lib/CodeGen/BackendUtil.cpp - platform/external/clang - Git at Google

 //===--- BackendUtil.cpp - LLVM Backend Utilities -------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//

 #include "clang/CodeGen/BackendUtil.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/TargetOptions.h"
 #include "clang/Basic/LangOptions.h"
 #include "clang/Frontend/CodeGenOptions.h"
 #include "clang/Frontend/FrontendDiagnostic.h"
 #include "llvm/Module.h"
 #include "llvm/PassManager.h"
 #include "llvm/Analysis/Verifier.h"
 #include "llvm/Assembly/PrintModulePass.h"
 #include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm/CodeGen/RegAllocRegistry.h"
 #include "llvm/CodeGen/SchedulerRegistry.h"
 #include "llvm/MC/SubtargetFeature.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FormattedStream.h"
 #include "llvm/Support/PrettyStackTrace.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/Timer.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Target/TargetLibraryInfo.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Transforms/Instrumentation.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
 #include "llvm/Transforms/Scalar.h"
 using namespace clang;
 using namespace llvm;

 namespace {

 class EmitAssemblyHelper {
   DiagnosticsEngine &Diags;
   const CodeGenOptions &CodeGenOpts;
   const clang::TargetOptions &TargetOpts;
   const LangOptions &LangOpts;
   Module *TheModule;

   Timer CodeGenerationTime;

   mutable PassManager *CodeGenPasses;
   mutable PassManager *PerModulePasses;
   mutable FunctionPassManager *PerFunctionPasses;

 private:
   PassManager *getCodeGenPasses() const {
     if (!CodeGenPasses) {
       CodeGenPasses = new PassManager();
       CodeGenPasses->add(new TargetData(TheModule));
     }
     return CodeGenPasses;
   }

   PassManager *getPerModulePasses() const {
     if (!PerModulePasses) {
       PerModulePasses = new PassManager();
       PerModulePasses->add(new TargetData(TheModule));
     }
     return PerModulePasses;
   }

   FunctionPassManager *getPerFunctionPasses() const {
     if (!PerFunctionPasses) {
       PerFunctionPasses = new FunctionPassManager(TheModule);
       PerFunctionPasses->add(new TargetData(TheModule));
     }
     return PerFunctionPasses;
   }

   void CreatePasses();

   /// AddEmitPasses - Add passes necessary to emit assembly or LLVM IR.
   ///
   /// \return True on success.
   bool AddEmitPasses(BackendAction Action, formatted_raw_ostream &OS);

 public:
   EmitAssemblyHelper(DiagnosticsEngine &_Diags,
                      const CodeGenOptions &CGOpts,
                      const clang::TargetOptions &TOpts,
                      const LangOptions &LOpts,
                      Module *M)
     : Diags(_Diags), CodeGenOpts(CGOpts), TargetOpts(TOpts), LangOpts(LOpts),
       TheModule(M), CodeGenerationTime("Code Generation Time"),
       CodeGenPasses(0), PerModulePasses(0), PerFunctionPasses(0) {}

   ~EmitAssemblyHelper() {
     delete CodeGenPasses;
     delete PerModulePasses;
     delete PerFunctionPasses;
   }

   void EmitAssembly(BackendAction Action, raw_ostream *OS);
 };

 }

 static void addObjCARCAPElimPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
   if (Builder.OptLevel > 0)
     PM.add(createObjCARCAPElimPass());
 }

 static void addObjCARCExpandPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
   if (Builder.OptLevel > 0)
     PM.add(createObjCARCExpandPass());
 }

 static void addObjCARCOptPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
   if (Builder.OptLevel > 0)
     PM.add(createObjCARCOptPass());
 }

 static unsigned BoundsChecking;
 static void addBoundsCheckingPass(const PassManagerBuilder &Builder,
                                     PassManagerBase &PM) {
   PM.add(createBoundsCheckingPass(BoundsChecking));
 }

 static void addAddressSanitizerPass(const PassManagerBuilder &Builder,
                                     PassManagerBase &PM) {
   PM.add(createAddressSanitizerPass());
 }

 static void addThreadSanitizerPass(const PassManagerBuilder &Builder,
                                    PassManagerBase &PM) {
   PM.add(createThreadSanitizerPass());
 }

 void EmitAssemblyHelper::CreatePasses() {
   unsigned OptLevel = CodeGenOpts.OptimizationLevel;
   CodeGenOptions::InliningMethod Inlining = CodeGenOpts.Inlining;

   // Handle disabling of LLVM optimization, where we want to preserve the
   // internal module before any optimization.
   if (CodeGenOpts.DisableLLVMOpts) {
     OptLevel = 0;
     Inlining = CodeGenOpts.NoInlining;
   }

   PassManagerBuilder PMBuilder;
   PMBuilder.OptLevel = OptLevel;
   PMBuilder.SizeLevel = CodeGenOpts.OptimizeSize;

   PMBuilder.DisableSimplifyLibCalls = !CodeGenOpts.SimplifyLibCalls;
   PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;

   // In ObjC ARC mode, add the main ARC optimization passes.
   if (LangOpts.ObjCAutoRefCount) {
     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
                            addObjCARCExpandPass);
     PMBuilder.addExtension(PassManagerBuilder::EP_ModuleOptimizerEarly,
                            addObjCARCAPElimPass);
     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
                            addObjCARCOptPass);
   }

   if (CodeGenOpts.BoundsChecking > 0) {
     BoundsChecking = CodeGenOpts.BoundsChecking;
     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
                            addBoundsCheckingPass);
     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                            addBoundsCheckingPass);
   }

   if (LangOpts.AddressSanitizer) {
     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
                            addAddressSanitizerPass);
     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                            addAddressSanitizerPass);
   }

   if (LangOpts.ThreadSanitizer) {
     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
                            addThreadSanitizerPass);
     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
                            addThreadSanitizerPass);
   }

   // Figure out TargetLibraryInfo.
   Triple TargetTriple(TheModule->getTargetTriple());
   PMBuilder.LibraryInfo = new TargetLibraryInfo(TargetTriple);
   if (!CodeGenOpts.SimplifyLibCalls)
     PMBuilder.LibraryInfo->disableAllFunctions();

   switch (Inlining) {
   case CodeGenOptions::NoInlining: break;
   case CodeGenOptions::NormalInlining: {
     // FIXME: Derive these constants in a principled fashion.
     unsigned Threshold = 225;
     if (CodeGenOpts.OptimizeSize == 1)      // -Os
       Threshold = 75;
     else if (CodeGenOpts.OptimizeSize == 2) // -Oz
       Threshold = 25;
     else if (OptLevel > 2)
       Threshold = 275;
     PMBuilder.Inliner = createFunctionInliningPass(Threshold);
     break;
   }
   case CodeGenOptions::OnlyAlwaysInlining:
     // Respect always_inline.
     if (OptLevel == 0)
       // Do not insert lifetime intrinsics at -O0.
       PMBuilder.Inliner = createAlwaysInlinerPass(false);
     else
       PMBuilder.Inliner = createAlwaysInlinerPass();
     break;
   }


   // Set up the per-function pass manager.
   FunctionPassManager *FPM = getPerFunctionPasses();
   if (CodeGenOpts.VerifyModule)
     FPM->add(createVerifierPass());
   PMBuilder.populateFunctionPassManager(*FPM);

   // Set up the per-module pass manager.
   PassManager *MPM = getPerModulePasses();

   if (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes) {
     MPM->add(createGCOVProfilerPass(CodeGenOpts.EmitGcovNotes,
                                     CodeGenOpts.EmitGcovArcs,
                                     TargetTriple.isMacOSX()));

     if (CodeGenOpts.DebugInfo == CodeGenOptions::NoDebugInfo)
       MPM->add(createStripSymbolsPass(true));
   }


   PMBuilder.populateModulePassManager(*MPM);
 }

 bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
                                        formatted_raw_ostream &OS) {
   // Create the TargetMachine for generating code.
   std::string Error;
   std::string Triple = TheModule->getTargetTriple();
   const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
   if (!TheTarget) {
     Diags.Report(diag::err_fe_unable_to_create_target) << Error;
     return false;
   }

   // FIXME: Expose these capabilities via actual APIs!!!! Aside from just
   // being gross, this is also totally broken if we ever care about
   // concurrency.

   TargetMachine::setAsmVerbosityDefault(CodeGenOpts.AsmVerbose);

   TargetMachine::setFunctionSections(CodeGenOpts.FunctionSections);
   TargetMachine::setDataSections    (CodeGenOpts.DataSections);

   // FIXME: Parse this earlier.
   llvm::CodeModel::Model CM;
   if (CodeGenOpts.CodeModel == "small") {
     CM = llvm::CodeModel::Small;
   } else if (CodeGenOpts.CodeModel == "kernel") {
     CM = llvm::CodeModel::Kernel;
   } else if (CodeGenOpts.CodeModel == "medium") {
     CM = llvm::CodeModel::Medium;
   } else if (CodeGenOpts.CodeModel == "large") {
     CM = llvm::CodeModel::Large;
   } else {
     assert(CodeGenOpts.CodeModel.empty() && "Invalid code model!");
     CM = llvm::CodeModel::Default;
   }

   SmallVector<const char *, 16> BackendArgs;
   BackendArgs.push_back("clang"); // Fake program name.
   if (!CodeGenOpts.DebugPass.empty()) {
     BackendArgs.push_back("-debug-pass");
     BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
   }
   if (!CodeGenOpts.LimitFloatPrecision.empty()) {
     BackendArgs.push_back("-limit-float-precision");
     BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
   }
   if (llvm::TimePassesIsEnabled)
     BackendArgs.push_back("-time-passes");
   for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
     BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
   if (CodeGenOpts.NoGlobalMerge)
     BackendArgs.push_back("-global-merge=false");
   BackendArgs.push_back(0);
   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
                                     BackendArgs.data());

   std::string FeaturesStr;
   if (TargetOpts.Features.size()) {
     SubtargetFeatures Features;
     for (std::vector<std::string>::const_iterator
            it = TargetOpts.Features.begin(),
            ie = TargetOpts.Features.end(); it != ie; ++it)
       Features.AddFeature(*it);
     FeaturesStr = Features.getString();
   }

   llvm::Reloc::Model RM = llvm::Reloc::Default;
   if (CodeGenOpts.RelocationModel == "static") {
     RM = llvm::Reloc::Static;
   } else if (CodeGenOpts.RelocationModel == "pic") {
     RM = llvm::Reloc::PIC_;
   } else {
     assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
            "Invalid PIC model!");
     RM = llvm::Reloc::DynamicNoPIC;
   }

   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
   switch (CodeGenOpts.OptimizationLevel) {
   default: break;
   case 0: OptLevel = CodeGenOpt::None; break;
   case 3: OptLevel = CodeGenOpt::Aggressive; break;
   }

   llvm::TargetOptions Options;

   // Set frame pointer elimination mode.
   if (!CodeGenOpts.DisableFPElim) {
     Options.NoFramePointerElim = false;
     Options.NoFramePointerElimNonLeaf = false;
   } else if (CodeGenOpts.OmitLeafFramePointer) {
     Options.NoFramePointerElim = false;
     Options.NoFramePointerElimNonLeaf = true;
   } else {
     Options.NoFramePointerElim = true;
     Options.NoFramePointerElimNonLeaf = true;
   }

   if (CodeGenOpts.UseInitArray)
     Options.UseInitArray = true;

   // Set float ABI type.
   if (CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp")
     Options.FloatABIType = llvm::FloatABI::Soft;
   else if (CodeGenOpts.FloatABI == "hard")
     Options.FloatABIType = llvm::FloatABI::Hard;
   else {
     assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
     Options.FloatABIType = llvm::FloatABI::Default;
   }

   Options.LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
   Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
   Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
   Options.UseSoftFloat = CodeGenOpts.SoftFloat;
   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
   Options.RealignStack = CodeGenOpts.StackRealignment;
   Options.DisableTailCalls = CodeGenOpts.DisableTailCalls;
   Options.TrapFuncName = CodeGenOpts.TrapFuncName;
   Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;

   TargetMachine *TM = TheTarget->createTargetMachine(Triple, TargetOpts.CPU,
                                                      FeaturesStr, Options,
                                                      RM, CM, OptLevel);

   if (CodeGenOpts.RelaxAll)
     TM->setMCRelaxAll(true);
   if (CodeGenOpts.SaveTempLabels)
     TM->setMCSaveTempLabels(true);
   if (CodeGenOpts.NoDwarf2CFIAsm)
     TM->setMCUseCFI(false);
   if (!CodeGenOpts.NoDwarfDirectoryAsm)
     TM->setMCUseDwarfDirectory(true);
   if (CodeGenOpts.NoExecStack)
     TM->setMCNoExecStack(true);

   // Create the code generator passes.
   PassManager *PM = getCodeGenPasses();

   // Add LibraryInfo.
   TargetLibraryInfo *TLI = new TargetLibraryInfo();
   if (!CodeGenOpts.SimplifyLibCalls)
     TLI->disableAllFunctions();
   PM->add(TLI);

   // Normal mode, emit a .s or .o file by running the code generator. Note,
   // this also adds codegenerator level optimization passes.
   TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
   if (Action == Backend_EmitObj)
     CGFT = TargetMachine::CGFT_ObjectFile;
   else if (Action == Backend_EmitMCNull)
     CGFT = TargetMachine::CGFT_Null;
   else
     assert(Action == Backend_EmitAssembly && "Invalid action!");

   // Add ObjC ARC final-cleanup optimizations. This is done as part of the
   // "codegen" passes so that it isn't run multiple times when there is
   // inlining happening.
   if (LangOpts.ObjCAutoRefCount &&
       CodeGenOpts.OptimizationLevel > 0)
     PM->add(createObjCARCContractPass());

   if (TM->addPassesToEmitFile(*PM, OS, CGFT,
                               /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
     Diags.Report(diag::err_fe_unable_to_interface_with_target);
     return false;
   }

   return true;
 }

 void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
   TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : 0);
   llvm::formatted_raw_ostream FormattedOS;

   CreatePasses();
   switch (Action) {
   case Backend_EmitNothing:
     break;

   case Backend_EmitBC:
     getPerModulePasses()->add(createBitcodeWriterPass(*OS));
     break;

   case Backend_EmitLL:
     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
     getPerModulePasses()->add(createPrintModulePass(&FormattedOS));
     break;

   default:
     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
     if (!AddEmitPasses(Action, FormattedOS))
       return;
   }

   // Before executing passes, print the final values of the LLVM options.
   cl::PrintOptionValues();

   // Run passes. For now we do all passes at once, but eventually we
   // would like to have the option of streaming code generation.

   if (PerFunctionPasses) {
     PrettyStackTraceString CrashInfo("Per-function optimization");

     PerFunctionPasses->doInitialization();
     for (Module::iterator I = TheModule->begin(),
            E = TheModule->end(); I != E; ++I)
       if (!I->isDeclaration())
         PerFunctionPasses->run(*I);
     PerFunctionPasses->doFinalization();
   }

   if (PerModulePasses) {
     PrettyStackTraceString CrashInfo("Per-module optimization passes");
     PerModulePasses->run(*TheModule);
   }

   if (CodeGenPasses) {
     PrettyStackTraceString CrashInfo("Code generation");
     CodeGenPasses->run(*TheModule);
   }
 }

 void clang::EmitBackendOutput(DiagnosticsEngine &Diags,
                               const CodeGenOptions &CGOpts,
                               const clang::TargetOptions &TOpts,
                               const LangOptions &LOpts,
                               Module *M,
                               BackendAction Action, raw_ostream *OS) {
   EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, LOpts, M);

   AsmHelper.EmitAssembly(Action, OS);
 }
	//===--- BackendUtil.cpp - LLVM Backend Utilities -------------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//

	#include "clang/CodeGen/BackendUtil.h"
	#include "clang/Basic/Diagnostic.h"
	#include "clang/Basic/TargetOptions.h"
	#include "clang/Basic/LangOptions.h"
	#include "clang/Frontend/CodeGenOptions.h"
	#include "clang/Frontend/FrontendDiagnostic.h"
	#include "llvm/Module.h"
	#include "llvm/PassManager.h"
	#include "llvm/Analysis/Verifier.h"
	#include "llvm/Assembly/PrintModulePass.h"
	#include "llvm/Bitcode/ReaderWriter.h"
	#include "llvm/CodeGen/RegAllocRegistry.h"
	#include "llvm/CodeGen/SchedulerRegistry.h"
	#include "llvm/MC/SubtargetFeature.h"
	#include "llvm/Support/CommandLine.h"
	#include "llvm/Support/FormattedStream.h"
	#include "llvm/Support/PrettyStackTrace.h"
	#include "llvm/Support/TargetRegistry.h"
	#include "llvm/Support/Timer.h"
	#include "llvm/Support/raw_ostream.h"
	#include "llvm/Target/TargetData.h"
	#include "llvm/Target/TargetLibraryInfo.h"
	#include "llvm/Target/TargetMachine.h"
	#include "llvm/Target/TargetOptions.h"
	#include "llvm/Transforms/Instrumentation.h"
	#include "llvm/Transforms/IPO.h"
	#include "llvm/Transforms/IPO/PassManagerBuilder.h"
	#include "llvm/Transforms/Scalar.h"
	using namespace clang;
	using namespace llvm;

	namespace {

	class EmitAssemblyHelper {
	DiagnosticsEngine &Diags;
	const CodeGenOptions &CodeGenOpts;
	const clang::TargetOptions &TargetOpts;
	const LangOptions &LangOpts;
	Module *TheModule;

	Timer CodeGenerationTime;

	mutable PassManager *CodeGenPasses;
	mutable PassManager *PerModulePasses;
	mutable FunctionPassManager *PerFunctionPasses;

	private:
	PassManager *getCodeGenPasses() const {
	if (!CodeGenPasses) {
	CodeGenPasses = new PassManager();
	CodeGenPasses->add(new TargetData(TheModule));
	}
	return CodeGenPasses;
	}

	PassManager *getPerModulePasses() const {
	if (!PerModulePasses) {
	PerModulePasses = new PassManager();
	PerModulePasses->add(new TargetData(TheModule));
	}
	return PerModulePasses;
	}

	FunctionPassManager *getPerFunctionPasses() const {
	if (!PerFunctionPasses) {
	PerFunctionPasses = new FunctionPassManager(TheModule);
	PerFunctionPasses->add(new TargetData(TheModule));
	}
	return PerFunctionPasses;
	}

	void CreatePasses();

	/// AddEmitPasses - Add passes necessary to emit assembly or LLVM IR.
	///
	/// \return True on success.
	bool AddEmitPasses(BackendAction Action, formatted_raw_ostream &OS);

	public:
	EmitAssemblyHelper(DiagnosticsEngine &_Diags,
	const CodeGenOptions &CGOpts,
	const clang::TargetOptions &TOpts,
	const LangOptions &LOpts,
	Module *M)
	: Diags(_Diags), CodeGenOpts(CGOpts), TargetOpts(TOpts), LangOpts(LOpts),
	TheModule(M), CodeGenerationTime("Code Generation Time"),
	CodeGenPasses(0), PerModulePasses(0), PerFunctionPasses(0) {}

	~EmitAssemblyHelper() {
	delete CodeGenPasses;
	delete PerModulePasses;
	delete PerFunctionPasses;
	}

	void EmitAssembly(BackendAction Action, raw_ostream *OS);
	};

	}

	static void addObjCARCAPElimPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
	if (Builder.OptLevel > 0)
	PM.add(createObjCARCAPElimPass());
	}

	static void addObjCARCExpandPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
	if (Builder.OptLevel > 0)
	PM.add(createObjCARCExpandPass());
	}

	static void addObjCARCOptPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
	if (Builder.OptLevel > 0)
	PM.add(createObjCARCOptPass());
	}

	static unsigned BoundsChecking;
	static void addBoundsCheckingPass(const PassManagerBuilder &Builder,
	PassManagerBase &PM) {
	PM.add(createBoundsCheckingPass(BoundsChecking));
	}

	static void addAddressSanitizerPass(const PassManagerBuilder &Builder,
	PassManagerBase &PM) {
	PM.add(createAddressSanitizerPass());
	}

	static void addThreadSanitizerPass(const PassManagerBuilder &Builder,
	PassManagerBase &PM) {
	PM.add(createThreadSanitizerPass());
	}

	void EmitAssemblyHelper::CreatePasses() {
	unsigned OptLevel = CodeGenOpts.OptimizationLevel;
	CodeGenOptions::InliningMethod Inlining = CodeGenOpts.Inlining;

	// Handle disabling of LLVM optimization, where we want to preserve the
	// internal module before any optimization.
	if (CodeGenOpts.DisableLLVMOpts) {
	OptLevel = 0;
	Inlining = CodeGenOpts.NoInlining;
	}

	PassManagerBuilder PMBuilder;
	PMBuilder.OptLevel = OptLevel;
	PMBuilder.SizeLevel = CodeGenOpts.OptimizeSize;

	PMBuilder.DisableSimplifyLibCalls = !CodeGenOpts.SimplifyLibCalls;
	PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
	PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;

	// In ObjC ARC mode, add the main ARC optimization passes.
	if (LangOpts.ObjCAutoRefCount) {
	PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
	addObjCARCExpandPass);
	PMBuilder.addExtension(PassManagerBuilder::EP_ModuleOptimizerEarly,
	addObjCARCAPElimPass);
	PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
	addObjCARCOptPass);
	}

	if (CodeGenOpts.BoundsChecking > 0) {
	BoundsChecking = CodeGenOpts.BoundsChecking;
	PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
	addBoundsCheckingPass);
	PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
	addBoundsCheckingPass);
	}

	if (LangOpts.AddressSanitizer) {
	PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
	addAddressSanitizerPass);
	PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
	addAddressSanitizerPass);
	}

	if (LangOpts.ThreadSanitizer) {
	PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
	addThreadSanitizerPass);
	PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
	addThreadSanitizerPass);
	}

	// Figure out TargetLibraryInfo.
	Triple TargetTriple(TheModule->getTargetTriple());
	PMBuilder.LibraryInfo = new TargetLibraryInfo(TargetTriple);
	if (!CodeGenOpts.SimplifyLibCalls)
	PMBuilder.LibraryInfo->disableAllFunctions();

	switch (Inlining) {
	case CodeGenOptions::NoInlining: break;
	case CodeGenOptions::NormalInlining: {
	// FIXME: Derive these constants in a principled fashion.
	unsigned Threshold = 225;
	if (CodeGenOpts.OptimizeSize == 1) // -Os
	Threshold = 75;
	else if (CodeGenOpts.OptimizeSize == 2) // -Oz
	Threshold = 25;
	else if (OptLevel > 2)
	Threshold = 275;
	PMBuilder.Inliner = createFunctionInliningPass(Threshold);
	break;
	}
	case CodeGenOptions::OnlyAlwaysInlining:
	// Respect always_inline.
	if (OptLevel == 0)
	// Do not insert lifetime intrinsics at -O0.
	PMBuilder.Inliner = createAlwaysInlinerPass(false);
	else
	PMBuilder.Inliner = createAlwaysInlinerPass();
	break;
	}


	// Set up the per-function pass manager.
	FunctionPassManager *FPM = getPerFunctionPasses();
	if (CodeGenOpts.VerifyModule)
	FPM->add(createVerifierPass());
	PMBuilder.populateFunctionPassManager(*FPM);

	// Set up the per-module pass manager.
	PassManager *MPM = getPerModulePasses();

	if (CodeGenOpts.EmitGcovArcs \|\| CodeGenOpts.EmitGcovNotes) {
	MPM->add(createGCOVProfilerPass(CodeGenOpts.EmitGcovNotes,
	CodeGenOpts.EmitGcovArcs,
	TargetTriple.isMacOSX()));

	if (CodeGenOpts.DebugInfo == CodeGenOptions::NoDebugInfo)
	MPM->add(createStripSymbolsPass(true));
	}


	PMBuilder.populateModulePassManager(*MPM);
	}

	bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
	formatted_raw_ostream &OS) {
	// Create the TargetMachine for generating code.
	std::string Error;
	std::string Triple = TheModule->getTargetTriple();
	const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
	if (!TheTarget) {
	Diags.Report(diag::err_fe_unable_to_create_target) << Error;
	return false;
	}

	// FIXME: Expose these capabilities via actual APIs!!!! Aside from just
	// being gross, this is also totally broken if we ever care about
	// concurrency.

	TargetMachine::setAsmVerbosityDefault(CodeGenOpts.AsmVerbose);

	TargetMachine::setFunctionSections(CodeGenOpts.FunctionSections);
	TargetMachine::setDataSections (CodeGenOpts.DataSections);

	// FIXME: Parse this earlier.
	llvm::CodeModel::Model CM;
	if (CodeGenOpts.CodeModel == "small") {
	CM = llvm::CodeModel::Small;
	} else if (CodeGenOpts.CodeModel == "kernel") {
	CM = llvm::CodeModel::Kernel;
	} else if (CodeGenOpts.CodeModel == "medium") {
	CM = llvm::CodeModel::Medium;
	} else if (CodeGenOpts.CodeModel == "large") {
	CM = llvm::CodeModel::Large;
	} else {
	assert(CodeGenOpts.CodeModel.empty() && "Invalid code model!");
	CM = llvm::CodeModel::Default;
	}

	SmallVector<const char *, 16> BackendArgs;
	BackendArgs.push_back("clang"); // Fake program name.
	if (!CodeGenOpts.DebugPass.empty()) {
	BackendArgs.push_back("-debug-pass");
	BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
	}
	if (!CodeGenOpts.LimitFloatPrecision.empty()) {
	BackendArgs.push_back("-limit-float-precision");
	BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
	}
	if (llvm::TimePassesIsEnabled)
	BackendArgs.push_back("-time-passes");
	for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
	BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
	if (CodeGenOpts.NoGlobalMerge)
	BackendArgs.push_back("-global-merge=false");
	BackendArgs.push_back(0);
	llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
	BackendArgs.data());

	std::string FeaturesStr;
	if (TargetOpts.Features.size()) {
	SubtargetFeatures Features;
	for (std::vector<std::string>::const_iterator
	it = TargetOpts.Features.begin(),
	ie = TargetOpts.Features.end(); it != ie; ++it)
	Features.AddFeature(*it);
	FeaturesStr = Features.getString();
	}

	llvm::Reloc::Model RM = llvm::Reloc::Default;
	if (CodeGenOpts.RelocationModel == "static") {
	RM = llvm::Reloc::Static;
	} else if (CodeGenOpts.RelocationModel == "pic") {
	RM = llvm::Reloc::PIC_;
	} else {
	assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
	"Invalid PIC model!");
	RM = llvm::Reloc::DynamicNoPIC;
	}

	CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
	switch (CodeGenOpts.OptimizationLevel) {
	default: break;
	case 0: OptLevel = CodeGenOpt::None; break;
	case 3: OptLevel = CodeGenOpt::Aggressive; break;
	}

	llvm::TargetOptions Options;

	// Set frame pointer elimination mode.
	if (!CodeGenOpts.DisableFPElim) {
	Options.NoFramePointerElim = false;
	Options.NoFramePointerElimNonLeaf = false;
	} else if (CodeGenOpts.OmitLeafFramePointer) {
	Options.NoFramePointerElim = false;
	Options.NoFramePointerElimNonLeaf = true;
	} else {
	Options.NoFramePointerElim = true;
	Options.NoFramePointerElimNonLeaf = true;
	}

	if (CodeGenOpts.UseInitArray)
	Options.UseInitArray = true;

	// Set float ABI type.
	if (CodeGenOpts.FloatABI == "soft" \|\| CodeGenOpts.FloatABI == "softfp")
	Options.FloatABIType = llvm::FloatABI::Soft;
	else if (CodeGenOpts.FloatABI == "hard")
	Options.FloatABIType = llvm::FloatABI::Hard;
	else {
	assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
	Options.FloatABIType = llvm::FloatABI::Default;
	}

	Options.LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
	Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
	Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
	Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
	Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
	Options.UseSoftFloat = CodeGenOpts.SoftFloat;
	Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
	Options.RealignStack = CodeGenOpts.StackRealignment;
	Options.DisableTailCalls = CodeGenOpts.DisableTailCalls;
	Options.TrapFuncName = CodeGenOpts.TrapFuncName;
	Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;

	TargetMachine *TM = TheTarget->createTargetMachine(Triple, TargetOpts.CPU,
	FeaturesStr, Options,
	RM, CM, OptLevel);

	if (CodeGenOpts.RelaxAll)
	TM->setMCRelaxAll(true);
	if (CodeGenOpts.SaveTempLabels)
	TM->setMCSaveTempLabels(true);
	if (CodeGenOpts.NoDwarf2CFIAsm)
	TM->setMCUseCFI(false);
	if (!CodeGenOpts.NoDwarfDirectoryAsm)
	TM->setMCUseDwarfDirectory(true);
	if (CodeGenOpts.NoExecStack)
	TM->setMCNoExecStack(true);

	// Create the code generator passes.
	PassManager *PM = getCodeGenPasses();

	// Add LibraryInfo.
	TargetLibraryInfo *TLI = new TargetLibraryInfo();
	if (!CodeGenOpts.SimplifyLibCalls)
	TLI->disableAllFunctions();
	PM->add(TLI);

	// Normal mode, emit a .s or .o file by running the code generator. Note,
	// this also adds codegenerator level optimization passes.
	TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
	if (Action == Backend_EmitObj)
	CGFT = TargetMachine::CGFT_ObjectFile;
	else if (Action == Backend_EmitMCNull)
	CGFT = TargetMachine::CGFT_Null;
	else
	assert(Action == Backend_EmitAssembly && "Invalid action!");

	// Add ObjC ARC final-cleanup optimizations. This is done as part of the
	// "codegen" passes so that it isn't run multiple times when there is
	// inlining happening.
	if (LangOpts.ObjCAutoRefCount &&
	CodeGenOpts.OptimizationLevel > 0)
	PM->add(createObjCARCContractPass());

	if (TM->addPassesToEmitFile(*PM, OS, CGFT,
	/DisableVerify=/!CodeGenOpts.VerifyModule)) {
	Diags.Report(diag::err_fe_unable_to_interface_with_target);
	return false;
	}

	return true;
	}

	void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
	TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : 0);
	llvm::formatted_raw_ostream FormattedOS;

	CreatePasses();
	switch (Action) {
	case Backend_EmitNothing:
	break;

	case Backend_EmitBC:
	getPerModulePasses()->add(createBitcodeWriterPass(*OS));
	break;

	case Backend_EmitLL:
	FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
	getPerModulePasses()->add(createPrintModulePass(&FormattedOS));
	break;

	default:
	FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
	if (!AddEmitPasses(Action, FormattedOS))
	return;
	}

	// Before executing passes, print the final values of the LLVM options.
	cl::PrintOptionValues();

	// Run passes. For now we do all passes at once, but eventually we
	// would like to have the option of streaming code generation.

	if (PerFunctionPasses) {
	PrettyStackTraceString CrashInfo("Per-function optimization");

	PerFunctionPasses->doInitialization();
	for (Module::iterator I = TheModule->begin(),
	E = TheModule->end(); I != E; ++I)
	if (!I->isDeclaration())
	PerFunctionPasses->run(*I);
	PerFunctionPasses->doFinalization();
	}

	if (PerModulePasses) {
	PrettyStackTraceString CrashInfo("Per-module optimization passes");
	PerModulePasses->run(*TheModule);
	}

	if (CodeGenPasses) {
	PrettyStackTraceString CrashInfo("Code generation");
	CodeGenPasses->run(*TheModule);
	}
	}

	void clang::EmitBackendOutput(DiagnosticsEngine &Diags,
	const CodeGenOptions &CGOpts,
	const clang::TargetOptions &TOpts,
	const LangOptions &LOpts,
	Module *M,
	BackendAction Action, raw_ostream *OS) {
	EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, LOpts, M);

	AsmHelper.EmitAssembly(Action, OS);
	}