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llvm-mirror/lib/CodeGen/ParallelCG.cpp
Chandler Carruth ae65e281f3 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00

99 lines
3.7 KiB
C++

//===-- ParallelCG.cpp ----------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines functions that can be used for parallel code generation.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/ParallelCG.h"
#include "llvm/Bitcode/BitcodeReader.h"
#include "llvm/Bitcode/BitcodeWriter.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/ThreadPool.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/Utils/SplitModule.h"
using namespace llvm;
static void codegen(Module *M, llvm::raw_pwrite_stream &OS,
function_ref<std::unique_ptr<TargetMachine>()> TMFactory,
TargetMachine::CodeGenFileType FileType) {
std::unique_ptr<TargetMachine> TM = TMFactory();
legacy::PassManager CodeGenPasses;
if (TM->addPassesToEmitFile(CodeGenPasses, OS, nullptr, FileType))
report_fatal_error("Failed to setup codegen");
CodeGenPasses.run(*M);
}
std::unique_ptr<Module> llvm::splitCodeGen(
std::unique_ptr<Module> M, ArrayRef<llvm::raw_pwrite_stream *> OSs,
ArrayRef<llvm::raw_pwrite_stream *> BCOSs,
const std::function<std::unique_ptr<TargetMachine>()> &TMFactory,
TargetMachine::CodeGenFileType FileType, bool PreserveLocals) {
assert(BCOSs.empty() || BCOSs.size() == OSs.size());
if (OSs.size() == 1) {
if (!BCOSs.empty())
WriteBitcodeToFile(*M, *BCOSs[0]);
codegen(M.get(), *OSs[0], TMFactory, FileType);
return M;
}
// Create ThreadPool in nested scope so that threads will be joined
// on destruction.
{
ThreadPool CodegenThreadPool(OSs.size());
int ThreadCount = 0;
SplitModule(
std::move(M), OSs.size(),
[&](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, BCOS);
if (!BCOSs.empty()) {
BCOSs[ThreadCount]->write(BC.begin(), BC.size());
BCOSs[ThreadCount]->flush();
}
llvm::raw_pwrite_stream *ThreadOS = OSs[ThreadCount++];
// Enqueue the task
CodegenThreadPool.async(
[TMFactory, FileType, ThreadOS](const SmallString<0> &BC) {
LLVMContext Ctx;
Expected<std::unique_ptr<Module>> MOrErr = parseBitcodeFile(
MemoryBufferRef(StringRef(BC.data(), BC.size()),
"<split-module>"),
Ctx);
if (!MOrErr)
report_fatal_error("Failed to read bitcode");
std::unique_ptr<Module> MPartInCtx = std::move(MOrErr.get());
codegen(MPartInCtx.get(), *ThreadOS, TMFactory, FileType);
},
// Pass BC using std::move to ensure that it get moved rather than
// copied into the thread's context.
std::move(BC));
},
PreserveLocals);
}
return {};
}