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 //
loadFile(const char * argv0,const std::string & FN,LLVMContext & Context,bool MaterializeMetadata=true)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.
ModuleLazyLoaderCache(std::function<std::unique_ptr<Module> (const char * argv0,const std::string & FileName)> createLazyModule)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
takeModule(const std::string & FileName)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.
operator ()(const char * argv0,const std::string & Identifier)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 {
handleDiagnostics__anon144c7e4a0211::LLVMLinkDiagnosticHandler187 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.
importFunctions(const char * argv0,Module & DestModule)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
linkFiles(const char * argv0,LLVMContext & Context,Linker & L,const cl::list<std::string> & Files,unsigned Flags)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
main(int argc,char ** argv)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 }
409