1 //===-LTOCodeGenerator.cpp - LLVM Link Time Optimizer ---------------------===//
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 file implements the Link Time Optimization library. This library is
11 // intended to be used by linker to optimize code at link time.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "LTOCodeGenerator.h"
16 #include "LTOModule.h"
17 #include "llvm/Constants.h"
18 #include "llvm/DerivedTypes.h"
19 #include "llvm/Linker.h"
20 #include "llvm/LLVMContext.h"
21 #include "llvm/Module.h"
22 #include "llvm/PassManager.h"
23 #include "llvm/Analysis/Passes.h"
24 #include "llvm/Analysis/Verifier.h"
25 #include "llvm/Bitcode/ReaderWriter.h"
26 #include "llvm/Config/config.h"
27 #include "llvm/MC/MCAsmInfo.h"
28 #include "llvm/MC/MCContext.h"
29 #include "llvm/MC/SubtargetFeature.h"
30 #include "llvm/Target/Mangler.h"
31 #include "llvm/Target/TargetOptions.h"
32 #include "llvm/Target/TargetData.h"
33 #include "llvm/Target/TargetMachine.h"
34 #include "llvm/Target/TargetRegisterInfo.h"
35 #include "llvm/Transforms/IPO.h"
36 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
37 #include "llvm/Support/CommandLine.h"
38 #include "llvm/Support/FormattedStream.h"
39 #include "llvm/Support/MemoryBuffer.h"
40 #include "llvm/Support/ToolOutputFile.h"
41 #include "llvm/Support/Host.h"
42 #include "llvm/Support/Signals.h"
43 #include "llvm/Support/TargetRegistry.h"
44 #include "llvm/Support/TargetSelect.h"
45 #include "llvm/Support/system_error.h"
46 #include "llvm/ADT/StringExtras.h"
47 using namespace llvm;
48
49 static cl::opt<bool> DisableInline("disable-inlining", cl::init(false),
50 cl::desc("Do not run the inliner pass"));
51
52 static cl::opt<bool> DisableGVNLoadPRE("disable-gvn-loadpre", cl::init(false),
53 cl::desc("Do not run the GVN load PRE pass"));
54
getVersionString()55 const char* LTOCodeGenerator::getVersionString() {
56 #ifdef LLVM_VERSION_INFO
57 return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
58 #else
59 return PACKAGE_NAME " version " PACKAGE_VERSION;
60 #endif
61 }
62
LTOCodeGenerator()63 LTOCodeGenerator::LTOCodeGenerator()
64 : _context(getGlobalContext()),
65 _linker("LinkTimeOptimizer", "ld-temp.o", _context), _target(NULL),
66 _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
67 _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
68 _nativeObjectFile(NULL) {
69 InitializeAllTargets();
70 InitializeAllTargetMCs();
71 InitializeAllAsmPrinters();
72 }
73
~LTOCodeGenerator()74 LTOCodeGenerator::~LTOCodeGenerator() {
75 delete _target;
76 delete _nativeObjectFile;
77
78 for (std::vector<char*>::iterator I = _codegenOptions.begin(),
79 E = _codegenOptions.end(); I != E; ++I)
80 free(*I);
81 }
82
addModule(LTOModule * mod,std::string & errMsg)83 bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg) {
84 bool ret = _linker.LinkInModule(mod->getLLVVMModule(), &errMsg);
85
86 const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
87 for (int i = 0, e = undefs.size(); i != e; ++i)
88 _asmUndefinedRefs[undefs[i]] = 1;
89
90 return ret;
91 }
92
setDebugInfo(lto_debug_model debug,std::string & errMsg)93 bool LTOCodeGenerator::setDebugInfo(lto_debug_model debug,
94 std::string& errMsg) {
95 switch (debug) {
96 case LTO_DEBUG_MODEL_NONE:
97 _emitDwarfDebugInfo = false;
98 return false;
99
100 case LTO_DEBUG_MODEL_DWARF:
101 _emitDwarfDebugInfo = true;
102 return false;
103 }
104 llvm_unreachable("Unknown debug format!");
105 }
106
setCodePICModel(lto_codegen_model model,std::string & errMsg)107 bool LTOCodeGenerator::setCodePICModel(lto_codegen_model model,
108 std::string& errMsg) {
109 switch (model) {
110 case LTO_CODEGEN_PIC_MODEL_STATIC:
111 case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
112 case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
113 _codeModel = model;
114 return false;
115 }
116 llvm_unreachable("Unknown PIC model!");
117 }
118
writeMergedModules(const char * path,std::string & errMsg)119 bool LTOCodeGenerator::writeMergedModules(const char *path,
120 std::string &errMsg) {
121 if (determineTarget(errMsg))
122 return true;
123
124 // mark which symbols can not be internalized
125 applyScopeRestrictions();
126
127 // create output file
128 std::string ErrInfo;
129 tool_output_file Out(path, ErrInfo,
130 raw_fd_ostream::F_Binary);
131 if (!ErrInfo.empty()) {
132 errMsg = "could not open bitcode file for writing: ";
133 errMsg += path;
134 return true;
135 }
136
137 // write bitcode to it
138 WriteBitcodeToFile(_linker.getModule(), Out.os());
139 Out.os().close();
140
141 if (Out.os().has_error()) {
142 errMsg = "could not write bitcode file: ";
143 errMsg += path;
144 Out.os().clear_error();
145 return true;
146 }
147
148 Out.keep();
149 return false;
150 }
151
compile_to_file(const char ** name,std::string & errMsg)152 bool LTOCodeGenerator::compile_to_file(const char** name, std::string& errMsg) {
153 // make unique temp .o file to put generated object file
154 sys::PathWithStatus uniqueObjPath("lto-llvm.o");
155 if ( uniqueObjPath.createTemporaryFileOnDisk(false, &errMsg) ) {
156 uniqueObjPath.eraseFromDisk();
157 return true;
158 }
159 sys::RemoveFileOnSignal(uniqueObjPath);
160
161 // generate object file
162 bool genResult = false;
163 tool_output_file objFile(uniqueObjPath.c_str(), errMsg);
164 if (!errMsg.empty())
165 return true;
166
167 genResult = this->generateObjectFile(objFile.os(), errMsg);
168 objFile.os().close();
169 if (objFile.os().has_error()) {
170 objFile.os().clear_error();
171 return true;
172 }
173
174 objFile.keep();
175 if ( genResult ) {
176 uniqueObjPath.eraseFromDisk();
177 return true;
178 }
179
180 _nativeObjectPath = uniqueObjPath.str();
181 *name = _nativeObjectPath.c_str();
182 return false;
183 }
184
compile(size_t * length,std::string & errMsg)185 const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg) {
186 const char *name;
187 if (compile_to_file(&name, errMsg))
188 return NULL;
189
190 // remove old buffer if compile() called twice
191 delete _nativeObjectFile;
192
193 // read .o file into memory buffer
194 OwningPtr<MemoryBuffer> BuffPtr;
195 if (error_code ec = MemoryBuffer::getFile(name, BuffPtr, -1, false)) {
196 errMsg = ec.message();
197 return NULL;
198 }
199 _nativeObjectFile = BuffPtr.take();
200
201 // remove temp files
202 sys::Path(_nativeObjectPath).eraseFromDisk();
203
204 // return buffer, unless error
205 if ( _nativeObjectFile == NULL )
206 return NULL;
207 *length = _nativeObjectFile->getBufferSize();
208 return _nativeObjectFile->getBufferStart();
209 }
210
determineTarget(std::string & errMsg)211 bool LTOCodeGenerator::determineTarget(std::string& errMsg) {
212 if ( _target == NULL ) {
213 std::string Triple = _linker.getModule()->getTargetTriple();
214 if (Triple.empty())
215 Triple = sys::getDefaultTargetTriple();
216
217 // create target machine from info for merged modules
218 const Target *march = TargetRegistry::lookupTarget(Triple, errMsg);
219 if ( march == NULL )
220 return true;
221
222 // The relocation model is actually a static member of TargetMachine and
223 // needs to be set before the TargetMachine is instantiated.
224 Reloc::Model RelocModel = Reloc::Default;
225 switch( _codeModel ) {
226 case LTO_CODEGEN_PIC_MODEL_STATIC:
227 RelocModel = Reloc::Static;
228 break;
229 case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
230 RelocModel = Reloc::PIC_;
231 break;
232 case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
233 RelocModel = Reloc::DynamicNoPIC;
234 break;
235 }
236
237 // construct LTOModule, hand over ownership of module and target
238 SubtargetFeatures Features;
239 Features.getDefaultSubtargetFeatures(llvm::Triple(Triple));
240 std::string FeatureStr = Features.getString();
241 TargetOptions Options;
242 _target = march->createTargetMachine(Triple, _mCpu, FeatureStr, Options,
243 RelocModel);
244 }
245 return false;
246 }
247
248 void LTOCodeGenerator::
applyRestriction(GlobalValue & GV,std::vector<const char * > & mustPreserveList,SmallPtrSet<GlobalValue *,8> & asmUsed,Mangler & mangler)249 applyRestriction(GlobalValue &GV,
250 std::vector<const char*> &mustPreserveList,
251 SmallPtrSet<GlobalValue*, 8> &asmUsed,
252 Mangler &mangler) {
253 SmallString<64> Buffer;
254 mangler.getNameWithPrefix(Buffer, &GV, false);
255
256 if (GV.isDeclaration())
257 return;
258 if (_mustPreserveSymbols.count(Buffer))
259 mustPreserveList.push_back(GV.getName().data());
260 if (_asmUndefinedRefs.count(Buffer))
261 asmUsed.insert(&GV);
262 }
263
findUsedValues(GlobalVariable * LLVMUsed,SmallPtrSet<GlobalValue *,8> & UsedValues)264 static void findUsedValues(GlobalVariable *LLVMUsed,
265 SmallPtrSet<GlobalValue*, 8> &UsedValues) {
266 if (LLVMUsed == 0) return;
267
268 ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
269 if (Inits == 0) return;
270
271 for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
272 if (GlobalValue *GV =
273 dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
274 UsedValues.insert(GV);
275 }
276
applyScopeRestrictions()277 void LTOCodeGenerator::applyScopeRestrictions() {
278 if (_scopeRestrictionsDone) return;
279 Module *mergedModule = _linker.getModule();
280
281 // Start off with a verification pass.
282 PassManager passes;
283 passes.add(createVerifierPass());
284
285 // mark which symbols can not be internalized
286 MCContext Context(*_target->getMCAsmInfo(), *_target->getRegisterInfo(),NULL);
287 Mangler mangler(Context, *_target->getTargetData());
288 std::vector<const char*> mustPreserveList;
289 SmallPtrSet<GlobalValue*, 8> asmUsed;
290
291 for (Module::iterator f = mergedModule->begin(),
292 e = mergedModule->end(); f != e; ++f)
293 applyRestriction(*f, mustPreserveList, asmUsed, mangler);
294 for (Module::global_iterator v = mergedModule->global_begin(),
295 e = mergedModule->global_end(); v != e; ++v)
296 applyRestriction(*v, mustPreserveList, asmUsed, mangler);
297 for (Module::alias_iterator a = mergedModule->alias_begin(),
298 e = mergedModule->alias_end(); a != e; ++a)
299 applyRestriction(*a, mustPreserveList, asmUsed, mangler);
300
301 GlobalVariable *LLVMCompilerUsed =
302 mergedModule->getGlobalVariable("llvm.compiler.used");
303 findUsedValues(LLVMCompilerUsed, asmUsed);
304 if (LLVMCompilerUsed)
305 LLVMCompilerUsed->eraseFromParent();
306
307 llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
308 std::vector<Constant*> asmUsed2;
309 for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
310 e = asmUsed.end(); i !=e; ++i) {
311 GlobalValue *GV = *i;
312 Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
313 asmUsed2.push_back(c);
314 }
315
316 llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
317 LLVMCompilerUsed =
318 new llvm::GlobalVariable(*mergedModule, ATy, false,
319 llvm::GlobalValue::AppendingLinkage,
320 llvm::ConstantArray::get(ATy, asmUsed2),
321 "llvm.compiler.used");
322
323 LLVMCompilerUsed->setSection("llvm.metadata");
324
325 passes.add(createInternalizePass(mustPreserveList));
326
327 // apply scope restrictions
328 passes.run(*mergedModule);
329
330 _scopeRestrictionsDone = true;
331 }
332
333 /// Optimize merged modules using various IPO passes
generateObjectFile(raw_ostream & out,std::string & errMsg)334 bool LTOCodeGenerator::generateObjectFile(raw_ostream &out,
335 std::string &errMsg) {
336 if ( this->determineTarget(errMsg) )
337 return true;
338
339 Module* mergedModule = _linker.getModule();
340
341 // if options were requested, set them
342 if ( !_codegenOptions.empty() )
343 cl::ParseCommandLineOptions(_codegenOptions.size(),
344 const_cast<char **>(&_codegenOptions[0]));
345
346 // mark which symbols can not be internalized
347 this->applyScopeRestrictions();
348
349 // Instantiate the pass manager to organize the passes.
350 PassManager passes;
351
352 // Start off with a verification pass.
353 passes.add(createVerifierPass());
354
355 // Add an appropriate TargetData instance for this module...
356 passes.add(new TargetData(*_target->getTargetData()));
357
358 // Enabling internalize here would use its AllButMain variant. It
359 // keeps only main if it exists and does nothing for libraries. Instead
360 // we create the pass ourselves with the symbol list provided by the linker.
361 PassManagerBuilder().populateLTOPassManager(passes, /*Internalize=*/false,
362 !DisableInline,
363 DisableGVNLoadPRE);
364
365 // Make sure everything is still good.
366 passes.add(createVerifierPass());
367
368 FunctionPassManager *codeGenPasses = new FunctionPassManager(mergedModule);
369
370 codeGenPasses->add(new TargetData(*_target->getTargetData()));
371
372 formatted_raw_ostream Out(out);
373
374 if (_target->addPassesToEmitFile(*codeGenPasses, Out,
375 TargetMachine::CGFT_ObjectFile,
376 CodeGenOpt::Aggressive)) {
377 errMsg = "target file type not supported";
378 return true;
379 }
380
381 // Run our queue of passes all at once now, efficiently.
382 passes.run(*mergedModule);
383
384 // Run the code generator, and write assembly file
385 codeGenPasses->doInitialization();
386
387 for (Module::iterator
388 it = mergedModule->begin(), e = mergedModule->end(); it != e; ++it)
389 if (!it->isDeclaration())
390 codeGenPasses->run(*it);
391
392 codeGenPasses->doFinalization();
393 delete codeGenPasses;
394
395 return false; // success
396 }
397
398 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
399 /// LTO problems.
setCodeGenDebugOptions(const char * options)400 void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
401 for (std::pair<StringRef, StringRef> o = getToken(options);
402 !o.first.empty(); o = getToken(o.second)) {
403 // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
404 // that.
405 if ( _codegenOptions.empty() )
406 _codegenOptions.push_back(strdup("libLTO"));
407 _codegenOptions.push_back(strdup(o.first.str().c_str()));
408 }
409 }
410