llvm-6502/tools/lto/LTOCodeGenerator.cpp
Peter Collingbourne 988fdc5f28 Now that the linker supports lazily materialising globals, don't
materialise them in LTO.

I observed a ~0.5-1% speedup for an LTO link of opt.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143784 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-05 04:17:25 +00:00

432 lines
13 KiB
C++

//===-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 "LTOModule.h"
#include "LTOCodeGenerator.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Linker.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/Verifier.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Target/Mangler.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/SystemUtils.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/system_error.h"
#include "llvm/Config/config.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#include <cstdlib>
#include <unistd.h>
#include <fcntl.h>
using namespace llvm;
static cl::opt<bool> DisableInline("disable-inlining",
cl::desc("Do not run the inliner 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("LinkTimeOptimizer", "ld-temp.o", _context), _target(NULL),
_emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
_codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
_nativeObjectFile(NULL)
{
InitializeAllTargets();
InitializeAllTargetMCs();
InitializeAllAsmPrinters();
}
LTOCodeGenerator::~LTOCodeGenerator()
{
delete _target;
delete _nativeObjectFile;
}
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;
}
bool LTOCodeGenerator::setDebugInfo(lto_debug_model debug, std::string& errMsg)
{
switch (debug) {
case LTO_DEBUG_MODEL_NONE:
_emitDwarfDebugInfo = false;
return false;
case LTO_DEBUG_MODEL_DWARF:
_emitDwarfDebugInfo = true;
return false;
}
errMsg = "unknown debug format";
return true;
}
bool LTOCodeGenerator::setCodePICModel(lto_codegen_model model,
std::string& errMsg)
{
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 false;
}
errMsg = "unknown pic model";
return true;
}
void LTOCodeGenerator::setCpu(const char* mCpu)
{
_mCpu = mCpu;
}
void LTOCodeGenerator::addMustPreserveSymbol(const char* sym)
{
_mustPreserveSymbols[sym] = 1;
}
bool LTOCodeGenerator::writeMergedModules(const char *path,
std::string &errMsg) {
if (determineTarget(errMsg))
return true;
// mark which symbols can not be internalized
applyScopeRestrictions();
// create output file
std::string ErrInfo;
tool_output_file Out(path, ErrInfo,
raw_fd_ostream::F_Binary);
if (!ErrInfo.empty()) {
errMsg = "could not open bitcode file for writing: ";
errMsg += path;
return true;
}
// 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 true;
}
Out.keep();
return false;
}
bool LTOCodeGenerator::compile_to_file(const char** name, std::string& errMsg)
{
// make unique temp .o file to put generated object file
sys::PathWithStatus uniqueObjPath("lto-llvm.o");
if ( uniqueObjPath.createTemporaryFileOnDisk(false, &errMsg) ) {
uniqueObjPath.eraseFromDisk();
return true;
}
sys::RemoveFileOnSignal(uniqueObjPath);
// generate object file
bool genResult = false;
tool_output_file objFile(uniqueObjPath.c_str(), errMsg);
if (!errMsg.empty())
return true;
genResult = this->generateObjectFile(objFile.os(), errMsg);
objFile.os().close();
if (objFile.os().has_error()) {
objFile.os().clear_error();
return true;
}
objFile.keep();
if ( genResult ) {
uniqueObjPath.eraseFromDisk();
return true;
}
_nativeObjectPath = uniqueObjPath.str();
*name = _nativeObjectPath.c_str();
return false;
}
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();
return NULL;
}
_nativeObjectFile = BuffPtr.take();
// remove temp files
sys::Path(_nativeObjectPath).eraseFromDisk();
// return buffer, unless error
if ( _nativeObjectFile == NULL )
return NULL;
*length = _nativeObjectFile->getBufferSize();
return _nativeObjectFile->getBufferStart();
}
bool LTOCodeGenerator::determineTarget(std::string& errMsg)
{
if ( _target == NULL ) {
std::string Triple = _linker.getModule()->getTargetTriple();
if (Triple.empty())
Triple = sys::getDefaultTargetTriple();
// create target machine from info for merged modules
const Target *march = TargetRegistry::lookupTarget(Triple, errMsg);
if ( march == NULL )
return true;
// 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(llvm::Triple(Triple));
std::string FeatureStr = Features.getString();
_target = march->createTargetMachine(Triple, _mCpu, FeatureStr,
RelocModel);
}
return false;
}
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 = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
if (Inits == 0) return;
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 Context(*_target->getMCAsmInfo(), *_target->getRegisterInfo(), NULL);
Mangler mangler(Context, *_target->getTargetData());
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();
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 true;
// mark which symbols can not be internalized
this->applyScopeRestrictions();
Module* mergedModule = _linker.getModule();
// if options were requested, set them
if ( !_codegenOptions.empty() )
cl::ParseCommandLineOptions(_codegenOptions.size(),
const_cast<char **>(&_codegenOptions[0]));
// Instantiate the pass manager to organize the passes.
PassManager passes;
// Start off with a verification pass.
passes.add(createVerifierPass());
// Add an appropriate TargetData instance for this module...
passes.add(new TargetData(*_target->getTargetData()));
PassManagerBuilder().populateLTOPassManager(passes, /*Internalize=*/ false,
!DisableInline);
// Make sure everything is still good.
passes.add(createVerifierPass());
FunctionPassManager *codeGenPasses = new FunctionPassManager(mergedModule);
codeGenPasses->add(new TargetData(*_target->getTargetData()));
formatted_raw_ostream Out(out);
if (_target->addPassesToEmitFile(*codeGenPasses, Out,
TargetMachine::CGFT_ObjectFile,
CodeGenOpt::Aggressive)) {
errMsg = "target file type not supported";
return true;
}
// Run our queue of passes all at once now, efficiently.
passes.run(*mergedModule);
// Run the code generator, and write assembly file
codeGenPasses->doInitialization();
for (Module::iterator
it = mergedModule->begin(), e = mergedModule->end(); it != e; ++it)
if (!it->isDeclaration())
codeGenPasses->run(*it);
codeGenPasses->doFinalization();
delete codeGenPasses;
return false; // success
}
/// Optimize merged modules using various IPO passes
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("libLTO");
_codegenOptions.push_back(strdup(o.first.str().c_str()));
}
}