1 //===-lto.cpp - LLVM Link Time Optimizer ----------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Devang Patel and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implementes link time optimization library. This library is
11 // intended to be used by linker to optimize code at link time.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Module.h"
16 #include "llvm/PassManager.h"
17 #include "llvm/Linker.h"
18 #include "llvm/Constants.h"
19 #include "llvm/DerivedTypes.h"
20 #include "llvm/SymbolTable.h"
21 #include "llvm/Bytecode/Reader.h"
22 #include "llvm/Bytecode/Writer.h"
23 #include "llvm/Support/CommandLine.h"
24 #include "llvm/Support/FileUtilities.h"
25 #include "llvm/Support/SystemUtils.h"
26 #include "llvm/Support/Mangler.h"
27 #include "llvm/System/Program.h"
28 #include "llvm/System/Signals.h"
29 #include "llvm/Analysis/Passes.h"
30 #include "llvm/Analysis/Verifier.h"
31 #include "llvm/Target/SubtargetFeature.h"
32 #include "llvm/Target/TargetData.h"
33 #include "llvm/Target/TargetMachine.h"
34 #include "llvm/Target/TargetMachineRegistry.h"
35 #include "llvm/Transforms/IPO.h"
36 #include "llvm/Transforms/Scalar.h"
37 #include "llvm/Analysis/LoadValueNumbering.h"
38 #include "llvm/LinkTimeOptimizer.h"
45 llvm::LinkTimeOptimizer *createLLVMOptimizer()
47 llvm::LinkTimeOptimizer *l = new llvm::LinkTimeOptimizer();
53 /// If symbol is not used then make it internal and let optimizer takes
55 void LLVMSymbol::mayBeNotUsed() {
56 gv->setLinkage(GlobalValue::InternalLinkage);
60 // FIXME : Take advantage of GlobalPrefix from AsmPrinter
61 static const char *addUnderscore(const char *name) {
62 size_t namelen = strlen(name);
63 char *symName = (char*)malloc(namelen+2);
65 strcpy(&symName[1], name);
69 // Map LLVM LinkageType to LTO LinakgeType
70 static LTOLinkageTypes
71 getLTOLinkageType(GlobalValue *v)
74 if (v->hasExternalLinkage())
75 lt = LTOExternalLinkage;
76 else if (v->hasLinkOnceLinkage())
77 lt = LTOLinkOnceLinkage;
78 else if (v->hasWeakLinkage())
81 // Otherwise it is internal linkage for link time optimizer
82 lt = LTOInternalLinkage;
86 // Find exeternal symbols referenced by VALUE. This is a recursive function.
88 findExternalRefs(Value *value, std::set<std::string> &references,
91 if (GlobalValue *gv = dyn_cast<GlobalValue>(value)) {
92 LTOLinkageTypes lt = getLTOLinkageType(gv);
93 if (lt != LTOInternalLinkage && strncmp (gv->getName().c_str(), "llvm.", 5))
94 references.insert(mangler.getValueName(gv));
96 else if (Constant *c = dyn_cast<Constant>(value))
97 // Handle ConstantExpr, ConstantStruct, ConstantArry etc..
98 for (unsigned i = 0, e = c->getNumOperands(); i != e; ++i)
99 findExternalRefs(c->getOperand(i), references, mangler);
102 /// InputFilename is a LLVM bytecode file. If Module with InputFilename is
103 /// available then return it. Otherwise parseInputFilename.
105 LinkTimeOptimizer::getModule(const std::string &InputFilename)
109 NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str());
110 if (pos != allModules.end())
111 m = allModules[InputFilename.c_str()];
113 m = ParseBytecodeFile(InputFilename);
114 allModules[InputFilename.c_str()] = m;
119 /// InputFilename is a LLVM bytecode file. Read it using bytecode reader.
120 /// Collect global functions and symbol names in symbols vector.
121 /// Collect external references in references vector.
122 /// Return LTO_READ_SUCCESS if there is no error.
124 LinkTimeOptimizer::readLLVMObjectFile(const std::string &InputFilename,
125 NameToSymbolMap &symbols,
126 std::set<std::string> &references)
128 Module *m = getModule(InputFilename);
130 return LTO_READ_FAILURE;
132 // Use mangler to add GlobalPrefix to names to match linker names.
133 // FIXME : Instead of hard coding "-" use GlobalPrefix.
134 Mangler mangler(*m, "_");
136 modules.push_back(m);
138 for (Module::iterator f = m->begin(), e = m->end(); f != e; ++f) {
140 LTOLinkageTypes lt = getLTOLinkageType(f);
142 if (!f->isExternal() && lt != LTOInternalLinkage
143 && strncmp (f->getName().c_str(), "llvm.", 5)) {
144 LLVMSymbol *newSymbol = new LLVMSymbol(lt, f, f->getName(),
145 mangler.getValueName(f));
146 symbols[newSymbol->getMangledName()] = newSymbol;
147 allSymbols[newSymbol->getMangledName()] = newSymbol;
150 // Collect external symbols referenced by this function.
151 for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b)
152 for (BasicBlock::iterator i = b->begin(), be = b->end();
154 for (unsigned count = 0, total = i->getNumOperands();
155 count != total; ++count)
156 findExternalRefs(i->getOperand(count), references, mangler);
159 for (Module::global_iterator v = m->global_begin(), e = m->global_end();
161 LTOLinkageTypes lt = getLTOLinkageType(v);
162 if (!v->isExternal() && lt != LTOInternalLinkage
163 && strncmp (v->getName().c_str(), "llvm.", 5)) {
164 LLVMSymbol *newSymbol = new LLVMSymbol(lt, v, v->getName(),
165 mangler.getValueName(v));
166 symbols[newSymbol->getMangledName()] = newSymbol;
167 allSymbols[newSymbol->getMangledName()] = newSymbol;
169 for (unsigned count = 0, total = v->getNumOperands();
170 count != total; ++count)
171 findExternalRefs(v->getOperand(count), references, mangler);
176 return LTO_READ_SUCCESS;
179 /// Optimize module M using various IPO passes. Use exportList to
180 /// internalize selected symbols. Target platform is selected
181 /// based on information available to module M. No new target
182 /// features are selected.
183 static enum LTOStatus lto_optimize(Module *M, std::ostream &Out,
184 std::vector<const char *> &exportList)
186 // Instantiate the pass manager to organize the passes.
189 // Collect Target info
191 const TargetMachineRegistry::Entry* March =
192 TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err);
195 return LTO_NO_TARGET;
198 std::string Features;
199 std::auto_ptr<TargetMachine> target(March->CtorFn(*M, Features));
201 return LTO_NO_TARGET;
203 TargetMachine &Target = *target.get();
205 // Start off with a verification pass.
206 Passes.add(createVerifierPass());
208 // Add an appropriate TargetData instance for this module...
209 Passes.add(new TargetData(*Target.getTargetData()));
211 // Often if the programmer does not specify proper prototypes for the
212 // functions they are calling, they end up calling a vararg version of the
213 // function that does not get a body filled in (the real function has typed
214 // arguments). This pass merges the two functions.
215 Passes.add(createFunctionResolvingPass());
217 // Internalize symbols if export list is nonemty
218 if (!exportList.empty())
219 Passes.add(createInternalizePass(exportList));
221 // Now that we internalized some globals, see if we can hack on them!
222 Passes.add(createGlobalOptimizerPass());
224 // Linking modules together can lead to duplicated global constants, only
225 // keep one copy of each constant...
226 Passes.add(createConstantMergePass());
228 // If the -s command line option was specified, strip the symbols out of the
229 // resulting program to make it smaller. -s is a GLD option that we are
231 Passes.add(createStripSymbolsPass());
233 // Propagate constants at call sites into the functions they call.
234 Passes.add(createIPConstantPropagationPass());
236 // Remove unused arguments from functions...
237 Passes.add(createDeadArgEliminationPass());
239 Passes.add(createFunctionInliningPass()); // Inline small functions
241 Passes.add(createPruneEHPass()); // Remove dead EH info
243 Passes.add(createGlobalDCEPass()); // Remove dead functions
245 // If we didn't decide to inline a function, check to see if we can
246 // transform it to pass arguments by value instead of by reference.
247 Passes.add(createArgumentPromotionPass());
249 // The IPO passes may leave cruft around. Clean up after them.
250 Passes.add(createInstructionCombiningPass());
252 Passes.add(createScalarReplAggregatesPass()); // Break up allocas
254 // Run a few AA driven optimizations here and now, to cleanup the code.
255 Passes.add(createGlobalsModRefPass()); // IP alias analysis
257 Passes.add(createLICMPass()); // Hoist loop invariants
258 Passes.add(createLoadValueNumberingPass()); // GVN for load instrs
259 Passes.add(createGCSEPass()); // Remove common subexprs
260 Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores
262 // Cleanup and simplify the code after the scalar optimizations.
263 Passes.add(createInstructionCombiningPass());
265 // Delete basic blocks, which optimization passes may have killed...
266 Passes.add(createCFGSimplificationPass());
268 // Now that we have optimized the program, discard unreachable functions...
269 Passes.add(createGlobalDCEPass());
271 // Make sure everything is still good.
272 Passes.add(createVerifierPass());
274 Target.addPassesToEmitFile(Passes, Out, TargetMachine::AssemblyFile, true);
276 // Run our queue of passes all at once now, efficiently.
279 return LTO_OPT_SUCCESS;
282 ///Link all modules together and optimize them using IPO. Generate
283 /// native object file using OutputFilename
284 /// Return appropriate LTOStatus.
286 LinkTimeOptimizer::optimizeModules(const std::string &OutputFilename,
287 std::vector<const char *> &exportList,
288 std::string &targetTriple)
293 std::ios::openmode io_mode =
294 std::ios::out | std::ios::trunc | std::ios::binary;
295 std::string *errMsg = NULL;
296 Module *bigOne = modules[0];
297 Linker theLinker("LinkTimeOptimizer", bigOne, false);
298 for (unsigned i = 1, e = modules.size(); i != e; ++i)
299 if (theLinker.LinkModules(bigOne, modules[i], errMsg))
300 return LTO_MODULE_MERGE_FAILURE;
303 // Enable this when -save-temps is used
304 std::ofstream Out("big.bc", io_mode);
305 WriteBytecodeToFile(bigOne, Out, true);
308 // Strip leading underscore because it was added to match names
310 for (unsigned i = 0, e = exportList.size(); i != e; ++i) {
311 const char *name = exportList[i];
312 NameToSymbolMap::iterator itr = allSymbols.find(name);
313 if (itr != allSymbols.end())
314 exportList[i] = allSymbols[name]->getName();
317 sys::Path tmpAsmFilePath("/tmp/");
319 if (tmpAsmFilePath.createTemporaryFileOnDisk(&ErrMsg)) {
320 std::cerr << "lto: " << ErrMsg << "\n";
321 return LTO_WRITE_FAILURE;
323 sys::RemoveFileOnSignal(tmpAsmFilePath);
325 std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode);
326 if (!asmFile.is_open() || asmFile.bad()) {
327 if (tmpAsmFilePath.exists())
328 tmpAsmFilePath.eraseFromDisk();
329 return LTO_WRITE_FAILURE;
332 enum LTOStatus status = lto_optimize(bigOne, asmFile, exportList);
334 if (status != LTO_OPT_SUCCESS) {
335 tmpAsmFilePath.eraseFromDisk();
339 targetTriple = bigOne->getTargetTriple();
341 // Run GCC to assemble and link the program into native code.
344 // We can't just assemble and link the file with the system assembler
345 // and linker because we don't know where to put the _start symbol.
346 // GCC mysteriously knows how to do it.
347 const sys::Path gcc = FindExecutable("gcc", "/");
349 tmpAsmFilePath.eraseFromDisk();
350 return LTO_ASM_FAILURE;
353 std::vector<const char*> args;
354 args.push_back(gcc.c_str());
355 args.push_back("-c");
356 args.push_back("-x");
357 args.push_back("assembler");
358 args.push_back("-o");
359 args.push_back(OutputFilename.c_str());
360 args.push_back(tmpAsmFilePath.c_str());
363 sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1);
365 tmpAsmFilePath.eraseFromDisk();
367 return LTO_OPT_SUCCESS;