/MC/MCInstPrinter.cpp b/lib/MC/MCInstPrinter.cpp
index 23afe8054840..912179095974 100644
--- a/lib/MC/MCInstPrinter.cpp
+++ b/lib/MC/MCInstPrinter.cpp
@@ -1,4 +1,4 @@
-//===-- MCInstPrinter.cpp - Convert an MCInst to target assembly syntax ---===//
+//===- MCInstPrinter.cpp - Convert an MCInst to target assembly syntax ----===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,13 +7,17 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCInstPrinter.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCInstPrinter.h"
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cinttypes>
+#include <cstdint>
+
 using namespace llvm;
 
 void llvm::dumpBytes(ArrayRef<uint8_t> bytes, raw_ostream &OS) {
@@ -25,8 +29,7 @@ void llvm::dumpBytes(ArrayRef<uint8_t> bytes, raw_ostream &OS) {
   }
 }
 
-MCInstPrinter::~MCInstPrinter() {
-}
+MCInstPrinter::~MCInstPrinter() = default;
 
 /// getOpcodeName - Return the name of the specified opcode enum (e.g.
 /// "MOV32ri") or empty if we can't resolve it.
@@ -68,7 +71,7 @@ StringRef MCInstPrinter::markup(StringRef a, StringRef b) const {
 // For asm-style hex (e.g. 0ffh) the first digit always has to be a number.
 static bool needsLeadingZero(uint64_t Value)
 {
-  while(Value)
+  while (Value)
   {
     uint64_t digit = (Value >> 60) & 0xf;
     if (digit != 0)
diff --git a/lib/MC/MCInstrAnalysis.cpp b/lib/MC/MCInstrAnalysis.cpp
index 2d8336d77ac7..566944c53548 100644
--- a/lib/MC/MCInstrAnalysis.cpp
+++ b/lib/MC/MCInstrAnalysis.cpp
@@ -1,4 +1,4 @@
-//===-- MCInstrAnalysis.cpp - InstrDesc target hooks ------------*- C++ -*-===//
+//===- MCInstrAnalysis.cpp - InstrDesc target hooks -----------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,7 +7,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCInstrAnalysis.h"
+#include "llvm/MC/MCInstrDesc.h"
+#include "llvm/MC/MCInstrInfo.h"
+#include <cstdint>
+
 using namespace llvm;
 
 bool MCInstrAnalysis::evaluateBranch(const MCInst &Inst, uint64_t Addr,
diff --git a/lib/MC/MCLabel.cpp b/lib/MC/MCLabel.cpp
index b443cbbbf43e..db25a46fce18 100644
--- a/lib/MC/MCLabel.cpp
+++ b/lib/MC/MCLabel.cpp
@@ -1,4 +1,4 @@
-//===- lib/MC/MCLabel.cpp - MCLabel implementation ----------------------===//
+//===- lib/MC/MCLabel.cpp - MCLabel implementation ------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -8,14 +8,18 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCLabel.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
+
 using namespace llvm;
 
 void MCLabel::print(raw_ostream &OS) const {
   OS << '"' << getInstance() << '"';
 }
 
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MCLabel::dump() const {
   print(dbgs());
 }
+#endif
diff --git a/lib/MC/MCLinkerOptimizationHint.cpp b/lib/MC/MCLinkerOptimizationHint.cpp
index f71fc7830129..97f95418e054 100644
--- a/lib/MC/MCLinkerOptimizationHint.cpp
+++ b/lib/MC/MCLinkerOptimizationHint.cpp
@@ -1,4 +1,4 @@
-//===-- llvm/MC/MCLinkerOptimizationHint.cpp ----- LOH handling -*- C++ -*-===//
+//===- llvm/MC/MCLinkerOptimizationHint.cpp ----- LOH handling ------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -9,9 +9,11 @@
 
 #include "llvm/MC/MCLinkerOptimizationHint.h"
 #include "llvm/MC/MCAsmLayout.h"
-#include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCMachObjectWriter.h"
 #include "llvm/Support/LEB128.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cstddef>
+#include <cstdint>
 
 using namespace llvm;
 
@@ -41,14 +43,14 @@ void MCLOHDirective::emit(MachObjectWriter &ObjWriter,
 uint64_t MCLOHDirective::getEmitSize(const MachObjectWriter &ObjWriter,
                                      const MCAsmLayout &Layout) const {
   class raw_counting_ostream : public raw_ostream {
-    uint64_t Count;
+    uint64_t Count = 0;
 
     void write_impl(const char *, size_t size) override { Count += size; }
 
     uint64_t current_pos() const override { return Count; }
 
   public:
-    raw_counting_ostream() : Count(0) {}
+    raw_counting_ostream() = default;
     ~raw_counting_ostream() override { flush(); }
   };
 
diff --git a/lib/MC/MCMachOStreamer.cpp b/lib/MC/MCMachOStreamer.cpp
index bd425bb73093..1e9ef4163256 100644
--- a/lib/MC/MCMachOStreamer.cpp
+++ b/lib/MC/MCMachOStreamer.cpp
@@ -1,4 +1,4 @@
-//===-- MCMachOStreamer.cpp - MachO Streamer ------------------------------===//
+//===- MCMachOStreamer.cpp - MachO Streamer -------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,27 +7,35 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCStreamer.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Triple.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCContext.h"
-#include "llvm/MC/MCDwarf.h"
+#include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCLinkerOptimizationHint.h"
 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCObjectStreamer.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionMachO.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCSymbolMachO.h"
 #include "llvm/MC/MCValue.h"
-#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/TargetRegistry.h"
+#include <cassert>
+#include <vector>
 
 using namespace llvm;
 
@@ -70,7 +78,7 @@ public:
   /// @{
 
   void ChangeSection(MCSection *Sect, const MCExpr *Subsect) override;
-  void EmitLabel(MCSymbol *Symbol) override;
+  void EmitLabel(MCSymbol *Symbol, SMLoc Loc = SMLoc()) override;
   void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) override;
   void EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
   void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
@@ -83,18 +91,7 @@ public:
   void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
   void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                         unsigned ByteAlignment) override;
-  void BeginCOFFSymbolDef(const MCSymbol *Symbol) override {
-    llvm_unreachable("macho doesn't support this directive");
-  }
-  void EmitCOFFSymbolStorageClass(int StorageClass) override {
-    llvm_unreachable("macho doesn't support this directive");
-  }
-  void EmitCOFFSymbolType(int Type) override {
-    llvm_unreachable("macho doesn't support this directive");
-  }
-  void EndCOFFSymbolDef() override {
-    llvm_unreachable("macho doesn't support this directive");
-  }
+
   void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                              unsigned ByteAlignment) override;
   void EmitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
@@ -102,13 +99,6 @@ public:
   void EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol, uint64_t Size,
                       unsigned ByteAlignment = 0) override;
 
-  void EmitFileDirective(StringRef Filename) override {
-    // FIXME: Just ignore the .file; it isn't important enough to fail the
-    // entire assembly.
-
-    // report_fatal_error("unsupported directive: '.file'");
-  }
-
   void EmitIdent(StringRef IdentString) override {
     llvm_unreachable("macho doesn't support this directive");
   }
@@ -152,7 +142,7 @@ static bool canGoAfterDWARF(const MCSectionMachO &MSec) {
 void MCMachOStreamer::ChangeSection(MCSection *Section,
                                     const MCExpr *Subsection) {
   // Change the section normally.
-  bool Created = MCObjectStreamer::changeSectionImpl(Section, Subsection);
+  bool Created = changeSectionImpl(Section, Subsection);
   const MCSectionMachO &MSec = *cast<MCSectionMachO>(Section);
   StringRef SegName = MSec.getSegmentName();
   if (SegName == "__DWARF")
@@ -181,15 +171,13 @@ void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
     EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
 }
 
-void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
-  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
-
+void MCMachOStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
   // We have to create a new fragment if this is an atom defining symbol,
   // fragments cannot span atoms.
   if (getAssembler().isSymbolLinkerVisible(*Symbol))
     insert(new MCDataFragment());
 
-  MCObjectStreamer::EmitLabel(Symbol);
+  MCObjectStreamer::EmitLabel(Symbol, Loc);
 
   // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
   // to clear the weak reference and weak definition bits too, but the
diff --git a/lib/MC/MCMachObjectTargetWriter.cpp b/lib/MC/MCMachObjectTargetWriter.cpp
index 4ffd6a78a61f..8809a3c320f8 100644
--- a/lib/MC/MCMachObjectTargetWriter.cpp
+++ b/lib/MC/MCMachObjectTargetWriter.cpp
@@ -1,4 +1,4 @@
-//===-- MCMachObjectTargetWriter.cpp - Mach-O Target Writer Subclass ------===//
+//===- MCMachObjectTargetWriter.cpp - Mach-O Target Writer Subclass -------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -16,4 +16,4 @@ MCMachObjectTargetWriter::MCMachObjectTargetWriter(bool Is64Bit_,
                                                    uint32_t CPUSubtype_)
     : Is64Bit(Is64Bit_), CPUType(CPUType_), CPUSubtype(CPUSubtype_) {}
 
-MCMachObjectTargetWriter::~MCMachObjectTargetWriter() {}
+MCMachObjectTargetWriter::~MCMachObjectTargetWriter() = default;
diff --git a/lib/MC/MCNullStreamer.cpp b/lib/MC/MCNullStreamer.cpp
index eb2d91254b34..d156f5d05a31 100644
--- a/lib/MC/MCNullStreamer.cpp
+++ b/lib/MC/MCNullStreamer.cpp
@@ -34,6 +34,10 @@ namespace {
     void EmitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
                       uint64_t Size = 0, unsigned ByteAlignment = 0) override {}
     void EmitGPRel32Value(const MCExpr *Value) override {}
+    void BeginCOFFSymbolDef(const MCSymbol *Symbol) override {}
+    void EmitCOFFSymbolStorageClass(int StorageClass) override {}
+    void EmitCOFFSymbolType(int Type) override {}
+    void EndCOFFSymbolDef() override {}
   };
 
 }
diff --git a/lib/MC/MCObjectFileInfo.cpp b/lib/MC/MCObjectFileInfo.cpp
index 8fd71f62e4e5..9f94264684f9 100644
--- a/lib/MC/MCObjectFileInfo.cpp
+++ b/lib/MC/MCObjectFileInfo.cpp
@@ -16,7 +16,9 @@
 #include "llvm/MC/MCSectionCOFF.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCSectionMachO.h"
+#include "llvm/MC/MCSectionWasm.h"
 #include "llvm/Support/COFF.h"
+#include "llvm/Support/ELF.h"
 
 using namespace llvm;
 
@@ -505,68 +507,75 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T) {
   COFFDebugSymbolsSection = nullptr;
   COFFDebugTypesSection = nullptr;
 
+  unsigned DebugSecType = ELF::SHT_PROGBITS;
+
+  // MIPS .debug_* sections should have SHT_MIPS_DWARF section type
+  // to distinguish among sections contain DWARF and ECOFF debug formats.
+  // Sections with ECOFF debug format are obsoleted and marked by SHT_PROGBITS.
+  if (T.getArch() == Triple::mips || T.getArch() == Triple::mipsel ||
+      T.getArch() == Triple::mips64 || T.getArch() == Triple::mips64el)
+    DebugSecType = ELF::SHT_MIPS_DWARF;
+
   // Debug Info Sections.
-  DwarfAbbrevSection = Ctx->getELFSection(".debug_abbrev", ELF::SHT_PROGBITS, 0,
-                                          "section_abbrev");
-  DwarfInfoSection =
-      Ctx->getELFSection(".debug_info", ELF::SHT_PROGBITS, 0, "section_info");
-  DwarfLineSection = Ctx->getELFSection(".debug_line", ELF::SHT_PROGBITS, 0);
-  DwarfFrameSection = Ctx->getELFSection(".debug_frame", ELF::SHT_PROGBITS, 0);
+  DwarfAbbrevSection =
+      Ctx->getELFSection(".debug_abbrev", DebugSecType, 0);
+  DwarfInfoSection = Ctx->getELFSection(".debug_info", DebugSecType, 0);
+  DwarfLineSection = Ctx->getELFSection(".debug_line", DebugSecType, 0);
+  DwarfFrameSection = Ctx->getELFSection(".debug_frame", DebugSecType, 0);
   DwarfPubNamesSection =
-      Ctx->getELFSection(".debug_pubnames", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_pubnames", DebugSecType, 0);
   DwarfPubTypesSection =
-      Ctx->getELFSection(".debug_pubtypes", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_pubtypes", DebugSecType, 0);
   DwarfGnuPubNamesSection =
-      Ctx->getELFSection(".debug_gnu_pubnames", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_gnu_pubnames", DebugSecType, 0);
   DwarfGnuPubTypesSection =
-      Ctx->getELFSection(".debug_gnu_pubtypes", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_gnu_pubtypes", DebugSecType, 0);
   DwarfStrSection =
-      Ctx->getELFSection(".debug_str", ELF::SHT_PROGBITS,
+      Ctx->getELFSection(".debug_str", DebugSecType,
                          ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
-  DwarfLocSection = Ctx->getELFSection(".debug_loc", ELF::SHT_PROGBITS, 0);
+  DwarfLocSection = Ctx->getELFSection(".debug_loc", DebugSecType, 0);
   DwarfARangesSection =
-      Ctx->getELFSection(".debug_aranges", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_aranges", DebugSecType, 0);
   DwarfRangesSection =
-      Ctx->getELFSection(".debug_ranges", ELF::SHT_PROGBITS, 0, "debug_range");
-  DwarfMacinfoSection = Ctx->getELFSection(".debug_macinfo", ELF::SHT_PROGBITS,
-                                           0, "debug_macinfo");
+      Ctx->getELFSection(".debug_ranges", DebugSecType, 0);
+  DwarfMacinfoSection =
+      Ctx->getELFSection(".debug_macinfo", DebugSecType, 0);
 
   // DWARF5 Experimental Debug Info
 
   // Accelerator Tables
   DwarfAccelNamesSection =
-      Ctx->getELFSection(".apple_names", ELF::SHT_PROGBITS, 0, "names_begin");
+      Ctx->getELFSection(".apple_names", ELF::SHT_PROGBITS, 0);
   DwarfAccelObjCSection =
-      Ctx->getELFSection(".apple_objc", ELF::SHT_PROGBITS, 0, "objc_begin");
-  DwarfAccelNamespaceSection = Ctx->getELFSection(
-      ".apple_namespaces", ELF::SHT_PROGBITS, 0, "namespac_begin");
+      Ctx->getELFSection(".apple_objc", ELF::SHT_PROGBITS, 0);
+  DwarfAccelNamespaceSection =
+      Ctx->getELFSection(".apple_namespaces", ELF::SHT_PROGBITS, 0);
   DwarfAccelTypesSection =
-      Ctx->getELFSection(".apple_types", ELF::SHT_PROGBITS, 0, "types_begin");
+      Ctx->getELFSection(".apple_types", ELF::SHT_PROGBITS, 0);
 
   // Fission Sections
   DwarfInfoDWOSection =
-      Ctx->getELFSection(".debug_info.dwo", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_info.dwo", DebugSecType, 0);
   DwarfTypesDWOSection =
-      Ctx->getELFSection(".debug_types.dwo", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_types.dwo", DebugSecType, 0);
   DwarfAbbrevDWOSection =
-      Ctx->getELFSection(".debug_abbrev.dwo", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_abbrev.dwo", DebugSecType, 0);
   DwarfStrDWOSection =
-      Ctx->getELFSection(".debug_str.dwo", ELF::SHT_PROGBITS,
+      Ctx->getELFSection(".debug_str.dwo", DebugSecType,
                          ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
   DwarfLineDWOSection =
-      Ctx->getELFSection(".debug_line.dwo", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_line.dwo", DebugSecType, 0);
   DwarfLocDWOSection =
-      Ctx->getELFSection(".debug_loc.dwo", ELF::SHT_PROGBITS, 0, "skel_loc");
+      Ctx->getELFSection(".debug_loc.dwo", DebugSecType, 0);
   DwarfStrOffDWOSection =
-      Ctx->getELFSection(".debug_str_offsets.dwo", ELF::SHT_PROGBITS, 0);
-  DwarfAddrSection =
-      Ctx->getELFSection(".debug_addr", ELF::SHT_PROGBITS, 0, "addr_sec");
+      Ctx->getELFSection(".debug_str_offsets.dwo", DebugSecType, 0);
+  DwarfAddrSection = Ctx->getELFSection(".debug_addr", DebugSecType, 0);
 
   // DWP Sections
   DwarfCUIndexSection =
-      Ctx->getELFSection(".debug_cu_index", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_cu_index", DebugSecType, 0);
   DwarfTUIndexSection =
-      Ctx->getELFSection(".debug_tu_index", ELF::SHT_PROGBITS, 0);
+      Ctx->getELFSection(".debug_tu_index", DebugSecType, 0);
 
   StackMapSection =
       Ctx->getELFSection(".llvm_stackmaps", ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
@@ -799,6 +808,30 @@ void MCObjectFileInfo::initCOFFMCObjectFileInfo(const Triple &T) {
                                         SectionKind::getReadOnly());
 }
 
+void MCObjectFileInfo::initWasmMCObjectFileInfo(const Triple &T) {
+  // TODO: Set the section types and flags.
+  TextSection = Ctx->getWasmSection(".text", 0, 0);
+  DataSection = Ctx->getWasmSection(".data", 0, 0);
+
+  // TODO: Set the section types and flags.
+  DwarfLineSection = Ctx->getWasmSection(".debug_line", 0, 0);
+  DwarfStrSection = Ctx->getWasmSection(".debug_str", 0, 0);
+  DwarfLocSection = Ctx->getWasmSection(".debug_loc", 0, 0);
+  DwarfAbbrevSection = Ctx->getWasmSection(".debug_abbrev", 0, 0, "section_abbrev");
+  DwarfARangesSection = Ctx->getWasmSection(".debug_aranges", 0, 0);
+  DwarfRangesSection = Ctx->getWasmSection(".debug_ranges", 0, 0, "debug_range");
+  DwarfMacinfoSection = Ctx->getWasmSection(".debug_macinfo", 0, 0, "debug_macinfo");
+  DwarfAddrSection = Ctx->getWasmSection(".debug_addr", 0, 0);
+  DwarfCUIndexSection = Ctx->getWasmSection(".debug_cu_index", 0, 0);
+  DwarfTUIndexSection = Ctx->getWasmSection(".debug_tu_index", 0, 0);
+  DwarfInfoSection = Ctx->getWasmSection(".debug_info", 0, 0, "section_info");
+  DwarfFrameSection = Ctx->getWasmSection(".debug_frame", 0, 0);
+  DwarfPubNamesSection = Ctx->getWasmSection(".debug_pubnames", 0, 0);
+  DwarfPubTypesSection = Ctx->getWasmSection(".debug_pubtypes", 0, 0);
+
+  // TODO: Define more sections.
+}
+
 void MCObjectFileInfo::InitMCObjectFileInfo(const Triple &TheTriple, bool PIC,
                                             CodeModel::Model cm,
                                             MCContext &ctx) {
@@ -843,6 +876,10 @@ void MCObjectFileInfo::InitMCObjectFileInfo(const Triple &TheTriple, bool PIC,
     Env = IsELF;
     initELFMCObjectFileInfo(TT);
     break;
+  case Triple::Wasm:
+    Env = IsWasm;
+    initWasmMCObjectFileInfo(TT);
+    break;
   case Triple::UnknownObjectFormat:
     report_fatal_error("Cannot initialize MC for unknown object file format.");
     break;
diff --git a/lib/MC/MCObjectStreamer.cpp b/lib/MC/MCObjectStreamer.cpp
index cae5c1f8d156..f7f2253256eb 100644
--- a/lib/MC/MCObjectStreamer.cpp
+++ b/lib/MC/MCObjectStreamer.cpp
@@ -153,8 +153,8 @@ void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
   EmitLabel(Frame.End);
 }
 
-void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
-  MCStreamer::EmitLabel(Symbol);
+void MCObjectStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
+  MCStreamer::EmitLabel(Symbol, Loc);
 
   getAssembler().registerSymbol(*Symbol);
 
@@ -171,6 +171,16 @@ void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
   }
 }
 
+void MCObjectStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc, MCFragment *F) {
+  MCStreamer::EmitLabel(Symbol, Loc);
+  getAssembler().registerSymbol(*Symbol);
+  auto *DF = dyn_cast_or_null<MCDataFragment>(F);
+  if (DF)
+    Symbol->setFragment(F);
+  else
+    PendingLabels.push_back(Symbol);
+}
+
 void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) {
   int64_t IntValue;
   if (Value->evaluateAsAbsolute(IntValue, getAssembler())) {
@@ -203,6 +213,7 @@ bool MCObjectStreamer::changeSectionImpl(MCSection *Section,
                                          const MCExpr *Subsection) {
   assert(Section && "Cannot switch to a null section!");
   flushPendingLabels(nullptr);
+  getContext().clearDwarfLocSeen();
 
   bool Created = getAssembler().registerSection(*Section);
 
@@ -227,7 +238,7 @@ bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const {
 }
 
 void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
-                                       const MCSubtargetInfo &STI) {
+                                       const MCSubtargetInfo &STI, bool) {
   MCStreamer::EmitInstruction(Inst, STI);
 
   MCSection *Sec = getCurrentSectionOnly();
@@ -490,8 +501,8 @@ void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) {
   MCDataFragment *DF = getOrCreateDataFragment();
   flushPendingLabels(DF, DF->getContents().size());
 
-  DF->getFixups().push_back(MCFixup::create(DF->getContents().size(), 
-                                            Value, FK_GPRel_4));
+  DF->getFixups().push_back(
+      MCFixup::create(DF->getContents().size(), Value, FK_GPRel_4));
   DF->getContents().resize(DF->getContents().size() + 4, 0);
 }
 
@@ -500,8 +511,8 @@ void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) {
   MCDataFragment *DF = getOrCreateDataFragment();
   flushPendingLabels(DF, DF->getContents().size());
 
-  DF->getFixups().push_back(MCFixup::create(DF->getContents().size(), 
-                                            Value, FK_GPRel_4));
+  DF->getFixups().push_back(
+      MCFixup::create(DF->getContents().size(), Value, FK_GPRel_4));
   DF->getContents().resize(DF->getContents().size() + 8, 0);
 }
 
@@ -572,6 +583,10 @@ void MCObjectStreamer::emitFill(const MCExpr &NumValues, int64_t Size,
   MCStreamer::emitFill(IntNumValues, Size, Expr);
 }
 
+void MCObjectStreamer::EmitFileDirective(StringRef Filename) {
+  getAssembler().addFileName(Filename);
+}
+
 void MCObjectStreamer::FinishImpl() {
   // If we are generating dwarf for assembly source files dump out the sections.
   if (getContext().getGenDwarfForAssembly())
diff --git a/lib/MC/MCObjectWriter.cpp b/lib/MC/MCObjectWriter.cpp
index e84f74ae81d6..478b4e84e74a 100644
--- a/lib/MC/MCObjectWriter.cpp
+++ b/lib/MC/MCObjectWriter.cpp
@@ -8,14 +8,14 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCAssembler.h"
+#include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSymbol.h"
 
 using namespace llvm;
 
-MCObjectWriter::~MCObjectWriter() {
-}
+MCObjectWriter::~MCObjectWriter() = default;
 
 bool MCObjectWriter::isSymbolRefDifferenceFullyResolved(
     const MCAssembler &Asm, const MCSymbolRefExpr *A, const MCSymbolRefExpr *B,
@@ -51,5 +51,3 @@ bool MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
   // On ELF and COFF  A - B is absolute if A and B are in the same section.
   return &SecA == &SecB;
 }
-
-bool MCObjectWriter::isWeak(const MCSymbol &) const { return false; }
diff --git a/lib/MC/MCParser/AsmLexer.cpp b/lib/MC/MCParser/AsmLexer.cpp
index 87ecf9e0227f..38dadfe62135 100644
--- a/lib/MC/MCParser/AsmLexer.cpp
+++ b/lib/MC/MCParser/AsmLexer.cpp
@@ -11,12 +11,12 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCParser/AsmLexer.h"
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCParser/AsmLexer.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
 #include "llvm/Support/SMLoc.h"
 #include "llvm/Support/SaveAndRestore.h"
@@ -30,15 +30,11 @@
 
 using namespace llvm;
 
-AsmLexer::AsmLexer(const MCAsmInfo &MAI)
-    : MAI(MAI), CurPtr(nullptr), IsAtStartOfLine(true),
-      IsAtStartOfStatement(true), IsParsingMSInlineAsm(false),
-      IsPeeking(false) {
+AsmLexer::AsmLexer(const MCAsmInfo &MAI) : MAI(MAI) {
   AllowAtInIdentifier = !StringRef(MAI.getCommentString()).startswith("@");
 }
 
-AsmLexer::~AsmLexer() {
-}
+AsmLexer::~AsmLexer() = default;
 
 void AsmLexer::setBuffer(StringRef Buf, const char *ptr) {
   CurBuf = Buf;
diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index da54155b3b9d..e65ce9f0b936 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -35,6 +35,7 @@
 #include "llvm/MC/MCParser/AsmLexer.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
 #include "llvm/MC/MCParser/MCAsmParser.h"
+#include "llvm/MC/MCParser/MCAsmParserExtension.h"
 #include "llvm/MC/MCParser/MCAsmParserUtils.h"
 #include "llvm/MC/MCParser/MCParsedAsmOperand.h"
 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
@@ -42,6 +43,7 @@
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCTargetOptions.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/CommandLine.h"
@@ -55,6 +57,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cctype>
+#include <climits>
 #include <cstddef>
 #include <cstdint>
 #include <deque>
@@ -67,7 +70,7 @@
 
 using namespace llvm;
 
-MCAsmParserSemaCallback::~MCAsmParserSemaCallback() {}
+MCAsmParserSemaCallback::~MCAsmParserSemaCallback() = default;
 
 static cl::opt<unsigned> AsmMacroMaxNestingDepth(
      "asm-macro-max-nesting-depth", cl::init(20), cl::Hidden,
@@ -82,10 +85,10 @@ typedef std::vector<MCAsmMacroArgument> MCAsmMacroArguments;
 struct MCAsmMacroParameter {
   StringRef Name;
   MCAsmMacroArgument Value;
-  bool Required;
-  bool Vararg;
+  bool Required = false;
+  bool Vararg = false;
 
-  MCAsmMacroParameter() : Required(false), Vararg(false) {}
+  MCAsmMacroParameter() = default;
 };
 
 typedef std::vector<MCAsmMacroParameter> MCAsmMacroParameters;
@@ -124,23 +127,20 @@ struct ParseStatementInfo {
   SmallVector<std::unique_ptr<MCParsedAsmOperand>, 8> ParsedOperands;
 
   /// \brief The opcode from the last parsed instruction.
-  unsigned Opcode;
+  unsigned Opcode = ~0U;
 
   /// \brief Was there an error parsing the inline assembly?
-  bool ParseError;
+  bool ParseError = false;
 
-  SmallVectorImpl<AsmRewrite> *AsmRewrites;
+  SmallVectorImpl<AsmRewrite> *AsmRewrites = nullptr;
 
-  ParseStatementInfo() : Opcode(~0U), ParseError(false), AsmRewrites(nullptr) {}
+  ParseStatementInfo() = default;
   ParseStatementInfo(SmallVectorImpl<AsmRewrite> *rewrites)
-    : Opcode(~0), ParseError(false), AsmRewrites(rewrites) {}
+    : AsmRewrites(rewrites) {}
 };
 
 /// \brief The concrete assembly parser instance.
 class AsmParser : public MCAsmParser {
-  AsmParser(const AsmParser &) = delete;
-  void operator=(const AsmParser &) = delete;
-
 private:
   AsmLexer Lexer;
   MCContext &Ctx;
@@ -199,17 +199,19 @@ private:
   unsigned LastQueryLine;
 
   /// AssemblerDialect. ~OU means unset value and use value provided by MAI.
-  unsigned AssemblerDialect;
+  unsigned AssemblerDialect = ~0U;
 
   /// \brief is Darwin compatibility enabled?
-  bool IsDarwin;
+  bool IsDarwin = false;
 
   /// \brief Are we parsing ms-style inline assembly?
-  bool ParsingInlineAsm;
+  bool ParsingInlineAsm = false;
 
 public:
   AsmParser(SourceMgr &SM, MCContext &Ctx, MCStreamer &Out,
-            const MCAsmInfo &MAI);
+            const MCAsmInfo &MAI, unsigned CB);
+  AsmParser(const AsmParser &) = delete;
+  AsmParser &operator=(const AsmParser &) = delete;
   ~AsmParser() override;
 
   bool Run(bool NoInitialTextSection, bool NoFinalize = false) override;
@@ -223,7 +225,6 @@ public:
     DirectiveKindMap[Directive] = DirectiveKindMap[Alias];
   }
 
-public:
   /// @name MCAsmParser Interface
   /// {
 
@@ -258,7 +259,7 @@ public:
 
   bool parseMSInlineAsm(void *AsmLoc, std::string &AsmString,
                         unsigned &NumOutputs, unsigned &NumInputs,
-                        SmallVectorImpl<std::pair<void *,bool> > &OpDecls,
+                        SmallVectorImpl<std::pair<void *,bool>> &OpDecls,
                         SmallVectorImpl<std::string> &Constraints,
                         SmallVectorImpl<std::string> &Clobbers,
                         const MCInstrInfo *MII, const MCInstPrinter *IP,
@@ -572,11 +573,9 @@ extern MCAsmParserExtension *createCOFFAsmParser();
 enum { DEFAULT_ADDRSPACE = 0 };
 
 AsmParser::AsmParser(SourceMgr &SM, MCContext &Ctx, MCStreamer &Out,
-                     const MCAsmInfo &MAI)
+                     const MCAsmInfo &MAI, unsigned CB = 0)
     : Lexer(MAI), Ctx(Ctx), Out(Out), MAI(MAI), SrcMgr(SM),
-      PlatformParser(nullptr), CurBuffer(SM.getMainFileID()),
-      MacrosEnabledFlag(true), CppHashInfo(), AssemblerDialect(~0U),
-      IsDarwin(false), ParsingInlineAsm(false) {
+      CurBuffer(CB ? CB : SM.getMainFileID()), MacrosEnabledFlag(true) {
   HadError = false;
   // Save the old handler.
   SavedDiagHandler = SrcMgr.getDiagHandler();
@@ -597,6 +596,9 @@ AsmParser::AsmParser(SourceMgr &SM, MCContext &Ctx, MCStreamer &Out,
   case MCObjectFileInfo::IsELF:
     PlatformParser.reset(createELFAsmParser());
     break;
+  case MCObjectFileInfo::IsWasm:
+    llvm_unreachable("Wasm parsing not supported yet");
+    break;
   }
 
   PlatformParser->Initialize(*this);
@@ -608,6 +610,10 @@ AsmParser::AsmParser(SourceMgr &SM, MCContext &Ctx, MCStreamer &Out,
 AsmParser::~AsmParser() {
   assert((HadError || ActiveMacros.empty()) &&
          "Unexpected active macro instantiation!");
+
+  // Restore the saved diagnostics handler and context for use during
+  // finalization.
+  SrcMgr.setDiagHandler(SavedDiagHandler, SavedDiagContext);
 }
 
 void AsmParser::printMacroInstantiations() {
@@ -918,7 +924,7 @@ bool AsmParser::parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
     Lex(); // Eat the operator.
     if (parsePrimaryExpr(Res, EndLoc))
       return true;
-    Res = MCUnaryExpr::createLNot(Res, getContext());
+    Res = MCUnaryExpr::createLNot(Res, getContext(), FirstTokenLoc);
     return false;
   case AsmToken::Dollar:
   case AsmToken::At:
@@ -979,7 +985,7 @@ bool AsmParser::parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
     MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
 
     // Lookup the symbol variant if used.
-    if (Split.second.size()) {
+    if (!Split.second.empty()) {
       Variant = MCSymbolRefExpr::getVariantKindForName(Split.second);
       if (Variant != MCSymbolRefExpr::VK_Invalid) {
         SymbolName = Split.first;
@@ -1005,7 +1011,7 @@ bool AsmParser::parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
     }
 
     // Otherwise create a symbol ref.
-    Res = MCSymbolRefExpr::create(Sym, Variant, getContext());
+    Res = MCSymbolRefExpr::create(Sym, Variant, getContext(), FirstTokenLoc);
     return false;
   }
   case AsmToken::BigNum:
@@ -1071,19 +1077,19 @@ bool AsmParser::parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
     Lex(); // Eat the operator.
     if (parsePrimaryExpr(Res, EndLoc))
       return true;
-    Res = MCUnaryExpr::createMinus(Res, getContext());
+    Res = MCUnaryExpr::createMinus(Res, getContext(), FirstTokenLoc);
     return false;
   case AsmToken::Plus:
     Lex(); // Eat the operator.
     if (parsePrimaryExpr(Res, EndLoc))
       return true;
-    Res = MCUnaryExpr::createPlus(Res, getContext());
+    Res = MCUnaryExpr::createPlus(Res, getContext(), FirstTokenLoc);
     return false;
   case AsmToken::Tilde:
     Lex(); // Eat the operator.
     if (parsePrimaryExpr(Res, EndLoc))
       return true;
-    Res = MCUnaryExpr::createNot(Res, getContext());
+    Res = MCUnaryExpr::createNot(Res, getContext(), FirstTokenLoc);
     return false;
   // MIPS unary expression operators. The lexer won't generate these tokens if
   // MCAsmInfo::HasMipsExpressions is false for the target.
@@ -1436,6 +1442,7 @@ unsigned AsmParser::getBinOpPrecedence(AsmToken::TokenKind K,
 /// Res contains the LHS of the expression on input.
 bool AsmParser::parseBinOpRHS(unsigned Precedence, const MCExpr *&Res,
                               SMLoc &EndLoc) {
+  SMLoc StartLoc = Lexer.getLoc();
   while (true) {
     MCBinaryExpr::Opcode Kind = MCBinaryExpr::Add;
     unsigned TokPrec = getBinOpPrecedence(Lexer.getKind(), Kind);
@@ -1460,7 +1467,7 @@ bool AsmParser::parseBinOpRHS(unsigned Precedence, const MCExpr *&Res,
       return true;
 
     // Merge LHS and RHS according to operator.
-    Res = MCBinaryExpr::create(Kind, Res, RHS, getContext());
+    Res = MCBinaryExpr::create(Kind, Res, RHS, getContext(), StartLoc);
   }
 }
 
@@ -1617,7 +1624,7 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
       if (ParsingInlineAsm && SI) {
         StringRef RewrittenLabel =
             SI->LookupInlineAsmLabel(IDVal, getSourceManager(), IDLoc, true);
-        assert(RewrittenLabel.size() &&
+        assert(!RewrittenLabel.empty() &&
                "We should have an internal name here.");
         Info.AsmRewrites->emplace_back(AOK_Label, IDLoc, IDVal.size(),
                                        RewrittenLabel);
@@ -1626,12 +1633,6 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
       Sym = getContext().getOrCreateSymbol(IDVal);
     } else
       Sym = Ctx.createDirectionalLocalSymbol(LocalLabelVal);
-
-    Sym->redefineIfPossible();
-
-    if (!Sym->isUndefined() || Sym->isVariable())
-      return Error(IDLoc, "invalid symbol redefinition");
-
     // End of Labels should be treated as end of line for lexing
     // purposes but that information is not available to the Lexer who
     // does not understand Labels. This may cause us to see a Hash
@@ -1650,7 +1651,7 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
 
     // Emit the label.
     if (!ParsingInlineAsm)
-      Out.EmitLabel(Sym);
+      Out.EmitLabel(Sym, IDLoc);
 
     // If we are generating dwarf for assembly source files then gather the
     // info to make a dwarf label entry for this label if needed.
@@ -1979,7 +1980,7 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
   if (ParsingInlineAsm && (IDVal == "align" || IDVal == "ALIGN"))
     return parseDirectiveMSAlign(IDLoc, Info);
 
-  if (ParsingInlineAsm && (IDVal == "even"))
+  if (ParsingInlineAsm && (IDVal == "even" || IDVal == "EVEN"))
     Info.AsmRewrites->emplace_back(AOK_EVEN, IDLoc, 4);
   if (checkForValidSection())
     return true;
@@ -2025,7 +2026,7 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
     // If we previously parsed a cpp hash file line comment then make sure the
     // current Dwarf File is for the CppHashFilename if not then emit the
     // Dwarf File table for it and adjust the line number for the .loc.
-    if (CppHashInfo.Filename.size()) {
+    if (!CppHashInfo.Filename.empty()) {
       unsigned FileNumber = getStreamer().EmitDwarfFileDirective(
           0, StringRef(), CppHashInfo.Filename);
       getContext().setGenDwarfFileNumber(FileNumber);
@@ -3873,6 +3874,12 @@ bool AsmParser::parseDirectiveMacro(SMLoc DirectiveLoc) {
     if (parseIdentifier(Parameter.Name))
       return TokError("expected identifier in '.macro' directive");
 
+    // Emit an error if two (or more) named parameters share the same name
+    for (const MCAsmMacroParameter& CurrParam : Parameters)
+      if (CurrParam.Name.equals(Parameter.Name))
+        return TokError("macro '" + Name + "' has multiple parameters"
+                        " named '" + Parameter.Name + "'");
+
     if (Lexer.is(AsmToken::Colon)) {
       Lex();  // consume ':'
 
@@ -4191,7 +4198,6 @@ bool AsmParser::parseDirectiveBundleUnlock() {
 /// parseDirectiveSpace
 /// ::= (.skip | .space) expression [ , expression ]
 bool AsmParser::parseDirectiveSpace(StringRef IDVal) {
-
   SMLoc NumBytesLoc = Lexer.getLoc();
   const MCExpr *NumBytes;
   if (checkForValidSection() || parseExpression(NumBytes))
@@ -4287,7 +4293,6 @@ bool AsmParser::parseDirectiveRealDCB(StringRef IDVal, const fltSemantics &Seman
 /// parseDirectiveDS
 /// ::= .ds.{b, d, l, p, s, w, x} expression
 bool AsmParser::parseDirectiveDS(StringRef IDVal, unsigned Size) {
-
   SMLoc NumValuesLoc = Lexer.getLoc();
   int64_t NumValues;
   if (checkForValidSection() || parseAbsoluteExpression(NumValues))
@@ -4416,6 +4421,7 @@ bool AsmParser::parseDirectiveComm(bool IsLocal) {
     return Error(Pow2AlignmentLoc, "invalid '.comm' or '.lcomm' directive "
                                    "alignment, can't be less than zero");
 
+  Sym->redefineIfPossible();
   if (!Sym->isUndefined())
     return Error(IDLoc, "invalid symbol redefinition");
 
@@ -5208,7 +5214,7 @@ static int rewritesSort(const AsmRewrite *AsmRewriteA,
 
 bool AsmParser::parseMSInlineAsm(
     void *AsmLoc, std::string &AsmString, unsigned &NumOutputs,
-    unsigned &NumInputs, SmallVectorImpl<std::pair<void *, bool> > &OpDecls,
+    unsigned &NumInputs, SmallVectorImpl<std::pair<void *, bool>> &OpDecls,
     SmallVectorImpl<std::string> &Constraints,
     SmallVectorImpl<std::string> &Clobbers, const MCInstrInfo *MII,
     const MCInstPrinter *IP, MCAsmParserSemaCallback &SI) {
@@ -5518,6 +5524,7 @@ bool parseAssignmentExpression(StringRef Name, bool allow_redef,
 
 /// \brief Create an MCAsmParser instance.
 MCAsmParser *llvm::createMCAsmParser(SourceMgr &SM, MCContext &C,
-                                     MCStreamer &Out, const MCAsmInfo &MAI) {
-  return new AsmParser(SM, C, Out, MAI);
+                                     MCStreamer &Out, const MCAsmInfo &MAI,
+                                     unsigned CB) {
+  return new AsmParser(SM, C, Out, MAI, CB);
 }
diff --git a/lib/MC/MCParser/COFFAsmParser.cpp b/lib/MC/MCParser/COFFAsmParser.cpp
index f4114795a92d..bec62ccb2f7f 100644
--- a/lib/MC/MCParser/COFFAsmParser.cpp
+++ b/lib/MC/MCParser/COFFAsmParser.cpp
@@ -7,19 +7,27 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCParser/MCAsmParserExtension.h"
 #include "llvm/ADT/StringSwitch.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Triple.h"
 #include "llvm/ADT/Twine.h"
-#include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
-#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
+#include "llvm/MC/MCParser/MCAsmParserExtension.h"
 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSectionCOFF.h"
 #include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/SectionKind.h"
 #include "llvm/Support/COFF.h"
+#include "llvm/Support/SMLoc.h"
+#include <cassert>
+#include <cstdint>
+#include <limits>
+#include <utility>
+
 using namespace llvm;
 
 namespace {
@@ -98,12 +106,14 @@ class COFFAsmParser : public MCAsmParserExtension {
                             | COFF::IMAGE_SCN_MEM_READ,
                               SectionKind::getText());
   }
+
   bool ParseSectionDirectiveData(StringRef, SMLoc) {
     return ParseSectionSwitch(".data", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
                                            COFF::IMAGE_SCN_MEM_READ |
                                            COFF::IMAGE_SCN_MEM_WRITE,
                               SectionKind::getData());
   }
+
   bool ParseSectionDirectiveBSS(StringRef, SMLoc) {
     return ParseSectionSwitch(".bss",
                               COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA
@@ -141,8 +151,9 @@ class COFFAsmParser : public MCAsmParserExtension {
   bool ParseAtUnwindOrAtExcept(bool &unwind, bool &except);
   bool ParseSEHRegisterNumber(unsigned &RegNo);
   bool ParseDirectiveSymbolAttribute(StringRef Directive, SMLoc);
+
 public:
-  COFFAsmParser() {}
+  COFFAsmParser() = default;
 };
 
 } // end annonomous namespace.
@@ -277,7 +288,7 @@ bool COFFAsmParser::ParseDirectiveSymbolAttribute(StringRef Directive, SMLoc) {
     .Default(MCSA_Invalid);
   assert(Attr != MCSA_Invalid && "unexpected symbol attribute directive!");
   if (getLexer().isNot(AsmToken::EndOfStatement)) {
-    for (;;) {
+    while (true) {
       StringRef Name;
 
       if (getParser().parseIdentifier(Name))
@@ -466,10 +477,11 @@ bool COFFAsmParser::ParseDirectiveSecRel32(StringRef, SMLoc) {
   if (getLexer().isNot(AsmToken::EndOfStatement))
     return TokError("unexpected token in directive");
 
-  if (Offset < 0 || Offset > UINT32_MAX)
-    return Error(OffsetLoc,
-                 "invalid '.secrel32' directive offset, can't be less "
-                 "than zero or greater than UINT32_MAX");
+  if (Offset < 0 || Offset > std::numeric_limits<uint32_t>::max())
+    return Error(
+        OffsetLoc,
+        "invalid '.secrel32' directive offset, can't be less "
+        "than zero or greater than std::numeric_limits<uint32_t>::max()");
 
   MCSymbol *Symbol = getContext().getOrCreateSymbol(SymbolID);
 
@@ -817,4 +829,4 @@ MCAsmParserExtension *createCOFFAsmParser() {
   return new COFFAsmParser;
 }
 
-}
+} // end namespace llvm
diff --git a/lib/MC/MCParser/DarwinAsmParser.cpp b/lib/MC/MCParser/DarwinAsmParser.cpp
index 94aa70ef0326..73a7ad0500c3 100644
--- a/lib/MC/MCParser/DarwinAsmParser.cpp
+++ b/lib/MC/MCParser/DarwinAsmParser.cpp
@@ -7,22 +7,35 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCParser/MCAsmParserExtension.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
 #include "llvm/MC/MCParser/MCAsmParser.h"
+#include "llvm/MC/MCParser/MCAsmParserExtension.h"
 #include "llvm/MC/MCSectionMachO.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/SectionKind.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/MachO.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/SMLoc.h"
 #include "llvm/Support/SourceMgr.h"
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <system_error>
+#include <utility>
+
 using namespace llvm;
 
 namespace {
@@ -44,7 +57,7 @@ class DarwinAsmParser : public MCAsmParserExtension {
   SMLoc LastVersionMinDirective;
 
 public:
-  DarwinAsmParser() {}
+  DarwinAsmParser() = default;
 
   void Initialize(MCAsmParser &Parser) override {
     // Call the base implementation.
@@ -209,37 +222,47 @@ public:
   bool parseSectionDirectiveConst(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT", "__const");
   }
+
   bool parseSectionDirectiveStaticConst(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT", "__static_const");
   }
+
   bool parseSectionDirectiveCString(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT","__cstring",
                               MachO::S_CSTRING_LITERALS);
   }
+
   bool parseSectionDirectiveLiteral4(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT", "__literal4",
                               MachO::S_4BYTE_LITERALS, 4);
   }
+
   bool parseSectionDirectiveLiteral8(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT", "__literal8",
                               MachO::S_8BYTE_LITERALS, 8);
   }
+
   bool parseSectionDirectiveLiteral16(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT","__literal16",
                               MachO::S_16BYTE_LITERALS, 16);
   }
+
   bool parseSectionDirectiveConstructor(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT","__constructor");
   }
+
   bool parseSectionDirectiveDestructor(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT","__destructor");
   }
+
   bool parseSectionDirectiveFVMLibInit0(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT","__fvmlib_init0");
   }
+
   bool parseSectionDirectiveFVMLibInit1(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT","__fvmlib_init1");
   }
+
   bool parseSectionDirectiveSymbolStub(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT","__symbol_stub",
                               MachO::S_SYMBOL_STUBS |
@@ -247,144 +270,178 @@ public:
                               // FIXME: Different on PPC and ARM.
                               0, 16);
   }
+
   bool parseSectionDirectivePICSymbolStub(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT","__picsymbol_stub",
                               MachO::S_SYMBOL_STUBS |
                               MachO::S_ATTR_PURE_INSTRUCTIONS, 0, 26);
   }
+
   bool parseSectionDirectiveData(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__data");
   }
+
   bool parseSectionDirectiveStaticData(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__static_data");
   }
+
   bool parseSectionDirectiveNonLazySymbolPointers(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__nl_symbol_ptr",
                               MachO::S_NON_LAZY_SYMBOL_POINTERS, 4);
   }
+
   bool parseSectionDirectiveLazySymbolPointers(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__la_symbol_ptr",
                               MachO::S_LAZY_SYMBOL_POINTERS, 4);
   }
+
   bool parseSectionDirectiveThreadLocalVariablePointers(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__thread_ptr",
                               MachO::S_THREAD_LOCAL_VARIABLE_POINTERS, 4);
   }
+
   bool parseSectionDirectiveDyld(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__dyld");
   }
+
   bool parseSectionDirectiveModInitFunc(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__mod_init_func",
                               MachO::S_MOD_INIT_FUNC_POINTERS, 4);
   }
+
   bool parseSectionDirectiveModTermFunc(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__mod_term_func",
                               MachO::S_MOD_TERM_FUNC_POINTERS, 4);
   }
+
   bool parseSectionDirectiveConstData(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__const");
   }
+
   bool parseSectionDirectiveObjCClass(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__class",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCMetaClass(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__meta_class",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCCatClsMeth(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__cat_cls_meth",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCCatInstMeth(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__cat_inst_meth",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCProtocol(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__protocol",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCStringObject(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__string_object",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCClsMeth(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__cls_meth",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCInstMeth(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__inst_meth",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCClsRefs(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__cls_refs",
                               MachO::S_ATTR_NO_DEAD_STRIP |
                               MachO::S_LITERAL_POINTERS, 4);
   }
+
   bool parseSectionDirectiveObjCMessageRefs(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__message_refs",
                               MachO::S_ATTR_NO_DEAD_STRIP |
                               MachO::S_LITERAL_POINTERS, 4);
   }
+
   bool parseSectionDirectiveObjCSymbols(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__symbols",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCCategory(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__category",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCClassVars(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__class_vars",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCInstanceVars(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__instance_vars",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCModuleInfo(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__module_info",
                               MachO::S_ATTR_NO_DEAD_STRIP);
   }
+
   bool parseSectionDirectiveObjCClassNames(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT", "__cstring",
                               MachO::S_CSTRING_LITERALS);
   }
+
   bool parseSectionDirectiveObjCMethVarTypes(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT", "__cstring",
                               MachO::S_CSTRING_LITERALS);
   }
+
   bool parseSectionDirectiveObjCMethVarNames(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT", "__cstring",
                               MachO::S_CSTRING_LITERALS);
   }
+
   bool parseSectionDirectiveObjCSelectorStrs(StringRef, SMLoc) {
     return parseSectionSwitch("__OBJC", "__selector_strs",
                               MachO::S_CSTRING_LITERALS);
   }
+
   bool parseSectionDirectiveTData(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__thread_data",
                               MachO::S_THREAD_LOCAL_REGULAR);
   }
+
   bool parseSectionDirectiveText(StringRef, SMLoc) {
     return parseSectionSwitch("__TEXT", "__text",
                               MachO::S_ATTR_PURE_INSTRUCTIONS);
   }
+
   bool parseSectionDirectiveTLV(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__thread_vars",
                               MachO::S_THREAD_LOCAL_VARIABLES);
   }
+
   bool parseSectionDirectiveIdent(StringRef, SMLoc) {
     // Darwin silently ignores the .ident directive.
     getParser().eatToEndOfStatement();
     return false;
   }
+
   bool parseSectionDirectiveThreadInitFunc(StringRef, SMLoc) {
     return parseSectionSwitch("__DATA", "__thread_init",
                          MachO::S_THREAD_LOCAL_INIT_FUNCTION_POINTERS);
   }
-  bool parseVersionMin(StringRef, SMLoc);
 
+  bool parseVersionMin(StringRef, SMLoc);
 };
 
 } // end anonymous namespace
@@ -526,7 +583,7 @@ bool DarwinAsmParser::parseDirectiveDumpOrLoad(StringRef Directive,
 ///  ::= .linker_option "string" ( , "string" )*
 bool DarwinAsmParser::parseDirectiveLinkerOption(StringRef IDVal, SMLoc) {
   SmallVector<std::string, 4> Args;
-  for (;;) {
+  while (true) {
     if (getLexer().isNot(AsmToken::String))
       return TokError("expected string in '" + Twine(IDVal) + "' directive");
 
@@ -604,7 +661,6 @@ bool DarwinAsmParser::parseDirectiveSection(StringRef, SMLoc) {
     return TokError("unexpected token in '.section' directive");
   Lex();
 
-
   StringRef Segment, Section;
   unsigned StubSize;
   unsigned TAA;
diff --git a/lib/MC/MCParser/ELFAsmParser.cpp b/lib/MC/MCParser/ELFAsmParser.cpp
index 8d7ba0d03362..401011a027f4 100644
--- a/lib/MC/MCParser/ELFAsmParser.cpp
+++ b/lib/MC/MCParser/ELFAsmParser.cpp
@@ -7,17 +7,29 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCParser/MCAsmParserExtension.h"
 #include "llvm/ADT/StringSwitch.h"
-#include "llvm/ADT/Twine.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
+#include "llvm/MC/MCParser/MCAsmParser.h"
+#include "llvm/MC/MCParser/MCAsmParserExtension.h"
+#include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCSymbolELF.h"
+#include "llvm/MC/SectionKind.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/ELF.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/SMLoc.h"
+#include <cassert>
+#include <cstdint>
+#include <utility>
+
 using namespace llvm;
 
 namespace {
@@ -142,9 +154,14 @@ private:
   bool ParseSectionName(StringRef &SectionName);
   bool ParseSectionArguments(bool IsPush, SMLoc loc);
   unsigned parseSunStyleSectionFlags();
+  bool maybeParseSectionType(StringRef &TypeName);
+  bool parseMergeSize(int64_t &Size);
+  bool parseGroup(StringRef &GroupName);
+  bool parseMetadataSym(MCSymbolELF *&Associated);
+  bool maybeParseUniqueID(int64_t &UniqueID);
 };
 
-}
+} // end anonymous namespace
 
 /// ParseDirectiveSymbolAttribute
 ///  ::= { ".local", ".weak", ... } [ identifier ( , identifier )* ]
@@ -158,7 +175,7 @@ bool ELFAsmParser::ParseDirectiveSymbolAttribute(StringRef Directive, SMLoc) {
     .Default(MCSA_Invalid);
   assert(Attr != MCSA_Invalid && "unexpected symbol attribute directive!");
   if (getLexer().isNot(AsmToken::EndOfStatement)) {
-    for (;;) {
+    while (true) {
       StringRef Name;
 
       if (getParser().parseIdentifier(Name))
@@ -230,8 +247,7 @@ bool ELFAsmParser::ParseSectionName(StringRef &SectionName) {
     return false;
   }
 
-  for (;;) {
-    
+  while (true) {
     SMLoc PrevLoc = getLexer().getLoc();
     if (getLexer().is(AsmToken::Comma) ||
       getLexer().is(AsmToken::EndOfStatement))
@@ -282,6 +298,9 @@ static unsigned parseSectionFlags(StringRef flagsStr, bool *UseLastGroup) {
     case 'w':
       flags |= ELF::SHF_WRITE;
       break;
+    case 'o':
+      flags |= ELF::SHF_LINK_ORDER;
+      break;
     case 'M':
       flags |= ELF::SHF_MERGE;
       break;
@@ -366,6 +385,97 @@ bool ELFAsmParser::ParseDirectiveSection(StringRef, SMLoc loc) {
   return ParseSectionArguments(/*IsPush=*/false, loc);
 }
 
+bool ELFAsmParser::maybeParseSectionType(StringRef &TypeName) {
+  MCAsmLexer &L = getLexer();
+  if (L.isNot(AsmToken::Comma))
+    return false;
+  Lex();
+  if (L.isNot(AsmToken::At) && L.isNot(AsmToken::Percent) &&
+      L.isNot(AsmToken::String)) {
+    if (L.getAllowAtInIdentifier())
+      return TokError("expected '@<type>', '%<type>' or \"<type>\"");
+    else
+      return TokError("expected '%<type>' or \"<type>\"");
+  }
+  if (!L.is(AsmToken::String))
+    Lex();
+  if (L.is(AsmToken::Integer)) {
+    TypeName = getTok().getString();
+    Lex();
+  } else if (getParser().parseIdentifier(TypeName))
+    return TokError("expected identifier in directive");
+  return false;
+}
+
+bool ELFAsmParser::parseMergeSize(int64_t &Size) {
+  if (getLexer().isNot(AsmToken::Comma))
+    return TokError("expected the entry size");
+  Lex();
+  if (getParser().parseAbsoluteExpression(Size))
+    return true;
+  if (Size <= 0)
+    return TokError("entry size must be positive");
+  return false;
+}
+
+bool ELFAsmParser::parseGroup(StringRef &GroupName) {
+  MCAsmLexer &L = getLexer();
+  if (L.isNot(AsmToken::Comma))
+    return TokError("expected group name");
+  Lex();
+  if (getParser().parseIdentifier(GroupName))
+    return true;
+  if (L.is(AsmToken::Comma)) {
+    Lex();
+    StringRef Linkage;
+    if (getParser().parseIdentifier(Linkage))
+      return true;
+    if (Linkage != "comdat")
+      return TokError("Linkage must be 'comdat'");
+  }
+  return false;
+}
+
+bool ELFAsmParser::parseMetadataSym(MCSymbolELF *&Associated) {
+  MCAsmLexer &L = getLexer();
+  if (L.isNot(AsmToken::Comma))
+    return TokError("expected metadata symbol");
+  Lex();
+  StringRef Name;
+  if (getParser().parseIdentifier(Name))
+    return true;
+  Associated = dyn_cast_or_null<MCSymbolELF>(getContext().lookupSymbol(Name));
+  if (!Associated || !Associated->isInSection())
+    return TokError("symbol is not in a section: " + Name);
+  return false;
+}
+
+bool ELFAsmParser::maybeParseUniqueID(int64_t &UniqueID) {
+  MCAsmLexer &L = getLexer();
+  if (L.isNot(AsmToken::Comma))
+    return false;
+  Lex();
+  StringRef UniqueStr;
+  if (getParser().parseIdentifier(UniqueStr))
+    return TokError("expected identifier in directive");
+  if (UniqueStr != "unique")
+    return TokError("expected 'unique'");
+  if (L.isNot(AsmToken::Comma))
+    return TokError("expected commma");
+  Lex();
+  if (getParser().parseAbsoluteExpression(UniqueID))
+    return true;
+  if (UniqueID < 0)
+    return TokError("unique id must be positive");
+  if (!isUInt<32>(UniqueID) || UniqueID == ~0U)
+    return TokError("unique id is too large");
+  return false;
+}
+
+static bool hasPrefix(StringRef SectionName, StringRef Prefix) {
+  return SectionName.startswith(Prefix) || SectionName == Prefix.drop_back();
+}
+
 bool ELFAsmParser::ParseSectionArguments(bool IsPush, SMLoc loc) {
   StringRef SectionName;
 
@@ -379,14 +489,24 @@ bool ELFAsmParser::ParseSectionArguments(bool IsPush, SMLoc loc) {
   const MCExpr *Subsection = nullptr;
   bool UseLastGroup = false;
   StringRef UniqueStr;
+  MCSymbolELF *Associated = nullptr;
   int64_t UniqueID = ~0;
 
   // Set the defaults first.
-  if (SectionName == ".fini" || SectionName == ".init" ||
-      SectionName == ".rodata")
+  if (hasPrefix(SectionName, ".rodata.") || SectionName == ".rodata1")
     Flags |= ELF::SHF_ALLOC;
-  if (SectionName == ".fini" || SectionName == ".init")
-    Flags |= ELF::SHF_EXECINSTR;
+  if (SectionName == ".fini" || SectionName == ".init" ||
+      hasPrefix(SectionName, ".text."))
+    Flags |= ELF::SHF_ALLOC | ELF::SHF_EXECINSTR;
+  if (hasPrefix(SectionName, ".data.") || SectionName == ".data1" ||
+      hasPrefix(SectionName, ".bss.") ||
+      hasPrefix(SectionName, ".init_array.") ||
+      hasPrefix(SectionName, ".fini_array.") ||
+      hasPrefix(SectionName, ".preinit_array."))
+    Flags |= ELF::SHF_ALLOC | ELF::SHF_WRITE;
+  if (hasPrefix(SectionName, ".tdata.") ||
+      hasPrefix(SectionName, ".tbss."))
+    Flags |= ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_TLS;
 
   if (getLexer().is(AsmToken::Comma)) {
     Lex();
@@ -422,65 +542,30 @@ bool ELFAsmParser::ParseSectionArguments(bool IsPush, SMLoc loc) {
       return TokError("Section cannot specifiy a group name while also acting "
                       "as a member of the last group");
 
-    if (getLexer().isNot(AsmToken::Comma)) {
+    if (maybeParseSectionType(TypeName))
+      return true;
+
+    MCAsmLexer &L = getLexer();
+    if (TypeName.empty()) {
       if (Mergeable)
         return TokError("Mergeable section must specify the type");
       if (Group)
         return TokError("Group section must specify the type");
-    } else {
-      Lex();
-      if (getLexer().is(AsmToken::At) || getLexer().is(AsmToken::Percent) ||
-          getLexer().is(AsmToken::String)) {
-        if (!getLexer().is(AsmToken::String))
-          Lex();
-      } else
-        return TokError("expected '@<type>', '%<type>' or \"<type>\"");
-
-      if (getParser().parseIdentifier(TypeName))
-        return TokError("expected identifier in directive");
-
-      if (Mergeable) {
-        if (getLexer().isNot(AsmToken::Comma))
-          return TokError("expected the entry size");
-        Lex();
-        if (getParser().parseAbsoluteExpression(Size))
-          return true;
-        if (Size <= 0)
-          return TokError("entry size must be positive");
-      }
-
-      if (Group) {
-        if (getLexer().isNot(AsmToken::Comma))
-          return TokError("expected group name");
-        Lex();
-        if (getParser().parseIdentifier(GroupName))
-          return true;
-        if (getLexer().is(AsmToken::Comma)) {
-          Lex();
-          StringRef Linkage;
-          if (getParser().parseIdentifier(Linkage))
-            return true;
-          if (Linkage != "comdat")
-            return TokError("Linkage must be 'comdat'");
-        }
-      }
-      if (getLexer().is(AsmToken::Comma)) {
-        Lex();
-        if (getParser().parseIdentifier(UniqueStr))
-          return TokError("expected identifier in directive");
-        if (UniqueStr != "unique")
-          return TokError("expected 'unique'");
-        if (getLexer().isNot(AsmToken::Comma))
-          return TokError("expected commma");
-        Lex();
-        if (getParser().parseAbsoluteExpression(UniqueID))
-          return true;
-        if (UniqueID < 0)
-          return TokError("unique id must be positive");
-        if (!isUInt<32>(UniqueID) || UniqueID == ~0U)
-          return TokError("unique id is too large");
-      }
+      if (L.isNot(AsmToken::EndOfStatement))
+        return TokError("unexpected token in directive");
     }
+
+    if (Mergeable)
+      if (parseMergeSize(Size))
+        return true;
+    if (Group)
+      if (parseGroup(GroupName))
+        return true;
+    if (Flags & ELF::SHF_LINK_ORDER)
+      if (parseMetadataSym(Associated))
+        return true;
+    if (maybeParseUniqueID(UniqueID))
+      return true;
   }
 
 EndStmt:
@@ -493,11 +578,15 @@ EndStmt:
   if (TypeName.empty()) {
     if (SectionName.startswith(".note"))
       Type = ELF::SHT_NOTE;
-    else if (SectionName == ".init_array")
+    else if (hasPrefix(SectionName, ".init_array."))
       Type = ELF::SHT_INIT_ARRAY;
-    else if (SectionName == ".fini_array")
+    else if (hasPrefix(SectionName, ".bss."))
+      Type = ELF::SHT_NOBITS;
+    else if (hasPrefix(SectionName, ".tbss."))
+      Type = ELF::SHT_NOBITS;
+    else if (hasPrefix(SectionName, ".fini_array."))
       Type = ELF::SHT_FINI_ARRAY;
-    else if (SectionName == ".preinit_array")
+    else if (hasPrefix(SectionName, ".preinit_array."))
       Type = ELF::SHT_PREINIT_ARRAY;
   } else {
     if (TypeName == "init_array")
@@ -514,7 +603,7 @@ EndStmt:
       Type = ELF::SHT_NOTE;
     else if (TypeName == "unwind")
       Type = ELF::SHT_X86_64_UNWIND;
-    else
+    else if (TypeName.getAsInteger(0, Type))
       return TokError("unknown section type");
   }
 
@@ -528,8 +617,9 @@ EndStmt:
       }
   }
 
-  MCSection *ELFSection = getContext().getELFSection(SectionName, Type, Flags,
-                                                     Size, GroupName, UniqueID);
+  MCSection *ELFSection =
+      getContext().getELFSection(SectionName, Type, Flags, Size, GroupName,
+                                 UniqueID, Associated);
   getStreamer().SwitchSection(ELFSection, Subsection);
 
   if (getContext().getGenDwarfForAssembly()) {
@@ -677,6 +767,7 @@ bool ELFAsmParser::ParseDirectiveSymver(StringRef, SMLoc) {
   const MCExpr *Value = MCSymbolRefExpr::create(Sym, getContext());
 
   getStreamer().EmitAssignment(Alias, Value);
+  getStreamer().emitELFSymverDirective(Alias, Sym);
   return false;
 }
 
@@ -752,4 +843,4 @@ MCAsmParserExtension *createELFAsmParser() {
   return new ELFAsmParser;
 }
 
-}
+} // end namespace llvm
diff --git a/lib/MC/MCParser/MCAsmLexer.cpp b/lib/MC/MCParser/MCAsmLexer.cpp
index 63c0daba09a0..f8fe78aece0c 100644
--- a/lib/MC/MCParser/MCAsmLexer.cpp
+++ b/lib/MC/MCParser/MCAsmLexer.cpp
@@ -1,4 +1,4 @@
-//===-- MCAsmLexer.cpp - Abstract Asm Lexer Interface ---------------------===//
+//===- MCAsmLexer.cpp - Abstract Asm Lexer Interface ----------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,19 +7,17 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/StringRef.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
-#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/SMLoc.h"
 
 using namespace llvm;
 
-MCAsmLexer::MCAsmLexer()
-    : TokStart(nullptr), SkipSpace(true), IsAtStartOfStatement(true),
-      CommentConsumer(nullptr) {
+MCAsmLexer::MCAsmLexer() {
   CurTok.emplace_back(AsmToken::Space, StringRef());
 }
 
-MCAsmLexer::~MCAsmLexer() {
-}
+MCAsmLexer::~MCAsmLexer() = default;
 
 SMLoc MCAsmLexer::getLoc() const {
   return SMLoc::getFromPointer(TokStart);
diff --git a/lib/MC/MCParser/MCAsmParser.cpp b/lib/MC/MCParser/MCAsmParser.cpp
index 98f4daf972d6..27b37f3e2dfb 100644
--- a/lib/MC/MCParser/MCAsmParser.cpp
+++ b/lib/MC/MCParser/MCAsmParser.cpp
@@ -7,22 +7,22 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCParser/MCAsmParser.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
+#include "llvm/MC/MCParser/MCAsmParser.h"
 #include "llvm/MC/MCParser/MCParsedAsmOperand.h"
 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
 #include "llvm/Support/Debug.h"
-#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/SMLoc.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
+
 using namespace llvm;
 
-MCAsmParser::MCAsmParser()
-    : TargetParser(nullptr), ShowParsedOperands(0), HadError(false),
-      PendingErrors() {}
+MCAsmParser::MCAsmParser() : ShowParsedOperands(0) {}
 
-MCAsmParser::~MCAsmParser() {
-}
+MCAsmParser::~MCAsmParser() = default;
 
 void MCAsmParser::setTargetParser(MCTargetAsmParser &P) {
   assert(!TargetParser && "Target parser is already initialized!");
@@ -118,10 +118,10 @@ bool MCAsmParser::addErrorSuffix(const Twine &Suffix) {
   return true;
 }
 
-bool MCAsmParser::parseMany(std::function<bool()> parseOne, bool hasComma) {
+bool MCAsmParser::parseMany(function_ref<bool()> parseOne, bool hasComma) {
   if (parseOptionalToken(AsmToken::EndOfStatement))
     return false;
-  while (1) {
+  while (true) {
     if (parseOne())
       return true;
     if (parseOptionalToken(AsmToken::EndOfStatement))
@@ -137,6 +137,9 @@ bool MCAsmParser::parseExpression(const MCExpr *&Res) {
   return parseExpression(Res, L);
 }
 
-LLVM_DUMP_METHOD void MCParsedAsmOperand::dump() const {
+void MCParsedAsmOperand::dump() const {
+  // Cannot completely remove virtual function even in release mode.
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
   dbgs() << "  " << *this;
+#endif
 }
diff --git a/lib/MC/MCParser/MCAsmParserExtension.cpp b/lib/MC/MCParser/MCAsmParserExtension.cpp
index 3f25a14926b6..031f473dc5fe 100644
--- a/lib/MC/MCParser/MCAsmParserExtension.cpp
+++ b/lib/MC/MCParser/MCAsmParserExtension.cpp
@@ -1,4 +1,4 @@
-//===-- MCAsmParserExtension.cpp - Asm Parser Hooks -----------------------===//
+//===- MCAsmParserExtension.cpp - Asm Parser Hooks ------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -8,14 +8,12 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCParser/MCAsmParserExtension.h"
+
 using namespace llvm;
 
-MCAsmParserExtension::MCAsmParserExtension() :
-  BracketExpressionsSupported(false) {
-}
+MCAsmParserExtension::MCAsmParserExtension() = default;
 
-MCAsmParserExtension::~MCAsmParserExtension() {
-}
+MCAsmParserExtension::~MCAsmParserExtension() = default;
 
 void MCAsmParserExtension::Initialize(MCAsmParser &Parser) {
   this->Parser = &Parser;
diff --git a/lib/MC/MCParser/MCTargetAsmParser.cpp b/lib/MC/MCParser/MCTargetAsmParser.cpp
index 14a22c6b8a2f..5f821443bb96 100644
--- a/lib/MC/MCParser/MCTargetAsmParser.cpp
+++ b/lib/MC/MCParser/MCTargetAsmParser.cpp
@@ -1,4 +1,4 @@
-//===-- MCTargetAsmParser.cpp - Target Assembly Parser ---------------------==//
+//===-- MCTargetAsmParser.cpp - Target Assembly Parser --------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,19 +7,16 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCParser/MCTargetAsmParser.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCParser/MCTargetAsmParser.h"
+
 using namespace llvm;
 
 MCTargetAsmParser::MCTargetAsmParser(MCTargetOptions const &MCOptions,
                                      const MCSubtargetInfo &STI)
-  : AvailableFeatures(0), ParsingInlineAsm(false), MCOptions(MCOptions),
-    STI(&STI)
-{
-}
+  : MCOptions(MCOptions), STI(&STI) {}
 
-MCTargetAsmParser::~MCTargetAsmParser() {
-}
+MCTargetAsmParser::~MCTargetAsmParser() = default;
 
 MCSubtargetInfo &MCTargetAsmParser::copySTI() {
   MCSubtargetInfo &STICopy = getContext().getSubtargetCopy(getSTI());
diff --git a/lib/MC/MCRegisterInfo.cpp b/lib/MC/MCRegisterInfo.cpp
index ea117f3caa85..a75100a4876b 100644
--- a/lib/MC/MCRegisterInfo.cpp
+++ b/lib/MC/MCRegisterInfo.cpp
@@ -1,4 +1,4 @@
-//=== MC/MCRegisterInfo.cpp - Target Register Description -------*- C++ -*-===//
+//===- MC/MCRegisterInfo.cpp - Target Register Description ----------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -11,9 +11,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/MC/MCRegisterInfo.h"
-#include "llvm/Support/Format.h"
-#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/ErrorHandling.h"
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
 
 using namespace llvm;
 
diff --git a/lib/MC/MCSection.cpp b/lib/MC/MCSection.cpp
index 9064cdf2f319..7986c0122043 100644
--- a/lib/MC/MCSection.cpp
+++ b/lib/MC/MCSection.cpp
@@ -7,17 +7,18 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCSection.h"
-#include "llvm/MC/MCAssembler.h"
-#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCFragment.h"
+#include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSymbol.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
-using namespace llvm;
+#include <algorithm>
+#include <utility>
 
-//===----------------------------------------------------------------------===//
-// MCSection
-//===----------------------------------------------------------------------===//
+using namespace llvm;
 
 MCSection::MCSection(SectionVariant V, SectionKind K, MCSymbol *Begin)
     : Begin(Begin), BundleGroupBeforeFirstInst(false), HasInstructions(false),
@@ -31,8 +32,7 @@ MCSymbol *MCSection::getEndSymbol(MCContext &Ctx) {
 
 bool MCSection::hasEnded() const { return End && End->isInSection(); }
 
-MCSection::~MCSection() {
-}
+MCSection::~MCSection() = default;
 
 void MCSection::setBundleLockState(BundleLockStateType NewState) {
   if (NewState == NotBundleLocked) {
@@ -85,8 +85,9 @@ MCSection::getSubsectionInsertionPoint(unsigned Subsection) {
   return IP;
 }
 
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MCSection::dump() {
-  raw_ostream &OS = llvm::errs();
+  raw_ostream &OS = errs();
 
   OS << "<MCSection";
   OS << " Fragments:[\n      ";
@@ -97,3 +98,4 @@ LLVM_DUMP_METHOD void MCSection::dump() {
   }
   OS << "]>";
 }
+#endif
diff --git a/lib/MC/MCSectionCOFF.cpp b/lib/MC/MCSectionCOFF.cpp
index f2dd47d81b7e..f0709cbc2515 100644
--- a/lib/MC/MCSectionCOFF.cpp
+++ b/lib/MC/MCSectionCOFF.cpp
@@ -8,14 +8,14 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/MC/MCSectionCOFF.h"
-#include "llvm/MC/MCAsmInfo.h"
-#include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/COFF.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
+
 using namespace llvm;
 
-MCSectionCOFF::~MCSectionCOFF() {} // anchor.
+MCSectionCOFF::~MCSectionCOFF() = default; // anchor.
 
 // ShouldOmitSectionDirective - Decides whether a '.section' directive
 // should be printed before the section name
@@ -37,10 +37,9 @@ void MCSectionCOFF::setSelection(int Selection) const {
   Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
 }
 
-void MCSectionCOFF::PrintSwitchToSection(const MCAsmInfo &MAI,
+void MCSectionCOFF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
                                          raw_ostream &OS,
                                          const MCExpr *Subsection) const {
-
   // standard sections don't require the '.section'
   if (ShouldOmitSectionDirective(SectionName, MAI)) {
     OS << '\t' << getSectionName() << '\n';
@@ -94,7 +93,7 @@ void MCSectionCOFF::PrintSwitchToSection(const MCAsmInfo &MAI,
         OS << "newest,";
         break;
       default:
-        assert (0 && "unsupported COFF selection type");
+        assert(false && "unsupported COFF selection type");
         break;
     }
     assert(COMDATSymbol);
diff --git a/lib/MC/MCSectionELF.cpp b/lib/MC/MCSectionELF.cpp
index 587b28f71b7d..78fe01cca24a 100644
--- a/lib/MC/MCSectionELF.cpp
+++ b/lib/MC/MCSectionELF.cpp
@@ -7,23 +7,23 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCSectionELF.h"
+#include "llvm/ADT/Triple.h"
 #include "llvm/MC/MCAsmInfo.h"
-#include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
-#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCSectionELF.h"
 #include "llvm/Support/ELF.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
 
 using namespace llvm;
 
-MCSectionELF::~MCSectionELF() {} // anchor.
+MCSectionELF::~MCSectionELF() = default; // anchor.
 
 // Decides whether a '.section' directive
 // should be printed before the section name.
 bool MCSectionELF::ShouldOmitSectionDirective(StringRef Name,
                                               const MCAsmInfo &MAI) const {
-
   if (isUnique())
     return false;
 
@@ -53,10 +53,9 @@ static void printName(raw_ostream &OS, StringRef Name) {
   OS << '"';
 }
 
-void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI,
+void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
                                         raw_ostream &OS,
                                         const MCExpr *Subsection) const {
-
   if (ShouldOmitSectionDirective(SectionName, MAI)) {
     OS << '\t' << getSectionName();
     if (Subsection) {
@@ -104,14 +103,21 @@ void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI,
     OS << 'S';
   if (Flags & ELF::SHF_TLS)
     OS << 'T';
+  if (Flags & ELF::SHF_LINK_ORDER)
+    OS << 'o';
 
   // If there are target-specific flags, print them.
-  if (Flags & ELF::XCORE_SHF_CP_SECTION)
-    OS << 'c';
-  if (Flags & ELF::XCORE_SHF_DP_SECTION)
-    OS << 'd';
-  if (Flags & ELF::SHF_ARM_PURECODE)
-    OS << 'y';
+  Triple::ArchType Arch = T.getArch();
+  if (Arch == Triple::xcore) {
+    if (Flags & ELF::XCORE_SHF_CP_SECTION)
+      OS << 'c';
+    if (Flags & ELF::XCORE_SHF_DP_SECTION)
+      OS << 'd';
+  } else if (Arch == Triple::arm || Arch == Triple::armeb ||
+             Arch == Triple::thumb || Arch == Triple::thumbeb) {
+    if (Flags & ELF::SHF_ARM_PURECODE)
+      OS << 'y';
+  }
 
   OS << '"';
 
@@ -137,6 +143,13 @@ void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI,
     OS << "progbits";
   else if (Type == ELF::SHT_X86_64_UNWIND)
     OS << "unwind";
+  else if (Type == ELF::SHT_MIPS_DWARF)
+    // Print hex value of the flag while we do not have
+    // any standard symbolic representation of the flag.
+    OS << "0x7000001e";
+  else
+    report_fatal_error("unsupported type 0x" + Twine::utohexstr(Type) +
+                       " for section " + getSectionName());
 
   if (EntrySize) {
     assert(Flags & ELF::SHF_MERGE);
@@ -149,6 +162,12 @@ void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI,
     OS << ",comdat";
   }
 
+  if (Flags & ELF::SHF_LINK_ORDER) {
+    assert(AssociatedSymbol);
+    OS << ",";
+    printName(OS, AssociatedSymbol->getName());
+  }
+
   if (isUnique())
     OS << ",unique," << UniqueID;
 
diff --git a/lib/MC/MCSectionMachO.cpp b/lib/MC/MCSectionMachO.cpp
index c2a772fdbdac..f40237231a2f 100644
--- a/lib/MC/MCSectionMachO.cpp
+++ b/lib/MC/MCSectionMachO.cpp
@@ -16,45 +16,57 @@ using namespace llvm;
 /// SectionTypeDescriptors - These are strings that describe the various section
 /// types.  This *must* be kept in order with and stay synchronized with the
 /// section type list.
-static const struct {
-  StringRef AssemblerName, EnumName;
-} SectionTypeDescriptors[MachO::LAST_KNOWN_SECTION_TYPE+1] = {
-  { "regular",                  "S_REGULAR" },                    // 0x00
-  { StringRef(),                "S_ZEROFILL" },                   // 0x01
-  { "cstring_literals",         "S_CSTRING_LITERALS" },           // 0x02
-  { "4byte_literals",           "S_4BYTE_LITERALS" },             // 0x03
-  { "8byte_literals",           "S_8BYTE_LITERALS" },             // 0x04
-  { "literal_pointers",         "S_LITERAL_POINTERS" },           // 0x05
-  { "non_lazy_symbol_pointers", "S_NON_LAZY_SYMBOL_POINTERS" },   // 0x06
-  { "lazy_symbol_pointers",     "S_LAZY_SYMBOL_POINTERS" },       // 0x07
-  { "symbol_stubs",             "S_SYMBOL_STUBS" },               // 0x08
-  { "mod_init_funcs",           "S_MOD_INIT_FUNC_POINTERS" },     // 0x09
-  { "mod_term_funcs",           "S_MOD_TERM_FUNC_POINTERS" },     // 0x0A
-  { "coalesced",                "S_COALESCED" },                  // 0x0B
-  { StringRef(), /*FIXME??*/    "S_GB_ZEROFILL" },                // 0x0C
-  { "interposing",              "S_INTERPOSING" },                // 0x0D
-  { "16byte_literals",          "S_16BYTE_LITERALS" },            // 0x0E
-  { StringRef(), /*FIXME??*/    "S_DTRACE_DOF" },                 // 0x0F
-  { StringRef(), /*FIXME??*/    "S_LAZY_DYLIB_SYMBOL_POINTERS" }, // 0x10
-  { "thread_local_regular",     "S_THREAD_LOCAL_REGULAR" },       // 0x11
-  { "thread_local_zerofill",    "S_THREAD_LOCAL_ZEROFILL" },      // 0x12
-  { "thread_local_variables",   "S_THREAD_LOCAL_VARIABLES" },     // 0x13
-  { "thread_local_variable_pointers",
-    "S_THREAD_LOCAL_VARIABLE_POINTERS" },                         // 0x14
-  { "thread_local_init_function_pointers",
-    "S_THREAD_LOCAL_INIT_FUNCTION_POINTERS"},                     // 0x15
+static constexpr struct {
+  StringLiteral AssemblerName, EnumName;
+} SectionTypeDescriptors[MachO::LAST_KNOWN_SECTION_TYPE + 1] = {
+    {StringLiteral("regular"), StringLiteral("S_REGULAR")}, // 0x00
+    {StringLiteral(""), StringLiteral("S_ZEROFILL")},       // 0x01
+    {StringLiteral("cstring_literals"),
+     StringLiteral("S_CSTRING_LITERALS")}, // 0x02
+    {StringLiteral("4byte_literals"),
+     StringLiteral("S_4BYTE_LITERALS")}, // 0x03
+    {StringLiteral("8byte_literals"),
+     StringLiteral("S_8BYTE_LITERALS")}, // 0x04
+    {StringLiteral("literal_pointers"),
+     StringLiteral("S_LITERAL_POINTERS")}, // 0x05
+    {StringLiteral("non_lazy_symbol_pointers"),
+     StringLiteral("S_NON_LAZY_SYMBOL_POINTERS")}, // 0x06
+    {StringLiteral("lazy_symbol_pointers"),
+     StringLiteral("S_LAZY_SYMBOL_POINTERS")},                        // 0x07
+    {StringLiteral("symbol_stubs"), StringLiteral("S_SYMBOL_STUBS")}, // 0x08
+    {StringLiteral("mod_init_funcs"),
+     StringLiteral("S_MOD_INIT_FUNC_POINTERS")}, // 0x09
+    {StringLiteral("mod_term_funcs"),
+     StringLiteral("S_MOD_TERM_FUNC_POINTERS")},                     // 0x0A
+    {StringLiteral("coalesced"), StringLiteral("S_COALESCED")},      // 0x0B
+    {StringLiteral("") /*FIXME??*/, StringLiteral("S_GB_ZEROFILL")}, // 0x0C
+    {StringLiteral("interposing"), StringLiteral("S_INTERPOSING")},  // 0x0D
+    {StringLiteral("16byte_literals"),
+     StringLiteral("S_16BYTE_LITERALS")},                           // 0x0E
+    {StringLiteral("") /*FIXME??*/, StringLiteral("S_DTRACE_DOF")}, // 0x0F
+    {StringLiteral("") /*FIXME??*/,
+     StringLiteral("S_LAZY_DYLIB_SYMBOL_POINTERS")}, // 0x10
+    {StringLiteral("thread_local_regular"),
+     StringLiteral("S_THREAD_LOCAL_REGULAR")}, // 0x11
+    {StringLiteral("thread_local_zerofill"),
+     StringLiteral("S_THREAD_LOCAL_ZEROFILL")}, // 0x12
+    {StringLiteral("thread_local_variables"),
+     StringLiteral("S_THREAD_LOCAL_VARIABLES")}, // 0x13
+    {StringLiteral("thread_local_variable_pointers"),
+     StringLiteral("S_THREAD_LOCAL_VARIABLE_POINTERS")}, // 0x14
+    {StringLiteral("thread_local_init_function_pointers"),
+     StringLiteral("S_THREAD_LOCAL_INIT_FUNCTION_POINTERS")}, // 0x15
 };
 
-
 /// SectionAttrDescriptors - This is an array of descriptors for section
 /// attributes.  Unlike the SectionTypeDescriptors, this is not directly indexed
 /// by attribute, instead it is searched.
-static const struct {
+static constexpr struct {
   unsigned AttrFlag;
-  StringRef AssemblerName, EnumName;
+  StringLiteral AssemblerName, EnumName;
 } SectionAttrDescriptors[] = {
 #define ENTRY(ASMNAME, ENUM) \
-  { MachO::ENUM, ASMNAME, #ENUM },
+  { MachO::ENUM, StringLiteral(ASMNAME), StringLiteral(#ENUM) },
 ENTRY("pure_instructions",   S_ATTR_PURE_INSTRUCTIONS)
 ENTRY("no_toc",              S_ATTR_NO_TOC)
 ENTRY("strip_static_syms",   S_ATTR_STRIP_STATIC_SYMS)
@@ -62,11 +74,11 @@ ENTRY("no_dead_strip",       S_ATTR_NO_DEAD_STRIP)
 ENTRY("live_support",        S_ATTR_LIVE_SUPPORT)
 ENTRY("self_modifying_code", S_ATTR_SELF_MODIFYING_CODE)
 ENTRY("debug",               S_ATTR_DEBUG)
-ENTRY(StringRef() /*FIXME*/, S_ATTR_SOME_INSTRUCTIONS)
-ENTRY(StringRef() /*FIXME*/, S_ATTR_EXT_RELOC)
-ENTRY(StringRef() /*FIXME*/, S_ATTR_LOC_RELOC)
+ENTRY("" /*FIXME*/,          S_ATTR_SOME_INSTRUCTIONS)
+ENTRY("" /*FIXME*/,          S_ATTR_EXT_RELOC)
+ENTRY("" /*FIXME*/,          S_ATTR_LOC_RELOC)
 #undef ENTRY
-  { 0, "none", StringRef() }, // used if section has no attributes but has a stub size
+  { 0, StringLiteral("none"), StringLiteral("") }, // used if section has no attributes but has a stub size
 };
 
 MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section,
@@ -89,7 +101,7 @@ MCSectionMachO::MCSectionMachO(StringRef Segment, StringRef Section,
   }
 }
 
-void MCSectionMachO::PrintSwitchToSection(const MCAsmInfo &MAI,
+void MCSectionMachO::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
                                           raw_ostream &OS,
                                           const MCExpr *Subsection) const {
   OS << "\t.section\t" << getSegmentName() << ',' << getSectionName();
diff --git a/lib/MC/MCSectionWasm.cpp b/lib/MC/MCSectionWasm.cpp
new file mode 100644
index 000000000000..c61f28e129f5
--- /dev/null
+++ b/lib/MC/MCSectionWasm.cpp
@@ -0,0 +1,97 @@
+//===- lib/MC/MCSectionWasm.cpp - Wasm Code Section Representation --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCSectionWasm.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+MCSectionWasm::~MCSectionWasm() {} // anchor.
+
+// Decides whether a '.section' directive
+// should be printed before the section name.
+bool MCSectionWasm::ShouldOmitSectionDirective(StringRef Name,
+                                               const MCAsmInfo &MAI) const {
+  return MAI.shouldOmitSectionDirective(Name);
+}
+
+static void printName(raw_ostream &OS, StringRef Name) {
+  if (Name.find_first_not_of("0123456789_."
+                             "abcdefghijklmnopqrstuvwxyz"
+                             "ABCDEFGHIJKLMNOPQRSTUVWXYZ") == Name.npos) {
+    OS << Name;
+    return;
+  }
+  OS << '"';
+  for (const char *B = Name.begin(), *E = Name.end(); B < E; ++B) {
+    if (*B == '"') // Unquoted "
+      OS << "\\\"";
+    else if (*B != '\\') // Neither " or backslash
+      OS << *B;
+    else if (B + 1 == E) // Trailing backslash
+      OS << "\\\\";
+    else {
+      OS << B[0] << B[1]; // Quoted character
+      ++B;
+    }
+  }
+  OS << '"';
+}
+
+void MCSectionWasm::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
+                                         raw_ostream &OS,
+                                         const MCExpr *Subsection) const {
+
+  if (ShouldOmitSectionDirective(SectionName, MAI)) {
+    OS << '\t' << getSectionName();
+    if (Subsection) {
+      OS << '\t';
+      Subsection->print(OS, &MAI);
+    }
+    OS << '\n';
+    return;
+  }
+
+  OS << "\t.section\t";
+  printName(OS, getSectionName());
+  OS << ",\"";
+
+  // TODO: Print section flags.
+
+  OS << '"';
+
+  OS << ',';
+
+  // If comment string is '@', e.g. as on ARM - use '%' instead
+  if (MAI.getCommentString()[0] == '@')
+    OS << '%';
+  else
+    OS << '@';
+
+  // TODO: Print section type.
+
+  if (isUnique())
+    OS << ",unique," << UniqueID;
+
+  OS << '\n';
+
+  if (Subsection) {
+    OS << "\t.subsection\t";
+    Subsection->print(OS, &MAI);
+    OS << '\n';
+  }
+}
+
+bool MCSectionWasm::UseCodeAlign() const { return false; }
+
+bool MCSectionWasm::isVirtualSection() const { return false; }
diff --git a/lib/MC/MCStreamer.cpp b/lib/MC/MCStreamer.cpp
index fb28f856f671..c9a6f12b6a58 100644
--- a/lib/MC/MCStreamer.cpp
+++ b/lib/MC/MCStreamer.cpp
@@ -7,36 +7,44 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCStreamer.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCCodeView.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCInstPrinter.h"
 #include "llvm/MC/MCObjectFileInfo.h"
-#include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionCOFF.h"
+#include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCWin64EH.h"
+#include "llvm/MC/MCWinEH.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/COFF.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/LEB128.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstdlib>
-using namespace llvm;
+#include <cassert>
+#include <cstdint>
+#include <utility>
 
-// Pin the vtables to this file.
-MCTargetStreamer::~MCTargetStreamer() {}
+using namespace llvm;
 
 MCTargetStreamer::MCTargetStreamer(MCStreamer &S) : Streamer(S) {
   S.setTargetStreamer(this);
 }
 
+// Pin the vtables to this file.
+MCTargetStreamer::~MCTargetStreamer() = default;
+
 void MCTargetStreamer::emitLabel(MCSymbol *Symbol) {}
 
 void MCTargetStreamer::finish() {}
@@ -290,10 +298,17 @@ void MCStreamer::AssignFragment(MCSymbol *Symbol, MCFragment *Fragment) {
   SymbolOrdering[Symbol] = 1 + SymbolOrdering.size();
 }
 
-void MCStreamer::EmitLabel(MCSymbol *Symbol) {
+void MCStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
+  Symbol->redefineIfPossible();
+
+  if (!Symbol->isUndefined() || Symbol->isVariable())
+    return getContext().reportError(Loc, "invalid symbol redefinition");
+
   assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
   assert(getCurrentSectionOnly() && "Cannot emit before setting section!");
   assert(!Symbol->getFragment() && "Unexpected fragment on symbol data!");
+  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
+
   Symbol->setFragment(&getCurrentSectionOnly()->getDummyFragment());
 
   MCTargetStreamer *TS = getTargetStreamer();
@@ -666,7 +681,7 @@ void MCStreamer::EmitWinCFISaveXMM(unsigned Register, unsigned Offset) {
 
 void MCStreamer::EmitWinCFIPushFrame(bool Code) {
   EnsureValidWinFrameInfo();
-  if (CurrentWinFrameInfo->Instructions.size() > 0)
+  if (!CurrentWinFrameInfo->Instructions.empty())
     report_fatal_error("If present, PushMachFrame must be the first UOP");
 
   MCSymbol *Label = EmitCFILabel();
@@ -762,8 +777,8 @@ void MCStreamer::visitUsedExpr(const MCExpr &Expr) {
   }
 }
 
-void MCStreamer::EmitInstruction(const MCInst &Inst,
-                                 const MCSubtargetInfo &STI) {
+void MCStreamer::EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
+                                 bool) {
   // Scan for values.
   for (unsigned i = Inst.getNumOperands(); i--;)
     if (Inst.getOperand(i).isExpr())
@@ -792,12 +807,22 @@ void MCStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi, const MCSymbol *Lo,
 void MCStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {}
 void MCStreamer::EmitThumbFunc(MCSymbol *Func) {}
 void MCStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {}
-void MCStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {}
-void MCStreamer::EndCOFFSymbolDef() {}
+void MCStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
+  llvm_unreachable("this directive only supported on COFF targets");
+}
+void MCStreamer::EndCOFFSymbolDef() {
+  llvm_unreachable("this directive only supported on COFF targets");
+}
 void MCStreamer::EmitFileDirective(StringRef Filename) {}
-void MCStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {}
-void MCStreamer::EmitCOFFSymbolType(int Type) {}
+void MCStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
+  llvm_unreachable("this directive only supported on COFF targets");
+}
+void MCStreamer::EmitCOFFSymbolType(int Type) {
+  llvm_unreachable("this directive only supported on COFF targets");
+}
 void MCStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {}
+void MCStreamer::emitELFSymverDirective(MCSymbol *Alias,
+                                        const MCSymbol *Aliasee) {}
 void MCStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                        unsigned ByteAlignment) {}
 void MCStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
diff --git a/lib/MC/MCSubtargetInfo.cpp b/lib/MC/MCSubtargetInfo.cpp
index 1b592504b1e4..777b4e3d6b67 100644
--- a/lib/MC/MCSubtargetInfo.cpp
+++ b/lib/MC/MCSubtargetInfo.cpp
@@ -1,4 +1,4 @@
-//===-- MCSubtargetInfo.cpp - Subtarget Information -----------------------===//
+//===- MCSubtargetInfo.cpp - Subtarget Information ------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,13 +7,16 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
-#include "llvm/ADT/Triple.h"
 #include "llvm/MC/MCInstrItineraries.h"
+#include "llvm/MC/MCSchedule.h"
+#include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/MC/SubtargetFeature.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
+#include <cassert>
+#include <cstring>
 
 using namespace llvm;
 
diff --git a/lib/MC/MCSymbol.cpp b/lib/MC/MCSymbol.cpp
index 20d985df7ea0..cb262542b89f 100644
--- a/lib/MC/MCSymbol.cpp
+++ b/lib/MC/MCSymbol.cpp
@@ -7,13 +7,19 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCSymbol.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCFragment.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstddef>
+
 using namespace llvm;
 
 // Only the address of this fragment is ever actually used.
@@ -75,4 +81,8 @@ void MCSymbol::print(raw_ostream &OS, const MCAsmInfo *MAI) const {
   OS << '"';
 }
 
-LLVM_DUMP_METHOD void MCSymbol::dump() const { dbgs() << *this; }
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void MCSymbol::dump() const {
+  dbgs() << *this;
+}
+#endif
diff --git a/lib/MC/MCSymbolELF.cpp b/lib/MC/MCSymbolELF.cpp
index ec7ef447ff89..ffa8260d4342 100644
--- a/lib/MC/MCSymbolELF.cpp
+++ b/lib/MC/MCSymbolELF.cpp
@@ -42,6 +42,8 @@ enum {
 
 void MCSymbolELF::setBinding(unsigned Binding) const {
   setIsBindingSet();
+  if (getType() == ELF::STT_SECTION && Binding != ELF::STB_LOCAL)
+    setType(ELF::STT_NOTYPE);
   unsigned Val;
   switch (Binding) {
   default:
@@ -93,6 +95,8 @@ unsigned MCSymbolELF::getBinding() const {
 
 void MCSymbolELF::setType(unsigned Type) const {
   unsigned Val;
+  if (Type == ELF::STT_SECTION && getBinding() != ELF::STB_LOCAL)
+    return;
   switch (Type) {
   default:
     llvm_unreachable("Unsupported Binding");
diff --git a/lib/MC/MCTargetOptions.cpp b/lib/MC/MCTargetOptions.cpp
index 419210537eea..5d666b67fddb 100644
--- a/lib/MC/MCTargetOptions.cpp
+++ b/lib/MC/MCTargetOptions.cpp
@@ -1,4 +1,4 @@
-//===- lib/MC/MCTargetOptions.cpp - MC Target Options --------------------===//
+//===- lib/MC/MCTargetOptions.cpp - MC Target Options ---------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -10,19 +10,16 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/MC/MCTargetOptions.h"
 
-namespace llvm {
+using namespace llvm;
 
 MCTargetOptions::MCTargetOptions()
     : SanitizeAddress(false), MCRelaxAll(false), MCNoExecStack(false),
       MCFatalWarnings(false), MCNoWarn(false), MCNoDeprecatedWarn(false),
-      MCSaveTempLabels(false),
-      MCUseDwarfDirectory(false), MCIncrementalLinkerCompatible(false),
-      MCPIECopyRelocations(false), ShowMCEncoding(false),
-      ShowMCInst(false), AsmVerbose(false),
-      PreserveAsmComments(true), DwarfVersion(0), ABIName() {}
+      MCSaveTempLabels(false), MCUseDwarfDirectory(false),
+      MCIncrementalLinkerCompatible(false), MCPIECopyRelocations(false),
+      ShowMCEncoding(false), ShowMCInst(false), AsmVerbose(false),
+      PreserveAsmComments(true) {}
 
 StringRef MCTargetOptions::getABIName() const {
   return ABIName;
 }
-
-} // end namespace llvm
diff --git a/lib/MC/MCValue.cpp b/lib/MC/MCValue.cpp
index c1336d6d1b49..32a6adbf224e 100644
--- a/lib/MC/MCValue.cpp
+++ b/lib/MC/MCValue.cpp
@@ -37,9 +37,11 @@ void MCValue::print(raw_ostream &OS) const {
     OS << " + " << getConstant();
 }
 
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MCValue::dump() const {
   print(dbgs());
 }
+#endif
 
 MCSymbolRefExpr::VariantKind MCValue::getAccessVariant() const {
   const MCSymbolRefExpr *B = getSymB();
diff --git a/lib/MC/MCWasmObjectTargetWriter.cpp b/lib/MC/MCWasmObjectTargetWriter.cpp
new file mode 100644
index 000000000000..a09a17d7a124
--- /dev/null
+++ b/lib/MC/MCWasmObjectTargetWriter.cpp
@@ -0,0 +1,27 @@
+//===-- MCWasmObjectTargetWriter.cpp - Wasm Target Writer Subclass --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/MC/MCWasmObjectWriter.h"
+
+using namespace llvm;
+
+MCWasmObjectTargetWriter::MCWasmObjectTargetWriter(bool Is64Bit_)
+    : Is64Bit(Is64Bit_) {}
+
+bool MCWasmObjectTargetWriter::needsRelocateWithSymbol(const MCSymbol &Sym,
+                                                       unsigned Type) const {
+  return false;
+}
+
+void MCWasmObjectTargetWriter::sortRelocs(
+    const MCAssembler &Asm, std::vector<WasmRelocationEntry> &Relocs) {
+}
diff --git a/lib/MC/MCWasmStreamer.cpp b/lib/MC/MCWasmStreamer.cpp
new file mode 100644
index 000000000000..59b62b8d37c3
--- /dev/null
+++ b/lib/MC/MCWasmStreamer.cpp
@@ -0,0 +1,216 @@
+//===- lib/MC/MCWasmStreamer.cpp - Wasm Object Output ---------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file assembles .s files and emits Wasm .o object files.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCWasmStreamer.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCAsmLayout.h"
+#include "llvm/MC/MCAssembler.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCObjectStreamer.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCSectionWasm.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCSymbolWasm.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+MCWasmStreamer::~MCWasmStreamer() {}
+
+void MCWasmStreamer::mergeFragment(MCDataFragment *DF, MCDataFragment *EF) {
+  flushPendingLabels(DF, DF->getContents().size());
+
+  for (unsigned i = 0, e = EF->getFixups().size(); i != e; ++i) {
+    EF->getFixups()[i].setOffset(EF->getFixups()[i].getOffset() +
+                                 DF->getContents().size());
+    DF->getFixups().push_back(EF->getFixups()[i]);
+  }
+  DF->setHasInstructions(true);
+  DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
+}
+
+void MCWasmStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
+  // Let the target do whatever target specific stuff it needs to do.
+  getAssembler().getBackend().handleAssemblerFlag(Flag);
+
+  // Do any generic stuff we need to do.
+  llvm_unreachable("invalid assembler flag!");
+}
+
+void MCWasmStreamer::ChangeSection(MCSection *Section,
+                                   const MCExpr *Subsection) {
+  MCAssembler &Asm = getAssembler();
+  auto *SectionWasm = static_cast<const MCSectionWasm *>(Section);
+  const MCSymbol *Grp = SectionWasm->getGroup();
+  if (Grp)
+    Asm.registerSymbol(*Grp);
+
+  this->MCObjectStreamer::ChangeSection(Section, Subsection);
+}
+
+void MCWasmStreamer::EmitWeakReference(MCSymbol *Alias,
+                                       const MCSymbol *Symbol) {
+  getAssembler().registerSymbol(*Symbol);
+  const MCExpr *Value = MCSymbolRefExpr::create(
+      Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
+  Alias->setVariableValue(Value);
+}
+
+bool MCWasmStreamer::EmitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
+  assert(Attribute != MCSA_IndirectSymbol && "indirect symbols not supported");
+
+  auto *Symbol = cast<MCSymbolWasm>(S);
+
+  // Adding a symbol attribute always introduces the symbol, note that an
+  // important side effect of calling registerSymbol here is to register
+  // the symbol with the assembler.
+  getAssembler().registerSymbol(*Symbol);
+
+  switch (Attribute) {
+  case MCSA_LazyReference:
+  case MCSA_Reference:
+  case MCSA_SymbolResolver:
+  case MCSA_PrivateExtern:
+  case MCSA_WeakDefinition:
+  case MCSA_WeakDefAutoPrivate:
+  case MCSA_Invalid:
+  case MCSA_IndirectSymbol:
+    return false;
+  case MCSA_Global:
+    Symbol->setExternal(true);
+    break;
+  case MCSA_ELF_TypeFunction:
+    Symbol->setIsFunction(true);
+    break;
+  case MCSA_ELF_TypeObject:
+    Symbol->setIsFunction(false);
+    break;
+  default:
+    // unrecognized directive
+    return false;
+  }
+
+  return true;
+}
+
+void MCWasmStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
+                                      unsigned ByteAlignment) {
+  llvm_unreachable("Common symbols are not yet implemented for Wasm");
+}
+
+void MCWasmStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
+  cast<MCSymbolWasm>(Symbol)->setSize(Value);
+}
+
+void MCWasmStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
+                                           unsigned ByteAlignment) {
+  llvm_unreachable("Local common symbols are not yet implemented for Wasm");
+}
+
+void MCWasmStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
+                                   SMLoc Loc) {
+  MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
+}
+
+void MCWasmStreamer::EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
+                                          unsigned ValueSize,
+                                          unsigned MaxBytesToEmit) {
+  MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value, ValueSize,
+                                         MaxBytesToEmit);
+}
+
+void MCWasmStreamer::EmitIdent(StringRef IdentString) {
+  MCSection *Comment = getAssembler().getContext().getWasmSection(
+      ".comment", 0, 0);
+  PushSection();
+  SwitchSection(Comment);
+  if (!SeenIdent) {
+    EmitIntValue(0, 1);
+    SeenIdent = true;
+  }
+  EmitBytes(IdentString);
+  EmitIntValue(0, 1);
+  PopSection();
+}
+
+void MCWasmStreamer::EmitInstToFragment(const MCInst &Inst,
+                                        const MCSubtargetInfo &STI) {
+  this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
+}
+
+void MCWasmStreamer::EmitInstToData(const MCInst &Inst,
+                                    const MCSubtargetInfo &STI) {
+  MCAssembler &Assembler = getAssembler();
+  SmallVector<MCFixup, 4> Fixups;
+  SmallString<256> Code;
+  raw_svector_ostream VecOS(Code);
+  Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
+
+  // Append the encoded instruction to the current data fragment (or create a
+  // new such fragment if the current fragment is not a data fragment).
+  MCDataFragment *DF = getOrCreateDataFragment();
+
+  // Add the fixups and data.
+  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
+    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
+    DF->getFixups().push_back(Fixups[i]);
+  }
+  DF->setHasInstructions(true);
+  DF->getContents().append(Code.begin(), Code.end());
+}
+
+void MCWasmStreamer::FinishImpl() {
+  EmitFrames(nullptr);
+
+  this->MCObjectStreamer::FinishImpl();
+}
+
+MCStreamer *llvm::createWasmStreamer(MCContext &Context, MCAsmBackend &MAB,
+                                     raw_pwrite_stream &OS, MCCodeEmitter *CE,
+                                     bool RelaxAll) {
+  MCWasmStreamer *S = new MCWasmStreamer(Context, MAB, OS, CE);
+  if (RelaxAll)
+    S->getAssembler().setRelaxAll(true);
+  return S;
+}
+
+void MCWasmStreamer::EmitThumbFunc(MCSymbol *Func) {
+  llvm_unreachable("Generic Wasm doesn't support this directive");
+}
+
+void MCWasmStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
+  llvm_unreachable("Wasm doesn't support this directive");
+}
+
+void MCWasmStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
+                                  uint64_t Size, unsigned ByteAlignment) {
+  llvm_unreachable("Wasm doesn't support this directive");
+}
+
+void MCWasmStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
+                                    uint64_t Size, unsigned ByteAlignment) {
+  llvm_unreachable("Wasm doesn't support this directive");
+}
diff --git a/lib/MC/MachObjectWriter.cpp b/lib/MC/MachObjectWriter.cpp
index c4b35f5db9b4..d9ccf0dd661f 100644
--- a/lib/MC/MachObjectWriter.cpp
+++ b/lib/MC/MachObjectWriter.cpp
@@ -7,23 +7,36 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCMachObjectWriter.h"
-#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/iterator_range.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
+#include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCFixupKindInfo.h"
+#include "llvm/MC/MCFragment.h"
+#include "llvm/MC/MCMachObjectWriter.h"
 #include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionMachO.h"
+#include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCSymbolMachO.h"
 #include "llvm/MC/MCValue.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MachO.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <string>
+#include <utility>
 #include <vector>
+
 using namespace llvm;
 
 #define DEBUG_TYPE "mc"
diff --git a/lib/MC/StringTableBuilder.cpp b/lib/MC/StringTableBuilder.cpp
index 1a501bcafc12..fbd7ba60bc90 100644
--- a/lib/MC/StringTableBuilder.cpp
+++ b/lib/MC/StringTableBuilder.cpp
@@ -1,4 +1,4 @@
-//===-- StringTableBuilder.cpp - String table building utility ------------===//
+//===- StringTableBuilder.cpp - String table building utility -------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,18 +7,24 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/StringTableBuilder.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/CachedHashString.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Support/COFF.h"
 #include "llvm/Support/Endian.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
-
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <utility>
 #include <vector>
 
 using namespace llvm;
 
-StringTableBuilder::~StringTableBuilder() {}
+StringTableBuilder::~StringTableBuilder() = default;
 
 void StringTableBuilder::initSize() {
   // Account for leading bytes in table so that offsets returned from add are
@@ -48,7 +54,7 @@ void StringTableBuilder::write(raw_ostream &OS) const {
   assert(isFinalized());
   SmallString<0> Data;
   Data.resize(getSize());
-  write((uint8_t *)&Data[0]);
+  write((uint8_t *)Data.data());
   OS << Data;
 }
 
diff --git a/lib/MC/SubtargetFeature.cpp b/lib/MC/SubtargetFeature.cpp
index 32f06f8a7d6a..51aaa4b0aa25 100644
--- a/lib/MC/SubtargetFeature.cpp
+++ b/lib/MC/SubtargetFeature.cpp
@@ -7,28 +7,31 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file implements the SubtargetFeature interface.
+/// \file Implements the SubtargetFeature interface.
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/SubtargetFeature.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/MC/SubtargetFeature.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
-#include <cctype>
-#include <cstdlib>
-using namespace llvm;
+#include <cstddef>
+#include <cstring>
+#include <iterator>
+#include <string>
+#include <vector>
 
-//===----------------------------------------------------------------------===//
-//                          Static Helper Functions
-//===----------------------------------------------------------------------===//
+using namespace llvm;
 
-/// hasFlag - Determine if a feature has a flag; '+' or '-'
-///
+/// Determine if a feature has a flag; '+' or '-'
 static inline bool hasFlag(StringRef Feature) {
   assert(!Feature.empty() && "Empty string");
   // Get first character
@@ -37,14 +40,12 @@ static inline bool hasFlag(StringRef Feature) {
   return Ch == '+' || Ch =='-';
 }
 
-/// StripFlag - Return string stripped of flag.
-///
+/// Return string stripped of flag.
 static inline std::string StripFlag(StringRef Feature) {
   return hasFlag(Feature) ? Feature.substr(1) : Feature;
 }
 
-/// isEnabled - Return true if enable flag; '+'.
-///
+/// Return true if enable flag; '+'.
 static inline bool isEnabled(StringRef Feature) {
   assert(!Feature.empty() && "Empty string");
   // Get first character
@@ -53,15 +54,13 @@ static inline bool isEnabled(StringRef Feature) {
   return Ch == '+';
 }
 
-/// Split - Splits a string of comma separated items in to a vector of strings.
-///
+/// Splits a string of comma separated items in to a vector of strings.
 static void Split(std::vector<std::string> &V, StringRef S) {
   SmallVector<StringRef, 3> Tmp;
   S.split(Tmp, ',', -1, false /* KeepEmpty */);
   V.assign(Tmp.begin(), Tmp.end());
 }
 
-/// Adding features.
 void SubtargetFeatures::AddFeature(StringRef String, bool Enable) {
   // Don't add empty features.
   if (!String.empty())
@@ -81,8 +80,7 @@ static const SubtargetFeatureKV *Find(StringRef S,
   return F;
 }
 
-/// getLongestEntryLength - Return the length of the longest entry in the table.
-///
+/// Return the length of the longest entry in the table.
 static size_t getLongestEntryLength(ArrayRef<SubtargetFeatureKV> Table) {
   size_t MaxLen = 0;
   for (auto &I : Table)
@@ -91,7 +89,6 @@ static size_t getLongestEntryLength(ArrayRef<SubtargetFeatureKV> Table) {
 }
 
 /// Display help for feature choices.
-///
 static void Help(ArrayRef<SubtargetFeatureKV> CPUTable,
                  ArrayRef<SubtargetFeatureKV> FeatTable) {
   // Determine the length of the longest CPU and Feature entries.
@@ -114,58 +111,47 @@ static void Help(ArrayRef<SubtargetFeatureKV> CPUTable,
             "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
 }
 
-//===----------------------------------------------------------------------===//
-//                    SubtargetFeatures Implementation
-//===----------------------------------------------------------------------===//
-
 SubtargetFeatures::SubtargetFeatures(StringRef Initial) {
   // Break up string into separate features
   Split(Features, Initial);
 }
 
-
 std::string SubtargetFeatures::getString() const {
   return join(Features.begin(), Features.end(), ",");
 }
 
-/// SetImpliedBits - For each feature that is (transitively) implied by this
-/// feature, set it.
-///
+/// For each feature that is (transitively) implied by this feature, set it.
 static
-void SetImpliedBits(FeatureBitset &Bits, const SubtargetFeatureKV *FeatureEntry,
+void SetImpliedBits(FeatureBitset &Bits, const SubtargetFeatureKV &FeatureEntry,
                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
-  for (auto &FE : FeatureTable) {
-    if (FeatureEntry->Value == FE.Value) continue;
+  for (const SubtargetFeatureKV &FE : FeatureTable) {
+    if (FeatureEntry.Value == FE.Value) continue;
 
-    if ((FeatureEntry->Implies & FE.Value).any()) {
+    if ((FeatureEntry.Implies & FE.Value).any()) {
       Bits |= FE.Value;
-      SetImpliedBits(Bits, &FE, FeatureTable);
+      SetImpliedBits(Bits, FE, FeatureTable);
     }
   }
 }
 
-/// ClearImpliedBits - For each feature that (transitively) implies this
-/// feature, clear it.
-///
+/// For each feature that (transitively) implies this feature, clear it.
 static
-void ClearImpliedBits(FeatureBitset &Bits, 
-                      const SubtargetFeatureKV *FeatureEntry,
+void ClearImpliedBits(FeatureBitset &Bits,
+                      const SubtargetFeatureKV &FeatureEntry,
                       ArrayRef<SubtargetFeatureKV> FeatureTable) {
-  for (auto &FE : FeatureTable) {
-    if (FeatureEntry->Value == FE.Value) continue;
+  for (const SubtargetFeatureKV &FE : FeatureTable) {
+    if (FeatureEntry.Value == FE.Value) continue;
 
-    if ((FE.Implies & FeatureEntry->Value).any()) {
+    if ((FE.Implies & FeatureEntry.Value).any()) {
       Bits &= ~FE.Value;
-      ClearImpliedBits(Bits, &FE, FeatureTable);
+      ClearImpliedBits(Bits, FE, FeatureTable);
     }
   }
 }
 
-/// ToggleFeature - Toggle a feature and update the feature bits.
 void
 SubtargetFeatures::ToggleFeature(FeatureBitset &Bits, StringRef Feature,
                                  ArrayRef<SubtargetFeatureKV> FeatureTable) {
-
   // Find feature in table.
   const SubtargetFeatureKV *FeatureEntry =
       Find(StripFlag(Feature), FeatureTable);
@@ -174,23 +160,21 @@ SubtargetFeatures::ToggleFeature(FeatureBitset &Bits, StringRef Feature,
     if ((Bits & FeatureEntry->Value) == FeatureEntry->Value) {
       Bits &= ~FeatureEntry->Value;
       // For each feature that implies this, clear it.
-      ClearImpliedBits(Bits, FeatureEntry, FeatureTable);
+      ClearImpliedBits(Bits, *FeatureEntry, FeatureTable);
     } else {
       Bits |=  FeatureEntry->Value;
 
       // For each feature that this implies, set it.
-      SetImpliedBits(Bits, FeatureEntry, FeatureTable);
+      SetImpliedBits(Bits, *FeatureEntry, FeatureTable);
     }
   } else {
-    errs() << "'" << Feature
-           << "' is not a recognized feature for this target"
+    errs() << "'" << Feature << "' is not a recognized feature for this target"
            << " (ignoring feature)\n";
   }
 }
 
 void SubtargetFeatures::ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
                                     ArrayRef<SubtargetFeatureKV> FeatureTable) {
-
   assert(hasFlag(Feature));
 
   // Find feature in table.
@@ -203,37 +187,30 @@ void SubtargetFeatures::ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,
       Bits |= FeatureEntry->Value;
 
       // For each feature that this implies, set it.
-      SetImpliedBits(Bits, FeatureEntry, FeatureTable);
+      SetImpliedBits(Bits, *FeatureEntry, FeatureTable);
     } else {
       Bits &= ~FeatureEntry->Value;
 
       // For each feature that implies this, clear it.
-      ClearImpliedBits(Bits, FeatureEntry, FeatureTable);
+      ClearImpliedBits(Bits, *FeatureEntry, FeatureTable);
     }
   } else {
-    errs() << "'" << Feature
-           << "' is not a recognized feature for this target"
+    errs() << "'" << Feature << "' is not a recognized feature for this target"
            << " (ignoring feature)\n";
   }
 }
 
-
-/// getFeatureBits - Get feature bits a CPU.
-///
 FeatureBitset
 SubtargetFeatures::getFeatureBits(StringRef CPU,
                                   ArrayRef<SubtargetFeatureKV> CPUTable,
                                   ArrayRef<SubtargetFeatureKV> FeatureTable) {
-
   if (CPUTable.empty() || FeatureTable.empty())
     return FeatureBitset();
 
-#ifndef NDEBUG
   assert(std::is_sorted(std::begin(CPUTable), std::end(CPUTable)) &&
          "CPU table is not sorted");
   assert(std::is_sorted(std::begin(FeatureTable), std::end(FeatureTable)) &&
          "CPU features table is not sorted");
-#endif
   // Resulting bits
   FeatureBitset Bits;
 
@@ -253,17 +230,16 @@ SubtargetFeatures::getFeatureBits(StringRef CPU,
       // Set the feature implied by this CPU feature, if any.
       for (auto &FE : FeatureTable) {
         if ((CPUEntry->Value & FE.Value).any())
-          SetImpliedBits(Bits, &FE, FeatureTable);
+          SetImpliedBits(Bits, FE, FeatureTable);
       }
     } else {
-      errs() << "'" << CPU
-             << "' is not a recognized processor for this target"
+      errs() << "'" << CPU << "' is not a recognized processor for this target"
              << " (ignoring processor)\n";
     }
   }
 
   // Iterate through each feature
-  for (auto &Feature : Features) {
+  for (const std::string &Feature : Features) {
     // Check for help
     if (Feature == "+help")
       Help(CPUTable, FeatureTable);
@@ -274,27 +250,22 @@ SubtargetFeatures::getFeatureBits(StringRef CPU,
   return Bits;
 }
 
-/// print - Print feature string.
-///
 void SubtargetFeatures::print(raw_ostream &OS) const {
   for (auto &F : Features)
     OS << F << " ";
   OS << "\n";
 }
 
-/// dump - Dump feature info.
-///
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void SubtargetFeatures::dump() const {
   print(dbgs());
 }
+#endif
 
-/// Adds the default features for the specified target triple.
-///
-/// FIXME: This is an inelegant way of specifying the features of a
-/// subtarget. It would be better if we could encode this information
-/// into the IR. See <rdar://5972456>.
-///
 void SubtargetFeatures::getDefaultSubtargetFeatures(const Triple& Triple) {
+  // FIXME: This is an inelegant way of specifying the features of a
+  // subtarget. It would be better if we could encode this information
+  // into the IR. See <rdar://5972456>.
   if (Triple.getVendor() == Triple::Apple) {
     if (Triple.getArch() == Triple::ppc) {
       // powerpc-apple-*
diff --git a/lib/MC/WasmObjectWriter.cpp b/lib/MC/WasmObjectWriter.cpp
new file mode 100644
index 000000000000..159cc3b4def2
--- /dev/null
+++ b/lib/MC/WasmObjectWriter.cpp
@@ -0,0 +1,1149 @@
+//===- lib/MC/WasmObjectWriter.cpp - Wasm File Writer ---------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements Wasm object file writer information.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCAsmLayout.h"
+#include "llvm/MC/MCAssembler.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCFixupKindInfo.h"
+#include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCSectionWasm.h"
+#include "llvm/MC/MCSymbolWasm.h"
+#include "llvm/MC/MCValue.h"
+#include "llvm/MC/MCWasmObjectWriter.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/StringSaver.h"
+#include "llvm/Support/Wasm.h"
+#include <vector>
+
+using namespace llvm;
+
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "reloc-info"
+
+namespace {
+// For patching purposes, we need to remember where each section starts, both
+// for patching up the section size field, and for patching up references to
+// locations within the section.
+struct SectionBookkeeping {
+  // Where the size of the section is written.
+  uint64_t SizeOffset;
+  // Where the contents of the section starts (after the header).
+  uint64_t ContentsOffset;
+};
+
+class WasmObjectWriter : public MCObjectWriter {
+  /// Helper struct for containing some precomputed information on symbols.
+  struct WasmSymbolData {
+    const MCSymbolWasm *Symbol;
+    StringRef Name;
+
+    // Support lexicographic sorting.
+    bool operator<(const WasmSymbolData &RHS) const { return Name < RHS.Name; }
+  };
+
+  /// The target specific Wasm writer instance.
+  std::unique_ptr<MCWasmObjectTargetWriter> TargetObjectWriter;
+
+  // Relocations for fixing up references in the code section.
+  std::vector<WasmRelocationEntry> CodeRelocations;
+
+  // Relocations for fixing up references in the data section.
+  std::vector<WasmRelocationEntry> DataRelocations;
+
+  // Fixups for call_indirect type indices.
+  std::vector<WasmRelocationEntry> TypeIndexFixups;
+
+  // Index values to use for fixing up call_indirect type indices.
+  std::vector<uint32_t> TypeIndexFixupTypes;
+
+  // TargetObjectWriter wrappers.
+  bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
+  unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
+                        const MCFixup &Fixup, bool IsPCRel) const {
+    return TargetObjectWriter->getRelocType(Ctx, Target, Fixup, IsPCRel);
+  }
+
+  void startSection(SectionBookkeeping &Section, unsigned SectionId,
+                    const char *Name = nullptr);
+  void endSection(SectionBookkeeping &Section);
+
+public:
+  WasmObjectWriter(MCWasmObjectTargetWriter *MOTW, raw_pwrite_stream &OS)
+      : MCObjectWriter(OS, /*IsLittleEndian=*/true), TargetObjectWriter(MOTW) {}
+
+private:
+  void reset() override {
+    MCObjectWriter::reset();
+  }
+
+  ~WasmObjectWriter() override;
+
+  void writeHeader(const MCAssembler &Asm);
+
+  void writeValueType(wasm::ValType Ty) {
+    encodeSLEB128(int32_t(Ty), getStream());
+  }
+
+  void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
+                        const MCFragment *Fragment, const MCFixup &Fixup,
+                        MCValue Target, bool &IsPCRel,
+                        uint64_t &FixedValue) override;
+
+  void executePostLayoutBinding(MCAssembler &Asm,
+                                const MCAsmLayout &Layout) override;
+
+  void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
+};
+} // end anonymous namespace
+
+WasmObjectWriter::~WasmObjectWriter() {}
+
+// Return the padding size to write a 32-bit value into a 5-byte ULEB128.
+static unsigned PaddingFor5ByteULEB128(uint32_t X) {
+  return X == 0 ? 4 : (4u - (31u - countLeadingZeros(X)) / 7u);
+}
+
+// Return the padding size to write a 32-bit value into a 5-byte SLEB128.
+static unsigned PaddingFor5ByteSLEB128(int32_t X) {
+  return 5 - getSLEB128Size(X);
+}
+
+// Write out a section header and a patchable section size field.
+void WasmObjectWriter::startSection(SectionBookkeeping &Section,
+                                    unsigned SectionId,
+                                    const char *Name) {
+  assert((Name != nullptr) == (SectionId == wasm::WASM_SEC_CUSTOM) &&
+         "Only custom sections can have names");
+
+  encodeULEB128(SectionId, getStream());
+
+  Section.SizeOffset = getStream().tell();
+
+  // The section size. We don't know the size yet, so reserve enough space
+  // for any 32-bit value; we'll patch it later.
+  encodeULEB128(UINT32_MAX, getStream());
+
+  // The position where the section starts, for measuring its size.
+  Section.ContentsOffset = getStream().tell();
+
+  // Custom sections in wasm also have a string identifier.
+  if (SectionId == wasm::WASM_SEC_CUSTOM) {
+    encodeULEB128(strlen(Name), getStream());
+    writeBytes(Name);
+  }
+}
+
+// Now that the section is complete and we know how big it is, patch up the
+// section size field at the start of the section.
+void WasmObjectWriter::endSection(SectionBookkeeping &Section) {
+  uint64_t Size = getStream().tell() - Section.ContentsOffset;
+  if (uint32_t(Size) != Size)
+    report_fatal_error("section size does not fit in a uint32_t");
+
+  unsigned Padding = PaddingFor5ByteULEB128(Size);
+
+  // Write the final section size to the payload_len field, which follows
+  // the section id byte.
+  uint8_t Buffer[16];
+  unsigned SizeLen = encodeULEB128(Size, Buffer, Padding);
+  assert(SizeLen == 5);
+  getStream().pwrite((char *)Buffer, SizeLen, Section.SizeOffset);
+}
+
+// Emit the Wasm header.
+void WasmObjectWriter::writeHeader(const MCAssembler &Asm) {
+  writeBytes(StringRef(wasm::WasmMagic, sizeof(wasm::WasmMagic)));
+  writeLE32(wasm::WasmVersion);
+}
+
+void WasmObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
+                                                const MCAsmLayout &Layout) {
+}
+
+void WasmObjectWriter::recordRelocation(MCAssembler &Asm,
+                                        const MCAsmLayout &Layout,
+                                        const MCFragment *Fragment,
+                                        const MCFixup &Fixup, MCValue Target,
+                                        bool &IsPCRel, uint64_t &FixedValue) {
+  MCSectionWasm &FixupSection = cast<MCSectionWasm>(*Fragment->getParent());
+  uint64_t C = Target.getConstant();
+  uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
+  MCContext &Ctx = Asm.getContext();
+
+  if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
+    assert(RefB->getKind() == MCSymbolRefExpr::VK_None &&
+           "Should not have constructed this");
+
+    // Let A, B and C being the components of Target and R be the location of
+    // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
+    // If it is pcrel, we want to compute (A - B + C - R).
+
+    // In general, Wasm has no relocations for -B. It can only represent (A + C)
+    // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
+    // replace B to implement it: (A - R - K + C)
+    if (IsPCRel) {
+      Ctx.reportError(
+          Fixup.getLoc(),
+          "No relocation available to represent this relative expression");
+      return;
+    }
+
+    const auto &SymB = cast<MCSymbolWasm>(RefB->getSymbol());
+
+    if (SymB.isUndefined()) {
+      Ctx.reportError(Fixup.getLoc(),
+                      Twine("symbol '") + SymB.getName() +
+                          "' can not be undefined in a subtraction expression");
+      return;
+    }
+
+    assert(!SymB.isAbsolute() && "Should have been folded");
+    const MCSection &SecB = SymB.getSection();
+    if (&SecB != &FixupSection) {
+      Ctx.reportError(Fixup.getLoc(),
+                      "Cannot represent a difference across sections");
+      return;
+    }
+
+    uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
+    uint64_t K = SymBOffset - FixupOffset;
+    IsPCRel = true;
+    C -= K;
+  }
+
+  // We either rejected the fixup or folded B into C at this point.
+  const MCSymbolRefExpr *RefA = Target.getSymA();
+  const auto *SymA = RefA ? cast<MCSymbolWasm>(&RefA->getSymbol()) : nullptr;
+
+  bool ViaWeakRef = false;
+  if (SymA && SymA->isVariable()) {
+    const MCExpr *Expr = SymA->getVariableValue();
+    if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) {
+      if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) {
+        SymA = cast<MCSymbolWasm>(&Inner->getSymbol());
+        ViaWeakRef = true;
+      }
+    }
+  }
+
+  // Put any constant offset in an addend. Offsets can be negative, and
+  // LLVM expects wrapping, in contrast to wasm's immediates which can't
+  // be negative and don't wrap.
+  FixedValue = 0;
+
+  if (SymA) {
+    if (ViaWeakRef)
+      llvm_unreachable("weakref used in reloc not yet implemented");
+    else
+      SymA->setUsedInReloc();
+  }
+
+  if (RefA) {
+    if (RefA->getKind() == MCSymbolRefExpr::VK_WebAssembly_TYPEINDEX) {
+      assert(C == 0);
+      WasmRelocationEntry Rec(FixupOffset, SymA, C,
+                              wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB,
+                              &FixupSection);
+      TypeIndexFixups.push_back(Rec);
+      return;
+    }
+  }
+
+  unsigned Type = getRelocType(Ctx, Target, Fixup, IsPCRel);
+
+  WasmRelocationEntry Rec(FixupOffset, SymA, C, Type, &FixupSection);
+
+  if (FixupSection.hasInstructions())
+    CodeRelocations.push_back(Rec);
+  else
+    DataRelocations.push_back(Rec);
+}
+
+namespace {
+
+// The signature of a wasm function, in a struct capable of being used as a
+// DenseMap key.
+struct WasmFunctionType {
+  // Support empty and tombstone instances, needed by DenseMap.
+  enum { Plain, Empty, Tombstone } State;
+
+  // The return types of the function.
+  SmallVector<wasm::ValType, 1> Returns;
+
+  // The parameter types of the function.
+  SmallVector<wasm::ValType, 4> Params;
+
+  WasmFunctionType() : State(Plain) {}
+
+  bool operator==(const WasmFunctionType &Other) const {
+    return State == Other.State && Returns == Other.Returns &&
+           Params == Other.Params;
+  }
+};
+
+// Traits for using WasmFunctionType in a DenseMap.
+struct WasmFunctionTypeDenseMapInfo {
+  static WasmFunctionType getEmptyKey() {
+    WasmFunctionType FuncTy;
+    FuncTy.State = WasmFunctionType::Empty;
+    return FuncTy;
+  }
+  static WasmFunctionType getTombstoneKey() {
+    WasmFunctionType FuncTy;
+    FuncTy.State = WasmFunctionType::Tombstone;
+    return FuncTy;
+  }
+  static unsigned getHashValue(const WasmFunctionType &FuncTy) {
+    uintptr_t Value = FuncTy.State;
+    for (wasm::ValType Ret : FuncTy.Returns)
+      Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Ret));
+    for (wasm::ValType Param : FuncTy.Params)
+      Value += DenseMapInfo<int32_t>::getHashValue(int32_t(Param));
+    return Value;
+  }
+  static bool isEqual(const WasmFunctionType &LHS,
+                      const WasmFunctionType &RHS) {
+    return LHS == RHS;
+  }
+};
+
+// A wasm import to be written into the import section.
+struct WasmImport {
+  StringRef ModuleName;
+  StringRef FieldName;
+  unsigned Kind;
+  int32_t Type;
+};
+
+// A wasm function to be written into the function section.
+struct WasmFunction {
+  int32_t Type;
+  const MCSymbolWasm *Sym;
+};
+
+// A wasm export to be written into the export section.
+struct WasmExport {
+  StringRef FieldName;
+  unsigned Kind;
+  uint32_t Index;
+};
+
+// A wasm global to be written into the global section.
+struct WasmGlobal {
+  wasm::ValType Type;
+  bool IsMutable;
+  bool HasImport;
+  uint64_t InitialValue;
+  uint32_t ImportIndex;
+};
+
+} // end anonymous namespace
+
+// Write X as an (unsigned) LEB value at offset Offset in Stream, padded
+// to allow patching.
+static void
+WritePatchableLEB(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) {
+  uint8_t Buffer[5];
+  unsigned Padding = PaddingFor5ByteULEB128(X);
+  unsigned SizeLen = encodeULEB128(X, Buffer, Padding);
+  assert(SizeLen == 5);
+  Stream.pwrite((char *)Buffer, SizeLen, Offset);
+}
+
+// Write X as an signed LEB value at offset Offset in Stream, padded
+// to allow patching.
+static void
+WritePatchableSLEB(raw_pwrite_stream &Stream, int32_t X, uint64_t Offset) {
+  uint8_t Buffer[5];
+  unsigned Padding = PaddingFor5ByteSLEB128(X);
+  unsigned SizeLen = encodeSLEB128(X, Buffer, Padding);
+  assert(SizeLen == 5);
+  Stream.pwrite((char *)Buffer, SizeLen, Offset);
+}
+
+// Write X as a plain integer value at offset Offset in Stream.
+static void WriteI32(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) {
+  uint8_t Buffer[4];
+  support::endian::write32le(Buffer, X);
+  Stream.pwrite((char *)Buffer, sizeof(Buffer), Offset);
+}
+
+// Compute a value to write into the code at the location covered
+// by RelEntry. This value isn't used by the static linker, since
+// we have addends; it just serves to make the code more readable
+// and to make standalone wasm modules directly usable.
+static uint32_t ProvisionalValue(const WasmRelocationEntry &RelEntry) {
+  const MCSymbolWasm *Sym = RelEntry.Symbol;
+
+  // For undefined symbols, use a hopefully invalid value.
+  if (!Sym->isDefined(false))
+    return UINT32_MAX;
+
+  MCSectionWasm &Section =
+    cast<MCSectionWasm>(RelEntry.Symbol->getSection(false));
+  uint64_t Address = Section.getSectionOffset() + RelEntry.Addend;
+
+  // Ignore overflow. LLVM allows address arithmetic to silently wrap.
+  uint32_t Value = Address;
+
+  return Value;
+}
+
+// Apply the portions of the relocation records that we can handle ourselves
+// directly.
+static void ApplyRelocations(
+    ArrayRef<WasmRelocationEntry> Relocations,
+    raw_pwrite_stream &Stream,
+    DenseMap<const MCSymbolWasm *, uint32_t> &SymbolIndices,
+    uint64_t ContentsOffset)
+{
+  for (const WasmRelocationEntry &RelEntry : Relocations) {
+    uint64_t Offset = ContentsOffset +
+                      RelEntry.FixupSection->getSectionOffset() +
+                      RelEntry.Offset;
+    switch (RelEntry.Type) {
+    case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB: {
+      uint32_t Index = SymbolIndices[RelEntry.Symbol];
+      assert(RelEntry.Addend == 0);
+
+      WritePatchableLEB(Stream, Index, Offset);
+      break;
+    }
+    case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB: {
+      uint32_t Index = SymbolIndices[RelEntry.Symbol];
+      assert(RelEntry.Addend == 0);
+
+      WritePatchableSLEB(Stream, Index, Offset);
+      break;
+    }
+    case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_SLEB: {
+      uint32_t Value = ProvisionalValue(RelEntry);
+
+      WritePatchableSLEB(Stream, Value, Offset);
+      break;
+    }
+    case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_LEB: {
+      uint32_t Value = ProvisionalValue(RelEntry);
+
+      WritePatchableLEB(Stream, Value, Offset);
+      break;
+    }
+    case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32: {
+      uint32_t Index = SymbolIndices[RelEntry.Symbol];
+      assert(RelEntry.Addend == 0);
+
+      WriteI32(Stream, Index, Offset);
+      break;
+    }
+    case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_I32: {
+      uint32_t Value = ProvisionalValue(RelEntry);
+
+      WriteI32(Stream, Value, Offset);
+      break;
+    }
+    default:
+      break;
+    }
+  }
+}
+
+// Write out the portions of the relocation records that the linker will
+// need to handle.
+static void WriteRelocations(
+    ArrayRef<WasmRelocationEntry> Relocations,
+    raw_pwrite_stream &Stream,
+    DenseMap<const MCSymbolWasm *, uint32_t> &SymbolIndices)
+{
+  for (const WasmRelocationEntry RelEntry : Relocations) {
+    encodeULEB128(RelEntry.Type, Stream);
+
+    uint64_t Offset = RelEntry.Offset +
+                      RelEntry.FixupSection->getSectionOffset();
+    uint32_t Index = SymbolIndices[RelEntry.Symbol];
+    int64_t Addend = RelEntry.Addend;
+
+    switch (RelEntry.Type) {
+    case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
+    case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
+    case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
+      encodeULEB128(Offset, Stream);
+      encodeULEB128(Index, Stream);
+      assert(Addend == 0 && "addends not supported for functions");
+      break;
+    case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_LEB:
+    case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_SLEB:
+    case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_I32:
+      encodeULEB128(Offset, Stream);
+      encodeULEB128(Index, Stream);
+      encodeSLEB128(Addend, Stream);
+      break;
+    default:
+      llvm_unreachable("unsupported relocation type");
+    }
+  }
+}
+
+// Write out the the type relocation records that the linker will
+// need to handle.
+static void WriteTypeRelocations(
+    ArrayRef<WasmRelocationEntry> TypeIndexFixups,
+    ArrayRef<uint32_t> TypeIndexFixupTypes,
+    raw_pwrite_stream &Stream)
+{
+  for (size_t i = 0, e = TypeIndexFixups.size(); i < e; ++i) {
+    const WasmRelocationEntry &Fixup = TypeIndexFixups[i];
+    uint32_t Type = TypeIndexFixupTypes[i];
+
+    assert(Fixup.Type == wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB);
+    assert(Fixup.Addend == 0);
+
+    uint64_t Offset = Fixup.Offset +
+                      Fixup.FixupSection->getSectionOffset();
+
+    encodeULEB128(Fixup.Type, Stream);
+    encodeULEB128(Offset, Stream);
+    encodeULEB128(Type, Stream);
+  }
+}
+
+void WasmObjectWriter::writeObject(MCAssembler &Asm,
+                                   const MCAsmLayout &Layout) {
+  MCContext &Ctx = Asm.getContext();
+  wasm::ValType PtrType = is64Bit() ? wasm::ValType::I64 : wasm::ValType::I32;
+
+  // Collect information from the available symbols.
+  DenseMap<WasmFunctionType, int32_t, WasmFunctionTypeDenseMapInfo>
+      FunctionTypeIndices;
+  SmallVector<WasmFunctionType, 4> FunctionTypes;
+  SmallVector<WasmFunction, 4> Functions;
+  SmallVector<uint32_t, 4> TableElems;
+  SmallVector<WasmGlobal, 4> Globals;
+  SmallVector<WasmImport, 4> Imports;
+  SmallVector<WasmExport, 4> Exports;
+  DenseMap<const MCSymbolWasm *, uint32_t> SymbolIndices;
+  SmallPtrSet<const MCSymbolWasm *, 4> IsAddressTaken;
+  unsigned NumFuncImports = 0;
+  unsigned NumGlobalImports = 0;
+  SmallVector<char, 0> DataBytes;
+  uint32_t StackPointerGlobal = 0;
+  bool HasStackPointer = false;
+
+  // Populate the IsAddressTaken set.
+  for (WasmRelocationEntry RelEntry : CodeRelocations) {
+    switch (RelEntry.Type) {
+    case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
+    case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_SLEB:
+      IsAddressTaken.insert(RelEntry.Symbol);
+      break;
+    default:
+      break;
+    }
+  }
+  for (WasmRelocationEntry RelEntry : DataRelocations) {
+    switch (RelEntry.Type) {
+    case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
+    case wasm::R_WEBASSEMBLY_GLOBAL_ADDR_I32:
+      IsAddressTaken.insert(RelEntry.Symbol);
+      break;
+    default:
+      break;
+    }
+  }
+
+  // Populate the Imports set.
+  for (const MCSymbol &S : Asm.symbols()) {
+    const auto &WS = static_cast<const MCSymbolWasm &>(S);
+    int32_t Type;
+
+    if (WS.isFunction()) {
+      // Prepare the function's type, if we haven't seen it yet.
+      WasmFunctionType F;
+      F.Returns = WS.getReturns();
+      F.Params = WS.getParams();
+      auto Pair =
+          FunctionTypeIndices.insert(std::make_pair(F, FunctionTypes.size()));
+      if (Pair.second)
+        FunctionTypes.push_back(F);
+
+      Type = Pair.first->second;
+    } else {
+      Type = int32_t(PtrType);
+    }
+
+    // If the symbol is not defined in this translation unit, import it.
+    if (!WS.isTemporary() && !WS.isDefined(/*SetUsed=*/false)) {
+      WasmImport Import;
+      Import.ModuleName = WS.getModuleName();
+      Import.FieldName = WS.getName();
+
+      if (WS.isFunction()) {
+        Import.Kind = wasm::WASM_EXTERNAL_FUNCTION;
+        Import.Type = Type;
+        SymbolIndices[&WS] = NumFuncImports;
+        ++NumFuncImports;
+      } else {
+        Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
+        Import.Type = Type;
+        SymbolIndices[&WS] = NumGlobalImports;
+        ++NumGlobalImports;
+      }
+
+      Imports.push_back(Import);
+    }
+  }
+
+  // In the special .global_variables section, we've encoded global
+  // variables used by the function. Translate them into the Globals
+  // list.
+  MCSectionWasm *GlobalVars = Ctx.getWasmSection(".global_variables", 0, 0);
+  if (!GlobalVars->getFragmentList().empty()) {
+    if (GlobalVars->getFragmentList().size() != 1)
+      report_fatal_error("only one .global_variables fragment supported");
+    const MCFragment &Frag = *GlobalVars->begin();
+    if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
+      report_fatal_error("only data supported in .global_variables");
+    const MCDataFragment &DataFrag = cast<MCDataFragment>(Frag);
+    if (!DataFrag.getFixups().empty())
+      report_fatal_error("fixups not supported in .global_variables");
+    const SmallVectorImpl<char> &Contents = DataFrag.getContents();
+    for (const uint8_t *p = (const uint8_t *)Contents.data(),
+                     *end = (const uint8_t *)Contents.data() + Contents.size();
+         p != end; ) {
+      WasmGlobal G;
+      if (end - p < 3)
+        report_fatal_error("truncated global variable encoding");
+      G.Type = wasm::ValType(int8_t(*p++));
+      G.IsMutable = bool(*p++);
+      G.HasImport = bool(*p++);
+      if (G.HasImport) {
+        G.InitialValue = 0;
+
+        WasmImport Import;
+        Import.ModuleName = (const char *)p;
+        const uint8_t *nul = (const uint8_t *)memchr(p, '\0', end - p);
+        if (!nul)
+          report_fatal_error("global module name must be nul-terminated");
+        p = nul + 1;
+        nul = (const uint8_t *)memchr(p, '\0', end - p);
+        if (!nul)
+          report_fatal_error("global base name must be nul-terminated");
+        Import.FieldName = (const char *)p;
+        p = nul + 1;
+
+        Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
+        Import.Type = int32_t(G.Type);
+
+        G.ImportIndex = NumGlobalImports;
+        ++NumGlobalImports;
+
+        Imports.push_back(Import);
+      } else {
+        unsigned n;
+        G.InitialValue = decodeSLEB128(p, &n);
+        G.ImportIndex = 0;
+        if ((ptrdiff_t)n > end - p)
+          report_fatal_error("global initial value must be valid SLEB128");
+        p += n;
+      }
+      Globals.push_back(G);
+    }
+  }
+
+  // In the special .stack_pointer section, we've encoded the stack pointer
+  // index.
+  MCSectionWasm *StackPtr = Ctx.getWasmSection(".stack_pointer", 0, 0);
+  if (!StackPtr->getFragmentList().empty()) {
+    if (StackPtr->getFragmentList().size() != 1)
+      report_fatal_error("only one .stack_pointer fragment supported");
+    const MCFragment &Frag = *StackPtr->begin();
+    if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
+      report_fatal_error("only data supported in .stack_pointer");
+    const MCDataFragment &DataFrag = cast<MCDataFragment>(Frag);
+    if (!DataFrag.getFixups().empty())
+      report_fatal_error("fixups not supported in .stack_pointer");
+    const SmallVectorImpl<char> &Contents = DataFrag.getContents();
+    if (Contents.size() != 4)
+      report_fatal_error("only one entry supported in .stack_pointer");
+    HasStackPointer = true;
+    StackPointerGlobal = NumGlobalImports + *(const int32_t *)Contents.data();
+  }
+
+  // Handle defined symbols.
+  for (const MCSymbol &S : Asm.symbols()) {
+    // Ignore unnamed temporary symbols, which aren't ever exported, imported,
+    // or used in relocations.
+    if (S.isTemporary() && S.getName().empty())
+      continue;
+    const auto &WS = static_cast<const MCSymbolWasm &>(S);
+    unsigned Index;
+    if (WS.isFunction()) {
+      // Prepare the function's type, if we haven't seen it yet.
+      WasmFunctionType F;
+      F.Returns = WS.getReturns();
+      F.Params = WS.getParams();
+      auto Pair =
+          FunctionTypeIndices.insert(std::make_pair(F, FunctionTypes.size()));
+      if (Pair.second)
+        FunctionTypes.push_back(F);
+
+      int32_t Type = Pair.first->second;
+
+      if (WS.isDefined(/*SetUsed=*/false)) {
+        // A definition. Take the next available index.
+        Index = NumFuncImports + Functions.size();
+
+        // Prepare the function.
+        WasmFunction Func;
+        Func.Type = Type;
+        Func.Sym = &WS;
+        SymbolIndices[&WS] = Index;
+        Functions.push_back(Func);
+      } else {
+        // An import; the index was assigned above.
+        Index = SymbolIndices.find(&WS)->second;
+      }
+
+      // If needed, prepare the function to be called indirectly.
+      if (IsAddressTaken.count(&WS))
+        TableElems.push_back(Index);
+    } else {
+      // For now, ignore temporary non-function symbols.
+      if (S.isTemporary())
+        continue;
+
+      if (WS.getOffset() != 0)
+        report_fatal_error("data sections must contain one variable each");
+      if (!WS.getSize())
+        report_fatal_error("data symbols must have a size set with .size");
+
+      int64_t Size = 0;
+      if (!WS.getSize()->evaluateAsAbsolute(Size, Layout))
+        report_fatal_error(".size expression must be evaluatable");
+
+      if (WS.isDefined(false)) {
+        MCSectionWasm &DataSection =
+            static_cast<MCSectionWasm &>(WS.getSection());
+
+        if (uint64_t(Size) != Layout.getSectionFileSize(&DataSection))
+          report_fatal_error("data sections must contain at most one variable");
+
+        DataBytes.resize(alignTo(DataBytes.size(), DataSection.getAlignment()));
+
+        DataSection.setSectionOffset(DataBytes.size());
+
+        for (MCSection::iterator I = DataSection.begin(), E = DataSection.end();
+             I != E; ++I) {
+          const MCFragment &Frag = *I;
+          if (Frag.hasInstructions())
+            report_fatal_error("only data supported in data sections");
+
+          if (const MCAlignFragment *Align = dyn_cast<MCAlignFragment>(&Frag)) {
+            if (Align->getValueSize() != 1)
+              report_fatal_error("only byte values supported for alignment");
+            // If nops are requested, use zeros, as this is the data section.
+            uint8_t Value = Align->hasEmitNops() ? 0 : Align->getValue();
+            uint64_t Size = std::min<uint64_t>(alignTo(DataBytes.size(),
+                                                       Align->getAlignment()),
+                                               DataBytes.size() +
+                                                   Align->getMaxBytesToEmit());
+            DataBytes.resize(Size, Value);
+          } else if (const MCFillFragment *Fill =
+                                              dyn_cast<MCFillFragment>(&Frag)) {
+            DataBytes.insert(DataBytes.end(), Size, Fill->getValue());
+          } else {
+            const MCDataFragment &DataFrag = cast<MCDataFragment>(Frag);
+            const SmallVectorImpl<char> &Contents = DataFrag.getContents();
+
+            DataBytes.insert(DataBytes.end(), Contents.begin(), Contents.end());
+          }
+        }
+
+        // For each external global, prepare a corresponding wasm global
+        // holding its address.
+        if (WS.isExternal()) {
+          Index = NumGlobalImports + Globals.size();
+
+          WasmGlobal Global;
+          Global.Type = PtrType;
+          Global.IsMutable = false;
+          Global.HasImport = false;
+          Global.InitialValue = DataSection.getSectionOffset();
+          Global.ImportIndex = 0;
+          SymbolIndices[&WS] = Index;
+          Globals.push_back(Global);
+        }
+      }
+    }
+
+    // If the symbol is visible outside this translation unit, export it.
+    if (WS.isExternal()) {
+      assert(WS.isDefined(false));
+      WasmExport Export;
+      Export.FieldName = WS.getName();
+      Export.Index = Index;
+
+      if (WS.isFunction())
+        Export.Kind = wasm::WASM_EXTERNAL_FUNCTION;
+      else
+        Export.Kind = wasm::WASM_EXTERNAL_GLOBAL;
+
+      Exports.push_back(Export);
+    }
+  }
+
+  // Add types for indirect function calls.
+  for (const WasmRelocationEntry &Fixup : TypeIndexFixups) {
+    assert(Fixup.Addend == 0);
+    assert(Fixup.Type == wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB);
+
+    WasmFunctionType F;
+    F.Returns = Fixup.Symbol->getReturns();
+    F.Params = Fixup.Symbol->getParams();
+    auto Pair =
+        FunctionTypeIndices.insert(std::make_pair(F, FunctionTypes.size()));
+    if (Pair.second)
+      FunctionTypes.push_back(F);
+
+    TypeIndexFixupTypes.push_back(Pair.first->second);
+  }
+
+  // Write out the Wasm header.
+  writeHeader(Asm);
+
+  SectionBookkeeping Section;
+
+  // === Type Section =========================================================
+  if (!FunctionTypes.empty()) {
+    startSection(Section, wasm::WASM_SEC_TYPE);
+
+    encodeULEB128(FunctionTypes.size(), getStream());
+
+    for (WasmFunctionType &FuncTy : FunctionTypes) {
+      encodeSLEB128(wasm::WASM_TYPE_FUNC, getStream());
+      encodeULEB128(FuncTy.Params.size(), getStream());
+      for (wasm::ValType Ty : FuncTy.Params)
+        writeValueType(Ty);
+      encodeULEB128(FuncTy.Returns.size(), getStream());
+      for (wasm::ValType Ty : FuncTy.Returns)
+        writeValueType(Ty);
+    }
+
+    endSection(Section);
+  }
+
+  // === Import Section ========================================================
+  if (!Imports.empty()) {
+    startSection(Section, wasm::WASM_SEC_IMPORT);
+
+    encodeULEB128(Imports.size(), getStream());
+    for (const WasmImport &Import : Imports) {
+      StringRef ModuleName = Import.ModuleName;
+      encodeULEB128(ModuleName.size(), getStream());
+      writeBytes(ModuleName);
+
+      StringRef FieldName = Import.FieldName;
+      encodeULEB128(FieldName.size(), getStream());
+      writeBytes(FieldName);
+
+      encodeULEB128(Import.Kind, getStream());
+
+      switch (Import.Kind) {
+      case wasm::WASM_EXTERNAL_FUNCTION:
+        encodeULEB128(Import.Type, getStream());
+        break;
+      case wasm::WASM_EXTERNAL_GLOBAL:
+        encodeSLEB128(int32_t(Import.Type), getStream());
+        encodeULEB128(0, getStream()); // mutability
+        break;
+      default:
+        llvm_unreachable("unsupported import kind");
+      }
+    }
+
+    endSection(Section);
+  }
+
+  // === Function Section ======================================================
+  if (!Functions.empty()) {
+    startSection(Section, wasm::WASM_SEC_FUNCTION);
+
+    encodeULEB128(Functions.size(), getStream());
+    for (const WasmFunction &Func : Functions)
+      encodeULEB128(Func.Type, getStream());
+
+    endSection(Section);
+  }
+
+  // === Table Section =========================================================
+  // For now, always emit the table section, since indirect calls are not
+  // valid without it. In the future, we could perhaps be more clever and omit
+  // it if there are no indirect calls.
+  startSection(Section, wasm::WASM_SEC_TABLE);
+
+  // The number of tables, fixed to 1 for now.
+  encodeULEB128(1, getStream());
+
+  encodeSLEB128(wasm::WASM_TYPE_ANYFUNC, getStream());
+
+  encodeULEB128(0, getStream());                 // flags
+  encodeULEB128(TableElems.size(), getStream()); // initial
+
+  endSection(Section);
+
+  // === Memory Section ========================================================
+  // For now, always emit the memory section, since loads and stores are not
+  // valid without it. In the future, we could perhaps be more clever and omit
+  // it if there are no loads or stores.
+  startSection(Section, wasm::WASM_SEC_MEMORY);
+
+  encodeULEB128(1, getStream()); // number of memory spaces
+
+  encodeULEB128(0, getStream()); // flags
+  encodeULEB128(DataBytes.size(), getStream()); // initial
+
+  endSection(Section);
+
+  // === Global Section ========================================================
+  if (!Globals.empty()) {
+    startSection(Section, wasm::WASM_SEC_GLOBAL);
+
+    encodeULEB128(Globals.size(), getStream());
+    for (const WasmGlobal &Global : Globals) {
+      writeValueType(Global.Type);
+      write8(Global.IsMutable);
+
+      if (Global.HasImport) {
+        assert(Global.InitialValue == 0);
+        write8(wasm::WASM_OPCODE_GET_GLOBAL);
+        encodeULEB128(Global.ImportIndex, getStream());
+      } else {
+        assert(Global.ImportIndex == 0);
+        write8(wasm::WASM_OPCODE_I32_CONST);
+        encodeSLEB128(Global.InitialValue, getStream()); // offset
+      }
+      write8(wasm::WASM_OPCODE_END);
+    }
+
+    endSection(Section);
+  }
+
+  // === Export Section ========================================================
+  if (!Exports.empty()) {
+    startSection(Section, wasm::WASM_SEC_EXPORT);
+
+    encodeULEB128(Exports.size(), getStream());
+    for (const WasmExport &Export : Exports) {
+      encodeULEB128(Export.FieldName.size(), getStream());
+      writeBytes(Export.FieldName);
+
+      encodeSLEB128(Export.Kind, getStream());
+
+      encodeULEB128(Export.Index, getStream());
+    }
+
+    endSection(Section);
+  }
+
+#if 0 // TODO: Start Section
+  if (HaveStartFunction) {
+    // === Start Section =========================================================
+    startSection(Section, wasm::WASM_SEC_START);
+
+    encodeSLEB128(StartFunction, getStream());
+
+    endSection(Section);
+  }
+#endif
+
+  // === Elem Section ==========================================================
+  if (!TableElems.empty()) {
+    startSection(Section, wasm::WASM_SEC_ELEM);
+
+    encodeULEB128(1, getStream()); // number of "segments"
+    encodeULEB128(0, getStream()); // the table index
+
+    // init expr for starting offset
+    write8(wasm::WASM_OPCODE_I32_CONST);
+    encodeSLEB128(0, getStream());
+    write8(wasm::WASM_OPCODE_END);
+
+    encodeULEB128(TableElems.size(), getStream());
+    for (uint32_t Elem : TableElems)
+      encodeULEB128(Elem, getStream());
+
+    endSection(Section);
+  }
+
+  // === Code Section ==========================================================
+  if (!Functions.empty()) {
+    startSection(Section, wasm::WASM_SEC_CODE);
+
+    encodeULEB128(Functions.size(), getStream());
+
+    for (const WasmFunction &Func : Functions) {
+      MCSectionWasm &FuncSection =
+          static_cast<MCSectionWasm &>(Func.Sym->getSection());
+
+      if (Func.Sym->isVariable())
+        report_fatal_error("weak symbols not supported yet");
+
+      if (Func.Sym->getOffset() != 0)
+        report_fatal_error("function sections must contain one function each");
+
+      if (!Func.Sym->getSize())
+        report_fatal_error("function symbols must have a size set with .size");
+
+      int64_t Size = 0;
+      if (!Func.Sym->getSize()->evaluateAsAbsolute(Size, Layout))
+        report_fatal_error(".size expression must be evaluatable");
+
+      encodeULEB128(Size, getStream());
+
+      FuncSection.setSectionOffset(getStream().tell() -
+                                   Section.ContentsOffset);
+
+      Asm.writeSectionData(&FuncSection, Layout);
+    }
+
+    // Apply the type index fixups for call_indirect etc. instructions.
+    for (size_t i = 0, e = TypeIndexFixups.size(); i < e; ++i) {
+      uint32_t Type = TypeIndexFixupTypes[i];
+      unsigned Padding = PaddingFor5ByteULEB128(Type);
+
+      const WasmRelocationEntry &Fixup = TypeIndexFixups[i];
+      assert(Fixup.Addend == 0);
+      assert(Fixup.Type == wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB);
+      uint64_t Offset = Fixup.Offset +
+                        Fixup.FixupSection->getSectionOffset();
+
+      uint8_t Buffer[16];
+      unsigned SizeLen = encodeULEB128(Type, Buffer, Padding);
+      assert(SizeLen == 5);
+      getStream().pwrite((char *)Buffer, SizeLen,
+                         Section.ContentsOffset + Offset);
+    }
+
+    // Apply fixups.
+    ApplyRelocations(CodeRelocations, getStream(), SymbolIndices,
+                     Section.ContentsOffset);
+
+    endSection(Section);
+  }
+
+  // === Data Section ==========================================================
+  if (!DataBytes.empty()) {
+    startSection(Section, wasm::WASM_SEC_DATA);
+
+    encodeULEB128(1, getStream()); // count
+    encodeULEB128(0, getStream()); // memory index
+    write8(wasm::WASM_OPCODE_I32_CONST);
+    encodeSLEB128(0, getStream()); // offset
+    write8(wasm::WASM_OPCODE_END);
+    encodeULEB128(DataBytes.size(), getStream()); // size
+    writeBytes(DataBytes); // data
+
+    // Apply fixups.
+    ApplyRelocations(DataRelocations, getStream(), SymbolIndices,
+                     Section.ContentsOffset);
+
+    endSection(Section);
+  }
+
+  // === Name Section ==========================================================
+  uint32_t TotalFunctions = NumFuncImports + Functions.size();
+  if (TotalFunctions != 0) {
+    startSection(Section, wasm::WASM_SEC_CUSTOM, "name");
+    SectionBookkeeping SubSection;
+    startSection(SubSection, wasm::WASM_NAMES_FUNCTION);
+
+    encodeULEB128(TotalFunctions, getStream());
+    uint32_t Index = 0;
+    for (const WasmImport &Import : Imports) {
+      if (Import.Kind == wasm::WASM_EXTERNAL_FUNCTION) {
+        encodeULEB128(Index, getStream());
+        encodeULEB128(Import.FieldName.size(), getStream());
+        writeBytes(Import.FieldName);
+        ++Index;
+      }
+    }
+    for (const WasmFunction &Func : Functions) {
+      encodeULEB128(Index, getStream());
+      encodeULEB128(Func.Sym->getName().size(), getStream());
+      writeBytes(Func.Sym->getName());
+      ++Index;
+    }
+
+    endSection(SubSection);
+    endSection(Section);
+  }
+
+  // See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md
+  // for descriptions of the reloc sections.
+
+  // === Code Reloc Section ====================================================
+  if (!CodeRelocations.empty()) {
+    startSection(Section, wasm::WASM_SEC_CUSTOM, "reloc.CODE");
+
+    encodeULEB128(wasm::WASM_SEC_CODE, getStream());
+
+    encodeULEB128(CodeRelocations.size(), getStream());
+
+    WriteRelocations(CodeRelocations, getStream(), SymbolIndices);
+    WriteTypeRelocations(TypeIndexFixups, TypeIndexFixupTypes, getStream());
+
+    endSection(Section);
+  }
+
+  // === Data Reloc Section ====================================================
+  if (!DataRelocations.empty()) {
+    startSection(Section, wasm::WASM_SEC_CUSTOM, "reloc.DATA");
+
+    encodeULEB128(wasm::WASM_SEC_DATA, getStream());
+
+    encodeULEB128(DataRelocations.size(), getStream());
+
+    WriteRelocations(DataRelocations, getStream(), SymbolIndices);
+
+    endSection(Section);
+  }
+
+  // === Linking Metadata Section ==============================================
+  if (HasStackPointer) {
+    startSection(Section, wasm::WASM_SEC_CUSTOM, "linking");
+
+    encodeULEB128(1, getStream()); // count
+
+    encodeULEB128(wasm::WASM_STACK_POINTER, getStream()); // type
+    encodeULEB128(StackPointerGlobal, getStream()); // id
+
+    endSection(Section);
+  }
+
+  // TODO: Translate the .comment section to the output.
+
+  // TODO: Translate debug sections to the output.
+}
+
+MCObjectWriter *llvm::createWasmObjectWriter(MCWasmObjectTargetWriter *MOTW,
+                                             raw_pwrite_stream &OS) {
+  return new WasmObjectWriter(MOTW, OS);
+}
diff --git a/lib/MC/WinCOFFObjectWriter.cpp b/lib/MC/WinCOFFObjectWriter.cpp
index afc5c6a14d11..da8fe73f823b 100644
--- a/lib/MC/WinCOFFObjectWriter.cpp
+++ b/lib/MC/WinCOFFObjectWriter.cpp
@@ -1,4 +1,4 @@
-//===-- llvm/MC/WinCOFFObjectWriter.cpp -------------------------*- C++ -*-===//
+//===- llvm/MC/WinCOFFObjectWriter.cpp ------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -11,37 +11,49 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCWinCOFFObjectWriter.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
-#include "llvm/Config/config.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
-#include "llvm/MC/MCObjectFileInfo.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionCOFF.h"
+#include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCSymbolCOFF.h"
 #include "llvm/MC/MCValue.h"
+#include "llvm/MC/MCWinCOFFObjectWriter.h"
 #include "llvm/MC/StringTableBuilder.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/COFF.h"
-#include "llvm/Support/Debug.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/JamCRC.h"
-#include <cstdio>
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
 #include <ctime>
+#include <memory>
+#include <string>
+#include <vector>
 
 using namespace llvm;
+using llvm::support::endian::write32le;
 
 #define DEBUG_TYPE "WinCOFFObjectWriter"
 
 namespace {
+
 typedef SmallString<COFF::NameSize> name;
 
 enum AuxiliaryType {
@@ -57,25 +69,24 @@ struct AuxSymbol {
   COFF::Auxiliary Aux;
 };
 
-class COFFSymbol;
 class COFFSection;
 
 class COFFSymbol {
 public:
-  COFF::symbol Data;
+  COFF::symbol Data = {};
 
   typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
 
   name Name;
   int Index;
   AuxiliarySymbols Aux;
-  COFFSymbol *Other;
-  COFFSection *Section;
-  int Relocations;
+  COFFSymbol *Other = nullptr;
+  COFFSection *Section = nullptr;
+  int Relocations = 0;
+  const MCSymbol *MC = nullptr;
 
-  const MCSymbol *MC;
+  COFFSymbol(StringRef Name) : Name(Name) {}
 
-  COFFSymbol(StringRef name);
   void set_name_offset(uint32_t Offset);
 
   int64_t getIndex() const { return Index; }
@@ -89,9 +100,10 @@ public:
 // This class contains staging data for a COFF relocation entry.
 struct COFFRelocation {
   COFF::relocation Data;
-  COFFSymbol *Symb;
+  COFFSymbol *Symb = nullptr;
+
+  COFFRelocation() = default;
 
-  COFFRelocation() : Symb(nullptr) {}
   static size_t size() { return COFF::RelocationSize; }
 };
 
@@ -99,15 +111,15 @@ typedef std::vector<COFFRelocation> relocations;
 
 class COFFSection {
 public:
-  COFF::section Header;
+  COFF::section Header = {};
 
   std::string Name;
   int Number;
-  MCSectionCOFF const *MCSection;
-  COFFSymbol *Symbol;
+  MCSectionCOFF const *MCSection = nullptr;
+  COFFSymbol *Symbol = nullptr;
   relocations Relocations;
 
-  COFFSection(StringRef name);
+  COFFSection(StringRef Name) : Name(Name) {}
 };
 
 class WinCOFFObjectWriter : public MCObjectWriter {
@@ -121,7 +133,7 @@ public:
   std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
 
   // Root level file contents.
-  COFF::header Header;
+  COFF::header Header = {};
   sections Sections;
   symbols Symbols;
   StringTableBuilder Strings{StringTableBuilder::WinCOFF};
@@ -149,9 +161,6 @@ public:
   COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol);
   COFFSection *createSection(StringRef Name);
 
-  template <typename object_t, typename list_t>
-  object_t *createCOFFEntity(StringRef Name, list_t &List);
-
   void defineSection(MCSectionCOFF const &Sec);
 
   COFFSymbol *getLinkedSymbol(const MCSymbol &Symbol);
@@ -168,8 +177,12 @@ public:
   void WriteFileHeader(const COFF::header &Header);
   void WriteSymbol(const COFFSymbol &S);
   void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
-  void writeSectionHeader(const COFF::section &S);
+  void writeSectionHeaders();
   void WriteRelocation(const COFF::relocation &R);
+  uint32_t writeSectionContents(MCAssembler &Asm, const MCAsmLayout &Layout,
+                                const MCSection &MCSec);
+  void writeSection(MCAssembler &Asm, const MCAsmLayout &Layout,
+                    const COFFSection &Sec, const MCSection &MCSec);
 
   // MCObjectWriter interface implementation.
 
@@ -181,45 +194,29 @@ public:
                                               const MCFragment &FB, bool InSet,
                                               bool IsPCRel) const override;
 
-  bool isWeak(const MCSymbol &Sym) const override;
-
   void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
                         const MCFragment *Fragment, const MCFixup &Fixup,
                         MCValue Target, bool &IsPCRel,
                         uint64_t &FixedValue) override;
 
+  void createFileSymbols(MCAssembler &Asm);
+  void assignSectionNumbers();
+  void assignFileOffsets(MCAssembler &Asm, const MCAsmLayout &Layout);
+
   void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
 };
-}
 
-static inline void write_uint32_le(void *Data, uint32_t Value) {
-  support::endian::write<uint32_t, support::little, support::unaligned>(Data,
-                                                                        Value);
-}
+} // end anonymous namespace
 
 //------------------------------------------------------------------------------
 // Symbol class implementation
 
-COFFSymbol::COFFSymbol(StringRef name)
-    : Name(name.begin(), name.end()), Other(nullptr), Section(nullptr),
-      Relocations(0), MC(nullptr) {
-  memset(&Data, 0, sizeof(Data));
-}
-
 // In the case that the name does not fit within 8 bytes, the offset
 // into the string table is stored in the last 4 bytes instead, leaving
 // the first 4 bytes as 0.
 void COFFSymbol::set_name_offset(uint32_t Offset) {
-  write_uint32_le(Data.Name + 0, 0);
-  write_uint32_le(Data.Name + 4, Offset);
-}
-
-//------------------------------------------------------------------------------
-// Section class implementation
-
-COFFSection::COFFSection(StringRef name)
-    : Name(name), MCSection(nullptr), Symbol(nullptr) {
-  memset(&Header, 0, sizeof(Header));
+  write32le(Data.Name + 0, 0);
+  write32le(Data.Name + 4, Offset);
 }
 
 //------------------------------------------------------------------------------
@@ -228,115 +225,92 @@ COFFSection::COFFSection(StringRef name)
 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
                                          raw_pwrite_stream &OS)
     : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
-  memset(&Header, 0, sizeof(Header));
-
   Header.Machine = TargetObjectWriter->getMachine();
 }
 
 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
-  return createCOFFEntity<COFFSymbol>(Name, Symbols);
+  Symbols.push_back(make_unique<COFFSymbol>(Name));
+  return Symbols.back().get();
 }
 
 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
-  symbol_map::iterator i = SymbolMap.find(Symbol);
-  if (i != SymbolMap.end())
-    return i->second;
-  COFFSymbol *RetSymbol =
-      createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
-  SymbolMap[Symbol] = RetSymbol;
-  return RetSymbol;
+  COFFSymbol *&Ret = SymbolMap[Symbol];
+  if (!Ret)
+    Ret = createSymbol(Symbol->getName());
+  return Ret;
 }
 
 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
-  return createCOFFEntity<COFFSection>(Name, Sections);
+  Sections.emplace_back(make_unique<COFFSection>(Name));
+  return Sections.back().get();
 }
 
-/// A template used to lookup or create a symbol/section, and initialize it if
-/// needed.
-template <typename object_t, typename list_t>
-object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, list_t &List) {
-  List.push_back(make_unique<object_t>(Name));
-
-  return List.back().get();
-}
-
-/// This function takes a section data object from the assembler
-/// and creates the associated COFF section staging object.
-void WinCOFFObjectWriter::defineSection(MCSectionCOFF const &Sec) {
-  COFFSection *coff_section = createSection(Sec.getSectionName());
-  COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
-  if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
-    if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
-      COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
-      if (COMDATSymbol->Section)
-        report_fatal_error("two sections have the same comdat");
-      COMDATSymbol->Section = coff_section;
-    }
-  }
-
-  coff_section->Symbol = coff_symbol;
-  coff_symbol->Section = coff_section;
-  coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
-
-  // In this case the auxiliary symbol is a Section Definition.
-  coff_symbol->Aux.resize(1);
-  memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
-  coff_symbol->Aux[0].AuxType = ATSectionDefinition;
-  coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
-
-  coff_section->Header.Characteristics = Sec.getCharacteristics();
-
-  uint32_t &Characteristics = coff_section->Header.Characteristics;
+static uint32_t getAlignment(const MCSectionCOFF &Sec) {
   switch (Sec.getAlignment()) {
   case 1:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_1BYTES;
   case 2:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_2BYTES;
   case 4:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_4BYTES;
   case 8:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_8BYTES;
   case 16:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_16BYTES;
   case 32:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_32BYTES;
   case 64:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_64BYTES;
   case 128:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_128BYTES;
   case 256:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_256BYTES;
   case 512:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_512BYTES;
   case 1024:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_1024BYTES;
   case 2048:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_2048BYTES;
   case 4096:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES;
-    break;
+    return COFF::IMAGE_SCN_ALIGN_4096BYTES;
   case 8192:
-    Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES;
-    break;
-  default:
-    llvm_unreachable("unsupported section alignment");
+    return COFF::IMAGE_SCN_ALIGN_8192BYTES;
+  }
+  llvm_unreachable("unsupported section alignment");
+}
+
+/// This function takes a section data object from the assembler
+/// and creates the associated COFF section staging object.
+void WinCOFFObjectWriter::defineSection(const MCSectionCOFF &MCSec) {
+  COFFSection *Section = createSection(MCSec.getSectionName());
+  COFFSymbol *Symbol = createSymbol(MCSec.getSectionName());
+  Section->Symbol = Symbol;
+  Symbol->Section = Section;
+  Symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
+
+  // Create a COMDAT symbol if needed.
+  if (MCSec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
+    if (const MCSymbol *S = MCSec.getCOMDATSymbol()) {
+      COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
+      if (COMDATSymbol->Section)
+        report_fatal_error("two sections have the same comdat");
+      COMDATSymbol->Section = Section;
+    }
   }
 
+  // In this case the auxiliary symbol is a Section Definition.
+  Symbol->Aux.resize(1);
+  Symbol->Aux[0] = {};
+  Symbol->Aux[0].AuxType = ATSectionDefinition;
+  Symbol->Aux[0].Aux.SectionDefinition.Selection = MCSec.getSelection();
+
+  // Set section alignment.
+  Section->Header.Characteristics = MCSec.getCharacteristics();
+  Section->Header.Characteristics |= getAlignment(MCSec);
+
   // Bind internal COFF section to MC section.
-  coff_section->MCSection = &Sec;
-  SectionMap[&Sec] = coff_section;
+  Section->MCSection = &MCSec;
+  SectionMap[&MCSec] = Section;
 }
 
 static uint64_t getSymbolValue(const MCSymbol &Symbol,
@@ -368,25 +342,25 @@ COFFSymbol *WinCOFFObjectWriter::getLinkedSymbol(const MCSymbol &Symbol) {
 
 /// This function takes a symbol data object from the assembler
 /// and creates the associated COFF symbol staging object.
-void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &Symbol,
+void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &MCSym,
                                        MCAssembler &Assembler,
                                        const MCAsmLayout &Layout) {
-  COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
-  const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
+  COFFSymbol *Sym = GetOrCreateCOFFSymbol(&MCSym);
+  const MCSymbol *Base = Layout.getBaseSymbol(MCSym);
   COFFSection *Sec = nullptr;
   if (Base && Base->getFragment()) {
     Sec = SectionMap[Base->getFragment()->getParent()];
-    if (coff_symbol->Section && coff_symbol->Section != Sec)
+    if (Sym->Section && Sym->Section != Sec)
       report_fatal_error("conflicting sections for symbol");
   }
 
   COFFSymbol *Local = nullptr;
-  if (cast<MCSymbolCOFF>(Symbol).isWeakExternal()) {
-    coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
+  if (cast<MCSymbolCOFF>(MCSym).isWeakExternal()) {
+    Sym->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
 
-    COFFSymbol *WeakDefault = getLinkedSymbol(Symbol);
+    COFFSymbol *WeakDefault = getLinkedSymbol(MCSym);
     if (!WeakDefault) {
-      std::string WeakName = (".weak." + Symbol.getName() + ".default").str();
+      std::string WeakName = (".weak." + MCSym.getName() + ".default").str();
       WeakDefault = createSymbol(WeakName);
       if (!Sec)
         WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
@@ -395,41 +369,41 @@ void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &Symbol,
       Local = WeakDefault;
     }
 
-    coff_symbol->Other = WeakDefault;
+    Sym->Other = WeakDefault;
 
     // Setup the Weak External auxiliary symbol.
-    coff_symbol->Aux.resize(1);
-    memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
-    coff_symbol->Aux[0].AuxType = ATWeakExternal;
-    coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
-    coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
+    Sym->Aux.resize(1);
+    memset(&Sym->Aux[0], 0, sizeof(Sym->Aux[0]));
+    Sym->Aux[0].AuxType = ATWeakExternal;
+    Sym->Aux[0].Aux.WeakExternal.TagIndex = 0;
+    Sym->Aux[0].Aux.WeakExternal.Characteristics =
         COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
   } else {
     if (!Base)
-      coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
+      Sym->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
     else
-      coff_symbol->Section = Sec;
-    Local = coff_symbol;
+      Sym->Section = Sec;
+    Local = Sym;
   }
 
   if (Local) {
-    Local->Data.Value = getSymbolValue(Symbol, Layout);
+    Local->Data.Value = getSymbolValue(MCSym, Layout);
 
-    const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(Symbol);
+    const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(MCSym);
     Local->Data.Type = SymbolCOFF.getType();
     Local->Data.StorageClass = SymbolCOFF.getClass();
 
     // If no storage class was specified in the streamer, define it here.
     if (Local->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
-      bool IsExternal = Symbol.isExternal() ||
-                        (!Symbol.getFragment() && !Symbol.isVariable());
+      bool IsExternal = MCSym.isExternal() ||
+                        (!MCSym.getFragment() && !MCSym.isVariable());
 
       Local->Data.StorageClass = IsExternal ? COFF::IMAGE_SYM_CLASS_EXTERNAL
                                             : COFF::IMAGE_SYM_CLASS_STATIC;
     }
   }
 
-  coff_symbol->MC = &Symbol;
+  Sym->MC = &MCSym;
 }
 
 // Maximum offsets for different string table entry encodings.
@@ -459,24 +433,25 @@ static void encodeBase64StringEntry(char *Buffer, uint64_t Value) {
 }
 
 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
-  if (S.Name.size() > COFF::NameSize) {
-    uint64_t StringTableEntry = Strings.getOffset(S.Name);
-
-    if (StringTableEntry <= Max7DecimalOffset) {
-      SmallVector<char, COFF::NameSize> Buffer;
-      Twine('/').concat(Twine(StringTableEntry)).toVector(Buffer);
-      assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2);
-
-      std::memcpy(S.Header.Name, Buffer.data(), Buffer.size());
-    } else if (StringTableEntry <= MaxBase64Offset) {
-      // Starting with 10,000,000, offsets are encoded as base64.
-      encodeBase64StringEntry(S.Header.Name, StringTableEntry);
-    } else {
-      report_fatal_error("COFF string table is greater than 64 GB.");
-    }
-  } else {
+  if (S.Name.size() <= COFF::NameSize) {
     std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
+    return;
   }
+
+  uint64_t StringTableEntry = Strings.getOffset(S.Name);
+  if (StringTableEntry <= Max7DecimalOffset) {
+    SmallVector<char, COFF::NameSize> Buffer;
+    Twine('/').concat(Twine(StringTableEntry)).toVector(Buffer);
+    assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2);
+    std::memcpy(S.Header.Name, Buffer.data(), Buffer.size());
+    return;
+  }
+  if (StringTableEntry <= MaxBase64Offset) {
+    // Starting with 10,000,000, offsets are encoded as base64.
+    encodeBase64StringEntry(S.Header.Name, StringTableEntry);
+    return;
+  }
+  report_fatal_error("COFF string table is greater than 64 GB.");
 }
 
 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
@@ -583,18 +558,37 @@ void WinCOFFObjectWriter::WriteAuxiliarySymbols(
   }
 }
 
-void WinCOFFObjectWriter::writeSectionHeader(const COFF::section &S) {
-  writeBytes(StringRef(S.Name, COFF::NameSize));
-
-  writeLE32(S.VirtualSize);
-  writeLE32(S.VirtualAddress);
-  writeLE32(S.SizeOfRawData);
-  writeLE32(S.PointerToRawData);
-  writeLE32(S.PointerToRelocations);
-  writeLE32(S.PointerToLineNumbers);
-  writeLE16(S.NumberOfRelocations);
-  writeLE16(S.NumberOfLineNumbers);
-  writeLE32(S.Characteristics);
+// Write the section header.
+void WinCOFFObjectWriter::writeSectionHeaders() {
+  // Section numbers must be monotonically increasing in the section
+  // header, but our Sections array is not sorted by section number,
+  // so make a copy of Sections and sort it.
+  std::vector<COFFSection *> Arr;
+  for (auto &Section : Sections)
+    Arr.push_back(Section.get());
+  std::sort(Arr.begin(), Arr.end(),
+            [](const COFFSection *A, const COFFSection *B) {
+              return A->Number < B->Number;
+            });
+
+  for (auto &Section : Arr) {
+    if (Section->Number == -1)
+      continue;
+
+    COFF::section &S = Section->Header;
+    if (Section->Relocations.size() >= 0xffff)
+      S.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
+    writeBytes(StringRef(S.Name, COFF::NameSize));
+    writeLE32(S.VirtualSize);
+    writeLE32(S.VirtualAddress);
+    writeLE32(S.SizeOfRawData);
+    writeLE32(S.PointerToRawData);
+    writeLE32(S.PointerToRelocations);
+    writeLE32(S.PointerToLineNumbers);
+    writeLE16(S.NumberOfRelocations);
+    writeLE16(S.NumberOfLineNumbers);
+    writeLE32(S.Characteristics);
+  }
 }
 
 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
@@ -603,6 +597,87 @@ void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
   writeLE16(R.Type);
 }
 
+// Write MCSec's contents. What this function does is essentially
+// "Asm.writeSectionData(&MCSec, Layout)", but it's a bit complicated
+// because it needs to compute a CRC.
+uint32_t WinCOFFObjectWriter::writeSectionContents(MCAssembler &Asm,
+                                                   const MCAsmLayout &Layout,
+                                                   const MCSection &MCSec) {
+  // Save the contents of the section to a temporary buffer, we need this
+  // to CRC the data before we dump it into the object file.
+  SmallVector<char, 128> Buf;
+  raw_svector_ostream VecOS(Buf);
+  raw_pwrite_stream &OldStream = getStream();
+
+  // Redirect the output stream to our buffer and fill our buffer with
+  // the section data.
+  setStream(VecOS);
+  Asm.writeSectionData(&MCSec, Layout);
+
+  // Reset the stream back to what it was before.
+  setStream(OldStream);
+
+  // Write the section contents to the object file.
+  getStream() << Buf;
+
+  // Calculate our CRC with an initial value of '0', this is not how
+  // JamCRC is specified but it aligns with the expected output.
+  JamCRC JC(/*Init=*/0);
+  JC.update(Buf);
+  return JC.getCRC();
+}
+
+void WinCOFFObjectWriter::writeSection(MCAssembler &Asm,
+                                       const MCAsmLayout &Layout,
+                                       const COFFSection &Sec,
+                                       const MCSection &MCSec) {
+  if (Sec.Number == -1)
+    return;
+
+  // Write the section contents.
+  if (Sec.Header.PointerToRawData != 0) {
+    assert(getStream().tell() <= Sec.Header.PointerToRawData &&
+           "Section::PointerToRawData is insane!");
+
+    unsigned PaddingSize = Sec.Header.PointerToRawData - getStream().tell();
+    assert(PaddingSize < 4 &&
+           "Should only need at most three bytes of padding!");
+    WriteZeros(PaddingSize);
+
+    uint32_t CRC = writeSectionContents(Asm, Layout, MCSec);
+
+    // Update the section definition auxiliary symbol to record the CRC.
+    COFFSection *Sec = SectionMap[&MCSec];
+    COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux;
+    assert(AuxSyms.size() == 1 && AuxSyms[0].AuxType == ATSectionDefinition);
+    AuxSymbol &SecDef = AuxSyms[0];
+    SecDef.Aux.SectionDefinition.CheckSum = CRC;
+  }
+
+  // Write relocations for this section.
+  if (Sec.Relocations.empty()) {
+    assert(Sec.Header.PointerToRelocations == 0 &&
+           "Section::PointerToRelocations is insane!");
+    return;
+  }
+
+  assert(getStream().tell() == Sec.Header.PointerToRelocations &&
+         "Section::PointerToRelocations is insane!");
+
+  if (Sec.Relocations.size() >= 0xffff) {
+    // In case of overflow, write actual relocation count as first
+    // relocation. Including the synthetic reloc itself (+ 1).
+    COFF::relocation R;
+    R.VirtualAddress = Sec.Relocations.size() + 1;
+    R.SymbolTableIndex = 0;
+    R.Type = 0;
+    WriteRelocation(R);
+  }
+
+  for (const auto &Relocation : Sec.Relocations)
+    WriteRelocation(Relocation.Data);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // MCObjectWriter interface implementations
 
@@ -632,23 +707,6 @@ bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
                                                                 InSet, IsPCRel);
 }
 
-bool WinCOFFObjectWriter::isWeak(const MCSymbol &Sym) const {
-  if (!Sym.isExternal())
-    return false;
-
-  if (!Sym.isInSection())
-    return false;
-
-  const auto &Sec = cast<MCSectionCOFF>(Sym.getSection());
-  if (!Sec.getCOMDATSymbol())
-    return false;
-
-  // It looks like for COFF it is invalid to replace a reference to a global
-  // in a comdat with a reference to a local.
-  // FIXME: Add a specification reference if available.
-  return true;
-}
-
 void WinCOFFObjectWriter::recordRelocation(
     MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment,
     const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) {
@@ -668,13 +726,13 @@ void WinCOFFObjectWriter::recordRelocation(
     return;
   }
 
-  MCSection *Section = Fragment->getParent();
+  MCSection *MCSec = Fragment->getParent();
 
   // Mark this symbol as requiring an entry in the symbol table.
-  assert(SectionMap.find(Section) != SectionMap.end() &&
+  assert(SectionMap.find(MCSec) != SectionMap.end() &&
          "Section must already have been defined in executePostLayoutBinding!");
 
-  COFFSection *coff_section = SectionMap[Section];
+  COFFSection *Sec = SectionMap[MCSec];
   const MCSymbolRefExpr *SymB = Target.getSymB();
   bool CrossSection = false;
 
@@ -796,46 +854,31 @@ void WinCOFFObjectWriter::recordRelocation(
     FixedValue = 0;
 
   if (TargetObjectWriter->recordRelocation(Fixup))
-    coff_section->Relocations.push_back(Reloc);
+    Sec->Relocations.push_back(Reloc);
 }
 
-void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
-                                      const MCAsmLayout &Layout) {
-  size_t SectionsSize = Sections.size();
-  if (SectionsSize > static_cast<size_t>(INT32_MAX))
-    report_fatal_error(
-        "PE COFF object files can't have more than 2147483647 sections");
-
-  // Assign symbol and section indexes and offsets.
-  int32_t NumberOfSections = static_cast<int32_t>(SectionsSize);
-
-  UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
-
-  // Assign section numbers.
-  size_t Number = 1;
-  for (const auto &Section : Sections) {
-    Section->Number = Number;
-    Section->Symbol->Data.SectionNumber = Number;
-    Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number;
-    ++Number;
-  }
-
-  Header.NumberOfSections = NumberOfSections;
-  Header.NumberOfSymbols = 0;
+static std::time_t getTime() {
+  std::time_t Now = time(nullptr);
+  if (Now < 0 || !isUInt<32>(Now))
+    return UINT32_MAX;
+  return Now;
+}
 
+// Create .file symbols.
+void WinCOFFObjectWriter::createFileSymbols(MCAssembler &Asm) {
   for (const std::string &Name : Asm.getFileNames()) {
     // round up to calculate the number of auxiliary symbols required
     unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
     unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize;
 
-    COFFSymbol *file = createSymbol(".file");
-    file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
-    file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
-    file->Aux.resize(Count);
+    COFFSymbol *File = createSymbol(".file");
+    File->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
+    File->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
+    File->Aux.resize(Count);
 
     unsigned Offset = 0;
     unsigned Length = Name.size();
-    for (auto &Aux : file->Aux) {
+    for (auto &Aux : File->Aux) {
       Aux.AuxType = ATFile;
 
       if (Length > SymbolSize) {
@@ -850,6 +893,109 @@ void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
       Offset += SymbolSize;
     }
   }
+}
+
+static bool isAssociative(const COFFSection &Section) {
+  return Section.Symbol->Aux[0].Aux.SectionDefinition.Selection ==
+         COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
+}
+
+void WinCOFFObjectWriter::assignSectionNumbers() {
+  size_t I = 1;
+  auto Assign = [&](COFFSection &Section) {
+    Section.Number = I;
+    Section.Symbol->Data.SectionNumber = I;
+    Section.Symbol->Aux[0].Aux.SectionDefinition.Number = I;
+    ++I;
+  };
+
+  // Although it is not explicitly requested by the Microsoft COFF spec,
+  // we should avoid emitting forward associative section references,
+  // because MSVC link.exe as of 2017 cannot handle that.
+  for (const std::unique_ptr<COFFSection> &Section : Sections)
+    if (!isAssociative(*Section))
+      Assign(*Section);
+  for (const std::unique_ptr<COFFSection> &Section : Sections)
+    if (isAssociative(*Section))
+      Assign(*Section);
+}
+
+// Assign file offsets to COFF object file structures.
+void WinCOFFObjectWriter::assignFileOffsets(MCAssembler &Asm,
+                                            const MCAsmLayout &Layout) {
+  unsigned Offset = getInitialOffset();
+
+  Offset += UseBigObj ? COFF::Header32Size : COFF::Header16Size;
+  Offset += COFF::SectionSize * Header.NumberOfSections;
+
+  for (const auto &Section : Asm) {
+    COFFSection *Sec = SectionMap[&Section];
+
+    if (Sec->Number == -1)
+      continue;
+
+    Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
+
+    if (IsPhysicalSection(Sec)) {
+      // Align the section data to a four byte boundary.
+      Offset = alignTo(Offset, 4);
+      Sec->Header.PointerToRawData = Offset;
+
+      Offset += Sec->Header.SizeOfRawData;
+    }
+
+    if (!Sec->Relocations.empty()) {
+      bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
+
+      if (RelocationsOverflow) {
+        // Signal overflow by setting NumberOfRelocations to max value. Actual
+        // size is found in reloc #0. Microsoft tools understand this.
+        Sec->Header.NumberOfRelocations = 0xffff;
+      } else {
+        Sec->Header.NumberOfRelocations = Sec->Relocations.size();
+      }
+      Sec->Header.PointerToRelocations = Offset;
+
+      if (RelocationsOverflow) {
+        // Reloc #0 will contain actual count, so make room for it.
+        Offset += COFF::RelocationSize;
+      }
+
+      Offset += COFF::RelocationSize * Sec->Relocations.size();
+
+      for (auto &Relocation : Sec->Relocations) {
+        assert(Relocation.Symb->getIndex() != -1);
+        Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
+      }
+    }
+
+    assert(Sec->Symbol->Aux.size() == 1 &&
+           "Section's symbol must have one aux!");
+    AuxSymbol &Aux = Sec->Symbol->Aux[0];
+    assert(Aux.AuxType == ATSectionDefinition &&
+           "Section's symbol's aux symbol must be a Section Definition!");
+    Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
+    Aux.Aux.SectionDefinition.NumberOfRelocations =
+        Sec->Header.NumberOfRelocations;
+    Aux.Aux.SectionDefinition.NumberOfLinenumbers =
+        Sec->Header.NumberOfLineNumbers;
+  }
+
+  Header.PointerToSymbolTable = Offset;
+}
+
+void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
+                                      const MCAsmLayout &Layout) {
+  if (Sections.size() > INT32_MAX)
+    report_fatal_error(
+        "PE COFF object files can't have more than 2147483647 sections");
+
+  UseBigObj = Sections.size() > COFF::MaxNumberOfSections16;
+  Header.NumberOfSections = Sections.size();
+  Header.NumberOfSymbols = 0;
+
+  assignSectionNumbers();
+  createFileSymbols(Asm);
 
   for (auto &Symbol : Symbols) {
     // Update section number & offset for symbols that have them.
@@ -912,78 +1058,12 @@ void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
     Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number;
   }
 
-  // Assign file offsets to COFF object file structures.
-
-  unsigned offset = getInitialOffset();
-
-  if (UseBigObj)
-    offset += COFF::Header32Size;
-  else
-    offset += COFF::Header16Size;
-  offset += COFF::SectionSize * Header.NumberOfSections;
-
-  for (const auto &Section : Asm) {
-    COFFSection *Sec = SectionMap[&Section];
-
-    if (Sec->Number == -1)
-      continue;
-
-    Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
-
-    if (IsPhysicalSection(Sec)) {
-      // Align the section data to a four byte boundary.
-      offset = alignTo(offset, 4);
-      Sec->Header.PointerToRawData = offset;
-
-      offset += Sec->Header.SizeOfRawData;
-    }
-
-    if (Sec->Relocations.size() > 0) {
-      bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
-
-      if (RelocationsOverflow) {
-        // Signal overflow by setting NumberOfRelocations to max value. Actual
-        // size is found in reloc #0. Microsoft tools understand this.
-        Sec->Header.NumberOfRelocations = 0xffff;
-      } else {
-        Sec->Header.NumberOfRelocations = Sec->Relocations.size();
-      }
-      Sec->Header.PointerToRelocations = offset;
-
-      if (RelocationsOverflow) {
-        // Reloc #0 will contain actual count, so make room for it.
-        offset += COFF::RelocationSize;
-      }
-
-      offset += COFF::RelocationSize * Sec->Relocations.size();
-
-      for (auto &Relocation : Sec->Relocations) {
-        assert(Relocation.Symb->getIndex() != -1);
-        Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
-      }
-    }
-
-    assert(Sec->Symbol->Aux.size() == 1 &&
-           "Section's symbol must have one aux!");
-    AuxSymbol &Aux = Sec->Symbol->Aux[0];
-    assert(Aux.AuxType == ATSectionDefinition &&
-           "Section's symbol's aux symbol must be a Section Definition!");
-    Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
-    Aux.Aux.SectionDefinition.NumberOfRelocations =
-        Sec->Header.NumberOfRelocations;
-    Aux.Aux.SectionDefinition.NumberOfLinenumbers =
-        Sec->Header.NumberOfLineNumbers;
-  }
-
-  Header.PointerToSymbolTable = offset;
+  assignFileOffsets(Asm, Layout);
 
   // MS LINK expects to be able to use this timestamp to implement their
   // /INCREMENTAL feature.
   if (Asm.isIncrementalLinkerCompatible()) {
-    std::time_t Now = time(nullptr);
-    if (Now < 0 || !isUInt<32>(Now))
-      Now = UINT32_MAX;
-    Header.TimeDateStamp = Now;
+    Header.TimeDateStamp = getTime();
   } else {
     // Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU.
     Header.TimeDateStamp = 0;
@@ -991,96 +1071,25 @@ void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
 
   // Write it all to disk...
   WriteFileHeader(Header);
+  writeSectionHeaders();
 
-  {
-    sections::iterator i, ie;
-    MCAssembler::iterator j, je;
-
-    for (auto &Section : Sections) {
-      if (Section->Number != -1) {
-        if (Section->Relocations.size() >= 0xffff)
-          Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
-        writeSectionHeader(Section->Header);
-      }
-    }
-
-    SmallVector<char, 128> SectionContents;
-    for (i = Sections.begin(), ie = Sections.end(), j = Asm.begin(),
-        je = Asm.end();
-         (i != ie) && (j != je); ++i, ++j) {
-
-      if ((*i)->Number == -1)
-        continue;
-
-      if ((*i)->Header.PointerToRawData != 0) {
-        assert(getStream().tell() <= (*i)->Header.PointerToRawData &&
-               "Section::PointerToRawData is insane!");
-
-        unsigned SectionDataPadding =
-            (*i)->Header.PointerToRawData - getStream().tell();
-        assert(SectionDataPadding < 4 &&
-               "Should only need at most three bytes of padding!");
-
-        WriteZeros(SectionDataPadding);
-
-        // Save the contents of the section to a temporary buffer, we need this
-        // to CRC the data before we dump it into the object file.
-        SectionContents.clear();
-        raw_svector_ostream VecOS(SectionContents);
-        raw_pwrite_stream &OldStream = getStream();
-        // Redirect the output stream to our buffer.
-        setStream(VecOS);
-        // Fill our buffer with the section data.
-        Asm.writeSectionData(&*j, Layout);
-        // Reset the stream back to what it was before.
-        setStream(OldStream);
-
-        // Calculate our CRC with an initial value of '0', this is not how
-        // JamCRC is specified but it aligns with the expected output.
-        JamCRC JC(/*Init=*/0x00000000U);
-        JC.update(SectionContents);
-
-        // Write the section contents to the object file.
-        getStream() << SectionContents;
-
-        // Update the section definition auxiliary symbol to record the CRC.
-        COFFSection *Sec = SectionMap[&*j];
-        COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux;
-        assert(AuxSyms.size() == 1 &&
-               AuxSyms[0].AuxType == ATSectionDefinition);
-        AuxSymbol &SecDef = AuxSyms[0];
-        SecDef.Aux.SectionDefinition.CheckSum = JC.getCRC();
-      }
-
-      if ((*i)->Relocations.size() > 0) {
-        assert(getStream().tell() == (*i)->Header.PointerToRelocations &&
-               "Section::PointerToRelocations is insane!");
-
-        if ((*i)->Relocations.size() >= 0xffff) {
-          // In case of overflow, write actual relocation count as first
-          // relocation. Including the synthetic reloc itself (+ 1).
-          COFF::relocation r;
-          r.VirtualAddress = (*i)->Relocations.size() + 1;
-          r.SymbolTableIndex = 0;
-          r.Type = 0;
-          WriteRelocation(r);
-        }
-
-        for (const auto &Relocation : (*i)->Relocations)
-          WriteRelocation(Relocation.Data);
-      } else
-        assert((*i)->Header.PointerToRelocations == 0 &&
-               "Section::PointerToRelocations is insane!");
-    }
-  }
+  // Write section contents.
+  sections::iterator I = Sections.begin();
+  sections::iterator IE = Sections.end();
+  MCAssembler::iterator J = Asm.begin();
+  MCAssembler::iterator JE = Asm.end();
+  for (; I != IE && J != JE; ++I, ++J)
+    writeSection(Asm, Layout, **I, *J);
 
   assert(getStream().tell() == Header.PointerToSymbolTable &&
          "Header::PointerToSymbolTable is insane!");
 
+  // Write a symbol table.
   for (auto &Symbol : Symbols)
     if (Symbol->getIndex() != -1)
       WriteSymbol(*Symbol);
 
+  // Write a string table, which completes the entire COFF file.
   Strings.write(getStream());
 }
 
diff --git a/lib/MC/WinCOFFStreamer.cpp b/lib/MC/WinCOFFStreamer.cpp
index 6383d8794030..c26d87f36f83 100644
--- a/lib/MC/WinCOFFStreamer.cpp
+++ b/lib/MC/WinCOFFStreamer.cpp
@@ -1,4 +1,4 @@
-//===-- llvm/MC/WinCOFFStreamer.cpp -----------------------------*- C++ -*-===//
+//===- llvm/MC/WinCOFFStreamer.cpp ----------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -11,32 +11,36 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAsmBackend.h"
-#include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCObjectStreamer.h"
 #include "llvm/MC/MCSection.h"
-#include "llvm/MC/MCSectionCOFF.h"
-#include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbolCOFF.h"
-#include "llvm/MC/MCValue.h"
 #include "llvm/MC/MCWinCOFFStreamer.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/COFF.h"
-#include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
-#include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/SMLoc.h"
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "WinCOFFStreamer"
 
-namespace llvm {
 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB,
                                      MCCodeEmitter &CE, raw_pwrite_stream &OS)
     : MCObjectStreamer(Context, MAB, OS, &CE), CurSymbol(nullptr) {}
@@ -75,10 +79,9 @@ void MCWinCOFFStreamer::InitSections(bool NoExecStack) {
   SwitchSection(getContext().getObjectFileInfo()->getTextSection());
 }
 
-void MCWinCOFFStreamer::EmitLabel(MCSymbol *S) {
+void MCWinCOFFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) {
   auto *Symbol = cast<MCSymbolCOFF>(S);
-  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
-  MCObjectStreamer::EmitLabel(Symbol);
+  MCObjectStreamer::EmitLabel(Symbol, Loc);
 }
 
 void MCWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
@@ -275,10 +278,6 @@ void MCWinCOFFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
   llvm_unreachable("not implemented");
 }
 
-void MCWinCOFFStreamer::EmitFileDirective(StringRef Filename) {
-  getAssembler().addFileName(Filename);
-}
-
 // TODO: Implement this if you want to emit .comment section in COFF obj files.
 void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) {
   llvm_unreachable("not implemented");
@@ -295,5 +294,3 @@ void MCWinCOFFStreamer::FinishImpl() {
 void MCWinCOFFStreamer::Error(const Twine &Msg) const {
   getContext().reportError(SMLoc(), Msg);
 }
-}
-