LTOCodeGenerator.cpp revision 276365dd4bc0c2160f91fd8062ae1fc90c86c324 
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 "LTOModule.h"
16#include "LTOCodeGenerator.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/ADT/StringExtras.h"
24#include "llvm/ADT/Triple.h"
25#include "llvm/Analysis/Passes.h"
26#include "llvm/Bitcode/ReaderWriter.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/TargetRegistry.h"
35#include "llvm/Target/TargetSelect.h"
36#include "llvm/Support/CommandLine.h"
37#include "llvm/Support/FormattedStream.h"
38#include "llvm/Support/MemoryBuffer.h"
39#include "llvm/Support/PassManagerBuilder.h"
40#include "llvm/Support/SystemUtils.h"
41#include "llvm/Support/ToolOutputFile.h"
42#include "llvm/Support/Host.h"
43#include "llvm/Support/Program.h"
44#include "llvm/Support/Signals.h"
45#include "llvm/Support/system_error.h"
46#include "llvm/Config/config.h"
47#include <cstdlib>
48#include <unistd.h>
49#include <fcntl.h>
50
51
52using namespace llvm;
53
54static cl::opt<bool> DisableInline("disable-inlining",
55  cl::desc("Do not run the inliner pass"));
56
57
58const char* LTOCodeGenerator::getVersionString()
59{
60#ifdef LLVM_VERSION_INFO
61    return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
62#else
63    return PACKAGE_NAME " version " PACKAGE_VERSION;
64#endif
65}
66
67
68LTOCodeGenerator::LTOCodeGenerator()
69    : _context(getGlobalContext()),
70      _linker("LinkTimeOptimizer", "ld-temp.o", _context), _target(NULL),
71      _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
72      _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
73      _nativeObjectFile(NULL)
74{
75    InitializeAllTargets();
76    InitializeAllAsmPrinters();
77}
78
79LTOCodeGenerator::~LTOCodeGenerator()
80{
81    delete _target;
82    delete _nativeObjectFile;
83}
84
85
86
87bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg)
88{
89
90  if(mod->getLLVVMModule()->MaterializeAllPermanently(&errMsg))
91    return true;
92
93  bool ret = _linker.LinkInModule(mod->getLLVVMModule(), &errMsg);
94
95  const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
96  for (int i = 0, e = undefs.size(); i != e; ++i)
97    _asmUndefinedRefs[undefs[i]] = 1;
98
99  return ret;
100}
101
102
103bool LTOCodeGenerator::setDebugInfo(lto_debug_model debug, std::string& errMsg)
104{
105    switch (debug) {
106        case LTO_DEBUG_MODEL_NONE:
107            _emitDwarfDebugInfo = false;
108            return false;
109
110        case LTO_DEBUG_MODEL_DWARF:
111            _emitDwarfDebugInfo = true;
112            return false;
113    }
114    errMsg = "unknown debug format";
115    return true;
116}
117
118
119bool LTOCodeGenerator::setCodePICModel(lto_codegen_model model,
120                                       std::string& errMsg)
121{
122    switch (model) {
123        case LTO_CODEGEN_PIC_MODEL_STATIC:
124        case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
125        case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
126            _codeModel = model;
127            return false;
128    }
129    errMsg = "unknown pic model";
130    return true;
131}
132
133void LTOCodeGenerator::setCpu(const char* mCpu)
134{
135  _mCpu = mCpu;
136}
137
138void LTOCodeGenerator::addMustPreserveSymbol(const char* sym)
139{
140    _mustPreserveSymbols[sym] = 1;
141}
142
143
144bool LTOCodeGenerator::writeMergedModules(const char *path,
145                                          std::string &errMsg) {
146  if (determineTarget(errMsg))
147    return true;
148
149  // mark which symbols can not be internalized
150  applyScopeRestrictions();
151
152  // create output file
153  std::string ErrInfo;
154  tool_output_file Out(path, ErrInfo,
155                       raw_fd_ostream::F_Binary);
156  if (!ErrInfo.empty()) {
157    errMsg = "could not open bitcode file for writing: ";
158    errMsg += path;
159    return true;
160  }
161
162  // write bitcode to it
163  WriteBitcodeToFile(_linker.getModule(), Out.os());
164  Out.os().close();
165
166  if (Out.os().has_error()) {
167    errMsg = "could not write bitcode file: ";
168    errMsg += path;
169    Out.os().clear_error();
170    return true;
171  }
172
173  Out.keep();
174  return false;
175}
176
177
178bool LTOCodeGenerator::compile_to_file(const char** name, std::string& errMsg)
179{
180  // make unique temp .o file to put generated object file
181  sys::PathWithStatus uniqueObjPath("lto-llvm.o");
182  if ( uniqueObjPath.createTemporaryFileOnDisk(false, &errMsg) ) {
183    uniqueObjPath.eraseFromDisk();
184    return true;
185  }
186  sys::RemoveFileOnSignal(uniqueObjPath);
187
188  // generate object file
189  bool genResult = false;
190  tool_output_file objFile(uniqueObjPath.c_str(), errMsg);
191  if (!errMsg.empty())
192    return NULL;
193  genResult = this->generateObjectFile(objFile.os(), errMsg);
194  objFile.os().close();
195  if (objFile.os().has_error()) {
196    objFile.os().clear_error();
197    return true;
198  }
199  objFile.keep();
200  if ( genResult ) {
201    uniqueObjPath.eraseFromDisk();
202    return true;
203  }
204
205  _nativeObjectPath = uniqueObjPath.str();
206  *name = _nativeObjectPath.c_str();
207  return false;
208}
209
210const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg)
211{
212  const char *name;
213  if (compile_to_file(&name, errMsg))
214    return NULL;
215
216  // remove old buffer if compile() called twice
217  delete _nativeObjectFile;
218
219  // read .o file into memory buffer
220  OwningPtr<MemoryBuffer> BuffPtr;
221  if (error_code ec = MemoryBuffer::getFile(name, BuffPtr, -1, false)) {
222    errMsg = ec.message();
223    return NULL;
224  }
225  _nativeObjectFile = BuffPtr.take();
226
227  // remove temp files
228  sys::Path(_nativeObjectPath).eraseFromDisk();
229
230  // return buffer, unless error
231  if ( _nativeObjectFile == NULL )
232    return NULL;
233  *length = _nativeObjectFile->getBufferSize();
234  return _nativeObjectFile->getBufferStart();
235}
236
237bool LTOCodeGenerator::determineTarget(std::string& errMsg)
238{
239    if ( _target == NULL ) {
240        std::string Triple = _linker.getModule()->getTargetTriple();
241        if (Triple.empty())
242          Triple = sys::getHostTriple();
243
244        // create target machine from info for merged modules
245        const Target *march = TargetRegistry::lookupTarget(Triple, errMsg);
246        if ( march == NULL )
247            return true;
248
249        // The relocation model is actually a static member of TargetMachine
250        // and needs to be set before the TargetMachine is instantiated.
251        switch( _codeModel ) {
252        case LTO_CODEGEN_PIC_MODEL_STATIC:
253            TargetMachine::setRelocationModel(Reloc::Static);
254            break;
255        case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
256            TargetMachine::setRelocationModel(Reloc::PIC_);
257            break;
258        case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
259            TargetMachine::setRelocationModel(Reloc::DynamicNoPIC);
260            break;
261        }
262
263        // construct LTModule, hand over ownership of module and target
264        SubtargetFeatures Features;
265        Features.getDefaultSubtargetFeatures(llvm::Triple(Triple));
266        std::string FeatureStr = Features.getString();
267        _target = march->createTargetMachine(Triple, _mCpu, FeatureStr);
268    }
269    return false;
270}
271
272void LTOCodeGenerator::applyRestriction(GlobalValue &GV,
273                                     std::vector<const char*> &mustPreserveList,
274                                        SmallPtrSet<GlobalValue*, 8> &asmUsed,
275                                        Mangler &mangler) {
276  SmallString<64> Buffer;
277  mangler.getNameWithPrefix(Buffer, &GV, false);
278
279  if (GV.isDeclaration())
280    return;
281  if (_mustPreserveSymbols.count(Buffer))
282    mustPreserveList.push_back(GV.getName().data());
283  if (_asmUndefinedRefs.count(Buffer))
284    asmUsed.insert(&GV);
285}
286
287static void findUsedValues(GlobalVariable *LLVMUsed,
288                           SmallPtrSet<GlobalValue*, 8> &UsedValues) {
289  if (LLVMUsed == 0) return;
290
291  ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
292  if (Inits == 0) return;
293
294  for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
295    if (GlobalValue *GV =
296          dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
297      UsedValues.insert(GV);
298}
299
300void LTOCodeGenerator::applyScopeRestrictions() {
301  if (_scopeRestrictionsDone) return;
302  Module *mergedModule = _linker.getModule();
303
304  // Start off with a verification pass.
305  PassManager passes;
306  passes.add(createVerifierPass());
307
308  // mark which symbols can not be internalized
309  MCContext Context(*_target->getMCAsmInfo(), NULL);
310  Mangler mangler(Context, *_target->getTargetData());
311  std::vector<const char*> mustPreserveList;
312  SmallPtrSet<GlobalValue*, 8> asmUsed;
313
314  for (Module::iterator f = mergedModule->begin(),
315         e = mergedModule->end(); f != e; ++f)
316    applyRestriction(*f, mustPreserveList, asmUsed, mangler);
317  for (Module::global_iterator v = mergedModule->global_begin(),
318         e = mergedModule->global_end(); v !=  e; ++v)
319    applyRestriction(*v, mustPreserveList, asmUsed, mangler);
320  for (Module::alias_iterator a = mergedModule->alias_begin(),
321         e = mergedModule->alias_end(); a != e; ++a)
322    applyRestriction(*a, mustPreserveList, asmUsed, mangler);
323
324  GlobalVariable *LLVMCompilerUsed =
325    mergedModule->getGlobalVariable("llvm.compiler.used");
326  findUsedValues(LLVMCompilerUsed, asmUsed);
327  if (LLVMCompilerUsed)
328    LLVMCompilerUsed->eraseFromParent();
329
330  const llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
331  std::vector<Constant*> asmUsed2;
332  for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
333         e = asmUsed.end(); i !=e; ++i) {
334    GlobalValue *GV = *i;
335    Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
336    asmUsed2.push_back(c);
337  }
338
339  llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
340  LLVMCompilerUsed =
341    new llvm::GlobalVariable(*mergedModule, ATy, false,
342                             llvm::GlobalValue::AppendingLinkage,
343                             llvm::ConstantArray::get(ATy, asmUsed2),
344                             "llvm.compiler.used");
345
346  LLVMCompilerUsed->setSection("llvm.metadata");
347
348  passes.add(createInternalizePass(mustPreserveList));
349
350  // apply scope restrictions
351  passes.run(*mergedModule);
352
353  _scopeRestrictionsDone = true;
354}
355
356/// Optimize merged modules using various IPO passes
357bool LTOCodeGenerator::generateObjectFile(raw_ostream &out,
358                                          std::string &errMsg) {
359    if ( this->determineTarget(errMsg) )
360        return true;
361
362    // mark which symbols can not be internalized
363    this->applyScopeRestrictions();
364
365    Module* mergedModule = _linker.getModule();
366
367    // if options were requested, set them
368    if ( !_codegenOptions.empty() )
369        cl::ParseCommandLineOptions(_codegenOptions.size(),
370                                    const_cast<char **>(&_codegenOptions[0]));
371
372    // Instantiate the pass manager to organize the passes.
373    PassManager passes;
374
375    // Start off with a verification pass.
376    passes.add(createVerifierPass());
377
378    // Add an appropriate TargetData instance for this module...
379    passes.add(new TargetData(*_target->getTargetData()));
380
381    PassManagerBuilder().populateLTOPassManager(passes, /*Internalize=*/ false,
382                                                !DisableInline);
383
384    // Make sure everything is still good.
385    passes.add(createVerifierPass());
386
387    FunctionPassManager *codeGenPasses = new FunctionPassManager(mergedModule);
388
389    codeGenPasses->add(new TargetData(*_target->getTargetData()));
390
391    formatted_raw_ostream Out(out);
392
393    if (_target->addPassesToEmitFile(*codeGenPasses, Out,
394                                     TargetMachine::CGFT_ObjectFile,
395                                     CodeGenOpt::Aggressive)) {
396      errMsg = "target file type not supported";
397      return true;
398    }
399
400    // Run our queue of passes all at once now, efficiently.
401    passes.run(*mergedModule);
402
403    // Run the code generator, and write assembly file
404    codeGenPasses->doInitialization();
405
406    for (Module::iterator
407           it = mergedModule->begin(), e = mergedModule->end(); it != e; ++it)
408      if (!it->isDeclaration())
409        codeGenPasses->run(*it);
410
411    codeGenPasses->doFinalization();
412    delete codeGenPasses;
413
414    return false; // success
415}
416
417
418/// Optimize merged modules using various IPO passes
419void LTOCodeGenerator::setCodeGenDebugOptions(const char* options)
420{
421    for (std::pair<StringRef, StringRef> o = getToken(options);
422         !o.first.empty(); o = getToken(o.second)) {
423        // ParseCommandLineOptions() expects argv[0] to be program name.
424        // Lazily add that.
425        if ( _codegenOptions.empty() )
426            _codegenOptions.push_back("libLTO");
427        _codegenOptions.push_back(strdup(o.first.str().c_str()));
428    }
429}
430