Support for function summary index bitcode sections and files.

Summary:
The bitcode format is described in this document:
  https://drive.google.com/file/d/0B036uwnWM6RWdnBLakxmeDdOeXc/view
For more info on ThinLTO see:
  https://sites.google.com/site/llvmthinlto

The first customer is ThinLTO, however the data structures are designed
and named more generally based on prior feedback. There are a few
comments regarding how certain interfaces are used by ThinLTO, and the
options added here to gold currently have ThinLTO-specific names as the
behavior they provoke is currently ThinLTO-specific.

This patch includes support for generating per-module function indexes,
the combined index file via the gold plugin, and several tests
(more are included with the associated clang patch D11908).

Reviewers: dexonsmith, davidxl, joker.eph

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13107

llvm-svn: 249270
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 165ab6e..c93b4af 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -27,6 +27,7 @@
 #include "llvm/IR/Module.h"
 #include "llvm/IR/OperandTraits.h"
 #include "llvm/IR/Operator.h"
+#include "llvm/IR/FunctionInfo.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/Support/DataStream.h"
 #include "llvm/Support/ManagedStatic.h"
@@ -395,6 +396,96 @@
       Function *F,
       DenseMap<Function *, uint64_t>::iterator DeferredFunctionInfoIterator);
 };
+
+/// Class to manage reading and parsing function summary index bitcode
+/// files/sections.
+class FunctionIndexBitcodeReader {
+  LLVMContext &Context;
+  DiagnosticHandlerFunction DiagnosticHandler;
+
+  /// Eventually points to the function index built during parsing.
+  FunctionInfoIndex *TheIndex = nullptr;
+
+  std::unique_ptr<MemoryBuffer> Buffer;
+  std::unique_ptr<BitstreamReader> StreamFile;
+  BitstreamCursor Stream;
+
+  /// \brief Used to indicate whether we are doing lazy parsing of summary data.
+  ///
+  /// If false, the summary section is fully parsed into the index during
+  /// the initial parse. Otherwise, if true, the caller is expected to
+  /// invoke \a readFunctionSummary for each summary needed, and the summary
+  /// section is thus parsed lazily.
+  bool IsLazy = false;
+
+  /// Used to indicate whether caller only wants to check for the presence
+  /// of the function summary bitcode section. All blocks are skipped,
+  /// but the SeenFuncSummary boolean is set.
+  bool CheckFuncSummaryPresenceOnly = false;
+
+  /// Indicates whether we have encountered a function summary section
+  /// yet during parsing, used when checking if file contains function
+  /// summary section.
+  bool SeenFuncSummary = false;
+
+  /// \brief Map populated during function summary section parsing, and
+  /// consumed during ValueSymbolTable parsing.
+  ///
+  /// Used to correlate summary records with VST entries. For the per-module
+  /// index this maps the ValueID to the parsed function summary, and
+  /// for the combined index this maps the summary record's bitcode
+  /// offset to the function summary (since in the combined index the
+  /// VST records do not hold value IDs but rather hold the function
+  /// summary record offset).
+  DenseMap<uint64_t, std::unique_ptr<FunctionSummary>> SummaryMap;
+
+  /// Map populated during module path string table parsing, from the
+  /// module ID to a string reference owned by the index's module
+  /// path string table, used to correlate with combined index function
+  /// summary records.
+  DenseMap<uint64_t, StringRef> ModuleIdMap;
+
+ public:
+  std::error_code error(BitcodeError E, const Twine &Message);
+  std::error_code error(BitcodeError E);
+  std::error_code error(const Twine &Message);
+
+  FunctionIndexBitcodeReader(MemoryBuffer *Buffer, LLVMContext &Context,
+                             DiagnosticHandlerFunction DiagnosticHandler,
+                             bool IsLazy = false,
+                             bool CheckFuncSummaryPresenceOnly = false);
+  FunctionIndexBitcodeReader(LLVMContext &Context,
+                             DiagnosticHandlerFunction DiagnosticHandler,
+                             bool IsLazy = false,
+                             bool CheckFuncSummaryPresenceOnly = false);
+  ~FunctionIndexBitcodeReader() { freeState(); }
+
+  void freeState();
+
+  void releaseBuffer();
+
+  /// Check if the parser has encountered a function summary section.
+  bool foundFuncSummary() { return SeenFuncSummary; }
+
+  /// \brief Main interface to parsing a bitcode buffer.
+  /// \returns true if an error occurred.
+  std::error_code parseSummaryIndexInto(std::unique_ptr<DataStreamer> Streamer,
+                                        FunctionInfoIndex *I);
+
+  /// \brief Interface for parsing a function summary lazily.
+  std::error_code parseFunctionSummary(std::unique_ptr<DataStreamer> Streamer,
+                                       FunctionInfoIndex *I,
+                                       size_t FunctionSummaryOffset);
+
+ private:
+  std::error_code parseModule();
+  std::error_code parseValueSymbolTable();
+  std::error_code parseEntireSummary();
+  std::error_code parseModuleStringTable();
+  std::error_code initStream(std::unique_ptr<DataStreamer> Streamer);
+  std::error_code initStreamFromBuffer();
+  std::error_code initLazyStream(std::unique_ptr<DataStreamer> Streamer);
+};
 } // namespace
 
 BitcodeDiagnosticInfo::BitcodeDiagnosticInfo(std::error_code EC,
@@ -3377,6 +3468,19 @@
   }
 }
 
+/// Helper to read the header common to all bitcode files.
+static bool hasValidBitcodeHeader(BitstreamCursor &Stream) {
+  // Sniff for the signature.
+  if (Stream.Read(8) != 'B' ||
+      Stream.Read(8) != 'C' ||
+      Stream.Read(4) != 0x0 ||
+      Stream.Read(4) != 0xC ||
+      Stream.Read(4) != 0xE ||
+      Stream.Read(4) != 0xD)
+    return false;
+  return true;
+}
+
 std::error_code
 BitcodeReader::parseBitcodeInto(std::unique_ptr<DataStreamer> Streamer,
                                 Module *M, bool ShouldLazyLoadMetadata) {
@@ -3386,13 +3490,7 @@
     return EC;
 
   // Sniff for the signature.
-  if (Stream.Read(8) != 'B' ||
-      Stream.Read(8) != 'C' ||
-      Stream.Read(4) != 0x0 ||
-      Stream.Read(4) != 0xC ||
-      Stream.Read(4) != 0xE ||
-      Stream.Read(4) != 0xD)
-    return error("Invalid bitcode signature");
+  if (!hasValidBitcodeHeader(Stream)) return error("Invalid bitcode signature");
 
   // We expect a number of well-defined blocks, though we don't necessarily
   // need to understand them all.
@@ -3459,13 +3557,7 @@
     return EC;
 
   // Sniff for the signature.
-  if (Stream.Read(8) != 'B' ||
-      Stream.Read(8) != 'C' ||
-      Stream.Read(4) != 0x0 ||
-      Stream.Read(4) != 0xC ||
-      Stream.Read(4) != 0xE ||
-      Stream.Read(4) != 0xD)
-    return error("Invalid bitcode signature");
+  if (!hasValidBitcodeHeader(Stream)) return error("Invalid bitcode signature");
 
   // We expect a number of well-defined blocks, though we don't necessarily
   // need to understand them all.
@@ -5060,6 +5152,405 @@
   return std::error_code();
 }
 
+std::error_code FunctionIndexBitcodeReader::error(BitcodeError E,
+                                                  const Twine &Message) {
+  return ::error(DiagnosticHandler, make_error_code(E), Message);
+}
+
+std::error_code FunctionIndexBitcodeReader::error(const Twine &Message) {
+  return ::error(DiagnosticHandler,
+                 make_error_code(BitcodeError::CorruptedBitcode), Message);
+}
+
+std::error_code FunctionIndexBitcodeReader::error(BitcodeError E) {
+  return ::error(DiagnosticHandler, make_error_code(E));
+}
+
+FunctionIndexBitcodeReader::FunctionIndexBitcodeReader(
+    MemoryBuffer *Buffer, LLVMContext &Context,
+    DiagnosticHandlerFunction DiagnosticHandler, bool IsLazy,
+    bool CheckFuncSummaryPresenceOnly)
+    : Context(Context),
+      DiagnosticHandler(getDiagHandler(DiagnosticHandler, Context)),
+      Buffer(Buffer),
+      IsLazy(IsLazy),
+      CheckFuncSummaryPresenceOnly(CheckFuncSummaryPresenceOnly) {}
+
+FunctionIndexBitcodeReader::FunctionIndexBitcodeReader(
+    LLVMContext &Context, DiagnosticHandlerFunction DiagnosticHandler,
+    bool IsLazy, bool CheckFuncSummaryPresenceOnly)
+    : Context(Context),
+      DiagnosticHandler(getDiagHandler(DiagnosticHandler, Context)),
+      Buffer(nullptr),
+      IsLazy(IsLazy),
+      CheckFuncSummaryPresenceOnly(CheckFuncSummaryPresenceOnly) {}
+
+void FunctionIndexBitcodeReader::freeState() { Buffer = nullptr; }
+
+void FunctionIndexBitcodeReader::releaseBuffer() { Buffer.release(); }
+
+// Specialized value symbol table parser used when reading function index
+// blocks where we don't actually create global values.
+// At the end of this routine the function index is populated with a map
+// from function name to FunctionInfo. The function info contains
+// the function block's bitcode offset as well as the offset into the
+// function summary section.
+std::error_code FunctionIndexBitcodeReader::parseValueSymbolTable() {
+  if (Stream.EnterSubBlock(bitc::VALUE_SYMTAB_BLOCK_ID))
+    return error("Invalid record");
+
+  SmallVector<uint64_t, 64> Record;
+
+  // Read all the records for this value table.
+  SmallString<128> ValueName;
+  while (1) {
+    BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
+
+    switch (Entry.Kind) {
+      case BitstreamEntry::SubBlock:  // Handled for us already.
+      case BitstreamEntry::Error:
+        return error("Malformed block");
+      case BitstreamEntry::EndBlock:
+        return std::error_code();
+      case BitstreamEntry::Record:
+        // The interesting case.
+        break;
+    }
+
+    // Read a record.
+    Record.clear();
+    switch (Stream.readRecord(Entry.ID, Record)) {
+      default:  // Default behavior: ignore (e.g. VST_CODE_BBENTRY records).
+        break;
+      case bitc::VST_CODE_FNENTRY: {
+        // VST_FNENTRY: [valueid, offset, namechar x N]
+        if (convertToString(Record, 2, ValueName))
+          return error("Invalid record");
+        unsigned ValueID = Record[0];
+        uint64_t FuncOffset = Record[1];
+        std::unique_ptr<FunctionInfo> FuncInfo =
+            llvm::make_unique<FunctionInfo>(FuncOffset);
+        if (foundFuncSummary() && !IsLazy) {
+          DenseMap<uint64_t, std::unique_ptr<FunctionSummary>>::iterator SMI =
+              SummaryMap.find(ValueID);
+          assert(SMI != SummaryMap.end() && "Summary info not found");
+          FuncInfo->setFunctionSummary(std::move(SMI->second));
+        }
+        TheIndex->addFunctionInfo(ValueName, std::move(FuncInfo));
+
+        ValueName.clear();
+        break;
+      }
+      case bitc::VST_CODE_COMBINED_FNENTRY: {
+        // VST_FNENTRY: [offset, namechar x N]
+        if (convertToString(Record, 1, ValueName))
+          return error("Invalid record");
+        uint64_t FuncSummaryOffset = Record[0];
+        std::unique_ptr<FunctionInfo> FuncInfo =
+            llvm::make_unique<FunctionInfo>(FuncSummaryOffset);
+        if (foundFuncSummary() && !IsLazy) {
+          DenseMap<uint64_t, std::unique_ptr<FunctionSummary>>::iterator SMI =
+              SummaryMap.find(FuncSummaryOffset);
+          assert(SMI != SummaryMap.end() && "Summary info not found");
+          FuncInfo->setFunctionSummary(std::move(SMI->second));
+        }
+        TheIndex->addFunctionInfo(ValueName, std::move(FuncInfo));
+
+        ValueName.clear();
+        break;
+      }
+    }
+  }
+}
+
+// Parse just the blocks needed for function index building out of the module.
+// At the end of this routine the function Index is populated with a map
+// from function name to FunctionInfo. The function info contains
+// either the parsed function summary information (when parsing summaries
+// eagerly), or just to the function summary record's offset
+// if parsing lazily (IsLazy).
+std::error_code FunctionIndexBitcodeReader::parseModule() {
+  if (Stream.EnterSubBlock(bitc::MODULE_BLOCK_ID))
+    return error("Invalid record");
+
+  // Read the function index for this module.
+  while (1) {
+    BitstreamEntry Entry = Stream.advance();
+
+    switch (Entry.Kind) {
+      case BitstreamEntry::Error:
+        return error("Malformed block");
+      case BitstreamEntry::EndBlock:
+        return std::error_code();
+
+      case BitstreamEntry::SubBlock:
+        if (CheckFuncSummaryPresenceOnly) {
+          if (Entry.ID == bitc::FUNCTION_SUMMARY_BLOCK_ID)
+            SeenFuncSummary = true;
+          if (Stream.SkipBlock()) return error("Invalid record");
+          // No need to parse the rest since we found the summary.
+          return std::error_code();
+        }
+        switch (Entry.ID) {
+          default:  // Skip unknown content.
+            if (Stream.SkipBlock()) return error("Invalid record");
+            break;
+          case bitc::BLOCKINFO_BLOCK_ID:
+            // Need to parse these to get abbrev ids (e.g. for VST)
+            if (Stream.ReadBlockInfoBlock()) return error("Malformed block");
+            break;
+          case bitc::VALUE_SYMTAB_BLOCK_ID:
+            if (std::error_code EC = parseValueSymbolTable()) return EC;
+            break;
+          case bitc::FUNCTION_SUMMARY_BLOCK_ID:
+            SeenFuncSummary = true;
+            if (IsLazy) {
+              // Lazy parsing of summary info, skip it.
+              if (Stream.SkipBlock()) return error("Invalid record");
+            } else if (std::error_code EC = parseEntireSummary())
+              return EC;
+            break;
+          case bitc::MODULE_STRTAB_BLOCK_ID:
+            if (std::error_code EC = parseModuleStringTable()) return EC;
+            break;
+        }
+        continue;
+
+      case BitstreamEntry::Record:
+        Stream.skipRecord(Entry.ID);
+        continue;
+    }
+  }
+}
+
+// Eagerly parse the entire function summary block (i.e. for all functions
+// in the index). This populates the FunctionSummary objects in
+// the index.
+std::error_code FunctionIndexBitcodeReader::parseEntireSummary() {
+  if (Stream.EnterSubBlock(bitc::FUNCTION_SUMMARY_BLOCK_ID))
+    return error("Invalid record");
+
+  SmallVector<uint64_t, 64> Record;
+
+  while (1) {
+    BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
+
+    switch (Entry.Kind) {
+      case BitstreamEntry::SubBlock:  // Handled for us already.
+      case BitstreamEntry::Error:
+        return error("Malformed block");
+      case BitstreamEntry::EndBlock:
+        return std::error_code();
+      case BitstreamEntry::Record:
+        // The interesting case.
+        break;
+    }
+
+    // Read a record. The record format depends on whether this
+    // is a per-module index or a combined index file. In the per-module
+    // case the records contain the associated value's ID for correlation
+    // with VST entries. In the combined index the correlation is done
+    // via the bitcode offset of the summary records (which were saved
+    // in the combined index VST entries). The records also contain
+    // information used for ThinLTO renaming and importing.
+    Record.clear();
+    uint64_t CurRecordBit = Stream.GetCurrentBitNo();
+    switch (Stream.readRecord(Entry.ID, Record)) {
+      default:  // Default behavior: ignore.
+        break;
+      // FS_PERMODULE_ENTRY: [valueid, islocal, instcount]
+      case bitc::FS_CODE_PERMODULE_ENTRY: {
+        unsigned ValueID = Record[0];
+        bool IsLocal = Record[1];
+        unsigned InstCount = Record[2];
+        std::unique_ptr<FunctionSummary> FS =
+            llvm::make_unique<FunctionSummary>(InstCount);
+        FS->setLocalFunction(IsLocal);
+        // The module path string ref set in the summary must be owned by the
+        // index's module string table. Since we don't have a module path
+        // string table section in the per-module index, we create a single
+        // module path string table entry with an empty (0) ID to take
+        // ownership.
+        FS->setModulePath(
+            TheIndex->addModulePath(Buffer->getBufferIdentifier(), 0));
+        SummaryMap[ValueID] = std::move(FS);
+      }
+      // FS_COMBINED_ENTRY: [modid, instcount]
+      case bitc::FS_CODE_COMBINED_ENTRY: {
+        uint64_t ModuleId = Record[0];
+        unsigned InstCount = Record[1];
+        std::unique_ptr<FunctionSummary> FS =
+            llvm::make_unique<FunctionSummary>(InstCount);
+        FS->setModulePath(ModuleIdMap[ModuleId]);
+        SummaryMap[CurRecordBit] = std::move(FS);
+      }
+    }
+  }
+  llvm_unreachable("Exit infinite loop");
+}
+
+// Parse the  module string table block into the Index.
+// This populates the ModulePathStringTable map in the index.
+std::error_code FunctionIndexBitcodeReader::parseModuleStringTable() {
+  if (Stream.EnterSubBlock(bitc::MODULE_STRTAB_BLOCK_ID))
+    return error("Invalid record");
+
+  SmallVector<uint64_t, 64> Record;
+
+  SmallString<128> ModulePath;
+  while (1) {
+    BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
+
+    switch (Entry.Kind) {
+      case BitstreamEntry::SubBlock:  // Handled for us already.
+      case BitstreamEntry::Error:
+        return error("Malformed block");
+      case BitstreamEntry::EndBlock:
+        return std::error_code();
+      case BitstreamEntry::Record:
+        // The interesting case.
+        break;
+    }
+
+    Record.clear();
+    switch (Stream.readRecord(Entry.ID, Record)) {
+      default:  // Default behavior: ignore.
+        break;
+      case bitc::MST_CODE_ENTRY: {
+        // MST_ENTRY: [modid, namechar x N]
+        if (convertToString(Record, 1, ModulePath))
+          return error("Invalid record");
+        uint64_t ModuleId = Record[0];
+        StringRef ModulePathInMap =
+            TheIndex->addModulePath(ModulePath, ModuleId);
+        ModuleIdMap[ModuleId] = ModulePathInMap;
+        ModulePath.clear();
+        break;
+      }
+    }
+  }
+  llvm_unreachable("Exit infinite loop");
+}
+
+// Parse the function info index from the bitcode streamer into the given index.
+std::error_code FunctionIndexBitcodeReader::parseSummaryIndexInto(
+    std::unique_ptr<DataStreamer> Streamer, FunctionInfoIndex *I) {
+  TheIndex = I;
+
+  if (std::error_code EC = initStream(std::move(Streamer))) return EC;
+
+  // Sniff for the signature.
+  if (!hasValidBitcodeHeader(Stream)) return error("Invalid bitcode signature");
+
+  // We expect a number of well-defined blocks, though we don't necessarily
+  // need to understand them all.
+  while (1) {
+    if (Stream.AtEndOfStream()) {
+      // We didn't really read a proper Module block.
+      return error("Malformed block");
+    }
+
+    BitstreamEntry Entry =
+        Stream.advance(BitstreamCursor::AF_DontAutoprocessAbbrevs);
+
+    if (Entry.Kind != BitstreamEntry::SubBlock) return error("Malformed block");
+
+    // If we see a MODULE_BLOCK, parse it to find the blocks needed for
+    // building the function summary index.
+    if (Entry.ID == bitc::MODULE_BLOCK_ID) return parseModule();
+
+    if (Stream.SkipBlock()) return error("Invalid record");
+  }
+}
+
+// Parse the function information at the given offset in the buffer into
+// the index. Used to support lazy parsing of function summaries from the
+// combined index during importing.
+// TODO: This function is not yet complete as it won't have a consumer
+// until ThinLTO function importing is added.
+std::error_code FunctionIndexBitcodeReader::parseFunctionSummary(
+    std::unique_ptr<DataStreamer> Streamer, FunctionInfoIndex *I,
+    size_t FunctionSummaryOffset) {
+  TheIndex = I;
+
+  if (std::error_code EC = initStream(std::move(Streamer))) return EC;
+
+  // Sniff for the signature.
+  if (!hasValidBitcodeHeader(Stream)) return error("Invalid bitcode signature");
+
+  Stream.JumpToBit(FunctionSummaryOffset);
+
+  BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
+
+  switch (Entry.Kind) {
+    default:
+      return error("Malformed block");
+    case BitstreamEntry::Record:
+      // The expected case.
+      break;
+  }
+
+  // TODO: Read a record. This interface will be completed when ThinLTO
+  // importing is added so that it can be tested.
+  SmallVector<uint64_t, 64> Record;
+  switch (Stream.readRecord(Entry.ID, Record)) {
+    default:
+      return error("Invalid record");
+  }
+
+  return std::error_code();
+}
+
+std::error_code FunctionIndexBitcodeReader::initStream(
+    std::unique_ptr<DataStreamer> Streamer) {
+  if (Streamer) return initLazyStream(std::move(Streamer));
+  return initStreamFromBuffer();
+}
+
+std::error_code FunctionIndexBitcodeReader::initStreamFromBuffer() {
+  const unsigned char *BufPtr = (const unsigned char *)Buffer->getBufferStart();
+  const unsigned char *BufEnd = BufPtr + Buffer->getBufferSize();
+
+  if (Buffer->getBufferSize() & 3) return error("Invalid bitcode signature");
+
+  // If we have a wrapper header, parse it and ignore the non-bc file contents.
+  // The magic number is 0x0B17C0DE stored in little endian.
+  if (isBitcodeWrapper(BufPtr, BufEnd))
+    if (SkipBitcodeWrapperHeader(BufPtr, BufEnd, true))
+      return error("Invalid bitcode wrapper header");
+
+  StreamFile.reset(new BitstreamReader(BufPtr, BufEnd));
+  Stream.init(&*StreamFile);
+
+  return std::error_code();
+}
+
+std::error_code FunctionIndexBitcodeReader::initLazyStream(
+    std::unique_ptr<DataStreamer> Streamer) {
+  // Check and strip off the bitcode wrapper; BitstreamReader expects never to
+  // see it.
+  auto OwnedBytes =
+      llvm::make_unique<StreamingMemoryObject>(std::move(Streamer));
+  StreamingMemoryObject &Bytes = *OwnedBytes;
+  StreamFile = llvm::make_unique<BitstreamReader>(std::move(OwnedBytes));
+  Stream.init(&*StreamFile);
+
+  unsigned char buf[16];
+  if (Bytes.readBytes(buf, 16, 0) != 16)
+    return error("Invalid bitcode signature");
+
+  if (!isBitcode(buf, buf + 16)) return error("Invalid bitcode signature");
+
+  if (isBitcodeWrapper(buf, buf + 4)) {
+    const unsigned char *bitcodeStart = buf;
+    const unsigned char *bitcodeEnd = buf + 16;
+    SkipBitcodeWrapperHeader(bitcodeStart, bitcodeEnd, false);
+    Bytes.dropLeadingBytes(bitcodeStart - buf);
+    Bytes.setKnownObjectSize(bitcodeEnd - bitcodeStart);
+  }
+  return std::error_code();
+}
+
 namespace {
 class BitcodeErrorCategoryType : public std::error_category {
   const char *name() const LLVM_NOEXCEPT override {
@@ -5181,3 +5672,81 @@
     return "";
   return Triple.get();
 }
+
+// Parse the specified bitcode buffer, returning the function info index.
+// If IsLazy is false, parse the entire function summary into
+// the index. Otherwise skip the function summary section, and only create
+// an index object with a map from function name to function summary offset.
+// The index is used to perform lazy function summary reading later.
+ErrorOr<std::unique_ptr<FunctionInfoIndex>> llvm::getFunctionInfoIndex(
+    MemoryBufferRef Buffer, LLVMContext &Context,
+    DiagnosticHandlerFunction DiagnosticHandler, bool IsLazy) {
+  std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
+  FunctionIndexBitcodeReader R(Buf.get(), Context, DiagnosticHandler, IsLazy);
+
+  std::unique_ptr<FunctionInfoIndex> Index =
+      llvm::make_unique<FunctionInfoIndex>();
+
+  auto cleanupOnError = [&](std::error_code EC) {
+    R.releaseBuffer();  // Never take ownership on error.
+    return EC;
+  };
+
+  if (std::error_code EC = R.parseSummaryIndexInto(nullptr, Index.get()))
+    return cleanupOnError(EC);
+
+  Buf.release();  // The FunctionIndexBitcodeReader owns it now.
+  return std::move(Index);
+}
+
+// Check if the given bitcode buffer contains a function summary block.
+bool llvm::hasFunctionSummary(MemoryBufferRef Buffer, LLVMContext &Context,
+                              DiagnosticHandlerFunction DiagnosticHandler) {
+  std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
+  FunctionIndexBitcodeReader R(Buf.get(), Context, DiagnosticHandler, false,
+                               true);
+
+  auto cleanupOnError = [&](std::error_code EC) {
+    R.releaseBuffer();  // Never take ownership on error.
+    return false;
+  };
+
+  if (std::error_code EC = R.parseSummaryIndexInto(nullptr, nullptr))
+    return cleanupOnError(EC);
+
+  Buf.release();  // The FunctionIndexBitcodeReader owns it now.
+  return R.foundFuncSummary();
+}
+
+// This method supports lazy reading of function summary data from the combined
+// index during ThinLTO function importing. When reading the combined index
+// file, getFunctionInfoIndex is first invoked with IsLazy=true.
+// Then this method is called for each function considered for importing,
+// to parse the summary information for the given function name into
+// the index.
+std::error_code llvm::readFunctionSummary(
+    MemoryBufferRef Buffer, LLVMContext &Context,
+    DiagnosticHandlerFunction DiagnosticHandler, StringRef FunctionName,
+    std::unique_ptr<FunctionInfoIndex> Index) {
+  std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
+  FunctionIndexBitcodeReader R(Buf.get(), Context, DiagnosticHandler);
+
+  auto cleanupOnError = [&](std::error_code EC) {
+    R.releaseBuffer();  // Never take ownership on error.
+    return EC;
+  };
+
+  // Lookup the given function name in the FunctionMap, which may
+  // contain a list of function infos in the case of a COMDAT. Walk through
+  // and parse each function summary info at the function summary offset
+  // recorded when parsing the value symbol table.
+  for (const auto &FI : Index->getFunctionInfoList(FunctionName)) {
+    size_t FunctionSummaryOffset = FI->bitcodeIndex();
+    if (std::error_code EC =
+            R.parseFunctionSummary(nullptr, Index.get(), FunctionSummaryOffset))
+      return cleanupOnError(EC);
+  }
+
+  Buf.release();  // The FunctionIndexBitcodeReader owns it now.
+  return std::error_code();
+}
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index f645572..b8a000d3 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -13,6 +13,7 @@
 
 #include "llvm/Bitcode/ReaderWriter.h"
 #include "ValueEnumerator.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Bitcode/BitstreamWriter.h"
 #include "llvm/Bitcode/LLVMBitCodes.h"
@@ -23,6 +24,7 @@
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/UseListOrder.h"
@@ -2187,7 +2189,8 @@
     const ValueSymbolTable &VST, const ValueEnumerator &VE,
     BitstreamWriter &Stream, uint64_t VSTOffsetPlaceholder = 0,
     uint64_t BitcodeStartBit = 0,
-    DenseMap<const Function *, uint64_t> *FunctionIndex = nullptr) {
+    DenseMap<const Function *, std::unique_ptr<FunctionInfo>> *FunctionIndex =
+        nullptr) {
   if (VST.empty()) {
     // WriteValueSymbolTableForwardDecl should have returned early as
     // well. Ensure this handling remains in sync by asserting that
@@ -2282,7 +2285,8 @@
       // Save the word offset of the function (from the start of the
       // actual bitcode written to the stream).
       assert(FunctionIndex->count(F) == 1);
-      uint64_t BitcodeIndex = (*FunctionIndex)[F] - BitcodeStartBit;
+      uint64_t BitcodeIndex =
+          (*FunctionIndex)[F]->bitcodeIndex() - BitcodeStartBit;
       assert((BitcodeIndex & 31) == 0 && "function block not 32-bit aligned");
       NameVals.push_back(BitcodeIndex / 32);
 
@@ -2300,9 +2304,7 @@
         AbbrevToUse = VST_ENTRY_7_ABBREV;
     }
 
-    for (const char *P = Name.getKeyData(),
-         *E = Name.getKeyData()+Name.getKeyLength(); P != E; ++P)
-      NameVals.push_back((unsigned char)*P);
+    for (const auto P : Name.getKey()) NameVals.push_back((unsigned char)P);
 
     // Emit the finished record.
     Stream.EmitRecord(Code, NameVals, AbbrevToUse);
@@ -2311,6 +2313,68 @@
   Stream.ExitBlock();
 }
 
+/// Emit function names and summary offsets for the combined index
+/// used by ThinLTO.
+static void WriteCombinedValueSymbolTable(const FunctionInfoIndex *Index,
+                                          BitstreamWriter &Stream) {
+  Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 4);
+
+  // 8-bit fixed-width VST_COMBINED_FNENTRY function strings.
+  BitCodeAbbrev *Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_COMBINED_FNENTRY));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));  // value id
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));  // funcoffset
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
+  unsigned FnEntry8BitAbbrev = Stream.EmitAbbrev(Abbv);
+
+  // 7-bit fixed width VST_COMBINED_FNENTRY function strings.
+  Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_COMBINED_FNENTRY));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));  // value id
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));  // funcoffset
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
+  unsigned FnEntry7BitAbbrev = Stream.EmitAbbrev(Abbv);
+
+  // 6-bit char6 VST_COMBINED_FNENTRY function strings.
+  Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_COMBINED_FNENTRY));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));  // value id
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));  // funcoffset
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
+  unsigned FnEntry6BitAbbrev = Stream.EmitAbbrev(Abbv);
+
+  // FIXME: We know if the type names can use 7-bit ascii.
+  SmallVector<unsigned, 64> NameVals;
+
+  for (const auto &FII : *Index) {
+    for (const auto &FI : FII.getValue()) {
+      NameVals.push_back(FI->bitcodeIndex());
+
+      StringRef FuncName = FII.first();
+
+      // Figure out the encoding to use for the name.
+      StringEncoding Bits = getStringEncoding(FuncName.data(), FuncName.size());
+
+      // VST_COMBINED_FNENTRY: [funcsumoffset, namechar x N]
+      unsigned AbbrevToUse = FnEntry8BitAbbrev;
+      if (Bits == SE_Char6)
+        AbbrevToUse = FnEntry6BitAbbrev;
+      else if (Bits == SE_Fixed7)
+        AbbrevToUse = FnEntry7BitAbbrev;
+
+      for (const auto P : FuncName) NameVals.push_back((unsigned char)P);
+
+      // Emit the finished record.
+      Stream.EmitRecord(bitc::VST_CODE_COMBINED_FNENTRY, NameVals, AbbrevToUse);
+      NameVals.clear();
+    }
+  }
+  Stream.ExitBlock();
+}
+
 static void WriteUseList(ValueEnumerator &VE, UseListOrder &&Order,
                          BitstreamWriter &Stream) {
   assert(Order.Shuffle.size() >= 2 && "Shuffle too small");
@@ -2345,14 +2409,33 @@
   Stream.ExitBlock();
 }
 
-/// WriteFunction - Emit a function body to the module stream.
-static void WriteFunction(const Function &F, ValueEnumerator &VE,
-                          BitstreamWriter &Stream,
-                          DenseMap<const Function *, uint64_t> &FunctionIndex) {
+/// \brief Save information for the given function into the function index.
+///
+/// At a minimum this saves the bitcode index of the function record that
+/// was just written. However, if we are emitting function summary information,
+/// for example for ThinLTO, then a \a FunctionSummary object is created
+/// to hold the provided summary information.
+static void SaveFunctionInfo(
+    const Function &F,
+    DenseMap<const Function *, std::unique_ptr<FunctionInfo>> &FunctionIndex,
+    unsigned NumInsts, uint64_t BitcodeIndex, bool EmitFunctionSummary) {
+  std::unique_ptr<FunctionSummary> FuncSummary;
+  if (EmitFunctionSummary) {
+    FuncSummary = llvm::make_unique<FunctionSummary>(NumInsts);
+    FuncSummary->setLocalFunction(F.hasLocalLinkage());
+  }
+  FunctionIndex[&F] =
+      llvm::make_unique<FunctionInfo>(BitcodeIndex, std::move(FuncSummary));
+}
+
+/// Emit a function body to the module stream.
+static void WriteFunction(
+    const Function &F, ValueEnumerator &VE, BitstreamWriter &Stream,
+    DenseMap<const Function *, std::unique_ptr<FunctionInfo>> &FunctionIndex,
+    bool EmitFunctionSummary) {
   // Save the bitcode index of the start of this function block for recording
   // in the VST.
   uint64_t BitcodeIndex = Stream.GetCurrentBitNo();
-  FunctionIndex[&F] = BitcodeIndex;
 
   Stream.EnterSubblock(bitc::FUNCTION_BLOCK_ID, 4);
   VE.incorporateFunction(F);
@@ -2379,6 +2462,7 @@
   bool NeedsMetadataAttachment = F.hasMetadata();
 
   DILocation *LastDL = nullptr;
+  unsigned NumInsts = 0;
 
   // Finally, emit all the instructions, in order.
   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
@@ -2386,6 +2470,8 @@
          I != E; ++I) {
       WriteInstruction(*I, InstID, VE, Stream, Vals);
 
+      if (!isa<DbgInfoIntrinsic>(I)) ++NumInsts;
+
       if (!I->getType()->isVoidTy())
         ++InstID;
 
@@ -2422,6 +2508,9 @@
     WriteUseListBlock(&F, VE, Stream);
   VE.purgeFunction();
   Stream.ExitBlock();
+
+  SaveFunctionInfo(F, FunctionIndex, NumInsts, BitcodeIndex,
+                   EmitFunctionSummary);
 }
 
 // Emit blockinfo, which defines the standard abbreviations etc.
@@ -2599,10 +2688,155 @@
   Stream.ExitBlock();
 }
 
+/// Write the module path strings, currently only used when generating
+/// a combined index file.
+static void WriteModStrings(const FunctionInfoIndex *I,
+                            BitstreamWriter &Stream) {
+  Stream.EnterSubblock(bitc::MODULE_STRTAB_BLOCK_ID, 3);
+
+  // TODO: See which abbrev sizes we actually need to emit
+
+  // 8-bit fixed-width MST_ENTRY strings.
+  BitCodeAbbrev *Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::MST_CODE_ENTRY));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
+  unsigned Abbrev8Bit = Stream.EmitAbbrev(Abbv);
+
+  // 7-bit fixed width MST_ENTRY strings.
+  Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::MST_CODE_ENTRY));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
+  unsigned Abbrev7Bit = Stream.EmitAbbrev(Abbv);
+
+  // 6-bit char6 MST_ENTRY strings.
+  Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::MST_CODE_ENTRY));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
+  unsigned Abbrev6Bit = Stream.EmitAbbrev(Abbv);
+
+  SmallVector<unsigned, 64> NameVals;
+  for (const StringMapEntry<uint64_t> &MPSE : I->modPathStringEntries()) {
+    StringEncoding Bits =
+        getStringEncoding(MPSE.getKey().data(), MPSE.getKey().size());
+    unsigned AbbrevToUse = Abbrev8Bit;
+    if (Bits == SE_Char6)
+      AbbrevToUse = Abbrev6Bit;
+    else if (Bits == SE_Fixed7)
+      AbbrevToUse = Abbrev7Bit;
+
+    NameVals.push_back(MPSE.getValue());
+
+    for (const auto P : MPSE.getKey()) NameVals.push_back((unsigned char)P);
+
+    // Emit the finished record.
+    Stream.EmitRecord(bitc::MST_CODE_ENTRY, NameVals, AbbrevToUse);
+    NameVals.clear();
+  }
+  Stream.ExitBlock();
+}
+
+// Helper to emit a single function summary record.
+static void WritePerModuleFunctionSummaryRecord(
+    SmallVector<unsigned, 64> &NameVals, FunctionSummary *FS, unsigned ValueID,
+    unsigned FSAbbrev, BitstreamWriter &Stream) {
+  assert(FS);
+  NameVals.push_back(ValueID);
+  NameVals.push_back(FS->isLocalFunction());
+  NameVals.push_back(FS->instCount());
+
+  // Emit the finished record.
+  Stream.EmitRecord(bitc::FS_CODE_PERMODULE_ENTRY, NameVals, FSAbbrev);
+  NameVals.clear();
+}
+
+/// Emit the per-module function summary section alongside the rest of
+/// the module's bitcode.
+static void WritePerModuleFunctionSummary(
+    DenseMap<const Function *, std::unique_ptr<FunctionInfo>> &FunctionIndex,
+    const Module *M, const ValueEnumerator &VE, BitstreamWriter &Stream) {
+  Stream.EnterSubblock(bitc::FUNCTION_SUMMARY_BLOCK_ID, 3);
+
+  // Abbrev for FS_CODE_PERMODULE_ENTRY.
+  BitCodeAbbrev *Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::FS_CODE_PERMODULE_ENTRY));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));    // valueid
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // islocal
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));    // instcount
+  unsigned FSAbbrev = Stream.EmitAbbrev(Abbv);
+
+  SmallVector<unsigned, 64> NameVals;
+  for (auto &I : FunctionIndex) {
+    // Skip anonymous functions. We will emit a function summary for
+    // any aliases below.
+    if (!I.first->hasName()) continue;
+
+    WritePerModuleFunctionSummaryRecord(
+        NameVals, I.second->functionSummary(),
+        VE.getValueID(M->getValueSymbolTable().lookup(I.first->getName())),
+        FSAbbrev, Stream);
+  }
+
+  for (const GlobalAlias &A : M->aliases()) {
+    if (!A.getBaseObject()) continue;
+    const Function *F = dyn_cast<Function>(A.getBaseObject());
+    if (!F || F->isDeclaration()) continue;
+
+    assert(FunctionIndex.count(F) == 1);
+    WritePerModuleFunctionSummaryRecord(
+        NameVals, FunctionIndex[F]->functionSummary(),
+        VE.getValueID(M->getValueSymbolTable().lookup(A.getName())), FSAbbrev,
+        Stream);
+  }
+
+  Stream.ExitBlock();
+}
+
+/// Emit the combined function summary section into the combined index
+/// file.
+static void WriteCombinedFunctionSummary(const FunctionInfoIndex *I,
+                                         BitstreamWriter &Stream) {
+  Stream.EnterSubblock(bitc::FUNCTION_SUMMARY_BLOCK_ID, 3);
+
+  // Abbrev for FS_CODE_COMBINED_ENTRY.
+  BitCodeAbbrev *Abbv = new BitCodeAbbrev();
+  Abbv->Add(BitCodeAbbrevOp(bitc::FS_CODE_COMBINED_ENTRY));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));  // modid
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));  // instcount
+  unsigned FSAbbrev = Stream.EmitAbbrev(Abbv);
+
+  SmallVector<unsigned, 64> NameVals;
+  for (const auto &FII : *I) {
+    for (auto &FI : FII.getValue()) {
+      FunctionSummary *FS = FI->functionSummary();
+      assert(FS);
+
+      NameVals.push_back(I->getModuleId(FS->modulePath()));
+      NameVals.push_back(FS->instCount());
+
+      // Record the starting offset of this summary entry for use
+      // in the VST entry. Add the current code size since the
+      // reader will invoke readRecord after the abbrev id read.
+      FI->setBitcodeIndex(Stream.GetCurrentBitNo() + Stream.GetAbbrevIDWidth());
+
+      // Emit the finished record.
+      Stream.EmitRecord(bitc::FS_CODE_COMBINED_ENTRY, NameVals, FSAbbrev);
+      NameVals.clear();
+    }
+  }
+
+  Stream.ExitBlock();
+}
+
 /// WriteModule - Emit the specified module to the bitstream.
 static void WriteModule(const Module *M, BitstreamWriter &Stream,
                         bool ShouldPreserveUseListOrder,
-                        uint64_t BitcodeStartBit) {
+                        uint64_t BitcodeStartBit, bool EmitFunctionSummary) {
   Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
 
   SmallVector<unsigned, 1> Vals;
@@ -2647,10 +2881,15 @@
   WriteOperandBundleTags(M, Stream);
 
   // Emit function bodies.
-  DenseMap<const Function *, uint64_t> FunctionIndex;
+  DenseMap<const Function *, std::unique_ptr<FunctionInfo>> FunctionIndex;
   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F)
     if (!F->isDeclaration())
-      WriteFunction(*F, VE, Stream, FunctionIndex);
+      WriteFunction(*F, VE, Stream, FunctionIndex, EmitFunctionSummary);
+
+  // Need to write after the above call to WriteFunction which populates
+  // the summary information in the index.
+  if (EmitFunctionSummary)
+    WritePerModuleFunctionSummary(FunctionIndex, M, VE, Stream);
 
   WriteValueSymbolTable(M->getValueSymbolTable(), VE, Stream,
                         VSTOffsetPlaceholder, BitcodeStartBit, &FunctionIndex);
@@ -2728,10 +2967,22 @@
     Buffer.push_back(0);
 }
 
+/// Helper to write the header common to all bitcode files.
+static void WriteBitcodeHeader(BitstreamWriter &Stream) {
+  // Emit the file header.
+  Stream.Emit((unsigned)'B', 8);
+  Stream.Emit((unsigned)'C', 8);
+  Stream.Emit(0x0, 4);
+  Stream.Emit(0xC, 4);
+  Stream.Emit(0xE, 4);
+  Stream.Emit(0xD, 4);
+}
+
 /// WriteBitcodeToFile - Write the specified module to the specified output
 /// stream.
 void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out,
-                              bool ShouldPreserveUseListOrder) {
+                              bool ShouldPreserveUseListOrder,
+                              bool EmitFunctionSummary) {
   SmallVector<char, 0> Buffer;
   Buffer.reserve(256*1024);
 
@@ -2751,15 +3002,11 @@
     uint64_t BitcodeStartBit = Stream.GetCurrentBitNo();
 
     // Emit the file header.
-    Stream.Emit((unsigned)'B', 8);
-    Stream.Emit((unsigned)'C', 8);
-    Stream.Emit(0x0, 4);
-    Stream.Emit(0xC, 4);
-    Stream.Emit(0xE, 4);
-    Stream.Emit(0xD, 4);
+    WriteBitcodeHeader(Stream);
 
     // Emit the module.
-    WriteModule(M, Stream, ShouldPreserveUseListOrder, BitcodeStartBit);
+    WriteModule(M, Stream, ShouldPreserveUseListOrder, BitcodeStartBit,
+                EmitFunctionSummary);
   }
 
   if (TT.isOSDarwin())
@@ -2768,3 +3015,38 @@
   // Write the generated bitstream to "Out".
   Out.write((char*)&Buffer.front(), Buffer.size());
 }
+
+// Write the specified function summary index to the given raw output stream,
+// where it will be written in a new bitcode block. This is used when
+// writing the combined index file for ThinLTO.
+void llvm::WriteFunctionSummaryToFile(const FunctionInfoIndex *Index,
+                                      raw_ostream &Out) {
+  SmallVector<char, 0> Buffer;
+  Buffer.reserve(256 * 1024);
+
+  BitstreamWriter Stream(Buffer);
+
+  // Emit the bitcode header.
+  WriteBitcodeHeader(Stream);
+
+  Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
+
+  SmallVector<unsigned, 1> Vals;
+  unsigned CurVersion = 1;
+  Vals.push_back(CurVersion);
+  Stream.EmitRecord(bitc::MODULE_CODE_VERSION, Vals);
+
+  // Write the module paths in the combined index.
+  WriteModStrings(Index, Stream);
+
+  // Write the function summary combined index records.
+  WriteCombinedFunctionSummary(Index, Stream);
+
+  // Need a special VST writer for the combined index (we don't have a
+  // real VST and real values when this is invoked).
+  WriteCombinedValueSymbolTable(Index, Stream);
+
+  Stream.ExitBlock();
+
+  Out.write((char *)&Buffer.front(), Buffer.size());
+}
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriterPass.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriterPass.cpp
index 3165743..24de99a 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriterPass.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriterPass.cpp
@@ -19,7 +19,7 @@
 using namespace llvm;
 
 PreservedAnalyses BitcodeWriterPass::run(Module &M) {
-  WriteBitcodeToFile(&M, OS, ShouldPreserveUseListOrder);
+  WriteBitcodeToFile(&M, OS, ShouldPreserveUseListOrder, EmitFunctionSummary);
   return PreservedAnalyses::all();
 }
 
@@ -27,17 +27,21 @@
   class WriteBitcodePass : public ModulePass {
     raw_ostream &OS; // raw_ostream to print on
     bool ShouldPreserveUseListOrder;
+    bool EmitFunctionSummary;
 
   public:
     static char ID; // Pass identification, replacement for typeid
-    explicit WriteBitcodePass(raw_ostream &o, bool ShouldPreserveUseListOrder)
+    explicit WriteBitcodePass(raw_ostream &o, bool ShouldPreserveUseListOrder,
+                              bool EmitFunctionSummary)
         : ModulePass(ID), OS(o),
-          ShouldPreserveUseListOrder(ShouldPreserveUseListOrder) {}
+          ShouldPreserveUseListOrder(ShouldPreserveUseListOrder),
+          EmitFunctionSummary(EmitFunctionSummary) {}
 
     const char *getPassName() const override { return "Bitcode Writer"; }
 
     bool runOnModule(Module &M) override {
-      WriteBitcodeToFile(&M, OS, ShouldPreserveUseListOrder);
+      WriteBitcodeToFile(&M, OS, ShouldPreserveUseListOrder,
+                         EmitFunctionSummary);
       return false;
     }
   };
@@ -46,6 +50,8 @@
 char WriteBitcodePass::ID = 0;
 
 ModulePass *llvm::createBitcodeWriterPass(raw_ostream &Str,
-                                          bool ShouldPreserveUseListOrder) {
-  return new WriteBitcodePass(Str, ShouldPreserveUseListOrder);
+                                          bool ShouldPreserveUseListOrder,
+                                          bool EmitFunctionSummary) {
+  return new WriteBitcodePass(Str, ShouldPreserveUseListOrder,
+                              EmitFunctionSummary);
 }