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/Linker/Linker.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/Bitcode/ReaderWriter.h"
18 #include "llvm/IR/AutoUpgrade.h"
19 #include "llvm/IR/DiagnosticInfo.h"
20 #include "llvm/IR/DiagnosticPrinter.h"
21 #include "llvm/IR/FunctionInfo.h"
22 #include "llvm/IR/LLVMContext.h"
23 #include "llvm/IR/Module.h"
24 #include "llvm/IR/Verifier.h"
25 #include "llvm/IRReader/IRReader.h"
26 #include "llvm/Object/FunctionIndexObjectFile.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 <memory>
37 using namespace llvm;
38
39 static cl::list<std::string>
40 InputFilenames(cl::Positional, cl::OneOrMore,
41 cl::desc("<input bitcode files>"));
42
43 static cl::list<std::string> OverridingInputs(
44 "override", cl::ZeroOrMore, cl::value_desc("filename"),
45 cl::desc(
46 "input bitcode file which can override previously defined symbol(s)"));
47
48 // Option to simulate function importing for testing. This enables using
49 // llvm-link to simulate ThinLTO backend processes.
50 static cl::list<std::string> Imports(
51 "import", cl::ZeroOrMore, cl::value_desc("function:filename"),
52 cl::desc("Pair of function name and filename, where function should be "
53 "imported from bitcode in filename"));
54
55 // Option to support testing of function importing. The function index
56 // must be specified in the case were we request imports via the -import
57 // option, as well as when compiling any module with functions that may be
58 // exported (imported by a different llvm-link -import invocation), to ensure
59 // consistent promotion and renaming of locals.
60 static cl::opt<std::string> FunctionIndex("functionindex",
61 cl::desc("Function index filename"),
62 cl::init(""),
63 cl::value_desc("filename"));
64
65 static cl::opt<std::string>
66 OutputFilename("o", cl::desc("Override output filename"), cl::init("-"),
67 cl::value_desc("filename"));
68
69 static cl::opt<bool>
70 Internalize("internalize", cl::desc("Internalize linked symbols"));
71
72 static cl::opt<bool>
73 OnlyNeeded("only-needed", cl::desc("Link only needed symbols"));
74
75 static cl::opt<bool>
76 Force("f", cl::desc("Enable binary output on terminals"));
77
78 static cl::opt<bool>
79 OutputAssembly("S",
80 cl::desc("Write output as LLVM assembly"), cl::Hidden);
81
82 static cl::opt<bool>
83 Verbose("v", cl::desc("Print information about actions taken"));
84
85 static cl::opt<bool>
86 DumpAsm("d", cl::desc("Print assembly as linked"), cl::Hidden);
87
88 static cl::opt<bool>
89 SuppressWarnings("suppress-warnings", cl::desc("Suppress all linking warnings"),
90 cl::init(false));
91
92 static cl::opt<bool>
93 PreserveModules("preserve-modules",
94 cl::desc("Preserve linked modules for testing"));
95
96 static cl::opt<bool> PreserveBitcodeUseListOrder(
97 "preserve-bc-uselistorder",
98 cl::desc("Preserve use-list order when writing LLVM bitcode."),
99 cl::init(true), cl::Hidden);
100
101 static cl::opt<bool> PreserveAssemblyUseListOrder(
102 "preserve-ll-uselistorder",
103 cl::desc("Preserve use-list order when writing LLVM assembly."),
104 cl::init(false), cl::Hidden);
105
106 // Read the specified bitcode file in and return it. This routine searches the
107 // link path for the specified file to try to find it...
108 //
loadFile(const char * argv0,const std::string & FN,LLVMContext & Context,bool MaterializeMetadata=true)109 static std::unique_ptr<Module> loadFile(const char *argv0,
110 const std::string &FN,
111 LLVMContext &Context,
112 bool MaterializeMetadata = true) {
113 SMDiagnostic Err;
114 if (Verbose) errs() << "Loading '" << FN << "'\n";
115 std::unique_ptr<Module> Result =
116 getLazyIRFileModule(FN, Err, Context, !MaterializeMetadata);
117 if (!Result)
118 Err.print(argv0, errs());
119
120 if (MaterializeMetadata) {
121 Result->materializeMetadata();
122 UpgradeDebugInfo(*Result);
123 }
124
125 return Result;
126 }
127
diagnosticHandler(const DiagnosticInfo & DI)128 static void diagnosticHandler(const DiagnosticInfo &DI) {
129 unsigned Severity = DI.getSeverity();
130 switch (Severity) {
131 case DS_Error:
132 errs() << "ERROR: ";
133 break;
134 case DS_Warning:
135 if (SuppressWarnings)
136 return;
137 errs() << "WARNING: ";
138 break;
139 case DS_Remark:
140 case DS_Note:
141 llvm_unreachable("Only expecting warnings and errors");
142 }
143
144 DiagnosticPrinterRawOStream DP(errs());
145 DI.print(DP);
146 errs() << '\n';
147 }
148
diagnosticHandlerWithContext(const DiagnosticInfo & DI,void * C)149 static void diagnosticHandlerWithContext(const DiagnosticInfo &DI, void *C) {
150 diagnosticHandler(DI);
151 }
152
153 /// Import any functions requested via the -import option.
importFunctions(const char * argv0,LLVMContext & Context,Linker & L)154 static bool importFunctions(const char *argv0, LLVMContext &Context,
155 Linker &L) {
156 StringMap<std::unique_ptr<DenseMap<unsigned, MDNode *>>>
157 ModuleToTempMDValsMap;
158 for (const auto &Import : Imports) {
159 // Identify the requested function and its bitcode source file.
160 size_t Idx = Import.find(':');
161 if (Idx == std::string::npos) {
162 errs() << "Import parameter bad format: " << Import << "\n";
163 return false;
164 }
165 std::string FunctionName = Import.substr(0, Idx);
166 std::string FileName = Import.substr(Idx + 1, std::string::npos);
167
168 // Load the specified source module.
169 std::unique_ptr<Module> M = loadFile(argv0, FileName, Context, false);
170 if (!M.get()) {
171 errs() << argv0 << ": error loading file '" << FileName << "'\n";
172 return false;
173 }
174
175 if (verifyModule(*M, &errs())) {
176 errs() << argv0 << ": " << FileName
177 << ": error: input module is broken!\n";
178 return false;
179 }
180
181 Function *F = M->getFunction(FunctionName);
182 if (!F) {
183 errs() << "Ignoring import request for non-existent function "
184 << FunctionName << " from " << FileName << "\n";
185 continue;
186 }
187 // We cannot import weak_any functions without possibly affecting the
188 // order they are seen and selected by the linker, changing program
189 // semantics.
190 if (F->hasWeakAnyLinkage()) {
191 errs() << "Ignoring import request for weak-any function " << FunctionName
192 << " from " << FileName << "\n";
193 continue;
194 }
195
196 if (Verbose)
197 errs() << "Importing " << FunctionName << " from " << FileName << "\n";
198
199 std::unique_ptr<FunctionInfoIndex> Index;
200 if (!FunctionIndex.empty()) {
201 ErrorOr<std::unique_ptr<FunctionInfoIndex>> IndexOrErr =
202 llvm::getFunctionIndexForFile(FunctionIndex, diagnosticHandler);
203 std::error_code EC = IndexOrErr.getError();
204 if (EC) {
205 errs() << EC.message() << '\n';
206 return false;
207 }
208 Index = std::move(IndexOrErr.get());
209 }
210
211 // Save the mapping of value ids to temporary metadata created when
212 // importing this function. If we have already imported from this module,
213 // add new temporary metadata to the existing mapping.
214 auto &TempMDVals = ModuleToTempMDValsMap[FileName];
215 if (!TempMDVals)
216 TempMDVals = llvm::make_unique<DenseMap<unsigned, MDNode *>>();
217
218 // Link in the specified function.
219 DenseSet<const GlobalValue *> FunctionsToImport;
220 FunctionsToImport.insert(F);
221 if (L.linkInModule(std::move(M), Linker::Flags::None, Index.get(),
222 &FunctionsToImport, TempMDVals.get()))
223 return false;
224 }
225
226 // Now link in metadata for all modules from which we imported functions.
227 for (StringMapEntry<std::unique_ptr<DenseMap<unsigned, MDNode *>>> &SME :
228 ModuleToTempMDValsMap) {
229 // Load the specified source module.
230 std::unique_ptr<Module> M = loadFile(argv0, SME.getKey(), Context, true);
231 if (!M.get()) {
232 errs() << argv0 << ": error loading file '" << SME.getKey() << "'\n";
233 return false;
234 }
235
236 if (verifyModule(*M, &errs())) {
237 errs() << argv0 << ": " << SME.getKey()
238 << ": error: input module is broken!\n";
239 return false;
240 }
241
242 // Link in all necessary metadata from this module.
243 if (L.linkInMetadata(*M, SME.getValue().get()))
244 return false;
245 }
246 return true;
247 }
248
linkFiles(const char * argv0,LLVMContext & Context,Linker & L,const cl::list<std::string> & Files,unsigned Flags)249 static bool linkFiles(const char *argv0, LLVMContext &Context, Linker &L,
250 const cl::list<std::string> &Files,
251 unsigned Flags) {
252 // Filter out flags that don't apply to the first file we load.
253 unsigned ApplicableFlags = Flags & Linker::Flags::OverrideFromSrc;
254 for (const auto &File : Files) {
255 std::unique_ptr<Module> M = loadFile(argv0, File, Context);
256 if (!M.get()) {
257 errs() << argv0 << ": error loading file '" << File << "'\n";
258 return false;
259 }
260
261 if (verifyModule(*M, &errs())) {
262 errs() << argv0 << ": " << File << ": error: input module is broken!\n";
263 return false;
264 }
265
266 // If a function index is supplied, load it so linkInModule can treat
267 // local functions/variables as exported and promote if necessary.
268 std::unique_ptr<FunctionInfoIndex> Index;
269 if (!FunctionIndex.empty()) {
270 ErrorOr<std::unique_ptr<FunctionInfoIndex>> IndexOrErr =
271 llvm::getFunctionIndexForFile(FunctionIndex, diagnosticHandler);
272 std::error_code EC = IndexOrErr.getError();
273 if (EC) {
274 errs() << EC.message() << '\n';
275 return false;
276 }
277 Index = std::move(IndexOrErr.get());
278 }
279
280 if (Verbose)
281 errs() << "Linking in '" << File << "'\n";
282
283 if (L.linkInModule(std::move(M), ApplicableFlags, Index.get()))
284 return false;
285 // All linker flags apply to linking of subsequent files.
286 ApplicableFlags = Flags;
287
288 // If requested for testing, preserve modules by releasing them from
289 // the unique_ptr before the are freed. This can help catch any
290 // cross-module references from e.g. unneeded metadata references
291 // that aren't properly set to null but instead mapped to the source
292 // module version. The bitcode writer will assert if it finds any such
293 // cross-module references.
294 if (PreserveModules)
295 M.release();
296 }
297
298 return true;
299 }
300
main(int argc,char ** argv)301 int main(int argc, char **argv) {
302 // Print a stack trace if we signal out.
303 sys::PrintStackTraceOnErrorSignal();
304 PrettyStackTraceProgram X(argc, argv);
305
306 LLVMContext &Context = getGlobalContext();
307 Context.setDiagnosticHandler(diagnosticHandlerWithContext, nullptr, true);
308
309 llvm_shutdown_obj Y; // Call llvm_shutdown() on exit.
310 cl::ParseCommandLineOptions(argc, argv, "llvm linker\n");
311
312 auto Composite = make_unique<Module>("llvm-link", Context);
313 Linker L(*Composite);
314
315 unsigned Flags = Linker::Flags::None;
316 if (Internalize)
317 Flags |= Linker::Flags::InternalizeLinkedSymbols;
318 if (OnlyNeeded)
319 Flags |= Linker::Flags::LinkOnlyNeeded;
320
321 // First add all the regular input files
322 if (!linkFiles(argv[0], Context, L, InputFilenames, Flags))
323 return 1;
324
325 // Next the -override ones.
326 if (!linkFiles(argv[0], Context, L, OverridingInputs,
327 Flags | Linker::Flags::OverrideFromSrc))
328 return 1;
329
330 // Import any functions requested via -import
331 if (!importFunctions(argv[0], Context, L))
332 return 1;
333
334 if (DumpAsm) errs() << "Here's the assembly:\n" << *Composite;
335
336 std::error_code EC;
337 tool_output_file Out(OutputFilename, EC, sys::fs::F_None);
338 if (EC) {
339 errs() << EC.message() << '\n';
340 return 1;
341 }
342
343 if (verifyModule(*Composite, &errs())) {
344 errs() << argv[0] << ": error: linked module is broken!\n";
345 return 1;
346 }
347
348 if (Verbose) errs() << "Writing bitcode...\n";
349 if (OutputAssembly) {
350 Composite->print(Out.os(), nullptr, PreserveAssemblyUseListOrder);
351 } else if (Force || !CheckBitcodeOutputToConsole(Out.os(), true))
352 WriteBitcodeToFile(Composite.get(), Out.os(), PreserveBitcodeUseListOrder);
353
354 // Declare success.
355 Out.keep();
356
357 return 0;
358 }
359