Move LTO support library to a component, allowing it to be tested

more reliably across platforms.  Patch by Tom Roeder!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191343 91177308-0d34-0410-b5e6-96231b3b80d8

lib/LTO/CMakeLists.txt

@@ -0,0 +1,4 @@
+add_llvm_library(LLVMLTO
+  LTOModule.cpp
+  LTOCodeGenerator.cpp
+  )

lib/LTO/LLVMBuild.txt

@@ -0,0 +1,22 @@
+;===- ./lib/LTO/LLVMBuild.txt ----------------------------------*- Conf -*--===;
+;
+;                     The LLVM Compiler Infrastructure
+;
+; This file is distributed under the University of Illinois Open Source
+; License. See LICENSE.TXT for details.
+;
+;===------------------------------------------------------------------------===;
+;
+; This is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+;   http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[component_0]
+type = Library
+name = LTO
+parent = Libraries
+required_libraries = Analysis BitReader BitWriter Core IPO Linker MC MCParser Scalar Support Target Vectorize

lib/LTO/LTOCodeGenerator.cpp

@@ -0,0 +1,453 @@
+//===-LTOCodeGenerator.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 Link Time Optimization library. This library is
+// intended to be used by linker to optimize code at link time.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/LTOCodeGenerator.h"
+#include "llvm/LTO/LTOModule.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/Config/config.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Linker.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/SubtargetFeature.h"
+#include "llvm/PassManager.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/FormattedStream.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Signals.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include "llvm/Support/system_error.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/Mangler.h"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/IPO/PassManagerBuilder.h"
+#include "llvm/Transforms/ObjCARC.h"
+using namespace llvm;
+
+static cl::opt<bool>
+DisableOpt("disable-opt", cl::init(false),
+  cl::desc("Do not run any optimization passes"));
+
+static cl::opt<bool>
+DisableInline("disable-inlining", cl::init(false),
+  cl::desc("Do not run the inliner pass"));
+
+static cl::opt<bool>
+DisableGVNLoadPRE("disable-gvn-loadpre", cl::init(false),
+  cl::desc("Do not run the GVN load PRE pass"));
+
+const char* LTOCodeGenerator::getVersionString() {
+#ifdef LLVM_VERSION_INFO
+  return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
+#else
+  return PACKAGE_NAME " version " PACKAGE_VERSION;
+#endif
+}
+
+LTOCodeGenerator::LTOCodeGenerator()
+    : Context(getGlobalContext()), Linker(new Module("ld-temp.o", Context)),
+      TargetMach(NULL), EmitDwarfDebugInfo(false), ScopeRestrictionsDone(false),
+      CodeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC), NativeObjectFile(NULL) {
+  initializeLTOPasses();
+}
+
+LTOCodeGenerator::~LTOCodeGenerator() {
+  delete TargetMach;
+  delete NativeObjectFile;
+  delete Linker.getModule();
+
+  for (std::vector<char *>::iterator I = CodegenOptions.begin(),
+                                     E = CodegenOptions.end();
+       I != E; ++I)
+    free(*I);
+}
+
+// Initialize LTO passes. Please keep this funciton in sync with
+// PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
+// passes are initialized. 
+//
+void LTOCodeGenerator::initializeLTOPasses() {
+  PassRegistry &R = *PassRegistry::getPassRegistry();
+
+  initializeInternalizePassPass(R);
+  initializeIPSCCPPass(R);
+  initializeGlobalOptPass(R);
+  initializeConstantMergePass(R);
+  initializeDAHPass(R);
+  initializeInstCombinerPass(R);
+  initializeSimpleInlinerPass(R);
+  initializePruneEHPass(R);
+  initializeGlobalDCEPass(R);
+  initializeArgPromotionPass(R);
+  initializeJumpThreadingPass(R);
+  initializeSROAPass(R);
+  initializeSROA_DTPass(R);
+  initializeSROA_SSAUpPass(R);
+  initializeFunctionAttrsPass(R);
+  initializeGlobalsModRefPass(R);
+  initializeLICMPass(R);
+  initializeGVNPass(R);
+  initializeMemCpyOptPass(R);
+  initializeDCEPass(R);
+  initializeCFGSimplifyPassPass(R);
+}
+
+bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg) {
+  bool ret = Linker.linkInModule(mod->getLLVVMModule(), &errMsg);
+
+  const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
+  for (int i = 0, e = undefs.size(); i != e; ++i)
+    AsmUndefinedRefs[undefs[i]] = 1;
+
+  return !ret;
+}
+
+void LTOCodeGenerator::setDebugInfo(lto_debug_model debug) {
+  switch (debug) {
+  case LTO_DEBUG_MODEL_NONE:
+    EmitDwarfDebugInfo = false;
+    return;
+
+  case LTO_DEBUG_MODEL_DWARF:
+    EmitDwarfDebugInfo = true;
+    return;
+  }
+  llvm_unreachable("Unknown debug format!");
+}
+
+void LTOCodeGenerator::setCodePICModel(lto_codegen_model model) {
+  switch (model) {
+  case LTO_CODEGEN_PIC_MODEL_STATIC:
+  case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
+  case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
+    CodeModel = model;
+    return;
+  }
+  llvm_unreachable("Unknown PIC model!");
+}
+
+bool LTOCodeGenerator::writeMergedModules(const char *path,
+                                          std::string &errMsg) {
+  if (!determineTarget(errMsg))
+    return false;
+
+  // mark which symbols can not be internalized
+  applyScopeRestrictions();
+
+  // create output file
+  std::string ErrInfo;
+  tool_output_file Out(path, ErrInfo, sys::fs::F_Binary);
+  if (!ErrInfo.empty()) {
+    errMsg = "could not open bitcode file for writing: ";
+    errMsg += path;
+    return false;
+  }
+
+  // write bitcode to it
+  WriteBitcodeToFile(Linker.getModule(), Out.os());
+  Out.os().close();
+
+  if (Out.os().has_error()) {
+    errMsg = "could not write bitcode file: ";
+    errMsg += path;
+    Out.os().clear_error();
+    return false;
+  }
+
+  Out.keep();
+  return true;
+}
+
+bool LTOCodeGenerator::compile_to_file(const char** name, std::string& errMsg) {
+  // make unique temp .o file to put generated object file
+  SmallString<128> Filename;
+  int FD;
+  error_code EC = sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
+  if (EC) {
+    errMsg = EC.message();
+    return false;
+  }
+
+  // generate object file
+  tool_output_file objFile(Filename.c_str(), FD);
+
+  bool genResult = generateObjectFile(objFile.os(), errMsg);
+  objFile.os().close();
+  if (objFile.os().has_error()) {
+    objFile.os().clear_error();
+    sys::fs::remove(Twine(Filename));
+    return false;
+  }
+
+  objFile.keep();
+  if (!genResult) {
+    sys::fs::remove(Twine(Filename));
+    return false;
+  }
+
+  NativeObjectPath = Filename.c_str();
+  *name = NativeObjectPath.c_str();
+  return true;
+}
+
+const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg) {
+  const char *name;
+  if (!compile_to_file(&name, errMsg))
+    return NULL;
+
+  // remove old buffer if compile() called twice
+  delete NativeObjectFile;
+
+  // read .o file into memory buffer
+  OwningPtr<MemoryBuffer> BuffPtr;
+  if (error_code ec = MemoryBuffer::getFile(name, BuffPtr, -1, false)) {
+    errMsg = ec.message();
+    sys::fs::remove(NativeObjectPath);
+    return NULL;
+  }
+  NativeObjectFile = BuffPtr.take();
+
+  // remove temp files
+  sys::fs::remove(NativeObjectPath);
+
+  // return buffer, unless error
+  if (NativeObjectFile == NULL)
+    return NULL;
+  *length = NativeObjectFile->getBufferSize();
+  return NativeObjectFile->getBufferStart();
+}
+
+bool LTOCodeGenerator::determineTarget(std::string &errMsg) {
+  if (TargetMach != NULL)
+    return true;
+
+  // if options were requested, set them
+  if (!CodegenOptions.empty())
+    cl::ParseCommandLineOptions(CodegenOptions.size(),
+                                const_cast<char **>(&CodegenOptions[0]));
+
+  std::string TripleStr = Linker.getModule()->getTargetTriple();
+  if (TripleStr.empty())
+    TripleStr = sys::getDefaultTargetTriple();
+  llvm::Triple Triple(TripleStr);
+
+  // create target machine from info for merged modules
+  const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
+  if (march == NULL)
+    return false;
+
+  // The relocation model is actually a static member of TargetMachine and
+  // needs to be set before the TargetMachine is instantiated.
+  Reloc::Model RelocModel = Reloc::Default;
+  switch (CodeModel) {
+  case LTO_CODEGEN_PIC_MODEL_STATIC:
+    RelocModel = Reloc::Static;
+    break;
+  case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
+    RelocModel = Reloc::PIC_;
+    break;
+  case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
+    RelocModel = Reloc::DynamicNoPIC;
+    break;
+  }
+
+  // construct LTOModule, hand over ownership of module and target
+  SubtargetFeatures Features;
+  Features.getDefaultSubtargetFeatures(Triple);
+  std::string FeatureStr = Features.getString();
+  // Set a default CPU for Darwin triples.
+  if (MCpu.empty() && Triple.isOSDarwin()) {
+    if (Triple.getArch() == llvm::Triple::x86_64)
+      MCpu = "core2";
+    else if (Triple.getArch() == llvm::Triple::x86)
+      MCpu = "yonah";
+  }
+  TargetOptions Options;
+  LTOModule::getTargetOptions(Options);
+  TargetMach = march->createTargetMachine(TripleStr, MCpu, FeatureStr, Options,
+                                          RelocModel, CodeModel::Default,
+                                          CodeGenOpt::Aggressive);
+  return true;
+}
+
+void LTOCodeGenerator::
+applyRestriction(GlobalValue &GV,
+                 std::vector<const char*> &MustPreserveList,
+                 SmallPtrSet<GlobalValue*, 8> &AsmUsed,
+                 Mangler &Mangler) {
+  SmallString<64> Buffer;
+  Mangler.getNameWithPrefix(Buffer, &GV, false);
+
+  if (GV.isDeclaration())
+    return;
+  if (MustPreserveSymbols.count(Buffer))
+    MustPreserveList.push_back(GV.getName().data());
+  if (AsmUndefinedRefs.count(Buffer))
+    AsmUsed.insert(&GV);
+}
+
+static void findUsedValues(GlobalVariable *LLVMUsed,
+                           SmallPtrSet<GlobalValue*, 8> &UsedValues) {
+  if (LLVMUsed == 0) return;
+
+  ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
+  for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
+    if (GlobalValue *GV =
+        dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
+      UsedValues.insert(GV);
+}
+
+void LTOCodeGenerator::applyScopeRestrictions() {
+  if (ScopeRestrictionsDone)
+    return;
+  Module *mergedModule = Linker.getModule();
+
+  // Start off with a verification pass.
+  PassManager passes;
+  passes.add(createVerifierPass());
+
+  // mark which symbols can not be internalized
+  MCContext MContext(TargetMach->getMCAsmInfo(), TargetMach->getRegisterInfo(),
+                     NULL);
+  Mangler Mangler(MContext, TargetMach);
+  std::vector<const char*> MustPreserveList;
+  SmallPtrSet<GlobalValue*, 8> AsmUsed;
+
+  for (Module::iterator f = mergedModule->begin(),
+         e = mergedModule->end(); f != e; ++f)
+    applyRestriction(*f, MustPreserveList, AsmUsed, Mangler);
+  for (Module::global_iterator v = mergedModule->global_begin(),
+         e = mergedModule->global_end(); v !=  e; ++v)
+    applyRestriction(*v, MustPreserveList, AsmUsed, Mangler);
+  for (Module::alias_iterator a = mergedModule->alias_begin(),
+         e = mergedModule->alias_end(); a != e; ++a)
+    applyRestriction(*a, MustPreserveList, AsmUsed, Mangler);
+
+  GlobalVariable *LLVMCompilerUsed =
+    mergedModule->getGlobalVariable("llvm.compiler.used");
+  findUsedValues(LLVMCompilerUsed, AsmUsed);
+  if (LLVMCompilerUsed)
+    LLVMCompilerUsed->eraseFromParent();
+
+  if (!AsmUsed.empty()) {
+    llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
+    std::vector<Constant*> asmUsed2;
+    for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = AsmUsed.begin(),
+           e = AsmUsed.end(); i !=e; ++i) {
+      GlobalValue *GV = *i;
+      Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
+      asmUsed2.push_back(c);
+    }
+
+    llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
+    LLVMCompilerUsed =
+      new llvm::GlobalVariable(*mergedModule, ATy, false,
+                               llvm::GlobalValue::AppendingLinkage,
+                               llvm::ConstantArray::get(ATy, asmUsed2),
+                               "llvm.compiler.used");
+
+    LLVMCompilerUsed->setSection("llvm.metadata");
+  }
+
+  passes.add(createInternalizePass(MustPreserveList));
+
+  // apply scope restrictions
+  passes.run(*mergedModule);
+
+  ScopeRestrictionsDone = true;
+}
+
+/// Optimize merged modules using various IPO passes
+bool LTOCodeGenerator::generateObjectFile(raw_ostream &out,
+                                          std::string &errMsg) {
+  if (!this->determineTarget(errMsg))
+    return false;
+
+  Module *mergedModule = Linker.getModule();
+
+  // Mark which symbols can not be internalized
+  this->applyScopeRestrictions();
+
+  // Instantiate the pass manager to organize the passes.
+  PassManager passes;
+
+  // Start off with a verification pass.
+  passes.add(createVerifierPass());
+
+  // Add an appropriate DataLayout instance for this module...
+  passes.add(new DataLayout(*TargetMach->getDataLayout()));
+  TargetMach->addAnalysisPasses(passes);
+
+  // Enabling internalize here would use its AllButMain variant. It
+  // keeps only main if it exists and does nothing for libraries. Instead
+  // we create the pass ourselves with the symbol list provided by the linker.
+  if (!DisableOpt)
+    PassManagerBuilder().populateLTOPassManager(passes,
+                                              /*Internalize=*/false,
+                                              !DisableInline,
+                                              DisableGVNLoadPRE);
+
+  // Make sure everything is still good.
+  passes.add(createVerifierPass());
+
+  PassManager codeGenPasses;
+
+  codeGenPasses.add(new DataLayout(*TargetMach->getDataLayout()));
+  TargetMach->addAnalysisPasses(codeGenPasses);
+
+  formatted_raw_ostream Out(out);
+
+  // If the bitcode files contain ARC code and were compiled with optimization,
+  // the ObjCARCContractPass must be run, so do it unconditionally here.
+  codeGenPasses.add(createObjCARCContractPass());
+
+  if (TargetMach->addPassesToEmitFile(codeGenPasses, Out,
+                                      TargetMachine::CGFT_ObjectFile)) {
+    errMsg = "target file type not supported";
+    return false;
+  }
+
+  // Run our queue of passes all at once now, efficiently.
+  passes.run(*mergedModule);
+
+  // Run the code generator, and write assembly file
+  codeGenPasses.run(*mergedModule);
+
+  return true;
+}
+
+/// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
+/// LTO problems.
+void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
+  for (std::pair<StringRef, StringRef> o = getToken(options);
+       !o.first.empty(); o = getToken(o.second)) {
+    // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
+    // that.
+    if (CodegenOptions.empty())
+      CodegenOptions.push_back(strdup("libLLVMLTO"));
+    CodegenOptions.push_back(strdup(o.first.str().c_str()));
+  }
+}

lib/LTO/LTOModule.cpp

@@ -0,0 +1,900 @@
+//===-- LTOModule.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 Link Time Optimization library. This library is
+// intended to be used by linker to optimize code at link time.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/LTOModule.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCInstrInfo.h"
+#include "llvm/MC/MCParser/MCAsmParser.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSubtargetInfo.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCTargetAsmParser.h"
+#include "llvm/MC/SubtargetFeature.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/system_error.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+using namespace llvm;
+
+static cl::opt<bool>
+EnableFPMAD("enable-fp-mad",
+  cl::desc("Enable less precise MAD instructions to be generated"),
+  cl::init(false));
+
+static cl::opt<bool>
+DisableFPElim("disable-fp-elim",
+  cl::desc("Disable frame pointer elimination optimization"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableUnsafeFPMath("enable-unsafe-fp-math",
+  cl::desc("Enable optimizations that may decrease FP precision"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableNoInfsFPMath("enable-no-infs-fp-math",
+  cl::desc("Enable FP math optimizations that assume no +-Infs"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableNoNaNsFPMath("enable-no-nans-fp-math",
+  cl::desc("Enable FP math optimizations that assume no NaNs"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableHonorSignDependentRoundingFPMath("enable-sign-dependent-rounding-fp-math",
+  cl::Hidden,
+  cl::desc("Force codegen to assume rounding mode can change dynamically"),
+  cl::init(false));
+
+static cl::opt<bool>
+GenerateSoftFloatCalls("soft-float",
+  cl::desc("Generate software floating point library calls"),
+  cl::init(false));
+
+static cl::opt<llvm::FloatABI::ABIType>
+FloatABIForCalls("float-abi",
+  cl::desc("Choose float ABI type"),
+  cl::init(FloatABI::Default),
+  cl::values(
+    clEnumValN(FloatABI::Default, "default",
+               "Target default float ABI type"),
+    clEnumValN(FloatABI::Soft, "soft",
+               "Soft float ABI (implied by -soft-float)"),
+    clEnumValN(FloatABI::Hard, "hard",
+               "Hard float ABI (uses FP registers)"),
+    clEnumValEnd));
+
+static cl::opt<llvm::FPOpFusion::FPOpFusionMode>
+FuseFPOps("fp-contract",
+  cl::desc("Enable aggresive formation of fused FP ops"),
+  cl::init(FPOpFusion::Standard),
+  cl::values(
+    clEnumValN(FPOpFusion::Fast, "fast",
+               "Fuse FP ops whenever profitable"),
+    clEnumValN(FPOpFusion::Standard, "on",
+               "Only fuse 'blessed' FP ops."),
+    clEnumValN(FPOpFusion::Strict, "off",
+               "Only fuse FP ops when the result won't be effected."),
+    clEnumValEnd));
+
+static cl::opt<bool>
+DontPlaceZerosInBSS("nozero-initialized-in-bss",
+  cl::desc("Don't place zero-initialized symbols into bss section"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableGuaranteedTailCallOpt("tailcallopt",
+  cl::desc("Turn fastcc calls into tail calls by (potentially) changing ABI."),
+  cl::init(false));
+
+static cl::opt<bool>
+DisableTailCalls("disable-tail-calls",
+  cl::desc("Never emit tail calls"),
+  cl::init(false));
+
+static cl::opt<unsigned>
+OverrideStackAlignment("stack-alignment",
+  cl::desc("Override default stack alignment"),
+  cl::init(0));
+
+static cl::opt<std::string>
+TrapFuncName("trap-func", cl::Hidden,
+  cl::desc("Emit a call to trap function rather than a trap instruction"),
+  cl::init(""));
+
+static cl::opt<bool>
+EnablePIE("enable-pie",
+  cl::desc("Assume the creation of a position independent executable."),
+  cl::init(false));
+
+static cl::opt<bool>
+SegmentedStacks("segmented-stacks",
+  cl::desc("Use segmented stacks if possible."),
+  cl::init(false));
+
+static cl::opt<bool>
+UseInitArray("use-init-array",
+  cl::desc("Use .init_array instead of .ctors."),
+  cl::init(false));
+
+LTOModule::LTOModule(llvm::Module *m, llvm::TargetMachine *t)
+  : _module(m), _target(t),
+    _context(_target->getMCAsmInfo(), _target->getRegisterInfo(), NULL),
+    _mangler(_context, t) {}
+
+/// isBitcodeFile - Returns 'true' if the file (or memory contents) is LLVM
+/// bitcode.
+bool LTOModule::isBitcodeFile(const void *mem, size_t length) {
+  return sys::fs::identify_magic(StringRef((const char *)mem, length)) ==
+         sys::fs::file_magic::bitcode;
+}
+
+bool LTOModule::isBitcodeFile(const char *path) {
+  sys::fs::file_magic type;
+  if (sys::fs::identify_magic(path, type))
+    return false;
+  return type == sys::fs::file_magic::bitcode;
+}
+
+/// isBitcodeFileForTarget - Returns 'true' if the file (or memory contents) is
+/// LLVM bitcode for the specified triple.
+bool LTOModule::isBitcodeFileForTarget(const void *mem, size_t length,
+                                       const char *triplePrefix) {
+  MemoryBuffer *buffer = makeBuffer(mem, length);
+  if (!buffer)
+    return false;
+  return isTargetMatch(buffer, triplePrefix);
+}
+
+bool LTOModule::isBitcodeFileForTarget(const char *path,
+                                       const char *triplePrefix) {
+  OwningPtr<MemoryBuffer> buffer;
+  if (MemoryBuffer::getFile(path, buffer))
+    return false;
+  return isTargetMatch(buffer.take(), triplePrefix);
+}
+
+/// isTargetMatch - Returns 'true' if the memory buffer is for the specified
+/// target triple.
+bool LTOModule::isTargetMatch(MemoryBuffer *buffer, const char *triplePrefix) {
+  std::string Triple = getBitcodeTargetTriple(buffer, getGlobalContext());
+  delete buffer;
+  return strncmp(Triple.c_str(), triplePrefix, strlen(triplePrefix)) == 0;
+}
+
+/// makeLTOModule - Create an LTOModule. N.B. These methods take ownership of
+/// the buffer.
+LTOModule *LTOModule::makeLTOModule(const char *path, std::string &errMsg) {
+  OwningPtr<MemoryBuffer> buffer;
+  if (error_code ec = MemoryBuffer::getFile(path, buffer)) {
+    errMsg = ec.message();
+    return NULL;
+  }
+  return makeLTOModule(buffer.take(), errMsg);
+}
+
+LTOModule *LTOModule::makeLTOModule(int fd, const char *path,
+                                    size_t size, std::string &errMsg) {
+  return makeLTOModule(fd, path, size, 0, errMsg);
+}
+
+LTOModule *LTOModule::makeLTOModule(int fd, const char *path,
+                                    size_t map_size,
+                                    off_t offset,
+                                    std::string &errMsg) {
+  OwningPtr<MemoryBuffer> buffer;
+  if (error_code ec =
+          MemoryBuffer::getOpenFileSlice(fd, path, buffer, map_size, offset)) {
+    errMsg = ec.message();
+    return NULL;
+  }
+  return makeLTOModule(buffer.take(), errMsg);
+}
+
+LTOModule *LTOModule::makeLTOModule(const void *mem, size_t length,
+                                    std::string &errMsg) {
+  OwningPtr<MemoryBuffer> buffer(makeBuffer(mem, length));
+  if (!buffer)
+    return NULL;
+  return makeLTOModule(buffer.take(), errMsg);
+}
+
+void LTOModule::getTargetOptions(TargetOptions &Options) {
+  Options.LessPreciseFPMADOption = EnableFPMAD;
+  Options.NoFramePointerElim = DisableFPElim;
+  Options.AllowFPOpFusion = FuseFPOps;
+  Options.UnsafeFPMath = EnableUnsafeFPMath;
+  Options.NoInfsFPMath = EnableNoInfsFPMath;
+  Options.NoNaNsFPMath = EnableNoNaNsFPMath;
+  Options.HonorSignDependentRoundingFPMathOption =
+    EnableHonorSignDependentRoundingFPMath;
+  Options.UseSoftFloat = GenerateSoftFloatCalls;
+  if (FloatABIForCalls != FloatABI::Default)
+    Options.FloatABIType = FloatABIForCalls;
+  Options.NoZerosInBSS = DontPlaceZerosInBSS;
+  Options.GuaranteedTailCallOpt = EnableGuaranteedTailCallOpt;
+  Options.DisableTailCalls = DisableTailCalls;
+  Options.StackAlignmentOverride = OverrideStackAlignment;
+  Options.TrapFuncName = TrapFuncName;
+  Options.PositionIndependentExecutable = EnablePIE;
+  Options.EnableSegmentedStacks = SegmentedStacks;
+  Options.UseInitArray = UseInitArray;
+}
+
+LTOModule *LTOModule::makeLTOModule(MemoryBuffer *buffer,
+                                    std::string &errMsg) {
+  // parse bitcode buffer
+  OwningPtr<Module> m(getLazyBitcodeModule(buffer, getGlobalContext(),
+                                           &errMsg));
+  if (!m) {
+    delete buffer;
+    return NULL;
+  }
+
+  std::string TripleStr = m->getTargetTriple();
+  if (TripleStr.empty())
+    TripleStr = sys::getDefaultTargetTriple();
+  llvm::Triple Triple(TripleStr);
+
+  // find machine architecture for this module
+  const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
+  if (!march)
+    return NULL;
+
+  // construct LTOModule, hand over ownership of module and target
+  SubtargetFeatures Features;
+  Features.getDefaultSubtargetFeatures(Triple);
+  std::string FeatureStr = Features.getString();
+  // Set a default CPU for Darwin triples.
+  std::string CPU;
+  if (Triple.isOSDarwin()) {
+    if (Triple.getArch() == llvm::Triple::x86_64)
+      CPU = "core2";
+    else if (Triple.getArch() == llvm::Triple::x86)
+      CPU = "yonah";
+  }
+  TargetOptions Options;
+  getTargetOptions(Options);
+  TargetMachine *target = march->createTargetMachine(TripleStr, CPU, FeatureStr,
+                                                     Options);
+  LTOModule *Ret = new LTOModule(m.take(), target);
+  if (Ret->parseSymbols(errMsg)) {
+    delete Ret;
+    return NULL;
+  }
+
+  return Ret;
+}
+
+/// makeBuffer - Create a MemoryBuffer from a memory range.
+MemoryBuffer *LTOModule::makeBuffer(const void *mem, size_t length) {
+  const char *startPtr = (const char*)mem;
+  return MemoryBuffer::getMemBuffer(StringRef(startPtr, length), "", false);
+}
+
+/// objcClassNameFromExpression - Get string that the data pointer points to.
+bool
+LTOModule::objcClassNameFromExpression(const Constant *c, std::string &name) {
+  if (const ConstantExpr *ce = dyn_cast<ConstantExpr>(c)) {
+    Constant *op = ce->getOperand(0);
+    if (GlobalVariable *gvn = dyn_cast<GlobalVariable>(op)) {
+      Constant *cn = gvn->getInitializer();
+      if (ConstantDataArray *ca = dyn_cast<ConstantDataArray>(cn)) {
+        if (ca->isCString()) {
+          name = ".objc_class_name_" + ca->getAsCString().str();
+          return true;
+        }
+      }
+    }
+  }
+  return false;
+}
+
+/// addObjCClass - Parse i386/ppc ObjC class data structure.
+void LTOModule::addObjCClass(const GlobalVariable *clgv) {
+  const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
+  if (!c) return;
+
+  // second slot in __OBJC,__class is pointer to superclass name
+  std::string superclassName;
+  if (objcClassNameFromExpression(c->getOperand(1), superclassName)) {
+    NameAndAttributes info;
+    StringMap<NameAndAttributes>::value_type &entry =
+      _undefines.GetOrCreateValue(superclassName);
+    if (!entry.getValue().name) {
+      const char *symbolName = entry.getKey().data();
+      info.name = symbolName;
+      info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
+      info.isFunction = false;
+      info.symbol = clgv;
+      entry.setValue(info);
+    }
+  }
+
+  // third slot in __OBJC,__class is pointer to class name
+  std::string className;
+  if (objcClassNameFromExpression(c->getOperand(2), className)) {
+    StringSet::value_type &entry = _defines.GetOrCreateValue(className);
+    entry.setValue(1);
+
+    NameAndAttributes info;
+    info.name = entry.getKey().data();
+    info.attributes = LTO_SYMBOL_PERMISSIONS_DATA |
+      LTO_SYMBOL_DEFINITION_REGULAR | LTO_SYMBOL_SCOPE_DEFAULT;
+    info.isFunction = false;
+    info.symbol = clgv;
+    _symbols.push_back(info);
+  }
+}
+
+/// addObjCCategory - Parse i386/ppc ObjC category data structure.
+void LTOModule::addObjCCategory(const GlobalVariable *clgv) {
+  const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
+  if (!c) return;
+
+  // second slot in __OBJC,__category is pointer to target class name
+  std::string targetclassName;
+  if (!objcClassNameFromExpression(c->getOperand(1), targetclassName))
+    return;
+
+  NameAndAttributes info;
+  StringMap<NameAndAttributes>::value_type &entry =
+    _undefines.GetOrCreateValue(targetclassName);
+
+  if (entry.getValue().name)
+    return;
+
+  const char *symbolName = entry.getKey().data();
+  info.name = symbolName;
+  info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
+  info.isFunction = false;
+  info.symbol = clgv;
+  entry.setValue(info);
+}
+
+/// addObjCClassRef - Parse i386/ppc ObjC class list data structure.
+void LTOModule::addObjCClassRef(const GlobalVariable *clgv) {
+  std::string targetclassName;
+  if (!objcClassNameFromExpression(clgv->getInitializer(), targetclassName))
+    return;
+
+  NameAndAttributes info;
+  StringMap<NameAndAttributes>::value_type &entry =
+    _undefines.GetOrCreateValue(targetclassName);
+  if (entry.getValue().name)
+    return;
+
+  const char *symbolName = entry.getKey().data();
+  info.name = symbolName;
+  info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
+  info.isFunction = false;
+  info.symbol = clgv;
+  entry.setValue(info);
+}
+
+/// addDefinedDataSymbol - Add a data symbol as defined to the list.
+void LTOModule::addDefinedDataSymbol(const GlobalValue *v) {
+  // Add to list of defined symbols.
+  addDefinedSymbol(v, false);
+
+  if (!v->hasSection() /* || !isTargetDarwin */)
+    return;
+
+  // Special case i386/ppc ObjC data structures in magic sections:
+  // The issue is that the old ObjC object format did some strange
+  // contortions to avoid real linker symbols.  For instance, the
+  // ObjC class data structure is allocated statically in the executable
+  // that defines that class.  That data structures contains a pointer to
+  // its superclass.  But instead of just initializing that part of the
+  // struct to the address of its superclass, and letting the static and
+  // dynamic linkers do the rest, the runtime works by having that field
+  // instead point to a C-string that is the name of the superclass.
+  // At runtime the objc initialization updates that pointer and sets
+  // it to point to the actual super class.  As far as the linker
+  // knows it is just a pointer to a string.  But then someone wanted the
+  // linker to issue errors at build time if the superclass was not found.
+  // So they figured out a way in mach-o object format to use an absolute
+  // symbols (.objc_class_name_Foo = 0) and a floating reference
+  // (.reference .objc_class_name_Bar) to cause the linker into erroring when
+  // a class was missing.
+  // The following synthesizes the implicit .objc_* symbols for the linker
+  // from the ObjC data structures generated by the front end.
+
+  // special case if this data blob is an ObjC class definition
+  if (v->getSection().compare(0, 15, "__OBJC,__class,") == 0) {
+    if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
+      addObjCClass(gv);
+    }
+  }
+
+  // special case if this data blob is an ObjC category definition
+  else if (v->getSection().compare(0, 18, "__OBJC,__category,") == 0) {
+    if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
+      addObjCCategory(gv);
+    }
+  }
+
+  // special case if this data blob is the list of referenced classes
+  else if (v->getSection().compare(0, 18, "__OBJC,__cls_refs,") == 0) {
+    if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
+      addObjCClassRef(gv);
+    }
+  }
+}
+
+/// addDefinedFunctionSymbol - Add a function symbol as defined to the list.
+void LTOModule::addDefinedFunctionSymbol(const Function *f) {
+  // add to list of defined symbols
+  addDefinedSymbol(f, true);
+}
+
+/// addDefinedSymbol - Add a defined symbol to the list.
+void LTOModule::addDefinedSymbol(const GlobalValue *def, bool isFunction) {
+  // ignore all llvm.* symbols
+  if (def->getName().startswith("llvm."))
+    return;
+
+  // string is owned by _defines
+  SmallString<64> Buffer;
+  _mangler.getNameWithPrefix(Buffer, def, false);
+
+  // set alignment part log2() can have rounding errors
+  uint32_t align = def->getAlignment();
+  uint32_t attr = align ? countTrailingZeros(def->getAlignment()) : 0;
+
+  // set permissions part
+  if (isFunction) {
+    attr |= LTO_SYMBOL_PERMISSIONS_CODE;
+  } else {
+    const GlobalVariable *gv = dyn_cast<GlobalVariable>(def);
+    if (gv && gv->isConstant())
+      attr |= LTO_SYMBOL_PERMISSIONS_RODATA;
+    else
+      attr |= LTO_SYMBOL_PERMISSIONS_DATA;
+  }
+
+  // set definition part
+  if (def->hasWeakLinkage() || def->hasLinkOnceLinkage() ||
+      def->hasLinkerPrivateWeakLinkage())
+    attr |= LTO_SYMBOL_DEFINITION_WEAK;
+  else if (def->hasCommonLinkage())
+    attr |= LTO_SYMBOL_DEFINITION_TENTATIVE;
+  else
+    attr |= LTO_SYMBOL_DEFINITION_REGULAR;
+
+  // set scope part
+  if (def->hasHiddenVisibility())
+    attr |= LTO_SYMBOL_SCOPE_HIDDEN;
+  else if (def->hasProtectedVisibility())
+    attr |= LTO_SYMBOL_SCOPE_PROTECTED;
+  else if (def->hasExternalLinkage() || def->hasWeakLinkage() ||
+           def->hasLinkOnceLinkage() || def->hasCommonLinkage() ||
+           def->hasLinkerPrivateWeakLinkage())
+    attr |= LTO_SYMBOL_SCOPE_DEFAULT;
+  else if (def->hasLinkOnceODRAutoHideLinkage())
+    attr |= LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
+  else
+    attr |= LTO_SYMBOL_SCOPE_INTERNAL;
+
+  StringSet::value_type &entry = _defines.GetOrCreateValue(Buffer);
+  entry.setValue(1);
+
+  // fill information structure
+  NameAndAttributes info;
+  StringRef Name = entry.getKey();
+  info.name = Name.data();
+  assert(info.name[Name.size()] == '\0');
+  info.attributes = attr;
+  info.isFunction = isFunction;
+  info.symbol = def;
+
+  // add to table of symbols
+  _symbols.push_back(info);
+}
+
+/// addAsmGlobalSymbol - Add a global symbol from module-level ASM to the
+/// defined list.
+void LTOModule::addAsmGlobalSymbol(const char *name,
+                                   lto_symbol_attributes scope) {
+  StringSet::value_type &entry = _defines.GetOrCreateValue(name);
+
+  // only add new define if not already defined
+  if (entry.getValue())
+    return;
+
+  entry.setValue(1);
+
+  NameAndAttributes &info = _undefines[entry.getKey().data()];
+
+  if (info.symbol == 0) {
+    // FIXME: This is trying to take care of module ASM like this:
+    //
+    //   module asm ".zerofill __FOO, __foo, _bar_baz_qux, 0"
+    //
+    // but is gross and its mother dresses it funny. Have the ASM parser give us
+    // more details for this type of situation so that we're not guessing so
+    // much.
+
+    // fill information structure
+    info.name = entry.getKey().data();
+    info.attributes =
+      LTO_SYMBOL_PERMISSIONS_DATA | LTO_SYMBOL_DEFINITION_REGULAR | scope;
+    info.isFunction = false;
+    info.symbol = 0;
+
+    // add to table of symbols
+    _symbols.push_back(info);
+    return;
+  }
+
+  if (info.isFunction)
+    addDefinedFunctionSymbol(cast<Function>(info.symbol));
+  else
+    addDefinedDataSymbol(info.symbol);
+
+  _symbols.back().attributes &= ~LTO_SYMBOL_SCOPE_MASK;
+  _symbols.back().attributes |= scope;
+}
+
+/// addAsmGlobalSymbolUndef - Add a global symbol from module-level ASM to the
+/// undefined list.
+void LTOModule::addAsmGlobalSymbolUndef(const char *name) {
+  StringMap<NameAndAttributes>::value_type &entry =
+    _undefines.GetOrCreateValue(name);
+
+  _asm_undefines.push_back(entry.getKey().data());
+
+  // we already have the symbol
+  if (entry.getValue().name)
+    return;
+
+  uint32_t attr = LTO_SYMBOL_DEFINITION_UNDEFINED;;
+  attr |= LTO_SYMBOL_SCOPE_DEFAULT;
+  NameAndAttributes info;
+  info.name = entry.getKey().data();
+  info.attributes = attr;
+  info.isFunction = false;
+  info.symbol = 0;
+
+  entry.setValue(info);
+}
+
+/// addPotentialUndefinedSymbol - Add a symbol which isn't defined just yet to a
+/// list to be resolved later.
+void
+LTOModule::addPotentialUndefinedSymbol(const GlobalValue *decl, bool isFunc) {
+  // ignore all llvm.* symbols
+  if (decl->getName().startswith("llvm."))
+    return;
+
+  // ignore all aliases
+  if (isa<GlobalAlias>(decl))
+    return;
+
+  SmallString<64> name;
+  _mangler.getNameWithPrefix(name, decl, false);
+
+  StringMap<NameAndAttributes>::value_type &entry =
+    _undefines.GetOrCreateValue(name);
+
+  // we already have the symbol
+  if (entry.getValue().name)
+    return;
+
+  NameAndAttributes info;
+
+  info.name = entry.getKey().data();
+
+  if (decl->hasExternalWeakLinkage())
+    info.attributes = LTO_SYMBOL_DEFINITION_WEAKUNDEF;
+  else
+    info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
+
+  info.isFunction = isFunc;
+  info.symbol = decl;
+
+  entry.setValue(info);
+}
+
+namespace {
+  class RecordStreamer : public MCStreamer {
+  public:
+    enum State { NeverSeen, Global, Defined, DefinedGlobal, Used };
+
+  private:
+    StringMap<State> Symbols;
+
+    void markDefined(const MCSymbol &Symbol) {
+      State &S = Symbols[Symbol.getName()];
+      switch (S) {
+      case DefinedGlobal:
+      case Global:
+        S = DefinedGlobal;
+        break;
+      case NeverSeen:
+      case Defined:
+      case Used:
+        S = Defined;
+        break;
+      }
+    }
+    void markGlobal(const MCSymbol &Symbol) {
+      State &S = Symbols[Symbol.getName()];
+      switch (S) {
+      case DefinedGlobal:
+      case Defined:
+        S = DefinedGlobal;
+        break;
+
+      case NeverSeen:
+      case Global:
+      case Used:
+        S = Global;
+        break;
+      }
+    }
+    void markUsed(const MCSymbol &Symbol) {
+      State &S = Symbols[Symbol.getName()];
+      switch (S) {
+      case DefinedGlobal:
+      case Defined:
+      case Global:
+        break;
+
+      case NeverSeen:
+      case Used:
+        S = Used;
+        break;
+      }
+    }
+
+    // FIXME: mostly copied for the obj streamer.
+    void AddValueSymbols(const MCExpr *Value) {
+      switch (Value->getKind()) {
+      case MCExpr::Target:
+        // FIXME: What should we do in here?
+        break;
+
+      case MCExpr::Constant:
+        break;
+
+      case MCExpr::Binary: {
+        const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
+        AddValueSymbols(BE->getLHS());
+        AddValueSymbols(BE->getRHS());
+        break;
+      }
+
+      case MCExpr::SymbolRef:
+        markUsed(cast<MCSymbolRefExpr>(Value)->getSymbol());
+        break;
+
+      case MCExpr::Unary:
+        AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
+        break;
+      }
+    }
+
+  public:
+    typedef StringMap<State>::const_iterator const_iterator;
+
+    const_iterator begin() {
+      return Symbols.begin();
+    }
+
+    const_iterator end() {
+      return Symbols.end();
+    }
+
+    RecordStreamer(MCContext &Context)
+        : MCStreamer(SK_RecordStreamer, Context) {}
+
+    virtual void EmitInstruction(const MCInst &Inst) {
+      // Scan for values.
+      for (unsigned i = Inst.getNumOperands(); i--; )
+        if (Inst.getOperand(i).isExpr())
+          AddValueSymbols(Inst.getOperand(i).getExpr());
+    }
+    virtual void EmitLabel(MCSymbol *Symbol) {
+      Symbol->setSection(*getCurrentSection().first);
+      markDefined(*Symbol);
+    }
+    virtual void EmitDebugLabel(MCSymbol *Symbol) {
+      EmitLabel(Symbol);
+    }
+    virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
+      // FIXME: should we handle aliases?
+      markDefined(*Symbol);
+    }
+    virtual bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) {
+      if (Attribute == MCSA_Global)
+        markGlobal(*Symbol);
+      return true;
+    }
+    virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
+                              uint64_t Size , unsigned ByteAlignment) {
+      markDefined(*Symbol);
+    }
+    virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
+                                  unsigned ByteAlignment) {
+      markDefined(*Symbol);
+    }
+
+    virtual void EmitBundleAlignMode(unsigned AlignPow2) {}
+    virtual void EmitBundleLock(bool AlignToEnd) {}
+    virtual void EmitBundleUnlock() {}
+
+    // Noop calls.
+    virtual void ChangeSection(const MCSection *Section,
+                               const MCExpr *Subsection) {}
+    virtual void InitToTextSection() {}
+    virtual void InitSections() {}
+    virtual void EmitAssemblerFlag(MCAssemblerFlag Flag) {}
+    virtual void EmitThumbFunc(MCSymbol *Func) {}
+    virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {}
+    virtual void EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {}
+    virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {}
+    virtual void EmitCOFFSymbolStorageClass(int StorageClass) {}
+    virtual void EmitCOFFSymbolType(int Type) {}
+    virtual void EndCOFFSymbolDef() {}
+    virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {}
+    virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
+                                       unsigned ByteAlignment) {}
+    virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
+                                uint64_t Size, unsigned ByteAlignment) {}
+    virtual void EmitBytes(StringRef Data) {}
+    virtual void EmitValueImpl(const MCExpr *Value, unsigned Size) {}
+    virtual void EmitULEB128Value(const MCExpr *Value) {}
+    virtual void EmitSLEB128Value(const MCExpr *Value) {}
+    virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
+                                      unsigned ValueSize,
+                                      unsigned MaxBytesToEmit) {}
+    virtual void EmitCodeAlignment(unsigned ByteAlignment,
+                                   unsigned MaxBytesToEmit) {}
+    virtual bool EmitValueToOffset(const MCExpr *Offset,
+                                   unsigned char Value ) { return false; }
+    virtual void EmitFileDirective(StringRef Filename) {}
+    virtual void EmitDwarfAdvanceLineAddr(int64_t LineDelta,
+                                          const MCSymbol *LastLabel,
+                                          const MCSymbol *Label,
+                                          unsigned PointerSize) {}
+    virtual void FinishImpl() {}
+    virtual void EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
+      RecordProcEnd(Frame);
+    }
+
+    static bool classof(const MCStreamer *S) {
+      return S->getKind() == SK_RecordStreamer;
+    }
+  };
+} // end anonymous namespace
+
+/// addAsmGlobalSymbols - Add global symbols from module-level ASM to the
+/// defined or undefined lists.
+bool LTOModule::addAsmGlobalSymbols(std::string &errMsg) {
+  const std::string &inlineAsm = _module->getModuleInlineAsm();
+  if (inlineAsm.empty())
+    return false;
+
+  OwningPtr<RecordStreamer> Streamer(new RecordStreamer(_context));
+  MemoryBuffer *Buffer = MemoryBuffer::getMemBuffer(inlineAsm);
+  SourceMgr SrcMgr;
+  SrcMgr.AddNewSourceBuffer(Buffer, SMLoc());
+  OwningPtr<MCAsmParser> Parser(createMCAsmParser(SrcMgr,
+                                                  _context, *Streamer,
+                                                  *_target->getMCAsmInfo()));
+  const Target &T = _target->getTarget();
+  OwningPtr<MCInstrInfo> MCII(T.createMCInstrInfo());
+  OwningPtr<MCSubtargetInfo>
+    STI(T.createMCSubtargetInfo(_target->getTargetTriple(),
+                                _target->getTargetCPU(),
+                                _target->getTargetFeatureString()));
+  OwningPtr<MCTargetAsmParser> TAP(T.createMCAsmParser(*STI, *Parser.get(), *MCII));
+  if (!TAP) {
+    errMsg = "target " + std::string(T.getName()) +
+      " does not define AsmParser.";
+    return true;
+  }
+
+  Parser->setTargetParser(*TAP);
+  if (Parser->Run(false))
+    return true;
+
+  for (RecordStreamer::const_iterator i = Streamer->begin(),
+         e = Streamer->end(); i != e; ++i) {
+    StringRef Key = i->first();
+    RecordStreamer::State Value = i->second;
+    if (Value == RecordStreamer::DefinedGlobal)
+      addAsmGlobalSymbol(Key.data(), LTO_SYMBOL_SCOPE_DEFAULT);
+    else if (Value == RecordStreamer::Defined)
+      addAsmGlobalSymbol(Key.data(), LTO_SYMBOL_SCOPE_INTERNAL);
+    else if (Value == RecordStreamer::Global ||
+             Value == RecordStreamer::Used)
+      addAsmGlobalSymbolUndef(Key.data());
+  }
+
+  return false;
+}
+
+/// isDeclaration - Return 'true' if the global value is a declaration.
+static bool isDeclaration(const GlobalValue &V) {
+  if (V.hasAvailableExternallyLinkage())
+    return true;
+
+  if (V.isMaterializable())
+    return false;
+
+  return V.isDeclaration();
+}
+
+/// parseSymbols - Parse the symbols from the module and model-level ASM and add
+/// them to either the defined or undefined lists.
+bool LTOModule::parseSymbols(std::string &errMsg) {
+  // add functions
+  for (Module::iterator f = _module->begin(), e = _module->end(); f != e; ++f) {
+    if (isDeclaration(*f))
+      addPotentialUndefinedSymbol(f, true);
+    else
+      addDefinedFunctionSymbol(f);
+  }
+
+  // add data
+  for (Module::global_iterator v = _module->global_begin(),
+         e = _module->global_end(); v !=  e; ++v) {
+    if (isDeclaration(*v))
+      addPotentialUndefinedSymbol(v, false);
+    else
+      addDefinedDataSymbol(v);
+  }
+
+  // add asm globals
+  if (addAsmGlobalSymbols(errMsg))
+    return true;
+
+  // add aliases
+  for (Module::alias_iterator a = _module->alias_begin(),
+         e = _module->alias_end(); a != e; ++a) {
+    if (isDeclaration(*a->getAliasedGlobal()))
+      // Is an alias to a declaration.
+      addPotentialUndefinedSymbol(a, false);
+    else
+      addDefinedDataSymbol(a);
+  }
+
+  // make symbols for all undefines
+  for (StringMap<NameAndAttributes>::iterator u =_undefines.begin(),
+         e = _undefines.end(); u != e; ++u) {
+    // If this symbol also has a definition, then don't make an undefine because
+    // it is a tentative definition.
+    if (_defines.count(u->getKey())) continue;
+    NameAndAttributes info = u->getValue();
+    _symbols.push_back(info);
+  }
+
+  return false;
+}

lib/LTO/Makefile

@@ -0,0 +1,15 @@
+##===- lib/Linker/Makefile ---------------------------------*- Makefile -*-===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../..
+LIBRARYNAME = LLVMLTO
+BUILD_ARCHIVE := 1
+
+include $(LEVEL)/Makefile.common
+