tools/llvm-link/llvm-link.cpp

   1 //===- llvm-link.cpp - Low-level LLVM linker ------------------------------===//
   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 utility may be invoked in the following manner:
  11 //  llvm-link a.bc b.bc c.bc -o x.bc
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  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 namespace {
 144
 145 /// Helper to load on demand a Module from file and cache it for subsequent
 146 /// queries during function importing.
 147 class ModuleLazyLoaderCache {
 148   /// Cache of lazily loaded module for import.
 149   StringMap<std::unique_ptr<Module>> ModuleMap;
 150
 151   /// Retrieve a Module from the cache or lazily load it on demand.
 152   std::function<std::unique_ptr<Module>(const char *argv0,
 153                                         const std::string &FileName)>
 154       createLazyModule;
 155
 156 public:
 157   /// Create the loader, Module will be initialized in \p Context.
 158   ModuleLazyLoaderCache(std::function<std::unique_ptr<Module>(
 159                             const char *argv0, const std::string &FileName)>
 160                             createLazyModule)
 161       : createLazyModule(std::move(createLazyModule)) {}
 162
 163   /// Retrieve a Module from the cache or lazily load it on demand.
 164   Module &operator()(const char *argv0, const std::string &FileName);
 165
 166   std::unique_ptr<Module> takeModule(const std::string &FileName) {
 167     auto I = ModuleMap.find(FileName);
 168     assert(I != ModuleMap.end());
 169     std::unique_ptr<Module> Ret = std::move(I->second);
 170     ModuleMap.erase(I);
 171     return Ret;
 172   }
 173 };
 174
 175 // Get a Module for \p FileName from the cache, or load it lazily.
 176 Module &ModuleLazyLoaderCache::operator()(const char *argv0,
 177                                           const std::string &Identifier) {
 178   auto &Module = ModuleMap[Identifier];
 179   if (!Module)
 180     Module = createLazyModule(argv0, Identifier);
 181   return *Module;
 182 }
 183 } // anonymous namespace
 184
 185 namespace {
 186 struct LLVMLinkDiagnosticHandler : public DiagnosticHandler {
 187   bool handleDiagnostics(const DiagnosticInfo &DI) override {
 188     unsigned Severity = DI.getSeverity();
 189     switch (Severity) {
 190     case DS_Error:
 191       WithColor::error();
 192       break;
 193     case DS_Warning:
 194       if (SuppressWarnings)
 195         return true;
 196       WithColor::warning();
 197       break;
 198     case DS_Remark:
 199     case DS_Note:
 200       llvm_unreachable("Only expecting warnings and errors");
 201     }
 202
 203     DiagnosticPrinterRawOStream DP(errs());
 204     DI.print(DP);
 205     errs() << '\n';
 206     return true;
 207   }
 208 };
 209 }
 210
 211 /// Import any functions requested via the -import option.
 212 static bool importFunctions(const char *argv0, Module &DestModule) {
 213   if (SummaryIndex.empty())
 214     return true;
 215   std::unique_ptr<ModuleSummaryIndex> Index =
 216       ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex));
 217
 218   // Map of Module -> List of globals to import from the Module
 219   FunctionImporter::ImportMapTy ImportList;
 220
 221   auto ModuleLoader = [&DestModule](const char *argv0,
 222                                     const std::string &Identifier) {
 223     return loadFile(argv0, Identifier, DestModule.getContext(), false);
 224   };
 225
 226   ModuleLazyLoaderCache ModuleLoaderCache(ModuleLoader);
 227   for (const auto &Import : Imports) {
 228     // Identify the requested function and its bitcode source file.
 229     size_t Idx = Import.find(':');
 230     if (Idx == std::string::npos) {
 231       errs() << "Import parameter bad format: " << Import << "\n";
 232       return false;
 233     }
 234     std::string FunctionName = Import.substr(0, Idx);
 235     std::string FileName = Import.substr(Idx + 1, std::string::npos);
 236
 237     // Load the specified source module.
 238     auto &SrcModule = ModuleLoaderCache(argv0, FileName);
 239
 240     if (verifyModule(SrcModule, &errs())) {
 241       errs() << argv0 << ": " << FileName;
 242       WithColor::error() << "input module is broken!\n";
 243       return false;
 244     }
 245
 246     Function *F = SrcModule.getFunction(FunctionName);
 247     if (!F) {
 248       errs() << "Ignoring import request for non-existent function "
 249              << FunctionName << " from " << FileName << "\n";
 250       continue;
 251     }
 252     // We cannot import weak_any functions without possibly affecting the
 253     // order they are seen and selected by the linker, changing program
 254     // semantics.
 255     if (F->hasWeakAnyLinkage()) {
 256       errs() << "Ignoring import request for weak-any function " << FunctionName
 257              << " from " << FileName << "\n";
 258       continue;
 259     }
 260
 261     if (Verbose)
 262       errs() << "Importing " << FunctionName << " from " << FileName << "\n";
 263
 264     auto &Entry = ImportList[FileName];
 265     Entry.insert(F->getGUID());
 266   }
 267   auto CachedModuleLoader = [&](StringRef Identifier) {
 268     return ModuleLoaderCache.takeModule(Identifier);
 269   };
 270   FunctionImporter Importer(*Index, CachedModuleLoader);
 271   ExitOnErr(Importer.importFunctions(DestModule, ImportList));
 272
 273   return true;
 274 }
 275
 276 static bool linkFiles(const char *argv0, LLVMContext &Context, Linker &L,
 277                       const cl::list<std::string> &Files,
 278                       unsigned Flags) {
 279   // Filter out flags that don't apply to the first file we load.
 280   unsigned ApplicableFlags = Flags & Linker::Flags::OverrideFromSrc;
 281   // Similar to some flags, internalization doesn't apply to the first file.
 282   bool InternalizeLinkedSymbols = false;
 283   for (const auto &File : Files) {
 284     std::unique_ptr<Module> M = loadFile(argv0, File, Context);
 285     if (!M.get()) {
 286       errs() << argv0 << ": ";
 287       WithColor::error() << " loading file '" << File << "'\n";
 288       return false;
 289     }
 290
 291     // Note that when ODR merging types cannot verify input files in here When
 292     // doing that debug metadata in the src module might already be pointing to
 293     // the destination.
 294     if (DisableDITypeMap && verifyModule(*M, &errs())) {
 295       errs() << argv0 << ": " << File << ": ";
 296       WithColor::error() << "input module is broken!\n";
 297       return false;
 298     }
 299
 300     // If a module summary index is supplied, load it so linkInModule can treat
 301     // local functions/variables as exported and promote if necessary.
 302     if (!SummaryIndex.empty()) {
 303       std::unique_ptr<ModuleSummaryIndex> Index =
 304           ExitOnErr(llvm::getModuleSummaryIndexForFile(SummaryIndex));
 305
 306       // Conservatively mark all internal values as promoted, since this tool
 307       // does not do the ThinLink that would normally determine what values to
 308       // promote.
 309       for (auto &I : *Index) {
 310         for (auto &S : I.second.SummaryList) {
 311           if (GlobalValue::isLocalLinkage(S->linkage()))
 312             S->setLinkage(GlobalValue::ExternalLinkage);
 313         }
 314       }
 315
 316       // Promotion
 317       if (renameModuleForThinLTO(*M, *Index))
 318         return true;
 319     }
 320
 321     if (Verbose)
 322       errs() << "Linking in '" << File << "'\n";
 323
 324     bool Err = false;
 325     if (InternalizeLinkedSymbols) {
 326       Err = L.linkInModule(
 327           std::move(M), ApplicableFlags, [](Module &M, const StringSet<> &GVS) {
 328             internalizeModule(M, [&GVS](const GlobalValue &GV) {
 329               return !GV.hasName() || (GVS.count(GV.getName()) == 0);
 330             });
 331           });
 332     } else {
 333       Err = L.linkInModule(std::move(M), ApplicableFlags);
 334     }
 335
 336     if (Err)
 337       return false;
 338
 339     // Internalization applies to linking of subsequent files.
 340     InternalizeLinkedSymbols = Internalize;
 341
 342     // All linker flags apply to linking of subsequent files.
 343     ApplicableFlags = Flags;
 344   }
 345
 346   return true;
 347 }
 348
 349 int main(int argc, char **argv) {
 350   InitLLVM X(argc, argv);
 351   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
 352
 353   LLVMContext Context;
 354   Context.setDiagnosticHandler(
 355     llvm::make_unique<LLVMLinkDiagnosticHandler>(), true);
 356   cl::ParseCommandLineOptions(argc, argv, "llvm linker\n");
 357
 358   if (!DisableDITypeMap)
 359     Context.enableDebugTypeODRUniquing();
 360
 361   auto Composite = make_unique<Module>("llvm-link", Context);
 362   Linker L(*Composite);
 363
 364   unsigned Flags = Linker::Flags::None;
 365   if (OnlyNeeded)
 366     Flags |= Linker::Flags::LinkOnlyNeeded;
 367
 368   // First add all the regular input files
 369   if (!linkFiles(argv[0], Context, L, InputFilenames, Flags))
 370     return 1;
 371
 372   // Next the -override ones.
 373   if (!linkFiles(argv[0], Context, L, OverridingInputs,
 374                  Flags | Linker::Flags::OverrideFromSrc))
 375     return 1;
 376
 377   // Import any functions requested via -import
 378   if (!importFunctions(argv[0], *Composite))
 379     return 1;
 380
 381   if (DumpAsm)
 382     errs() << "Here's the assembly:\n" << *Composite;
 383
 384   std::error_code EC;
 385   ToolOutputFile Out(OutputFilename, EC, sys::fs::F_None);
 386   if (EC) {
 387     WithColor::error() << EC.message() << '\n';
 388     return 1;
 389   }
 390
 391   if (verifyModule(*Composite, &errs())) {
 392     errs() << argv[0] << ": ";
 393     WithColor::error() << "linked module is broken!\n";
 394     return 1;
 395   }
 396
 397   if (Verbose)
 398     errs() << "Writing bitcode...\n";
 399   if (OutputAssembly) {
 400     Composite->print(Out.os(), nullptr, PreserveAssemblyUseListOrder);
 401   } else if (Force || !CheckBitcodeOutputToConsole(Out.os(), true))
 402     WriteBitcodeToFile(*Composite, Out.os(), PreserveBitcodeUseListOrder);
 403
 404   // Declare success.
 405   Out.keep();
 406
 407   return 0;
 408 }