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llvm-mirror/lib/LTO/LTOCodeGenerator.cpp
Rafael Espindola 24353f2de2 Use LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN instead of the "dso list". 
There are two ways one could implement hiding of linkonce_odr symbols in LTO:
* LLVM tells the linker which symbols can be hidden if not used from native
  files.
* The linker tells LLVM which symbols are not used from other object files,
  but will be put in the dso symbol table if present.

GOLD's API is the second option. It was implemented almost 1:1 in llvm by
passing the list down to internalize.

LLVM already had partial support for the first option. It is also very similar
to how ld64 handles hiding these symbols when *not* doing LTO.

This patch then
* removes the APIs for the DSO list.
* marks LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN all linkonce_odr unnamed_addr
  global values and other linkonce_odr whose address is not used.
* makes the gold plugin responsible for handling the API mismatch.

llvm-svn: 193800
2013-10-31 20:51:58 +00:00

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//===-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/TargetOptions.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;
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;
TargetMach = NULL;
NativeObjectFile = NULL;
Linker.deleteModule();
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::setTargetOptions(TargetOptions options) {
Options.LessPreciseFPMADOption = options.LessPreciseFPMADOption;
Options.NoFramePointerElim = options.NoFramePointerElim;
Options.AllowFPOpFusion = options.AllowFPOpFusion;
Options.UnsafeFPMath = options.UnsafeFPMath;
Options.NoInfsFPMath = options.NoInfsFPMath;
Options.NoNaNsFPMath = options.NoNaNsFPMath;
Options.HonorSignDependentRoundingFPMathOption =
options.HonorSignDependentRoundingFPMathOption;
Options.UseSoftFloat = options.UseSoftFloat;
Options.FloatABIType = options.FloatABIType;
Options.NoZerosInBSS = options.NoZerosInBSS;
Options.GuaranteedTailCallOpt = options.GuaranteedTailCallOpt;
Options.DisableTailCalls = options.DisableTailCalls;
Options.StackAlignmentOverride = options.StackAlignmentOverride;
Options.TrapFuncName = options.TrapFuncName;
Options.PositionIndependentExecutable = options.PositionIndependentExecutable;
Options.EnableSegmentedStacks = options.EnableSegmentedStacks;
Options.UseInitArray = options.UseInitArray;
}
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,
bool disableOpt,
bool disableInline,
bool disableGVNLoadPRE,
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(), disableOpt, disableInline,
disableGVNLoadPRE, 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,
bool disableOpt,
bool disableInline,
bool disableGVNLoadPRE,
std::string& errMsg) {
const char *name;
if (!compile_to_file(&name, disableOpt, disableInline, disableGVNLoadPRE,
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;
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";
}
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
Mangler Mangler(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,
bool DisableOpt,
bool DisableInline,
bool DisableGVNLoadPRE,
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()));
}
}
void LTOCodeGenerator::parseCodeGenDebugOptions() {
// if options were requested, set them
if (!CodegenOptions.empty())
cl::ParseCommandLineOptions(CodegenOptions.size(),
const_cast<char **>(&CodegenOptions[0]));
}
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