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//===- LTO.cpp ------------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "LTO.h"
#include "Config.h"
#include "Error.h"
#include "InputFiles.h"
#include "Symbols.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/CodeGen/CommandFlags.h"
#include "llvm/CodeGen/ParallelCG.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/Linker/IRMover.h"
#include "llvm/Support/StringSaver.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf;
// This is for use when debugging LTO.
static void saveLtoObjectFile(StringRef Buffer, unsigned I, bool Many) {
SmallString<128> Filename = Config->OutputFile;
if (Many)
Filename += utostr(I);
Filename += ".lto.o";
std::error_code EC;
raw_fd_ostream OS(Filename, EC, sys::fs::OpenFlags::F_None);
check(EC);
OS << Buffer;
}
// This is for use when debugging LTO.
static void saveBCFile(Module &M, StringRef Suffix) {
std::error_code EC;
raw_fd_ostream OS(Config->OutputFile.str() + Suffix.str(), EC,
sys::fs::OpenFlags::F_None);
check(EC);
WriteBitcodeToFile(&M, OS, /* ShouldPreserveUseListOrder */ true);
}
// Run LTO passes.
// Note that the gold plugin has a similar piece of code, so
// it is probably better to move this code to a common place.
static void runLTOPasses(Module &M, TargetMachine &TM) {
legacy::PassManager LtoPasses;
LtoPasses.add(createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis()));
PassManagerBuilder PMB;
PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM.getTargetTriple()));
PMB.Inliner = createFunctionInliningPass();
PMB.VerifyInput = PMB.VerifyOutput = !Config->DisableVerify;
PMB.LoopVectorize = true;
PMB.SLPVectorize = true;
PMB.OptLevel = Config->LtoO;
PMB.populateLTOPassManager(LtoPasses);
LtoPasses.run(M);
if (Config->SaveTemps)
saveBCFile(M, ".lto.opt.bc");
}
static bool shouldInternalize(const SmallPtrSet<GlobalValue *, 8> &Used,
SymbolBody &B, GlobalValue *GV) {
if (B.Backref->IsUsedInRegularObj)
return false;
if (Used.count(GV))
return false;
return !B.Backref->includeInDynsym();
}
BitcodeCompiler::BitcodeCompiler()
: Combined(new llvm::Module("ld-temp.o", Context)), Mover(*Combined) {
// This is a flag to discard all but GlobalValue names.
// We want to enable it by default because it saves memory.
// Disable it only when a developer option (-save-temps) is given.
Context.setDiscardValueNames(!Config->SaveTemps);
Context.enableDebugTypeODRUniquing();
}
void BitcodeCompiler::add(BitcodeFile &F) {
std::unique_ptr<IRObjectFile> Obj =
check(IRObjectFile::create(F.MB, Context));
std::vector<GlobalValue *> Keep;
unsigned BodyIndex = 0;
ArrayRef<SymbolBody *> Bodies = F.getSymbols();
Module &M = Obj->getModule();
if (M.getDataLayoutStr().empty())
fatal("invalid bitcode file: " + F.getName() + " has no datalayout");
// If a symbol appears in @llvm.used, the linker is required
// to treat the symbol as there is a reference to the symbol
// that it cannot see. Therefore, we can't internalize.
SmallPtrSet<GlobalValue *, 8> Used;
collectUsedGlobalVariables(M, Used, /* CompilerUsed */ false);
for (const BasicSymbolRef &Sym : Obj->symbols()) {
GlobalValue *GV = Obj->getSymbolGV(Sym.getRawDataRefImpl());
// Ignore module asm symbols.
if (!GV)
continue;
if (GV->hasAppendingLinkage()) {
Keep.push_back(GV);
continue;
}
if (BitcodeFile::shouldSkip(Sym))
continue;
SymbolBody *B = Bodies[BodyIndex++];
if (!B || &B->repl() != B || !isa<DefinedBitcode>(B))
continue;
switch (GV->getLinkage()) {
default:
break;
case llvm::GlobalValue::LinkOnceAnyLinkage:
GV->setLinkage(GlobalValue::WeakAnyLinkage);
break;
case llvm::GlobalValue::LinkOnceODRLinkage:
GV->setLinkage(GlobalValue::WeakODRLinkage);
break;
}
// We collect the set of symbols we want to internalize here
// and change the linkage after the IRMover executed, i.e. after
// we imported the symbols and satisfied undefined references
// to it. We can't just change linkage here because otherwise
// the IRMover will just rename the symbol.
if (shouldInternalize(Used, *B, GV))
InternalizedSyms.insert(GV->getName());
Keep.push_back(GV);
}
Mover.move(Obj->takeModule(), Keep,
[](GlobalValue &, IRMover::ValueAdder) {});
}
static void internalize(GlobalValue &GV) {
assert(!GV.hasLocalLinkage() &&
"Trying to internalize a symbol with local linkage!");
GV.setLinkage(GlobalValue::InternalLinkage);
}
std::vector<std::unique_ptr<InputFile>> BitcodeCompiler::runSplitCodegen(
const std::function<std::unique_ptr<TargetMachine>()> &TMFactory) {
unsigned NumThreads = Config->LtoJobs;
OwningData.resize(NumThreads);
std::list<raw_svector_ostream> OSs;
std::vector<raw_pwrite_stream *> OSPtrs;
for (SmallString<0> &Obj : OwningData) {
OSs.emplace_back(Obj);
OSPtrs.push_back(&OSs.back());
}
splitCodeGen(std::move(Combined), OSPtrs, {}, TMFactory);
std::vector<std::unique_ptr<InputFile>> ObjFiles;
for (SmallString<0> &Obj : OwningData)
ObjFiles.push_back(createObjectFile(
MemoryBufferRef(Obj, "LLD-INTERNAL-combined-lto-object")));
if (Config->SaveTemps)
for (unsigned I = 0; I < NumThreads; ++I)
saveLtoObjectFile(OwningData[I], I, NumThreads > 1);
return ObjFiles;
}
// Merge all the bitcode files we have seen, codegen the result
// and return the resulting ObjectFile.
std::vector<std::unique_ptr<InputFile>> BitcodeCompiler::compile() {
TheTriple = Combined->getTargetTriple();
for (const auto &Name : InternalizedSyms) {
GlobalValue *GV = Combined->getNamedValue(Name.first());
assert(GV);
internalize(*GV);
}
if (Config->SaveTemps)
saveBCFile(*Combined, ".lto.bc");
std::string Msg;
const Target *T = TargetRegistry::lookupTarget(TheTriple, Msg);
if (!T)
fatal("target not found: " + Msg);
TargetOptions Options = InitTargetOptionsFromCodeGenFlags();
Reloc::Model R = Config->Pic ? Reloc::PIC_ : Reloc::Static;
auto CreateTargetMachine = [&]() {
return std::unique_ptr<TargetMachine>(
T->createTargetMachine(TheTriple, "", "", Options, R));
};
std::unique_ptr<TargetMachine> TM = CreateTargetMachine();
runLTOPasses(*Combined, *TM);
return runSplitCodegen(CreateTargetMachine);
}
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