1 //===- llvm-link.cpp - Low-level LLVM linker ------------------------------===// 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 utility may be invoked in the following manner: 10 // llvm-link a.bc b.bc c.bc -o x.bc 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/ADT/STLExtras.h" 15 #include "llvm/BinaryFormat/Magic.h" 16 #include "llvm/Bitcode/BitcodeReader.h" 17 #include "llvm/Bitcode/BitcodeWriter.h" 18 #include "llvm/IR/AutoUpgrade.h" 19 #include "llvm/IR/DiagnosticInfo.h" 20 #include "llvm/IR/DiagnosticPrinter.h" 21 #include "llvm/IR/LLVMContext.h" 22 #include "llvm/IR/Module.h" 23 #include "llvm/IR/ModuleSummaryIndex.h" 24 #include "llvm/IR/Verifier.h" 25 #include "llvm/IRReader/IRReader.h" 26 #include "llvm/Linker/Linker.h" 27 #include "llvm/Object/Archive.h" 28 #include "llvm/Support/CommandLine.h" 29 #include "llvm/Support/FileSystem.h" 30 #include "llvm/Support/InitLLVM.h" 31 #include "llvm/Support/Path.h" 32 #include "llvm/Support/SourceMgr.h" 33 #include "llvm/Support/SystemUtils.h" 34 #include "llvm/Support/ToolOutputFile.h" 35 #include "llvm/Support/WithColor.h" 36 #include "llvm/Transforms/IPO/FunctionImport.h" 37 #include "llvm/Transforms/IPO/Internalize.h" 38 #include "llvm/Transforms/Utils/FunctionImportUtils.h" 39 40 #include <memory> 41 #include <utility> 42 using namespace llvm; 43 44 static cl::OptionCategory LinkCategory("Link Options"); 45 46 static cl::list<std::string> InputFilenames(cl::Positional, cl::OneOrMore, 47 cl::desc("<input bitcode files>"), 48 cl::cat(LinkCategory)); 49 50 static cl::list<std::string> OverridingInputs( 51 "override", cl::value_desc("filename"), 52 cl::desc( 53 "input bitcode file which can override previously defined symbol(s)"), 54 cl::cat(LinkCategory)); 55 56 // Option to simulate function importing for testing. This enables using 57 // llvm-link to simulate ThinLTO backend processes. 58 static cl::list<std::string> Imports( 59 "import", cl::value_desc("function:filename"), 60 cl::desc("Pair of function name and filename, where function should be " 61 "imported from bitcode in filename"), 62 cl::cat(LinkCategory)); 63 64 // Option to support testing of function importing. The module summary 65 // must be specified in the case were we request imports via the -import 66 // option, as well as when compiling any module with functions that may be 67 // exported (imported by a different llvm-link -import invocation), to ensure 68 // consistent promotion and renaming of locals. 69 static cl::opt<std::string> 70 SummaryIndex("summary-index", cl::desc("Module summary index filename"), 71 cl::init(""), cl::value_desc("filename"), 72 cl::cat(LinkCategory)); 73 74 static cl::opt<std::string> 75 OutputFilename("o", cl::desc("Override output filename"), cl::init("-"), 76 cl::value_desc("filename"), cl::cat(LinkCategory)); 77 78 static cl::opt<bool> Internalize("internalize", 79 cl::desc("Internalize linked symbols"), 80 cl::cat(LinkCategory)); 81 82 static cl::opt<bool> 83 DisableDITypeMap("disable-debug-info-type-map", 84 cl::desc("Don't use a uniquing type map for debug info"), 85 cl::cat(LinkCategory)); 86 87 static cl::opt<bool> OnlyNeeded("only-needed", 88 cl::desc("Link only needed symbols"), 89 cl::cat(LinkCategory)); 90 91 static cl::opt<bool> Force("f", cl::desc("Enable binary output on terminals"), 92 cl::cat(LinkCategory)); 93 94 static cl::opt<bool> DisableLazyLoad("disable-lazy-loading", 95 cl::desc("Disable lazy module loading"), 96 cl::cat(LinkCategory)); 97 98 static cl::opt<bool> OutputAssembly("S", 99 cl::desc("Write output as LLVM assembly"), 100 cl::Hidden, cl::cat(LinkCategory)); 101 102 static cl::opt<bool> Verbose("v", 103 cl::desc("Print information about actions taken"), 104 cl::cat(LinkCategory)); 105 106 static cl::opt<bool> DumpAsm("d", cl::desc("Print assembly as linked"), 107 cl::Hidden, cl::cat(LinkCategory)); 108 109 static cl::opt<bool> SuppressWarnings("suppress-warnings", 110 cl::desc("Suppress all linking warnings"), 111 cl::init(false), cl::cat(LinkCategory)); 112 113 static cl::opt<bool> PreserveBitcodeUseListOrder( 114 "preserve-bc-uselistorder", 115 cl::desc("Preserve use-list order when writing LLVM bitcode."), 116 cl::init(true), cl::Hidden, cl::cat(LinkCategory)); 117 118 static cl::opt<bool> PreserveAssemblyUseListOrder( 119 "preserve-ll-uselistorder", 120 cl::desc("Preserve use-list order when writing LLVM assembly."), 121 cl::init(false), cl::Hidden, cl::cat(LinkCategory)); 122 123 static cl::opt<bool> NoVerify("disable-verify", 124 cl::desc("Do not run the verifier"), cl::Hidden, 125 cl::cat(LinkCategory)); 126 127 static cl::opt<bool> IgnoreNonBitcode( 128 "ignore-non-bitcode", 129 cl::desc("Do not report an error for non-bitcode files in archives"), 130 cl::Hidden); 131 132 static cl::opt<bool> TryUseNewDbgInfoFormat( 133 "try-experimental-debuginfo-iterators", 134 cl::desc("Enable debuginfo iterator positions, if they're built in"), 135 cl::init(false)); 136 137 extern cl::opt<bool> UseNewDbgInfoFormat; 138 extern cl::opt<cl::boolOrDefault> PreserveInputDbgFormat; 139 extern cl::opt<bool> WriteNewDbgInfoFormat; 140 extern bool WriteNewDbgInfoFormatToBitcode; 141 142 extern cl::opt<cl::boolOrDefault> LoadBitcodeIntoNewDbgInfoFormat; 143 144 static ExitOnError ExitOnErr; 145 146 // Read the specified bitcode file in and return it. This routine searches the 147 // link path for the specified file to try to find it... 148 // 149 static std::unique_ptr<Module> loadFile(const char *argv0, 150 std::unique_ptr<MemoryBuffer> Buffer, 151 LLVMContext &Context, 152 bool MaterializeMetadata = true) { 153 SMDiagnostic Err; 154 if (Verbose) 155 errs() << "Loading '" << Buffer->getBufferIdentifier() << "'\n"; 156 std::unique_ptr<Module> Result; 157 if (DisableLazyLoad) 158 Result = parseIR(*Buffer, Err, Context); 159 else 160 Result = 161 getLazyIRModule(std::move(Buffer), Err, Context, !MaterializeMetadata); 162 163 if (!Result) { 164 Err.print(argv0, errs()); 165 return nullptr; 166 } 167 168 if (MaterializeMetadata) { 169 ExitOnErr(Result->materializeMetadata()); 170 UpgradeDebugInfo(*Result); 171 } 172 173 return Result; 174 } 175 176 static std::unique_ptr<Module> loadArFile(const char *Argv0, 177 std::unique_ptr<MemoryBuffer> Buffer, 178 LLVMContext &Context) { 179 std::unique_ptr<Module> Result(new Module("ArchiveModule", Context)); 180 StringRef ArchiveName = Buffer->getBufferIdentifier(); 181 if (Verbose) 182 errs() << "Reading library archive file '" << ArchiveName 183 << "' to memory\n"; 184 Expected<std::unique_ptr<object::Archive>> ArchiveOrError = 185 object::Archive::create(Buffer->getMemBufferRef()); 186 if (!ArchiveOrError) 187 ExitOnErr(ArchiveOrError.takeError()); 188 189 std::unique_ptr<object::Archive> Archive = std::move(ArchiveOrError.get()); 190 191 Linker L(*Result); 192 Error Err = Error::success(); 193 for (const object::Archive::Child &C : Archive->children(Err)) { 194 Expected<StringRef> Ename = C.getName(); 195 if (Error E = Ename.takeError()) { 196 errs() << Argv0 << ": "; 197 WithColor::error() << " failed to read name of archive member" 198 << ArchiveName << "'\n"; 199 return nullptr; 200 } 201 std::string ChildName = Ename.get().str(); 202 if (Verbose) 203 errs() << "Parsing member '" << ChildName 204 << "' of archive library to module.\n"; 205 SMDiagnostic ParseErr; 206 Expected<MemoryBufferRef> MemBuf = C.getMemoryBufferRef(); 207 if (Error E = MemBuf.takeError()) { 208 errs() << Argv0 << ": "; 209 WithColor::error() << " loading memory for member '" << ChildName 210 << "' of archive library failed'" << ArchiveName 211 << "'\n"; 212 return nullptr; 213 }; 214 215 if (!isBitcode(reinterpret_cast<const unsigned char *>( 216 MemBuf.get().getBufferStart()), 217 reinterpret_cast<const unsigned char *>( 218 MemBuf.get().getBufferEnd()))) { 219 if (IgnoreNonBitcode) 220 continue; 221 errs() << Argv0 << ": "; 222 WithColor::error() << " member of archive is not a bitcode file: '" 223 << ChildName << "'\n"; 224 return nullptr; 225 } 226 227 std::unique_ptr<Module> M; 228 if (DisableLazyLoad) 229 M = parseIR(MemBuf.get(), ParseErr, Context); 230 else 231 M = getLazyIRModule(MemoryBuffer::getMemBuffer(MemBuf.get(), false), 232 ParseErr, Context); 233 234 if (!M) { 235 errs() << Argv0 << ": "; 236 WithColor::error() << " parsing member '" << ChildName 237 << "' of archive library failed'" << ArchiveName 238 << "'\n"; 239 return nullptr; 240 } 241 if (Verbose) 242 errs() << "Linking member '" << ChildName << "' of archive library.\n"; 243 if (L.linkInModule(std::move(M))) 244 return nullptr; 245 } // end for each child 246 ExitOnErr(std::move(Err)); 247 return Result; 248 } 249 250 namespace { 251 252 /// Helper to load on demand a Module from file and cache it for subsequent 253 /// queries during function importing. 254 class ModuleLazyLoaderCache { 255 /// Cache of lazily loaded module for import. 256 StringMap<std::unique_ptr<Module>> ModuleMap; 257 258 /// Retrieve a Module from the cache or lazily load it on demand. 259 std::function<std::unique_ptr<Module>(const char *argv0, 260 const std::string &FileName)> 261 createLazyModule; 262 263 public: 264 /// Create the loader, Module will be initialized in \p Context. 265 ModuleLazyLoaderCache(std::function<std::unique_ptr<Module>( 266 const char *argv0, const std::string &FileName)> 267 createLazyModule) 268 : createLazyModule(std::move(createLazyModule)) {} 269 270 /// Retrieve a Module from the cache or lazily load it on demand. 271 Module &operator()(const char *argv0, const std::string &FileName); 272 273 std::unique_ptr<Module> takeModule(const std::string &FileName) { 274 auto I = ModuleMap.find(FileName); 275 assert(I != ModuleMap.end()); 276 std::unique_ptr<Module> Ret = std::move(I->second); 277 ModuleMap.erase(I); 278 return Ret; 279 } 280 }; 281 282 // Get a Module for \p FileName from the cache, or load it lazily. 283 Module &ModuleLazyLoaderCache::operator()(const char *argv0, 284 const std::string &Identifier) { 285 auto &Module = ModuleMap[Identifier]; 286 if (!Module) { 287 Module = createLazyModule(argv0, Identifier); 288 assert(Module && "Failed to create lazy module!"); 289 } 290 return *Module; 291 } 292 } // anonymous namespace 293 294 namespace { 295 struct LLVMLinkDiagnosticHandler : public DiagnosticHandler { 296 bool handleDiagnostics(const DiagnosticInfo &DI) override { 297 unsigned Severity = DI.getSeverity(); 298 switch (Severity) { 299 case DS_Error: 300 WithColor::error(); 301 break; 302 case DS_Warning: 303 if (SuppressWarnings) 304 return true; 305 WithColor::warning(); 306 break; 307 case DS_Remark: 308 case DS_Note: 309 llvm_unreachable("Only expecting warnings and errors"); 310 } 311 312 DiagnosticPrinterRawOStream DP(errs()); 313 DI.print(DP); 314 errs() << '\n'; 315 return true; 316 } 317 }; 318 } // namespace 319 320 /// Import any functions requested via the -import option. 321 static bool importFunctions(const char *argv0, Module &DestModule) { 322 if (SummaryIndex.empty()) 323 return true; 324 std::unique_ptr<ModuleSummaryIndex> Index = 325 ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex)); 326 327 // Map of Module -> List of globals to import from the Module 328 FunctionImporter::ImportMapTy ImportList; 329 330 auto ModuleLoader = [&DestModule](const char *argv0, 331 const std::string &Identifier) { 332 std::unique_ptr<MemoryBuffer> Buffer = 333 ExitOnErr(errorOrToExpected(MemoryBuffer::getFileOrSTDIN(Identifier))); 334 return loadFile(argv0, std::move(Buffer), DestModule.getContext(), false); 335 }; 336 337 ModuleLazyLoaderCache ModuleLoaderCache(ModuleLoader); 338 // Owns the filename strings used to key into the ImportList. Normally this is 339 // constructed from the index and the strings are owned by the index, however, 340 // since we are synthesizing this data structure from options we need a cache 341 // to own those strings. 342 StringSet<> FileNameStringCache; 343 for (const auto &Import : Imports) { 344 // Identify the requested function and its bitcode source file. 345 size_t Idx = Import.find(':'); 346 if (Idx == std::string::npos) { 347 errs() << "Import parameter bad format: " << Import << "\n"; 348 return false; 349 } 350 std::string FunctionName = Import.substr(0, Idx); 351 std::string FileName = Import.substr(Idx + 1, std::string::npos); 352 353 // Load the specified source module. 354 auto &SrcModule = ModuleLoaderCache(argv0, FileName); 355 356 if (!NoVerify && verifyModule(SrcModule, &errs())) { 357 errs() << argv0 << ": " << FileName; 358 WithColor::error() << "input module is broken!\n"; 359 return false; 360 } 361 362 Function *F = SrcModule.getFunction(FunctionName); 363 if (!F) { 364 errs() << "Ignoring import request for non-existent function " 365 << FunctionName << " from " << FileName << "\n"; 366 continue; 367 } 368 // We cannot import weak_any functions without possibly affecting the 369 // order they are seen and selected by the linker, changing program 370 // semantics. 371 if (F->hasWeakAnyLinkage()) { 372 errs() << "Ignoring import request for weak-any function " << FunctionName 373 << " from " << FileName << "\n"; 374 continue; 375 } 376 377 if (Verbose) 378 errs() << "Importing " << FunctionName << " from " << FileName << "\n"; 379 380 // `-import` specifies the `<filename,function-name>` pairs to import as 381 // definition, so make the import type definition directly. 382 // FIXME: A follow-up patch should add test coverage for import declaration 383 // in `llvm-link` CLI (e.g., by introducing a new command line option). 384 auto &Entry = 385 ImportList[FileNameStringCache.insert(FileName).first->getKey()]; 386 Entry[F->getGUID()] = GlobalValueSummary::Definition; 387 } 388 auto CachedModuleLoader = [&](StringRef Identifier) { 389 return ModuleLoaderCache.takeModule(std::string(Identifier)); 390 }; 391 FunctionImporter Importer(*Index, CachedModuleLoader, 392 /*ClearDSOLocalOnDeclarations=*/false); 393 ExitOnErr(Importer.importFunctions(DestModule, ImportList)); 394 395 return true; 396 } 397 398 static bool linkFiles(const char *argv0, LLVMContext &Context, Linker &L, 399 const cl::list<std::string> &Files, unsigned Flags) { 400 // Filter out flags that don't apply to the first file we load. 401 unsigned ApplicableFlags = Flags & Linker::Flags::OverrideFromSrc; 402 // Similar to some flags, internalization doesn't apply to the first file. 403 bool InternalizeLinkedSymbols = false; 404 for (const auto &File : Files) { 405 auto BufferOrErr = MemoryBuffer::getFileOrSTDIN(File); 406 407 // When we encounter a missing file, make sure we expose its name. 408 if (auto EC = BufferOrErr.getError()) 409 if (EC == std::errc::no_such_file_or_directory) 410 ExitOnErr(createStringError(EC, "No such file or directory: '%s'", 411 File.c_str())); 412 413 std::unique_ptr<MemoryBuffer> Buffer = 414 ExitOnErr(errorOrToExpected(std::move(BufferOrErr))); 415 416 std::unique_ptr<Module> M = 417 identify_magic(Buffer->getBuffer()) == file_magic::archive 418 ? loadArFile(argv0, std::move(Buffer), Context) 419 : loadFile(argv0, std::move(Buffer), Context); 420 if (!M) { 421 errs() << argv0 << ": "; 422 WithColor::error() << " loading file '" << File << "'\n"; 423 return false; 424 } 425 426 // Note that when ODR merging types cannot verify input files in here When 427 // doing that debug metadata in the src module might already be pointing to 428 // the destination. 429 if (DisableDITypeMap && !NoVerify && verifyModule(*M, &errs())) { 430 errs() << argv0 << ": " << File << ": "; 431 WithColor::error() << "input module is broken!\n"; 432 return false; 433 } 434 435 // If a module summary index is supplied, load it so linkInModule can treat 436 // local functions/variables as exported and promote if necessary. 437 if (!SummaryIndex.empty()) { 438 std::unique_ptr<ModuleSummaryIndex> Index = 439 ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex)); 440 441 // Conservatively mark all internal values as promoted, since this tool 442 // does not do the ThinLink that would normally determine what values to 443 // promote. 444 for (auto &I : *Index) { 445 for (auto &S : I.second.SummaryList) { 446 if (GlobalValue::isLocalLinkage(S->linkage())) 447 S->setLinkage(GlobalValue::ExternalLinkage); 448 } 449 } 450 451 // Promotion 452 if (renameModuleForThinLTO(*M, *Index, 453 /*ClearDSOLocalOnDeclarations=*/false)) 454 return true; 455 } 456 457 if (Verbose) 458 errs() << "Linking in '" << File << "'\n"; 459 460 bool Err = false; 461 if (InternalizeLinkedSymbols) { 462 Err = L.linkInModule( 463 std::move(M), ApplicableFlags, [](Module &M, const StringSet<> &GVS) { 464 internalizeModule(M, [&GVS](const GlobalValue &GV) { 465 return !GV.hasName() || (GVS.count(GV.getName()) == 0); 466 }); 467 }); 468 } else { 469 Err = L.linkInModule(std::move(M), ApplicableFlags); 470 } 471 472 if (Err) 473 return false; 474 475 // Internalization applies to linking of subsequent files. 476 InternalizeLinkedSymbols = Internalize; 477 478 // All linker flags apply to linking of subsequent files. 479 ApplicableFlags = Flags; 480 } 481 482 return true; 483 } 484 485 int main(int argc, char **argv) { 486 InitLLVM X(argc, argv); 487 ExitOnErr.setBanner(std::string(argv[0]) + ": "); 488 489 cl::HideUnrelatedOptions({&LinkCategory, &getColorCategory()}); 490 cl::ParseCommandLineOptions(argc, argv, "llvm linker\n"); 491 492 // Load bitcode into the new debug info format by default. 493 if (LoadBitcodeIntoNewDbgInfoFormat == cl::boolOrDefault::BOU_UNSET) 494 LoadBitcodeIntoNewDbgInfoFormat = cl::boolOrDefault::BOU_TRUE; 495 496 // Since llvm-link collects multiple IR modules together, for simplicity's 497 // sake we disable the "PreserveInputDbgFormat" flag to enforce a single 498 // debug info format. 499 PreserveInputDbgFormat = cl::boolOrDefault::BOU_FALSE; 500 501 LLVMContext Context; 502 Context.setDiagnosticHandler(std::make_unique<LLVMLinkDiagnosticHandler>(), 503 true); 504 505 if (!DisableDITypeMap) 506 Context.enableDebugTypeODRUniquing(); 507 508 auto Composite = std::make_unique<Module>("llvm-link", Context); 509 Linker L(*Composite); 510 511 unsigned Flags = Linker::Flags::None; 512 if (OnlyNeeded) 513 Flags |= Linker::Flags::LinkOnlyNeeded; 514 515 // First add all the regular input files 516 if (!linkFiles(argv[0], Context, L, InputFilenames, Flags)) 517 return 1; 518 519 // Next the -override ones. 520 if (!linkFiles(argv[0], Context, L, OverridingInputs, 521 Flags | Linker::Flags::OverrideFromSrc)) 522 return 1; 523 524 // Import any functions requested via -import 525 if (!importFunctions(argv[0], *Composite)) 526 return 1; 527 528 if (DumpAsm) 529 errs() << "Here's the assembly:\n" << *Composite; 530 531 std::error_code EC; 532 ToolOutputFile Out(OutputFilename, EC, 533 OutputAssembly ? sys::fs::OF_TextWithCRLF 534 : sys::fs::OF_None); 535 if (EC) { 536 WithColor::error() << EC.message() << '\n'; 537 return 1; 538 } 539 540 if (!NoVerify && verifyModule(*Composite, &errs())) { 541 errs() << argv[0] << ": "; 542 WithColor::error() << "linked module is broken!\n"; 543 return 1; 544 } 545 546 if (Verbose) 547 errs() << "Writing bitcode...\n"; 548 auto SetFormat = [&](bool NewFormat) { 549 Composite->setIsNewDbgInfoFormat(NewFormat); 550 if (NewFormat) 551 Composite->removeDebugIntrinsicDeclarations(); 552 }; 553 if (OutputAssembly) { 554 SetFormat(WriteNewDbgInfoFormat); 555 Composite->print(Out.os(), nullptr, PreserveAssemblyUseListOrder); 556 } else if (Force || !CheckBitcodeOutputToConsole(Out.os())) { 557 SetFormat(UseNewDbgInfoFormat && WriteNewDbgInfoFormatToBitcode); 558 WriteBitcodeToFile(*Composite, Out.os(), PreserveBitcodeUseListOrder); 559 } 560 561 // Declare success. 562 Out.keep(); 563 564 return 0; 565 } 566