1 //===-LTOBackend.cpp - LLVM Link Time Optimizer Backend -------------------===//
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 implements the "backend" phase of LTO, i.e. it performs
10 // optimization and code generation on a loaded module. It is generally used
11 // internally by the LTO class but can also be used independently, for example
12 // to implement a standalone ThinLTO backend.
13 //
14 //===----------------------------------------------------------------------===//
15
16 #include "llvm/LTO/LTOBackend.h"
17 #include "llvm/Analysis/AliasAnalysis.h"
18 #include "llvm/Analysis/CGSCCPassManager.h"
19 #include "llvm/Analysis/ModuleSummaryAnalysis.h"
20 #include "llvm/Analysis/TargetLibraryInfo.h"
21 #include "llvm/Analysis/TargetTransformInfo.h"
22 #include "llvm/Bitcode/BitcodeReader.h"
23 #include "llvm/Bitcode/BitcodeWriter.h"
24 #include "llvm/IR/LLVMRemarkStreamer.h"
25 #include "llvm/IR/LegacyPassManager.h"
26 #include "llvm/IR/PassManager.h"
27 #include "llvm/IR/Verifier.h"
28 #include "llvm/LTO/LTO.h"
29 #include "llvm/MC/SubtargetFeature.h"
30 #include "llvm/MC/TargetRegistry.h"
31 #include "llvm/Object/ModuleSymbolTable.h"
32 #include "llvm/Passes/PassBuilder.h"
33 #include "llvm/Passes/PassPlugin.h"
34 #include "llvm/Passes/StandardInstrumentations.h"
35 #include "llvm/Support/Error.h"
36 #include "llvm/Support/FileSystem.h"
37 #include "llvm/Support/MemoryBuffer.h"
38 #include "llvm/Support/Path.h"
39 #include "llvm/Support/Program.h"
40 #include "llvm/Support/SmallVectorMemoryBuffer.h"
41 #include "llvm/Support/ThreadPool.h"
42 #include "llvm/Support/raw_ostream.h"
43 #include "llvm/Target/TargetMachine.h"
44 #include "llvm/Transforms/IPO.h"
45 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
46 #include "llvm/Transforms/Scalar/LoopPassManager.h"
47 #include "llvm/Transforms/Utils/FunctionImportUtils.h"
48 #include "llvm/Transforms/Utils/SplitModule.h"
49
50 using namespace llvm;
51 using namespace lto;
52
53 #define DEBUG_TYPE "lto-backend"
54
55 enum class LTOBitcodeEmbedding {
56 DoNotEmbed = 0,
57 EmbedOptimized = 1,
58 EmbedPostMergePreOptimized = 2
59 };
60
61 static cl::opt<LTOBitcodeEmbedding> EmbedBitcode(
62 "lto-embed-bitcode", cl::init(LTOBitcodeEmbedding::DoNotEmbed),
63 cl::values(clEnumValN(LTOBitcodeEmbedding::DoNotEmbed, "none",
64 "Do not embed"),
65 clEnumValN(LTOBitcodeEmbedding::EmbedOptimized, "optimized",
66 "Embed after all optimization passes"),
67 clEnumValN(LTOBitcodeEmbedding::EmbedPostMergePreOptimized,
68 "post-merge-pre-opt",
69 "Embed post merge, but before optimizations")),
70 cl::desc("Embed LLVM bitcode in object files produced by LTO"));
71
72 static cl::opt<bool> ThinLTOAssumeMerged(
73 "thinlto-assume-merged", cl::init(false),
74 cl::desc("Assume the input has already undergone ThinLTO function "
75 "importing and the other pre-optimization pipeline changes."));
76
77 namespace llvm {
78 extern cl::opt<bool> NoPGOWarnMismatch;
79 }
80
reportOpenError(StringRef Path,Twine Msg)81 [[noreturn]] static void reportOpenError(StringRef Path, Twine Msg) {
82 errs() << "failed to open " << Path << ": " << Msg << '\n';
83 errs().flush();
84 exit(1);
85 }
86
addSaveTemps(std::string OutputFileName,bool UseInputModulePath)87 Error Config::addSaveTemps(std::string OutputFileName,
88 bool UseInputModulePath) {
89 ShouldDiscardValueNames = false;
90
91 std::error_code EC;
92 ResolutionFile =
93 std::make_unique<raw_fd_ostream>(OutputFileName + "resolution.txt", EC,
94 sys::fs::OpenFlags::OF_TextWithCRLF);
95 if (EC) {
96 ResolutionFile.reset();
97 return errorCodeToError(EC);
98 }
99
100 auto setHook = [&](std::string PathSuffix, ModuleHookFn &Hook) {
101 // Keep track of the hook provided by the linker, which also needs to run.
102 ModuleHookFn LinkerHook = Hook;
103 Hook = [=](unsigned Task, const Module &M) {
104 // If the linker's hook returned false, we need to pass that result
105 // through.
106 if (LinkerHook && !LinkerHook(Task, M))
107 return false;
108
109 std::string PathPrefix;
110 // If this is the combined module (not a ThinLTO backend compile) or the
111 // user hasn't requested using the input module's path, emit to a file
112 // named from the provided OutputFileName with the Task ID appended.
113 if (M.getModuleIdentifier() == "ld-temp.o" || !UseInputModulePath) {
114 PathPrefix = OutputFileName;
115 if (Task != (unsigned)-1)
116 PathPrefix += utostr(Task) + ".";
117 } else
118 PathPrefix = M.getModuleIdentifier() + ".";
119 std::string Path = PathPrefix + PathSuffix + ".bc";
120 std::error_code EC;
121 raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::OF_None);
122 // Because -save-temps is a debugging feature, we report the error
123 // directly and exit.
124 if (EC)
125 reportOpenError(Path, EC.message());
126 WriteBitcodeToFile(M, OS, /*ShouldPreserveUseListOrder=*/false);
127 return true;
128 };
129 };
130
131 setHook("0.preopt", PreOptModuleHook);
132 setHook("1.promote", PostPromoteModuleHook);
133 setHook("2.internalize", PostInternalizeModuleHook);
134 setHook("3.import", PostImportModuleHook);
135 setHook("4.opt", PostOptModuleHook);
136 setHook("5.precodegen", PreCodeGenModuleHook);
137
138 CombinedIndexHook =
139 [=](const ModuleSummaryIndex &Index,
140 const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) {
141 std::string Path = OutputFileName + "index.bc";
142 std::error_code EC;
143 raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::OF_None);
144 // Because -save-temps is a debugging feature, we report the error
145 // directly and exit.
146 if (EC)
147 reportOpenError(Path, EC.message());
148 WriteIndexToFile(Index, OS);
149
150 Path = OutputFileName + "index.dot";
151 raw_fd_ostream OSDot(Path, EC, sys::fs::OpenFlags::OF_None);
152 if (EC)
153 reportOpenError(Path, EC.message());
154 Index.exportToDot(OSDot, GUIDPreservedSymbols);
155 return true;
156 };
157
158 return Error::success();
159 }
160
161 #define HANDLE_EXTENSION(Ext) \
162 llvm::PassPluginLibraryInfo get##Ext##PluginInfo();
163 #include "llvm/Support/Extension.def"
164
RegisterPassPlugins(ArrayRef<std::string> PassPlugins,PassBuilder & PB)165 static void RegisterPassPlugins(ArrayRef<std::string> PassPlugins,
166 PassBuilder &PB) {
167 #define HANDLE_EXTENSION(Ext) \
168 get##Ext##PluginInfo().RegisterPassBuilderCallbacks(PB);
169 #include "llvm/Support/Extension.def"
170
171 // Load requested pass plugins and let them register pass builder callbacks
172 for (auto &PluginFN : PassPlugins) {
173 auto PassPlugin = PassPlugin::Load(PluginFN);
174 if (!PassPlugin) {
175 errs() << "Failed to load passes from '" << PluginFN
176 << "'. Request ignored.\n";
177 continue;
178 }
179
180 PassPlugin->registerPassBuilderCallbacks(PB);
181 }
182 }
183
184 static std::unique_ptr<TargetMachine>
createTargetMachine(const Config & Conf,const Target * TheTarget,Module & M)185 createTargetMachine(const Config &Conf, const Target *TheTarget, Module &M) {
186 StringRef TheTriple = M.getTargetTriple();
187 SubtargetFeatures Features;
188 Features.getDefaultSubtargetFeatures(Triple(TheTriple));
189 for (const std::string &A : Conf.MAttrs)
190 Features.AddFeature(A);
191
192 Optional<Reloc::Model> RelocModel = None;
193 if (Conf.RelocModel)
194 RelocModel = *Conf.RelocModel;
195 else if (M.getModuleFlag("PIC Level"))
196 RelocModel =
197 M.getPICLevel() == PICLevel::NotPIC ? Reloc::Static : Reloc::PIC_;
198
199 Optional<CodeModel::Model> CodeModel;
200 if (Conf.CodeModel)
201 CodeModel = *Conf.CodeModel;
202 else
203 CodeModel = M.getCodeModel();
204
205 std::unique_ptr<TargetMachine> TM(TheTarget->createTargetMachine(
206 TheTriple, Conf.CPU, Features.getString(), Conf.Options, RelocModel,
207 CodeModel, Conf.CGOptLevel));
208 assert(TM && "Failed to create target machine");
209 return TM;
210 }
211
runNewPMPasses(const Config & Conf,Module & Mod,TargetMachine * TM,unsigned OptLevel,bool IsThinLTO,ModuleSummaryIndex * ExportSummary,const ModuleSummaryIndex * ImportSummary)212 static void runNewPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
213 unsigned OptLevel, bool IsThinLTO,
214 ModuleSummaryIndex *ExportSummary,
215 const ModuleSummaryIndex *ImportSummary) {
216 Optional<PGOOptions> PGOOpt;
217 if (!Conf.SampleProfile.empty())
218 PGOOpt = PGOOptions(Conf.SampleProfile, "", Conf.ProfileRemapping,
219 PGOOptions::SampleUse, PGOOptions::NoCSAction, true);
220 else if (Conf.RunCSIRInstr) {
221 PGOOpt = PGOOptions("", Conf.CSIRProfile, Conf.ProfileRemapping,
222 PGOOptions::IRUse, PGOOptions::CSIRInstr,
223 Conf.AddFSDiscriminator);
224 } else if (!Conf.CSIRProfile.empty()) {
225 PGOOpt = PGOOptions(Conf.CSIRProfile, "", Conf.ProfileRemapping,
226 PGOOptions::IRUse, PGOOptions::CSIRUse,
227 Conf.AddFSDiscriminator);
228 NoPGOWarnMismatch = !Conf.PGOWarnMismatch;
229 } else if (Conf.AddFSDiscriminator) {
230 PGOOpt = PGOOptions("", "", "", PGOOptions::NoAction,
231 PGOOptions::NoCSAction, true);
232 }
233 if (TM)
234 TM->setPGOOption(PGOOpt);
235
236 LoopAnalysisManager LAM;
237 FunctionAnalysisManager FAM;
238 CGSCCAnalysisManager CGAM;
239 ModuleAnalysisManager MAM;
240
241 PassInstrumentationCallbacks PIC;
242 StandardInstrumentations SI(Conf.DebugPassManager);
243 SI.registerCallbacks(PIC, &FAM);
244 PassBuilder PB(TM, Conf.PTO, PGOOpt, &PIC);
245
246 RegisterPassPlugins(Conf.PassPlugins, PB);
247
248 std::unique_ptr<TargetLibraryInfoImpl> TLII(
249 new TargetLibraryInfoImpl(Triple(TM->getTargetTriple())));
250 if (Conf.Freestanding)
251 TLII->disableAllFunctions();
252 FAM.registerPass([&] { return TargetLibraryAnalysis(*TLII); });
253
254 AAManager AA;
255 // Parse a custom AA pipeline if asked to.
256 if (!Conf.AAPipeline.empty()) {
257 if (auto Err = PB.parseAAPipeline(AA, Conf.AAPipeline)) {
258 report_fatal_error(Twine("unable to parse AA pipeline description '") +
259 Conf.AAPipeline + "': " + toString(std::move(Err)));
260 }
261 } else {
262 AA = PB.buildDefaultAAPipeline();
263 }
264 // Register the AA manager first so that our version is the one used.
265 FAM.registerPass([&] { return std::move(AA); });
266
267 // Register all the basic analyses with the managers.
268 PB.registerModuleAnalyses(MAM);
269 PB.registerCGSCCAnalyses(CGAM);
270 PB.registerFunctionAnalyses(FAM);
271 PB.registerLoopAnalyses(LAM);
272 PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
273
274 ModulePassManager MPM;
275
276 if (!Conf.DisableVerify)
277 MPM.addPass(VerifierPass());
278
279 OptimizationLevel OL;
280
281 switch (OptLevel) {
282 default:
283 llvm_unreachable("Invalid optimization level");
284 case 0:
285 OL = OptimizationLevel::O0;
286 break;
287 case 1:
288 OL = OptimizationLevel::O1;
289 break;
290 case 2:
291 OL = OptimizationLevel::O2;
292 break;
293 case 3:
294 OL = OptimizationLevel::O3;
295 break;
296 }
297
298 // Parse a custom pipeline if asked to.
299 if (!Conf.OptPipeline.empty()) {
300 if (auto Err = PB.parsePassPipeline(MPM, Conf.OptPipeline)) {
301 report_fatal_error(Twine("unable to parse pass pipeline description '") +
302 Conf.OptPipeline + "': " + toString(std::move(Err)));
303 }
304 } else if (IsThinLTO) {
305 MPM.addPass(PB.buildThinLTODefaultPipeline(OL, ImportSummary));
306 } else {
307 MPM.addPass(PB.buildLTODefaultPipeline(OL, ExportSummary));
308 }
309
310 if (!Conf.DisableVerify)
311 MPM.addPass(VerifierPass());
312
313 MPM.run(Mod, MAM);
314 }
315
runOldPMPasses(const Config & Conf,Module & Mod,TargetMachine * TM,bool IsThinLTO,ModuleSummaryIndex * ExportSummary,const ModuleSummaryIndex * ImportSummary)316 static void runOldPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
317 bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
318 const ModuleSummaryIndex *ImportSummary) {
319 legacy::PassManager passes;
320 passes.add(createTargetTransformInfoWrapperPass(TM->getTargetIRAnalysis()));
321
322 PassManagerBuilder PMB;
323 PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM->getTargetTriple()));
324 if (Conf.Freestanding)
325 PMB.LibraryInfo->disableAllFunctions();
326 PMB.Inliner = createFunctionInliningPass();
327 PMB.ExportSummary = ExportSummary;
328 PMB.ImportSummary = ImportSummary;
329 // Unconditionally verify input since it is not verified before this
330 // point and has unknown origin.
331 PMB.VerifyInput = true;
332 PMB.VerifyOutput = !Conf.DisableVerify;
333 PMB.LoopVectorize = true;
334 PMB.SLPVectorize = true;
335 PMB.OptLevel = Conf.OptLevel;
336 PMB.PGOSampleUse = Conf.SampleProfile;
337 PMB.EnablePGOCSInstrGen = Conf.RunCSIRInstr;
338 if (!Conf.RunCSIRInstr && !Conf.CSIRProfile.empty()) {
339 PMB.EnablePGOCSInstrUse = true;
340 PMB.PGOInstrUse = Conf.CSIRProfile;
341 }
342 if (IsThinLTO)
343 PMB.populateThinLTOPassManager(passes);
344 else
345 PMB.populateLTOPassManager(passes);
346 passes.run(Mod);
347 }
348
opt(const Config & Conf,TargetMachine * TM,unsigned Task,Module & Mod,bool IsThinLTO,ModuleSummaryIndex * ExportSummary,const ModuleSummaryIndex * ImportSummary,const std::vector<uint8_t> & CmdArgs)349 bool lto::opt(const Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
350 bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
351 const ModuleSummaryIndex *ImportSummary,
352 const std::vector<uint8_t> &CmdArgs) {
353 if (EmbedBitcode == LTOBitcodeEmbedding::EmbedPostMergePreOptimized) {
354 // FIXME: the motivation for capturing post-merge bitcode and command line
355 // is replicating the compilation environment from bitcode, without needing
356 // to understand the dependencies (the functions to be imported). This
357 // assumes a clang - based invocation, case in which we have the command
358 // line.
359 // It's not very clear how the above motivation would map in the
360 // linker-based case, so we currently don't plumb the command line args in
361 // that case.
362 if (CmdArgs.empty())
363 LLVM_DEBUG(
364 dbgs() << "Post-(Thin)LTO merge bitcode embedding was requested, but "
365 "command line arguments are not available");
366 llvm::EmbedBitcodeInModule(Mod, llvm::MemoryBufferRef(),
367 /*EmbedBitcode*/ true, /*EmbedCmdline*/ true,
368 /*Cmdline*/ CmdArgs);
369 }
370 // FIXME: Plumb the combined index into the new pass manager.
371 if (Conf.UseNewPM || !Conf.OptPipeline.empty()) {
372 runNewPMPasses(Conf, Mod, TM, Conf.OptLevel, IsThinLTO, ExportSummary,
373 ImportSummary);
374 } else {
375 runOldPMPasses(Conf, Mod, TM, IsThinLTO, ExportSummary, ImportSummary);
376 }
377 return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod);
378 }
379
codegen(const Config & Conf,TargetMachine * TM,AddStreamFn AddStream,unsigned Task,Module & Mod,const ModuleSummaryIndex & CombinedIndex)380 static void codegen(const Config &Conf, TargetMachine *TM,
381 AddStreamFn AddStream, unsigned Task, Module &Mod,
382 const ModuleSummaryIndex &CombinedIndex) {
383 if (Conf.PreCodeGenModuleHook && !Conf.PreCodeGenModuleHook(Task, Mod))
384 return;
385
386 if (EmbedBitcode == LTOBitcodeEmbedding::EmbedOptimized)
387 llvm::EmbedBitcodeInModule(Mod, llvm::MemoryBufferRef(),
388 /*EmbedBitcode*/ true,
389 /*EmbedCmdline*/ false,
390 /*CmdArgs*/ std::vector<uint8_t>());
391
392 std::unique_ptr<ToolOutputFile> DwoOut;
393 SmallString<1024> DwoFile(Conf.SplitDwarfOutput);
394 if (!Conf.DwoDir.empty()) {
395 std::error_code EC;
396 if (auto EC = llvm::sys::fs::create_directories(Conf.DwoDir))
397 report_fatal_error(Twine("Failed to create directory ") + Conf.DwoDir +
398 ": " + EC.message());
399
400 DwoFile = Conf.DwoDir;
401 sys::path::append(DwoFile, std::to_string(Task) + ".dwo");
402 TM->Options.MCOptions.SplitDwarfFile = std::string(DwoFile);
403 } else
404 TM->Options.MCOptions.SplitDwarfFile = Conf.SplitDwarfFile;
405
406 if (!DwoFile.empty()) {
407 std::error_code EC;
408 DwoOut = std::make_unique<ToolOutputFile>(DwoFile, EC, sys::fs::OF_None);
409 if (EC)
410 report_fatal_error(Twine("Failed to open ") + DwoFile + ": " +
411 EC.message());
412 }
413
414 auto Stream = AddStream(Task);
415 legacy::PassManager CodeGenPasses;
416 CodeGenPasses.add(
417 createImmutableModuleSummaryIndexWrapperPass(&CombinedIndex));
418 if (Conf.PreCodeGenPassesHook)
419 Conf.PreCodeGenPassesHook(CodeGenPasses);
420 if (TM->addPassesToEmitFile(CodeGenPasses, *Stream->OS,
421 DwoOut ? &DwoOut->os() : nullptr,
422 Conf.CGFileType))
423 report_fatal_error("Failed to setup codegen");
424 CodeGenPasses.run(Mod);
425
426 if (DwoOut)
427 DwoOut->keep();
428 }
429
splitCodeGen(const Config & C,TargetMachine * TM,AddStreamFn AddStream,unsigned ParallelCodeGenParallelismLevel,Module & Mod,const ModuleSummaryIndex & CombinedIndex)430 static void splitCodeGen(const Config &C, TargetMachine *TM,
431 AddStreamFn AddStream,
432 unsigned ParallelCodeGenParallelismLevel, Module &Mod,
433 const ModuleSummaryIndex &CombinedIndex) {
434 ThreadPool CodegenThreadPool(
435 heavyweight_hardware_concurrency(ParallelCodeGenParallelismLevel));
436 unsigned ThreadCount = 0;
437 const Target *T = &TM->getTarget();
438
439 SplitModule(
440 Mod, ParallelCodeGenParallelismLevel,
441 [&](std::unique_ptr<Module> MPart) {
442 // We want to clone the module in a new context to multi-thread the
443 // codegen. We do it by serializing partition modules to bitcode
444 // (while still on the main thread, in order to avoid data races) and
445 // spinning up new threads which deserialize the partitions into
446 // separate contexts.
447 // FIXME: Provide a more direct way to do this in LLVM.
448 SmallString<0> BC;
449 raw_svector_ostream BCOS(BC);
450 WriteBitcodeToFile(*MPart, BCOS);
451
452 // Enqueue the task
453 CodegenThreadPool.async(
454 [&](const SmallString<0> &BC, unsigned ThreadId) {
455 LTOLLVMContext Ctx(C);
456 Expected<std::unique_ptr<Module>> MOrErr = parseBitcodeFile(
457 MemoryBufferRef(StringRef(BC.data(), BC.size()), "ld-temp.o"),
458 Ctx);
459 if (!MOrErr)
460 report_fatal_error("Failed to read bitcode");
461 std::unique_ptr<Module> MPartInCtx = std::move(MOrErr.get());
462
463 std::unique_ptr<TargetMachine> TM =
464 createTargetMachine(C, T, *MPartInCtx);
465
466 codegen(C, TM.get(), AddStream, ThreadId, *MPartInCtx,
467 CombinedIndex);
468 },
469 // Pass BC using std::move to ensure that it get moved rather than
470 // copied into the thread's context.
471 std::move(BC), ThreadCount++);
472 },
473 false);
474
475 // Because the inner lambda (which runs in a worker thread) captures our local
476 // variables, we need to wait for the worker threads to terminate before we
477 // can leave the function scope.
478 CodegenThreadPool.wait();
479 }
480
initAndLookupTarget(const Config & C,Module & Mod)481 static Expected<const Target *> initAndLookupTarget(const Config &C,
482 Module &Mod) {
483 if (!C.OverrideTriple.empty())
484 Mod.setTargetTriple(C.OverrideTriple);
485 else if (Mod.getTargetTriple().empty())
486 Mod.setTargetTriple(C.DefaultTriple);
487
488 std::string Msg;
489 const Target *T = TargetRegistry::lookupTarget(Mod.getTargetTriple(), Msg);
490 if (!T)
491 return make_error<StringError>(Msg, inconvertibleErrorCode());
492 return T;
493 }
494
finalizeOptimizationRemarks(std::unique_ptr<ToolOutputFile> DiagOutputFile)495 Error lto::finalizeOptimizationRemarks(
496 std::unique_ptr<ToolOutputFile> DiagOutputFile) {
497 // Make sure we flush the diagnostic remarks file in case the linker doesn't
498 // call the global destructors before exiting.
499 if (!DiagOutputFile)
500 return Error::success();
501 DiagOutputFile->keep();
502 DiagOutputFile->os().flush();
503 return Error::success();
504 }
505
backend(const Config & C,AddStreamFn AddStream,unsigned ParallelCodeGenParallelismLevel,Module & Mod,ModuleSummaryIndex & CombinedIndex)506 Error lto::backend(const Config &C, AddStreamFn AddStream,
507 unsigned ParallelCodeGenParallelismLevel, Module &Mod,
508 ModuleSummaryIndex &CombinedIndex) {
509 Expected<const Target *> TOrErr = initAndLookupTarget(C, Mod);
510 if (!TOrErr)
511 return TOrErr.takeError();
512
513 std::unique_ptr<TargetMachine> TM = createTargetMachine(C, *TOrErr, Mod);
514
515 if (!C.CodeGenOnly) {
516 if (!opt(C, TM.get(), 0, Mod, /*IsThinLTO=*/false,
517 /*ExportSummary=*/&CombinedIndex, /*ImportSummary=*/nullptr,
518 /*CmdArgs*/ std::vector<uint8_t>()))
519 return Error::success();
520 }
521
522 if (ParallelCodeGenParallelismLevel == 1) {
523 codegen(C, TM.get(), AddStream, 0, Mod, CombinedIndex);
524 } else {
525 splitCodeGen(C, TM.get(), AddStream, ParallelCodeGenParallelismLevel, Mod,
526 CombinedIndex);
527 }
528 return Error::success();
529 }
530
dropDeadSymbols(Module & Mod,const GVSummaryMapTy & DefinedGlobals,const ModuleSummaryIndex & Index)531 static void dropDeadSymbols(Module &Mod, const GVSummaryMapTy &DefinedGlobals,
532 const ModuleSummaryIndex &Index) {
533 std::vector<GlobalValue*> DeadGVs;
534 for (auto &GV : Mod.global_values())
535 if (GlobalValueSummary *GVS = DefinedGlobals.lookup(GV.getGUID()))
536 if (!Index.isGlobalValueLive(GVS)) {
537 DeadGVs.push_back(&GV);
538 convertToDeclaration(GV);
539 }
540
541 // Now that all dead bodies have been dropped, delete the actual objects
542 // themselves when possible.
543 for (GlobalValue *GV : DeadGVs) {
544 GV->removeDeadConstantUsers();
545 // Might reference something defined in native object (i.e. dropped a
546 // non-prevailing IR def, but we need to keep the declaration).
547 if (GV->use_empty())
548 GV->eraseFromParent();
549 }
550 }
551
thinBackend(const Config & Conf,unsigned Task,AddStreamFn AddStream,Module & Mod,const ModuleSummaryIndex & CombinedIndex,const FunctionImporter::ImportMapTy & ImportList,const GVSummaryMapTy & DefinedGlobals,MapVector<StringRef,BitcodeModule> * ModuleMap,const std::vector<uint8_t> & CmdArgs)552 Error lto::thinBackend(const Config &Conf, unsigned Task, AddStreamFn AddStream,
553 Module &Mod, const ModuleSummaryIndex &CombinedIndex,
554 const FunctionImporter::ImportMapTy &ImportList,
555 const GVSummaryMapTy &DefinedGlobals,
556 MapVector<StringRef, BitcodeModule> *ModuleMap,
557 const std::vector<uint8_t> &CmdArgs) {
558 Expected<const Target *> TOrErr = initAndLookupTarget(Conf, Mod);
559 if (!TOrErr)
560 return TOrErr.takeError();
561
562 std::unique_ptr<TargetMachine> TM = createTargetMachine(Conf, *TOrErr, Mod);
563
564 // Setup optimization remarks.
565 auto DiagFileOrErr = lto::setupLLVMOptimizationRemarks(
566 Mod.getContext(), Conf.RemarksFilename, Conf.RemarksPasses,
567 Conf.RemarksFormat, Conf.RemarksWithHotness, Conf.RemarksHotnessThreshold,
568 Task);
569 if (!DiagFileOrErr)
570 return DiagFileOrErr.takeError();
571 auto DiagnosticOutputFile = std::move(*DiagFileOrErr);
572
573 // Set the partial sample profile ratio in the profile summary module flag of
574 // the module, if applicable.
575 Mod.setPartialSampleProfileRatio(CombinedIndex);
576
577 if (Conf.CodeGenOnly) {
578 codegen(Conf, TM.get(), AddStream, Task, Mod, CombinedIndex);
579 return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
580 }
581
582 if (Conf.PreOptModuleHook && !Conf.PreOptModuleHook(Task, Mod))
583 return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
584
585 auto OptimizeAndCodegen =
586 [&](Module &Mod, TargetMachine *TM,
587 std::unique_ptr<ToolOutputFile> DiagnosticOutputFile) {
588 if (!opt(Conf, TM, Task, Mod, /*IsThinLTO=*/true,
589 /*ExportSummary=*/nullptr, /*ImportSummary=*/&CombinedIndex,
590 CmdArgs))
591 return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
592
593 codegen(Conf, TM, AddStream, Task, Mod, CombinedIndex);
594 return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
595 };
596
597 if (ThinLTOAssumeMerged)
598 return OptimizeAndCodegen(Mod, TM.get(), std::move(DiagnosticOutputFile));
599
600 // When linking an ELF shared object, dso_local should be dropped. We
601 // conservatively do this for -fpic.
602 bool ClearDSOLocalOnDeclarations =
603 TM->getTargetTriple().isOSBinFormatELF() &&
604 TM->getRelocationModel() != Reloc::Static &&
605 Mod.getPIELevel() == PIELevel::Default;
606 renameModuleForThinLTO(Mod, CombinedIndex, ClearDSOLocalOnDeclarations);
607
608 dropDeadSymbols(Mod, DefinedGlobals, CombinedIndex);
609
610 thinLTOFinalizeInModule(Mod, DefinedGlobals, /*PropagateAttrs=*/true);
611
612 if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod))
613 return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
614
615 if (!DefinedGlobals.empty())
616 thinLTOInternalizeModule(Mod, DefinedGlobals);
617
618 if (Conf.PostInternalizeModuleHook &&
619 !Conf.PostInternalizeModuleHook(Task, Mod))
620 return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
621
622 auto ModuleLoader = [&](StringRef Identifier) {
623 assert(Mod.getContext().isODRUniquingDebugTypes() &&
624 "ODR Type uniquing should be enabled on the context");
625 if (ModuleMap) {
626 auto I = ModuleMap->find(Identifier);
627 assert(I != ModuleMap->end());
628 return I->second.getLazyModule(Mod.getContext(),
629 /*ShouldLazyLoadMetadata=*/true,
630 /*IsImporting*/ true);
631 }
632
633 ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> MBOrErr =
634 llvm::MemoryBuffer::getFile(Identifier);
635 if (!MBOrErr)
636 return Expected<std::unique_ptr<llvm::Module>>(make_error<StringError>(
637 Twine("Error loading imported file ") + Identifier + " : ",
638 MBOrErr.getError()));
639
640 Expected<BitcodeModule> BMOrErr = findThinLTOModule(**MBOrErr);
641 if (!BMOrErr)
642 return Expected<std::unique_ptr<llvm::Module>>(make_error<StringError>(
643 Twine("Error loading imported file ") + Identifier + " : " +
644 toString(BMOrErr.takeError()),
645 inconvertibleErrorCode()));
646
647 Expected<std::unique_ptr<Module>> MOrErr =
648 BMOrErr->getLazyModule(Mod.getContext(),
649 /*ShouldLazyLoadMetadata=*/true,
650 /*IsImporting*/ true);
651 if (MOrErr)
652 (*MOrErr)->setOwnedMemoryBuffer(std::move(*MBOrErr));
653 return MOrErr;
654 };
655
656 FunctionImporter Importer(CombinedIndex, ModuleLoader,
657 ClearDSOLocalOnDeclarations);
658 if (Error Err = Importer.importFunctions(Mod, ImportList).takeError())
659 return Err;
660
661 if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod))
662 return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
663
664 return OptimizeAndCodegen(Mod, TM.get(), std::move(DiagnosticOutputFile));
665 }
666
findThinLTOModule(MutableArrayRef<BitcodeModule> BMs)667 BitcodeModule *lto::findThinLTOModule(MutableArrayRef<BitcodeModule> BMs) {
668 if (ThinLTOAssumeMerged && BMs.size() == 1)
669 return BMs.begin();
670
671 for (BitcodeModule &BM : BMs) {
672 Expected<BitcodeLTOInfo> LTOInfo = BM.getLTOInfo();
673 if (LTOInfo && LTOInfo->IsThinLTO)
674 return &BM;
675 }
676 return nullptr;
677 }
678
findThinLTOModule(MemoryBufferRef MBRef)679 Expected<BitcodeModule> lto::findThinLTOModule(MemoryBufferRef MBRef) {
680 Expected<std::vector<BitcodeModule>> BMsOrErr = getBitcodeModuleList(MBRef);
681 if (!BMsOrErr)
682 return BMsOrErr.takeError();
683
684 // The bitcode file may contain multiple modules, we want the one that is
685 // marked as being the ThinLTO module.
686 if (const BitcodeModule *Bm = lto::findThinLTOModule(*BMsOrErr))
687 return *Bm;
688
689 return make_error<StringError>("Could not find module summary",
690 inconvertibleErrorCode());
691 }
692
initImportList(const Module & M,const ModuleSummaryIndex & CombinedIndex,FunctionImporter::ImportMapTy & ImportList)693 bool lto::initImportList(const Module &M,
694 const ModuleSummaryIndex &CombinedIndex,
695 FunctionImporter::ImportMapTy &ImportList) {
696 if (ThinLTOAssumeMerged)
697 return true;
698 // We can simply import the values mentioned in the combined index, since
699 // we should only invoke this using the individual indexes written out
700 // via a WriteIndexesThinBackend.
701 for (const auto &GlobalList : CombinedIndex) {
702 // Ignore entries for undefined references.
703 if (GlobalList.second.SummaryList.empty())
704 continue;
705
706 auto GUID = GlobalList.first;
707 for (const auto &Summary : GlobalList.second.SummaryList) {
708 // Skip the summaries for the importing module. These are included to
709 // e.g. record required linkage changes.
710 if (Summary->modulePath() == M.getModuleIdentifier())
711 continue;
712 // Add an entry to provoke importing by thinBackend.
713 ImportList[Summary->modulePath()].insert(GUID);
714 }
715 }
716 return true;
717 }
718