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/ReaderWriter.h"
17 #include "llvm/IR/AutoUpgrade.h"
18 #include "llvm/IR/DiagnosticInfo.h"
19 #include "llvm/IR/DiagnosticPrinter.h"
20 #include "llvm/IR/LLVMContext.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/IR/ModuleSummaryIndex.h"
23 #include "llvm/IR/Verifier.h"
24 #include "llvm/IRReader/IRReader.h"
25 #include "llvm/Linker/Linker.h"
26 #include "llvm/Object/ModuleSummaryIndexObjectFile.h"
27 #include "llvm/Support/CommandLine.h"
28 #include "llvm/Support/FileSystem.h"
29 #include "llvm/Support/ManagedStatic.h"
30 #include "llvm/Support/Path.h"
31 #include "llvm/Support/PrettyStackTrace.h"
32 #include "llvm/Support/Signals.h"
33 #include "llvm/Support/SourceMgr.h"
34 #include "llvm/Support/SystemUtils.h"
35 #include "llvm/Support/ToolOutputFile.h"
36 #include "llvm/Transforms/Utils/FunctionImportUtils.h"
37
38 #include <memory>
39 #include <utility>
40 using namespace llvm;
41
42 static cl::list<std::string>
43 InputFilenames(cl::Positional, cl::OneOrMore,
44 cl::desc("<input bitcode files>"));
45
46 static cl::list<std::string> OverridingInputs(
47 "override", cl::ZeroOrMore, cl::value_desc("filename"),
48 cl::desc(
49 "input bitcode file which can override previously defined symbol(s)"));
50
51 // Option to simulate function importing for testing. This enables using
52 // llvm-link to simulate ThinLTO backend processes.
53 static cl::list<std::string> Imports(
54 "import", cl::ZeroOrMore, cl::value_desc("function:filename"),
55 cl::desc("Pair of function name and filename, where function should be "
56 "imported from bitcode in filename"));
57
58 // Option to support testing of function importing. The module summary
59 // must be specified in the case were we request imports via the -import
60 // option, as well as when compiling any module with functions that may be
61 // exported (imported by a different llvm-link -import invocation), to ensure
62 // consistent promotion and renaming of locals.
63 static cl::opt<std::string>
64 SummaryIndex("summary-index", cl::desc("Module summary index filename"),
65 cl::init(""), cl::value_desc("filename"));
66
67 static cl::opt<std::string>
68 OutputFilename("o", cl::desc("Override output filename"), cl::init("-"),
69 cl::value_desc("filename"));
70
71 static cl::opt<bool>
72 Internalize("internalize", cl::desc("Internalize linked symbols"));
73
74 static cl::opt<bool>
75 DisableDITypeMap("disable-debug-info-type-map",
76 cl::desc("Don't use a uniquing type map for debug info"));
77
78 static cl::opt<bool>
79 OnlyNeeded("only-needed", cl::desc("Link only needed symbols"));
80
81 static cl::opt<bool>
82 Force("f", cl::desc("Enable binary output on terminals"));
83
84 static cl::opt<bool>
85 OutputAssembly("S",
86 cl::desc("Write output as LLVM assembly"), cl::Hidden);
87
88 static cl::opt<bool>
89 Verbose("v", cl::desc("Print information about actions taken"));
90
91 static cl::opt<bool>
92 DumpAsm("d", cl::desc("Print assembly as linked"), cl::Hidden);
93
94 static cl::opt<bool>
95 SuppressWarnings("suppress-warnings", cl::desc("Suppress all linking warnings"),
96 cl::init(false));
97
98 static cl::opt<bool> PreserveBitcodeUseListOrder(
99 "preserve-bc-uselistorder",
100 cl::desc("Preserve use-list order when writing LLVM bitcode."),
101 cl::init(true), cl::Hidden);
102
103 static cl::opt<bool> PreserveAssemblyUseListOrder(
104 "preserve-ll-uselistorder",
105 cl::desc("Preserve use-list order when writing LLVM assembly."),
106 cl::init(false), cl::Hidden);
107
108 // Read the specified bitcode file in and return it. This routine searches the
109 // link path for the specified file to try to find it...
110 //
loadFile(const char * argv0,const std::string & FN,LLVMContext & Context,bool MaterializeMetadata=true)111 static std::unique_ptr<Module> loadFile(const char *argv0,
112 const std::string &FN,
113 LLVMContext &Context,
114 bool MaterializeMetadata = true) {
115 SMDiagnostic Err;
116 if (Verbose) errs() << "Loading '" << FN << "'\n";
117 std::unique_ptr<Module> Result =
118 getLazyIRFileModule(FN, Err, Context, !MaterializeMetadata);
119 if (!Result) {
120 Err.print(argv0, errs());
121 return nullptr;
122 }
123
124 if (MaterializeMetadata) {
125 Result->materializeMetadata();
126 UpgradeDebugInfo(*Result);
127 }
128
129 return Result;
130 }
131
132 namespace {
133
134 /// Helper to load on demand a Module from file and cache it for subsequent
135 /// queries during function importing.
136 class ModuleLazyLoaderCache {
137 /// Cache of lazily loaded module for import.
138 StringMap<std::unique_ptr<Module>> ModuleMap;
139
140 /// Retrieve a Module from the cache or lazily load it on demand.
141 std::function<std::unique_ptr<Module>(const char *argv0,
142 const std::string &FileName)>
143 createLazyModule;
144
145 public:
146 /// 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)147 ModuleLazyLoaderCache(std::function<std::unique_ptr<Module>(
148 const char *argv0, const std::string &FileName)>
149 createLazyModule)
150 : createLazyModule(std::move(createLazyModule)) {}
151
152 /// Retrieve a Module from the cache or lazily load it on demand.
153 Module &operator()(const char *argv0, const std::string &FileName);
154
takeModule(const std::string & FileName)155 std::unique_ptr<Module> takeModule(const std::string &FileName) {
156 auto I = ModuleMap.find(FileName);
157 assert(I != ModuleMap.end());
158 std::unique_ptr<Module> Ret = std::move(I->second);
159 ModuleMap.erase(I);
160 return Ret;
161 }
162 };
163
164 // Get a Module for \p FileName from the cache, or load it lazily.
operator ()(const char * argv0,const std::string & Identifier)165 Module &ModuleLazyLoaderCache::operator()(const char *argv0,
166 const std::string &Identifier) {
167 auto &Module = ModuleMap[Identifier];
168 if (!Module)
169 Module = createLazyModule(argv0, Identifier);
170 return *Module;
171 }
172 } // anonymous namespace
173
diagnosticHandler(const DiagnosticInfo & DI)174 static void diagnosticHandler(const DiagnosticInfo &DI) {
175 unsigned Severity = DI.getSeverity();
176 switch (Severity) {
177 case DS_Error:
178 errs() << "ERROR: ";
179 break;
180 case DS_Warning:
181 if (SuppressWarnings)
182 return;
183 errs() << "WARNING: ";
184 break;
185 case DS_Remark:
186 case DS_Note:
187 llvm_unreachable("Only expecting warnings and errors");
188 }
189
190 DiagnosticPrinterRawOStream DP(errs());
191 DI.print(DP);
192 errs() << '\n';
193 }
194
diagnosticHandlerWithContext(const DiagnosticInfo & DI,void * C)195 static void diagnosticHandlerWithContext(const DiagnosticInfo &DI, void *C) {
196 diagnosticHandler(DI);
197 }
198
199 /// Import any functions requested via the -import option.
importFunctions(const char * argv0,LLVMContext & Context,Linker & L)200 static bool importFunctions(const char *argv0, LLVMContext &Context,
201 Linker &L) {
202 if (SummaryIndex.empty())
203 return true;
204 ErrorOr<std::unique_ptr<ModuleSummaryIndex>> IndexOrErr =
205 llvm::getModuleSummaryIndexForFile(SummaryIndex, diagnosticHandler);
206 std::error_code EC = IndexOrErr.getError();
207 if (EC) {
208 errs() << EC.message() << '\n';
209 return false;
210 }
211 auto Index = std::move(IndexOrErr.get());
212
213 // Map of Module -> List of globals to import from the Module
214 std::map<StringRef, DenseSet<const GlobalValue *>> ModuleToGlobalsToImportMap;
215 auto ModuleLoader = [&Context](const char *argv0,
216 const std::string &Identifier) {
217 return loadFile(argv0, Identifier, Context, false);
218 };
219 ModuleLazyLoaderCache ModuleLoaderCache(ModuleLoader);
220 for (const auto &Import : Imports) {
221 // Identify the requested function and its bitcode source file.
222 size_t Idx = Import.find(':');
223 if (Idx == std::string::npos) {
224 errs() << "Import parameter bad format: " << Import << "\n";
225 return false;
226 }
227 std::string FunctionName = Import.substr(0, Idx);
228 std::string FileName = Import.substr(Idx + 1, std::string::npos);
229
230 // Load the specified source module.
231 auto &SrcModule = ModuleLoaderCache(argv0, FileName);
232
233 if (verifyModule(SrcModule, &errs())) {
234 errs() << argv0 << ": " << FileName
235 << ": error: input module is broken!\n";
236 return false;
237 }
238
239 Function *F = SrcModule.getFunction(FunctionName);
240 if (!F) {
241 errs() << "Ignoring import request for non-existent function "
242 << FunctionName << " from " << FileName << "\n";
243 continue;
244 }
245 // We cannot import weak_any functions without possibly affecting the
246 // order they are seen and selected by the linker, changing program
247 // semantics.
248 if (F->hasWeakAnyLinkage()) {
249 errs() << "Ignoring import request for weak-any function " << FunctionName
250 << " from " << FileName << "\n";
251 continue;
252 }
253
254 if (Verbose)
255 errs() << "Importing " << FunctionName << " from " << FileName << "\n";
256
257 auto &Entry = ModuleToGlobalsToImportMap[SrcModule.getModuleIdentifier()];
258 Entry.insert(F);
259
260 F->materialize();
261 }
262
263 // Do the actual import of globals now, one Module at a time
264 for (auto &GlobalsToImportPerModule : ModuleToGlobalsToImportMap) {
265 // Get the module for the import
266 auto &GlobalsToImport = GlobalsToImportPerModule.second;
267 std::unique_ptr<Module> SrcModule =
268 ModuleLoaderCache.takeModule(GlobalsToImportPerModule.first);
269 assert(&Context == &SrcModule->getContext() && "Context mismatch");
270
271 // If modules were created with lazy metadata loading, materialize it
272 // now, before linking it (otherwise this will be a noop).
273 SrcModule->materializeMetadata();
274 UpgradeDebugInfo(*SrcModule);
275
276 // Linkage Promotion and renaming
277 if (renameModuleForThinLTO(*SrcModule, *Index, &GlobalsToImport))
278 return true;
279
280 // Instruct the linker to not automatically import linkonce defintion.
281 unsigned Flags = Linker::Flags::DontForceLinkLinkonceODR;
282
283 if (L.linkInModule(std::move(SrcModule), Flags, &GlobalsToImport))
284 return false;
285 }
286
287 return true;
288 }
289
linkFiles(const char * argv0,LLVMContext & Context,Linker & L,const cl::list<std::string> & Files,unsigned Flags)290 static bool linkFiles(const char *argv0, LLVMContext &Context, Linker &L,
291 const cl::list<std::string> &Files,
292 unsigned Flags) {
293 // Filter out flags that don't apply to the first file we load.
294 unsigned ApplicableFlags = Flags & Linker::Flags::OverrideFromSrc;
295 for (const auto &File : Files) {
296 std::unique_ptr<Module> M = loadFile(argv0, File, Context);
297 if (!M.get()) {
298 errs() << argv0 << ": error loading file '" << File << "'\n";
299 return false;
300 }
301
302 // Note that when ODR merging types cannot verify input files in here When
303 // doing that debug metadata in the src module might already be pointing to
304 // the destination.
305 if (DisableDITypeMap && verifyModule(*M, &errs())) {
306 errs() << argv0 << ": " << File << ": error: input module is broken!\n";
307 return false;
308 }
309
310 // If a module summary index is supplied, load it so linkInModule can treat
311 // local functions/variables as exported and promote if necessary.
312 if (!SummaryIndex.empty()) {
313 ErrorOr<std::unique_ptr<ModuleSummaryIndex>> IndexOrErr =
314 llvm::getModuleSummaryIndexForFile(SummaryIndex, diagnosticHandler);
315 std::error_code EC = IndexOrErr.getError();
316 if (EC) {
317 errs() << EC.message() << '\n';
318 return false;
319 }
320 auto Index = std::move(IndexOrErr.get());
321
322 // Promotion
323 if (renameModuleForThinLTO(*M, *Index))
324 return true;
325 }
326
327 if (Verbose)
328 errs() << "Linking in '" << File << "'\n";
329
330 if (L.linkInModule(std::move(M), ApplicableFlags))
331 return false;
332 // All linker flags apply to linking of subsequent files.
333 ApplicableFlags = Flags;
334 }
335
336 return true;
337 }
338
main(int argc,char ** argv)339 int main(int argc, char **argv) {
340 // Print a stack trace if we signal out.
341 sys::PrintStackTraceOnErrorSignal(argv[0]);
342 PrettyStackTraceProgram X(argc, argv);
343
344 LLVMContext Context;
345 Context.setDiagnosticHandler(diagnosticHandlerWithContext, nullptr, true);
346
347 llvm_shutdown_obj Y; // Call llvm_shutdown() on exit.
348 cl::ParseCommandLineOptions(argc, argv, "llvm linker\n");
349
350 if (!DisableDITypeMap)
351 Context.enableDebugTypeODRUniquing();
352
353 auto Composite = make_unique<Module>("llvm-link", Context);
354 Linker L(*Composite);
355
356 unsigned Flags = Linker::Flags::None;
357 if (Internalize)
358 Flags |= Linker::Flags::InternalizeLinkedSymbols;
359 if (OnlyNeeded)
360 Flags |= Linker::Flags::LinkOnlyNeeded;
361
362 // First add all the regular input files
363 if (!linkFiles(argv[0], Context, L, InputFilenames, Flags))
364 return 1;
365
366 // Next the -override ones.
367 if (!linkFiles(argv[0], Context, L, OverridingInputs,
368 Flags | Linker::Flags::OverrideFromSrc))
369 return 1;
370
371 // Import any functions requested via -import
372 if (!importFunctions(argv[0], Context, L))
373 return 1;
374
375 if (DumpAsm) errs() << "Here's the assembly:\n" << *Composite;
376
377 std::error_code EC;
378 tool_output_file Out(OutputFilename, EC, sys::fs::F_None);
379 if (EC) {
380 errs() << EC.message() << '\n';
381 return 1;
382 }
383
384 if (verifyModule(*Composite, &errs())) {
385 errs() << argv[0] << ": error: linked module is broken!\n";
386 return 1;
387 }
388
389 if (Verbose) errs() << "Writing bitcode...\n";
390 if (OutputAssembly) {
391 Composite->print(Out.os(), nullptr, PreserveAssemblyUseListOrder);
392 } else if (Force || !CheckBitcodeOutputToConsole(Out.os(), true))
393 WriteBitcodeToFile(Composite.get(), Out.os(), PreserveBitcodeUseListOrder);
394
395 // Declare success.
396 Out.keep();
397
398 return 0;
399 }
400