1 //===-- llvm-lto: a simple command-line program to link modules with LTO --===//
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 program takes in a list of bitcode files, links them, performs link-time
11 // optimization, and outputs an object file.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/ADT/StringSet.h"
16 #include "llvm/Bitcode/ReaderWriter.h"
17 #include "llvm/CodeGen/CommandFlags.h"
18 #include "llvm/IR/DiagnosticPrinter.h"
19 #include "llvm/IR/LLVMContext.h"
20 #include "llvm/LTO/LTOCodeGenerator.h"
21 #include "llvm/LTO/LTOModule.h"
22 #include "llvm/Object/FunctionIndexObjectFile.h"
23 #include "llvm/Support/CommandLine.h"
24 #include "llvm/Support/FileSystem.h"
25 #include "llvm/Support/ManagedStatic.h"
26 #include "llvm/Support/PrettyStackTrace.h"
27 #include "llvm/Support/Signals.h"
28 #include "llvm/Support/TargetSelect.h"
29 #include "llvm/Support/ToolOutputFile.h"
30 #include "llvm/Support/raw_ostream.h"
31 #include <list>
32 
33 using namespace llvm;
34 
35 static cl::opt<char>
36 OptLevel("O",
37          cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "
38                   "(default = '-O2')"),
39          cl::Prefix,
40          cl::ZeroOrMore,
41          cl::init('2'));
42 
43 static cl::opt<bool> DisableVerify(
44     "disable-verify", cl::init(false),
45     cl::desc("Do not run the verifier during the optimization pipeline"));
46 
47 static cl::opt<bool>
48 DisableInline("disable-inlining", cl::init(false),
49   cl::desc("Do not run the inliner pass"));
50 
51 static cl::opt<bool>
52 DisableGVNLoadPRE("disable-gvn-loadpre", cl::init(false),
53   cl::desc("Do not run the GVN load PRE pass"));
54 
55 static cl::opt<bool>
56 DisableLTOVectorization("disable-lto-vectorization", cl::init(false),
57   cl::desc("Do not run loop or slp vectorization during LTO"));
58 
59 static cl::opt<bool>
60 UseDiagnosticHandler("use-diagnostic-handler", cl::init(false),
61   cl::desc("Use a diagnostic handler to test the handler interface"));
62 
63 static cl::opt<bool>
64     ThinLTO("thinlto", cl::init(false),
65             cl::desc("Only write combined global index for ThinLTO backends"));
66 
67 static cl::opt<bool>
68 SaveModuleFile("save-merged-module", cl::init(false),
69                cl::desc("Write merged LTO module to file before CodeGen"));
70 
71 static cl::list<std::string>
72 InputFilenames(cl::Positional, cl::OneOrMore,
73   cl::desc("<input bitcode files>"));
74 
75 static cl::opt<std::string>
76 OutputFilename("o", cl::init(""),
77   cl::desc("Override output filename"),
78   cl::value_desc("filename"));
79 
80 static cl::list<std::string>
81 ExportedSymbols("exported-symbol",
82   cl::desc("Symbol to export from the resulting object file"),
83   cl::ZeroOrMore);
84 
85 static cl::list<std::string>
86 DSOSymbols("dso-symbol",
87   cl::desc("Symbol to put in the symtab in the resulting dso"),
88   cl::ZeroOrMore);
89 
90 static cl::opt<bool> ListSymbolsOnly(
91     "list-symbols-only", cl::init(false),
92     cl::desc("Instead of running LTO, list the symbols in each IR file"));
93 
94 static cl::opt<bool> SetMergedModule(
95     "set-merged-module", cl::init(false),
96     cl::desc("Use the first input module as the merged module"));
97 
98 static cl::opt<unsigned> Parallelism("j", cl::Prefix, cl::init(1),
99                                      cl::desc("Number of backend threads"));
100 
101 namespace {
102 struct ModuleInfo {
103   std::vector<bool> CanBeHidden;
104 };
105 }
106 
handleDiagnostics(lto_codegen_diagnostic_severity_t Severity,const char * Msg,void *)107 static void handleDiagnostics(lto_codegen_diagnostic_severity_t Severity,
108                               const char *Msg, void *) {
109   errs() << "llvm-lto: ";
110   switch (Severity) {
111   case LTO_DS_NOTE:
112     errs() << "note: ";
113     break;
114   case LTO_DS_REMARK:
115     errs() << "remark: ";
116     break;
117   case LTO_DS_ERROR:
118     errs() << "error: ";
119     break;
120   case LTO_DS_WARNING:
121     errs() << "warning: ";
122     break;
123   }
124   errs() << Msg << "\n";
125 }
126 
127 static std::string CurrentActivity;
diagnosticHandler(const DiagnosticInfo & DI)128 static void diagnosticHandler(const DiagnosticInfo &DI) {
129   raw_ostream &OS = errs();
130   OS << "llvm-lto: ";
131   switch (DI.getSeverity()) {
132   case DS_Error:
133     OS << "error";
134     break;
135   case DS_Warning:
136     OS << "warning";
137     break;
138   case DS_Remark:
139     OS << "remark";
140     break;
141   case DS_Note:
142     OS << "note";
143     break;
144   }
145   if (!CurrentActivity.empty())
146     OS << ' ' << CurrentActivity;
147   OS << ": ";
148 
149   DiagnosticPrinterRawOStream DP(OS);
150   DI.print(DP);
151   OS << '\n';
152 
153   if (DI.getSeverity() == DS_Error)
154     exit(1);
155 }
156 
diagnosticHandlerWithContenxt(const DiagnosticInfo & DI,void * Context)157 static void diagnosticHandlerWithContenxt(const DiagnosticInfo &DI,
158                                           void *Context) {
159   diagnosticHandler(DI);
160 }
161 
error(const Twine & Msg)162 static void error(const Twine &Msg) {
163   errs() << "llvm-lto: " << Msg << '\n';
164   exit(1);
165 }
166 
error(std::error_code EC,const Twine & Prefix)167 static void error(std::error_code EC, const Twine &Prefix) {
168   if (EC)
169     error(Prefix + ": " + EC.message());
170 }
171 
172 template <typename T>
error(const ErrorOr<T> & V,const Twine & Prefix)173 static void error(const ErrorOr<T> &V, const Twine &Prefix) {
174   error(V.getError(), Prefix);
175 }
176 
177 static std::unique_ptr<LTOModule>
getLocalLTOModule(StringRef Path,std::unique_ptr<MemoryBuffer> & Buffer,const TargetOptions & Options)178 getLocalLTOModule(StringRef Path, std::unique_ptr<MemoryBuffer> &Buffer,
179                   const TargetOptions &Options) {
180   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
181       MemoryBuffer::getFile(Path);
182   error(BufferOrErr, "error loading file '" + Path + "'");
183   Buffer = std::move(BufferOrErr.get());
184   CurrentActivity = ("loading file '" + Path + "'").str();
185   ErrorOr<std::unique_ptr<LTOModule>> Ret = LTOModule::createInLocalContext(
186       Buffer->getBufferStart(), Buffer->getBufferSize(), Options, Path);
187   CurrentActivity = "";
188   return std::move(*Ret);
189 }
190 
191 /// \brief List symbols in each IR file.
192 ///
193 /// The main point here is to provide lit-testable coverage for the LTOModule
194 /// functionality that's exposed by the C API to list symbols.  Moreover, this
195 /// provides testing coverage for modules that have been created in their own
196 /// contexts.
listSymbols(const TargetOptions & Options)197 static void listSymbols(const TargetOptions &Options) {
198   for (auto &Filename : InputFilenames) {
199     std::unique_ptr<MemoryBuffer> Buffer;
200     std::unique_ptr<LTOModule> Module =
201         getLocalLTOModule(Filename, Buffer, Options);
202 
203     // List the symbols.
204     outs() << Filename << ":\n";
205     for (int I = 0, E = Module->getSymbolCount(); I != E; ++I)
206       outs() << Module->getSymbolName(I) << "\n";
207   }
208 }
209 
210 /// Create a combined index file from the input IR files and write it.
211 ///
212 /// This is meant to enable testing of ThinLTO combined index generation,
213 /// currently available via the gold plugin via -thinlto.
createCombinedFunctionIndex()214 static void createCombinedFunctionIndex() {
215   FunctionInfoIndex CombinedIndex;
216   uint64_t NextModuleId = 0;
217   for (auto &Filename : InputFilenames) {
218     CurrentActivity = "loading file '" + Filename + "'";
219     ErrorOr<std::unique_ptr<FunctionInfoIndex>> IndexOrErr =
220         llvm::getFunctionIndexForFile(Filename, diagnosticHandler);
221     std::unique_ptr<FunctionInfoIndex> Index = std::move(IndexOrErr.get());
222     CurrentActivity = "";
223     // Skip files without a function summary.
224     if (!Index)
225       continue;
226     CombinedIndex.mergeFrom(std::move(Index), ++NextModuleId);
227   }
228   std::error_code EC;
229   assert(!OutputFilename.empty());
230   raw_fd_ostream OS(OutputFilename + ".thinlto.bc", EC,
231                     sys::fs::OpenFlags::F_None);
232   error(EC, "error opening the file '" + OutputFilename + ".thinlto.bc'");
233   WriteFunctionSummaryToFile(CombinedIndex, OS);
234   OS.close();
235 }
236 
main(int argc,char ** argv)237 int main(int argc, char **argv) {
238   // Print a stack trace if we signal out.
239   sys::PrintStackTraceOnErrorSignal();
240   PrettyStackTraceProgram X(argc, argv);
241 
242   llvm_shutdown_obj Y; // Call llvm_shutdown() on exit.
243   cl::ParseCommandLineOptions(argc, argv, "llvm LTO linker\n");
244 
245   if (OptLevel < '0' || OptLevel > '3')
246     error("optimization level must be between 0 and 3");
247 
248   // Initialize the configured targets.
249   InitializeAllTargets();
250   InitializeAllTargetMCs();
251   InitializeAllAsmPrinters();
252   InitializeAllAsmParsers();
253 
254   // set up the TargetOptions for the machine
255   TargetOptions Options = InitTargetOptionsFromCodeGenFlags();
256 
257   if (ListSymbolsOnly) {
258     listSymbols(Options);
259     return 0;
260   }
261 
262   if (ThinLTO) {
263     createCombinedFunctionIndex();
264     return 0;
265   }
266 
267   unsigned BaseArg = 0;
268 
269   LLVMContext Context;
270   Context.setDiagnosticHandler(diagnosticHandlerWithContenxt, nullptr, true);
271 
272   LTOCodeGenerator CodeGen(Context);
273 
274   if (UseDiagnosticHandler)
275     CodeGen.setDiagnosticHandler(handleDiagnostics, nullptr);
276 
277   CodeGen.setCodePICModel(RelocModel);
278 
279   CodeGen.setDebugInfo(LTO_DEBUG_MODEL_DWARF);
280   CodeGen.setTargetOptions(Options);
281 
282   llvm::StringSet<llvm::MallocAllocator> DSOSymbolsSet;
283   for (unsigned i = 0; i < DSOSymbols.size(); ++i)
284     DSOSymbolsSet.insert(DSOSymbols[i]);
285 
286   std::vector<std::string> KeptDSOSyms;
287 
288   for (unsigned i = BaseArg; i < InputFilenames.size(); ++i) {
289     CurrentActivity = "loading file '" + InputFilenames[i] + "'";
290     ErrorOr<std::unique_ptr<LTOModule>> ModuleOrErr =
291         LTOModule::createFromFile(Context, InputFilenames[i].c_str(), Options);
292     std::unique_ptr<LTOModule> &Module = *ModuleOrErr;
293     CurrentActivity = "";
294 
295     unsigned NumSyms = Module->getSymbolCount();
296     for (unsigned I = 0; I < NumSyms; ++I) {
297       StringRef Name = Module->getSymbolName(I);
298       if (!DSOSymbolsSet.count(Name))
299         continue;
300       lto_symbol_attributes Attrs = Module->getSymbolAttributes(I);
301       unsigned Scope = Attrs & LTO_SYMBOL_SCOPE_MASK;
302       if (Scope != LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN)
303         KeptDSOSyms.push_back(Name);
304     }
305 
306     // We use the first input module as the destination module when
307     // SetMergedModule is true.
308     if (SetMergedModule && i == BaseArg) {
309       // Transfer ownership to the code generator.
310       CodeGen.setModule(std::move(Module));
311     } else if (!CodeGen.addModule(Module.get())) {
312       // Print a message here so that we know addModule() did not abort.
313       errs() << argv[0] << ": error adding file '" << InputFilenames[i] << "'\n";
314       return 1;
315     }
316   }
317 
318   // Add all the exported symbols to the table of symbols to preserve.
319   for (unsigned i = 0; i < ExportedSymbols.size(); ++i)
320     CodeGen.addMustPreserveSymbol(ExportedSymbols[i].c_str());
321 
322   // Add all the dso symbols to the table of symbols to expose.
323   for (unsigned i = 0; i < KeptDSOSyms.size(); ++i)
324     CodeGen.addMustPreserveSymbol(KeptDSOSyms[i].c_str());
325 
326   // Set cpu and attrs strings for the default target/subtarget.
327   CodeGen.setCpu(MCPU.c_str());
328 
329   CodeGen.setOptLevel(OptLevel - '0');
330 
331   std::string attrs;
332   for (unsigned i = 0; i < MAttrs.size(); ++i) {
333     if (i > 0)
334       attrs.append(",");
335     attrs.append(MAttrs[i]);
336   }
337 
338   if (!attrs.empty())
339     CodeGen.setAttr(attrs.c_str());
340 
341   if (FileType.getNumOccurrences())
342     CodeGen.setFileType(FileType);
343 
344   if (!OutputFilename.empty()) {
345     if (!CodeGen.optimize(DisableVerify, DisableInline, DisableGVNLoadPRE,
346                           DisableLTOVectorization)) {
347       // Diagnostic messages should have been printed by the handler.
348       errs() << argv[0] << ": error optimizing the code\n";
349       return 1;
350     }
351 
352     if (SaveModuleFile) {
353       std::string ModuleFilename = OutputFilename;
354       ModuleFilename += ".merged.bc";
355       std::string ErrMsg;
356 
357       if (!CodeGen.writeMergedModules(ModuleFilename.c_str())) {
358         errs() << argv[0] << ": writing merged module failed.\n";
359         return 1;
360       }
361     }
362 
363     std::list<tool_output_file> OSs;
364     std::vector<raw_pwrite_stream *> OSPtrs;
365     for (unsigned I = 0; I != Parallelism; ++I) {
366       std::string PartFilename = OutputFilename;
367       if (Parallelism != 1)
368         PartFilename += "." + utostr(I);
369       std::error_code EC;
370       OSs.emplace_back(PartFilename, EC, sys::fs::F_None);
371       if (EC) {
372         errs() << argv[0] << ": error opening the file '" << PartFilename
373                << "': " << EC.message() << "\n";
374         return 1;
375       }
376       OSPtrs.push_back(&OSs.back().os());
377     }
378 
379     if (!CodeGen.compileOptimized(OSPtrs)) {
380       // Diagnostic messages should have been printed by the handler.
381       errs() << argv[0] << ": error compiling the code\n";
382       return 1;
383     }
384 
385     for (tool_output_file &OS : OSs)
386       OS.keep();
387   } else {
388     if (Parallelism != 1) {
389       errs() << argv[0] << ": -j must be specified together with -o\n";
390       return 1;
391     }
392 
393     if (SaveModuleFile) {
394       errs() << argv[0] << ": -save-merged-module must be specified with -o\n";
395       return 1;
396     }
397 
398     const char *OutputName = nullptr;
399     if (!CodeGen.compile_to_file(&OutputName, DisableVerify, DisableInline,
400                                  DisableGVNLoadPRE, DisableLTOVectorization)) {
401       // Diagnostic messages should have been printed by the handler.
402       errs() << argv[0] << ": error compiling the code\n";
403       return 1;
404     }
405 
406     outs() << "Wrote native object file '" << OutputName << "'\n";
407   }
408 
409   return 0;
410 }
411