llvm/tools/llvm-link/llvm-link.cpp

   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 ExitOnError ExitOnErr;
 133
 134 // Read the specified bitcode file in and return it. This routine searches the
 135 // link path for the specified file to try to find it...
 136 //
 137 static std::unique_ptr<Module> loadFile(const char *argv0,
 138                                         std::unique_ptr<MemoryBuffer> Buffer,
 139                                         LLVMContext &Context,
 140                                         bool MaterializeMetadata = true) {
 141   SMDiagnostic Err;
 142   if (Verbose)
 143     errs() << "Loading '" << Buffer->getBufferIdentifier() << "'\n";
 144   std::unique_ptr<Module> Result;
 145   if (DisableLazyLoad)
 146     Result = parseIR(*Buffer, Err, Context);
 147   else
 148     Result =
 149         getLazyIRModule(std::move(Buffer), Err, Context, !MaterializeMetadata);
 150
 151   if (!Result) {
 152     Err.print(argv0, errs());
 153     return nullptr;
 154   }
 155
 156   if (MaterializeMetadata) {
 157     ExitOnErr(Result->materializeMetadata());
 158     UpgradeDebugInfo(*Result);
 159   }
 160
 161   return Result;
 162 }
 163
 164 static std::unique_ptr<Module> loadArFile(const char *Argv0,
 165                                           std::unique_ptr<MemoryBuffer> Buffer,
 166                                           LLVMContext &Context) {
 167   std::unique_ptr<Module> Result(new Module("ArchiveModule", Context));
 168   StringRef ArchiveName = Buffer->getBufferIdentifier();
 169   if (Verbose)
 170     errs() << "Reading library archive file '" << ArchiveName
 171            << "' to memory\n";
 172   Expected<std::unique_ptr<object::Archive>> ArchiveOrError =
 173       object::Archive::create(Buffer->getMemBufferRef());
 174   if (!ArchiveOrError)
 175     ExitOnErr(ArchiveOrError.takeError());
 176
 177   std::unique_ptr<object::Archive> Archive = std::move(ArchiveOrError.get());
 178
 179   Linker L(*Result);
 180   Error Err = Error::success();
 181   for (const object::Archive::Child &C : Archive->children(Err)) {
 182     Expected<StringRef> Ename = C.getName();
 183     if (Error E = Ename.takeError()) {
 184       errs() << Argv0 << ": ";
 185       WithColor::error() << " failed to read name of archive member"
 186                          << ArchiveName << "'\n";
 187       return nullptr;
 188     }
 189     std::string ChildName = Ename.get().str();
 190     if (Verbose)
 191       errs() << "Parsing member '" << ChildName
 192              << "' of archive library to module.\n";
 193     SMDiagnostic ParseErr;
 194     Expected<MemoryBufferRef> MemBuf = C.getMemoryBufferRef();
 195     if (Error E = MemBuf.takeError()) {
 196       errs() << Argv0 << ": ";
 197       WithColor::error() << " loading memory for member '" << ChildName
 198                          << "' of archive library failed'" << ArchiveName
 199                          << "'\n";
 200       return nullptr;
 201     };
 202
 203     if (!isBitcode(reinterpret_cast<const unsigned char *>(
 204                        MemBuf.get().getBufferStart()),
 205                    reinterpret_cast<const unsigned char *>(
 206                        MemBuf.get().getBufferEnd()))) {
 207       if (IgnoreNonBitcode)
 208         continue;
 209       errs() << Argv0 << ": ";
 210       WithColor::error() << "  member of archive is not a bitcode file: '"
 211                          << ChildName << "'\n";
 212       return nullptr;
 213     }
 214
 215     std::unique_ptr<Module> M;
 216     if (DisableLazyLoad)
 217       M = parseIR(MemBuf.get(), ParseErr, Context);
 218     else
 219       M = getLazyIRModule(MemoryBuffer::getMemBuffer(MemBuf.get(), false),
 220                           ParseErr, Context);
 221
 222     if (!M.get()) {
 223       errs() << Argv0 << ": ";
 224       WithColor::error() << " parsing member '" << ChildName
 225                          << "' of archive library failed'" << ArchiveName
 226                          << "'\n";
 227       return nullptr;
 228     }
 229     if (Verbose)
 230       errs() << "Linking member '" << ChildName << "' of archive library.\n";
 231     if (L.linkInModule(std::move(M)))
 232       return nullptr;
 233   } // end for each child
 234   ExitOnErr(std::move(Err));
 235   return Result;
 236 }
 237
 238 namespace {
 239
 240 /// Helper to load on demand a Module from file and cache it for subsequent
 241 /// queries during function importing.
 242 class ModuleLazyLoaderCache {
 243   /// Cache of lazily loaded module for import.
 244   StringMap<std::unique_ptr<Module>> ModuleMap;
 245
 246   /// Retrieve a Module from the cache or lazily load it on demand.
 247   std::function<std::unique_ptr<Module>(const char *argv0,
 248                                         const std::string &FileName)>
 249       createLazyModule;
 250
 251 public:
 252   /// Create the loader, Module will be initialized in \p Context.
 253   ModuleLazyLoaderCache(std::function<std::unique_ptr<Module>(
 254                             const char *argv0, const std::string &FileName)>
 255                             createLazyModule)
 256       : createLazyModule(std::move(createLazyModule)) {}
 257
 258   /// Retrieve a Module from the cache or lazily load it on demand.
 259   Module &operator()(const char *argv0, const std::string &FileName);
 260
 261   std::unique_ptr<Module> takeModule(const std::string &FileName) {
 262     auto I = ModuleMap.find(FileName);
 263     assert(I != ModuleMap.end());
 264     std::unique_ptr<Module> Ret = std::move(I->second);
 265     ModuleMap.erase(I);
 266     return Ret;
 267   }
 268 };
 269
 270 // Get a Module for \p FileName from the cache, or load it lazily.
 271 Module &ModuleLazyLoaderCache::operator()(const char *argv0,
 272                                           const std::string &Identifier) {
 273   auto &Module = ModuleMap[Identifier];
 274   if (!Module) {
 275     Module = createLazyModule(argv0, Identifier);
 276     assert(Module && "Failed to create lazy module!");
 277   }
 278   return *Module;
 279 }
 280 } // anonymous namespace
 281
 282 namespace {
 283 struct LLVMLinkDiagnosticHandler : public DiagnosticHandler {
 284   bool handleDiagnostics(const DiagnosticInfo &DI) override {
 285     unsigned Severity = DI.getSeverity();
 286     switch (Severity) {
 287     case DS_Error:
 288       WithColor::error();
 289       break;
 290     case DS_Warning:
 291       if (SuppressWarnings)
 292         return true;
 293       WithColor::warning();
 294       break;
 295     case DS_Remark:
 296     case DS_Note:
 297       llvm_unreachable("Only expecting warnings and errors");
 298     }
 299
 300     DiagnosticPrinterRawOStream DP(errs());
 301     DI.print(DP);
 302     errs() << '\n';
 303     return true;
 304   }
 305 };
 306 } // namespace
 307
 308 /// Import any functions requested via the -import option.
 309 static bool importFunctions(const char *argv0, Module &DestModule) {
 310   if (SummaryIndex.empty())
 311     return true;
 312   std::unique_ptr<ModuleSummaryIndex> Index =
 313       ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex));
 314
 315   // Map of Module -> List of globals to import from the Module
 316   FunctionImporter::ImportMapTy ImportList;
 317
 318   auto ModuleLoader = [&DestModule](const char *argv0,
 319                                     const std::string &Identifier) {
 320     std::unique_ptr<MemoryBuffer> Buffer =
 321         ExitOnErr(errorOrToExpected(MemoryBuffer::getFileOrSTDIN(Identifier)));
 322     return loadFile(argv0, std::move(Buffer), DestModule.getContext(), false);
 323   };
 324
 325   ModuleLazyLoaderCache ModuleLoaderCache(ModuleLoader);
 326   for (const auto &Import : Imports) {
 327     // Identify the requested function and its bitcode source file.
 328     size_t Idx = Import.find(':');
 329     if (Idx == std::string::npos) {
 330       errs() << "Import parameter bad format: " << Import << "\n";
 331       return false;
 332     }
 333     std::string FunctionName = Import.substr(0, Idx);
 334     std::string FileName = Import.substr(Idx + 1, std::string::npos);
 335
 336     // Load the specified source module.
 337     auto &SrcModule = ModuleLoaderCache(argv0, FileName);
 338
 339     if (!NoVerify && verifyModule(SrcModule, &errs())) {
 340       errs() << argv0 << ": " << FileName;
 341       WithColor::error() << "input module is broken!\n";
 342       return false;
 343     }
 344
 345     Function *F = SrcModule.getFunction(FunctionName);
 346     if (!F) {
 347       errs() << "Ignoring import request for non-existent function "
 348              << FunctionName << " from " << FileName << "\n";
 349       continue;
 350     }
 351     // We cannot import weak_any functions without possibly affecting the
 352     // order they are seen and selected by the linker, changing program
 353     // semantics.
 354     if (F->hasWeakAnyLinkage()) {
 355       errs() << "Ignoring import request for weak-any function " << FunctionName
 356              << " from " << FileName << "\n";
 357       continue;
 358     }
 359
 360     if (Verbose)
 361       errs() << "Importing " << FunctionName << " from " << FileName << "\n";
 362
 363     auto &Entry = ImportList[FileName];
 364     Entry.insert(F->getGUID());
 365   }
 366   auto CachedModuleLoader = [&](StringRef Identifier) {
 367     return ModuleLoaderCache.takeModule(std::string(Identifier));
 368   };
 369   FunctionImporter Importer(*Index, CachedModuleLoader,
 370                             /*ClearDSOLocalOnDeclarations=*/false);
 371   ExitOnErr(Importer.importFunctions(DestModule, ImportList));
 372
 373   return true;
 374 }
 375
 376 static bool linkFiles(const char *argv0, LLVMContext &Context, Linker &L,
 377                       const cl::list<std::string> &Files, unsigned Flags) {
 378   // Filter out flags that don't apply to the first file we load.
 379   unsigned ApplicableFlags = Flags & Linker::Flags::OverrideFromSrc;
 380   // Similar to some flags, internalization doesn't apply to the first file.
 381   bool InternalizeLinkedSymbols = false;
 382   for (const auto &File : Files) {
 383     std::unique_ptr<MemoryBuffer> Buffer =
 384         ExitOnErr(errorOrToExpected(MemoryBuffer::getFileOrSTDIN(File)));
 385
 386     std::unique_ptr<Module> M =
 387         identify_magic(Buffer->getBuffer()) == file_magic::archive
 388             ? loadArFile(argv0, std::move(Buffer), Context)
 389             : loadFile(argv0, std::move(Buffer), Context);
 390     if (!M.get()) {
 391       errs() << argv0 << ": ";
 392       WithColor::error() << " loading file '" << File << "'\n";
 393       return false;
 394     }
 395
 396     // Note that when ODR merging types cannot verify input files in here When
 397     // doing that debug metadata in the src module might already be pointing to
 398     // the destination.
 399     if (DisableDITypeMap && !NoVerify && verifyModule(*M, &errs())) {
 400       errs() << argv0 << ": " << File << ": ";
 401       WithColor::error() << "input module is broken!\n";
 402       return false;
 403     }
 404
 405     // If a module summary index is supplied, load it so linkInModule can treat
 406     // local functions/variables as exported and promote if necessary.
 407     if (!SummaryIndex.empty()) {
 408       std::unique_ptr<ModuleSummaryIndex> Index =
 409           ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex));
 410
 411       // Conservatively mark all internal values as promoted, since this tool
 412       // does not do the ThinLink that would normally determine what values to
 413       // promote.
 414       for (auto &I : *Index) {
 415         for (auto &S : I.second.SummaryList) {
 416           if (GlobalValue::isLocalLinkage(S->linkage()))
 417             S->setLinkage(GlobalValue::ExternalLinkage);
 418         }
 419       }
 420
 421       // Promotion
 422       if (renameModuleForThinLTO(*M, *Index,
 423                                  /*ClearDSOLocalOnDeclarations=*/false))
 424         return true;
 425     }
 426
 427     if (Verbose)
 428       errs() << "Linking in '" << File << "'\n";
 429
 430     bool Err = false;
 431     if (InternalizeLinkedSymbols) {
 432       Err = L.linkInModule(
 433           std::move(M), ApplicableFlags, [](Module &M, const StringSet<> &GVS) {
 434             internalizeModule(M, [&GVS](const GlobalValue &GV) {
 435               return !GV.hasName() || (GVS.count(GV.getName()) == 0);
 436             });
 437           });
 438     } else {
 439       Err = L.linkInModule(std::move(M), ApplicableFlags);
 440     }
 441
 442     if (Err)
 443       return false;
 444
 445     // Internalization applies to linking of subsequent files.
 446     InternalizeLinkedSymbols = Internalize;
 447
 448     // All linker flags apply to linking of subsequent files.
 449     ApplicableFlags = Flags;
 450   }
 451
 452   return true;
 453 }
 454
 455 int main(int argc, char **argv) {
 456   InitLLVM X(argc, argv);
 457   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
 458
 459   LLVMContext Context;
 460   Context.setDiagnosticHandler(std::make_unique<LLVMLinkDiagnosticHandler>(),
 461                                true);
 462   cl::HideUnrelatedOptions({&LinkCategory, &getColorCategory()});
 463   cl::ParseCommandLineOptions(argc, argv, "llvm linker\n");
 464
 465   if (!DisableDITypeMap)
 466     Context.enableDebugTypeODRUniquing();
 467
 468   auto Composite = std::make_unique<Module>("llvm-link", Context);
 469   Linker L(*Composite);
 470
 471   unsigned Flags = Linker::Flags::None;
 472   if (OnlyNeeded)
 473     Flags |= Linker::Flags::LinkOnlyNeeded;
 474
 475   // First add all the regular input files
 476   if (!linkFiles(argv[0], Context, L, InputFilenames, Flags))
 477     return 1;
 478
 479   // Next the -override ones.
 480   if (!linkFiles(argv[0], Context, L, OverridingInputs,
 481                  Flags | Linker::Flags::OverrideFromSrc))
 482     return 1;
 483
 484   // Import any functions requested via -import
 485   if (!importFunctions(argv[0], *Composite))
 486     return 1;
 487
 488   if (DumpAsm)
 489     errs() << "Here's the assembly:\n" << *Composite;
 490
 491   std::error_code EC;
 492   ToolOutputFile Out(OutputFilename, EC,
 493                      OutputAssembly ? sys::fs::OF_TextWithCRLF
 494                                     : sys::fs::OF_None);
 495   if (EC) {
 496     WithColor::error() << EC.message() << '\n';
 497     return 1;
 498   }
 499
 500   if (!NoVerify && verifyModule(*Composite, &errs())) {
 501     errs() << argv[0] << ": ";
 502     WithColor::error() << "linked module is broken!\n";
 503     return 1;
 504   }
 505
 506   if (Verbose)
 507     errs() << "Writing bitcode...\n";
 508   if (OutputAssembly) {
 509     Composite->print(Out.os(), nullptr, PreserveAssemblyUseListOrder);
 510   } else if (Force || !CheckBitcodeOutputToConsole(Out.os()))
 511     WriteBitcodeToFile(*Composite, Out.os(), PreserveBitcodeUseListOrder);
 512
 513   // Declare success.
 514   Out.keep();
 515
 516   return 0;
 517 }