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Diffstat (limited to 'tools/lto/lto.cpp')
| -rw-r--r-- | tools/lto/lto.cpp | 330 |
1 files changed, 330 insertions, 0 deletions
diff --git a/tools/lto/lto.cpp b/tools/lto/lto.cpp new file mode 100644 index 0000000..3f3e8f9 --- /dev/null +++ b/tools/lto/lto.cpp @@ -0,0 +1,330 @@ +//===-lto.cpp - LLVM Link Time Optimizer ----------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file was developed by Devang Patel and is distributed under +// the University of Illinois Open Source License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implementes link time optimization library. This library is +// intended to be used by linker to optimize code at link time. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Module.h" +#include "llvm/PassManager.h" +#include "llvm/Linker.h" +#include "llvm/Constants.h" +#include "llvm/DerivedTypes.h" +#include "llvm/SymbolTable.h" +#include "llvm/Bytecode/Reader.h" +#include "llvm/Bytecode/Writer.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/FileUtilities.h" +#include "llvm/Support/SystemUtils.h" +#include "llvm/System/Program.h" +#include "llvm/System/Signals.h" +#include "llvm/Analysis/Passes.h" +#include "llvm/Analysis/Verifier.h" +#include "llvm/Target/SubtargetFeature.h" +#include "llvm/Target/TargetData.h" +#include "llvm/Target/TargetMachine.h" +#include "llvm/Target/TargetMachineRegistry.h" +#include "llvm/Transforms/IPO.h" +#include "llvm/Transforms/Scalar.h" +#include "llvm/Analysis/LoadValueNumbering.h" +#include "llvm/LinkTimeOptimizer.h" +#include <fstream> +#include <iostream> + +using namespace llvm; + +extern "C" +llvm::LinkTimeOptimizer *createLLVMOptimizer() +{ + llvm::LinkTimeOptimizer *l = new llvm::LinkTimeOptimizer(); + return l; +} + + + +/// If symbol is not used then make it internal and let optimizer takes +/// care of it. +void LLVMSymbol::mayBeNotUsed() { + gv->setLinkage(GlobalValue::InternalLinkage); +} + +// Helper routine +// FIXME : Take advantage of GlobalPrefix from AsmPrinter +static const char *addUnderscore(const char *name) { + size_t namelen = strlen(name); + char *symName = (char*)malloc(namelen+2); + symName[0] = '_'; + strcpy(&symName[1], name); + return symName; +} + +// Map LLVM LinkageType to LTO LinakgeType +static LTOLinkageTypes +getLTOLinkageType(GlobalValue *v) +{ + LTOLinkageTypes lt; + if (v->hasExternalLinkage()) + lt = LTOExternalLinkage; + else if (v->hasLinkOnceLinkage()) + lt = LTOLinkOnceLinkage; + else if (v->hasWeakLinkage()) + lt = LTOWeakLinkage; + else + // Otherwise it is internal linkage for link time optimizer + lt = LTOInternalLinkage; + return lt; +} + +// Find exeternal symbols referenced by VALUE. This is a recursive function. +static void +findExternalRefs(Value *value, std::set<const char *> &references) { + + if (ConstantExpr *ce = dyn_cast<ConstantExpr>(value)) + for (unsigned i = 0, e = ce->getNumOperands(); i != e; ++i) + findExternalRefs(ce->getOperand(i), references); + else if (GlobalValue *gv = dyn_cast<GlobalValue>(value)) { + LTOLinkageTypes lt = getLTOLinkageType(gv); + if (lt != LTOInternalLinkage && strncmp (gv->getName().c_str(), "llvm.", 5)) + references.insert(addUnderscore(gv->getName().c_str())); + } +} + +/// InputFilename is a LLVM bytecode file. Read it using bytecode reader. +/// Collect global functions and symbol names in symbols vector. +/// Collect external references in references vector. +/// Return LTO_READ_SUCCESS if there is no error. +enum LTOStatus +LinkTimeOptimizer::readLLVMObjectFile(const std::string &InputFilename, + NameToSymbolMap &symbols, + std::set<const char *> &references) +{ + Module *m = ParseBytecodeFile(InputFilename); + if (!m) + return LTO_READ_FAILURE; + + modules.push_back(m); + + for (Module::iterator f = m->begin(), e = m->end(); f != e; ++f) { + + LTOLinkageTypes lt = getLTOLinkageType(f); + + if (!f->isExternal() && lt != LTOInternalLinkage + && strncmp (f->getName().c_str(), "llvm.", 5)) { + const char *name = addUnderscore(f->getName().c_str()); + LLVMSymbol *newSymbol = new LLVMSymbol(lt, f); + symbols[name] = newSymbol; + allSymbols[name] = newSymbol; + } + + // Collect external symbols referenced by this function. + for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b) + for (BasicBlock::iterator i = b->begin(), be = b->end(); + i != be; ++i) + for (unsigned count = 0, total = i->getNumOperands(); + count != total; ++count) + findExternalRefs(i->getOperand(count), references); + } + + for (Module::global_iterator v = m->global_begin(), e = m->global_end(); + v != e; ++v) { + LTOLinkageTypes lt = getLTOLinkageType(v); + if (!v->isExternal() && lt != LTOInternalLinkage + && strncmp (v->getName().c_str(), "llvm.", 5)) { + const char *name = addUnderscore(v->getName().c_str()); + LLVMSymbol *newSymbol = new LLVMSymbol(lt,v); + symbols[name] = newSymbol; + } + } + + return LTO_READ_SUCCESS; +} + +/// Optimize module M using various IPO passes. Use exportList to +/// internalize selected symbols. Target platform is selected +/// based on information available to module M. No new target +/// features are selected. +static enum LTOStatus lto_optimize(Module *M, std::ostream &Out, + std::vector<const char *> &exportList) +{ + // Instantiate the pass manager to organize the passes. + PassManager Passes; + + // Collect Target info + std::string Err; + const TargetMachineRegistry::Entry* March = + TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err); + + if (March == 0) + return LTO_NO_TARGET; + + // Create target + std::string Features; + std::auto_ptr<TargetMachine> target(March->CtorFn(*M, Features)); + if (!target.get()) + return LTO_NO_TARGET; + + TargetMachine &Target = *target.get(); + + // Start off with a verification pass. + Passes.add(createVerifierPass()); + + // Add an appropriate TargetData instance for this module... + Passes.add(new TargetData(*Target.getTargetData())); + + // Often if the programmer does not specify proper prototypes for the + // functions they are calling, they end up calling a vararg version of the + // function that does not get a body filled in (the real function has typed + // arguments). This pass merges the two functions. + Passes.add(createFunctionResolvingPass()); + + // Internalize symbols if export list is nonemty + if (!exportList.empty()) + Passes.add(createInternalizePass(exportList)); + + // Now that we internalized some globals, see if we can hack on them! + Passes.add(createGlobalOptimizerPass()); + + // Linking modules together can lead to duplicated global constants, only + // keep one copy of each constant... + Passes.add(createConstantMergePass()); + + // If the -s command line option was specified, strip the symbols out of the + // resulting program to make it smaller. -s is a GLD option that we are + // supporting. + Passes.add(createStripSymbolsPass()); + + // Propagate constants at call sites into the functions they call. + Passes.add(createIPConstantPropagationPass()); + + // Remove unused arguments from functions... + Passes.add(createDeadArgEliminationPass()); + + Passes.add(createFunctionInliningPass()); // Inline small functions + + Passes.add(createPruneEHPass()); // Remove dead EH info + + Passes.add(createGlobalDCEPass()); // Remove dead functions + + // If we didn't decide to inline a function, check to see if we can + // transform it to pass arguments by value instead of by reference. + Passes.add(createArgumentPromotionPass()); + + // The IPO passes may leave cruft around. Clean up after them. + Passes.add(createInstructionCombiningPass()); + + Passes.add(createScalarReplAggregatesPass()); // Break up allocas + + // Run a few AA driven optimizations here and now, to cleanup the code. + Passes.add(createGlobalsModRefPass()); // IP alias analysis + + Passes.add(createLICMPass()); // Hoist loop invariants + Passes.add(createLoadValueNumberingPass()); // GVN for load instrs + Passes.add(createGCSEPass()); // Remove common subexprs + Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores + + // Cleanup and simplify the code after the scalar optimizations. + Passes.add(createInstructionCombiningPass()); + + // Delete basic blocks, which optimization passes may have killed... + Passes.add(createCFGSimplificationPass()); + + // Now that we have optimized the program, discard unreachable functions... + Passes.add(createGlobalDCEPass()); + + // Make sure everything is still good. + Passes.add(createVerifierPass()); + + Target.addPassesToEmitFile(Passes, Out, TargetMachine::AssemblyFile, true); + + // Run our queue of passes all at once now, efficiently. + Passes.run(*M); + + return LTO_OPT_SUCCESS; +} + +///Link all modules together and optimize them using IPO. Generate +/// native object file using OutputFilename +/// Return appropriate LTOStatus. +enum LTOStatus +LinkTimeOptimizer::optimizeModules(const std::string &OutputFilename, + std::vector<const char *> &exportList) +{ + if (modules.empty()) + return LTO_NO_WORK; + + std::ios::openmode io_mode = + std::ios::out | std::ios::trunc | std::ios::binary; + std::string *errMsg = NULL; + Module *bigOne = modules[0]; + Linker theLinker("LinkTimeOptimizer", bigOne, false); + for (unsigned i = 1, e = modules.size(); i != e; ++i) + if (theLinker.LinkModules(bigOne, modules[i], errMsg)) + return LTO_MODULE_MERGE_FAILURE; + +#if 0 + // Enable this when -save-temps is used + std::ofstream Out("big.bc", io_mode); + WriteBytecodeToFile(bigOne, Out, true); +#endif + + // Strip leading underscore because it was added to match names + // seen by liner. + for (unsigned i = 0, e = exportList.size(); i != e; ++i) { + const char *name = exportList[i]; + if (strlen(name) > 2 && name[0] == '_') + exportList[i] = &name[1]; + } + + sys::Path tmpAsmFilePath("/tmp/"); + tmpAsmFilePath.createTemporaryFileOnDisk(); + sys::RemoveFileOnSignal(tmpAsmFilePath); + + std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode); + if (!asmFile.is_open() || asmFile.bad()) { + if (tmpAsmFilePath.exists()) + tmpAsmFilePath.eraseFromDisk(); + return LTO_WRITE_FAILURE; + } + + enum LTOStatus status = lto_optimize(bigOne, asmFile, exportList); + asmFile.close(); + if (status != LTO_OPT_SUCCESS) { + tmpAsmFilePath.eraseFromDisk(); + return status; + } + + // Run GCC to assemble and link the program into native code. + // + // Note: + // We can't just assemble and link the file with the system assembler + // and linker because we don't know where to put the _start symbol. + // GCC mysteriously knows how to do it. + const sys::Path gcc = FindExecutable("gcc", "/"); + if (gcc.isEmpty()) { + tmpAsmFilePath.eraseFromDisk(); + return LTO_ASM_FAILURE; + } + + std::vector<const char*> args; + args.push_back(gcc.c_str()); + args.push_back("-c"); + args.push_back("-x"); + args.push_back("assembler"); + args.push_back("-o"); + args.push_back(OutputFilename.c_str()); + args.push_back(tmpAsmFilePath.c_str()); + args.push_back(0); + + int R1 = sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1); + + tmpAsmFilePath.eraseFromDisk(); + + return LTO_OPT_SUCCESS; +} |