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llvm-project/llvm/lib/LTO/LTOBackend.cpp

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//===-LTOBackend.cpp - LLVM Link Time Optimizer Backend -------------------===//
//
// 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 "backend" phase of LTO, i.e. it performs
// optimization and code generation on a loaded module. It is generally used
// internally by the LTO class but can also be used independently, for example
// to implement a standalone ThinLTO backend.
//
//===----------------------------------------------------------------------===//
#include "llvm/LTO/LTOBackend.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/LTO/LTO.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/ThreadPool.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#include "llvm/Transforms/Utils/FunctionImportUtils.h"
#include "llvm/Transforms/Utils/SplitModule.h"
using namespace llvm;
using namespace lto;
Error Config::addSaveTemps(std::string OutputFileName,
bool UseInputModulePath) {
ShouldDiscardValueNames = false;
std::error_code EC;
ResolutionFile = llvm::make_unique<raw_fd_ostream>(
OutputFileName + "resolution.txt", EC, sys::fs::OpenFlags::F_Text);
if (EC)
return errorCodeToError(EC);
auto setHook = [&](std::string PathSuffix, ModuleHookFn &Hook) {
// Keep track of the hook provided by the linker, which also needs to run.
ModuleHookFn LinkerHook = Hook;
Hook = [=](unsigned Task, Module &M) {
// If the linker's hook returned false, we need to pass that result
// through.
if (LinkerHook && !LinkerHook(Task, M))
return false;
std::string PathPrefix;
// If this is the combined module (not a ThinLTO backend compile) or the
// user hasn't requested using the input module's path, emit to a file
// named from the provided OutputFileName with the Task ID appended.
if (M.getModuleIdentifier() == "ld-temp.o" || !UseInputModulePath) {
PathPrefix = OutputFileName + utostr(Task);
} else
PathPrefix = M.getModuleIdentifier();
std::string Path = PathPrefix + "." + PathSuffix + ".bc";
std::error_code EC;
raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
if (EC) {
// Because -save-temps is a debugging feature, we report the error
// directly and exit.
llvm::errs() << "failed to open " << Path << ": " << EC.message()
<< '\n';
exit(1);
}
WriteBitcodeToFile(&M, OS, /*ShouldPreserveUseListOrder=*/false);
return true;
};
};
setHook("0.preopt", PreOptModuleHook);
setHook("1.promote", PostPromoteModuleHook);
setHook("2.internalize", PostInternalizeModuleHook);
setHook("3.import", PostImportModuleHook);
setHook("4.opt", PostOptModuleHook);
setHook("5.precodegen", PreCodeGenModuleHook);
CombinedIndexHook = [=](const ModuleSummaryIndex &Index) {
std::string Path = OutputFileName + "index.bc";
std::error_code EC;
raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
if (EC) {
// Because -save-temps is a debugging feature, we report the error
// directly and exit.
llvm::errs() << "failed to open " << Path << ": " << EC.message() << '\n';
exit(1);
}
WriteIndexToFile(Index, OS);
return true;
};
return Error();
}
namespace {
std::unique_ptr<TargetMachine>
createTargetMachine(Config &C, StringRef TheTriple, const Target *TheTarget) {
SubtargetFeatures Features;
Features.getDefaultSubtargetFeatures(Triple(TheTriple));
for (const std::string &A : C.MAttrs)
Features.AddFeature(A);
return std::unique_ptr<TargetMachine>(TheTarget->createTargetMachine(
TheTriple, C.CPU, Features.getString(), C.Options, C.RelocModel,
C.CodeModel, C.CGOptLevel));
}
bool opt(Config &C, TargetMachine *TM, unsigned Task, Module &M,
bool IsThinLto) {
M.setDataLayout(TM->createDataLayout());
legacy::PassManager passes;
passes.add(createTargetTransformInfoWrapperPass(TM->getTargetIRAnalysis()));
PassManagerBuilder PMB;
PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM->getTargetTriple()));
PMB.Inliner = createFunctionInliningPass();
// Unconditionally verify input since it is not verified before this
// point and has unknown origin.
PMB.VerifyInput = true;
PMB.VerifyOutput = !C.DisableVerify;
PMB.LoopVectorize = true;
PMB.SLPVectorize = true;
PMB.OptLevel = C.OptLevel;
if (IsThinLto)
PMB.populateThinLTOPassManager(passes);
else
PMB.populateLTOPassManager(passes);
passes.run(M);
if (C.PostOptModuleHook && !C.PostOptModuleHook(Task, M))
return false;
return true;
}
void codegen(Config &C, TargetMachine *TM, AddOutputFn AddOutput, unsigned Task,
Module &M) {
if (C.PreCodeGenModuleHook && !C.PreCodeGenModuleHook(Task, M))
return;
auto Output = AddOutput(Task);
std::unique_ptr<raw_pwrite_stream> OS = Output->getStream();
legacy::PassManager CodeGenPasses;
if (TM->addPassesToEmitFile(CodeGenPasses, *OS,
TargetMachine::CGFT_ObjectFile))
report_fatal_error("Failed to setup codegen");
CodeGenPasses.run(M);
}
void splitCodeGen(Config &C, TargetMachine *TM, AddOutputFn AddOutput,
unsigned ParallelCodeGenParallelismLevel,
std::unique_ptr<Module> M) {
ThreadPool CodegenThreadPool(ParallelCodeGenParallelismLevel);
unsigned ThreadCount = 0;
const Target *T = &TM->getTarget();
SplitModule(
std::move(M), ParallelCodeGenParallelismLevel,
[&](std::unique_ptr<Module> MPart) {
// We want to clone the module in a new context to multi-thread the
// codegen. We do it by serializing partition modules to bitcode
// (while still on the main thread, in order to avoid data races) and
// spinning up new threads which deserialize the partitions into
// separate contexts.
// FIXME: Provide a more direct way to do this in LLVM.
SmallString<0> BC;
raw_svector_ostream BCOS(BC);
WriteBitcodeToFile(MPart.get(), BCOS);
// Enqueue the task
CodegenThreadPool.async(
[&](const SmallString<0> &BC, unsigned ThreadId) {
LTOLLVMContext Ctx(C);
ErrorOr<std::unique_ptr<Module>> MOrErr = parseBitcodeFile(
MemoryBufferRef(StringRef(BC.data(), BC.size()), "ld-temp.o"),
Ctx);
if (!MOrErr)
report_fatal_error("Failed to read bitcode");
std::unique_ptr<Module> MPartInCtx = std::move(MOrErr.get());
std::unique_ptr<TargetMachine> TM =
createTargetMachine(C, MPartInCtx->getTargetTriple(), T);
codegen(C, TM.get(), AddOutput, ThreadId, *MPartInCtx);
},
// Pass BC using std::move to ensure that it get moved rather than
// copied into the thread's context.
std::move(BC), ThreadCount++);
},
false);
}
Expected<const Target *> initAndLookupTarget(Config &C, Module &M) {
if (!C.OverrideTriple.empty())
M.setTargetTriple(C.OverrideTriple);
else if (M.getTargetTriple().empty())
M.setTargetTriple(C.DefaultTriple);
std::string Msg;
const Target *T = TargetRegistry::lookupTarget(M.getTargetTriple(), Msg);
if (!T)
return make_error<StringError>(Msg, inconvertibleErrorCode());
return T;
}
}
Error lto::backend(Config &C, AddOutputFn AddOutput,
unsigned ParallelCodeGenParallelismLevel,
std::unique_ptr<Module> M) {
Expected<const Target *> TOrErr = initAndLookupTarget(C, *M);
if (!TOrErr)
return TOrErr.takeError();
std::unique_ptr<TargetMachine> TM =
createTargetMachine(C, M->getTargetTriple(), *TOrErr);
if (!opt(C, TM.get(), 0, *M, /*IsThinLto=*/false))
return Error();
if (ParallelCodeGenParallelismLevel == 1)
codegen(C, TM.get(), AddOutput, 0, *M);
else
splitCodeGen(C, TM.get(), AddOutput, ParallelCodeGenParallelismLevel,
std::move(M));
return Error();
}
Error lto::thinBackend(Config &Conf, unsigned Task, AddOutputFn AddOutput,
Module &Mod, ModuleSummaryIndex &CombinedIndex,
const FunctionImporter::ImportMapTy &ImportList,
const GVSummaryMapTy &DefinedGlobals,
MapVector<StringRef, MemoryBufferRef> &ModuleMap) {
Expected<const Target *> TOrErr = initAndLookupTarget(Conf, Mod);
if (!TOrErr)
return TOrErr.takeError();
std::unique_ptr<TargetMachine> TM =
createTargetMachine(Conf, Mod.getTargetTriple(), *TOrErr);
if (Conf.PreOptModuleHook && !Conf.PreOptModuleHook(Task, Mod))
return Error();
renameModuleForThinLTO(Mod, CombinedIndex);
thinLTOResolveWeakForLinkerModule(Mod, DefinedGlobals);
if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod))
return Error();
if (!DefinedGlobals.empty())
thinLTOInternalizeModule(Mod, DefinedGlobals);
if (Conf.PostInternalizeModuleHook &&
!Conf.PostInternalizeModuleHook(Task, Mod))
return Error();
auto ModuleLoader = [&](StringRef Identifier) {
return std::move(getLazyBitcodeModule(MemoryBuffer::getMemBuffer(
ModuleMap[Identifier], false),
Mod.getContext(),
/*ShouldLazyLoadMetadata=*/true)
.get());
};
FunctionImporter Importer(CombinedIndex, ModuleLoader);
Importer.importFunctions(Mod, ImportList);
if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod))
return Error();
if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLto=*/true))
return Error();
codegen(Conf, TM.get(), AddOutput, Task, Mod);
return Error();
}
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