MFC r309124:

Upgrade our copies of clang, llvm, lldb, compiler-rt and libc++ to 3.9.0
release, and add lld 3.9.0.  Also completely revamp the build system for
clang, llvm, lldb and their related tools.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Release notes for llvm, clang and lld are available here:
<http://llvm.org/releases/3.9.0/docs/ReleaseNotes.html>
<http://llvm.org/releases/3.9.0/tools/clang/docs/ReleaseNotes.html>
<http://llvm.org/releases/3.9.0/tools/lld/docs/ReleaseNotes.html>

Thanks to Ed Maste, Bryan Drewery, Andrew Turner, Antoine Brodin and Jan
Beich for their help.

Relnotes:	yes

MFC r309147:

Pull in r282174 from upstream llvm trunk (by Krzysztof Parzyszek):

  [PPC] Set SP after loading data from stack frame, if no red zone is
  present

  Follow-up to r280705: Make sure that the SP is only restored after
  all data is loaded from the stack frame, if there is no red zone.

  This completes the fix for
  https://llvm.org/bugs/show_bug.cgi?id=26519.

  Differential Revision: https://reviews.llvm.org/D24466

Reported by:    Mark Millard
PR:             214433

MFC r309149:

Pull in r283060 from upstream llvm trunk (by Hal Finkel):

  [PowerPC] Refactor soft-float support, and enable PPC64 soft float

  This change enables soft-float for PowerPC64, and also makes
  soft-float disable all vector instruction sets for both 32-bit and
  64-bit modes. This latter part is necessary because the PPC backend
  canonicalizes many Altivec vector types to floating-point types, and
  so soft-float breaks scalarization support for many operations. Both
  for embedded targets and for operating-system kernels desiring
  soft-float support, it seems reasonable that disabling hardware
  floating-point also disables vector instructions (embedded targets
  without hardware floating point support are unlikely to have Altivec,
  etc. and operating system kernels desiring not to use floating-point
  registers to lower syscall cost are unlikely to want to use vector
  registers either). If someone needs this to work, we'll need to
  change the fact that we promote many Altivec operations to act on
  v4f32. To make it possible to disable Altivec when soft-float is
  enabled, hardware floating-point support needs to be expressed as a
  positive feature, like the others, and not a negative feature,
  because target features cannot have dependencies on the disabling of
  some other feature. So +soft-float has now become -hard-float.

  Fixes PR26970.

Pull in r283061 from upstream clang trunk (by Hal Finkel):

  [PowerPC] Enable soft-float for PPC64, and +soft-float -> -hard-float

  Enable soft-float support on PPC64, as the backend now supports it.
  Also, the backend now uses -hard-float instead of +soft-float, so set
  the target features accordingly.

  Fixes PR26970.

Reported by:	Mark Millard
PR:		214433

MFC r309212:

Add a few missed clang 3.9.0 files to OptionalObsoleteFiles.

MFC r309262:

Fix packaging for clang, lldb and lld 3.9.0

During the upgrade of clang/llvm etc to 3.9.0 in r309124, the PACKAGE
directive in the usr.bin/clang/*.mk files got dropped accidentally.

Restore it, with a few minor changes and additions:
* Correct license in clang.ucl to NCSA
* Add PACKAGE=clang for clang and most of the "ll" tools
* Put lldb in its own package
* Put lld in its own package

Reviewed by:	gjb, jmallett
Differential Revision: https://reviews.freebsd.org/D8666

MFC r309656:

During the bootstrap phase, when building the minimal llvm library on
PowerPC, add lib/Support/Atomic.cpp.  This is needed because upstream
llvm revision r271821 disabled the use of std::call_once, which causes
some fallback functions from Atomic.cpp to be used instead.

Reported by:	Mark Millard
PR:		214902

MFC r309835:

Tentatively apply https://reviews.llvm.org/D18730 to work around gcc PR
70528 (bogus error: constructor required before non-static data member).
This should fix buildworld with the external gcc package.

Reported by:	https://jenkins.freebsd.org/job/FreeBSD_HEAD_amd64_gcc/

MFC r310194:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
3.9.1 release.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Release notes for llvm, clang and lld will be available here:
<http://releases.llvm.org/3.9.1/docs/ReleaseNotes.html>
<http://releases.llvm.org/3.9.1/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/3.9.1/tools/lld/docs/ReleaseNotes.html>

Relnotes:	yes

1 files changed, 835 insertions, 0 deletions

diff --git a/contrib/llvm/lib/LTO/ThinLTOCodeGenerator.cpp b/contrib/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
new file mode 100644
index 0000000..bfb0980
--- /dev/null
+++ b/contrib/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -0,0 +1,835 @@
+//===-ThinLTOCodeGenerator.cpp - LLVM Link Time Optimizer -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Thin Link Time Optimization library. This library is
+// intended to be used by linker to optimize code at link time.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/legacy/ThinLTOCodeGenerator.h"
+
+#ifdef HAVE_LLVM_REVISION
+#include "LLVMLTORevision.h"
+#endif
+
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Analysis/ModuleSummaryAnalysis.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/Bitcode/BitcodeWriterPass.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/ExecutionEngine/ObjectMemoryBuffer.h"
+#include "llvm/IR/DiagnosticPrinter.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/Mangler.h"
+#include "llvm/IRReader/IRReader.h"
+#include "llvm/LTO/LTO.h"
+#include "llvm/Linker/Linker.h"
+#include "llvm/MC/SubtargetFeature.h"
+#include "llvm/Object/IRObjectFile.h"
+#include "llvm/Object/ModuleSummaryIndexObjectFile.h"
+#include "llvm/Support/CachePruning.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/SHA1.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/ThreadPool.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/IPO/FunctionImport.h"
+#include "llvm/Transforms/IPO/Internalize.h"
+#include "llvm/Transforms/IPO/PassManagerBuilder.h"
+#include "llvm/Transforms/ObjCARC.h"
+#include "llvm/Transforms/Utils/FunctionImportUtils.h"
+
+#include <numeric>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "thinlto"
+
+namespace llvm {
+// Flags -discard-value-names, defined in LTOCodeGenerator.cpp
+extern cl::opt<bool> LTODiscardValueNames;
+}
+
+namespace {
+
+static cl::opt<int> ThreadCount("threads",
+                                cl::init(std::thread::hardware_concurrency()));
+
+static void diagnosticHandler(const DiagnosticInfo &DI) {
+  DiagnosticPrinterRawOStream DP(errs());
+  DI.print(DP);
+  errs() << '\n';
+}
+
+// Simple helper to save temporary files for debug.
+static void saveTempBitcode(const Module &TheModule, StringRef TempDir,
+                            unsigned count, StringRef Suffix) {
+  if (TempDir.empty())
+    return;
+  // User asked to save temps, let dump the bitcode file after import.
+  auto SaveTempPath = TempDir + llvm::utostr(count) + Suffix;
+  std::error_code EC;
+  raw_fd_ostream OS(SaveTempPath.str(), EC, sys::fs::F_None);
+  if (EC)
+    report_fatal_error(Twine("Failed to open ") + SaveTempPath +
+                       " to save optimized bitcode\n");
+  WriteBitcodeToFile(&TheModule, OS, /* ShouldPreserveUseListOrder */ true);
+}
+
+static const GlobalValueSummary *
+getFirstDefinitionForLinker(const GlobalValueSummaryList &GVSummaryList) {
+  // If there is any strong definition anywhere, get it.
+  auto StrongDefForLinker = llvm::find_if(
+      GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) {
+        auto Linkage = Summary->linkage();
+        return !GlobalValue::isAvailableExternallyLinkage(Linkage) &&
+               !GlobalValue::isWeakForLinker(Linkage);
+      });
+  if (StrongDefForLinker != GVSummaryList.end())
+    return StrongDefForLinker->get();
+  // Get the first *linker visible* definition for this global in the summary
+  // list.
+  auto FirstDefForLinker = llvm::find_if(
+      GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) {
+        auto Linkage = Summary->linkage();
+        return !GlobalValue::isAvailableExternallyLinkage(Linkage);
+      });
+  // Extern templates can be emitted as available_externally.
+  if (FirstDefForLinker == GVSummaryList.end())
+    return nullptr;
+  return FirstDefForLinker->get();
+}
+
+// Populate map of GUID to the prevailing copy for any multiply defined
+// symbols. Currently assume first copy is prevailing, or any strong
+// definition. Can be refined with Linker information in the future.
+static void computePrevailingCopies(
+    const ModuleSummaryIndex &Index,
+    DenseMap<GlobalValue::GUID, const GlobalValueSummary *> &PrevailingCopy) {
+  auto HasMultipleCopies = [&](const GlobalValueSummaryList &GVSummaryList) {
+    return GVSummaryList.size() > 1;
+  };
+
+  for (auto &I : Index) {
+    if (HasMultipleCopies(I.second))
+      PrevailingCopy[I.first] = getFirstDefinitionForLinker(I.second);
+  }
+}
+
+static StringMap<MemoryBufferRef>
+generateModuleMap(const std::vector<MemoryBufferRef> &Modules) {
+  StringMap<MemoryBufferRef> ModuleMap;
+  for (auto &ModuleBuffer : Modules) {
+    assert(ModuleMap.find(ModuleBuffer.getBufferIdentifier()) ==
+               ModuleMap.end() &&
+           "Expect unique Buffer Identifier");
+    ModuleMap[ModuleBuffer.getBufferIdentifier()] = ModuleBuffer;
+  }
+  return ModuleMap;
+}
+
+static void promoteModule(Module &TheModule, const ModuleSummaryIndex &Index) {
+  if (renameModuleForThinLTO(TheModule, Index))
+    report_fatal_error("renameModuleForThinLTO failed");
+}
+
+static void
+crossImportIntoModule(Module &TheModule, const ModuleSummaryIndex &Index,
+                      StringMap<MemoryBufferRef> &ModuleMap,
+                      const FunctionImporter::ImportMapTy &ImportList) {
+  ModuleLoader Loader(TheModule.getContext(), ModuleMap);
+  FunctionImporter Importer(Index, Loader);
+  Importer.importFunctions(TheModule, ImportList);
+}
+
+static void optimizeModule(Module &TheModule, TargetMachine &TM) {
+  // Populate the PassManager
+  PassManagerBuilder PMB;
+  PMB.LibraryInfo = new TargetLibraryInfoImpl(TM.getTargetTriple());
+  PMB.Inliner = createFunctionInliningPass();
+  // FIXME: should get it from the bitcode?
+  PMB.OptLevel = 3;
+  PMB.LoopVectorize = true;
+  PMB.SLPVectorize = true;
+  PMB.VerifyInput = true;
+  PMB.VerifyOutput = false;
+
+  legacy::PassManager PM;
+
+  // Add the TTI (required to inform the vectorizer about register size for
+  // instance)
+  PM.add(createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis()));
+
+  // Add optimizations
+  PMB.populateThinLTOPassManager(PM);
+
+  PM.run(TheModule);
+}
+
+// Convert the PreservedSymbols map from "Name" based to "GUID" based.
+static DenseSet<GlobalValue::GUID>
+computeGUIDPreservedSymbols(const StringSet<> &PreservedSymbols,
+                            const Triple &TheTriple) {
+  DenseSet<GlobalValue::GUID> GUIDPreservedSymbols(PreservedSymbols.size());
+  for (auto &Entry : PreservedSymbols) {
+    StringRef Name = Entry.first();
+    if (TheTriple.isOSBinFormatMachO() && Name.size() > 0 && Name[0] == '_')
+      Name = Name.drop_front();
+    GUIDPreservedSymbols.insert(GlobalValue::getGUID(Name));
+  }
+  return GUIDPreservedSymbols;
+}
+
+std::unique_ptr<MemoryBuffer> codegenModule(Module &TheModule,
+                                            TargetMachine &TM) {
+  SmallVector<char, 128> OutputBuffer;
+
+  // CodeGen
+  {
+    raw_svector_ostream OS(OutputBuffer);
+    legacy::PassManager PM;
+
+    // If the bitcode files contain ARC code and were compiled with optimization,
+    // the ObjCARCContractPass must be run, so do it unconditionally here.
+    PM.add(createObjCARCContractPass());
+
+    // Setup the codegen now.
+    if (TM.addPassesToEmitFile(PM, OS, TargetMachine::CGFT_ObjectFile,
+                               /* DisableVerify */ true))
+      report_fatal_error("Failed to setup codegen");
+
+    // Run codegen now. resulting binary is in OutputBuffer.
+    PM.run(TheModule);
+  }
+  return make_unique<ObjectMemoryBuffer>(std::move(OutputBuffer));
+}
+
+/// Manage caching for a single Module.
+class ModuleCacheEntry {
+  SmallString<128> EntryPath;
+
+public:
+  // Create a cache entry. This compute a unique hash for the Module considering
+  // the current list of export/import, and offer an interface to query to
+  // access the content in the cache.
+  ModuleCacheEntry(
+      StringRef CachePath, const ModuleSummaryIndex &Index, StringRef ModuleID,
+      const FunctionImporter::ImportMapTy &ImportList,
+      const FunctionImporter::ExportSetTy &ExportList,
+      const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
+      const GVSummaryMapTy &DefinedFunctions,
+      const DenseSet<GlobalValue::GUID> &PreservedSymbols) {
+    if (CachePath.empty())
+      return;
+
+    // Compute the unique hash for this entry
+    // This is based on the current compiler version, the module itself, the
+    // export list, the hash for every single module in the import list, the
+    // list of ResolvedODR for the module, and the list of preserved symbols.
+
+    SHA1 Hasher;
+
+    // Start with the compiler revision
+    Hasher.update(LLVM_VERSION_STRING);
+#ifdef HAVE_LLVM_REVISION
+    Hasher.update(LLVM_REVISION);
+#endif
+
+    // Include the hash for the current module
+    auto ModHash = Index.getModuleHash(ModuleID);
+    Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));
+    for (auto F : ExportList)
+      // The export list can impact the internalization, be conservative here
+      Hasher.update(ArrayRef<uint8_t>((uint8_t *)&F, sizeof(F)));
+
+    // Include the hash for every module we import functions from
+    for (auto &Entry : ImportList) {
+      auto ModHash = Index.getModuleHash(Entry.first());
+      Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));
+    }
+
+    // Include the hash for the resolved ODR.
+    for (auto &Entry : ResolvedODR) {
+      Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&Entry.first,
+                                      sizeof(GlobalValue::GUID)));
+      Hasher.update(ArrayRef<uint8_t>((const uint8_t *)&Entry.second,
+                                      sizeof(GlobalValue::LinkageTypes)));
+    }
+
+    // Include the hash for the preserved symbols.
+    for (auto &Entry : PreservedSymbols) {
+      if (DefinedFunctions.count(Entry))
+        Hasher.update(
+            ArrayRef<uint8_t>((const uint8_t *)&Entry, sizeof(GlobalValue::GUID)));
+    }
+
+    sys::path::append(EntryPath, CachePath, toHex(Hasher.result()));
+  }
+
+  // Access the path to this entry in the cache.
+  StringRef getEntryPath() { return EntryPath; }
+
+  // Try loading the buffer for this cache entry.
+  ErrorOr<std::unique_ptr<MemoryBuffer>> tryLoadingBuffer() {
+    if (EntryPath.empty())
+      return std::error_code();
+    return MemoryBuffer::getFile(EntryPath);
+  }
+
+  // Cache the Produced object file
+  std::unique_ptr<MemoryBuffer>
+  write(std::unique_ptr<MemoryBuffer> OutputBuffer) {
+    if (EntryPath.empty())
+      return OutputBuffer;
+
+    // Write to a temporary to avoid race condition
+    SmallString<128> TempFilename;
+    int TempFD;
+    std::error_code EC =
+        sys::fs::createTemporaryFile("Thin", "tmp.o", TempFD, TempFilename);
+    if (EC) {
+      errs() << "Error: " << EC.message() << "\n";
+      report_fatal_error("ThinLTO: Can't get a temporary file");
+    }
+    {
+      raw_fd_ostream OS(TempFD, /* ShouldClose */ true);
+      OS << OutputBuffer->getBuffer();
+    }
+    // Rename to final destination (hopefully race condition won't matter here)
+    EC = sys::fs::rename(TempFilename, EntryPath);
+    if (EC) {
+      sys::fs::remove(TempFilename);
+      raw_fd_ostream OS(EntryPath, EC, sys::fs::F_None);
+      if (EC)
+        report_fatal_error(Twine("Failed to open ") + EntryPath +
+                           " to save cached entry\n");
+      OS << OutputBuffer->getBuffer();
+    }
+    auto ReloadedBufferOrErr = MemoryBuffer::getFile(EntryPath);
+    if (auto EC = ReloadedBufferOrErr.getError()) {
+      // FIXME diagnose
+      errs() << "error: can't reload cached file '" << EntryPath
+             << "': " << EC.message() << "\n";
+      return OutputBuffer;
+    }
+    return std::move(*ReloadedBufferOrErr);
+  }
+};
+
+static std::unique_ptr<MemoryBuffer>
+ProcessThinLTOModule(Module &TheModule, ModuleSummaryIndex &Index,
+                     StringMap<MemoryBufferRef> &ModuleMap, TargetMachine &TM,
+                     const FunctionImporter::ImportMapTy &ImportList,
+                     const FunctionImporter::ExportSetTy &ExportList,
+                     const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols,
+                     const GVSummaryMapTy &DefinedGlobals,
+                     const ThinLTOCodeGenerator::CachingOptions &CacheOptions,
+                     bool DisableCodeGen, StringRef SaveTempsDir,
+                     unsigned count) {
+
+  // "Benchmark"-like optimization: single-source case
+  bool SingleModule = (ModuleMap.size() == 1);
+
+  if (!SingleModule) {
+    promoteModule(TheModule, Index);
+
+    // Apply summary-based LinkOnce/Weak resolution decisions.
+    thinLTOResolveWeakForLinkerModule(TheModule, DefinedGlobals);
+
+    // Save temps: after promotion.
+    saveTempBitcode(TheModule, SaveTempsDir, count, ".1.promoted.bc");
+  }
+
+  // Be friendly and don't nuke totally the module when the client didn't
+  // supply anything to preserve.
+  if (!ExportList.empty() || !GUIDPreservedSymbols.empty()) {
+    // Apply summary-based internalization decisions.
+    thinLTOInternalizeModule(TheModule, DefinedGlobals);
+  }
+
+  // Save internalized bitcode
+  saveTempBitcode(TheModule, SaveTempsDir, count, ".2.internalized.bc");
+
+  if (!SingleModule) {
+    crossImportIntoModule(TheModule, Index, ModuleMap, ImportList);
+
+    // Save temps: after cross-module import.
+    saveTempBitcode(TheModule, SaveTempsDir, count, ".3.imported.bc");
+  }
+
+  optimizeModule(TheModule, TM);
+
+  saveTempBitcode(TheModule, SaveTempsDir, count, ".4.opt.bc");
+
+  if (DisableCodeGen) {
+    // Configured to stop before CodeGen, serialize the bitcode and return.
+    SmallVector<char, 128> OutputBuffer;
+    {
+      raw_svector_ostream OS(OutputBuffer);
+      ModuleSummaryIndexBuilder IndexBuilder(&TheModule);
+      WriteBitcodeToFile(&TheModule, OS, true, &IndexBuilder.getIndex());
+    }
+    return make_unique<ObjectMemoryBuffer>(std::move(OutputBuffer));
+  }
+
+  return codegenModule(TheModule, TM);
+}
+
+/// Resolve LinkOnce/Weak symbols. Record resolutions in the \p ResolvedODR map
+/// for caching, and in the \p Index for application during the ThinLTO
+/// backends. This is needed for correctness for exported symbols (ensure
+/// at least one copy kept) and a compile-time optimization (to drop duplicate
+/// copies when possible).
+static void resolveWeakForLinkerInIndex(
+    ModuleSummaryIndex &Index,
+    StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>>
+        &ResolvedODR) {
+
+  DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy;
+  computePrevailingCopies(Index, PrevailingCopy);
+
+  auto isPrevailing = [&](GlobalValue::GUID GUID, const GlobalValueSummary *S) {
+    const auto &Prevailing = PrevailingCopy.find(GUID);
+    // Not in map means that there was only one copy, which must be prevailing.
+    if (Prevailing == PrevailingCopy.end())
+      return true;
+    return Prevailing->second == S;
+  };
+
+  auto recordNewLinkage = [&](StringRef ModuleIdentifier,
+                              GlobalValue::GUID GUID,
+                              GlobalValue::LinkageTypes NewLinkage) {
+    ResolvedODR[ModuleIdentifier][GUID] = NewLinkage;
+  };
+
+  thinLTOResolveWeakForLinkerInIndex(Index, isPrevailing, recordNewLinkage);
+}
+
+// Initialize the TargetMachine builder for a given Triple
+static void initTMBuilder(TargetMachineBuilder &TMBuilder,
+                          const Triple &TheTriple) {
+  // Set a default CPU for Darwin triples (copied from LTOCodeGenerator).
+  // FIXME this looks pretty terrible...
+  if (TMBuilder.MCpu.empty() && TheTriple.isOSDarwin()) {
+    if (TheTriple.getArch() == llvm::Triple::x86_64)
+      TMBuilder.MCpu = "core2";
+    else if (TheTriple.getArch() == llvm::Triple::x86)
+      TMBuilder.MCpu = "yonah";
+    else if (TheTriple.getArch() == llvm::Triple::aarch64)
+      TMBuilder.MCpu = "cyclone";
+  }
+  TMBuilder.TheTriple = std::move(TheTriple);
+}
+
+} // end anonymous namespace
+
+void ThinLTOCodeGenerator::addModule(StringRef Identifier, StringRef Data) {
+  MemoryBufferRef Buffer(Data, Identifier);
+  if (Modules.empty()) {
+    // First module added, so initialize the triple and some options
+    LLVMContext Context;
+    Triple TheTriple(getBitcodeTargetTriple(Buffer, Context));
+    initTMBuilder(TMBuilder, Triple(TheTriple));
+  }
+#ifndef NDEBUG
+  else {
+    LLVMContext Context;
+    assert(TMBuilder.TheTriple.str() ==
+               getBitcodeTargetTriple(Buffer, Context) &&
+           "ThinLTO modules with different triple not supported");
+  }
+#endif
+  Modules.push_back(Buffer);
+}
+
+void ThinLTOCodeGenerator::preserveSymbol(StringRef Name) {
+  PreservedSymbols.insert(Name);
+}
+
+void ThinLTOCodeGenerator::crossReferenceSymbol(StringRef Name) {
+  // FIXME: At the moment, we don't take advantage of this extra information,
+  // we're conservatively considering cross-references as preserved.
+  //  CrossReferencedSymbols.insert(Name);
+  PreservedSymbols.insert(Name);
+}
+
+// TargetMachine factory
+std::unique_ptr<TargetMachine> TargetMachineBuilder::create() const {
+  std::string ErrMsg;
+  const Target *TheTarget =
+      TargetRegistry::lookupTarget(TheTriple.str(), ErrMsg);
+  if (!TheTarget) {
+    report_fatal_error("Can't load target for this Triple: " + ErrMsg);
+  }
+
+  // Use MAttr as the default set of features.
+  SubtargetFeatures Features(MAttr);
+  Features.getDefaultSubtargetFeatures(TheTriple);
+  std::string FeatureStr = Features.getString();
+  return std::unique_ptr<TargetMachine>(TheTarget->createTargetMachine(
+      TheTriple.str(), MCpu, FeatureStr, Options, RelocModel,
+      CodeModel::Default, CGOptLevel));
+}
+
+/**
+ * Produce the combined summary index from all the bitcode files:
+ * "thin-link".
+ */
+std::unique_ptr<ModuleSummaryIndex> ThinLTOCodeGenerator::linkCombinedIndex() {
+  std::unique_ptr<ModuleSummaryIndex> CombinedIndex;
+  uint64_t NextModuleId = 0;
+  for (auto &ModuleBuffer : Modules) {
+    ErrorOr<std::unique_ptr<object::ModuleSummaryIndexObjectFile>> ObjOrErr =
+        object::ModuleSummaryIndexObjectFile::create(ModuleBuffer,
+                                                     diagnosticHandler);
+    if (std::error_code EC = ObjOrErr.getError()) {
+      // FIXME diagnose
+      errs() << "error: can't create ModuleSummaryIndexObjectFile for buffer: "
+             << EC.message() << "\n";
+      return nullptr;
+    }
+    auto Index = (*ObjOrErr)->takeIndex();
+    if (CombinedIndex) {
+      CombinedIndex->mergeFrom(std::move(Index), ++NextModuleId);
+    } else {
+      CombinedIndex = std::move(Index);
+    }
+  }
+  return CombinedIndex;
+}
+
+/**
+ * Perform promotion and renaming of exported internal functions.
+ * Index is updated to reflect linkage changes from weak resolution.
+ */
+void ThinLTOCodeGenerator::promote(Module &TheModule,
+                                   ModuleSummaryIndex &Index) {
+  auto ModuleCount = Index.modulePaths().size();
+  auto ModuleIdentifier = TheModule.getModuleIdentifier();
+  // Collect for each module the list of function it defines (GUID -> Summary).
+  StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries;
+  Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
+
+  // Generate import/export list
+  StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
+  StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
+  ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
+                           ExportLists);
+
+  // Resolve LinkOnce/Weak symbols.
+  StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
+  resolveWeakForLinkerInIndex(Index, ResolvedODR);
+
+  thinLTOResolveWeakForLinkerModule(
+      TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier]);
+
+  promoteModule(TheModule, Index);
+}
+
+/**
+ * Perform cross-module importing for the module identified by ModuleIdentifier.
+ */
+void ThinLTOCodeGenerator::crossModuleImport(Module &TheModule,
+                                             ModuleSummaryIndex &Index) {
+  auto ModuleMap = generateModuleMap(Modules);
+  auto ModuleCount = Index.modulePaths().size();
+
+  // Collect for each module the list of function it defines (GUID -> Summary).
+  StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
+  Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
+
+  // Generate import/export list
+  StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
+  StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
+  ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
+                           ExportLists);
+  auto &ImportList = ImportLists[TheModule.getModuleIdentifier()];
+
+  crossImportIntoModule(TheModule, Index, ModuleMap, ImportList);
+}
+
+/**
+ * Compute the list of summaries needed for importing into module.
+ */
+void ThinLTOCodeGenerator::gatherImportedSummariesForModule(
+    StringRef ModulePath, ModuleSummaryIndex &Index,
+    std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex) {
+  auto ModuleCount = Index.modulePaths().size();
+
+  // Collect for each module the list of function it defines (GUID -> Summary).
+  StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
+  Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
+
+  // Generate import/export list
+  StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
+  StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
+  ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
+                           ExportLists);
+
+  llvm::gatherImportedSummariesForModule(ModulePath, ModuleToDefinedGVSummaries,
+                                         ImportLists,
+                                         ModuleToSummariesForIndex);
+}
+
+/**
+ * Emit the list of files needed for importing into module.
+ */
+void ThinLTOCodeGenerator::emitImports(StringRef ModulePath,
+                                       StringRef OutputName,
+                                       ModuleSummaryIndex &Index) {
+  auto ModuleCount = Index.modulePaths().size();
+
+  // Collect for each module the list of function it defines (GUID -> Summary).
+  StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
+  Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
+
+  // Generate import/export list
+  StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
+  StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
+  ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
+                           ExportLists);
+
+  std::error_code EC;
+  if ((EC = EmitImportsFiles(ModulePath, OutputName, ImportLists)))
+    report_fatal_error(Twine("Failed to open ") + OutputName +
+                       " to save imports lists\n");
+}
+
+/**
+ * Perform internalization. Index is updated to reflect linkage changes.
+ */
+void ThinLTOCodeGenerator::internalize(Module &TheModule,
+                                       ModuleSummaryIndex &Index) {
+  initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple()));
+  auto ModuleCount = Index.modulePaths().size();
+  auto ModuleIdentifier = TheModule.getModuleIdentifier();
+
+  // Convert the preserved symbols set from string to GUID
+  auto GUIDPreservedSymbols =
+      computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
+
+  // Collect for each module the list of function it defines (GUID -> Summary).
+  StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
+  Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
+
+  // Generate import/export list
+  StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
+  StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
+  ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
+                           ExportLists);
+  auto &ExportList = ExportLists[ModuleIdentifier];
+
+  // Be friendly and don't nuke totally the module when the client didn't
+  // supply anything to preserve.
+  if (ExportList.empty() && GUIDPreservedSymbols.empty())
+    return;
+
+  // Internalization
+  auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
+    const auto &ExportList = ExportLists.find(ModuleIdentifier);
+    return (ExportList != ExportLists.end() &&
+            ExportList->second.count(GUID)) ||
+           GUIDPreservedSymbols.count(GUID);
+  };
+  thinLTOInternalizeAndPromoteInIndex(Index, isExported);
+  thinLTOInternalizeModule(TheModule,
+                           ModuleToDefinedGVSummaries[ModuleIdentifier]);
+}
+
+/**
+ * Perform post-importing ThinLTO optimizations.
+ */
+void ThinLTOCodeGenerator::optimize(Module &TheModule) {
+  initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple()));
+
+  // Optimize now
+  optimizeModule(TheModule, *TMBuilder.create());
+}
+
+/**
+ * Perform ThinLTO CodeGen.
+ */
+std::unique_ptr<MemoryBuffer> ThinLTOCodeGenerator::codegen(Module &TheModule) {
+  initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple()));
+  return codegenModule(TheModule, *TMBuilder.create());
+}
+
+// Main entry point for the ThinLTO processing
+void ThinLTOCodeGenerator::run() {
+  if (CodeGenOnly) {
+    // Perform only parallel codegen and return.
+    ThreadPool Pool;
+    assert(ProducedBinaries.empty() && "The generator should not be reused");
+    ProducedBinaries.resize(Modules.size());
+    int count = 0;
+    for (auto &ModuleBuffer : Modules) {
+      Pool.async([&](int count) {
+        LLVMContext Context;
+        Context.setDiscardValueNames(LTODiscardValueNames);
+
+        // Parse module now
+        auto TheModule = loadModuleFromBuffer(ModuleBuffer, Context, false);
+
+        // CodeGen
+        ProducedBinaries[count] = codegen(*TheModule);
+      }, count++);
+    }
+
+    return;
+  }
+
+  // Sequential linking phase
+  auto Index = linkCombinedIndex();
+
+  // Save temps: index.
+  if (!SaveTempsDir.empty()) {
+    auto SaveTempPath = SaveTempsDir + "index.bc";
+    std::error_code EC;
+    raw_fd_ostream OS(SaveTempPath, EC, sys::fs::F_None);
+    if (EC)
+      report_fatal_error(Twine("Failed to open ") + SaveTempPath +
+                         " to save optimized bitcode\n");
+    WriteIndexToFile(*Index, OS);
+  }
+
+  // Prepare the resulting object vector
+  assert(ProducedBinaries.empty() && "The generator should not be reused");
+  ProducedBinaries.resize(Modules.size());
+
+  // Prepare the module map.
+  auto ModuleMap = generateModuleMap(Modules);
+  auto ModuleCount = Modules.size();
+
+  // Collect for each module the list of function it defines (GUID -> Summary).
+  StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
+  Index->collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
+
+  // Collect the import/export lists for all modules from the call-graph in the
+  // combined index.
+  StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
+  StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
+  ComputeCrossModuleImport(*Index, ModuleToDefinedGVSummaries, ImportLists,
+                           ExportLists);
+
+  // Convert the preserved symbols set from string to GUID, this is needed for
+  // computing the caching hash and the internalization.
+  auto GUIDPreservedSymbols =
+      computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
+
+  // We use a std::map here to be able to have a defined ordering when
+  // producing a hash for the cache entry.
+  // FIXME: we should be able to compute the caching hash for the entry based
+  // on the index, and nuke this map.
+  StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
+
+  // Resolve LinkOnce/Weak symbols, this has to be computed early because it
+  // impacts the caching.
+  resolveWeakForLinkerInIndex(*Index, ResolvedODR);
+
+  auto isExported = [&](StringRef ModuleIdentifier, GlobalValue::GUID GUID) {
+    const auto &ExportList = ExportLists.find(ModuleIdentifier);
+    return (ExportList != ExportLists.end() &&
+            ExportList->second.count(GUID)) ||
+           GUIDPreservedSymbols.count(GUID);
+  };
+
+  // Use global summary-based analysis to identify symbols that can be
+  // internalized (because they aren't exported or preserved as per callback).
+  // Changes are made in the index, consumed in the ThinLTO backends.
+  thinLTOInternalizeAndPromoteInIndex(*Index, isExported);
+
+  // Make sure that every module has an entry in the ExportLists and
+  // ResolvedODR maps to enable threaded access to these maps below.
+  for (auto &DefinedGVSummaries : ModuleToDefinedGVSummaries) {
+    ExportLists[DefinedGVSummaries.first()];
+    ResolvedODR[DefinedGVSummaries.first()];
+  }
+
+  // Compute the ordering we will process the inputs: the rough heuristic here
+  // is to sort them per size so that the largest module get schedule as soon as
+  // possible. This is purely a compile-time optimization.
+  std::vector<int> ModulesOrdering;
+  ModulesOrdering.resize(Modules.size());
+  std::iota(ModulesOrdering.begin(), ModulesOrdering.end(), 0);
+  std::sort(ModulesOrdering.begin(), ModulesOrdering.end(),
+            [&](int LeftIndex, int RightIndex) {
+              auto LSize = Modules[LeftIndex].getBufferSize();
+              auto RSize = Modules[RightIndex].getBufferSize();
+              return LSize > RSize;
+            });
+
+  // Parallel optimizer + codegen
+  {
+    ThreadPool Pool(ThreadCount);
+    for (auto IndexCount : ModulesOrdering) {
+      auto &ModuleBuffer = Modules[IndexCount];
+      Pool.async([&](int count) {
+        auto ModuleIdentifier = ModuleBuffer.getBufferIdentifier();
+        auto &ExportList = ExportLists[ModuleIdentifier];
+
+        auto &DefinedFunctions = ModuleToDefinedGVSummaries[ModuleIdentifier];
+
+        // The module may be cached, this helps handling it.
+        ModuleCacheEntry CacheEntry(CacheOptions.Path, *Index, ModuleIdentifier,
+                                    ImportLists[ModuleIdentifier], ExportList,
+                                    ResolvedODR[ModuleIdentifier],
+                                    DefinedFunctions, GUIDPreservedSymbols);
+
+        {
+          auto ErrOrBuffer = CacheEntry.tryLoadingBuffer();
+          DEBUG(dbgs() << "Cache " << (ErrOrBuffer ? "hit" : "miss") << " '"
+                       << CacheEntry.getEntryPath() << "' for buffer " << count
+                       << " " << ModuleIdentifier << "\n");
+
+          if (ErrOrBuffer) {
+            // Cache Hit!
+            ProducedBinaries[count] = std::move(ErrOrBuffer.get());
+            return;
+          }
+        }
+
+        LLVMContext Context;
+        Context.setDiscardValueNames(LTODiscardValueNames);
+        Context.enableDebugTypeODRUniquing();
+
+        // Parse module now
+        auto TheModule = loadModuleFromBuffer(ModuleBuffer, Context, false);
+
+        // Save temps: original file.
+        saveTempBitcode(*TheModule, SaveTempsDir, count, ".0.original.bc");
+
+        auto &ImportList = ImportLists[ModuleIdentifier];
+        // Run the main process now, and generates a binary
+        auto OutputBuffer = ProcessThinLTOModule(
+            *TheModule, *Index, ModuleMap, *TMBuilder.create(), ImportList,
+            ExportList, GUIDPreservedSymbols,
+            ModuleToDefinedGVSummaries[ModuleIdentifier], CacheOptions,
+            DisableCodeGen, SaveTempsDir, count);
+
+        OutputBuffer = CacheEntry.write(std::move(OutputBuffer));
+        ProducedBinaries[count] = std::move(OutputBuffer);
+      }, IndexCount);
+    }
+  }
+
+  CachePruning(CacheOptions.Path)
+      .setPruningInterval(CacheOptions.PruningInterval)
+      .setEntryExpiration(CacheOptions.Expiration)
+      .setMaxSize(CacheOptions.MaxPercentageOfAvailableSpace)
+      .prune();
+
+  // If statistics were requested, print them out now.
+  if (llvm::AreStatisticsEnabled())
+    llvm::PrintStatistics();
+}