LTOCodeGenerator.cpp revision a93ae711a91dd151ca4d28e4172e0de89d1594f3 
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
18
19#include "llvm/Module.h"
20#include "llvm/PassManager.h"
21#include "llvm/Linker.h"
22#include "llvm/Constants.h"
23#include "llvm/DerivedTypes.h"
24#include "llvm/ModuleProvider.h"
25#include "llvm/Bitcode/ReaderWriter.h"
26#include "llvm/Support/SystemUtils.h"
27#include "llvm/Support/Mangler.h"
28#include "llvm/Support/MemoryBuffer.h"
29#include "llvm/System/Signals.h"
30#include "llvm/Analysis/Passes.h"
31#include "llvm/Analysis/LoopPass.h"
32#include "llvm/Analysis/Verifier.h"
33#include "llvm/Analysis/LoadValueNumbering.h"
34#include "llvm/CodeGen/FileWriters.h"
35#include "llvm/Target/SubtargetFeature.h"
36#include "llvm/Target/TargetOptions.h"
37#include "llvm/Target/TargetData.h"
38#include "llvm/Target/TargetMachine.h"
39#include "llvm/Target/TargetMachineRegistry.h"
40#include "llvm/Target/TargetAsmInfo.h"
41#include "llvm/Transforms/IPO.h"
42#include "llvm/Transforms/Scalar.h"
43#include "llvm/ADT/StringExtras.h"
44#include "llvm/Config/config.h"
45
46
47#include <fstream>
48#include <unistd.h>
49#include <stdlib.h>
50#include <fcntl.h>
51
52
53using namespace llvm;
54
55
56
57const char* LTOCodeGenerator::getVersionString()
58{
59#ifdef LLVM_VERSION_INFO
60    return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
61#else
62    return PACKAGE_NAME " version " PACKAGE_VERSION;
63#endif
64}
65
66
67LTOCodeGenerator::LTOCodeGenerator()
68    : _linker("LinkTimeOptimizer", "ld-temp.o"), _target(NULL),
69      _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
70      _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
71      _nativeObjectFile(NULL)
72{
73
74}
75
76LTOCodeGenerator::~LTOCodeGenerator()
77{
78    delete _target;
79    delete _nativeObjectFile;
80}
81
82
83
84bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg)
85{
86    return _linker.LinkInModule(mod->getLLVVMModule(), &errMsg);
87}
88
89
90bool LTOCodeGenerator::setDebugInfo(lto_debug_model debug, std::string& errMsg)
91{
92    switch (debug) {
93        case LTO_DEBUG_MODEL_NONE:
94            _emitDwarfDebugInfo = false;
95            return false;
96
97        case LTO_DEBUG_MODEL_DWARF:
98            _emitDwarfDebugInfo = true;
99            return false;
100    }
101    errMsg = "unknown debug format";
102    return true;
103}
104
105
106bool LTOCodeGenerator::setCodePICModel(lto_codegen_model model,
107                                                        std::string& errMsg)
108{
109    switch (model) {
110        case LTO_CODEGEN_PIC_MODEL_STATIC:
111        case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
112        case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
113            _codeModel = model;
114            return false;
115    }
116    errMsg = "unknown pic model";
117    return true;
118}
119
120void LTOCodeGenerator::addMustPreserveSymbol(const char* sym)
121{
122    _mustPreserveSymbols[sym] = 1;
123}
124
125
126bool LTOCodeGenerator::writeMergedModules(const char* path, std::string& errMsg)
127{
128    if ( this->determineTarget(errMsg) )
129        return true;
130
131    // mark which symbols can not be internalized
132    this->applyScopeRestrictions();
133
134    // create output file
135    std::ofstream out(path, std::ios_base::out|std::ios::trunc|std::ios::binary);
136    if ( out.fail() ) {
137        errMsg = "could not open bitcode file for writing: ";
138        errMsg += path;
139        return true;
140    }
141
142    // write bitcode to it
143    WriteBitcodeToFile(_linker.getModule(), out);
144    if ( out.fail() ) {
145        errMsg = "could not write bitcode file: ";
146        errMsg += path;
147        return true;
148    }
149
150    return false;
151}
152
153
154const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg)
155{
156    // make unique temp .s file to put generated assembly code
157    sys::Path uniqueAsmPath("lto-llvm.s");
158    if ( uniqueAsmPath.createTemporaryFileOnDisk(true, &errMsg) )
159        return NULL;
160    sys::RemoveFileOnSignal(uniqueAsmPath);
161
162    // generate assembly code
163    std::ofstream asmFile(uniqueAsmPath.c_str());
164    bool genResult = this->generateAssemblyCode(asmFile, errMsg);
165    asmFile.close();
166    if ( genResult ) {
167        if ( uniqueAsmPath.exists() )
168            uniqueAsmPath.eraseFromDisk();
169        return NULL;
170    }
171
172    // make unique temp .o file to put generated object file
173    sys::PathWithStatus uniqueObjPath("lto-llvm.o");
174    if ( uniqueObjPath.createTemporaryFileOnDisk(true, &errMsg) ) {
175        if ( uniqueAsmPath.exists() )
176            uniqueAsmPath.eraseFromDisk();
177        return NULL;
178    }
179    sys::RemoveFileOnSignal(uniqueObjPath);
180
181    // assemble the assembly code
182    const std::string& uniqueObjStr = uniqueObjPath.toString();
183    bool asmResult = this->assemble(uniqueAsmPath.toString(),
184                                                        uniqueObjStr, errMsg);
185    if ( !asmResult ) {
186        // remove old buffer if compile() called twice
187        delete _nativeObjectFile;
188
189        // read .o file into memory buffer
190        _nativeObjectFile = MemoryBuffer::getFile(uniqueObjStr.c_str(),&errMsg);
191    }
192
193    // remove temp files
194    uniqueAsmPath.eraseFromDisk();
195    uniqueObjPath.eraseFromDisk();
196
197    // return buffer, unless error
198    if ( _nativeObjectFile == NULL )
199        return NULL;
200    *length = _nativeObjectFile->getBufferSize();
201    return _nativeObjectFile->getBufferStart();
202}
203
204
205bool LTOCodeGenerator::assemble(const std::string& asmPath,
206                                const std::string& objPath, std::string& errMsg)
207{
208    // find compiler driver
209    const sys::Path gcc = sys::Program::FindProgramByName("gcc");
210    if ( gcc.isEmpty() ) {
211        errMsg = "can't locate gcc";
212        return true;
213    }
214
215    // build argument list
216    std::vector<const char*> args;
217    std::string targetTriple = _linker.getModule()->getTargetTriple();
218    args.push_back(gcc.c_str());
219    if ( targetTriple.find("darwin") != targetTriple.size() ) {
220        if (strncmp(targetTriple.c_str(), "i686-apple-", 11) == 0) {
221            args.push_back("-arch");
222            args.push_back("i386");
223        }
224        else if (strncmp(targetTriple.c_str(), "x86_64-apple-", 13) == 0) {
225            args.push_back("-arch");
226            args.push_back("x86_64");
227        }
228        else if (strncmp(targetTriple.c_str(), "powerpc-apple-", 14) == 0) {
229            args.push_back("-arch");
230            args.push_back("ppc");
231        }
232        else if (strncmp(targetTriple.c_str(), "powerpc64-apple-", 16) == 0) {
233            args.push_back("-arch");
234            args.push_back("ppc64");
235        }
236    }
237    args.push_back("-c");
238    args.push_back("-x");
239    args.push_back("assembler");
240    args.push_back("-o");
241    args.push_back(objPath.c_str());
242    args.push_back(asmPath.c_str());
243    args.push_back(0);
244
245    // invoke assembler
246    if ( sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 0, 0, &errMsg) ) {
247        errMsg = "error in assembly";
248        return true;
249    }
250    return false; // success
251}
252
253
254
255bool LTOCodeGenerator::determineTarget(std::string& errMsg)
256{
257    if ( _target == NULL ) {
258        // create target machine from info for merged modules
259        Module* mergedModule = _linker.getModule();
260        const TargetMachineRegistry::entry* march =
261          TargetMachineRegistry::getClosestStaticTargetForModule(
262                                                       *mergedModule, errMsg);
263        if ( march == NULL )
264            return true;
265
266        // construct LTModule, hand over ownership of module and target
267        std::string FeatureStr =
268          getFeatureString(_linker.getModule()->getTargetTriple().c_str());
269        _target = march->CtorFn(*mergedModule, FeatureStr.c_str());
270    }
271    return false;
272}
273
274void LTOCodeGenerator::applyScopeRestrictions()
275{
276    if ( !_scopeRestrictionsDone ) {
277        Module* mergedModule = _linker.getModule();
278
279        // Start off with a verification pass.
280        PassManager passes;
281        passes.add(createVerifierPass());
282
283        // mark which symbols can not be internalized
284        if ( !_mustPreserveSymbols.empty() ) {
285            Mangler mangler(*mergedModule,
286                                _target->getTargetAsmInfo()->getGlobalPrefix());
287            std::vector<const char*> mustPreserveList;
288            for (Module::iterator f = mergedModule->begin(),
289                                        e = mergedModule->end(); f != e; ++f) {
290                if ( !f->isDeclaration()
291                  && _mustPreserveSymbols.count(mangler.getValueName(f)) )
292                    mustPreserveList.push_back(::strdup(f->getName().c_str()));
293            }
294            for (Module::global_iterator v = mergedModule->global_begin(),
295                                 e = mergedModule->global_end(); v !=  e; ++v) {
296                if ( !v->isDeclaration()
297                  && _mustPreserveSymbols.count(mangler.getValueName(v)) )
298                    mustPreserveList.push_back(::strdup(v->getName().c_str()));
299            }
300            passes.add(createInternalizePass(mustPreserveList));
301        }
302        // apply scope restrictions
303        passes.run(*mergedModule);
304
305        _scopeRestrictionsDone = true;
306    }
307}
308
309/// Optimize merged modules using various IPO passes
310bool LTOCodeGenerator::generateAssemblyCode(std::ostream& out, std::string& errMsg)
311{
312    if (  this->determineTarget(errMsg) )
313        return true;
314
315    // mark which symbols can not be internalized
316    this->applyScopeRestrictions();
317
318    Module* mergedModule = _linker.getModule();
319
320     // If target supports exception handling then enable it now.
321    if ( _target->getTargetAsmInfo()->doesSupportExceptionHandling() )
322        llvm::ExceptionHandling = true;
323
324    // set codegen model
325    switch( _codeModel ) {
326        case LTO_CODEGEN_PIC_MODEL_STATIC:
327            _target->setRelocationModel(Reloc::Static);
328            break;
329        case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
330            _target->setRelocationModel(Reloc::PIC_);
331            break;
332        case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
333            _target->setRelocationModel(Reloc::DynamicNoPIC);
334            break;
335    }
336
337    for (unsigned opt_index = 0, opt_size = _codegenOptions.size();
338         opt_index < opt_size; ++opt_index) {
339      std::vector<const char *> cgOpts;
340      std::string &optString = _codegenOptions[opt_index];
341      for (std::string Opt = getToken(optString);
342           !Opt.empty(); Opt = getToken(optString))
343        cgOpts.push_back(Opt.c_str());
344
345      int pseudo_argc = cgOpts.size()-1;
346      cl::ParseCommandLineOptions(pseudo_argc, (char**)&cgOpts[0]);
347     }
348
349    // Instantiate the pass manager to organize the passes.
350    PassManager passes;
351
352    // Start off with a verification pass.
353    passes.add(createVerifierPass());
354
355    // Add an appropriate TargetData instance for this module...
356    passes.add(new TargetData(*_target->getTargetData()));
357
358    // Propagate constants at call sites into the functions they call.  This
359    // opens opportunities for globalopt (and inlining) by substituting function
360    // pointers passed as arguments to direct uses of functions.
361    passes.add(createIPSCCPPass());
362
363    // Now that we internalized some globals, see if we can hack on them!
364    passes.add(createGlobalOptimizerPass());
365
366    // Linking modules together can lead to duplicated global constants, only
367    // keep one copy of each constant...
368    passes.add(createConstantMergePass());
369
370    // Remove unused arguments from functions...
371    passes.add(createDeadArgEliminationPass());
372
373    // Reduce the code after globalopt and ipsccp.  Both can open up significant
374    // simplification opportunities, and both can propagate functions through
375    // function pointers.  When this happens, we often have to resolve varargs
376    // calls, etc, so let instcombine do this.
377    passes.add(createInstructionCombiningPass());
378    passes.add(createFunctionInliningPass());     // Inline small functions
379    passes.add(createPruneEHPass());              // Remove dead EH info
380    passes.add(createGlobalDCEPass());            // Remove dead functions
381
382    // If we didn't decide to inline a function, check to see if we can
383    // transform it to pass arguments by value instead of by reference.
384    passes.add(createArgumentPromotionPass());
385
386    // The IPO passes may leave cruft around.  Clean up after them.
387    passes.add(createInstructionCombiningPass());
388    passes.add(createJumpThreadingPass());        // Thread jumps.
389    passes.add(createScalarReplAggregatesPass()); // Break up allocas
390
391    // Run a few AA driven optimizations here and now, to cleanup the code.
392    passes.add(createGlobalsModRefPass());        // IP alias analysis
393    passes.add(createLICMPass());                 // Hoist loop invariants
394    passes.add(createGVNPass());                  // Remove common subexprs
395    passes.add(createMemCpyOptPass());            // Remove dead memcpy's
396    passes.add(createDeadStoreEliminationPass()); // Nuke dead stores
397
398    // Cleanup and simplify the code after the scalar optimizations.
399    passes.add(createInstructionCombiningPass());
400    passes.add(createJumpThreadingPass());        // Thread jumps.
401    passes.add(createPromoteMemoryToRegisterPass()); // Cleanup after threading.
402
403
404    // Delete basic blocks, which optimization passes may have killed...
405    passes.add(createCFGSimplificationPass());
406
407    // Now that we have optimized the program, discard unreachable functions...
408    passes.add(createGlobalDCEPass());
409
410    // Make sure everything is still good.
411    passes.add(createVerifierPass());
412
413    FunctionPassManager* codeGenPasses =
414            new FunctionPassManager(new ExistingModuleProvider(mergedModule));
415
416    codeGenPasses->add(new TargetData(*_target->getTargetData()));
417
418    MachineCodeEmitter* mce = NULL;
419
420    switch (_target->addPassesToEmitFile(*codeGenPasses, out,
421                                      TargetMachine::AssemblyFile, true)) {
422        case FileModel::MachOFile:
423            mce = AddMachOWriter(*codeGenPasses, out, *_target);
424            break;
425        case FileModel::ElfFile:
426            mce = AddELFWriter(*codeGenPasses, out, *_target);
427            break;
428        case FileModel::AsmFile:
429            break;
430        case FileModel::Error:
431        case FileModel::None:
432            errMsg = "target file type not supported";
433            return true;
434    }
435
436    if (_target->addPassesToEmitFileFinish(*codeGenPasses, mce, true)) {
437        errMsg = "target does not support generation of this file type";
438        return true;
439    }
440
441    // Run our queue of passes all at once now, efficiently.
442    passes.run(*mergedModule);
443
444    // Run the code generator, and write assembly file
445    codeGenPasses->doInitialization();
446
447    for (Module::iterator
448           it = mergedModule->begin(), e = mergedModule->end(); it != e; ++it)
449      if (!it->isDeclaration())
450        codeGenPasses->run(*it);
451
452    codeGenPasses->doFinalization();
453    return false; // success
454}
455
456
457
458