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101 lines
3.8 KiB
101 lines
3.8 KiB
4 months ago
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//===-- ParallelCG.cpp ----------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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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/BitcodeReader.h"
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#include "llvm/Bitcode/BitcodeWriter.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/ThreadPool.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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function_ref<std::unique_ptr<TargetMachine>()> TMFactory,
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CodeGenFileType FileType) {
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std::unique_ptr<TargetMachine> TM = TMFactory();
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assert(TM && "Failed to create target machine!");
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legacy::PassManager CodeGenPasses;
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if (TM->addPassesToEmitFile(CodeGenPasses, OS, nullptr, FileType))
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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> llvm::splitCodeGen(
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std::unique_ptr<Module> M, ArrayRef<llvm::raw_pwrite_stream *> OSs,
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ArrayRef<llvm::raw_pwrite_stream *> BCOSs,
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const std::function<std::unique_ptr<TargetMachine>()> &TMFactory,
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CodeGenFileType FileType, bool PreserveLocals) {
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assert(BCOSs.empty() || BCOSs.size() == OSs.size());
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if (OSs.size() == 1) {
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if (!BCOSs.empty())
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WriteBitcodeToFile(*M, *BCOSs[0]);
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codegen(M.get(), *OSs[0], TMFactory, FileType);
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return M;
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}
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// Create ThreadPool in nested scope so that threads will be joined
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// on destruction.
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{
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ThreadPool CodegenThreadPool(hardware_concurrency(OSs.size()));
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int ThreadCount = 0;
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SplitModule(
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std::move(M), OSs.size(),
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[&](std::unique_ptr<Module> MPart) {
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// We want to clone the module in a new context to multi-thread the
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// codegen. We do it by serializing partition modules to bitcode
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// (while still on the main thread, in order to avoid data races) and
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// spinning up new threads which deserialize the partitions into
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// separate contexts.
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// FIXME: Provide a more direct way to do this in LLVM.
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SmallString<0> BC;
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raw_svector_ostream BCOS(BC);
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WriteBitcodeToFile(*MPart, BCOS);
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if (!BCOSs.empty()) {
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BCOSs[ThreadCount]->write(BC.begin(), BC.size());
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BCOSs[ThreadCount]->flush();
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}
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llvm::raw_pwrite_stream *ThreadOS = OSs[ThreadCount++];
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// Enqueue the task
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CodegenThreadPool.async(
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[TMFactory, FileType, ThreadOS](const SmallString<0> &BC) {
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LLVMContext Ctx;
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Expected<std::unique_ptr<Module>> MOrErr = parseBitcodeFile(
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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, TMFactory, FileType);
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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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PreserveLocals);
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}
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return {};
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}
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