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llvm::splitCodeGen is a function that implements the core of parallel LTO code generation. It uses llvm::SplitModule to split the module into linkable partitions and spawning one code generation thread per partition. The function produces multiple object files which can be linked in the usual way. This has been threaded through to LTOCodeGenerator (and llvm-lto for testing purposes). Separate patches will add parallel LTO support to the gold plugin and lld. Differential Revision: http://reviews.llvm.org/D12260 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@246236 91177308-0d34-0410-b5e6-96231b3b80d8
96 lines
3.7 KiB
C++
96 lines
3.7 KiB
C++
//===-- ParallelCG.cpp ----------------------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines functions that can be used for parallel code generation.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/ParallelCG.h"
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#include "llvm/Bitcode/ReaderWriter.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/LegacyPassManager.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Support/ErrorOr.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include "llvm/Support/TargetRegistry.h"
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#include "llvm/Support/thread.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Transforms/Utils/SplitModule.h"
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using namespace llvm;
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static void codegen(Module *M, llvm::raw_pwrite_stream &OS,
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const Target *TheTarget, StringRef CPU, StringRef Features,
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const TargetOptions &Options, Reloc::Model RM,
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CodeModel::Model CM, CodeGenOpt::Level OL) {
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std::unique_ptr<TargetMachine> TM(TheTarget->createTargetMachine(
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M->getTargetTriple(), CPU, Features, Options, RM, CM, OL));
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legacy::PassManager CodeGenPasses;
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if (TM->addPassesToEmitFile(CodeGenPasses, OS,
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TargetMachine::CGFT_ObjectFile))
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report_fatal_error("Failed to setup codegen");
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CodeGenPasses.run(*M);
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}
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std::unique_ptr<Module>
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llvm::splitCodeGen(std::unique_ptr<Module> M,
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ArrayRef<llvm::raw_pwrite_stream *> OSs, StringRef CPU,
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StringRef Features, const TargetOptions &Options,
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Reloc::Model RM, CodeModel::Model CM, CodeGenOpt::Level OL) {
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StringRef TripleStr = M->getTargetTriple();
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std::string ErrMsg;
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const Target *TheTarget = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
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if (!TheTarget)
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report_fatal_error(Twine("Target not found: ") + ErrMsg);
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if (OSs.size() == 1) {
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codegen(M.get(), *OSs[0], TheTarget, CPU, Features, Options, RM, CM,
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OL);
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return M;
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}
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std::vector<std::thread> Threads;
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SplitModule(std::move(M), OSs.size(), [&](std::unique_ptr<Module> MPart) {
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// We want to clone the module in a new context to multi-thread the codegen.
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// We do it by serializing partition modules to bitcode (while still on the
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// main thread, in order to avoid data races) and spinning up new threads
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// which deserialize the partitions into separate contexts.
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// FIXME: Provide a more direct way to do this in LLVM.
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SmallVector<char, 0> BC;
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raw_svector_ostream BCOS(BC);
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WriteBitcodeToFile(MPart.get(), BCOS);
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llvm::raw_pwrite_stream *ThreadOS = OSs[Threads.size()];
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Threads.emplace_back(
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[TheTarget, CPU, Features, Options, RM, CM, OL,
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ThreadOS](const SmallVector<char, 0> &BC) {
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LLVMContext Ctx;
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ErrorOr<std::unique_ptr<Module>> MOrErr =
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parseBitcodeFile(MemoryBufferRef(StringRef(BC.data(), BC.size()),
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"<split-module>"),
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Ctx);
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if (!MOrErr)
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report_fatal_error("Failed to read bitcode");
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std::unique_ptr<Module> MPartInCtx = std::move(MOrErr.get());
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codegen(MPartInCtx.get(), *ThreadOS, TheTarget, CPU, Features,
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Options, RM, CM, OL);
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},
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// Pass BC using std::move to ensure that it get moved rather than
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// copied into the thread's context.
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std::move(BC));
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});
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for (std::thread &T : Threads)
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T.join();
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return {};
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}
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