vendor/llvm-project/llvmorg-10-init-17466-ge26a78e7085

29 files changed, 709 insertions, 782 deletions

diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 6f160e491cea5..6b4b45eb8effa 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -569,26 +569,6 @@ void ELFWriter::writeSymbol(SymbolTableWriter &Writer, uint32_t StringIndex,
                      IsReserved);
 }
 
-// True if the assembler knows nothing about the final value of the symbol.
-// This doesn't cover the comdat issues, since in those cases the assembler
-// can at least know that all symbols in the section will move together.
-static bool isWeak(const MCSymbolELF &Sym) {
-  if (Sym.getType() == ELF::STT_GNU_IFUNC)
-    return true;
-
-  switch (Sym.getBinding()) {
-  default:
-    llvm_unreachable("Unknown binding");
-  case ELF::STB_LOCAL:
-    return false;
-  case ELF::STB_GLOBAL:
-    return false;
-  case ELF::STB_WEAK:
-  case ELF::STB_GNU_UNIQUE:
-    return true;
-  }
-}
-
 bool ELFWriter::isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
                            bool Used, bool Renamed) {
   if (Symbol.isVariable()) {
@@ -615,9 +595,6 @@ bool ELFWriter::isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
     return false;
   }
 
-  if (Symbol.isUndefined() && !Symbol.isBindingSet())
-    return false;
-
   if (Symbol.isTemporary())
     return false;
 
@@ -1537,7 +1514,8 @@ bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
   const auto &SymA = cast<MCSymbolELF>(SA);
   if (IsPCRel) {
     assert(!InSet);
-    if (isWeak(SymA))
+    if (SymA.getBinding() != ELF::STB_LOCAL ||
+        SymA.getType() == ELF::STT_GNU_IFUNC)
       return false;
   }
   return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
diff --git a/llvm/lib/MC/MCAsmBackend.cpp b/llvm/lib/MC/MCAsmBackend.cpp
index b800e9caee22a..cf110345df3de 100644
--- a/llvm/lib/MC/MCAsmBackend.cpp
+++ b/llvm/lib/MC/MCAsmBackend.cpp
@@ -9,7 +9,6 @@
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/STLExtras.h"
-#include "llvm/MC/MCCodePadder.h"
 #include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCFixupKindInfo.h"
 #include "llvm/MC/MCMachObjectWriter.h"
@@ -23,8 +22,7 @@
 
 using namespace llvm;
 
-MCAsmBackend::MCAsmBackend(support::endianness Endian)
-    : CodePadder(new MCCodePadder()), Endian(Endian) {}
+MCAsmBackend::MCAsmBackend(support::endianness Endian) : Endian(Endian) {}
 
 MCAsmBackend::~MCAsmBackend() = default;
 
@@ -113,25 +111,3 @@ bool MCAsmBackend::fixupNeedsRelaxationAdvanced(
     return true;
   return fixupNeedsRelaxation(Fixup, Value, DF, Layout);
 }
-
-void MCAsmBackend::handleCodePaddingBasicBlockStart(
-    MCObjectStreamer *OS, const MCCodePaddingContext &Context) {
-  CodePadder->handleBasicBlockStart(OS, Context);
-}
-
-void MCAsmBackend::handleCodePaddingBasicBlockEnd(
-    const MCCodePaddingContext &Context) {
-  CodePadder->handleBasicBlockEnd(Context);
-}
-
-void MCAsmBackend::handleCodePaddingInstructionBegin(const MCInst &Inst) {
-  CodePadder->handleInstructionBegin(Inst);
-}
-
-void MCAsmBackend::handleCodePaddingInstructionEnd(const MCInst &Inst) {
-  CodePadder->handleInstructionEnd(Inst);
-}
-
-bool MCAsmBackend::relaxFragment(MCPaddingFragment *PF, MCAsmLayout &Layout) {
-  return CodePadder->relaxFragment(PF, Layout);
-}
diff --git a/llvm/lib/MC/MCAsmInfo.cpp b/llvm/lib/MC/MCAsmInfo.cpp
index 71e51e320f8bd..420dbaa80ae90 100644
--- a/llvm/lib/MC/MCAsmInfo.cpp
+++ b/llvm/lib/MC/MCAsmInfo.cpp
@@ -100,7 +100,7 @@ MCAsmInfo::getExprForFDESymbol(const MCSymbol *Sym,
   return MCBinaryExpr::createSub(Res, PC, Context);
 }
 
-static bool isAcceptableChar(char C) {
+bool MCAsmInfo::isAcceptableChar(char C) const {
   return (C >= 'a' && C <= 'z') || (C >= 'A' && C <= 'Z') ||
          (C >= '0' && C <= '9') || C == '_' || C == '$' || C == '.' || C == '@';
 }
diff --git a/llvm/lib/MC/MCAsmInfoELF.cpp b/llvm/lib/MC/MCAsmInfoELF.cpp
index a5e8aff7f129d..9b8b8db794f0d 100644
--- a/llvm/lib/MC/MCAsmInfoELF.cpp
+++ b/llvm/lib/MC/MCAsmInfoELF.cpp
@@ -21,8 +21,6 @@ using namespace llvm;
 void MCAsmInfoELF::anchor() {}
 
 MCSection *MCAsmInfoELF::getNonexecutableStackSection(MCContext &Ctx) const {
-  if (!UsesNonexecutableStackSection)
-    return nullptr;
   return Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0);
 }
 
diff --git a/llvm/lib/MC/MCAsmInfoXCOFF.cpp b/llvm/lib/MC/MCAsmInfoXCOFF.cpp
index 65fe8848e20fb..c51cdff59fa0a 100644
--- a/llvm/lib/MC/MCAsmInfoXCOFF.cpp
+++ b/llvm/lib/MC/MCAsmInfoXCOFF.cpp
@@ -26,10 +26,11 @@ MCAsmInfoXCOFF::MCAsmInfoXCOFF() {
   SupportsQuotedNames = false;
 }
 
-bool MCAsmInfoXCOFF::isValidUnquotedName(StringRef Name) const {
-  // FIXME: Remove this function when we stop using "TOC[TC0]" as a symbol name.
-  if (Name.equals("TOC[TC0]"))
+bool MCAsmInfoXCOFF::isAcceptableChar(char C) const {
+  // QualName is allowed for a MCSymbolXCOFF, and
+  // QualName contains '[' and ']'.
+  if (C == '[' || C == ']')
     return true;
 
-  return MCAsmInfo::isValidUnquotedName(Name);
+  return MCAsmInfo::isAcceptableChar(C);
 }
diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp
index 2d9c2cb21255b..5d369503995b3 100644
--- a/llvm/lib/MC/MCAsmStreamer.cpp
+++ b/llvm/lib/MC/MCAsmStreamer.cpp
@@ -77,6 +77,8 @@ public:
     assert(InstPrinter);
     if (IsVerboseAsm)
         InstPrinter->setCommentStream(CommentStream);
+    if (Assembler->getBackendPtr())
+      setAllowAutoPadding(Assembler->getBackend().allowAutoPadding());
   }
 
   MCAssembler &getAssembler() { return *Assembler; }
@@ -164,7 +166,8 @@ public:
   void EmitCOFFSectionIndex(MCSymbol const *Symbol) override;
   void EmitCOFFSecRel32(MCSymbol const *Symbol, uint64_t Offset) override;
   void EmitCOFFImgRel32(MCSymbol const *Symbol, int64_t Offset) override;
-  void EmitXCOFFLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
+  void EmitXCOFFLocalCommonSymbol(MCSymbol *LabelSym, uint64_t Size,
+                                  MCSymbol *CsectSym,
                                   unsigned ByteAlign) override;
   void emitELFSize(MCSymbol *Symbol, const MCExpr *Value) override;
   void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
@@ -765,16 +768,18 @@ void MCAsmStreamer::EmitCOFFImgRel32(MCSymbol const *Symbol, int64_t Offset) {
 // We need an XCOFF-specific version of this directive as the AIX syntax
 // requires a QualName argument identifying the csect name and storage mapping
 // class to appear before the alignment if we are specifying it.
-void MCAsmStreamer::EmitXCOFFLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
+void MCAsmStreamer::EmitXCOFFLocalCommonSymbol(MCSymbol *LabelSym,
+                                               uint64_t Size,
+                                               MCSymbol *CsectSym,
                                                unsigned ByteAlignment) {
   assert(MAI->getLCOMMDirectiveAlignmentType() == LCOMM::Log2Alignment &&
          "We only support writing log base-2 alignment format with XCOFF.");
   assert(isPowerOf2_32(ByteAlignment) && "Alignment must be a power of 2.");
 
   OS << "\t.lcomm\t";
-  Symbol->print(OS, MAI);
-  OS << ',' << Size;
-  OS << ',' << Symbol->getName();
+  LabelSym->print(OS, MAI);
+  OS << ',' << Size << ',';
+  CsectSym->print(OS, MAI);
   OS << ',' << Log2_32(ByteAlignment);
 
   EmitEOL();
@@ -1941,9 +1946,9 @@ void MCAsmStreamer::EmitInstruction(const MCInst &Inst,
   }
 
   if(getTargetStreamer())
-    getTargetStreamer()->prettyPrintAsm(*InstPrinter, OS, Inst, STI);
+    getTargetStreamer()->prettyPrintAsm(*InstPrinter, 0, Inst, STI, OS);
   else
-    InstPrinter->printInst(&Inst, OS, "", STI);
+    InstPrinter->printInst(&Inst, 0, "", STI, OS);
 
   StringRef Comments = CommentToEmit;
   if (Comments.size() && Comments.back() != '\n')
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index cf42fe85b8e5d..b30137aafb8d1 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -68,10 +68,6 @@ 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");
-STATISTIC(PaddingFragmentsRelaxations,
-          "Number of Padding Fragments relaxations");
-STATISTIC(PaddingFragmentsBytes,
-          "Total size of all padding from adding Fragments");
 
 } // end namespace stats
 } // end anonymous namespace
@@ -167,10 +163,6 @@ bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
   if (!Symbol.isTemporary())
     return true;
 
-  // Absolute temporary labels are never visible.
-  if (!Symbol.isInSection())
-    return false;
-
   if (Symbol.isUsedInReloc())
     return true;
 
@@ -313,8 +305,8 @@ uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
   case MCFragment::FT_LEB:
     return cast<MCLEBFragment>(F).getContents().size();
 
-  case MCFragment::FT_Padding:
-    return cast<MCPaddingFragment>(F).getSize();
+  case MCFragment::FT_BoundaryAlign:
+    return cast<MCBoundaryAlignFragment>(F).getSize();
 
   case MCFragment::FT_SymbolId:
     return 4;
@@ -580,6 +572,7 @@ static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
     unsigned VSize = FF.getValueSize();
     const unsigned MaxChunkSize = 16;
     char Data[MaxChunkSize];
+    assert(0 < VSize && VSize <= MaxChunkSize && "Illegal fragment fill size");
     // Duplicate V into Data as byte vector to reduce number of
     // writes done. As such, do endian conversion here.
     for (unsigned I = 0; I != VSize; ++I) {
@@ -612,7 +605,7 @@ static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
     break;
   }
 
-  case MCFragment::FT_Padding: {
+  case MCFragment::FT_BoundaryAlign: {
     if (!Asm.getBackend().writeNopData(OS, FragmentSize))
       report_fatal_error("unable to write nop sequence of " +
                          Twine(FragmentSize) + " bytes");
@@ -935,20 +928,6 @@ bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
   return true;
 }
 
-bool MCAssembler::relaxPaddingFragment(MCAsmLayout &Layout,
-                                       MCPaddingFragment &PF) {
-  assert(getBackendPtr() && "Expected assembler backend");
-  uint64_t OldSize = PF.getSize();
-  if (!getBackend().relaxFragment(&PF, Layout))
-    return false;
-  uint64_t NewSize = PF.getSize();
-
-  ++stats::PaddingFragmentsRelaxations;
-  stats::PaddingFragmentsBytes += NewSize;
-  stats::PaddingFragmentsBytes -= OldSize;
-  return true;
-}
-
 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
   uint64_t OldSize = LF.getContents().size();
   int64_t Value;
@@ -969,6 +948,72 @@ bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
   return OldSize != LF.getContents().size();
 }
 
+/// Check if the branch crosses the boundary.
+///
+/// \param StartAddr start address of the fused/unfused branch.
+/// \param Size size of the fused/unfused branch.
+/// \param BoundaryAlignment alignment requirement of the branch.
+/// \returns true if the branch cross the boundary.
+static bool mayCrossBoundary(uint64_t StartAddr, uint64_t Size,
+                             Align BoundaryAlignment) {
+  uint64_t EndAddr = StartAddr + Size;
+  return (StartAddr >> Log2(BoundaryAlignment)) !=
+         ((EndAddr - 1) >> Log2(BoundaryAlignment));
+}
+
+/// Check if the branch is against the boundary.
+///
+/// \param StartAddr start address of the fused/unfused branch.
+/// \param Size size of the fused/unfused branch.
+/// \param BoundaryAlignment alignment requirement of the branch.
+/// \returns true if the branch is against the boundary.
+static bool isAgainstBoundary(uint64_t StartAddr, uint64_t Size,
+                              Align BoundaryAlignment) {
+  uint64_t EndAddr = StartAddr + Size;
+  return (EndAddr & (BoundaryAlignment.value() - 1)) == 0;
+}
+
+/// Check if the branch needs padding.
+///
+/// \param StartAddr start address of the fused/unfused branch.
+/// \param Size size of the fused/unfused branch.
+/// \param BoundaryAlignment alignment requirement of the branch.
+/// \returns true if the branch needs padding.
+static bool needPadding(uint64_t StartAddr, uint64_t Size,
+                        Align BoundaryAlignment) {
+  return mayCrossBoundary(StartAddr, Size, BoundaryAlignment) ||
+         isAgainstBoundary(StartAddr, Size, BoundaryAlignment);
+}
+
+bool MCAssembler::relaxBoundaryAlign(MCAsmLayout &Layout,
+                                     MCBoundaryAlignFragment &BF) {
+  // The MCBoundaryAlignFragment that doesn't emit NOP should not be relaxed.
+  if (!BF.canEmitNops())
+    return false;
+
+  uint64_t AlignedOffset = Layout.getFragmentOffset(BF.getNextNode());
+  uint64_t AlignedSize = 0;
+  const MCFragment *F = BF.getNextNode();
+  // If the branch is unfused, it is emitted into one fragment, otherwise it is
+  // emitted into two fragments at most, the next MCBoundaryAlignFragment(if
+  // exists) also marks the end of the branch.
+  for (auto i = 0, N = BF.isFused() ? 2 : 1;
+       i != N && !isa<MCBoundaryAlignFragment>(F); ++i, F = F->getNextNode()) {
+    AlignedSize += computeFragmentSize(Layout, *F);
+  }
+  uint64_t OldSize = BF.getSize();
+  AlignedOffset -= OldSize;
+  Align BoundaryAlignment = BF.getAlignment();
+  uint64_t NewSize = needPadding(AlignedOffset, AlignedSize, BoundaryAlignment)
+                         ? offsetToAlignment(AlignedOffset, BoundaryAlignment)
+                         : 0U;
+  if (NewSize == OldSize)
+    return false;
+  BF.setSize(NewSize);
+  Layout.invalidateFragmentsFrom(&BF);
+  return true;
+}
+
 bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
                                      MCDwarfLineAddrFragment &DF) {
   MCContext &Context = Layout.getAssembler().getContext();
@@ -1085,8 +1130,9 @@ bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) {
     case MCFragment::FT_LEB:
       RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
       break;
-    case MCFragment::FT_Padding:
-      RelaxedFrag = relaxPaddingFragment(Layout, *cast<MCPaddingFragment>(I));
+    case MCFragment::FT_BoundaryAlign:
+      RelaxedFrag =
+          relaxBoundaryAlign(Layout, *cast<MCBoundaryAlignFragment>(I));
       break;
     case MCFragment::FT_CVInlineLines:
       RelaxedFrag =
@@ -1124,8 +1170,8 @@ void MCAssembler::finishLayout(MCAsmLayout &Layout) {
   // The layout is done. Mark every fragment as valid.
   for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
     MCSection &Section = *Layout.getSectionOrder()[i];
-    Layout.getFragmentOffset(&*Section.rbegin());
-    computeFragmentSize(Layout, *Section.rbegin());
+    Layout.getFragmentOffset(&*Section.getFragmentList().rbegin());
+    computeFragmentSize(Layout, *Section.getFragmentList().rbegin());
   }
   getBackend().finishLayout(*this, Layout);
 }
diff --git a/llvm/lib/MC/MCCodePadder.cpp b/llvm/lib/MC/MCCodePadder.cpp
deleted file mode 100644
index 27a62f95a5294..0000000000000
--- a/llvm/lib/MC/MCCodePadder.cpp
+++ /dev/null
@@ -1,370 +0,0 @@
-//===- MCCodePadder.cpp - Target MC Code Padder ---------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/MC/MCAsmLayout.h"
-#include "llvm/MC/MCCodePadder.h"
-#include "llvm/MC/MCObjectStreamer.h"
-#include <algorithm>
-#include <limits>
-#include <numeric>
-
-using namespace llvm;
-
-//---------------------------------------------------------------------------
-// MCCodePadder
-//
-
-MCCodePadder::~MCCodePadder() {
-  for (auto *Policy : CodePaddingPolicies)
-    delete Policy;
-}
-
-bool MCCodePadder::addPolicy(MCCodePaddingPolicy *Policy) {
-  assert(Policy && "Policy must be valid");
-  return CodePaddingPolicies.insert(Policy).second;
-}
-
-void MCCodePadder::handleBasicBlockStart(MCObjectStreamer *OS,
-                                         const MCCodePaddingContext &Context) {
-  assert(OS != nullptr && "OS must be valid");
-  assert(this->OS == nullptr && "Still handling another basic block");
-  this->OS = OS;
-
-  ArePoliciesActive = usePoliciesForBasicBlock(Context);
-
-  bool InsertionPoint = basicBlockRequiresInsertionPoint(Context);
-  assert((!InsertionPoint ||
-          OS->getCurrentFragment()->getKind() != MCFragment::FT_Align) &&
-         "Cannot insert padding nops right after an alignment fragment as it "
-         "will ruin the alignment");
-
-  uint64_t PoliciesMask = MCPaddingFragment::PFK_None;
-  if (ArePoliciesActive) {
-    PoliciesMask = std::accumulate(
-        CodePaddingPolicies.begin(), CodePaddingPolicies.end(),
-        MCPaddingFragment::PFK_None,
-        [&Context](uint64_t Mask,
-                   const MCCodePaddingPolicy *Policy) -> uint64_t {
-          return Policy->basicBlockRequiresPaddingFragment(Context)
-                     ? (Mask | Policy->getKindMask())
-                     : Mask;
-        });
-  }
-
-  if (InsertionPoint || PoliciesMask != MCPaddingFragment::PFK_None) {
-    MCPaddingFragment *PaddingFragment = OS->getOrCreatePaddingFragment();
-    if (InsertionPoint)
-      PaddingFragment->setAsInsertionPoint();
-    PaddingFragment->setPaddingPoliciesMask(
-        PaddingFragment->getPaddingPoliciesMask() | PoliciesMask);
-  }
-}
-
-void MCCodePadder::handleBasicBlockEnd(const MCCodePaddingContext &Context) {
-  assert(this->OS != nullptr && "Not handling a basic block");
-  OS = nullptr;
-}
-
-void MCCodePadder::handleInstructionBegin(const MCInst &Inst) {
-  if (!OS)
-    return; // instruction was emitted outside a function
-
-  assert(CurrHandledInstFragment == nullptr && "Can't start handling an "
-                                               "instruction while still "
-                                               "handling another instruction");
-
-  bool InsertionPoint = instructionRequiresInsertionPoint(Inst);
-  assert((!InsertionPoint ||
-          OS->getCurrentFragment()->getKind() != MCFragment::FT_Align) &&
-         "Cannot insert padding nops right after an alignment fragment as it "
-         "will ruin the alignment");
-
-  uint64_t PoliciesMask = MCPaddingFragment::PFK_None;
-  if (ArePoliciesActive) {
-    PoliciesMask = std::accumulate(
-        CodePaddingPolicies.begin(), CodePaddingPolicies.end(),
-        MCPaddingFragment::PFK_None,
-        [&Inst](uint64_t Mask, const MCCodePaddingPolicy *Policy) -> uint64_t {
-          return Policy->instructionRequiresPaddingFragment(Inst)
-                     ? (Mask | Policy->getKindMask())
-                     : Mask;
-        });
-  }
-  MCFragment *CurrFragment = OS->getCurrentFragment();
-  // CurrFragment can be a previously created MCPaddingFragment. If so, let's
-  // update it with the information we have, such as the instruction that it
-  // should point to.
-  bool needToUpdateCurrFragment =
-      CurrFragment != nullptr &&
-      CurrFragment->getKind() == MCFragment::FT_Padding;
-  if (InsertionPoint || PoliciesMask != MCPaddingFragment::PFK_None ||
-      needToUpdateCurrFragment) {
-    // temporarily holding the fragment as CurrHandledInstFragment, to be
-    // updated after the instruction will be written
-    CurrHandledInstFragment = OS->getOrCreatePaddingFragment();
-    if (InsertionPoint)
-      CurrHandledInstFragment->setAsInsertionPoint();
-    CurrHandledInstFragment->setPaddingPoliciesMask(
-        CurrHandledInstFragment->getPaddingPoliciesMask() | PoliciesMask);
-  }
-}
-
-void MCCodePadder::handleInstructionEnd(const MCInst &Inst) {
-  if (!OS)
-    return; // instruction was emitted outside a function
-  if (CurrHandledInstFragment == nullptr)
-    return;
-
-  MCFragment *InstFragment = OS->getCurrentFragment();
-  if (MCDataFragment *InstDataFragment =
-          dyn_cast_or_null<MCDataFragment>(InstFragment))
-    // Inst is a fixed size instruction and was encoded into a MCDataFragment.
-    // Let the fragment hold it and its size. Its size is the current size of
-    // the data fragment, as the padding fragment was inserted right before it
-    // and nothing was written yet except Inst
-    CurrHandledInstFragment->setInstAndInstSize(
-        Inst, InstDataFragment->getContents().size());
-  else if (MCRelaxableFragment *InstRelaxableFragment =
-               dyn_cast_or_null<MCRelaxableFragment>(InstFragment))
-    // Inst may be relaxed and its size may vary.
-    // Let the fragment hold the instruction and the MCRelaxableFragment
-    // that's holding it.
-    CurrHandledInstFragment->setInstAndInstFragment(Inst,
-                                                    InstRelaxableFragment);
-  else
-    llvm_unreachable("After encoding an instruction current fragment must be "
-                     "either a MCDataFragment or a MCRelaxableFragment");
-
-  CurrHandledInstFragment = nullptr;
-}
-
-MCPFRange &MCCodePadder::getJurisdiction(MCPaddingFragment *Fragment,
-                                         MCAsmLayout &Layout) {
-  auto JurisdictionLocation = FragmentToJurisdiction.find(Fragment);
-  if (JurisdictionLocation != FragmentToJurisdiction.end())
-    return JurisdictionLocation->second;
-
-  MCPFRange Jurisdiction;
-
-  // Forward scanning the fragments in this section, starting from the given
-  // fragments, and adding relevant MCPaddingFragments to the Jurisdiction
-  for (MCFragment *CurrFragment = Fragment; CurrFragment != nullptr;
-       CurrFragment = CurrFragment->getNextNode()) {
-
-    MCPaddingFragment *CurrPaddingFragment =
-        dyn_cast<MCPaddingFragment>(CurrFragment);
-    if (CurrPaddingFragment == nullptr)
-      continue;
-
-    if (CurrPaddingFragment != Fragment &&
-        CurrPaddingFragment->isInsertionPoint())
-      // Found next insertion point Fragment. From now on it's its jurisdiction.
-      break;
-    for (const auto *Policy : CodePaddingPolicies) {
-      if (CurrPaddingFragment->hasPaddingPolicy(Policy->getKindMask())) {
-        Jurisdiction.push_back(CurrPaddingFragment);
-        break;
-      }
-    }
-  }
-
-  auto InsertionResult =
-      FragmentToJurisdiction.insert(std::make_pair(Fragment, Jurisdiction));
-  assert(InsertionResult.second &&
-         "Insertion to FragmentToJurisdiction failed");
-  return InsertionResult.first->second;
-}
-
-uint64_t MCCodePadder::getMaxWindowSize(MCPaddingFragment *Fragment,
-                                        MCAsmLayout &Layout) {
-  auto MaxFragmentSizeLocation = FragmentToMaxWindowSize.find(Fragment);
-  if (MaxFragmentSizeLocation != FragmentToMaxWindowSize.end())
-    return MaxFragmentSizeLocation->second;
-
-  MCPFRange &Jurisdiction = getJurisdiction(Fragment, Layout);
-  uint64_t JurisdictionMask = MCPaddingFragment::PFK_None;
-  for (const auto *Protege : Jurisdiction)
-    JurisdictionMask |= Protege->getPaddingPoliciesMask();
-
-  uint64_t MaxFragmentSize = UINT64_C(0);
-  for (const auto *Policy : CodePaddingPolicies)
-    if ((JurisdictionMask & Policy->getKindMask()) !=
-        MCPaddingFragment::PFK_None)
-      MaxFragmentSize = std::max(MaxFragmentSize, Policy->getWindowSize());
-
-  auto InsertionResult =
-      FragmentToMaxWindowSize.insert(std::make_pair(Fragment, MaxFragmentSize));
-  assert(InsertionResult.second &&
-         "Insertion to FragmentToMaxWindowSize failed");
-  return InsertionResult.first->second;
-}
-
-bool MCCodePadder::relaxFragment(MCPaddingFragment *Fragment,
-                                 MCAsmLayout &Layout) {
-  if (!Fragment->isInsertionPoint())
-    return false;
-  uint64_t OldSize = Fragment->getSize();
-
-  uint64_t MaxWindowSize = getMaxWindowSize(Fragment, Layout);
-  if (MaxWindowSize == UINT64_C(0))
-    return false;
-  assert(isPowerOf2_64(MaxWindowSize) &&
-         "MaxWindowSize must be an integer power of 2");
-  uint64_t SectionAlignment = Fragment->getParent()->getAlignment();
-  assert(isPowerOf2_64(SectionAlignment) &&
-         "SectionAlignment must be an integer power of 2");
-
-  MCPFRange &Jurisdiction = getJurisdiction(Fragment, Layout);
-  uint64_t OptimalSize = UINT64_C(0);
-  double OptimalWeight = std::numeric_limits<double>::max();
-  uint64_t MaxFragmentSize = MaxWindowSize - UINT16_C(1);
-  for (uint64_t Size = UINT64_C(0); Size <= MaxFragmentSize; ++Size) {
-    Fragment->setSize(Size);
-    Layout.invalidateFragmentsFrom(Fragment);
-    double SizeWeight = 0.0;
-    // The section is guaranteed to be aligned to SectionAlignment, but that
-    // doesn't guarantee the exact section offset w.r.t. the policies window
-    // size.
-    // As a concrete example, the section could be aligned to 16B, but a
-    // policy's window size can be 32B. That means that the section actual start
-    // address can either be 0mod32 or 16mod32. The said policy will act
-    // differently for each case, so we need to take both into consideration.
-    for (uint64_t Offset = UINT64_C(0); Offset < MaxWindowSize;
-         Offset += SectionAlignment) {
-      double OffsetWeight = std::accumulate(
-          CodePaddingPolicies.begin(), CodePaddingPolicies.end(), 0.0,
-          [&Jurisdiction, &Offset, &Layout](
-              double Weight, const MCCodePaddingPolicy *Policy) -> double {
-            double PolicyWeight =
-                Policy->computeRangePenaltyWeight(Jurisdiction, Offset, Layout);
-            assert(PolicyWeight >= 0.0 && "A penalty weight must be positive");
-            return Weight + PolicyWeight;
-          });
-      SizeWeight = std::max(SizeWeight, OffsetWeight);
-    }
-    if (SizeWeight < OptimalWeight) {
-      OptimalWeight = SizeWeight;
-      OptimalSize = Size;
-    }
-    if (OptimalWeight == 0.0)
-      break;
-  }
-
-  Fragment->setSize(OptimalSize);
-  Layout.invalidateFragmentsFrom(Fragment);
-  return OldSize != OptimalSize;
-}
-
-//---------------------------------------------------------------------------
-// MCCodePaddingPolicy
-//
-
-uint64_t MCCodePaddingPolicy::getNextFragmentOffset(const MCFragment *Fragment,
-                                                    const MCAsmLayout &Layout) {
-  assert(Fragment != nullptr && "Fragment cannot be null");
-  MCFragment const *NextFragment = Fragment->getNextNode();
-  return NextFragment == nullptr
-             ? Layout.getSectionAddressSize(Fragment->getParent())
-             : Layout.getFragmentOffset(NextFragment);
-}
-
-uint64_t
-MCCodePaddingPolicy::getFragmentInstByte(const MCPaddingFragment *Fragment,
-                                         MCAsmLayout &Layout) const {
-  uint64_t InstByte = getNextFragmentOffset(Fragment, Layout);
-  if (InstByteIsLastByte)
-    InstByte += Fragment->getInstSize() - UINT64_C(1);
-  return InstByte;
-}
-
-uint64_t
-MCCodePaddingPolicy::computeWindowEndAddress(const MCPaddingFragment *Fragment,
-                                             uint64_t Offset,
-                                             MCAsmLayout &Layout) const {
-  uint64_t InstByte = getFragmentInstByte(Fragment, Layout);
-  return alignTo(InstByte + UINT64_C(1) + Offset, WindowSize) - Offset;
-}
-
-double MCCodePaddingPolicy::computeRangePenaltyWeight(
-    const MCPFRange &Range, uint64_t Offset, MCAsmLayout &Layout) const {
-
-  SmallVector<MCPFRange, 8> Windows;
-  SmallVector<MCPFRange, 8>::iterator CurrWindowLocation = Windows.end();
-  for (const MCPaddingFragment *Fragment : Range) {
-    if (!Fragment->hasPaddingPolicy(getKindMask()))
-      continue;
-    uint64_t FragmentWindowEndAddress =
-        computeWindowEndAddress(Fragment, Offset, Layout);
-    if (CurrWindowLocation == Windows.end() ||
-        FragmentWindowEndAddress !=
-            computeWindowEndAddress(*CurrWindowLocation->begin(), Offset,
-                                    Layout)) {
-      // next window is starting
-      Windows.push_back(MCPFRange());
-      CurrWindowLocation = Windows.end() - 1;
-    }
-    CurrWindowLocation->push_back(Fragment);
-  }
-
-  if (Windows.empty())
-    return 0.0;
-
-  double RangeWeight = 0.0;
-  SmallVector<MCPFRange, 8>::iterator I = Windows.begin();
-  RangeWeight += computeFirstWindowPenaltyWeight(*I, Offset, Layout);
-  ++I;
-  RangeWeight += std::accumulate(
-      I, Windows.end(), 0.0,
-      [this, &Layout, &Offset](double Weight, MCPFRange &Window) -> double {
-        return Weight += computeWindowPenaltyWeight(Window, Offset, Layout);
-      });
-  return RangeWeight;
-}
-
-double MCCodePaddingPolicy::computeFirstWindowPenaltyWeight(
-    const MCPFRange &Window, uint64_t Offset, MCAsmLayout &Layout) const {
-  if (Window.empty())
-    return 0.0;
-  uint64_t WindowEndAddress =
-      computeWindowEndAddress(*Window.begin(), Offset, Layout);
-
-  MCPFRange FullWindowFirstPart; // will hold all the fragments that are in the
-								 // same window as the fragments in the given
-								 // window but their penalty weight should not
-								 // be added
-  for (const MCFragment *Fragment = (*Window.begin())->getPrevNode();
-       Fragment != nullptr; Fragment = Fragment->getPrevNode()) {
-    const MCPaddingFragment *PaddingNopFragment =
-        dyn_cast<MCPaddingFragment>(Fragment);
-    if (PaddingNopFragment == nullptr ||
-        !PaddingNopFragment->hasPaddingPolicy(getKindMask()))
-      continue;
-    if (WindowEndAddress !=
-        computeWindowEndAddress(PaddingNopFragment, Offset, Layout))
-      break;
-
-    FullWindowFirstPart.push_back(PaddingNopFragment);
-  }
-
-  std::reverse(FullWindowFirstPart.begin(), FullWindowFirstPart.end());
-  double FullWindowFirstPartWeight =
-      computeWindowPenaltyWeight(FullWindowFirstPart, Offset, Layout);
-
-  MCPFRange FullWindow(
-      FullWindowFirstPart); // will hold all the fragments that are in the
-                            // same window as the fragments in the given
-                            // window, whether their weight should be added
-                            // or not
-  FullWindow.append(Window.begin(), Window.end());
-  double FullWindowWeight =
-      computeWindowPenaltyWeight(FullWindow, Offset, Layout);
-
-  assert(FullWindowWeight >= FullWindowFirstPartWeight &&
-         "More fragments necessarily means bigger weight");
-  return FullWindowWeight - FullWindowFirstPartWeight;
-}
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index a69ee19e1a1ae..a6417113fd384 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -15,6 +15,7 @@
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/COFF.h"
 #include "llvm/BinaryFormat/ELF.h"
+#include "llvm/BinaryFormat/XCOFF.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCCodeView.h"
 #include "llvm/MC/MCDwarf.h"
@@ -550,13 +551,15 @@ MCSectionXCOFF *MCContext::getXCOFFSection(StringRef Section,
 
   // Otherwise, return a new section.
   StringRef CachedName = Entry.first.SectionName;
+  MCSymbol *QualName = getOrCreateSymbol(
+      CachedName + "[" + XCOFF::getMappingClassString(SMC) + "]");
 
   MCSymbol *Begin = nullptr;
   if (BeginSymName)
     Begin = createTempSymbol(BeginSymName, false);
 
-  MCSectionXCOFF *Result = new (XCOFFAllocator.Allocate())
-      MCSectionXCOFF(CachedName, SMC, Type, SC, Kind, Begin);
+  MCSectionXCOFF *Result = new (XCOFFAllocator.Allocate()) MCSectionXCOFF(
+      CachedName, SMC, Type, SC, Kind, cast<MCSymbolXCOFF>(QualName), Begin);
   Entry.second = Result;
 
   auto *F = new MCDataFragment();
diff --git a/llvm/lib/MC/MCDisassembler/Disassembler.cpp b/llvm/lib/MC/MCDisassembler/Disassembler.cpp
index 21bdc2eaea3e4..ff56695e8cc46 100644
--- a/llvm/lib/MC/MCDisassembler/Disassembler.cpp
+++ b/llvm/lib/MC/MCDisassembler/Disassembler.cpp
@@ -24,6 +24,7 @@
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSchedule.h"
 #include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/MC/MCTargetOptions.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FormattedStream.h"
 #include "llvm/Support/TargetRegistry.h"
@@ -56,8 +57,10 @@ LLVMCreateDisasmCPUFeatures(const char *TT, const char *CPU,
   if (!MRI)
     return nullptr;
 
+  MCTargetOptions MCOptions;
   // Get the assembler info needed to setup the MCContext.
-  std::unique_ptr<const MCAsmInfo> MAI(TheTarget->createMCAsmInfo(*MRI, TT));
+  std::unique_ptr<const MCAsmInfo> MAI(
+      TheTarget->createMCAsmInfo(*MRI, TT, MCOptions));
   if (!MAI)
     return nullptr;
 
@@ -260,8 +263,7 @@ size_t LLVMDisasmInstruction(LLVMDisasmContextRef DCR, uint8_t *Bytes,
   MCDisassembler::DecodeStatus S;
   SmallVector<char, 64> InsnStr;
   raw_svector_ostream Annotations(InsnStr);
-  S = DisAsm->getInstruction(Inst, Size, Data, PC,
-                             /*REMOVE*/ nulls(), Annotations);
+  S = DisAsm->getInstruction(Inst, Size, Data, PC, Annotations);
   switch (S) {
   case MCDisassembler::Fail:
   case MCDisassembler::SoftFail:
@@ -274,7 +276,8 @@ size_t LLVMDisasmInstruction(LLVMDisasmContextRef DCR, uint8_t *Bytes,
     SmallVector<char, 64> InsnStr;
     raw_svector_ostream OS(InsnStr);
     formatted_raw_ostream FormattedOS(OS);
-    IP->printInst(&Inst, FormattedOS, AnnotationsStr, *DC->getSubtargetInfo());
+    IP->printInst(&Inst, PC, AnnotationsStr, *DC->getSubtargetInfo(),
+                  FormattedOS);
 
     if (DC->getOptions() & LLVMDisassembler_Option_PrintLatency)
       emitLatency(DC, Inst);
diff --git a/llvm/lib/MC/MCDisassembler/MCDisassembler.cpp b/llvm/lib/MC/MCDisassembler/MCDisassembler.cpp
index 063f7e706024b..373916fbed785 100644
--- a/llvm/lib/MC/MCDisassembler/MCDisassembler.cpp
+++ b/llvm/lib/MC/MCDisassembler/MCDisassembler.cpp
@@ -16,9 +16,10 @@ using namespace llvm;
 
 MCDisassembler::~MCDisassembler() = default;
 
-MCDisassembler::DecodeStatus MCDisassembler::onSymbolStart(
-    StringRef Name, uint64_t &Size, ArrayRef<uint8_t> Bytes, uint64_t Address,
-    raw_ostream &VStream, raw_ostream &CStream) const {
+MCDisassembler::DecodeStatus
+MCDisassembler::onSymbolStart(StringRef Name, uint64_t &Size,
+                              ArrayRef<uint8_t> Bytes, uint64_t Address,
+                              raw_ostream &CStream) const {
   Size = 0;
   return MCDisassembler::Success;
 }
@@ -27,18 +28,16 @@ bool MCDisassembler::tryAddingSymbolicOperand(MCInst &Inst, int64_t Value,
                                               uint64_t Address, bool IsBranch,
                                               uint64_t Offset,
                                               uint64_t InstSize) const {
-  raw_ostream &cStream = CommentStream ? *CommentStream : nulls();
   if (Symbolizer)
-    return Symbolizer->tryAddingSymbolicOperand(Inst, cStream, Value, Address,
-                                                IsBranch, Offset, InstSize);
+    return Symbolizer->tryAddingSymbolicOperand(
+        Inst, *CommentStream, Value, Address, IsBranch, Offset, InstSize);
   return false;
 }
 
 void MCDisassembler::tryAddingPcLoadReferenceComment(int64_t Value,
                                                      uint64_t Address) const {
-  raw_ostream &cStream = CommentStream ? *CommentStream : nulls();
   if (Symbolizer)
-    Symbolizer->tryAddingPcLoadReferenceComment(cStream, Value, Address);
+    Symbolizer->tryAddingPcLoadReferenceComment(*CommentStream, Value, Address);
 }
 
 void MCDisassembler::setSymbolizer(std::unique_ptr<MCSymbolizer> Symzer) {
diff --git a/llvm/lib/MC/MCDwarf.cpp b/llvm/lib/MC/MCDwarf.cpp
index bcc7c45afc01b..b4b3c9956cc2d 100644
--- a/llvm/lib/MC/MCDwarf.cpp
+++ b/llvm/lib/MC/MCDwarf.cpp
@@ -1701,7 +1701,8 @@ void FrameEmitterImpl::EmitFDE(const MCSymbol &cieStart,
         MakeStartMinusEndExpr(Streamer, SectionStart, cieStart, 0);
     emitAbsValue(Streamer, offset, 4);
   } else {
-    Streamer.EmitSymbolValue(&cieStart, 4);
+    Streamer.EmitSymbolValue(&cieStart, 4,
+                             asmInfo->needsDwarfSectionOffsetDirective());
   }
 
   // PC Begin
diff --git a/llvm/lib/MC/MCELFStreamer.cpp b/llvm/lib/MC/MCELFStreamer.cpp
index fa2133078bfea..0a0c30df9c07f 100644
--- a/llvm/lib/MC/MCELFStreamer.cpp
+++ b/llvm/lib/MC/MCELFStreamer.cpp
@@ -106,9 +106,10 @@ void MCELFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) {
     Symbol->setType(ELF::STT_TLS);
 }
 
-void MCELFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc, MCFragment *F) {
+void MCELFStreamer::EmitLabelAtPos(MCSymbol *S, SMLoc Loc, MCFragment *F,
+                                   uint64_t Offset) {
   auto *Symbol = cast<MCSymbolELF>(S);
-  MCObjectStreamer::EmitLabel(Symbol, Loc, F);
+  MCObjectStreamer::EmitLabelAtPos(Symbol, Loc, F, Offset);
 
   const MCSectionELF &Section =
       static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
@@ -307,10 +308,6 @@ void MCELFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
     EmitLabel(Symbol);
     EmitZeros(Size);
 
-    // Update the maximum alignment of the section if necessary.
-    if (ByteAlignment > Section.getAlignment())
-      Section.setAlignment(Align(ByteAlignment));
-
     SwitchSection(P.first, P.second);
   } else {
     if(Symbol->declareCommon(Size, ByteAlignment))
diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index 813c00f6f3bb3..7f25fd4e90a78 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -601,7 +601,7 @@ static bool canFold(const MCAssembler *Asm, const MCSymbolRefExpr *A,
 /// and
 ///   Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
 ///
-/// This routine attempts to aggresively fold the operands such that the result
+/// This routine attempts to aggressively fold the operands such that the result
 /// is representable in an MCValue, but may not always succeed.
 ///
 /// \returns True on success, false if the result is not representable in an
diff --git a/llvm/lib/MC/MCFragment.cpp b/llvm/lib/MC/MCFragment.cpp
index ae5bd65507bc9..a96b8e86aed3c 100644
--- a/llvm/lib/MC/MCFragment.cpp
+++ b/llvm/lib/MC/MCFragment.cpp
@@ -232,13 +232,11 @@ uint64_t llvm::computeBundlePadding(const MCAssembler &Assembler,
 
 void ilist_alloc_traits<MCFragment>::deleteNode(MCFragment *V) { V->destroy(); }
 
-MCFragment::~MCFragment() = default;
-
 MCFragment::MCFragment(FragmentType Kind, bool HasInstructions,
                        MCSection *Parent)
-    : Kind(Kind), HasInstructions(HasInstructions), LayoutOrder(0),
-      Parent(Parent), Atom(nullptr), Offset(~UINT64_C(0)) {
-  if (Parent && !isDummy())
+    : Parent(Parent), Atom(nullptr), Offset(~UINT64_C(0)), LayoutOrder(0),
+      Kind(Kind), HasInstructions(HasInstructions) {
+  if (Parent && !isa<MCDummyFragment>(*this))
     Parent->getFragmentList().push_back(this);
 }
 
@@ -277,8 +275,8 @@ void MCFragment::destroy() {
     case FT_LEB:
       delete cast<MCLEBFragment>(this);
       return;
-    case FT_Padding:
-      delete cast<MCPaddingFragment>(this);
+    case FT_BoundaryAlign:
+      delete cast<MCBoundaryAlignFragment>(this);
       return;
     case FT_SymbolId:
       delete cast<MCSymbolIdFragment>(this);
@@ -324,7 +322,7 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
   case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
   case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
   case MCFragment::FT_LEB:   OS << "MCLEBFragment"; break;
-  case MCFragment::FT_Padding: OS << "MCPaddingFragment"; break;
+  case MCFragment::FT_BoundaryAlign: OS<<"MCBoundaryAlignFragment"; break;
   case MCFragment::FT_SymbolId:    OS << "MCSymbolIdFragment"; break;
   case MCFragment::FT_CVInlineLines: OS << "MCCVInlineLineTableFragment"; break;
   case MCFragment::FT_CVDefRange: OS << "MCCVDefRangeTableFragment"; break;
@@ -333,13 +331,13 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
 
   OS << "<MCFragment " << (const void *)this << " LayoutOrder:" << LayoutOrder
      << " Offset:" << Offset << " HasInstructions:" << hasInstructions();
-  if (const MCEncodedFragment *EF = dyn_cast<MCEncodedFragment>(this))
+  if (const auto *EF = dyn_cast<MCEncodedFragment>(this))
     OS << " BundlePadding:" << static_cast<unsigned>(EF->getBundlePadding());
   OS << ">";
 
   switch (getKind()) {
   case MCFragment::FT_Align: {
-    const MCAlignFragment *AF = cast<MCAlignFragment>(this);
+    const auto *AF = cast<MCAlignFragment>(this);
     if (AF->hasEmitNops())
       OS << " (emit nops)";
     OS << "\n       ";
@@ -349,7 +347,7 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
     break;
   }
   case MCFragment::FT_Data:  {
-    const MCDataFragment *DF = cast<MCDataFragment>(this);
+    const auto *DF = cast<MCDataFragment>(this);
     OS << "\n       ";
     OS << " Contents:[";
     const SmallVectorImpl<char> &Contents = DF->getContents();
@@ -372,7 +370,7 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
     break;
   }
   case MCFragment::FT_CompactEncodedInst: {
-    const MCCompactEncodedInstFragment *CEIF =
+    const auto *CEIF =
       cast<MCCompactEncodedInstFragment>(this);
     OS << "\n       ";
     OS << " Contents:[";
@@ -385,60 +383,60 @@ LLVM_DUMP_METHOD void MCFragment::dump() const {
     break;
   }
   case MCFragment::FT_Fill:  {
-    const MCFillFragment *FF = cast<MCFillFragment>(this);
+    const auto *FF = cast<MCFillFragment>(this);
     OS << " Value:" << static_cast<unsigned>(FF->getValue())
        << " ValueSize:" << static_cast<unsigned>(FF->getValueSize())
        << " NumValues:" << FF->getNumValues();
     break;
   }
   case MCFragment::FT_Relaxable:  {
-    const MCRelaxableFragment *F = cast<MCRelaxableFragment>(this);
+    const auto *F = cast<MCRelaxableFragment>(this);
     OS << "\n       ";
     OS << " Inst:";
     F->getInst().dump_pretty(OS);
     break;
   }
   case MCFragment::FT_Org:  {
-    const MCOrgFragment *OF = cast<MCOrgFragment>(this);
+    const auto *OF = cast<MCOrgFragment>(this);
     OS << "\n       ";
     OS << " Offset:" << OF->getOffset()
        << " Value:" << static_cast<unsigned>(OF->getValue());
     break;
   }
   case MCFragment::FT_Dwarf:  {
-    const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
+    const auto *OF = cast<MCDwarfLineAddrFragment>(this);
     OS << "\n       ";
     OS << " AddrDelta:" << OF->getAddrDelta()
        << " LineDelta:" << OF->getLineDelta();
     break;
   }
   case MCFragment::FT_DwarfFrame:  {
-    const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
+    const auto *CF = cast<MCDwarfCallFrameFragment>(this);
     OS << "\n       ";
     OS << " AddrDelta:" << CF->getAddrDelta();
     break;
   }
   case MCFragment::FT_LEB: {
-    const MCLEBFragment *LF = cast<MCLEBFragment>(this);
+    const auto *LF = cast<MCLEBFragment>(this);
     OS << "\n       ";
     OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
     break;
   }
-  case MCFragment::FT_Padding: {
-    const MCPaddingFragment *F = cast<MCPaddingFragment>(this);
-    OS << "\n       ";
-    OS << " PaddingPoliciesMask:" << F->getPaddingPoliciesMask()
-       << " IsInsertionPoint:" << F->isInsertionPoint()
-       << " Size:" << F->getSize();
-    OS << "\n       ";
-    OS << " Inst:";
-    F->getInst().dump_pretty(OS);
-    OS << " InstSize:" << F->getInstSize();
+  case MCFragment::FT_BoundaryAlign: {
+    const auto *BF = cast<MCBoundaryAlignFragment>(this);
+    if (BF->canEmitNops())
+      OS << " (can emit nops to align";
+    if (BF->isFused())
+      OS << " fused branch)";
+    else
+      OS << " unfused branch)";
     OS << "\n       ";
+    OS << " BoundarySize:" << BF->getAlignment().value()
+       << " Size:" << BF->getSize();
     break;
   }
   case MCFragment::FT_SymbolId: {
-    const MCSymbolIdFragment *F = cast<MCSymbolIdFragment>(this);
+    const auto *F = cast<MCSymbolIdFragment>(this);
     OS << "\n       ";
     OS << " Sym:" << F->getSymbol();
     break;
diff --git a/llvm/lib/MC/MCInstPrinter.cpp b/llvm/lib/MC/MCInstPrinter.cpp
index c5c06f323e680..8bf699279ada4 100644
--- a/llvm/lib/MC/MCInstPrinter.cpp
+++ b/llvm/lib/MC/MCInstPrinter.cpp
@@ -10,7 +10,9 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCInstrInfo.h"
+#include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
@@ -57,6 +59,94 @@ void MCInstPrinter::printAnnotation(raw_ostream &OS, StringRef Annot) {
   }
 }
 
+static bool matchAliasCondition(const MCInst &MI, const MCSubtargetInfo *STI,
+                                const MCRegisterInfo &MRI, unsigned &OpIdx,
+                                const AliasMatchingData &M,
+                                const AliasPatternCond &C) {
+  // Feature tests are special, they don't consume operands.
+  if (C.Kind == AliasPatternCond::K_Feature)
+    return STI->getFeatureBits().test(C.Value);
+  if (C.Kind == AliasPatternCond::K_NegFeature)
+    return !STI->getFeatureBits().test(C.Value);
+
+  // Get and consume an operand.
+  const MCOperand &Opnd = MI.getOperand(OpIdx);
+  ++OpIdx;
+
+  // Check the specific condition for the operand.
+  switch (C.Kind) {
+  case AliasPatternCond::K_Imm:
+    // Operand must be a specific immediate.
+    return Opnd.isImm() && Opnd.getImm() == int32_t(C.Value);
+  case AliasPatternCond::K_Reg:
+    // Operand must be a specific register.
+    return Opnd.isReg() && Opnd.getReg() == C.Value;
+  case AliasPatternCond::K_TiedReg:
+    // Operand must match the register of another operand.
+    return Opnd.isReg() && Opnd.getReg() == MI.getOperand(C.Value).getReg();
+  case AliasPatternCond::K_RegClass:
+    // Operand must be a register in this class. Value is a register class id.
+    return Opnd.isReg() && MRI.getRegClass(C.Value).contains(Opnd.getReg());
+  case AliasPatternCond::K_Custom:
+    // Operand must match some custom criteria.
+    return M.ValidateMCOperand(Opnd, *STI, C.Value);
+  case AliasPatternCond::K_Ignore:
+    // Operand can be anything.
+    return true;
+  case AliasPatternCond::K_Feature:
+  case AliasPatternCond::K_NegFeature:
+    llvm_unreachable("handled earlier");
+  }
+  llvm_unreachable("invalid kind");
+}
+
+const char *MCInstPrinter::matchAliasPatterns(const MCInst *MI,
+                                              const MCSubtargetInfo *STI,
+                                              const AliasMatchingData &M) {
+  // Binary search by opcode. Return false if there are no aliases for this
+  // opcode.
+  auto It = lower_bound(M.OpToPatterns, MI->getOpcode(),
+                        [](const PatternsForOpcode &L, unsigned Opcode) {
+                          return L.Opcode < Opcode;
+                        });
+  if (It == M.OpToPatterns.end() || It->Opcode != MI->getOpcode())
+    return nullptr;
+
+  // Try all patterns for this opcode.
+  uint32_t AsmStrOffset = ~0U;
+  ArrayRef<AliasPattern> Patterns =
+      M.Patterns.slice(It->PatternStart, It->NumPatterns);
+  for (const AliasPattern &P : Patterns) {
+    // Check operand count first.
+    if (MI->getNumOperands() != P.NumOperands)
+      return nullptr;
+
+    // Test all conditions for this pattern.
+    ArrayRef<AliasPatternCond> Conds =
+        M.PatternConds.slice(P.AliasCondStart, P.NumConds);
+    unsigned OpIdx = 0;
+    if (llvm::all_of(Conds, [&](const AliasPatternCond &C) {
+          return matchAliasCondition(*MI, STI, MRI, OpIdx, M, C);
+        })) {
+      // If all conditions matched, use this asm string.
+      AsmStrOffset = P.AsmStrOffset;
+      break;
+    }
+  }
+
+  // If no alias matched, don't print an alias.
+  if (AsmStrOffset == ~0U)
+    return nullptr;
+
+  // Go to offset AsmStrOffset and use the null terminated string there. The
+  // offset should point to the beginning of an alias string, so it should
+  // either be zero or be preceded by a null byte.
+  assert(AsmStrOffset < M.AsmStrings.size() &&
+         (AsmStrOffset == 0 || M.AsmStrings[AsmStrOffset - 1] == '\0') &&
+         "bad asm string offset");
+  return M.AsmStrings.data() + AsmStrOffset;
+}
+
 /// Utility functions to make adding mark ups simpler.
 StringRef MCInstPrinter::markup(StringRef s) const {
   if (getUseMarkup())
diff --git a/llvm/lib/MC/MCObjectFileInfo.cpp b/llvm/lib/MC/MCObjectFileInfo.cpp
index 70c0409ece7a9..d567cc14a8306 100644
--- a/llvm/lib/MC/MCObjectFileInfo.cpp
+++ b/llvm/lib/MC/MCObjectFileInfo.cpp
@@ -40,8 +40,7 @@ static bool useCompactUnwind(const Triple &T) {
     return true;
 
   // And the iOS simulator.
-  if (T.isiOS() &&
-      (T.getArch() == Triple::x86_64 || T.getArch() == Triple::x86))
+  if (T.isiOS() && T.isX86())
     return true;
 
   return false;
@@ -192,7 +191,7 @@ void MCObjectFileInfo::initMachOMCObjectFileInfo(const Triple &T) {
         Ctx->getMachOSection("__LD", "__compact_unwind", MachO::S_ATTR_DEBUG,
                              SectionKind::getReadOnly());
 
-    if (T.getArch() == Triple::x86_64 || T.getArch() == Triple::x86)
+    if (T.isX86())
       CompactUnwindDwarfEHFrameOnly = 0x04000000;  // UNWIND_X86_64_MODE_DWARF
     else if (T.getArch() == Triple::aarch64 || T.getArch() == Triple::aarch64_32)
       CompactUnwindDwarfEHFrameOnly = 0x03000000;  // UNWIND_ARM64_MODE_DWARF
@@ -304,9 +303,14 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T, bool Large) {
   case Triple::mipsel:
   case Triple::mips64:
   case Triple::mips64el:
-    FDECFIEncoding = Ctx->getAsmInfo()->getCodePointerSize() == 4
-                         ? dwarf::DW_EH_PE_sdata4
-                         : dwarf::DW_EH_PE_sdata8;
+    // We cannot use DW_EH_PE_sdata8 for the large PositionIndependent case
+    // since there is no R_MIPS_PC64 relocation (only a 32-bit version).
+    if (PositionIndependent && !Large)
+      FDECFIEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
+    else
+      FDECFIEncoding = Ctx->getAsmInfo()->getCodePointerSize() == 4
+                           ? dwarf::DW_EH_PE_sdata4
+                           : dwarf::DW_EH_PE_sdata8;
     break;
   case Triple::ppc64:
   case Triple::ppc64le:
@@ -463,6 +467,11 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T, bool Large) {
                                              DebugSecType, ELF::SHF_EXCLUDE);
   DwarfRnglistsDWOSection =
       Ctx->getELFSection(".debug_rnglists.dwo", DebugSecType, ELF::SHF_EXCLUDE);
+  DwarfMacinfoDWOSection =
+      Ctx->getELFSection(".debug_macinfo.dwo", DebugSecType, ELF::SHF_EXCLUDE);
+
+  DwarfLoclistsDWOSection =
+      Ctx->getELFSection(".debug_loclists.dwo", DebugSecType, ELF::SHF_EXCLUDE);
 
   // DWP Sections
   DwarfCUIndexSection =
@@ -480,9 +489,6 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(const Triple &T, bool Large) {
       Ctx->getELFSection(".eh_frame", EHSectionType, EHSectionFlags);
 
   StackSizesSection = Ctx->getELFSection(".stack_sizes", ELF::SHT_PROGBITS, 0);
-
-  RemarksSection =
-      Ctx->getELFSection(".remarks", ELF::SHT_PROGBITS, ELF::SHF_EXCLUDE);
 }
 
 void MCObjectFileInfo::initCOFFMCObjectFileInfo(const Triple &T) {
@@ -619,6 +625,11 @@ void MCObjectFileInfo::initCOFFMCObjectFileInfo(const Triple &T) {
       COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
           COFF::IMAGE_SCN_MEM_READ,
       SectionKind::getMetadata(), "debug_macinfo");
+  DwarfMacinfoDWOSection = Ctx->getCOFFSection(
+      ".debug_macinfo.dwo",
+      COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
+          COFF::IMAGE_SCN_MEM_READ,
+      SectionKind::getMetadata(), "debug_macinfo.dwo");
   DwarfInfoDWOSection = Ctx->getCOFFSection(
       ".debug_info.dwo",
       COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
@@ -715,6 +726,11 @@ void MCObjectFileInfo::initCOFFMCObjectFileInfo(const Triple &T) {
                                          COFF::IMAGE_SCN_MEM_READ,
                                      SectionKind::getMetadata());
 
+  GLJMPSection = Ctx->getCOFFSection(".gljmp$y",
+                                     COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
+                                         COFF::IMAGE_SCN_MEM_READ,
+                                     SectionKind::getMetadata());
+
   TLSDataSection = Ctx->getCOFFSection(
       ".tls$", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ |
                    COFF::IMAGE_SCN_MEM_WRITE,
@@ -775,6 +791,10 @@ void MCObjectFileInfo::initXCOFFMCObjectFileInfo(const Triple &T) {
   DataSection = Ctx->getXCOFFSection(
       ".data", XCOFF::StorageMappingClass::XMC_RW, XCOFF::XTY_SD,
       XCOFF::C_HIDEXT, SectionKind::getData());
+
+  ReadOnlySection = Ctx->getXCOFFSection(
+      ".rodata", XCOFF::StorageMappingClass::XMC_RO, XCOFF::XTY_SD,
+      XCOFF::C_HIDEXT, SectionKind::getReadOnly());
 }
 
 void MCObjectFileInfo::InitMCObjectFileInfo(const Triple &TheTriple, bool PIC,
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index 83f6ab8fe332e..3d1358df475f1 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -29,7 +29,10 @@ MCObjectStreamer::MCObjectStreamer(MCContext &Context,
     : MCStreamer(Context),
       Assembler(std::make_unique<MCAssembler>(
           Context, std::move(TAB), std::move(Emitter), std::move(OW))),
-      EmitEHFrame(true), EmitDebugFrame(false) {}
+      EmitEHFrame(true), EmitDebugFrame(false) {
+  if (Assembler->getBackendPtr())
+    setAllowAutoPadding(Assembler->getBackend().allowAutoPadding());
+}
 
 MCObjectStreamer::~MCObjectStreamer() {}
 
@@ -42,20 +45,64 @@ MCAssembler *MCObjectStreamer::getAssemblerPtr() {
   return nullptr;
 }
 
+void MCObjectStreamer::addPendingLabel(MCSymbol* S) {
+  MCSection *CurSection = getCurrentSectionOnly();
+  if (CurSection) {
+    // Register labels that have not yet been assigned to a Section.
+    if (!PendingLabels.empty()) {
+      for (MCSymbol* Sym : PendingLabels)
+        CurSection->addPendingLabel(Sym);
+      PendingLabels.clear();
+    }
+
+    // Add this label to the current Section / Subsection.
+    CurSection->addPendingLabel(S, CurSubsectionIdx);
+
+    // Add this Section to the list of PendingLabelSections.
+    auto SecIt = std::find(PendingLabelSections.begin(),
+                           PendingLabelSections.end(), CurSection);
+    if (SecIt == PendingLabelSections.end())
+      PendingLabelSections.push_back(CurSection);
+  }
+  else
+    // There is no Section / Subsection for this label yet.
+    PendingLabels.push_back(S);
+}
+
 void MCObjectStreamer::flushPendingLabels(MCFragment *F, uint64_t FOffset) {
-  if (PendingLabels.empty())
+  MCSection *CurSection = getCurrentSectionOnly();
+  if (!CurSection) {
+    assert(PendingLabels.empty());
     return;
-  if (!F) {
-    F = new MCDataFragment();
-    MCSection *CurSection = getCurrentSectionOnly();
-    CurSection->getFragmentList().insert(CurInsertionPoint, F);
-    F->setParent(CurSection);
   }
-  for (MCSymbol *Sym : PendingLabels) {
-    Sym->setFragment(F);
-    Sym->setOffset(FOffset);
+  // Register labels that have not yet been assigned to a Section.
+  if (!PendingLabels.empty()) {
+    for (MCSymbol* Sym : PendingLabels)
+      CurSection->addPendingLabel(Sym, CurSubsectionIdx);
+    PendingLabels.clear();
   }
-  PendingLabels.clear();
+
+  // Associate a fragment with this label, either the supplied fragment
+  // or an empty data fragment.
+  if (F)
+    CurSection->flushPendingLabels(F, FOffset, CurSubsectionIdx);
+  else
+    CurSection->flushPendingLabels(nullptr, 0, CurSubsectionIdx);
+}
+
+void MCObjectStreamer::flushPendingLabels() {
+  // Register labels that have not yet been assigned to a Section.
+  if (!PendingLabels.empty()) {
+    MCSection *CurSection = getCurrentSectionOnly();
+    assert(CurSection);
+    for (MCSymbol* Sym : PendingLabels)
+      CurSection->addPendingLabel(Sym, CurSubsectionIdx);
+    PendingLabels.clear();
+  }
+
+  // Assign an empty data fragment to all remaining pending labels.
+  for (MCSection* Section : PendingLabelSections)
+    Section->flushPendingLabels();
 }
 
 // When fixup's offset is a forward declared label, e.g.:
@@ -120,6 +167,7 @@ void MCObjectStreamer::reset() {
   EmitEHFrame = true;
   EmitDebugFrame = false;
   PendingLabels.clear();
+  PendingLabelSections.clear();
   MCStreamer::reset();
 }
 
@@ -167,16 +215,6 @@ MCObjectStreamer::getOrCreateDataFragment(const MCSubtargetInfo *STI) {
   return F;
 }
 
-MCPaddingFragment *MCObjectStreamer::getOrCreatePaddingFragment() {
-  MCPaddingFragment *F =
-      dyn_cast_or_null<MCPaddingFragment>(getCurrentFragment());
-  if (!F) {
-    F = new MCPaddingFragment();
-    insert(F);
-  }
-  return F;
-}
-
 void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {
   Assembler->registerSymbol(Sym);
 }
@@ -243,18 +281,32 @@ void MCObjectStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
     Symbol->setFragment(F);
     Symbol->setOffset(F->getContents().size());
   } else {
-    PendingLabels.push_back(Symbol);
+    // Assign all pending labels to offset 0 within the dummy "pending"
+    // fragment. (They will all be reassigned to a real fragment in
+    // flushPendingLabels())
+    Symbol->setOffset(0);
+    addPendingLabel(Symbol);
   }
 }
 
-void MCObjectStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc, MCFragment *F) {
+// Emit a label at a previously emitted fragment/offset position. This must be
+// within the currently-active section.
+void MCObjectStreamer::EmitLabelAtPos(MCSymbol *Symbol, SMLoc Loc,
+                                      MCFragment *F, uint64_t Offset) {
+  assert(F->getParent() == getCurrentSectionOnly());
+
   MCStreamer::EmitLabel(Symbol, Loc);
   getAssembler().registerSymbol(*Symbol);
   auto *DF = dyn_cast_or_null<MCDataFragment>(F);
-  if (DF)
+  Symbol->setOffset(Offset);
+  if (DF) {
     Symbol->setFragment(F);
-  else
-    PendingLabels.push_back(Symbol);
+  } else {
+    assert(isa<MCDummyFragment>(F) &&
+           "F must either be an MCDataFragment or the pending MCDummyFragment");
+    assert(Offset == 0);
+    addPendingLabel(Symbol);
+  }
 }
 
 void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) {
@@ -288,7 +340,6 @@ void MCObjectStreamer::ChangeSection(MCSection *Section,
 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);
@@ -299,8 +350,9 @@ bool MCObjectStreamer::changeSectionImpl(MCSection *Section,
     report_fatal_error("Cannot evaluate subsection number");
   if (IntSubsection < 0 || IntSubsection > 8192)
     report_fatal_error("Subsection number out of range");
+  CurSubsectionIdx = unsigned(IntSubsection);
   CurInsertionPoint =
-      Section->getSubsectionInsertionPoint(unsigned(IntSubsection));
+      Section->getSubsectionInsertionPoint(CurSubsectionIdx);
   return Created;
 }
 
@@ -315,9 +367,9 @@ bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const {
 
 void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
                                        const MCSubtargetInfo &STI) {
-  getAssembler().getBackend().handleCodePaddingInstructionBegin(Inst);
+  getAssembler().getBackend().alignBranchesBegin(*this, Inst);
   EmitInstructionImpl(Inst, STI);
-  getAssembler().getBackend().handleCodePaddingInstructionEnd(Inst);
+  getAssembler().getBackend().alignBranchesEnd(*this, Inst);
 }
 
 void MCObjectStreamer::EmitInstructionImpl(const MCInst &Inst,
@@ -520,12 +572,6 @@ void MCObjectStreamer::EmitBytes(StringRef Data) {
   MCDataFragment *DF = getOrCreateDataFragment();
   flushPendingLabels(DF, DF->getContents().size());
   DF->getContents().append(Data.begin(), Data.end());
-
-  // EmitBytes might not cover all possible ways we emit data (or could be used
-  // to emit executable code in some cases), but is the best method we have
-  // right now for checking this.
-  MCSection *Sec = getCurrentSectionOnly();
-  Sec->setHasData(true);
 }
 
 void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
@@ -554,16 +600,6 @@ void MCObjectStreamer::emitValueToOffset(const MCExpr *Offset,
   insert(new MCOrgFragment(*Offset, Value, Loc));
 }
 
-void MCObjectStreamer::EmitCodePaddingBasicBlockStart(
-    const MCCodePaddingContext &Context) {
-  getAssembler().getBackend().handleCodePaddingBasicBlockStart(this, Context);
-}
-
-void MCObjectStreamer::EmitCodePaddingBasicBlockEnd(
-    const MCCodePaddingContext &Context) {
-  getAssembler().getBackend().handleCodePaddingBasicBlockEnd(Context);
-}
-
 // Associate DTPRel32 fixup with data and resize data area
 void MCObjectStreamer::EmitDTPRel32Value(const MCExpr *Value) {
   MCDataFragment *DF = getOrCreateDataFragment();
@@ -725,7 +761,9 @@ void MCObjectStreamer::FinishImpl() {
   // Dump out the dwarf file & directory tables and line tables.
   MCDwarfLineTable::Emit(this, getAssembler().getDWARFLinetableParams());
 
+  // Update any remaining pending labels with empty data fragments.
   flushPendingLabels();
+
   resolvePendingFixups();
   getAssembler().Finish();
 }
diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index b59ac08ad6cc4..94a44c1f93b18 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -91,16 +91,13 @@ struct MacroInstantiation {
   SMLoc InstantiationLoc;
 
   /// The buffer where parsing should resume upon instantiation completion.
-  int ExitBuffer;
+  unsigned ExitBuffer;
 
   /// The location where parsing should resume upon instantiation completion.
   SMLoc ExitLoc;
 
   /// The depth of TheCondStack at the start of the instantiation.
   size_t CondStackDepth;
-
-public:
-  MacroInstantiation(SMLoc IL, int EB, SMLoc EL, size_t CondStackDepth);
 };
 
 struct ParseStatementInfo {
@@ -916,13 +913,12 @@ bool AsmParser::Run(bool NoInitialTextSection, bool NoFinalize) {
   // While we have input, parse each statement.
   while (Lexer.isNot(AsmToken::Eof)) {
     ParseStatementInfo Info(&AsmStrRewrites);
-    if (!parseStatement(Info, nullptr))
-      continue;
+    bool Parsed = parseStatement(Info, nullptr);
 
     // If we have a Lexer Error we are on an Error Token. Load in Lexer Error
     // for printing ErrMsg via Lex() only if no (presumably better) parser error
     // exists.
-    if (!hasPendingError() && Lexer.getTok().is(AsmToken::Error)) {
+    if (Parsed && !hasPendingError() && Lexer.getTok().is(AsmToken::Error)) {
       Lex();
     }
 
@@ -930,7 +926,7 @@ bool AsmParser::Run(bool NoInitialTextSection, bool NoFinalize) {
     printPendingErrors();
 
     // Skipping to the next line if needed.
-    if (!getLexer().isAtStartOfStatement())
+    if (Parsed && !getLexer().isAtStartOfStatement())
       eatToEndOfStatement();
   }
 
@@ -2521,11 +2517,6 @@ bool AsmParser::expandMacro(raw_svector_ostream &OS, StringRef Body,
   return false;
 }
 
-MacroInstantiation::MacroInstantiation(SMLoc IL, int EB, SMLoc EL,
-                                       size_t CondStackDepth)
-    : InstantiationLoc(IL), ExitBuffer(EB), ExitLoc(EL),
-      CondStackDepth(CondStackDepth) {}
-
 static bool isOperator(AsmToken::TokenKind kind) {
   switch (kind) {
   default:
@@ -2800,8 +2791,8 @@ bool AsmParser::handleMacroEntry(const MCAsmMacro *M, SMLoc NameLoc) {
 
   // Create the macro instantiation object and add to the current macro
   // instantiation stack.
-  MacroInstantiation *MI = new MacroInstantiation(
-      NameLoc, CurBuffer, getTok().getLoc(), TheCondStack.size());
+  MacroInstantiation *MI = new MacroInstantiation{
+      NameLoc, CurBuffer, getTok().getLoc(), TheCondStack.size()};
   ActiveMacros.push_back(MI);
 
   ++NumOfMacroInstantiations;
@@ -3139,8 +3130,9 @@ bool AsmParser::parseRealValue(const fltSemantics &Semantics, APInt &Res) {
       Value = APFloat::getNaN(Semantics, false, ~0);
     else
       return TokError("invalid floating point literal");
-  } else if (Value.convertFromString(IDVal, APFloat::rmNearestTiesToEven) ==
-             APFloat::opInvalidOp)
+  } else if (errorToBool(
+                 Value.convertFromString(IDVal, APFloat::rmNearestTiesToEven)
+                     .takeError()))
     return TokError("invalid floating point literal");
   if (IsNeg)
     Value.changeSign();
@@ -5545,8 +5537,8 @@ void AsmParser::instantiateMacroLikeBody(MCAsmMacro *M, SMLoc DirectiveLoc,
 
   // Create the macro instantiation object and add to the current macro
   // instantiation stack.
-  MacroInstantiation *MI = new MacroInstantiation(
-      DirectiveLoc, CurBuffer, getTok().getLoc(), TheCondStack.size());
+  MacroInstantiation *MI = new MacroInstantiation{
+      DirectiveLoc, CurBuffer, getTok().getLoc(), TheCondStack.size()};
   ActiveMacros.push_back(MI);
 
   // Jump to the macro instantiation and prime the lexer.
@@ -5813,10 +5805,6 @@ bool AsmParser::parseMSInlineAsm(
     for (unsigned i = 1, e = Info.ParsedOperands.size(); i != e; ++i) {
       MCParsedAsmOperand &Operand = *Info.ParsedOperands[i];
 
-      // Immediate.
-      if (Operand.isImm())
-        continue;
-
       // Register operand.
       if (Operand.isReg() && !Operand.needAddressOf() &&
           !getTargetParser().OmitRegisterFromClobberLists(Operand.getReg())) {
@@ -5836,19 +5824,31 @@ bool AsmParser::parseMSInlineAsm(
       if (!OpDecl)
         continue;
 
+      StringRef Constraint = Operand.getConstraint();
+      if (Operand.isImm()) {
+        // Offset as immediate
+        if (Operand.isOffsetOfLocal())
+          Constraint = "r";
+        else
+          Constraint = "i";
+      }
+
       bool isOutput = (i == 1) && Desc.mayStore();
       SMLoc Start = SMLoc::getFromPointer(SymName.data());
       if (isOutput) {
         ++InputIdx;
         OutputDecls.push_back(OpDecl);
         OutputDeclsAddressOf.push_back(Operand.needAddressOf());
-        OutputConstraints.push_back(("=" + Operand.getConstraint()).str());
+        OutputConstraints.push_back(("=" + Constraint).str());
         AsmStrRewrites.emplace_back(AOK_Output, Start, SymName.size());
       } else {
         InputDecls.push_back(OpDecl);
         InputDeclsAddressOf.push_back(Operand.needAddressOf());
-        InputConstraints.push_back(Operand.getConstraint().str());
-        AsmStrRewrites.emplace_back(AOK_Input, Start, SymName.size());
+        InputConstraints.push_back(Constraint.str());
+        if (Desc.OpInfo[i - 1].isBranchTarget())
+          AsmStrRewrites.emplace_back(AOK_CallInput, Start, SymName.size());
+        else
+          AsmStrRewrites.emplace_back(AOK_Input, Start, SymName.size());
       }
     }
 
@@ -5895,7 +5895,11 @@ bool AsmParser::parseMSInlineAsm(
   const char *AsmStart = ASMString.begin();
   const char *AsmEnd = ASMString.end();
   array_pod_sort(AsmStrRewrites.begin(), AsmStrRewrites.end(), rewritesSort);
-  for (const AsmRewrite &AR : AsmStrRewrites) {
+  for (auto it = AsmStrRewrites.begin(); it != AsmStrRewrites.end(); ++it) {
+    const AsmRewrite &AR = *it;
+    // Check if this has already been covered by another rewrite...
+    if (AR.Done)
+      continue;
     AsmRewriteKind Kind = AR.Kind;
 
     const char *Loc = AR.Loc.getPointer();
@@ -5926,9 +5930,32 @@ bool AsmParser::parseMSInlineAsm(
         OS << (AR.IntelExp.hasBaseReg() ? " + " : "")
            << AR.IntelExp.IndexReg;
       if (AR.IntelExp.Scale > 1)
-          OS << " * $$" << AR.IntelExp.Scale;
-      if (AR.IntelExp.Imm || !AR.IntelExp.hasRegs())
-        OS << (AR.IntelExp.hasRegs() ? " + $$" : "$$") << AR.IntelExp.Imm;
+        OS << " * $$" << AR.IntelExp.Scale;
+      if (AR.IntelExp.hasOffset()) {
+        if (AR.IntelExp.hasRegs())
+          OS << " + ";
+        // Fuse this rewrite with a rewrite of the offset name, if present.
+        StringRef OffsetName = AR.IntelExp.OffsetName;
+        SMLoc OffsetLoc = SMLoc::getFromPointer(AR.IntelExp.OffsetName.data());
+        size_t OffsetLen = OffsetName.size();
+        auto rewrite_it = std::find_if(
+            it, AsmStrRewrites.end(), [&](const AsmRewrite &FusingAR) {
+              return FusingAR.Loc == OffsetLoc && FusingAR.Len == OffsetLen &&
+                     (FusingAR.Kind == AOK_Input ||
+                      FusingAR.Kind == AOK_CallInput);
+            });
+        if (rewrite_it == AsmStrRewrites.end()) {
+          OS << "offset " << OffsetName;
+        } else if (rewrite_it->Kind == AOK_CallInput) {
+          OS << "${" << InputIdx++ << ":P}";
+          rewrite_it->Done = true;
+        } else {
+          OS << '$' << InputIdx++;
+          rewrite_it->Done = true;
+        }
+      }
+      if (AR.IntelExp.Imm || AR.IntelExp.emitImm())
+        OS << (AR.IntelExp.emitImm() ? "$$" : " + $$") << AR.IntelExp.Imm;
       if (AR.IntelExp.NeedBracs)
         OS << "]";
       break;
@@ -5938,6 +5965,9 @@ bool AsmParser::parseMSInlineAsm(
     case AOK_Input:
       OS << '$' << InputIdx++;
       break;
+    case AOK_CallInput:
+      OS << "${" << InputIdx++ << ":P}";
+      break;
     case AOK_Output:
       OS << '$' << OutputIdx++;
       break;
diff --git a/llvm/lib/MC/MCParser/COFFAsmParser.cpp b/llvm/lib/MC/MCParser/COFFAsmParser.cpp
index 06f8310ae0615..51bb1fe92b73d 100644
--- a/llvm/lib/MC/MCParser/COFFAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/COFFAsmParser.cpp
@@ -144,7 +144,7 @@ public:
   COFFAsmParser() = default;
 };
 
-} // end annonomous namespace.
+} // end anonymous namespace.
 
 static SectionKind computeSectionKind(unsigned Flags) {
   if (Flags & COFF::IMAGE_SCN_MEM_EXECUTE)
diff --git a/llvm/lib/MC/MCSection.cpp b/llvm/lib/MC/MCSection.cpp
index 2c892ab816081..074534bd73dbd 100644
--- a/llvm/lib/MC/MCSection.cpp
+++ b/llvm/lib/MC/MCSection.cpp
@@ -22,8 +22,7 @@ using namespace llvm;
 
 MCSection::MCSection(SectionVariant V, SectionKind K, MCSymbol *Begin)
     : Begin(Begin), BundleGroupBeforeFirstInst(false), HasInstructions(false),
-      HasData(false), IsRegistered(false), DummyFragment(this), Variant(V),
-      Kind(K) {}
+      IsRegistered(false), DummyFragment(this), Variant(V), Kind(K) {}
 
 MCSymbol *MCSection::getEndSymbol(MCContext &Ctx) {
   if (!End)
@@ -86,6 +85,41 @@ MCSection::getSubsectionInsertionPoint(unsigned Subsection) {
   return IP;
 }
 
+void MCSection::addPendingLabel(MCSymbol* label, unsigned Subsection) {
+  PendingLabels.push_back(PendingLabel(label, Subsection));
+}
+
+void MCSection::flushPendingLabels(MCFragment *F, uint64_t FOffset,
+				   unsigned Subsection) {
+  if (PendingLabels.empty())
+    return;
+
+  // Set the fragment and fragment offset for all pending symbols in the
+  // specified Subsection, and remove those symbols from the pending list.
+  for (auto It = PendingLabels.begin(); It != PendingLabels.end(); ++It) {
+    PendingLabel& Label = *It;
+    if (Label.Subsection == Subsection) {
+      Label.Sym->setFragment(F);
+      Label.Sym->setOffset(FOffset);
+      PendingLabels.erase(It--);
+    }
+  }
+}
+
+void MCSection::flushPendingLabels() {
+  // Make sure all remaining pending labels point to data fragments, by
+  // creating new empty data fragments for each Subsection with labels pending.
+  while (!PendingLabels.empty()) {
+    PendingLabel& Label = PendingLabels[0];
+    iterator CurInsertionPoint =
+      this->getSubsectionInsertionPoint(Label.Subsection);
+    MCFragment *F = new MCDataFragment();
+    getFragmentList().insert(CurInsertionPoint, F);
+    F->setParent(this);
+    flushPendingLabels(F, 0, Label.Subsection);
+  }
+}
+
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MCSection::dump() const {
   raw_ostream &OS = errs();
diff --git a/llvm/lib/MC/MCSectionXCOFF.cpp b/llvm/lib/MC/MCSectionXCOFF.cpp
index d52959f15f928..8377e295532ae 100644
--- a/llvm/lib/MC/MCSectionXCOFF.cpp
+++ b/llvm/lib/MC/MCSectionXCOFF.cpp
@@ -15,18 +15,6 @@ using namespace llvm;
 
 MCSectionXCOFF::~MCSectionXCOFF() = default;
 
-static StringRef getMappingClassString(XCOFF::StorageMappingClass SMC) {
-  switch (SMC) {
-  case XCOFF::XMC_DS:
-    return "DS";
-  case XCOFF::XMC_RW:
-    return "RW";
-  case XCOFF::XMC_PR:
-    return "PR";
-  default:
-    report_fatal_error("Unhandled storage-mapping class.");
-  }
-}
 
 void MCSectionXCOFF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
                                           raw_ostream &OS,
@@ -35,9 +23,14 @@ void MCSectionXCOFF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
     if (getMappingClass() != XCOFF::XMC_PR)
       report_fatal_error("Unhandled storage-mapping class for .text csect");
 
-    OS << "\t.csect " << getSectionName() << "["
-       << getMappingClassString(getMappingClass())
-       << "]" << '\n';
+    OS << "\t.csect " << QualName->getName() << '\n';
+    return;
+  }
+
+  if (getKind().isReadOnly()) {
+    if (getMappingClass() != XCOFF::XMC_RO)
+      report_fatal_error("Unhandled storage-mapping class for .rodata csect.");
+    OS << "\t.csect " << QualName->getName() << '\n';
     return;
   }
 
@@ -45,8 +38,9 @@ void MCSectionXCOFF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
     switch (getMappingClass()) {
     case XCOFF::XMC_RW:
     case XCOFF::XMC_DS:
-      OS << "\t.csect " << getSectionName() << "["
-         << getMappingClassString(getMappingClass()) << "]" << '\n';
+      OS << "\t.csect " << QualName->getName() << '\n';
+      break;
+    case XCOFF::XMC_TC:
       break;
     case XCOFF::XMC_TC0:
       OS << "\t.toc\n";
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index b8278cb110799..0ab8835367798 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -977,9 +977,10 @@ void MCStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
 }
 
 void MCTargetStreamer::prettyPrintAsm(MCInstPrinter &InstPrinter,
-                                      raw_ostream &OS, const MCInst &Inst,
-                                      const MCSubtargetInfo &STI) {
-  InstPrinter.printInst(&Inst, OS, "", STI);
+                                      uint64_t Address, const MCInst &Inst,
+                                      const MCSubtargetInfo &STI,
+                                      raw_ostream &OS) {
+  InstPrinter.printInst(&Inst, Address, "", STI, OS);
 }
 
 void MCStreamer::visitUsedSymbol(const MCSymbol &Sym) {
@@ -1063,7 +1064,8 @@ void MCStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
 void MCStreamer::EmitCOFFSymbolType(int Type) {
   llvm_unreachable("this directive only supported on COFF targets");
 }
-void MCStreamer::EmitXCOFFLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
+void MCStreamer::EmitXCOFFLocalCommonSymbol(MCSymbol *LabelSym, uint64_t Size,
+                                            MCSymbol *CsectSym,
                                             unsigned ByteAlign) {
   llvm_unreachable("this directive only supported on XCOFF targets");
 }
diff --git a/llvm/lib/MC/MCSymbolELF.cpp b/llvm/lib/MC/MCSymbolELF.cpp
index a07c56c64f841..1830b87fd8567 100644
--- a/llvm/lib/MC/MCSymbolELF.cpp
+++ b/llvm/lib/MC/MCSymbolELF.cpp
@@ -40,8 +40,6 @@ 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:
@@ -93,8 +91,6 @@ 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/llvm/lib/MC/MCTargetOptions.cpp b/llvm/lib/MC/MCTargetOptions.cpp
index 96bb094134fe8..5848e3ecadbe1 100644
--- a/llvm/lib/MC/MCTargetOptions.cpp
+++ b/llvm/lib/MC/MCTargetOptions.cpp
@@ -15,8 +15,8 @@ MCTargetOptions::MCTargetOptions()
     : 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) {}
+      ShowMCEncoding(false), ShowMCInst(false), AsmVerbose(false),
+      PreserveAsmComments(true) {}
 
 StringRef MCTargetOptions::getABIName() const {
   return ABIName;
diff --git a/llvm/lib/MC/MCValue.cpp b/llvm/lib/MC/MCValue.cpp
index 81da47b2eced2..b6bcec9b2ca07 100644
--- a/llvm/lib/MC/MCValue.cpp
+++ b/llvm/lib/MC/MCValue.cpp
@@ -54,8 +54,5 @@ MCSymbolRefExpr::VariantKind MCValue::getAccessVariant() const {
   if (!A)
     return MCSymbolRefExpr::VK_None;
 
-  MCSymbolRefExpr::VariantKind Kind = A->getKind();
-  if (Kind == MCSymbolRefExpr::VK_WEAKREF)
-    return MCSymbolRefExpr::VK_None;
-  return Kind;
+  return A->getKind();
 }
diff --git a/llvm/lib/MC/MCXCOFFStreamer.cpp b/llvm/lib/MC/MCXCOFFStreamer.cpp
index 50937d6adc0c8..6efa167ced42a 100644
--- a/llvm/lib/MC/MCXCOFFStreamer.cpp
+++ b/llvm/lib/MC/MCXCOFFStreamer.cpp
@@ -50,12 +50,6 @@ void MCXCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                       XCOFF::C_HIDEXT);
   Symbol->setCommon(Size, ByteAlignment);
 
-  // Need to add this symbol to the current Fragment which will belong to the
-  // containing CSECT.
-  auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
-  assert(F && "Expected a valid section with a fragment set.");
-  Symbol->setFragment(F);
-
   // Emit the alignment and storage for the variable to the section.
   EmitValueToAlignment(ByteAlignment);
   EmitZeros(Size);
@@ -94,8 +88,9 @@ MCStreamer *llvm::createXCOFFStreamer(MCContext &Context,
   return S;
 }
 
-void MCXCOFFStreamer::EmitXCOFFLocalCommonSymbol(MCSymbol *Symbol,
+void MCXCOFFStreamer::EmitXCOFFLocalCommonSymbol(MCSymbol *LabelSym,
                                                  uint64_t Size,
+                                                 MCSymbol *CsectSym,
                                                  unsigned ByteAlignment) {
-  EmitCommonSymbol(Symbol, Size, ByteAlignment);
+  EmitCommonSymbol(CsectSym, Size, ByteAlignment);
 }
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index c1ff3cc2480cd..321f93d76092b 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -1324,6 +1324,14 @@ uint64_t WasmObjectWriter::writeObject(MCAssembler &Asm,
           Comdats[C->getName()].emplace_back(
               WasmComdatEntry{wasm::WASM_COMDAT_FUNCTION, Index});
         }
+
+        if (WS.hasExportName()) {
+          wasm::WasmExport Export;
+          Export.Name = WS.getExportName();
+          Export.Kind = wasm::WASM_EXTERNAL_FUNCTION;
+          Export.Index = Index;
+          Exports.push_back(Export);
+        }
       } else {
         // An import; the index was assigned above.
         Index = WasmIndices.find(&WS)->second;
@@ -1452,8 +1460,10 @@ uint64_t WasmObjectWriter::writeObject(MCAssembler &Asm,
         Flags |= wasm::WASM_SYMBOL_EXPORTED;
       }
     }
-    if (WS.getName() != WS.getImportName())
+    if (WS.hasImportName())
       Flags |= wasm::WASM_SYMBOL_EXPLICIT_NAME;
+    if (WS.hasExportName())
+      Flags |= wasm::WASM_SYMBOL_EXPORTED;
 
     wasm::WasmSymbolInfo Info;
     Info.Name = WS.getName();
diff --git a/llvm/lib/MC/XCOFFObjectWriter.cpp b/llvm/lib/MC/XCOFFObjectWriter.cpp
index 353c21068735b..e584c6222a5a2 100644
--- a/llvm/lib/MC/XCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/XCOFFObjectWriter.cpp
@@ -44,6 +44,7 @@ using namespace llvm;
 namespace {
 
 constexpr unsigned DefaultSectionAlign = 4;
+constexpr int16_t MaxSectionIndex = INT16_MAX;
 
 // Packs the csect's alignment and type into a byte.
 uint8_t getEncodedType(const MCSectionXCOFF *);
@@ -73,6 +74,14 @@ struct ControlSection {
       : MCCsect(MCSec), SymbolTableIndex(-1), Address(-1), Size(0) {}
 };
 
+// Type to be used for a container representing a set of csects with
+// (approximately) the same storage mapping class. For example all the csects
+// with a storage mapping class of `xmc_pr` will get placed into the same
+// container.
+using CsectGroup = std::deque<ControlSection>;
+
+using CsectGroups = std::deque<CsectGroup *>;
+
 // Represents the data related to a section excluding the csects that make up
 // the raw data of the section. The csects are stored separately as not all
 // sections contain csects, and some sections contain csects which are better
@@ -94,49 +103,70 @@ struct Section {
   // Virtual sections do not need storage allocated in the object file.
   const bool IsVirtual;
 
+  // XCOFF has special section numbers for symbols:
+  // -2 Specifies N_DEBUG, a special symbolic debugging symbol.
+  // -1 Specifies N_ABS, an absolute symbol. The symbol has a value but is not
+  // relocatable.
+  //  0 Specifies N_UNDEF, an undefined external symbol.
+  // Therefore, we choose -3 (N_DEBUG - 1) to represent a section index that
+  // hasn't been initialized.
+  static constexpr int16_t UninitializedIndex =
+      XCOFF::ReservedSectionNum::N_DEBUG - 1;
+
+  CsectGroups Groups;
+
   void reset() {
     Address = 0;
     Size = 0;
     FileOffsetToData = 0;
     FileOffsetToRelocations = 0;
     RelocationCount = 0;
-    Index = -1;
+    Index = UninitializedIndex;
+    // Clear any csects we have stored.
+    for (auto *Group : Groups)
+      Group->clear();
   }
 
-  Section(const char *N, XCOFF::SectionTypeFlags Flags, bool IsVirtual)
+  Section(const char *N, XCOFF::SectionTypeFlags Flags, bool IsVirtual,
+          CsectGroups Groups)
       : Address(0), Size(0), FileOffsetToData(0), FileOffsetToRelocations(0),
-        RelocationCount(0), Flags(Flags), Index(-1), IsVirtual(IsVirtual) {
+        RelocationCount(0), Flags(Flags), Index(UninitializedIndex),
+        IsVirtual(IsVirtual), Groups(Groups) {
     strncpy(Name, N, XCOFF::NameSize);
   }
 };
 
 class XCOFFObjectWriter : public MCObjectWriter {
-  // Type to be used for a container representing a set of csects with
-  // (approximately) the same storage mapping class. For example all the csects
-  // with a storage mapping class of `xmc_pr` will get placed into the same
-  // container.
-  using CsectGroup = std::deque<ControlSection>;
+
+  uint32_t SymbolTableEntryCount = 0;
+  uint32_t SymbolTableOffset = 0;
+  uint16_t SectionCount = 0;
 
   support::endian::Writer W;
   std::unique_ptr<MCXCOFFObjectTargetWriter> TargetObjectWriter;
   StringTableBuilder Strings;
 
-  // The non-empty sections, in the order they will appear in the section header
-  // table.
-  std::vector<Section *> Sections;
-
-  // The Predefined sections.
-  Section Text;
-  Section BSS;
-
   // CsectGroups. These store the csects which make up different parts of
   // the sections. Should have one for each set of csects that get mapped into
   // the same section and get handled in a 'similar' way.
+  CsectGroup UndefinedCsects;
   CsectGroup ProgramCodeCsects;
+  CsectGroup ReadOnlyCsects;
+  CsectGroup DataCsects;
+  CsectGroup FuncDSCsects;
+  CsectGroup TOCCsects;
   CsectGroup BSSCsects;
 
-  uint32_t SymbolTableEntryCount = 0;
-  uint32_t SymbolTableOffset = 0;
+  // The Predefined sections.
+  Section Text;
+  Section Data;
+  Section BSS;
+
+  // All the XCOFF sections, in the order they will appear in the section header
+  // table.
+  std::array<Section *const, 3> Sections{{&Text, &Data, &BSS}};
+
+  CsectGroup &getCsectGroup(const MCSectionXCOFF *MCSec);
 
   virtual void reset() override;
 
@@ -190,27 +220,72 @@ XCOFFObjectWriter::XCOFFObjectWriter(
     std::unique_ptr<MCXCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS)
     : W(OS, support::big), TargetObjectWriter(std::move(MOTW)),
       Strings(StringTableBuilder::XCOFF),
-      Text(".text", XCOFF::STYP_TEXT, /* IsVirtual */ false),
-      BSS(".bss", XCOFF::STYP_BSS, /* IsVirtual */ true) {}
+      Text(".text", XCOFF::STYP_TEXT, /* IsVirtual */ false,
+           CsectGroups{&ProgramCodeCsects, &ReadOnlyCsects}),
+      Data(".data", XCOFF::STYP_DATA, /* IsVirtual */ false,
+           CsectGroups{&DataCsects, &FuncDSCsects, &TOCCsects}),
+      BSS(".bss", XCOFF::STYP_BSS, /* IsVirtual */ true,
+          CsectGroups{&BSSCsects}) {}
 
 void XCOFFObjectWriter::reset() {
+  UndefinedCsects.clear();
+
   // Reset any sections we have written to, and empty the section header table.
   for (auto *Sec : Sections)
     Sec->reset();
-  Sections.clear();
-
-  // Clear any csects we have stored.
-  ProgramCodeCsects.clear();
-  BSSCsects.clear();
 
   // Reset the symbol table and string table.
   SymbolTableEntryCount = 0;
   SymbolTableOffset = 0;
+  SectionCount = 0;
   Strings.clear();
 
   MCObjectWriter::reset();
 }
 
+CsectGroup &XCOFFObjectWriter::getCsectGroup(const MCSectionXCOFF *MCSec) {
+  switch (MCSec->getMappingClass()) {
+  case XCOFF::XMC_PR:
+    assert(XCOFF::XTY_SD == MCSec->getCSectType() &&
+           "Only an initialized csect can contain program code.");
+    return ProgramCodeCsects;
+  case XCOFF::XMC_RO:
+    assert(XCOFF::XTY_SD == MCSec->getCSectType() &&
+           "Only an initialized csect can contain read only data.");
+    return ReadOnlyCsects;
+  case XCOFF::XMC_RW:
+    if (XCOFF::XTY_CM == MCSec->getCSectType())
+      return BSSCsects;
+
+    if (XCOFF::XTY_SD == MCSec->getCSectType())
+      return DataCsects;
+
+    report_fatal_error("Unhandled mapping of read-write csect to section.");
+  case XCOFF::XMC_DS:
+    return FuncDSCsects;
+  case XCOFF::XMC_BS:
+    assert(XCOFF::XTY_CM == MCSec->getCSectType() &&
+           "Mapping invalid csect. CSECT with bss storage class must be "
+           "common type.");
+    return BSSCsects;
+  case XCOFF::XMC_TC0:
+    assert(XCOFF::XTY_SD == MCSec->getCSectType() &&
+           "Only an initialized csect can contain TOC-base.");
+    assert(TOCCsects.empty() &&
+           "We should have only one TOC-base, and it should be the first csect "
+           "in this CsectGroup.");
+    return TOCCsects;
+  case XCOFF::XMC_TC:
+    assert(XCOFF::XTY_SD == MCSec->getCSectType() &&
+           "Only an initialized csect can contain TC entry.");
+    assert(!TOCCsects.empty() &&
+           "We should at least have a TOC-base in this CsectGroup.");
+    return TOCCsects;
+  default:
+    report_fatal_error("Unhandled mapping of csect to section.");
+  }
+}
+
 void XCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
                                                  const MCAsmLayout &Layout) {
   if (TargetObjectWriter->is64Bit())
@@ -225,49 +300,38 @@ void XCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
     const auto *MCSec = cast<const MCSectionXCOFF>(&S);
     assert(WrapperMap.find(MCSec) == WrapperMap.end() &&
            "Cannot add a csect twice.");
+    assert(XCOFF::XTY_ER != MCSec->getCSectType() &&
+           "An undefined csect should not get registered.");
 
     // If the name does not fit in the storage provided in the symbol table
     // entry, add it to the string table.
     if (nameShouldBeInStringTable(MCSec->getSectionName()))
       Strings.add(MCSec->getSectionName());
 
-    switch (MCSec->getMappingClass()) {
-    case XCOFF::XMC_PR:
-      assert(XCOFF::XTY_SD == MCSec->getCSectType() &&
-             "Only an initialized csect can contain program code.");
-      ProgramCodeCsects.emplace_back(MCSec);
-      WrapperMap[MCSec] = &ProgramCodeCsects.back();
-      break;
-    case XCOFF::XMC_RW:
-      if (XCOFF::XTY_CM == MCSec->getCSectType()) {
-        BSSCsects.emplace_back(MCSec);
-        WrapperMap[MCSec] = &BSSCsects.back();
-        break;
-      }
-      report_fatal_error("Unhandled mapping of read-write csect to section.");
-    case XCOFF::XMC_TC0:
-      // TODO FIXME Handle emiting the TOC base.
-      break;
-    case XCOFF::XMC_BS:
-      assert(XCOFF::XTY_CM == MCSec->getCSectType() &&
-             "Mapping invalid csect. CSECT with bss storage class must be "
-             "common type.");
-      BSSCsects.emplace_back(MCSec);
-      WrapperMap[MCSec] = &BSSCsects.back();
-      break;
-    default:
-      report_fatal_error("Unhandled mapping of csect to section.");
-    }
+    CsectGroup &Group = getCsectGroup(MCSec);
+    Group.emplace_back(MCSec);
+    WrapperMap[MCSec] = &Group.back();
   }
 
   for (const MCSymbol &S : Asm.symbols()) {
     // Nothing to do for temporary symbols.
     if (S.isTemporary())
       continue;
-    const MCSymbolXCOFF *XSym = cast<MCSymbolXCOFF>(&S);
 
-    // Map the symbol into its containing csect.
+    const MCSymbolXCOFF *XSym = cast<MCSymbolXCOFF>(&S);
     const MCSectionXCOFF *ContainingCsect = XSym->getContainingCsect();
+
+    // Handle undefined symbol.
+    if (ContainingCsect->getCSectType() == XCOFF::XTY_ER) {
+      UndefinedCsects.emplace_back(ContainingCsect);
+      continue;
+    }
+
+    // If the symbol is the csect itself, we don't need to put the symbol
+    // into csect's Syms.
+    if (XSym == ContainingCsect->getQualNameSymbol())
+      continue;
+
     assert(WrapperMap.find(ContainingCsect) != WrapperMap.end() &&
            "Expected containing csect to exist in map");
 
@@ -287,27 +351,37 @@ void XCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
 void XCOFFObjectWriter::recordRelocation(MCAssembler &, const MCAsmLayout &,
                                          const MCFragment *, const MCFixup &,
                                          MCValue, uint64_t &) {
-  report_fatal_error("XCOFF relocations not supported.");
+  // TODO: recordRelocation is not yet implemented.
 }
 
 void XCOFFObjectWriter::writeSections(const MCAssembler &Asm,
                                       const MCAsmLayout &Layout) {
-  // Write the program code control sections one at a time.
-  uint32_t CurrentAddressLocation = Text.Address;
-  for (const auto &Csect : ProgramCodeCsects) {
-    if (uint32_t PaddingSize = Csect.Address - CurrentAddressLocation)
-      W.OS.write_zeros(PaddingSize);
-    Asm.writeSectionData(W.OS, Csect.MCCsect, Layout);
-    CurrentAddressLocation = Csect.Address + Csect.Size;
-  }
+  uint32_t CurrentAddressLocation = 0;
+  for (const auto *Section : Sections) {
+    // Nothing to write for this Section.
+    if (Section->Index == Section::UninitializedIndex || Section->IsVirtual)
+      continue;
+
+    assert(CurrentAddressLocation == Section->Address &&
+           "Sections should be written consecutively.");
+    for (const auto *Group : Section->Groups) {
+      for (const auto &Csect : *Group) {
+        if (uint32_t PaddingSize = Csect.Address - CurrentAddressLocation)
+          W.OS.write_zeros(PaddingSize);
+        if (Csect.Size)
+          Asm.writeSectionData(W.OS, Csect.MCCsect, Layout);
+        CurrentAddressLocation = Csect.Address + Csect.Size;
+      }
+    }
 
-  if (Text.Index != -1) {
     // The size of the tail padding in a section is the end virtual address of
     // the current section minus the the end virtual address of the last csect
     // in that section.
     if (uint32_t PaddingSize =
-            Text.Address + Text.Size - CurrentAddressLocation)
+            Section->Address + Section->Size - CurrentAddressLocation) {
       W.OS.write_zeros(PaddingSize);
+      CurrentAddressLocation += PaddingSize;
+    }
   }
 }
 
@@ -345,7 +419,7 @@ void XCOFFObjectWriter::writeSymbolName(const StringRef &SymbolName) {
     W.write<int32_t>(0);
     W.write<uint32_t>(Strings.getOffset(SymbolName));
   } else {
-    char Name[XCOFF::NameSize];
+    char Name[XCOFF::NameSize+1];
     std::strncpy(Name, SymbolName.data(), XCOFF::NameSize);
     ArrayRef<char> NameRef(Name, XCOFF::NameSize);
     W.write(NameRef);
@@ -431,7 +505,7 @@ void XCOFFObjectWriter::writeFileHeader() {
   // Magic.
   W.write<uint16_t>(0x01df);
   // Number of sections.
-  W.write<uint16_t>(Sections.size());
+  W.write<uint16_t>(SectionCount);
   // Timestamp field. For reproducible output we write a 0, which represents no
   // timestamp.
   W.write<int32_t>(0);
@@ -447,6 +521,10 @@ void XCOFFObjectWriter::writeFileHeader() {
 
 void XCOFFObjectWriter::writeSectionHeaderTable() {
   for (const auto *Sec : Sections) {
+    // Nothing to write for this Section.
+    if (Sec->Index == Section::UninitializedIndex)
+      continue;
+
     // Write Name.
     ArrayRef<char> NameRef(Sec->Name, XCOFF::NameSize);
     W.write(NameRef);
@@ -472,104 +550,112 @@ void XCOFFObjectWriter::writeSectionHeaderTable() {
 }
 
 void XCOFFObjectWriter::writeSymbolTable(const MCAsmLayout &Layout) {
-  // Print out symbol table for the program code.
-  for (const auto &Csect : ProgramCodeCsects) {
-    // Write out the control section first and then each symbol in it.
-    writeSymbolTableEntryForControlSection(Csect, Text.Index,
-                                           Csect.MCCsect->getStorageClass());
-    for (const auto &Sym : Csect.Syms)
-      writeSymbolTableEntryForCsectMemberLabel(
-          Sym, Csect, Text.Index, Layout.getSymbolOffset(*Sym.MCSym));
+  for (const auto &Csect : UndefinedCsects) {
+    writeSymbolTableEntryForControlSection(
+        Csect, XCOFF::ReservedSectionNum::N_UNDEF, Csect.MCCsect->getStorageClass());
   }
 
-  // The BSS Section is special in that the csects must contain a single symbol,
-  // and the contained symbol cannot be represented in the symbol table as a
-  // label definition.
-  for (auto &Csect : BSSCsects) {
-    assert(Csect.Syms.size() == 1 &&
-           "Uninitialized csect cannot contain more then 1 symbol.");
-    Symbol &Sym = Csect.Syms.back();
-    writeSymbolTableEntryForControlSection(Csect, BSS.Index,
-                                           Sym.getStorageClass());
+  for (const auto *Section : Sections) {
+    // Nothing to write for this Section.
+    if (Section->Index == Section::UninitializedIndex)
+      continue;
+
+    for (const auto *Group : Section->Groups) {
+      if (Group->empty())
+        continue;
+
+      const int16_t SectionIndex = Section->Index;
+      for (const auto &Csect : *Group) {
+        // Write out the control section first and then each symbol in it.
+        writeSymbolTableEntryForControlSection(
+            Csect, SectionIndex, Csect.MCCsect->getStorageClass());
+
+        for (const auto &Sym : Csect.Syms)
+          writeSymbolTableEntryForCsectMemberLabel(
+              Sym, Csect, SectionIndex, Layout.getSymbolOffset(*(Sym.MCSym)));
+      }
+    }
   }
 }
 
 void XCOFFObjectWriter::assignAddressesAndIndices(const MCAsmLayout &Layout) {
+  // The first symbol table entry is for the file name. We are not emitting it
+  // yet, so start at index 0.
+  uint32_t SymbolTableIndex = 0;
+
+  // Calculate indices for undefined symbols.
+  for (auto &Csect : UndefinedCsects) {
+    Csect.Size = 0;
+    Csect.Address = 0;
+    Csect.SymbolTableIndex = SymbolTableIndex;
+    // 1 main and 1 auxiliary symbol table entry for each contained symbol.
+    SymbolTableIndex += 2;
+  }
+
   // The address corrresponds to the address of sections and symbols in the
   // object file. We place the shared address 0 immediately after the
   // section header table.
   uint32_t Address = 0;
   // Section indices are 1-based in XCOFF.
-  int16_t SectionIndex = 1;
-  // The first symbol table entry is for the file name. We are not emitting it
-  // yet, so start at index 0.
-  uint32_t SymbolTableIndex = 0;
+  int32_t SectionIndex = 1;
 
-  // Text section comes first.
-  if (!ProgramCodeCsects.empty()) {
-    Sections.push_back(&Text);
-    Text.Index = SectionIndex++;
-    for (auto &Csect : ProgramCodeCsects) {
-      const MCSectionXCOFF *MCSec = Csect.MCCsect;
-      Csect.Address = alignTo(Address, MCSec->getAlignment());
-      Csect.Size = Layout.getSectionAddressSize(MCSec);
-      Address = Csect.Address + Csect.Size;
-      Csect.SymbolTableIndex = SymbolTableIndex;
-      // 1 main and 1 auxiliary symbol table entry for the csect.
-      SymbolTableIndex += 2;
-      for (auto &Sym : Csect.Syms) {
-        Sym.SymbolTableIndex = SymbolTableIndex;
-        // 1 main and 1 auxiliary symbol table entry for each contained symbol
+  for (auto *Section : Sections) {
+    const bool IsEmpty =
+        llvm::all_of(Section->Groups,
+                     [](const CsectGroup *Group) { return Group->empty(); });
+    if (IsEmpty)
+      continue;
+
+    if (SectionIndex > MaxSectionIndex)
+      report_fatal_error("Section index overflow!");
+    Section->Index = SectionIndex++;
+    SectionCount++;
+
+    bool SectionAddressSet = false;
+    for (auto *Group : Section->Groups) {
+      if (Group->empty())
+        continue;
+
+      for (auto &Csect : *Group) {
+        const MCSectionXCOFF *MCSec = Csect.MCCsect;
+        Csect.Address = alignTo(Address, MCSec->getAlignment());
+        Csect.Size = Layout.getSectionAddressSize(MCSec);
+        Address = Csect.Address + Csect.Size;
+        Csect.SymbolTableIndex = SymbolTableIndex;
+        // 1 main and 1 auxiliary symbol table entry for the csect.
         SymbolTableIndex += 2;
+        
+        for (auto &Sym : Csect.Syms) {
+          Sym.SymbolTableIndex = SymbolTableIndex;
+          // 1 main and 1 auxiliary symbol table entry for each contained
+          // symbol.
+          SymbolTableIndex += 2;
+        }
       }
-    }
-    Address = alignTo(Address, DefaultSectionAlign);
 
-    // The first csect of a section can be aligned by adjusting the virtual
-    // address of its containing section instead of writing zeroes into the
-    // object file.
-    Text.Address = ProgramCodeCsects.front().Address;
-
-    Text.Size = Address - Text.Address;
-  }
-
-  // Data section Second. TODO
-
-  // BSS Section third.
-  if (!BSSCsects.empty()) {
-    Sections.push_back(&BSS);
-    BSS.Index = SectionIndex++;
-    for (auto &Csect : BSSCsects) {
-      const MCSectionXCOFF *MCSec = Csect.MCCsect;
-      Csect.Address = alignTo(Address, MCSec->getAlignment());
-      Csect.Size = Layout.getSectionAddressSize(MCSec);
-      Address = Csect.Address + Csect.Size;
-      Csect.SymbolTableIndex = SymbolTableIndex;
-      // 1 main and 1 auxiliary symbol table entry for the csect.
-      SymbolTableIndex += 2;
-
-      assert(Csect.Syms.size() == 1 &&
-             "csect in the BSS can only contain a single symbol.");
-      Csect.Syms[0].SymbolTableIndex = Csect.SymbolTableIndex;
+      if (!SectionAddressSet) {
+        Section->Address = Group->front().Address;
+        SectionAddressSet = true;
+      }
     }
-    // Pad out Address to the default alignment. This is to match how the system
-    // assembler handles the .bss section. Its size is always a multiple of 4.
-    Address = alignTo(Address, DefaultSectionAlign);
 
-    BSS.Address = BSSCsects.front().Address;
-    BSS.Size = Address - BSS.Address;
+    // Make sure the address of the next section aligned to
+    // DefaultSectionAlign.
+    Address = alignTo(Address, DefaultSectionAlign);
+    Section->Size = Address - Section->Address;
   }
 
   SymbolTableEntryCount = SymbolTableIndex;
 
   // Calculate the RawPointer value for each section.
   uint64_t RawPointer = sizeof(XCOFF::FileHeader32) + auxiliaryHeaderSize() +
-                        Sections.size() * sizeof(XCOFF::SectionHeader32);
+                        SectionCount * sizeof(XCOFF::SectionHeader32);
   for (auto *Sec : Sections) {
-    if (!Sec->IsVirtual) {
-      Sec->FileOffsetToData = RawPointer;
-      RawPointer += Sec->Size;
-    }
+    if (Sec->Index == Section::UninitializedIndex || Sec->IsVirtual)
+      continue;
+
+    Sec->FileOffsetToData = RawPointer;
+    RawPointer += Sec->Size;
   }
 
   // TODO Add in Relocation storage to the RawPointer Calculation.