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[llvm-complete.git] / lib / CodeGen / ParallelCG.cpp
blobbc3f2a6e9b5a21ea61a9153fe1d44fcfb81435ae
1 //===-- ParallelCG.cpp ----------------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines functions that can be used for parallel code generation.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/CodeGen/ParallelCG.h"
15 #include "llvm/Bitcode/BitcodeReader.h"
16 #include "llvm/Bitcode/BitcodeWriter.h"
17 #include "llvm/IR/LLVMContext.h"
18 #include "llvm/IR/LegacyPassManager.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/Support/ErrorOr.h"
21 #include "llvm/Support/MemoryBuffer.h"
22 #include "llvm/Support/ThreadPool.h"
23 #include "llvm/Target/TargetMachine.h"
24 #include "llvm/Transforms/Utils/SplitModule.h"
26 using namespace llvm;
28 static void codegen(Module *M, llvm::raw_pwrite_stream &OS,
29 function_ref<std::unique_ptr<TargetMachine>()> TMFactory,
30 TargetMachine::CodeGenFileType FileType) {
31 std::unique_ptr<TargetMachine> TM = TMFactory();
32 legacy::PassManager CodeGenPasses;
33 if (TM->addPassesToEmitFile(CodeGenPasses, OS, nullptr, FileType))
34 report_fatal_error("Failed to setup codegen");
35 CodeGenPasses.run(*M);
38 std::unique_ptr<Module> llvm::splitCodeGen(
39 std::unique_ptr<Module> M, ArrayRef<llvm::raw_pwrite_stream *> OSs,
40 ArrayRef<llvm::raw_pwrite_stream *> BCOSs,
41 const std::function<std::unique_ptr<TargetMachine>()> &TMFactory,
42 TargetMachine::CodeGenFileType FileType, bool PreserveLocals) {
43 assert(BCOSs.empty() || BCOSs.size() == OSs.size());
45 if (OSs.size() == 1) {
46 if (!BCOSs.empty())
47 WriteBitcodeToFile(*M, *BCOSs[0]);
48 codegen(M.get(), *OSs[0], TMFactory, FileType);
49 return M;
52 // Create ThreadPool in nested scope so that threads will be joined
53 // on destruction.
55 ThreadPool CodegenThreadPool(OSs.size());
56 int ThreadCount = 0;
58 SplitModule(
59 std::move(M), OSs.size(),
60 [&](std::unique_ptr<Module> MPart) {
61 // We want to clone the module in a new context to multi-thread the
62 // codegen. We do it by serializing partition modules to bitcode
63 // (while still on the main thread, in order to avoid data races) and
64 // spinning up new threads which deserialize the partitions into
65 // separate contexts.
66 // FIXME: Provide a more direct way to do this in LLVM.
67 SmallString<0> BC;
68 raw_svector_ostream BCOS(BC);
69 WriteBitcodeToFile(*MPart, BCOS);
71 if (!BCOSs.empty()) {
72 BCOSs[ThreadCount]->write(BC.begin(), BC.size());
73 BCOSs[ThreadCount]->flush();
76 llvm::raw_pwrite_stream *ThreadOS = OSs[ThreadCount++];
77 // Enqueue the task
78 CodegenThreadPool.async(
79 [TMFactory, FileType, ThreadOS](const SmallString<0> &BC) {
80 LLVMContext Ctx;
81 Expected<std::unique_ptr<Module>> MOrErr = parseBitcodeFile(
82 MemoryBufferRef(StringRef(BC.data(), BC.size()),
83 "<split-module>"),
84 Ctx);
85 if (!MOrErr)
86 report_fatal_error("Failed to read bitcode");
87 std::unique_ptr<Module> MPartInCtx = std::move(MOrErr.get());
89 codegen(MPartInCtx.get(), *ThreadOS, TMFactory, FileType);
91 // Pass BC using std::move to ensure that it get moved rather than
92 // copied into the thread's context.
93 std::move(BC));
95 PreserveLocals);
98 return {};