vendor/llvm/llvm-trunk-r290819

1 files changed, 288 insertions, 173 deletions

diff --git a/lib/Bitcode/Writer/BitcodeWriter.cpp b/lib/Bitcode/Writer/BitcodeWriter.cpp
index dcb8b58cd7b3c..c10ba2399e717 100644
--- a/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -11,12 +11,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Bitcode/BitcodeWriter.h"
 #include "ValueEnumerator.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Bitcode/BitstreamWriter.h"
 #include "llvm/Bitcode/LLVMBitCodes.h"
-#include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DebugInfoMetadata.h"
@@ -38,6 +38,11 @@
 using namespace llvm;
 
 namespace {
+
+cl::opt<unsigned>
+    IndexThreshold("bitcode-mdindex-threshold", cl::Hidden, cl::init(25),
+                   cl::desc("Number of metadatas above which we emit an index "
+                            "to enable lazy-loading"));
 /// These are manifest constants used by the bitcode writer. They do not need to
 /// be kept in sync with the reader, but need to be consistent within this file.
 enum {
@@ -65,36 +70,20 @@ enum {
 };
 
 /// Abstract class to manage the bitcode writing, subclassed for each bitcode
-/// file type. Owns the BitstreamWriter, and includes the main entry point for
-/// writing.
-class BitcodeWriter {
+/// file type.
+class BitcodeWriterBase {
 protected:
-  /// Pointer to the buffer allocated by caller for bitcode writing.
-  const SmallVectorImpl<char> &Buffer;
-
-  /// The stream created and owned by the BitodeWriter.
-  BitstreamWriter Stream;
+  /// The stream created and owned by the client.
+  BitstreamWriter &Stream;
 
   /// Saves the offset of the VSTOffset record that must eventually be
   /// backpatched with the offset of the actual VST.
   uint64_t VSTOffsetPlaceholder = 0;
 
 public:
-  /// Constructs a BitcodeWriter object, and initializes a BitstreamRecord,
-  /// writing to the provided \p Buffer.
-  BitcodeWriter(SmallVectorImpl<char> &Buffer)
-      : Buffer(Buffer), Stream(Buffer) {}
-
-  virtual ~BitcodeWriter() = default;
-
-  /// Main entry point to write the bitcode file, which writes the bitcode
-  /// header and will then invoke the virtual writeBlocks() method.
-  void write();
-
-private:
-  /// Derived classes must implement this to write the corresponding blocks for
-  /// that bitcode file type.
-  virtual void writeBlocks() = 0;
+  /// Constructs a BitcodeWriterBase object that writes to the provided
+  /// \p Stream.
+  BitcodeWriterBase(BitstreamWriter &Stream) : Stream(Stream) {}
 
 protected:
   bool hasVSTOffsetPlaceholder() { return VSTOffsetPlaceholder != 0; }
@@ -103,7 +92,10 @@ protected:
 };
 
 /// Class to manage the bitcode writing for a module.
-class ModuleBitcodeWriter : public BitcodeWriter {
+class ModuleBitcodeWriter : public BitcodeWriterBase {
+  /// Pointer to the buffer allocated by caller for bitcode writing.
+  const SmallVectorImpl<char> &Buffer;
+
   /// The Module to write to bitcode.
   const Module &M;
 
@@ -116,8 +108,8 @@ class ModuleBitcodeWriter : public BitcodeWriter {
   /// True if a module hash record should be written.
   bool GenerateHash;
 
-  /// The start bit of the module block, for use in generating a module hash
-  uint64_t BitcodeStartBit = 0;
+  /// The start bit of the identification block.
+  uint64_t BitcodeStartBit;
 
   /// Map that holds the correspondence between GUIDs in the summary index,
   /// that came from indirect call profiles, and a value id generated by this
@@ -131,51 +123,38 @@ public:
   /// Constructs a ModuleBitcodeWriter object for the given Module,
   /// writing to the provided \p Buffer.
   ModuleBitcodeWriter(const Module *M, SmallVectorImpl<char> &Buffer,
-                      bool ShouldPreserveUseListOrder,
+                      BitstreamWriter &Stream, bool ShouldPreserveUseListOrder,
                       const ModuleSummaryIndex *Index, bool GenerateHash)
-      : BitcodeWriter(Buffer), M(*M), VE(*M, ShouldPreserveUseListOrder),
-        Index(Index), GenerateHash(GenerateHash) {
-    // Save the start bit of the actual bitcode, in case there is space
-    // saved at the start for the darwin header above. The reader stream
-    // will start at the bitcode, and we need the offset of the VST
-    // to line up.
-    BitcodeStartBit = Stream.GetCurrentBitNo();
-
+      : BitcodeWriterBase(Stream), Buffer(Buffer), M(*M),
+        VE(*M, ShouldPreserveUseListOrder), Index(Index),
+        GenerateHash(GenerateHash), BitcodeStartBit(Stream.GetCurrentBitNo()) {
     // Assign ValueIds to any callee values in the index that came from
     // indirect call profiles and were recorded as a GUID not a Value*
     // (which would have been assigned an ID by the ValueEnumerator).
     // The starting ValueId is just after the number of values in the
     // ValueEnumerator, so that they can be emitted in the VST.
     GlobalValueId = VE.getValues().size();
-    if (Index)
-      for (const auto &GUIDSummaryLists : *Index)
-        // Examine all summaries for this GUID.
-        for (auto &Summary : GUIDSummaryLists.second)
-          if (auto FS = dyn_cast<FunctionSummary>(Summary.get()))
-            // For each call in the function summary, see if the call
-            // is to a GUID (which means it is for an indirect call,
-            // otherwise we would have a Value for it). If so, synthesize
-            // a value id.
-            for (auto &CallEdge : FS->calls())
-              if (CallEdge.first.isGUID())
-                assignValueId(CallEdge.first.getGUID());
+    if (!Index)
+      return;
+    for (const auto &GUIDSummaryLists : *Index)
+      // Examine all summaries for this GUID.
+      for (auto &Summary : GUIDSummaryLists.second)
+        if (auto FS = dyn_cast<FunctionSummary>(Summary.get()))
+          // For each call in the function summary, see if the call
+          // is to a GUID (which means it is for an indirect call,
+          // otherwise we would have a Value for it). If so, synthesize
+          // a value id.
+          for (auto &CallEdge : FS->calls())
+            if (CallEdge.first.isGUID())
+              assignValueId(CallEdge.first.getGUID());
   }
 
-private:
-  /// Main entry point for writing a module to bitcode, invoked by
-  /// BitcodeWriter::write() after it writes the header.
-  void writeBlocks() override;
-
-  /// Create the "IDENTIFICATION_BLOCK_ID" containing a single string with the
-  /// current llvm version, and a record for the epoch number.
-  void writeIdentificationBlock();
-
   /// Emit the current module to the bitstream.
-  void writeModule();
+  void write();
 
+private:
   uint64_t bitcodeStartBit() { return BitcodeStartBit; }
 
-  void writeStringRecord(unsigned Code, StringRef Str, unsigned AbbrevToUse);
   void writeAttributeGroupTable();
   void writeAttributeTable();
   void writeTypeTable();
@@ -236,6 +215,9 @@ private:
                             SmallVectorImpl<uint64_t> &Record, unsigned Abbrev);
   void writeDIExpression(const DIExpression *N,
                          SmallVectorImpl<uint64_t> &Record, unsigned Abbrev);
+  void writeDIGlobalVariableExpression(const DIGlobalVariableExpression *N,
+                                       SmallVectorImpl<uint64_t> &Record,
+                                       unsigned Abbrev);
   void writeDIObjCProperty(const DIObjCProperty *N,
                            SmallVectorImpl<uint64_t> &Record, unsigned Abbrev);
   void writeDIImportedEntity(const DIImportedEntity *N,
@@ -247,7 +229,9 @@ private:
   void writeMetadataStrings(ArrayRef<const Metadata *> Strings,
                             SmallVectorImpl<uint64_t> &Record);
   void writeMetadataRecords(ArrayRef<const Metadata *> MDs,
-                            SmallVectorImpl<uint64_t> &Record);
+                            SmallVectorImpl<uint64_t> &Record,
+                            std::vector<unsigned> *MDAbbrevs = nullptr,
+                            std::vector<uint64_t> *IndexPos = nullptr);
   void writeModuleMetadata();
   void writeFunctionMetadata(const Function &F);
   void writeFunctionMetadataAttachment(const Function &F);
@@ -293,7 +277,10 @@ private:
   }
   unsigned getValueId(GlobalValue::GUID ValGUID) {
     const auto &VMI = GUIDToValueIdMap.find(ValGUID);
-    assert(VMI != GUIDToValueIdMap.end());
+    // Expect that any GUID value had a value Id assigned by an
+    // earlier call to assignValueId.
+    assert(VMI != GUIDToValueIdMap.end() &&
+           "GUID does not have assigned value Id");
     return VMI->second;
   }
   // Helper to get the valueId for the type of value recorded in VI.
@@ -306,13 +293,13 @@ private:
 };
 
 /// Class to manage the bitcode writing for a combined index.
-class IndexBitcodeWriter : public BitcodeWriter {
+class IndexBitcodeWriter : public BitcodeWriterBase {
   /// The combined index to write to bitcode.
   const ModuleSummaryIndex &Index;
 
   /// When writing a subset of the index for distributed backends, client
   /// provides a map of modules to the corresponding GUIDs/summaries to write.
-  std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex;
+  const std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex;
 
   /// Map that holds the correspondence between the GUID used in the combined
   /// index and a value id generated by this class to use in references.
@@ -325,11 +312,10 @@ public:
   /// Constructs a IndexBitcodeWriter object for the given combined index,
   /// writing to the provided \p Buffer. When writing a subset of the index
   /// for a distributed backend, provide a \p ModuleToSummariesForIndex map.
-  IndexBitcodeWriter(SmallVectorImpl<char> &Buffer,
-                     const ModuleSummaryIndex &Index,
-                     std::map<std::string, GVSummaryMapTy>
+  IndexBitcodeWriter(BitstreamWriter &Stream, const ModuleSummaryIndex &Index,
+                     const std::map<std::string, GVSummaryMapTy>
                          *ModuleToSummariesForIndex = nullptr)
-      : BitcodeWriter(Buffer), Index(Index),
+      : BitcodeWriterBase(Stream), Index(Index),
         ModuleToSummariesForIndex(ModuleToSummariesForIndex) {
     // Assign unique value ids to all summaries to be written, for use
     // in writing out the call graph edges. Save the mapping from GUID
@@ -355,11 +341,11 @@ public:
     // ModuleToSummariesForIndex map:
 
     /// Points to the last element in outer ModuleToSummariesForIndex map.
-    std::map<std::string, GVSummaryMapTy>::iterator ModuleSummariesBack;
+    std::map<std::string, GVSummaryMapTy>::const_iterator ModuleSummariesBack;
     /// Iterator on outer ModuleToSummariesForIndex map.
-    std::map<std::string, GVSummaryMapTy>::iterator ModuleSummariesIter;
+    std::map<std::string, GVSummaryMapTy>::const_iterator ModuleSummariesIter;
     /// Iterator on an inner global variable summary map.
-    GVSummaryMapTy::iterator ModuleGVSummariesIter;
+    GVSummaryMapTy::const_iterator ModuleGVSummariesIter;
 
     // Iterators used when writing all summaries in the index:
 
@@ -476,11 +462,10 @@ public:
   /// Obtain the end iterator over the summaries to be written.
   iterator end() { return iterator(*this, /*IsAtEnd=*/true); }
 
-private:
-  /// Main entry point for writing a combined index to bitcode, invoked by
-  /// BitcodeWriter::write() after it writes the header.
-  void writeBlocks() override;
+  /// Main entry point for writing a combined index to bitcode.
+  void write();
 
+private:
   void writeIndex();
   void writeModStrings();
   void writeCombinedValueSymbolTable();
@@ -593,8 +578,8 @@ static unsigned getEncodedSynchScope(SynchronizationScope SynchScope) {
   llvm_unreachable("Invalid synch scope");
 }
 
-void ModuleBitcodeWriter::writeStringRecord(unsigned Code, StringRef Str,
-                                            unsigned AbbrevToUse) {
+static void writeStringRecord(BitstreamWriter &Stream, unsigned Code,
+                              StringRef Str, unsigned AbbrevToUse) {
   SmallVector<unsigned, 64> Vals;
 
   // Code: [strchar x N]
@@ -918,7 +903,7 @@ void ModuleBitcodeWriter::writeTypeTable() {
 
         // Emit the name if it is present.
         if (!ST->getName().empty())
-          writeStringRecord(bitc::TYPE_CODE_STRUCT_NAME, ST->getName(),
+          writeStringRecord(Stream, bitc::TYPE_CODE_STRUCT_NAME, ST->getName(),
                             StructNameAbbrev);
       }
       break;
@@ -986,8 +971,9 @@ static unsigned getEncodedLinkage(const GlobalValue &GV) {
 static uint64_t getEncodedGVSummaryFlags(GlobalValueSummary::GVFlags Flags) {
   uint64_t RawFlags = 0;
 
-  RawFlags |= Flags.HasSection; // bool
-
+  RawFlags |= Flags.NoRename; // bool
+  RawFlags |= (Flags.IsNotViableToInline << 1);
+  RawFlags |= (Flags.HasInlineAsmMaybeReferencingInternal << 2);
   // Linkage don't need to be remapped at that time for the summary. Any future
   // change to the getEncodedLinkage() function will need to be taken into
   // account here as well.
@@ -1068,7 +1054,7 @@ void ModuleBitcodeWriter::writeComdats() {
 /// Write a record that will eventually hold the word offset of the
 /// module-level VST. For now the offset is 0, which will be backpatched
 /// after the real VST is written. Saves the bit offset to backpatch.
-void BitcodeWriter::writeValueSymbolTableForwardDecl() {
+void BitcodeWriterBase::writeValueSymbolTableForwardDecl() {
   // Write a placeholder value in for the offset of the real VST,
   // which is written after the function blocks so that it can include
   // the offset of each function. The placeholder offset will be
@@ -1115,13 +1101,13 @@ static StringEncoding getStringEncoding(const char *Str, unsigned StrLen) {
 void ModuleBitcodeWriter::writeModuleInfo() {
   // Emit various pieces of data attached to a module.
   if (!M.getTargetTriple().empty())
-    writeStringRecord(bitc::MODULE_CODE_TRIPLE, M.getTargetTriple(),
+    writeStringRecord(Stream, bitc::MODULE_CODE_TRIPLE, M.getTargetTriple(),
                       0 /*TODO*/);
   const std::string &DL = M.getDataLayoutStr();
   if (!DL.empty())
-    writeStringRecord(bitc::MODULE_CODE_DATALAYOUT, DL, 0 /*TODO*/);
+    writeStringRecord(Stream, bitc::MODULE_CODE_DATALAYOUT, DL, 0 /*TODO*/);
   if (!M.getModuleInlineAsm().empty())
-    writeStringRecord(bitc::MODULE_CODE_ASM, M.getModuleInlineAsm(),
+    writeStringRecord(Stream, bitc::MODULE_CODE_ASM, M.getModuleInlineAsm(),
                       0 /*TODO*/);
 
   // Emit information about sections and GC, computing how many there are. Also
@@ -1137,7 +1123,7 @@ void ModuleBitcodeWriter::writeModuleInfo() {
       // Give section names unique ID's.
       unsigned &Entry = SectionMap[GV.getSection()];
       if (!Entry) {
-        writeStringRecord(bitc::MODULE_CODE_SECTIONNAME, GV.getSection(),
+        writeStringRecord(Stream, bitc::MODULE_CODE_SECTIONNAME, GV.getSection(),
                           0 /*TODO*/);
         Entry = SectionMap.size();
       }
@@ -1149,7 +1135,7 @@ void ModuleBitcodeWriter::writeModuleInfo() {
       // Give section names unique ID's.
       unsigned &Entry = SectionMap[F.getSection()];
       if (!Entry) {
-        writeStringRecord(bitc::MODULE_CODE_SECTIONNAME, F.getSection(),
+        writeStringRecord(Stream, bitc::MODULE_CODE_SECTIONNAME, F.getSection(),
                           0 /*TODO*/);
         Entry = SectionMap.size();
       }
@@ -1158,7 +1144,8 @@ void ModuleBitcodeWriter::writeModuleInfo() {
       // Same for GC names.
       unsigned &Entry = GCMap[F.getGC()];
       if (!Entry) {
-        writeStringRecord(bitc::MODULE_CODE_GCNAME, F.getGC(), 0 /*TODO*/);
+        writeStringRecord(Stream, bitc::MODULE_CODE_GCNAME, F.getGC(),
+                          0 /*TODO*/);
         Entry = GCMap.size();
       }
     }
@@ -1535,6 +1522,8 @@ void ModuleBitcodeWriter::writeDIFile(const DIFile *N,
   Record.push_back(N->isDistinct());
   Record.push_back(VE.getMetadataOrNullID(N->getRawFilename()));
   Record.push_back(VE.getMetadataOrNullID(N->getRawDirectory()));
+  Record.push_back(N->getChecksumKind());
+  Record.push_back(VE.getMetadataOrNullID(N->getRawChecksum()));
 
   Stream.EmitRecord(bitc::METADATA_FILE, Record, Abbrev);
   Record.clear();
@@ -1560,6 +1549,7 @@ void ModuleBitcodeWriter::writeDICompileUnit(const DICompileUnit *N,
   Record.push_back(VE.getMetadataOrNullID(N->getImportedEntities().get()));
   Record.push_back(N->getDWOId());
   Record.push_back(VE.getMetadataOrNullID(N->getMacros().get()));
+  Record.push_back(N->getSplitDebugInlining());
 
   Stream.EmitRecord(bitc::METADATA_COMPILE_UNIT, Record, Abbrev);
   Record.clear();
@@ -1622,7 +1612,7 @@ void ModuleBitcodeWriter::writeDILexicalBlockFile(
 void ModuleBitcodeWriter::writeDINamespace(const DINamespace *N,
                                            SmallVectorImpl<uint64_t> &Record,
                                            unsigned Abbrev) {
-  Record.push_back(N->isDistinct());
+  Record.push_back(N->isDistinct() | N->getExportSymbols() << 1);
   Record.push_back(VE.getMetadataOrNullID(N->getScope()));
   Record.push_back(VE.getMetadataOrNullID(N->getFile()));
   Record.push_back(VE.getMetadataOrNullID(N->getRawName()));
@@ -1696,7 +1686,8 @@ void ModuleBitcodeWriter::writeDITemplateValueParameter(
 void ModuleBitcodeWriter::writeDIGlobalVariable(
     const DIGlobalVariable *N, SmallVectorImpl<uint64_t> &Record,
     unsigned Abbrev) {
-  Record.push_back(N->isDistinct());
+  const uint64_t Version = 1 << 1;
+  Record.push_back((uint64_t)N->isDistinct() | Version);
   Record.push_back(VE.getMetadataOrNullID(N->getScope()));
   Record.push_back(VE.getMetadataOrNullID(N->getRawName()));
   Record.push_back(VE.getMetadataOrNullID(N->getRawLinkageName()));
@@ -1705,8 +1696,9 @@ void ModuleBitcodeWriter::writeDIGlobalVariable(
   Record.push_back(VE.getMetadataOrNullID(N->getType()));
   Record.push_back(N->isLocalToUnit());
   Record.push_back(N->isDefinition());
-  Record.push_back(VE.getMetadataOrNullID(N->getRawVariable()));
+  Record.push_back(/* expr */ 0);
   Record.push_back(VE.getMetadataOrNullID(N->getStaticDataMemberDeclaration()));
+  Record.push_back(N->getAlignInBits());
 
   Stream.EmitRecord(bitc::METADATA_GLOBAL_VAR, Record, Abbrev);
   Record.clear();
@@ -1715,7 +1707,21 @@ void ModuleBitcodeWriter::writeDIGlobalVariable(
 void ModuleBitcodeWriter::writeDILocalVariable(
     const DILocalVariable *N, SmallVectorImpl<uint64_t> &Record,
     unsigned Abbrev) {
-  Record.push_back(N->isDistinct());
+  // In order to support all possible bitcode formats in BitcodeReader we need
+  // to distinguish the following cases:
+  // 1) Record has no artificial tag (Record[1]),
+  //   has no obsolete inlinedAt field (Record[9]).
+  //   In this case Record size will be 8, HasAlignment flag is false.
+  // 2) Record has artificial tag (Record[1]),
+  //   has no obsolete inlignedAt field (Record[9]).
+  //   In this case Record size will be 9, HasAlignment flag is false.
+  // 3) Record has both artificial tag (Record[1]) and
+  //   obsolete inlignedAt field (Record[9]).
+  //   In this case Record size will be 10, HasAlignment flag is false.
+  // 4) Record has neither artificial tag, nor inlignedAt field, but
+  //   HasAlignment flag is true and Record[8] contains alignment value.
+  const uint64_t HasAlignmentFlag = 1 << 1;
+  Record.push_back((uint64_t)N->isDistinct() | HasAlignmentFlag);
   Record.push_back(VE.getMetadataOrNullID(N->getScope()));
   Record.push_back(VE.getMetadataOrNullID(N->getRawName()));
   Record.push_back(VE.getMetadataOrNullID(N->getFile()));
@@ -1723,6 +1729,7 @@ void ModuleBitcodeWriter::writeDILocalVariable(
   Record.push_back(VE.getMetadataOrNullID(N->getType()));
   Record.push_back(N->getArg());
   Record.push_back(N->getFlags());
+  Record.push_back(N->getAlignInBits());
 
   Stream.EmitRecord(bitc::METADATA_LOCAL_VAR, Record, Abbrev);
   Record.clear();
@@ -1733,13 +1740,25 @@ void ModuleBitcodeWriter::writeDIExpression(const DIExpression *N,
                                             unsigned Abbrev) {
   Record.reserve(N->getElements().size() + 1);
 
-  Record.push_back(N->isDistinct());
+  const uint64_t HasOpFragmentFlag = 1 << 1;
+  Record.push_back((uint64_t)N->isDistinct() | HasOpFragmentFlag);
   Record.append(N->elements_begin(), N->elements_end());
 
   Stream.EmitRecord(bitc::METADATA_EXPRESSION, Record, Abbrev);
   Record.clear();
 }
 
+void ModuleBitcodeWriter::writeDIGlobalVariableExpression(
+    const DIGlobalVariableExpression *N, SmallVectorImpl<uint64_t> &Record,
+    unsigned Abbrev) {
+  Record.push_back(N->isDistinct());
+  Record.push_back(VE.getMetadataOrNullID(N->getVariable()));
+  Record.push_back(VE.getMetadataOrNullID(N->getExpression()));
+  
+  Stream.EmitRecord(bitc::METADATA_GLOBAL_VAR_EXPR, Record, Abbrev);
+  Record.clear();
+}
+
 void ModuleBitcodeWriter::writeDIObjCProperty(const DIObjCProperty *N,
                                               SmallVectorImpl<uint64_t> &Record,
                                               unsigned Abbrev) {
@@ -1842,8 +1861,16 @@ void ModuleBitcodeWriter::writeMetadataStrings(
   Record.clear();
 }
 
+// Generates an enum to use as an index in the Abbrev array of Metadata record.
+enum MetadataAbbrev : unsigned {
+#define HANDLE_MDNODE_LEAF(CLASS) CLASS##AbbrevID,
+#include "llvm/IR/Metadata.def"
+  LastPlusOne
+};
+
 void ModuleBitcodeWriter::writeMetadataRecords(
-    ArrayRef<const Metadata *> MDs, SmallVectorImpl<uint64_t> &Record) {
+    ArrayRef<const Metadata *> MDs, SmallVectorImpl<uint64_t> &Record,
+    std::vector<unsigned> *MDAbbrevs, std::vector<uint64_t> *IndexPos) {
   if (MDs.empty())
     return;
 
@@ -1852,6 +1879,8 @@ void ModuleBitcodeWriter::writeMetadataRecords(
 #include "llvm/IR/Metadata.def"
 
   for (const Metadata *MD : MDs) {
+    if (IndexPos)
+      IndexPos->push_back(Stream.GetCurrentBitNo());
     if (const MDNode *N = dyn_cast<MDNode>(MD)) {
       assert(N->isResolved() && "Expected forward references to be resolved");
 
@@ -1860,7 +1889,11 @@ void ModuleBitcodeWriter::writeMetadataRecords(
         llvm_unreachable("Invalid MDNode subclass");
 #define HANDLE_MDNODE_LEAF(CLASS)                                              \
   case Metadata::CLASS##Kind:                                                  \
-    write##CLASS(cast<CLASS>(N), Record, CLASS##Abbrev);                       \
+    if (MDAbbrevs)                                                             \
+      write##CLASS(cast<CLASS>(N), Record,                                     \
+                   (*MDAbbrevs)[MetadataAbbrev::CLASS##AbbrevID]);             \
+    else                                                                       \
+      write##CLASS(cast<CLASS>(N), Record, CLASS##Abbrev);                     \
     continue;
 #include "llvm/IR/Metadata.def"
       }
@@ -1873,10 +1906,77 @@ void ModuleBitcodeWriter::writeModuleMetadata() {
   if (!VE.hasMDs() && M.named_metadata_empty())
     return;
 
-  Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
+  Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 4);
   SmallVector<uint64_t, 64> Record;
+
+  // Emit all abbrevs upfront, so that the reader can jump in the middle of the
+  // block and load any metadata.
+  std::vector<unsigned> MDAbbrevs;
+
+  MDAbbrevs.resize(MetadataAbbrev::LastPlusOne);
+  MDAbbrevs[MetadataAbbrev::DILocationAbbrevID] = createDILocationAbbrev();
+  MDAbbrevs[MetadataAbbrev::GenericDINodeAbbrevID] =
+      createGenericDINodeAbbrev();
+
+  BitCodeAbbrev *Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_INDEX_OFFSET));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 32));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 32));
+  unsigned OffsetAbbrev = Stream.EmitAbbrev(Abbv);
+
+  Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_INDEX));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
+  unsigned IndexAbbrev = Stream.EmitAbbrev(Abbv);
+
+  // Emit MDStrings together upfront.
   writeMetadataStrings(VE.getMDStrings(), Record);
-  writeMetadataRecords(VE.getNonMDStrings(), Record);
+
+  // We only emit an index for the metadata record if we have more than a given
+  // (naive) threshold of metadatas, otherwise it is not worth it.
+  if (VE.getNonMDStrings().size() > IndexThreshold) {
+    // Write a placeholder value in for the offset of the metadata index,
+    // which is written after the records, so that it can include
+    // the offset of each entry. The placeholder offset will be
+    // updated after all records are emitted.
+    uint64_t Vals[] = {0, 0};
+    Stream.EmitRecord(bitc::METADATA_INDEX_OFFSET, Vals, OffsetAbbrev);
+  }
+
+  // Compute and save the bit offset to the current position, which will be
+  // patched when we emit the index later. We can simply subtract the 64-bit
+  // fixed size from the current bit number to get the location to backpatch.
+  uint64_t IndexOffsetRecordBitPos = Stream.GetCurrentBitNo();
+
+  // This index will contain the bitpos for each individual record.
+  std::vector<uint64_t> IndexPos;
+  IndexPos.reserve(VE.getNonMDStrings().size());
+
+  // Write all the records
+  writeMetadataRecords(VE.getNonMDStrings(), Record, &MDAbbrevs, &IndexPos);
+
+  if (VE.getNonMDStrings().size() > IndexThreshold) {
+    // Now that we have emitted all the records we will emit the index. But
+    // first
+    // backpatch the forward reference so that the reader can skip the records
+    // efficiently.
+    Stream.BackpatchWord64(IndexOffsetRecordBitPos - 64,
+                           Stream.GetCurrentBitNo() - IndexOffsetRecordBitPos);
+
+    // Delta encode the index.
+    uint64_t PreviousValue = IndexOffsetRecordBitPos;
+    for (auto &Elt : IndexPos) {
+      auto EltDelta = Elt - PreviousValue;
+      PreviousValue = Elt;
+      Elt = EltDelta;
+    }
+    // Emit the index record.
+    Stream.EmitRecord(bitc::METADATA_INDEX, IndexPos, IndexAbbrev);
+    IndexPos.clear();
+  }
+
+  // Write the named metadata now.
   writeNamedMetadata(Record);
 
   auto AddDeclAttachedMetadata = [&](const GlobalObject &GO) {
@@ -2196,9 +2296,12 @@ void ModuleBitcodeWriter::writeConstants(unsigned FirstVal, unsigned LastVal,
       case Instruction::GetElementPtr: {
         Code = bitc::CST_CODE_CE_GEP;
         const auto *GO = cast<GEPOperator>(C);
-        if (GO->isInBounds())
-          Code = bitc::CST_CODE_CE_INBOUNDS_GEP;
         Record.push_back(VE.getTypeID(GO->getSourceElementType()));
+        if (Optional<unsigned> Idx = GO->getInRangeIndex()) {
+          Code = bitc::CST_CODE_CE_GEP_WITH_INRANGE_INDEX;
+          Record.push_back((*Idx << 1) | GO->isInBounds());
+        } else if (GO->isInBounds())
+          Code = bitc::CST_CODE_CE_INBOUNDS_GEP;
         for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {
           Record.push_back(VE.getTypeID(C->getOperand(i)->getType()));
           Record.push_back(VE.getValueID(C->getOperand(i)));
@@ -2495,7 +2598,7 @@ void ModuleBitcodeWriter::writeInstruction(const Instruction &I,
 
     // Emit type/value pairs for varargs params.
     if (FTy->isVarArg()) {
-      for (unsigned i = FTy->getNumParams(), e = I.getNumOperands()-3;
+      for (unsigned i = FTy->getNumParams(), e = II->getNumArgOperands();
            i != e; ++i)
         pushValueAndType(I.getOperand(i), InstID, Vals); // vararg
     }
@@ -2736,11 +2839,13 @@ void ModuleBitcodeWriter::writeValueSymbolTable(
     // Get the offset of the VST we are writing, and backpatch it into
     // the VST forward declaration record.
     uint64_t VSTOffset = Stream.GetCurrentBitNo();
-    // The BitcodeStartBit was the stream offset of the actual bitcode
-    // (e.g. excluding any initial darwin header).
+    // The BitcodeStartBit was the stream offset of the identification block.
     VSTOffset -= bitcodeStartBit();
     assert((VSTOffset & 31) == 0 && "VST block not 32-bit aligned");
-    Stream.BackpatchWord(VSTOffsetPlaceholder, VSTOffset / 32);
+    // Note that we add 1 here because the offset is relative to one word
+    // before the start of the identification block, which was historically
+    // always the start of the regular bitcode header.
+    Stream.BackpatchWord(VSTOffsetPlaceholder, VSTOffset / 32 + 1);
   }
 
   Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 4);
@@ -2828,7 +2933,10 @@ void ModuleBitcodeWriter::writeValueSymbolTable(
       // actual bitcode written to the stream).
       uint64_t BitcodeIndex = (*FunctionToBitcodeIndex)[F] - bitcodeStartBit();
       assert((BitcodeIndex & 31) == 0 && "function block not 32-bit aligned");
-      NameVals.push_back(BitcodeIndex / 32);
+      // Note that we add 1 here because the offset is relative to one word
+      // before the start of the identification block, which was historically
+      // always the start of the regular bitcode header.
+      NameVals.push_back(BitcodeIndex / 32 + 1);
 
       Code = bitc::VST_CODE_FNENTRY;
       AbbrevToUse = FnEntry8BitAbbrev;
@@ -2994,7 +3102,8 @@ void ModuleBitcodeWriter::writeFunction(
     }
 
   // Emit names for all the instructions etc.
-  writeValueSymbolTable(F.getValueSymbolTable());
+  if (auto *Symtab = F.getValueSymbolTable())
+    writeValueSymbolTable(*Symtab);
 
   if (NeedsMetadataAttachment)
     writeFunctionMetadataAttachment(F);
@@ -3009,7 +3118,7 @@ void ModuleBitcodeWriter::writeBlockInfo() {
   // We only want to emit block info records for blocks that have multiple
   // instances: CONSTANTS_BLOCK, FUNCTION_BLOCK and VALUE_SYMTAB_BLOCK.
   // Other blocks can define their abbrevs inline.
-  Stream.EnterBlockInfoBlock(2);
+  Stream.EnterBlockInfoBlock();
 
   { // 8-bit fixed-width VST_CODE_ENTRY/VST_CODE_BBENTRY strings.
     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
@@ -3267,30 +3376,21 @@ void ModuleBitcodeWriter::writePerModuleFunctionSummaryRecord(
   NameVals.push_back(ValueID);
 
   FunctionSummary *FS = cast<FunctionSummary>(Summary);
+  if (!FS->type_tests().empty())
+    Stream.EmitRecord(bitc::FS_TYPE_TESTS, FS->type_tests());
+
   NameVals.push_back(getEncodedGVSummaryFlags(FS->flags()));
   NameVals.push_back(FS->instCount());
   NameVals.push_back(FS->refs().size());
 
-  unsigned SizeBeforeRefs = NameVals.size();
   for (auto &RI : FS->refs())
     NameVals.push_back(VE.getValueID(RI.getValue()));
-  // Sort the refs for determinism output, the vector returned by FS->refs() has
-  // been initialized from a DenseSet.
-  std::sort(NameVals.begin() + SizeBeforeRefs, NameVals.end());
 
-  std::vector<FunctionSummary::EdgeTy> Calls = FS->calls();
-  std::sort(Calls.begin(), Calls.end(),
-            [this](const FunctionSummary::EdgeTy &L,
-                   const FunctionSummary::EdgeTy &R) {
-              return getValueId(L.first) < getValueId(R.first);
-            });
   bool HasProfileData = F.getEntryCount().hasValue();
-  for (auto &ECI : Calls) {
+  for (auto &ECI : FS->calls()) {
     NameVals.push_back(getValueId(ECI.first));
-    assert(ECI.second.CallsiteCount > 0 && "Expected at least one callsite");
-    NameVals.push_back(ECI.second.CallsiteCount);
     if (HasProfileData)
-      NameVals.push_back(ECI.second.ProfileCount);
+      NameVals.push_back(static_cast<uint8_t>(ECI.second.Hotness));
   }
 
   unsigned FSAbbrev = (HasProfileData ? FSCallsProfileAbbrev : FSCallsAbbrev);
@@ -3307,13 +3407,18 @@ void ModuleBitcodeWriter::writePerModuleFunctionSummaryRecord(
 void ModuleBitcodeWriter::writeModuleLevelReferences(
     const GlobalVariable &V, SmallVector<uint64_t, 64> &NameVals,
     unsigned FSModRefsAbbrev) {
-  // Only interested in recording variable defs in the summary.
-  if (V.isDeclaration())
+  auto Summaries =
+      Index->findGlobalValueSummaryList(GlobalValue::getGUID(V.getName()));
+  if (Summaries == Index->end()) {
+    // Only declarations should not have a summary (a declaration might however
+    // have a summary if the def was in module level asm).
+    assert(V.isDeclaration());
     return;
+  }
+  auto *Summary = Summaries->second.front().get();
   NameVals.push_back(VE.getValueID(&V));
-  NameVals.push_back(getEncodedGVSummaryFlags(V));
-  auto *Summary = Index->getGlobalValueSummary(V);
   GlobalVarSummary *VS = cast<GlobalVarSummary>(Summary);
+  NameVals.push_back(getEncodedGVSummaryFlags(VS->flags()));
 
   unsigned SizeBeforeRefs = NameVals.size();
   for (auto &RI : VS->refs())
@@ -3330,18 +3435,20 @@ void ModuleBitcodeWriter::writeModuleLevelReferences(
 // Current version for the summary.
 // This is bumped whenever we introduce changes in the way some record are
 // interpreted, like flags for instance.
-static const uint64_t INDEX_VERSION = 1;
+static const uint64_t INDEX_VERSION = 2;
 
 /// Emit the per-module summary section alongside the rest of
 /// the module's bitcode.
 void ModuleBitcodeWriter::writePerModuleGlobalValueSummary() {
-  if (Index->begin() == Index->end())
-    return;
-
   Stream.EnterSubblock(bitc::GLOBALVAL_SUMMARY_BLOCK_ID, 4);
 
   Stream.EmitRecord(bitc::FS_VERSION, ArrayRef<uint64_t>{INDEX_VERSION});
 
+  if (Index->begin() == Index->end()) {
+    Stream.ExitBlock();
+    return;
+  }
+
   // Abbrev for FS_PERMODULE.
   BitCodeAbbrev *Abbv = new BitCodeAbbrev();
   Abbv->Add(BitCodeAbbrevOp(bitc::FS_PERMODULE));
@@ -3349,7 +3456,7 @@ void ModuleBitcodeWriter::writePerModuleGlobalValueSummary() {
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // flags
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // instcount
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4));   // numrefs
-  // numrefs x valueid, n x (valueid, callsitecount)
+  // numrefs x valueid, n x (valueid)
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
   unsigned FSCallsAbbrev = Stream.EmitAbbrev(Abbv);
@@ -3361,7 +3468,7 @@ void ModuleBitcodeWriter::writePerModuleGlobalValueSummary() {
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // flags
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // instcount
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4));   // numrefs
-  // numrefs x valueid, n x (valueid, callsitecount, profilecount)
+  // numrefs x valueid, n x (valueid, hotness)
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
   unsigned FSCallsProfileAbbrev = Stream.EmitAbbrev(Abbv);
@@ -3387,14 +3494,20 @@ void ModuleBitcodeWriter::writePerModuleGlobalValueSummary() {
   // Iterate over the list of functions instead of the Index to
   // ensure the ordering is stable.
   for (const Function &F : M) {
-    if (F.isDeclaration())
-      continue;
     // Summary emission does not support anonymous functions, they have to
     // renamed using the anonymous function renaming pass.
     if (!F.hasName())
       report_fatal_error("Unexpected anonymous function when writing summary");
 
-    auto *Summary = Index->getGlobalValueSummary(F);
+    auto Summaries =
+        Index->findGlobalValueSummaryList(GlobalValue::getGUID(F.getName()));
+    if (Summaries == Index->end()) {
+      // Only declarations should not have a summary (a declaration might
+      // however have a summary if the def was in module level asm).
+      assert(F.isDeclaration());
+      continue;
+    }
+    auto *Summary = Summaries->second.front().get();
     writePerModuleFunctionSummaryRecord(NameVals, Summary, VE.getValueID(&F),
                                         FSCallsAbbrev, FSCallsProfileAbbrev, F);
   }
@@ -3412,7 +3525,9 @@ void ModuleBitcodeWriter::writePerModuleGlobalValueSummary() {
     auto AliasId = VE.getValueID(&A);
     auto AliaseeId = VE.getValueID(Aliasee);
     NameVals.push_back(AliasId);
-    NameVals.push_back(getEncodedGVSummaryFlags(A));
+    auto *Summary = Index->getGlobalValueSummary(A);
+    AliasSummary *AS = cast<AliasSummary>(Summary);
+    NameVals.push_back(getEncodedGVSummaryFlags(AS->flags()));
     NameVals.push_back(AliaseeId);
     Stream.EmitRecord(bitc::FS_ALIAS, NameVals, FSAliasAbbrev);
     NameVals.clear();
@@ -3434,7 +3549,7 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // flags
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // instcount
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4));   // numrefs
-  // numrefs x valueid, n x (valueid, callsitecount)
+  // numrefs x valueid, n x (valueid)
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
   unsigned FSCallsAbbrev = Stream.EmitAbbrev(Abbv);
@@ -3447,7 +3562,7 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // flags
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // instcount
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4));   // numrefs
-  // numrefs x valueid, n x (valueid, callsitecount, profilecount)
+  // numrefs x valueid, n x (valueid, hotness)
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
   unsigned FSCallsProfileAbbrev = Stream.EmitAbbrev(Abbv);
@@ -3522,6 +3637,9 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
     }
 
     auto *FS = cast<FunctionSummary>(S);
+    if (!FS->type_tests().empty())
+      Stream.EmitRecord(bitc::FS_TYPE_TESTS, FS->type_tests());
+
     NameVals.push_back(ValueId);
     NameVals.push_back(Index.getModuleId(FS->modulePath()));
     NameVals.push_back(getEncodedGVSummaryFlags(FS->flags()));
@@ -3534,7 +3652,7 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
 
     bool HasProfileData = false;
     for (auto &EI : FS->calls()) {
-      HasProfileData |= EI.second.ProfileCount != 0;
+      HasProfileData |= EI.second.Hotness != CalleeInfo::HotnessType::Unknown;
       if (HasProfileData)
         break;
     }
@@ -3545,10 +3663,8 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
       if (!hasValueId(EI.first.getGUID()))
         continue;
       NameVals.push_back(getValueId(EI.first.getGUID()));
-      assert(EI.second.CallsiteCount > 0 && "Expected at least one callsite");
-      NameVals.push_back(EI.second.CallsiteCount);
       if (HasProfileData)
-        NameVals.push_back(EI.second.ProfileCount);
+        NameVals.push_back(static_cast<uint8_t>(EI.second.Hotness));
     }
 
     unsigned FSAbbrev = (HasProfileData ? FSCallsProfileAbbrev : FSCallsAbbrev);
@@ -3580,7 +3696,9 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
   Stream.ExitBlock();
 }
 
-void ModuleBitcodeWriter::writeIdentificationBlock() {
+/// Create the "IDENTIFICATION_BLOCK_ID" containing a single string with the
+/// current llvm version, and a record for the epoch number.
+void writeIdentificationBlock(BitstreamWriter &Stream) {
   Stream.EnterSubblock(bitc::IDENTIFICATION_BLOCK_ID, 5);
 
   // Write the "user readable" string identifying the bitcode producer
@@ -3589,7 +3707,7 @@ void ModuleBitcodeWriter::writeIdentificationBlock() {
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
   auto StringAbbrev = Stream.EmitAbbrev(Abbv);
-  writeStringRecord(bitc::IDENTIFICATION_CODE_STRING,
+  writeStringRecord(Stream, bitc::IDENTIFICATION_CODE_STRING,
                     "LLVM" LLVM_VERSION_STRING, StringAbbrev);
 
   // Write the epoch version
@@ -3608,39 +3726,19 @@ void ModuleBitcodeWriter::writeModuleHash(size_t BlockStartPos) {
   SHA1 Hasher;
   Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&(Buffer)[BlockStartPos],
                                   Buffer.size() - BlockStartPos));
-  auto Hash = Hasher.result();
-  SmallVector<uint64_t, 20> Vals;
-  auto LShift = [&](unsigned char Val, unsigned Amount)
-                    -> uint64_t { return ((uint64_t)Val) << Amount; };
+  StringRef Hash = Hasher.result();
+  uint32_t Vals[5];
   for (int Pos = 0; Pos < 20; Pos += 4) {
-    uint32_t SubHash = LShift(Hash[Pos + 0], 24);
-    SubHash |= LShift(Hash[Pos + 1], 16) | LShift(Hash[Pos + 2], 8) |
-               (unsigned)(unsigned char)Hash[Pos + 3];
-    Vals.push_back(SubHash);
+    Vals[Pos / 4] = support::endian::read32be(Hash.data() + Pos);
   }
 
   // Emit the finished record.
   Stream.EmitRecord(bitc::MODULE_CODE_HASH, Vals);
 }
 
-void BitcodeWriter::write() {
-  // Emit the file header first.
-  writeBitcodeHeader();
+void ModuleBitcodeWriter::write() {
+  writeIdentificationBlock(Stream);
 
-  writeBlocks();
-}
-
-void ModuleBitcodeWriter::writeBlocks() {
-  writeIdentificationBlock();
-  writeModule();
-}
-
-void IndexBitcodeWriter::writeBlocks() {
-  // Index contains only a single outer (module) block.
-  writeIndex();
-}
-
-void ModuleBitcodeWriter::writeModule() {
   Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
   size_t BlockStartPos = Buffer.size();
 
@@ -3769,7 +3867,7 @@ static void emitDarwinBCHeaderAndTrailer(SmallVectorImpl<char> &Buffer,
 }
 
 /// Helper to write the header common to all bitcode files.
-void BitcodeWriter::writeBitcodeHeader() {
+static void writeBitcodeHeader(BitstreamWriter &Stream) {
   // Emit the file header.
   Stream.Emit((unsigned)'B', 8);
   Stream.Emit((unsigned)'C', 8);
@@ -3779,6 +3877,22 @@ void BitcodeWriter::writeBitcodeHeader() {
   Stream.Emit(0xD, 4);
 }
 
+BitcodeWriter::BitcodeWriter(SmallVectorImpl<char> &Buffer)
+    : Buffer(Buffer), Stream(new BitstreamWriter(Buffer)) {
+  writeBitcodeHeader(*Stream);
+}
+
+BitcodeWriter::~BitcodeWriter() = default;
+
+void BitcodeWriter::writeModule(const Module *M,
+                                bool ShouldPreserveUseListOrder,
+                                const ModuleSummaryIndex *Index,
+                                bool GenerateHash) {
+  ModuleBitcodeWriter ModuleWriter(
+      M, Buffer, *Stream, ShouldPreserveUseListOrder, Index, GenerateHash);
+  ModuleWriter.write();
+}
+
 /// WriteBitcodeToFile - Write the specified module to the specified output
 /// stream.
 void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out,
@@ -3794,10 +3908,8 @@ void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out,
   if (TT.isOSDarwin() || TT.isOSBinFormatMachO())
     Buffer.insert(Buffer.begin(), BWH_HeaderSize, 0);
 
-  // Emit the module into the buffer.
-  ModuleBitcodeWriter ModuleWriter(M, Buffer, ShouldPreserveUseListOrder, Index,
-                                   GenerateHash);
-  ModuleWriter.write();
+  BitcodeWriter Writer(Buffer);
+  Writer.writeModule(M, ShouldPreserveUseListOrder, Index, GenerateHash);
 
   if (TT.isOSDarwin() || TT.isOSBinFormatMachO())
     emitDarwinBCHeaderAndTrailer(Buffer, TT);
@@ -3806,7 +3918,7 @@ void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out,
   Out.write((char*)&Buffer.front(), Buffer.size());
 }
 
-void IndexBitcodeWriter::writeIndex() {
+void IndexBitcodeWriter::write() {
   Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
 
   SmallVector<unsigned, 1> Vals;
@@ -3836,11 +3948,14 @@ void IndexBitcodeWriter::writeIndex() {
 // index for a distributed backend, provide a \p ModuleToSummariesForIndex map.
 void llvm::WriteIndexToFile(
     const ModuleSummaryIndex &Index, raw_ostream &Out,
-    std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex) {
+    const std::map<std::string, GVSummaryMapTy> *ModuleToSummariesForIndex) {
   SmallVector<char, 0> Buffer;
   Buffer.reserve(256 * 1024);
 
-  IndexBitcodeWriter IndexWriter(Buffer, Index, ModuleToSummariesForIndex);
+  BitstreamWriter Stream(Buffer);
+  writeBitcodeHeader(Stream);
+
+  IndexBitcodeWriter IndexWriter(Stream, Index, ModuleToSummariesForIndex);
   IndexWriter.write();
 
   Out.write((char *)&Buffer.front(), Buffer.size());