LTOCodeGenerator.cpp revision 0fb32eb56aabb24950bbfecc927596a3fffabcb1 
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/CodeGen/RuntimeLibcalls.h"
22#include "llvm/Config/config.h"
23#include "llvm/IR/Constants.h"
24#include "llvm/IR/DataLayout.h"
25#include "llvm/IR/DerivedTypes.h"
26#include "llvm/IR/LLVMContext.h"
27#include "llvm/IR/Module.h"
28#include "llvm/InitializePasses.h"
29#include "llvm/Linker.h"
30#include "llvm/MC/MCAsmInfo.h"
31#include "llvm/MC/MCContext.h"
32#include "llvm/MC/SubtargetFeature.h"
33#include "llvm/PassManager.h"
34#include "llvm/Support/CommandLine.h"
35#include "llvm/Support/FileSystem.h"
36#include "llvm/Support/FormattedStream.h"
37#include "llvm/Support/Host.h"
38#include "llvm/Support/MemoryBuffer.h"
39#include "llvm/Support/Signals.h"
40#include "llvm/Support/TargetRegistry.h"
41#include "llvm/Support/TargetSelect.h"
42#include "llvm/Support/ToolOutputFile.h"
43#include "llvm/Support/system_error.h"
44#include "llvm/Target/TargetLibraryInfo.h"
45#include "llvm/Target/TargetLowering.h"
46#include "llvm/Target/TargetOptions.h"
47#include "llvm/Target/TargetRegisterInfo.h"
48#include "llvm/Target/Mangler.h"
49#include "llvm/Transforms/IPO.h"
50#include "llvm/Transforms/IPO/PassManagerBuilder.h"
51#include "llvm/Transforms/ObjCARC.h"
52using namespace llvm;
53
54const char* LTOCodeGenerator::getVersionString() {
55#ifdef LLVM_VERSION_INFO
56  return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
57#else
58  return PACKAGE_NAME " version " PACKAGE_VERSION;
59#endif
60}
61
62LTOCodeGenerator::LTOCodeGenerator()
63    : Context(getGlobalContext()), Linker(new Module("ld-temp.o", Context)),
64      TargetMach(NULL), EmitDwarfDebugInfo(false), ScopeRestrictionsDone(false),
65      CodeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC), NativeObjectFile(NULL) {
66  initializeLTOPasses();
67}
68
69LTOCodeGenerator::~LTOCodeGenerator() {
70  delete TargetMach;
71  delete NativeObjectFile;
72  TargetMach = NULL;
73  NativeObjectFile = NULL;
74
75  Linker.deleteModule();
76
77  for (std::vector<char *>::iterator I = CodegenOptions.begin(),
78                                     E = CodegenOptions.end();
79       I != E; ++I)
80    free(*I);
81}
82
83// Initialize LTO passes. Please keep this funciton in sync with
84// PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
85// passes are initialized.
86//
87void LTOCodeGenerator::initializeLTOPasses() {
88  PassRegistry &R = *PassRegistry::getPassRegistry();
89
90  initializeInternalizePassPass(R);
91  initializeIPSCCPPass(R);
92  initializeGlobalOptPass(R);
93  initializeConstantMergePass(R);
94  initializeDAHPass(R);
95  initializeInstCombinerPass(R);
96  initializeSimpleInlinerPass(R);
97  initializePruneEHPass(R);
98  initializeGlobalDCEPass(R);
99  initializeArgPromotionPass(R);
100  initializeJumpThreadingPass(R);
101  initializeSROAPass(R);
102  initializeSROA_DTPass(R);
103  initializeSROA_SSAUpPass(R);
104  initializeFunctionAttrsPass(R);
105  initializeGlobalsModRefPass(R);
106  initializeLICMPass(R);
107  initializeGVNPass(R);
108  initializeMemCpyOptPass(R);
109  initializeDCEPass(R);
110  initializeCFGSimplifyPassPass(R);
111}
112
113bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg) {
114  bool ret = Linker.linkInModule(mod->getLLVVMModule(), &errMsg);
115
116  const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
117  for (int i = 0, e = undefs.size(); i != e; ++i)
118    AsmUndefinedRefs[undefs[i]] = 1;
119
120  return !ret;
121}
122
123void LTOCodeGenerator::setTargetOptions(TargetOptions options) {
124  Options.LessPreciseFPMADOption = options.LessPreciseFPMADOption;
125  Options.NoFramePointerElim = options.NoFramePointerElim;
126  Options.AllowFPOpFusion = options.AllowFPOpFusion;
127  Options.UnsafeFPMath = options.UnsafeFPMath;
128  Options.NoInfsFPMath = options.NoInfsFPMath;
129  Options.NoNaNsFPMath = options.NoNaNsFPMath;
130  Options.HonorSignDependentRoundingFPMathOption =
131    options.HonorSignDependentRoundingFPMathOption;
132  Options.UseSoftFloat = options.UseSoftFloat;
133  Options.FloatABIType = options.FloatABIType;
134  Options.NoZerosInBSS = options.NoZerosInBSS;
135  Options.GuaranteedTailCallOpt = options.GuaranteedTailCallOpt;
136  Options.DisableTailCalls = options.DisableTailCalls;
137  Options.StackAlignmentOverride = options.StackAlignmentOverride;
138  Options.TrapFuncName = options.TrapFuncName;
139  Options.PositionIndependentExecutable = options.PositionIndependentExecutable;
140  Options.EnableSegmentedStacks = options.EnableSegmentedStacks;
141  Options.UseInitArray = options.UseInitArray;
142}
143
144void LTOCodeGenerator::setDebugInfo(lto_debug_model debug) {
145  switch (debug) {
146  case LTO_DEBUG_MODEL_NONE:
147    EmitDwarfDebugInfo = false;
148    return;
149
150  case LTO_DEBUG_MODEL_DWARF:
151    EmitDwarfDebugInfo = true;
152    return;
153  }
154  llvm_unreachable("Unknown debug format!");
155}
156
157void LTOCodeGenerator::setCodePICModel(lto_codegen_model model) {
158  switch (model) {
159  case LTO_CODEGEN_PIC_MODEL_STATIC:
160  case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
161  case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
162    CodeModel = model;
163    return;
164  }
165  llvm_unreachable("Unknown PIC model!");
166}
167
168bool LTOCodeGenerator::writeMergedModules(const char *path,
169                                          std::string &errMsg) {
170  if (!determineTarget(errMsg))
171    return false;
172
173  // mark which symbols can not be internalized
174  applyScopeRestrictions();
175
176  // create output file
177  std::string ErrInfo;
178  tool_output_file Out(path, ErrInfo, sys::fs::F_Binary);
179  if (!ErrInfo.empty()) {
180    errMsg = "could not open bitcode file for writing: ";
181    errMsg += path;
182    return false;
183  }
184
185  // write bitcode to it
186  WriteBitcodeToFile(Linker.getModule(), Out.os());
187  Out.os().close();
188
189  if (Out.os().has_error()) {
190    errMsg = "could not write bitcode file: ";
191    errMsg += path;
192    Out.os().clear_error();
193    return false;
194  }
195
196  Out.keep();
197  return true;
198}
199
200bool LTOCodeGenerator::compile_to_file(const char** name,
201                                       bool disableOpt,
202                                       bool disableInline,
203                                       bool disableGVNLoadPRE,
204                                       std::string& errMsg) {
205  // make unique temp .o file to put generated object file
206  SmallString<128> Filename;
207  int FD;
208  error_code EC = sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
209  if (EC) {
210    errMsg = EC.message();
211    return false;
212  }
213
214  // generate object file
215  tool_output_file objFile(Filename.c_str(), FD);
216
217  bool genResult = generateObjectFile(objFile.os(), disableOpt, disableInline,
218                                      disableGVNLoadPRE, errMsg);
219  objFile.os().close();
220  if (objFile.os().has_error()) {
221    objFile.os().clear_error();
222    sys::fs::remove(Twine(Filename));
223    return false;
224  }
225
226  objFile.keep();
227  if (!genResult) {
228    sys::fs::remove(Twine(Filename));
229    return false;
230  }
231
232  NativeObjectPath = Filename.c_str();
233  *name = NativeObjectPath.c_str();
234  return true;
235}
236
237const void* LTOCodeGenerator::compile(size_t* length,
238                                      bool disableOpt,
239                                      bool disableInline,
240                                      bool disableGVNLoadPRE,
241                                      std::string& errMsg) {
242  const char *name;
243  if (!compile_to_file(&name, disableOpt, disableInline, disableGVNLoadPRE,
244                       errMsg))
245    return NULL;
246
247  // remove old buffer if compile() called twice
248  delete NativeObjectFile;
249
250  // read .o file into memory buffer
251  OwningPtr<MemoryBuffer> BuffPtr;
252  if (error_code ec = MemoryBuffer::getFile(name, BuffPtr, -1, false)) {
253    errMsg = ec.message();
254    sys::fs::remove(NativeObjectPath);
255    return NULL;
256  }
257  NativeObjectFile = BuffPtr.take();
258
259  // remove temp files
260  sys::fs::remove(NativeObjectPath);
261
262  // return buffer, unless error
263  if (NativeObjectFile == NULL)
264    return NULL;
265  *length = NativeObjectFile->getBufferSize();
266  return NativeObjectFile->getBufferStart();
267}
268
269bool LTOCodeGenerator::determineTarget(std::string &errMsg) {
270  if (TargetMach != NULL)
271    return true;
272
273  std::string TripleStr = Linker.getModule()->getTargetTriple();
274  if (TripleStr.empty())
275    TripleStr = sys::getDefaultTargetTriple();
276  llvm::Triple Triple(TripleStr);
277
278  // create target machine from info for merged modules
279  const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
280  if (march == NULL)
281    return false;
282
283  // The relocation model is actually a static member of TargetMachine and
284  // needs to be set before the TargetMachine is instantiated.
285  Reloc::Model RelocModel = Reloc::Default;
286  switch (CodeModel) {
287  case LTO_CODEGEN_PIC_MODEL_STATIC:
288    RelocModel = Reloc::Static;
289    break;
290  case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
291    RelocModel = Reloc::PIC_;
292    break;
293  case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
294    RelocModel = Reloc::DynamicNoPIC;
295    break;
296  }
297
298  // construct LTOModule, hand over ownership of module and target
299  SubtargetFeatures Features;
300  Features.getDefaultSubtargetFeatures(Triple);
301  std::string FeatureStr = Features.getString();
302  // Set a default CPU for Darwin triples.
303  if (MCpu.empty() && Triple.isOSDarwin()) {
304    if (Triple.getArch() == llvm::Triple::x86_64)
305      MCpu = "core2";
306    else if (Triple.getArch() == llvm::Triple::x86)
307      MCpu = "yonah";
308  }
309
310  TargetMach = march->createTargetMachine(TripleStr, MCpu, FeatureStr, Options,
311                                          RelocModel, CodeModel::Default,
312                                          CodeGenOpt::Aggressive);
313  return true;
314}
315
316void LTOCodeGenerator::
317applyRestriction(GlobalValue &GV,
318                 const ArrayRef<StringRef> &Libcalls,
319                 std::vector<const char*> &MustPreserveList,
320                 SmallPtrSet<GlobalValue*, 8> &AsmUsed,
321                 Mangler &Mangler) {
322  SmallString<64> Buffer;
323  Mangler.getNameWithPrefix(Buffer, &GV, false);
324
325  if (GV.isDeclaration())
326    return;
327  if (MustPreserveSymbols.count(Buffer))
328    MustPreserveList.push_back(GV.getName().data());
329  if (AsmUndefinedRefs.count(Buffer))
330    AsmUsed.insert(&GV);
331
332  // Conservatively append user-supplied runtime library functions to
333  // llvm.compiler.used.  These could be internalized and deleted by
334  // optimizations like -globalopt, causing problems when later optimizations
335  // add new library calls (e.g., llvm.memset => memset and printf => puts).
336  // Leave it to the linker to remove any dead code (e.g. with -dead_strip).
337  if (isa<Function>(GV) &&
338      std::binary_search(Libcalls.begin(), Libcalls.end(), GV.getName()))
339    AsmUsed.insert(&GV);
340}
341
342static void findUsedValues(GlobalVariable *LLVMUsed,
343                           SmallPtrSet<GlobalValue*, 8> &UsedValues) {
344  if (LLVMUsed == 0) return;
345
346  ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
347  for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
348    if (GlobalValue *GV =
349        dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
350      UsedValues.insert(GV);
351}
352
353static void accumulateAndSortLibcalls(std::vector<StringRef> &Libcalls,
354                                      const TargetLibraryInfo& TLI,
355                                      const TargetLowering *Lowering)
356{
357  // TargetLibraryInfo has info on C runtime library calls on the current
358  // target.
359  for (unsigned I = 0, E = static_cast<unsigned>(LibFunc::NumLibFuncs);
360       I != E; ++I) {
361    LibFunc::Func F = static_cast<LibFunc::Func>(I);
362    if (TLI.has(F))
363      Libcalls.push_back(TLI.getName(F));
364  }
365
366  // TargetLowering has info on library calls that CodeGen expects to be
367  // available, both from the C runtime and compiler-rt.
368  if (Lowering)
369    for (unsigned I = 0, E = static_cast<unsigned>(RTLIB::UNKNOWN_LIBCALL);
370         I != E; ++I)
371      if (const char *Name
372          = Lowering->getLibcallName(static_cast<RTLIB::Libcall>(I)))
373        Libcalls.push_back(Name);
374
375  array_pod_sort(Libcalls.begin(), Libcalls.end());
376  Libcalls.erase(std::unique(Libcalls.begin(), Libcalls.end()),
377                 Libcalls.end());
378}
379
380void LTOCodeGenerator::applyScopeRestrictions() {
381  if (ScopeRestrictionsDone)
382    return;
383  Module *mergedModule = Linker.getModule();
384
385  // Start off with a verification pass.
386  PassManager passes;
387  passes.add(createVerifierPass());
388
389  // mark which symbols can not be internalized
390  Mangler Mangler(TargetMach);
391  std::vector<const char*> MustPreserveList;
392  SmallPtrSet<GlobalValue*, 8> AsmUsed;
393  std::vector<StringRef> Libcalls;
394  TargetLibraryInfo TLI(Triple(TargetMach->getTargetTriple()));
395  accumulateAndSortLibcalls(Libcalls, TLI, TargetMach->getTargetLowering());
396
397  for (Module::iterator f = mergedModule->begin(),
398         e = mergedModule->end(); f != e; ++f)
399    applyRestriction(*f, Libcalls, MustPreserveList, AsmUsed, Mangler);
400  for (Module::global_iterator v = mergedModule->global_begin(),
401         e = mergedModule->global_end(); v !=  e; ++v)
402    applyRestriction(*v, Libcalls, MustPreserveList, AsmUsed, Mangler);
403  for (Module::alias_iterator a = mergedModule->alias_begin(),
404         e = mergedModule->alias_end(); a != e; ++a)
405    applyRestriction(*a, Libcalls, MustPreserveList, AsmUsed, Mangler);
406
407  GlobalVariable *LLVMCompilerUsed =
408    mergedModule->getGlobalVariable("llvm.compiler.used");
409  findUsedValues(LLVMCompilerUsed, AsmUsed);
410  if (LLVMCompilerUsed)
411    LLVMCompilerUsed->eraseFromParent();
412
413  if (!AsmUsed.empty()) {
414    llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
415    std::vector<Constant*> asmUsed2;
416    for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = AsmUsed.begin(),
417           e = AsmUsed.end(); i !=e; ++i) {
418      GlobalValue *GV = *i;
419      Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
420      asmUsed2.push_back(c);
421    }
422
423    llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
424    LLVMCompilerUsed =
425      new llvm::GlobalVariable(*mergedModule, ATy, false,
426                               llvm::GlobalValue::AppendingLinkage,
427                               llvm::ConstantArray::get(ATy, asmUsed2),
428                               "llvm.compiler.used");
429
430    LLVMCompilerUsed->setSection("llvm.metadata");
431  }
432
433  passes.add(createInternalizePass(MustPreserveList));
434
435  // apply scope restrictions
436  passes.run(*mergedModule);
437
438  ScopeRestrictionsDone = true;
439}
440
441/// Optimize merged modules using various IPO passes
442bool LTOCodeGenerator::generateObjectFile(raw_ostream &out,
443                                          bool DisableOpt,
444                                          bool DisableInline,
445                                          bool DisableGVNLoadPRE,
446                                          std::string &errMsg) {
447  if (!this->determineTarget(errMsg))
448    return false;
449
450  Module *mergedModule = Linker.getModule();
451
452  // Mark which symbols can not be internalized
453  this->applyScopeRestrictions();
454
455  // Instantiate the pass manager to organize the passes.
456  PassManager passes;
457
458  // Start off with a verification pass.
459  passes.add(createVerifierPass());
460
461  // Add an appropriate DataLayout instance for this module...
462  passes.add(new DataLayout(*TargetMach->getDataLayout()));
463  TargetMach->addAnalysisPasses(passes);
464
465  // Enabling internalize here would use its AllButMain variant. It
466  // keeps only main if it exists and does nothing for libraries. Instead
467  // we create the pass ourselves with the symbol list provided by the linker.
468  if (!DisableOpt)
469    PassManagerBuilder().populateLTOPassManager(passes,
470                                              /*Internalize=*/false,
471                                              !DisableInline,
472                                              DisableGVNLoadPRE);
473
474  // Make sure everything is still good.
475  passes.add(createVerifierPass());
476
477  PassManager codeGenPasses;
478
479  codeGenPasses.add(new DataLayout(*TargetMach->getDataLayout()));
480  TargetMach->addAnalysisPasses(codeGenPasses);
481
482  formatted_raw_ostream Out(out);
483
484  // If the bitcode files contain ARC code and were compiled with optimization,
485  // the ObjCARCContractPass must be run, so do it unconditionally here.
486  codeGenPasses.add(createObjCARCContractPass());
487
488  if (TargetMach->addPassesToEmitFile(codeGenPasses, Out,
489                                      TargetMachine::CGFT_ObjectFile)) {
490    errMsg = "target file type not supported";
491    return false;
492  }
493
494  // Run our queue of passes all at once now, efficiently.
495  passes.run(*mergedModule);
496
497  // Run the code generator, and write assembly file
498  codeGenPasses.run(*mergedModule);
499
500  return true;
501}
502
503/// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
504/// LTO problems.
505void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
506  for (std::pair<StringRef, StringRef> o = getToken(options);
507       !o.first.empty(); o = getToken(o.second)) {
508    // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
509    // that.
510    if (CodegenOptions.empty())
511      CodegenOptions.push_back(strdup("libLLVMLTO"));
512    CodegenOptions.push_back(strdup(o.first.str().c_str()));
513  }
514}
515
516void LTOCodeGenerator::parseCodeGenDebugOptions() {
517  // if options were requested, set them
518  if (!CodegenOptions.empty())
519    cl::ParseCommandLineOptions(CodegenOptions.size(),
520                                const_cast<char **>(&CodegenOptions[0]));
521}
522