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.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "llvm/CodeGen/ParallelCG.h"
15 #include "llvm/Bitcode/ReaderWriter.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/TargetRegistry.h"
22 #include "llvm/Support/thread.h"
23 #include "llvm/Target/TargetMachine.h"
24 #include "llvm/Transforms/Utils/SplitModule.h"
25
26 using namespace llvm;
27
codegen(Module * M,llvm::raw_pwrite_stream & OS,const Target * TheTarget,StringRef CPU,StringRef Features,const TargetOptions & Options,Reloc::Model RM,CodeModel::Model CM,CodeGenOpt::Level OL,TargetMachine::CodeGenFileType FileType)28 static void codegen(Module *M, llvm::raw_pwrite_stream &OS,
29 const Target *TheTarget, StringRef CPU, StringRef Features,
30 const TargetOptions &Options, Reloc::Model RM,
31 CodeModel::Model CM, CodeGenOpt::Level OL,
32 TargetMachine::CodeGenFileType FileType) {
33 std::unique_ptr<TargetMachine> TM(TheTarget->createTargetMachine(
34 M->getTargetTriple(), CPU, Features, Options, RM, CM, OL));
35
36 legacy::PassManager CodeGenPasses;
37 if (TM->addPassesToEmitFile(CodeGenPasses, OS, FileType))
38 report_fatal_error("Failed to setup codegen");
39 CodeGenPasses.run(*M);
40 }
41
42 std::unique_ptr<Module>
splitCodeGen(std::unique_ptr<Module> M,ArrayRef<llvm::raw_pwrite_stream * > OSs,StringRef CPU,StringRef Features,const TargetOptions & Options,Reloc::Model RM,CodeModel::Model CM,CodeGenOpt::Level OL,TargetMachine::CodeGenFileType FileType)43 llvm::splitCodeGen(std::unique_ptr<Module> M,
44 ArrayRef<llvm::raw_pwrite_stream *> OSs, StringRef CPU,
45 StringRef Features, const TargetOptions &Options,
46 Reloc::Model RM, CodeModel::Model CM, CodeGenOpt::Level OL,
47 TargetMachine::CodeGenFileType FileType) {
48 StringRef TripleStr = M->getTargetTriple();
49 std::string ErrMsg;
50 const Target *TheTarget = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
51 if (!TheTarget)
52 report_fatal_error(Twine("Target not found: ") + ErrMsg);
53
54 if (OSs.size() == 1) {
55 codegen(M.get(), *OSs[0], TheTarget, CPU, Features, Options, RM, CM,
56 OL, FileType);
57 return M;
58 }
59
60 std::vector<thread> Threads;
61 SplitModule(std::move(M), OSs.size(), [&](std::unique_ptr<Module> MPart) {
62 // We want to clone the module in a new context to multi-thread the codegen.
63 // We do it by serializing partition modules to bitcode (while still on the
64 // main thread, in order to avoid data races) and spinning up new threads
65 // which deserialize the partitions into separate contexts.
66 // FIXME: Provide a more direct way to do this in LLVM.
67 SmallVector<char, 0> BC;
68 raw_svector_ostream BCOS(BC);
69 WriteBitcodeToFile(MPart.get(), BCOS);
70
71 llvm::raw_pwrite_stream *ThreadOS = OSs[Threads.size()];
72 Threads.emplace_back(
73 [TheTarget, CPU, Features, Options, RM, CM, OL, FileType,
74 ThreadOS](const SmallVector<char, 0> &BC) {
75 LLVMContext Ctx;
76 ErrorOr<std::unique_ptr<Module>> MOrErr =
77 parseBitcodeFile(MemoryBufferRef(StringRef(BC.data(), BC.size()),
78 "<split-module>"),
79 Ctx);
80 if (!MOrErr)
81 report_fatal_error("Failed to read bitcode");
82 std::unique_ptr<Module> MPartInCtx = std::move(MOrErr.get());
83
84 codegen(MPartInCtx.get(), *ThreadOS, TheTarget, CPU, Features,
85 Options, RM, CM, OL, FileType);
86 },
87 // Pass BC using std::move to ensure that it get moved rather than
88 // copied into the thread's context.
89 std::move(BC));
90 });
91
92 for (thread &T : Threads)
93 T.join();
94
95 return {};
96 }
97