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/ADT/StringExtras.h"
18 #include "llvm/Analysis/Passes.h"
19 #include "llvm/Analysis/Verifier.h"
20 #include "llvm/Bitcode/ReaderWriter.h"
21 #include "llvm/Config/config.h"
22 #include "llvm/IR/Constants.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/DerivedTypes.h"
25 #include "llvm/IR/LLVMContext.h"
26 #include "llvm/IR/Module.h"
27 #include "llvm/InitializePasses.h"
28 #include "llvm/Linker.h"
29 #include "llvm/MC/MCAsmInfo.h"
30 #include "llvm/MC/MCContext.h"
31 #include "llvm/MC/SubtargetFeature.h"
32 #include "llvm/PassManager.h"
33 #include "llvm/Support/CommandLine.h"
34 #include "llvm/Support/FileSystem.h"
35 #include "llvm/Support/FormattedStream.h"
36 #include "llvm/Support/Host.h"
37 #include "llvm/Support/MemoryBuffer.h"
38 #include "llvm/Support/Signals.h"
39 #include "llvm/Support/TargetRegistry.h"
40 #include "llvm/Support/TargetSelect.h"
41 #include "llvm/Support/ToolOutputFile.h"
42 #include "llvm/Support/system_error.h"
43 #include "llvm/Target/Mangler.h"
44 #include "llvm/Target/TargetMachine.h"
45 #include "llvm/Target/TargetOptions.h"
46 #include "llvm/Target/TargetRegisterInfo.h"
47 #include "llvm/Transforms/IPO.h"
48 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
49 #include "llvm/Transforms/ObjCARC.h"
50 using namespace llvm;
51
52 static cl::opt<bool>
53 DisableOpt("disable-opt", cl::init(false),
54 cl::desc("Do not run any optimization passes"));
55
56 static cl::opt<bool>
57 DisableInline("disable-inlining", cl::init(false),
58 cl::desc("Do not run the inliner pass"));
59
60 static cl::opt<bool>
61 DisableGVNLoadPRE("disable-gvn-loadpre", cl::init(false),
62 cl::desc("Do not run the GVN load PRE pass"));
63
getVersionString()64 const char* LTOCodeGenerator::getVersionString() {
65 #ifdef LLVM_VERSION_INFO
66 return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
67 #else
68 return PACKAGE_NAME " version " PACKAGE_VERSION;
69 #endif
70 }
71
LTOCodeGenerator()72 LTOCodeGenerator::LTOCodeGenerator()
73 : _context(getGlobalContext()),
74 _linker(new Module("ld-temp.o", _context)), _target(NULL),
75 _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
76 _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
77 _nativeObjectFile(NULL) {
78 InitializeAllTargets();
79 InitializeAllTargetMCs();
80 InitializeAllAsmPrinters();
81 initializeLTOPasses();
82 }
83
~LTOCodeGenerator()84 LTOCodeGenerator::~LTOCodeGenerator() {
85 delete _target;
86 delete _nativeObjectFile;
87 delete _linker.getModule();
88
89 for (std::vector<char*>::iterator I = _codegenOptions.begin(),
90 E = _codegenOptions.end(); I != E; ++I)
91 free(*I);
92 }
93
94 // Initialize LTO passes. Please keep this funciton in sync with
95 // PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
96 // passes are initialized.
97 //
initializeLTOPasses()98 void LTOCodeGenerator::initializeLTOPasses() {
99 PassRegistry &R = *PassRegistry::getPassRegistry();
100
101 initializeInternalizePassPass(R);
102 initializeIPSCCPPass(R);
103 initializeGlobalOptPass(R);
104 initializeConstantMergePass(R);
105 initializeDAHPass(R);
106 initializeInstCombinerPass(R);
107 initializeSimpleInlinerPass(R);
108 initializePruneEHPass(R);
109 initializeGlobalDCEPass(R);
110 initializeArgPromotionPass(R);
111 initializeJumpThreadingPass(R);
112 initializeSROAPass(R);
113 initializeSROA_DTPass(R);
114 initializeSROA_SSAUpPass(R);
115 initializeFunctionAttrsPass(R);
116 initializeGlobalsModRefPass(R);
117 initializeLICMPass(R);
118 initializeGVNPass(R);
119 initializeMemCpyOptPass(R);
120 initializeDCEPass(R);
121 initializeCFGSimplifyPassPass(R);
122 }
123
addModule(LTOModule * mod,std::string & errMsg)124 bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg) {
125 bool ret = _linker.linkInModule(mod->getLLVVMModule(), &errMsg);
126
127 const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
128 for (int i = 0, e = undefs.size(); i != e; ++i)
129 _asmUndefinedRefs[undefs[i]] = 1;
130
131 return !ret;
132 }
133
setDebugInfo(lto_debug_model debug)134 void LTOCodeGenerator::setDebugInfo(lto_debug_model debug) {
135 switch (debug) {
136 case LTO_DEBUG_MODEL_NONE:
137 _emitDwarfDebugInfo = false;
138 return;
139
140 case LTO_DEBUG_MODEL_DWARF:
141 _emitDwarfDebugInfo = true;
142 return;
143 }
144 llvm_unreachable("Unknown debug format!");
145 }
146
setCodePICModel(lto_codegen_model model)147 void LTOCodeGenerator::setCodePICModel(lto_codegen_model model) {
148 switch (model) {
149 case LTO_CODEGEN_PIC_MODEL_STATIC:
150 case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
151 case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
152 _codeModel = model;
153 return;
154 }
155 llvm_unreachable("Unknown PIC model!");
156 }
157
writeMergedModules(const char * path,std::string & errMsg)158 bool LTOCodeGenerator::writeMergedModules(const char *path,
159 std::string &errMsg) {
160 if (!determineTarget(errMsg))
161 return false;
162
163 // Run the verifier on the merged modules.
164 PassManager passes;
165 passes.add(createVerifierPass());
166 passes.run(*_linker.getModule());
167
168 // create output file
169 std::string ErrInfo;
170 tool_output_file Out(path, ErrInfo, sys::fs::F_Binary);
171 if (!ErrInfo.empty()) {
172 errMsg = "could not open bitcode file for writing: ";
173 errMsg += path;
174 return false;
175 }
176
177 // write bitcode to it
178 WriteBitcodeToFile(_linker.getModule(), Out.os());
179 Out.os().close();
180
181 if (Out.os().has_error()) {
182 errMsg = "could not write bitcode file: ";
183 errMsg += path;
184 Out.os().clear_error();
185 return false;
186 }
187
188 Out.keep();
189 return true;
190 }
191
compile_to_file(const char ** name,std::string & errMsg)192 bool LTOCodeGenerator::compile_to_file(const char** name, std::string& errMsg) {
193 // make unique temp .o file to put generated object file
194 SmallString<128> Filename;
195 int FD;
196 error_code EC = sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
197 if (EC) {
198 errMsg = EC.message();
199 return false;
200 }
201
202 // generate object file
203 tool_output_file objFile(Filename.c_str(), FD);
204
205 bool genResult = generateObjectFile(objFile.os(), errMsg);
206 objFile.os().close();
207 if (objFile.os().has_error()) {
208 objFile.os().clear_error();
209 sys::fs::remove(Twine(Filename));
210 return false;
211 }
212
213 objFile.keep();
214 if (!genResult) {
215 sys::fs::remove(Twine(Filename));
216 return false;
217 }
218
219 _nativeObjectPath = Filename.c_str();
220 *name = _nativeObjectPath.c_str();
221 return true;
222 }
223
compile(size_t * length,std::string & errMsg)224 const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg) {
225 const char *name;
226 if (!compile_to_file(&name, errMsg))
227 return NULL;
228
229 // remove old buffer if compile() called twice
230 delete _nativeObjectFile;
231
232 // read .o file into memory buffer
233 OwningPtr<MemoryBuffer> BuffPtr;
234 if (error_code ec = MemoryBuffer::getFile(name, BuffPtr, -1, false)) {
235 errMsg = ec.message();
236 sys::fs::remove(_nativeObjectPath);
237 return NULL;
238 }
239 _nativeObjectFile = BuffPtr.take();
240
241 // remove temp files
242 sys::fs::remove(_nativeObjectPath);
243
244 // return buffer, unless error
245 if (_nativeObjectFile == NULL)
246 return NULL;
247 *length = _nativeObjectFile->getBufferSize();
248 return _nativeObjectFile->getBufferStart();
249 }
250
determineTarget(std::string & errMsg)251 bool LTOCodeGenerator::determineTarget(std::string &errMsg) {
252 if (_target != NULL)
253 return true;
254
255 // if options were requested, set them
256 if (!_codegenOptions.empty())
257 cl::ParseCommandLineOptions(_codegenOptions.size(),
258 const_cast<char **>(&_codegenOptions[0]));
259
260 std::string TripleStr = _linker.getModule()->getTargetTriple();
261 if (TripleStr.empty())
262 TripleStr = sys::getDefaultTargetTriple();
263 llvm::Triple Triple(TripleStr);
264
265 // create target machine from info for merged modules
266 const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
267 if (march == NULL)
268 return false;
269
270 // The relocation model is actually a static member of TargetMachine and
271 // needs to be set before the TargetMachine is instantiated.
272 Reloc::Model RelocModel = Reloc::Default;
273 switch (_codeModel) {
274 case LTO_CODEGEN_PIC_MODEL_STATIC:
275 RelocModel = Reloc::Static;
276 break;
277 case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
278 RelocModel = Reloc::PIC_;
279 break;
280 case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
281 RelocModel = Reloc::DynamicNoPIC;
282 break;
283 }
284
285 // construct LTOModule, hand over ownership of module and target
286 SubtargetFeatures Features;
287 Features.getDefaultSubtargetFeatures(Triple);
288 std::string FeatureStr = Features.getString();
289 // Set a default CPU for Darwin triples.
290 if (_mCpu.empty() && Triple.isOSDarwin()) {
291 if (Triple.getArch() == llvm::Triple::x86_64)
292 _mCpu = "core2";
293 else if (Triple.getArch() == llvm::Triple::x86)
294 _mCpu = "yonah";
295 }
296 TargetOptions Options;
297 LTOModule::getTargetOptions(Options);
298 _target = march->createTargetMachine(TripleStr, _mCpu, FeatureStr, Options,
299 RelocModel, CodeModel::Default,
300 CodeGenOpt::Aggressive);
301 return true;
302 }
303
304 void LTOCodeGenerator::
applyRestriction(GlobalValue & GV,std::vector<const char * > & mustPreserveList,SmallPtrSet<GlobalValue *,8> & asmUsed,Mangler & mangler)305 applyRestriction(GlobalValue &GV,
306 std::vector<const char*> &mustPreserveList,
307 SmallPtrSet<GlobalValue*, 8> &asmUsed,
308 Mangler &mangler) {
309 SmallString<64> Buffer;
310 mangler.getNameWithPrefix(Buffer, &GV, false);
311
312 if (GV.isDeclaration())
313 return;
314 if (_mustPreserveSymbols.count(Buffer))
315 mustPreserveList.push_back(GV.getName().data());
316 if (_asmUndefinedRefs.count(Buffer))
317 asmUsed.insert(&GV);
318 }
319
findUsedValues(GlobalVariable * LLVMUsed,SmallPtrSet<GlobalValue *,8> & UsedValues)320 static void findUsedValues(GlobalVariable *LLVMUsed,
321 SmallPtrSet<GlobalValue*, 8> &UsedValues) {
322 if (LLVMUsed == 0) return;
323
324 ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
325 for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
326 if (GlobalValue *GV =
327 dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
328 UsedValues.insert(GV);
329 }
330
applyScopeRestrictions()331 void LTOCodeGenerator::applyScopeRestrictions() {
332 if (_scopeRestrictionsDone) return;
333 Module *mergedModule = _linker.getModule();
334
335 // Start off with a verification pass.
336 PassManager passes;
337 passes.add(createVerifierPass());
338
339 // mark which symbols can not be internalized
340 MCContext Context(_target->getMCAsmInfo(), _target->getRegisterInfo(), NULL);
341 Mangler mangler(Context, _target);
342 std::vector<const char*> mustPreserveList;
343 SmallPtrSet<GlobalValue*, 8> asmUsed;
344
345 for (Module::iterator f = mergedModule->begin(),
346 e = mergedModule->end(); f != e; ++f)
347 applyRestriction(*f, mustPreserveList, asmUsed, mangler);
348 for (Module::global_iterator v = mergedModule->global_begin(),
349 e = mergedModule->global_end(); v != e; ++v)
350 applyRestriction(*v, mustPreserveList, asmUsed, mangler);
351 for (Module::alias_iterator a = mergedModule->alias_begin(),
352 e = mergedModule->alias_end(); a != e; ++a)
353 applyRestriction(*a, mustPreserveList, asmUsed, mangler);
354
355 GlobalVariable *LLVMCompilerUsed =
356 mergedModule->getGlobalVariable("llvm.compiler.used");
357 findUsedValues(LLVMCompilerUsed, asmUsed);
358 if (LLVMCompilerUsed)
359 LLVMCompilerUsed->eraseFromParent();
360
361 if (!asmUsed.empty()) {
362 llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
363 std::vector<Constant*> asmUsed2;
364 for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
365 e = asmUsed.end(); i !=e; ++i) {
366 GlobalValue *GV = *i;
367 Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
368 asmUsed2.push_back(c);
369 }
370
371 llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
372 LLVMCompilerUsed =
373 new llvm::GlobalVariable(*mergedModule, ATy, false,
374 llvm::GlobalValue::AppendingLinkage,
375 llvm::ConstantArray::get(ATy, asmUsed2),
376 "llvm.compiler.used");
377
378 LLVMCompilerUsed->setSection("llvm.metadata");
379 }
380
381 passes.add(createInternalizePass(mustPreserveList));
382
383 // apply scope restrictions
384 passes.run(*mergedModule);
385
386 _scopeRestrictionsDone = true;
387 }
388
389 /// Optimize merged modules using various IPO passes
generateObjectFile(raw_ostream & out,std::string & errMsg)390 bool LTOCodeGenerator::generateObjectFile(raw_ostream &out,
391 std::string &errMsg) {
392 if (!this->determineTarget(errMsg))
393 return false;
394
395 Module* mergedModule = _linker.getModule();
396
397 // Mark which symbols can not be internalized
398 this->applyScopeRestrictions();
399
400 // Instantiate the pass manager to organize the passes.
401 PassManager passes;
402
403 // Start off with a verification pass.
404 passes.add(createVerifierPass());
405
406 // Add an appropriate DataLayout instance for this module...
407 passes.add(new DataLayout(*_target->getDataLayout()));
408 _target->addAnalysisPasses(passes);
409
410 // Enabling internalize here would use its AllButMain variant. It
411 // keeps only main if it exists and does nothing for libraries. Instead
412 // we create the pass ourselves with the symbol list provided by the linker.
413 if (!DisableOpt)
414 PassManagerBuilder().populateLTOPassManager(passes,
415 /*Internalize=*/false,
416 !DisableInline,
417 DisableGVNLoadPRE);
418
419 // Make sure everything is still good.
420 passes.add(createVerifierPass());
421
422 PassManager codeGenPasses;
423
424 codeGenPasses.add(new DataLayout(*_target->getDataLayout()));
425 _target->addAnalysisPasses(codeGenPasses);
426
427 formatted_raw_ostream Out(out);
428
429 // If the bitcode files contain ARC code and were compiled with optimization,
430 // the ObjCARCContractPass must be run, so do it unconditionally here.
431 codeGenPasses.add(createObjCARCContractPass());
432
433 if (_target->addPassesToEmitFile(codeGenPasses, Out,
434 TargetMachine::CGFT_ObjectFile)) {
435 errMsg = "target file type not supported";
436 return false;
437 }
438
439 // Run our queue of passes all at once now, efficiently.
440 passes.run(*mergedModule);
441
442 // Run the code generator, and write assembly file
443 codeGenPasses.run(*mergedModule);
444
445 return true;
446 }
447
448 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
449 /// LTO problems.
setCodeGenDebugOptions(const char * options)450 void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
451 for (std::pair<StringRef, StringRef> o = getToken(options);
452 !o.first.empty(); o = getToken(o.second)) {
453 // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
454 // that.
455 if (_codegenOptions.empty())
456 _codegenOptions.push_back(strdup("libLTO"));
457 _codegenOptions.push_back(strdup(o.first.str().c_str()));
458 }
459 }
460