1 //===-- ParallelCG.cpp ----------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file defines functions that can be used for parallel code generation. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "llvm/CodeGen/ParallelCG.h" 14 #include "llvm/Bitcode/BitcodeReader.h" 15 #include "llvm/Bitcode/BitcodeWriter.h" 16 #include "llvm/IR/LLVMContext.h" 17 #include "llvm/IR/LegacyPassManager.h" 18 #include "llvm/IR/Module.h" 19 #include "llvm/Support/ErrorOr.h" 20 #include "llvm/Support/MemoryBuffer.h" 21 #include "llvm/Support/ThreadPool.h" 22 #include "llvm/Target/TargetMachine.h" 23 #include "llvm/Transforms/Utils/SplitModule.h" 24 25 using namespace llvm; 26 27 static void codegen(Module *M, llvm::raw_pwrite_stream &OS, 28 function_ref<std::unique_ptr<TargetMachine>()> TMFactory, 29 CodeGenFileType FileType) { 30 std::unique_ptr<TargetMachine> TM = TMFactory(); 31 assert(TM && "Failed to create target machine!"); 32 33 legacy::PassManager CodeGenPasses; 34 if (TM->addPassesToEmitFile(CodeGenPasses, OS, nullptr, FileType)) 35 report_fatal_error("Failed to setup codegen"); 36 CodeGenPasses.run(*M); 37 } 38 39 void llvm::splitCodeGen( 40 Module &M, ArrayRef<llvm::raw_pwrite_stream *> OSs, 41 ArrayRef<llvm::raw_pwrite_stream *> BCOSs, 42 const std::function<std::unique_ptr<TargetMachine>()> &TMFactory, 43 CodeGenFileType FileType, bool PreserveLocals) { 44 assert(BCOSs.empty() || BCOSs.size() == OSs.size()); 45 46 if (OSs.size() == 1) { 47 if (!BCOSs.empty()) 48 WriteBitcodeToFile(M, *BCOSs[0]); 49 codegen(&M, *OSs[0], TMFactory, FileType); 50 return; 51 } 52 53 // Create ThreadPool in nested scope so that threads will be joined 54 // on destruction. 55 { 56 ThreadPool CodegenThreadPool(hardware_concurrency(OSs.size())); 57 int ThreadCount = 0; 58 59 SplitModule( 60 M, OSs.size(), 61 [&](std::unique_ptr<Module> MPart) { 62 // We want to clone the module in a new context to multi-thread the 63 // codegen. We do it by serializing partition modules to bitcode 64 // (while still on the main thread, in order to avoid data races) and 65 // spinning up new threads which deserialize the partitions into 66 // separate contexts. 67 // FIXME: Provide a more direct way to do this in LLVM. 68 SmallString<0> BC; 69 raw_svector_ostream BCOS(BC); 70 WriteBitcodeToFile(*MPart, BCOS); 71 72 if (!BCOSs.empty()) { 73 BCOSs[ThreadCount]->write(BC.begin(), BC.size()); 74 BCOSs[ThreadCount]->flush(); 75 } 76 77 llvm::raw_pwrite_stream *ThreadOS = OSs[ThreadCount++]; 78 // Enqueue the task 79 CodegenThreadPool.async( 80 [TMFactory, FileType, ThreadOS](const SmallString<0> &BC) { 81 LLVMContext Ctx; 82 Expected<std::unique_ptr<Module>> MOrErr = parseBitcodeFile( 83 MemoryBufferRef(StringRef(BC.data(), BC.size()), 84 "<split-module>"), 85 Ctx); 86 if (!MOrErr) 87 report_fatal_error("Failed to read bitcode"); 88 std::unique_ptr<Module> MPartInCtx = std::move(MOrErr.get()); 89 90 codegen(MPartInCtx.get(), *ThreadOS, TMFactory, FileType); 91 }, 92 // Pass BC using std::move to ensure that it get moved rather than 93 // copied into the thread's context. 94 std::move(BC)); 95 }, 96 PreserveLocals); 97 } 98 } 99