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 "llvm/LTO/LTOCodeGenerator.h"
16 #include "llvm/LTO/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/TargetOptions.h"
44 #include "llvm/Target/TargetRegisterInfo.h"
45 #include "llvm/Target/Mangler.h"
46 #include "llvm/Transforms/IPO.h"
47 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
48 #include "llvm/Transforms/ObjCARC.h"
49 using namespace llvm;
50 
51 const char* LTOCodeGenerator::getVersionString() {
52 #ifdef LLVM_VERSION_INFO
53   return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
54 #else
55   return PACKAGE_NAME " version " PACKAGE_VERSION;
56 #endif
57 }
58 
59 LTOCodeGenerator::LTOCodeGenerator()
60     : Context(getGlobalContext()), Linker(new Module("ld-temp.o", Context)),
61       TargetMach(NULL), EmitDwarfDebugInfo(false), ScopeRestrictionsDone(false),
62       CodeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC), NativeObjectFile(NULL) {
63   initializeLTOPasses();
64 }
65 
66 LTOCodeGenerator::~LTOCodeGenerator() {
67   delete TargetMach;
68   delete NativeObjectFile;
69   delete Linker.getModule();
70 
71   for (std::vector<char *>::iterator I = CodegenOptions.begin(),
72                                      E = CodegenOptions.end();
73        I != E; ++I)
74     free(*I);
75 }
76 
77 // Initialize LTO passes. Please keep this funciton in sync with
78 // PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
79 // passes are initialized.
80 //
81 void LTOCodeGenerator::initializeLTOPasses() {
82   PassRegistry &R = *PassRegistry::getPassRegistry();
83 
84   initializeInternalizePassPass(R);
85   initializeIPSCCPPass(R);
86   initializeGlobalOptPass(R);
87   initializeConstantMergePass(R);
88   initializeDAHPass(R);
89   initializeInstCombinerPass(R);
90   initializeSimpleInlinerPass(R);
91   initializePruneEHPass(R);
92   initializeGlobalDCEPass(R);
93   initializeArgPromotionPass(R);
94   initializeJumpThreadingPass(R);
95   initializeSROAPass(R);
96   initializeSROA_DTPass(R);
97   initializeSROA_SSAUpPass(R);
98   initializeFunctionAttrsPass(R);
99   initializeGlobalsModRefPass(R);
100   initializeLICMPass(R);
101   initializeGVNPass(R);
102   initializeMemCpyOptPass(R);
103   initializeDCEPass(R);
104   initializeCFGSimplifyPassPass(R);
105 }
106 
107 bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg) {
108   bool ret = Linker.linkInModule(mod->getLLVVMModule(), &errMsg);
109 
110   const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
111   for (int i = 0, e = undefs.size(); i != e; ++i)
112     AsmUndefinedRefs[undefs[i]] = 1;
113 
114   return !ret;
115 }
116 
117 void LTOCodeGenerator::setTargetOptions(TargetOptions options) {
118   Options.LessPreciseFPMADOption = options.LessPreciseFPMADOption;
119   Options.NoFramePointerElim = options.NoFramePointerElim;
120   Options.AllowFPOpFusion = options.AllowFPOpFusion;
121   Options.UnsafeFPMath = options.UnsafeFPMath;
122   Options.NoInfsFPMath = options.NoInfsFPMath;
123   Options.NoNaNsFPMath = options.NoNaNsFPMath;
124   Options.HonorSignDependentRoundingFPMathOption =
125     options.HonorSignDependentRoundingFPMathOption;
126   Options.UseSoftFloat = options.UseSoftFloat;
127   Options.FloatABIType = options.FloatABIType;
128   Options.NoZerosInBSS = options.NoZerosInBSS;
129   Options.GuaranteedTailCallOpt = options.GuaranteedTailCallOpt;
130   Options.DisableTailCalls = options.DisableTailCalls;
131   Options.StackAlignmentOverride = options.StackAlignmentOverride;
132   Options.TrapFuncName = options.TrapFuncName;
133   Options.PositionIndependentExecutable = options.PositionIndependentExecutable;
134   Options.EnableSegmentedStacks = options.EnableSegmentedStacks;
135   Options.UseInitArray = options.UseInitArray;
136 }
137 
138 void LTOCodeGenerator::setDebugInfo(lto_debug_model debug) {
139   switch (debug) {
140   case LTO_DEBUG_MODEL_NONE:
141     EmitDwarfDebugInfo = false;
142     return;
143 
144   case LTO_DEBUG_MODEL_DWARF:
145     EmitDwarfDebugInfo = true;
146     return;
147   }
148   llvm_unreachable("Unknown debug format!");
149 }
150 
151 void LTOCodeGenerator::setCodePICModel(lto_codegen_model model) {
152   switch (model) {
153   case LTO_CODEGEN_PIC_MODEL_STATIC:
154   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
155   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
156     CodeModel = model;
157     return;
158   }
159   llvm_unreachable("Unknown PIC model!");
160 }
161 
162 bool LTOCodeGenerator::writeMergedModules(const char *path,
163                                           std::string &errMsg) {
164   if (!determineTarget(errMsg))
165     return false;
166 
167   // mark which symbols can not be internalized
168   applyScopeRestrictions();
169 
170   // create output file
171   std::string ErrInfo;
172   tool_output_file Out(path, ErrInfo, sys::fs::F_Binary);
173   if (!ErrInfo.empty()) {
174     errMsg = "could not open bitcode file for writing: ";
175     errMsg += path;
176     return false;
177   }
178 
179   // write bitcode to it
180   WriteBitcodeToFile(Linker.getModule(), Out.os());
181   Out.os().close();
182 
183   if (Out.os().has_error()) {
184     errMsg = "could not write bitcode file: ";
185     errMsg += path;
186     Out.os().clear_error();
187     return false;
188   }
189 
190   Out.keep();
191   return true;
192 }
193 
194 bool LTOCodeGenerator::compile_to_file(const char** name,
195                                        bool disableOpt,
196                                        bool disableInline,
197                                        bool disableGVNLoadPRE,
198                                        std::string& errMsg) {
199   // make unique temp .o file to put generated object file
200   SmallString<128> Filename;
201   int FD;
202   error_code EC = sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
203   if (EC) {
204     errMsg = EC.message();
205     return false;
206   }
207 
208   // generate object file
209   tool_output_file objFile(Filename.c_str(), FD);
210 
211   bool genResult = generateObjectFile(objFile.os(), disableOpt, disableInline,
212                                       disableGVNLoadPRE, errMsg);
213   objFile.os().close();
214   if (objFile.os().has_error()) {
215     objFile.os().clear_error();
216     sys::fs::remove(Twine(Filename));
217     return false;
218   }
219 
220   objFile.keep();
221   if (!genResult) {
222     sys::fs::remove(Twine(Filename));
223     return false;
224   }
225 
226   NativeObjectPath = Filename.c_str();
227   *name = NativeObjectPath.c_str();
228   return true;
229 }
230 
231 const void* LTOCodeGenerator::compile(size_t* length,
232                                       bool disableOpt,
233                                       bool disableInline,
234                                       bool disableGVNLoadPRE,
235                                       std::string& errMsg) {
236   const char *name;
237   if (!compile_to_file(&name, disableOpt, disableInline, disableGVNLoadPRE,
238                        errMsg))
239     return NULL;
240 
241   // remove old buffer if compile() called twice
242   delete NativeObjectFile;
243 
244   // read .o file into memory buffer
245   OwningPtr<MemoryBuffer> BuffPtr;
246   if (error_code ec = MemoryBuffer::getFile(name, BuffPtr, -1, false)) {
247     errMsg = ec.message();
248     sys::fs::remove(NativeObjectPath);
249     return NULL;
250   }
251   NativeObjectFile = BuffPtr.take();
252 
253   // remove temp files
254   sys::fs::remove(NativeObjectPath);
255 
256   // return buffer, unless error
257   if (NativeObjectFile == NULL)
258     return NULL;
259   *length = NativeObjectFile->getBufferSize();
260   return NativeObjectFile->getBufferStart();
261 }
262 
263 bool LTOCodeGenerator::determineTarget(std::string &errMsg) {
264   if (TargetMach != NULL)
265     return true;
266 
267   std::string TripleStr = Linker.getModule()->getTargetTriple();
268   if (TripleStr.empty())
269     TripleStr = sys::getDefaultTargetTriple();
270   llvm::Triple Triple(TripleStr);
271 
272   // create target machine from info for merged modules
273   const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
274   if (march == NULL)
275     return false;
276 
277   // The relocation model is actually a static member of TargetMachine and
278   // needs to be set before the TargetMachine is instantiated.
279   Reloc::Model RelocModel = Reloc::Default;
280   switch (CodeModel) {
281   case LTO_CODEGEN_PIC_MODEL_STATIC:
282     RelocModel = Reloc::Static;
283     break;
284   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
285     RelocModel = Reloc::PIC_;
286     break;
287   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
288     RelocModel = Reloc::DynamicNoPIC;
289     break;
290   }
291 
292   // construct LTOModule, hand over ownership of module and target
293   SubtargetFeatures Features;
294   Features.getDefaultSubtargetFeatures(Triple);
295   std::string FeatureStr = Features.getString();
296   // Set a default CPU for Darwin triples.
297   if (MCpu.empty() && Triple.isOSDarwin()) {
298     if (Triple.getArch() == llvm::Triple::x86_64)
299       MCpu = "core2";
300     else if (Triple.getArch() == llvm::Triple::x86)
301       MCpu = "yonah";
302   }
303 
304   TargetMach = march->createTargetMachine(TripleStr, MCpu, FeatureStr, Options,
305                                           RelocModel, CodeModel::Default,
306                                           CodeGenOpt::Aggressive);
307   return true;
308 }
309 
310 void LTOCodeGenerator::
311 applyRestriction(GlobalValue &GV,
312                  std::vector<const char*> &MustPreserveList,
313                  std::vector<const char*> &DSOList,
314                  SmallPtrSet<GlobalValue*, 8> &AsmUsed,
315                  Mangler &Mangler) {
316   SmallString<64> Buffer;
317   Mangler.getNameWithPrefix(Buffer, &GV, false);
318 
319   if (GV.isDeclaration())
320     return;
321   if (MustPreserveSymbols.count(Buffer))
322     MustPreserveList.push_back(GV.getName().data());
323   if (DSOSymbols.count(Buffer))
324     DSOList.push_back(GV.getName().data());
325   if (AsmUndefinedRefs.count(Buffer))
326     AsmUsed.insert(&GV);
327 }
328 
329 static void findUsedValues(GlobalVariable *LLVMUsed,
330                            SmallPtrSet<GlobalValue*, 8> &UsedValues) {
331   if (LLVMUsed == 0) return;
332 
333   ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
334   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
335     if (GlobalValue *GV =
336         dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
337       UsedValues.insert(GV);
338 }
339 
340 void LTOCodeGenerator::applyScopeRestrictions() {
341   if (ScopeRestrictionsDone)
342     return;
343   Module *mergedModule = Linker.getModule();
344 
345   // Start off with a verification pass.
346   PassManager passes;
347   passes.add(createVerifierPass());
348 
349   // mark which symbols can not be internalized
350   MCContext MContext(TargetMach->getMCAsmInfo(), TargetMach->getRegisterInfo(),
351                      NULL);
352   Mangler Mangler(MContext, TargetMach);
353   std::vector<const char*> MustPreserveList;
354   std::vector<const char*> DSOList;
355   SmallPtrSet<GlobalValue*, 8> AsmUsed;
356 
357   for (Module::iterator f = mergedModule->begin(),
358          e = mergedModule->end(); f != e; ++f)
359     applyRestriction(*f, MustPreserveList, DSOList, AsmUsed, Mangler);
360   for (Module::global_iterator v = mergedModule->global_begin(),
361          e = mergedModule->global_end(); v !=  e; ++v)
362     applyRestriction(*v, MustPreserveList, DSOList, AsmUsed, Mangler);
363   for (Module::alias_iterator a = mergedModule->alias_begin(),
364          e = mergedModule->alias_end(); a != e; ++a)
365     applyRestriction(*a, MustPreserveList, DSOList, AsmUsed, Mangler);
366 
367   GlobalVariable *LLVMCompilerUsed =
368     mergedModule->getGlobalVariable("llvm.compiler.used");
369   findUsedValues(LLVMCompilerUsed, AsmUsed);
370   if (LLVMCompilerUsed)
371     LLVMCompilerUsed->eraseFromParent();
372 
373   if (!AsmUsed.empty()) {
374     llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
375     std::vector<Constant*> asmUsed2;
376     for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = AsmUsed.begin(),
377            e = AsmUsed.end(); i !=e; ++i) {
378       GlobalValue *GV = *i;
379       Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
380       asmUsed2.push_back(c);
381     }
382 
383     llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
384     LLVMCompilerUsed =
385       new llvm::GlobalVariable(*mergedModule, ATy, false,
386                                llvm::GlobalValue::AppendingLinkage,
387                                llvm::ConstantArray::get(ATy, asmUsed2),
388                                "llvm.compiler.used");
389 
390     LLVMCompilerUsed->setSection("llvm.metadata");
391   }
392 
393   passes.add(createInternalizePass(MustPreserveList, DSOList));
394 
395   // apply scope restrictions
396   passes.run(*mergedModule);
397 
398   ScopeRestrictionsDone = true;
399 }
400 
401 /// Optimize merged modules using various IPO passes
402 bool LTOCodeGenerator::generateObjectFile(raw_ostream &out,
403                                           bool DisableOpt,
404                                           bool DisableInline,
405                                           bool DisableGVNLoadPRE,
406                                           std::string &errMsg) {
407   if (!this->determineTarget(errMsg))
408     return false;
409 
410   Module *mergedModule = Linker.getModule();
411 
412   // Mark which symbols can not be internalized
413   this->applyScopeRestrictions();
414 
415   // Instantiate the pass manager to organize the passes.
416   PassManager passes;
417 
418   // Start off with a verification pass.
419   passes.add(createVerifierPass());
420 
421   // Add an appropriate DataLayout instance for this module...
422   passes.add(new DataLayout(*TargetMach->getDataLayout()));
423   TargetMach->addAnalysisPasses(passes);
424 
425   // Enabling internalize here would use its AllButMain variant. It
426   // keeps only main if it exists and does nothing for libraries. Instead
427   // we create the pass ourselves with the symbol list provided by the linker.
428   if (!DisableOpt)
429     PassManagerBuilder().populateLTOPassManager(passes,
430                                               /*Internalize=*/false,
431                                               !DisableInline,
432                                               DisableGVNLoadPRE);
433 
434   // Make sure everything is still good.
435   passes.add(createVerifierPass());
436 
437   PassManager codeGenPasses;
438 
439   codeGenPasses.add(new DataLayout(*TargetMach->getDataLayout()));
440   TargetMach->addAnalysisPasses(codeGenPasses);
441 
442   formatted_raw_ostream Out(out);
443 
444   // If the bitcode files contain ARC code and were compiled with optimization,
445   // the ObjCARCContractPass must be run, so do it unconditionally here.
446   codeGenPasses.add(createObjCARCContractPass());
447 
448   if (TargetMach->addPassesToEmitFile(codeGenPasses, Out,
449                                       TargetMachine::CGFT_ObjectFile)) {
450     errMsg = "target file type not supported";
451     return false;
452   }
453 
454   // Run our queue of passes all at once now, efficiently.
455   passes.run(*mergedModule);
456 
457   // Run the code generator, and write assembly file
458   codeGenPasses.run(*mergedModule);
459 
460   return true;
461 }
462 
463 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
464 /// LTO problems.
465 void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
466   for (std::pair<StringRef, StringRef> o = getToken(options);
467        !o.first.empty(); o = getToken(o.second)) {
468     // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
469     // that.
470     if (CodegenOptions.empty())
471       CodegenOptions.push_back(strdup("libLLVMLTO"));
472     CodegenOptions.push_back(strdup(o.first.str().c_str()));
473   }
474 }
475 
476 void LTOCodeGenerator::parseCodeGenDebugOptions() {
477   // if options were requested, set them
478   if (!CodegenOptions.empty())
479     cl::ParseCommandLineOptions(CodegenOptions.size(),
480                                 const_cast<char **>(&CodegenOptions[0]));
481 }
482