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 //
loadFile(const char * argv0,std::unique_ptr<MemoryBuffer> Buffer,LLVMContext & Context,bool MaterializeMetadata=true)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
loadArFile(const char * Argv0,std::unique_ptr<MemoryBuffer> Buffer,LLVMContext & Context)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.
ModuleLazyLoaderCache(std::function<std::unique_ptr<Module> (const char * argv0,const std::string & FileName)> createLazyModule)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
takeModule(const std::string & FileName)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.
operator ()(const char * argv0,const std::string & Identifier)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 {
handleDiagnostics__anon0db55a7c0211::LLVMLinkDiagnosticHandler284 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.
importFunctions(const char * argv0,Module & DestModule)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
linkFiles(const char * argv0,LLVMContext & Context,Linker & L,const cl::list<std::string> & Files,unsigned Flags)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
main(int argc,char ** argv)455 int main(int argc, char **argv) {
456 InitLLVM X(argc, argv);
457 ExitOnErr.setBanner(std::string(argv[0]) + ": ");
458
459 cl::HideUnrelatedOptions({&LinkCategory, &getColorCategory()});
460 cl::ParseCommandLineOptions(argc, argv, "llvm linker\n");
461
462 LLVMContext Context;
463 Context.setDiagnosticHandler(std::make_unique<LLVMLinkDiagnosticHandler>(),
464 true);
465
466 if (!DisableDITypeMap)
467 Context.enableDebugTypeODRUniquing();
468
469 auto Composite = std::make_unique<Module>("llvm-link", Context);
470 Linker L(*Composite);
471
472 unsigned Flags = Linker::Flags::None;
473 if (OnlyNeeded)
474 Flags |= Linker::Flags::LinkOnlyNeeded;
475
476 // First add all the regular input files
477 if (!linkFiles(argv[0], Context, L, InputFilenames, Flags))
478 return 1;
479
480 // Next the -override ones.
481 if (!linkFiles(argv[0], Context, L, OverridingInputs,
482 Flags | Linker::Flags::OverrideFromSrc))
483 return 1;
484
485 // Import any functions requested via -import
486 if (!importFunctions(argv[0], *Composite))
487 return 1;
488
489 if (DumpAsm)
490 errs() << "Here's the assembly:\n" << *Composite;
491
492 std::error_code EC;
493 ToolOutputFile Out(OutputFilename, EC,
494 OutputAssembly ? sys::fs::OF_TextWithCRLF
495 : sys::fs::OF_None);
496 if (EC) {
497 WithColor::error() << EC.message() << '\n';
498 return 1;
499 }
500
501 if (!NoVerify && verifyModule(*Composite, &errs())) {
502 errs() << argv[0] << ": ";
503 WithColor::error() << "linked module is broken!\n";
504 return 1;
505 }
506
507 if (Verbose)
508 errs() << "Writing bitcode...\n";
509 if (OutputAssembly) {
510 Composite->print(Out.os(), nullptr, PreserveAssemblyUseListOrder);
511 } else if (Force || !CheckBitcodeOutputToConsole(Out.os()))
512 WriteBitcodeToFile(*Composite, Out.os(), PreserveBitcodeUseListOrder);
513
514 // Declare success.
515 Out.keep();
516
517 return 0;
518 }
519