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