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/Object/Archive.h" 15 #include "llvm/ADT/STLExtras.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/Support/CommandLine.h" 28 #include "llvm/Support/FileSystem.h" 29 #include "llvm/Support/InitLLVM.h" 30 #include "llvm/Support/Path.h" 31 #include "llvm/Support/SourceMgr.h" 32 #include "llvm/Support/SystemUtils.h" 33 #include "llvm/Support/ToolOutputFile.h" 34 #include "llvm/Support/WithColor.h" 35 #include "llvm/Transforms/IPO/FunctionImport.h" 36 #include "llvm/Transforms/IPO/Internalize.h" 37 #include "llvm/Transforms/Utils/FunctionImportUtils.h" 38 39 #include <memory> 40 #include <utility> 41 using namespace llvm; 42 43 static cl::list<std::string> 44 InputFilenames(cl::Positional, cl::OneOrMore, 45 cl::desc("<input bitcode files>")); 46 47 static cl::list<std::string> OverridingInputs( 48 "override", cl::ZeroOrMore, cl::value_desc("filename"), 49 cl::desc( 50 "input bitcode file which can override previously defined symbol(s)")); 51 52 // Option to simulate function importing for testing. This enables using 53 // llvm-link to simulate ThinLTO backend processes. 54 static cl::list<std::string> Imports( 55 "import", cl::ZeroOrMore, cl::value_desc("function:filename"), 56 cl::desc("Pair of function name and filename, where function should be " 57 "imported from bitcode in filename")); 58 59 // Option to support testing of function importing. The module summary 60 // must be specified in the case were we request imports via the -import 61 // option, as well as when compiling any module with functions that may be 62 // exported (imported by a different llvm-link -import invocation), to ensure 63 // consistent promotion and renaming of locals. 64 static cl::opt<std::string> 65 SummaryIndex("summary-index", cl::desc("Module summary index filename"), 66 cl::init(""), cl::value_desc("filename")); 67 68 static cl::opt<std::string> 69 OutputFilename("o", cl::desc("Override output filename"), cl::init("-"), 70 cl::value_desc("filename")); 71 72 static cl::opt<bool> 73 Internalize("internalize", cl::desc("Internalize linked symbols")); 74 75 static cl::opt<bool> 76 DisableDITypeMap("disable-debug-info-type-map", 77 cl::desc("Don't use a uniquing type map for debug info")); 78 79 static cl::opt<bool> 80 OnlyNeeded("only-needed", cl::desc("Link only needed symbols")); 81 82 static cl::opt<bool> 83 Force("f", cl::desc("Enable binary output on terminals")); 84 85 static cl::opt<bool> 86 DisableLazyLoad("disable-lazy-loading", 87 cl::desc("Disable lazy module loading")); 88 89 static cl::opt<bool> 90 OutputAssembly("S", cl::desc("Write output as LLVM assembly"), cl::Hidden); 91 92 static cl::opt<bool> 93 Verbose("v", cl::desc("Print information about actions taken")); 94 95 static cl::opt<bool> 96 DumpAsm("d", cl::desc("Print assembly as linked"), cl::Hidden); 97 98 static cl::opt<bool> 99 SuppressWarnings("suppress-warnings", cl::desc("Suppress all linking warnings"), 100 cl::init(false)); 101 102 static cl::opt<bool> PreserveBitcodeUseListOrder( 103 "preserve-bc-uselistorder", 104 cl::desc("Preserve use-list order when writing LLVM bitcode."), 105 cl::init(true), cl::Hidden); 106 107 static cl::opt<bool> PreserveAssemblyUseListOrder( 108 "preserve-ll-uselistorder", 109 cl::desc("Preserve use-list order when writing LLVM assembly."), 110 cl::init(false), cl::Hidden); 111 112 static ExitOnError ExitOnErr; 113 114 // Read the specified bitcode file in and return it. This routine searches the 115 // link path for the specified file to try to find it... 116 // 117 static std::unique_ptr<Module> loadFile(const char *argv0, 118 const std::string &FN, 119 LLVMContext &Context, 120 bool MaterializeMetadata = true) { 121 SMDiagnostic Err; 122 if (Verbose) 123 errs() << "Loading '" << FN << "'\n"; 124 std::unique_ptr<Module> Result; 125 if (DisableLazyLoad) 126 Result = parseIRFile(FN, Err, Context); 127 else 128 Result = getLazyIRFileModule(FN, Err, Context, !MaterializeMetadata); 129 130 if (!Result) { 131 Err.print(argv0, errs()); 132 return nullptr; 133 } 134 135 if (MaterializeMetadata) { 136 ExitOnErr(Result->materializeMetadata()); 137 UpgradeDebugInfo(*Result); 138 } 139 140 return Result; 141 } 142 143 static std::unique_ptr<Module> loadArFile(const char *Argv0, 144 const std::string &ArchiveName, 145 LLVMContext &Context, Linker &L, 146 unsigned OrigFlags, 147 unsigned ApplicableFlags) { 148 std::unique_ptr<Module> Result(new Module("ArchiveModule", Context)); 149 if (Verbose) 150 errs() << "Reading library archive file '" << ArchiveName 151 << "' to memory\n"; 152 ErrorOr<std::unique_ptr<MemoryBuffer>> Buf = 153 MemoryBuffer::getFile(ArchiveName, -1, false); 154 ExitOnErr(errorCodeToError(Buf.getError())); 155 Error Err = Error::success(); 156 object::Archive Archive(Buf.get()->getMemBufferRef(), Err); 157 ExitOnErr(std::move(Err)); 158 for (const object::Archive::Child &C : Archive.children(Err)) { 159 Expected<StringRef> Ename = C.getName(); 160 if (Error E = Ename.takeError()) { 161 errs() << Argv0 << ": "; 162 WithColor::error() 163 << " failed to read name of archive member" 164 << ArchiveName << "'\n"; 165 return nullptr; 166 }; 167 std::string ChildName = Ename.get().str(); 168 if (Verbose) 169 errs() << "Parsing member '" << ChildName 170 << "' of archive library to module.\n"; 171 SMDiagnostic ParseErr; 172 Expected<MemoryBufferRef> MemBuf = C.getMemoryBufferRef(); 173 if (Error E = MemBuf.takeError()) { 174 errs() << Argv0 << ": "; 175 WithColor::error() << " loading memory for member '" << ChildName 176 << "' of archive library failed'" << ArchiveName 177 << "'\n"; 178 return nullptr; 179 }; 180 181 if (!isBitcode(reinterpret_cast<const unsigned char *> 182 (MemBuf.get().getBufferStart()), 183 reinterpret_cast<const unsigned char *> 184 (MemBuf.get().getBufferEnd()))) { 185 errs() << Argv0 << ": "; 186 WithColor::error() << " member of archive is not a bitcode file: '" 187 << ChildName << "'\n"; 188 return nullptr; 189 } 190 191 std::unique_ptr<Module> M = parseIR(MemBuf.get(), ParseErr, Context); 192 193 if (!M.get()) { 194 errs() << Argv0 << ": "; 195 WithColor::error() << " parsing member '" << ChildName 196 << "' of archive library failed'" << ArchiveName 197 << "'\n"; 198 return nullptr; 199 } 200 if (Verbose) 201 errs() << "Linking member '" << ChildName << "' of archive library.\n"; 202 if (L.linkModules(*Result, std::move(M), ApplicableFlags)) 203 return nullptr; 204 ApplicableFlags = OrigFlags; 205 } // end for each child 206 ExitOnErr(std::move(Err)); 207 return Result; 208 } 209 210 namespace { 211 212 /// Helper to load on demand a Module from file and cache it for subsequent 213 /// queries during function importing. 214 class ModuleLazyLoaderCache { 215 /// Cache of lazily loaded module for import. 216 StringMap<std::unique_ptr<Module>> ModuleMap; 217 218 /// Retrieve a Module from the cache or lazily load it on demand. 219 std::function<std::unique_ptr<Module>(const char *argv0, 220 const std::string &FileName)> 221 createLazyModule; 222 223 public: 224 /// Create the loader, Module will be initialized in \p Context. 225 ModuleLazyLoaderCache(std::function<std::unique_ptr<Module>( 226 const char *argv0, const std::string &FileName)> 227 createLazyModule) 228 : createLazyModule(std::move(createLazyModule)) {} 229 230 /// Retrieve a Module from the cache or lazily load it on demand. 231 Module &operator()(const char *argv0, const std::string &FileName); 232 233 std::unique_ptr<Module> takeModule(const std::string &FileName) { 234 auto I = ModuleMap.find(FileName); 235 assert(I != ModuleMap.end()); 236 std::unique_ptr<Module> Ret = std::move(I->second); 237 ModuleMap.erase(I); 238 return Ret; 239 } 240 }; 241 242 // Get a Module for \p FileName from the cache, or load it lazily. 243 Module &ModuleLazyLoaderCache::operator()(const char *argv0, 244 const std::string &Identifier) { 245 auto &Module = ModuleMap[Identifier]; 246 if (!Module) 247 Module = createLazyModule(argv0, Identifier); 248 return *Module; 249 } 250 } // anonymous namespace 251 252 namespace { 253 struct LLVMLinkDiagnosticHandler : public DiagnosticHandler { 254 bool handleDiagnostics(const DiagnosticInfo &DI) override { 255 unsigned Severity = DI.getSeverity(); 256 switch (Severity) { 257 case DS_Error: 258 WithColor::error(); 259 break; 260 case DS_Warning: 261 if (SuppressWarnings) 262 return true; 263 WithColor::warning(); 264 break; 265 case DS_Remark: 266 case DS_Note: 267 llvm_unreachable("Only expecting warnings and errors"); 268 } 269 270 DiagnosticPrinterRawOStream DP(errs()); 271 DI.print(DP); 272 errs() << '\n'; 273 return true; 274 } 275 }; 276 } 277 278 /// Import any functions requested via the -import option. 279 static bool importFunctions(const char *argv0, Module &DestModule) { 280 if (SummaryIndex.empty()) 281 return true; 282 std::unique_ptr<ModuleSummaryIndex> Index = 283 ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex)); 284 285 // Map of Module -> List of globals to import from the Module 286 FunctionImporter::ImportMapTy ImportList; 287 288 auto ModuleLoader = [&DestModule](const char *argv0, 289 const std::string &Identifier) { 290 return loadFile(argv0, Identifier, DestModule.getContext(), false); 291 }; 292 293 ModuleLazyLoaderCache ModuleLoaderCache(ModuleLoader); 294 for (const auto &Import : Imports) { 295 // Identify the requested function and its bitcode source file. 296 size_t Idx = Import.find(':'); 297 if (Idx == std::string::npos) { 298 errs() << "Import parameter bad format: " << Import << "\n"; 299 return false; 300 } 301 std::string FunctionName = Import.substr(0, Idx); 302 std::string FileName = Import.substr(Idx + 1, std::string::npos); 303 304 // Load the specified source module. 305 auto &SrcModule = ModuleLoaderCache(argv0, FileName); 306 307 if (verifyModule(SrcModule, &errs())) { 308 errs() << argv0 << ": " << FileName; 309 WithColor::error() << "input module is broken!\n"; 310 return false; 311 } 312 313 Function *F = SrcModule.getFunction(FunctionName); 314 if (!F) { 315 errs() << "Ignoring import request for non-existent function " 316 << FunctionName << " from " << FileName << "\n"; 317 continue; 318 } 319 // We cannot import weak_any functions without possibly affecting the 320 // order they are seen and selected by the linker, changing program 321 // semantics. 322 if (F->hasWeakAnyLinkage()) { 323 errs() << "Ignoring import request for weak-any function " << FunctionName 324 << " from " << FileName << "\n"; 325 continue; 326 } 327 328 if (Verbose) 329 errs() << "Importing " << FunctionName << " from " << FileName << "\n"; 330 331 auto &Entry = ImportList[FileName]; 332 Entry.insert(F->getGUID()); 333 } 334 auto CachedModuleLoader = [&](StringRef Identifier) { 335 return ModuleLoaderCache.takeModule(std::string(Identifier)); 336 }; 337 FunctionImporter Importer(*Index, CachedModuleLoader, 338 /*ClearDSOLocalOnDeclarations=*/false); 339 ExitOnErr(Importer.importFunctions(DestModule, ImportList)); 340 341 return true; 342 } 343 344 static bool linkFiles(const char *argv0, LLVMContext &Context, Linker &L, 345 const cl::list<std::string> &Files, 346 unsigned Flags) { 347 // Filter out flags that don't apply to the first file we load. 348 unsigned ApplicableFlags = Flags & Linker::Flags::OverrideFromSrc; 349 // Similar to some flags, internalization doesn't apply to the first file. 350 bool InternalizeLinkedSymbols = false; 351 for (const auto &File : Files) { 352 std::unique_ptr<Module> M = 353 (llvm::sys::path::extension(File) == ".a") 354 ? loadArFile(argv0, File, Context, L, Flags, ApplicableFlags) 355 : loadFile(argv0, File, Context); 356 if (!M.get()) { 357 errs() << argv0 << ": "; 358 WithColor::error() << " loading file '" << File << "'\n"; 359 return false; 360 } 361 362 // Note that when ODR merging types cannot verify input files in here When 363 // doing that debug metadata in the src module might already be pointing to 364 // the destination. 365 if (DisableDITypeMap && verifyModule(*M, &errs())) { 366 errs() << argv0 << ": " << File << ": "; 367 WithColor::error() << "input module is broken!\n"; 368 return false; 369 } 370 371 // If a module summary index is supplied, load it so linkInModule can treat 372 // local functions/variables as exported and promote if necessary. 373 if (!SummaryIndex.empty()) { 374 std::unique_ptr<ModuleSummaryIndex> Index = 375 ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex)); 376 377 // Conservatively mark all internal values as promoted, since this tool 378 // does not do the ThinLink that would normally determine what values to 379 // promote. 380 for (auto &I : *Index) { 381 for (auto &S : I.second.SummaryList) { 382 if (GlobalValue::isLocalLinkage(S->linkage())) 383 S->setLinkage(GlobalValue::ExternalLinkage); 384 } 385 } 386 387 // Promotion 388 if (renameModuleForThinLTO(*M, *Index, 389 /*ClearDSOLocalOnDeclarations=*/false)) 390 return true; 391 } 392 393 if (Verbose) 394 errs() << "Linking in '" << File << "'\n"; 395 396 bool Err = false; 397 if (InternalizeLinkedSymbols) { 398 Err = L.linkInModule( 399 std::move(M), ApplicableFlags, [](Module &M, const StringSet<> &GVS) { 400 internalizeModule(M, [&GVS](const GlobalValue &GV) { 401 return !GV.hasName() || (GVS.count(GV.getName()) == 0); 402 }); 403 }); 404 } else { 405 Err = L.linkInModule(std::move(M), ApplicableFlags); 406 } 407 408 if (Err) 409 return false; 410 411 // Internalization applies to linking of subsequent files. 412 InternalizeLinkedSymbols = Internalize; 413 414 // All linker flags apply to linking of subsequent files. 415 ApplicableFlags = Flags; 416 } 417 418 return true; 419 } 420 421 int main(int argc, char **argv) { 422 InitLLVM X(argc, argv); 423 ExitOnErr.setBanner(std::string(argv[0]) + ": "); 424 425 LLVMContext Context; 426 Context.setDiagnosticHandler( 427 std::make_unique<LLVMLinkDiagnosticHandler>(), true); 428 cl::ParseCommandLineOptions(argc, argv, "llvm linker\n"); 429 430 if (!DisableDITypeMap) 431 Context.enableDebugTypeODRUniquing(); 432 433 auto Composite = std::make_unique<Module>("llvm-link", Context); 434 Linker L(*Composite); 435 436 unsigned Flags = Linker::Flags::None; 437 if (OnlyNeeded) 438 Flags |= Linker::Flags::LinkOnlyNeeded; 439 440 // First add all the regular input files 441 if (!linkFiles(argv[0], Context, L, InputFilenames, Flags)) 442 return 1; 443 444 // Next the -override ones. 445 if (!linkFiles(argv[0], Context, L, OverridingInputs, 446 Flags | Linker::Flags::OverrideFromSrc)) 447 return 1; 448 449 // Import any functions requested via -import 450 if (!importFunctions(argv[0], *Composite)) 451 return 1; 452 453 if (DumpAsm) 454 errs() << "Here's the assembly:\n" << *Composite; 455 456 std::error_code EC; 457 ToolOutputFile Out(OutputFilename, EC, sys::fs::OF_None); 458 if (EC) { 459 WithColor::error() << EC.message() << '\n'; 460 return 1; 461 } 462 463 if (verifyModule(*Composite, &errs())) { 464 errs() << argv[0] << ": "; 465 WithColor::error() << "linked module is broken!\n"; 466 return 1; 467 } 468 469 if (Verbose) 470 errs() << "Writing bitcode...\n"; 471 if (OutputAssembly) { 472 Composite->print(Out.os(), nullptr, PreserveAssemblyUseListOrder); 473 } else if (Force || !CheckBitcodeOutputToConsole(Out.os())) 474 WriteBitcodeToFile(*Composite, Out.os(), PreserveBitcodeUseListOrder); 475 476 // Declare success. 477 Out.keep(); 478 479 return 0; 480 } 481