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a89d47f54d
dynamic library that linker can use to optimize llvm byte codes at link time. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29494 91177308-0d34-0410-b5e6-96231b3b80d8
331 lines
11 KiB
C++
331 lines
11 KiB
C++
//===-lto.cpp - LLVM Link Time Optimizer ----------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Devang Patel and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implementes link time optimization library. This library is
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// intended to be used by linker to optimize code at link time.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Module.h"
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#include "llvm/PassManager.h"
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#include "llvm/Linker.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/SymbolTable.h"
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#include "llvm/Bytecode/Reader.h"
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#include "llvm/Bytecode/Writer.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/FileUtilities.h"
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#include "llvm/Support/SystemUtils.h"
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#include "llvm/System/Program.h"
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#include "llvm/System/Signals.h"
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#include "llvm/Analysis/Passes.h"
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#include "llvm/Analysis/Verifier.h"
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#include "llvm/Target/SubtargetFeature.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetMachineRegistry.h"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Analysis/LoadValueNumbering.h"
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#include "llvm/LinkTimeOptimizer.h"
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#include <fstream>
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#include <iostream>
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using namespace llvm;
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extern "C"
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llvm::LinkTimeOptimizer *createLLVMOptimizer()
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{
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llvm::LinkTimeOptimizer *l = new llvm::LinkTimeOptimizer();
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return l;
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}
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/// If symbol is not used then make it internal and let optimizer takes
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/// care of it.
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void LLVMSymbol::mayBeNotUsed() {
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gv->setLinkage(GlobalValue::InternalLinkage);
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}
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// Helper routine
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// FIXME : Take advantage of GlobalPrefix from AsmPrinter
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static const char *addUnderscore(const char *name) {
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size_t namelen = strlen(name);
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char *symName = (char*)malloc(namelen+2);
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symName[0] = '_';
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strcpy(&symName[1], name);
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return symName;
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}
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// Map LLVM LinkageType to LTO LinakgeType
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static LTOLinkageTypes
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getLTOLinkageType(GlobalValue *v)
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{
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LTOLinkageTypes lt;
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if (v->hasExternalLinkage())
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lt = LTOExternalLinkage;
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else if (v->hasLinkOnceLinkage())
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lt = LTOLinkOnceLinkage;
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else if (v->hasWeakLinkage())
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lt = LTOWeakLinkage;
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else
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// Otherwise it is internal linkage for link time optimizer
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lt = LTOInternalLinkage;
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return lt;
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}
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// Find exeternal symbols referenced by VALUE. This is a recursive function.
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static void
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findExternalRefs(Value *value, std::set<const char *> &references) {
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if (ConstantExpr *ce = dyn_cast<ConstantExpr>(value))
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for (unsigned i = 0, e = ce->getNumOperands(); i != e; ++i)
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findExternalRefs(ce->getOperand(i), references);
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else if (GlobalValue *gv = dyn_cast<GlobalValue>(value)) {
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LTOLinkageTypes lt = getLTOLinkageType(gv);
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if (lt != LTOInternalLinkage && strncmp (gv->getName().c_str(), "llvm.", 5))
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references.insert(addUnderscore(gv->getName().c_str()));
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}
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}
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/// InputFilename is a LLVM bytecode file. Read it using bytecode reader.
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/// Collect global functions and symbol names in symbols vector.
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/// Collect external references in references vector.
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/// Return LTO_READ_SUCCESS if there is no error.
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enum LTOStatus
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LinkTimeOptimizer::readLLVMObjectFile(const std::string &InputFilename,
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NameToSymbolMap &symbols,
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std::set<const char *> &references)
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{
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Module *m = ParseBytecodeFile(InputFilename);
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if (!m)
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return LTO_READ_FAILURE;
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modules.push_back(m);
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for (Module::iterator f = m->begin(), e = m->end(); f != e; ++f) {
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LTOLinkageTypes lt = getLTOLinkageType(f);
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if (!f->isExternal() && lt != LTOInternalLinkage
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&& strncmp (f->getName().c_str(), "llvm.", 5)) {
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const char *name = addUnderscore(f->getName().c_str());
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LLVMSymbol *newSymbol = new LLVMSymbol(lt, f);
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symbols[name] = newSymbol;
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allSymbols[name] = newSymbol;
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}
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// Collect external symbols referenced by this function.
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for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b)
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for (BasicBlock::iterator i = b->begin(), be = b->end();
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i != be; ++i)
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for (unsigned count = 0, total = i->getNumOperands();
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count != total; ++count)
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findExternalRefs(i->getOperand(count), references);
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}
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for (Module::global_iterator v = m->global_begin(), e = m->global_end();
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v != e; ++v) {
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LTOLinkageTypes lt = getLTOLinkageType(v);
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if (!v->isExternal() && lt != LTOInternalLinkage
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&& strncmp (v->getName().c_str(), "llvm.", 5)) {
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const char *name = addUnderscore(v->getName().c_str());
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LLVMSymbol *newSymbol = new LLVMSymbol(lt,v);
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symbols[name] = newSymbol;
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}
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}
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return LTO_READ_SUCCESS;
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}
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/// Optimize module M using various IPO passes. Use exportList to
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/// internalize selected symbols. Target platform is selected
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/// based on information available to module M. No new target
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/// features are selected.
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static enum LTOStatus lto_optimize(Module *M, std::ostream &Out,
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std::vector<const char *> &exportList)
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{
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// Instantiate the pass manager to organize the passes.
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PassManager Passes;
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// Collect Target info
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std::string Err;
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const TargetMachineRegistry::Entry* March =
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TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err);
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if (March == 0)
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return LTO_NO_TARGET;
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// Create target
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std::string Features;
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std::auto_ptr<TargetMachine> target(March->CtorFn(*M, Features));
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if (!target.get())
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return LTO_NO_TARGET;
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TargetMachine &Target = *target.get();
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// Start off with a verification pass.
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Passes.add(createVerifierPass());
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// Add an appropriate TargetData instance for this module...
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Passes.add(new TargetData(*Target.getTargetData()));
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// Often if the programmer does not specify proper prototypes for the
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// functions they are calling, they end up calling a vararg version of the
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// function that does not get a body filled in (the real function has typed
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// arguments). This pass merges the two functions.
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Passes.add(createFunctionResolvingPass());
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// Internalize symbols if export list is nonemty
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if (!exportList.empty())
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Passes.add(createInternalizePass(exportList));
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// Now that we internalized some globals, see if we can hack on them!
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Passes.add(createGlobalOptimizerPass());
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// Linking modules together can lead to duplicated global constants, only
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// keep one copy of each constant...
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Passes.add(createConstantMergePass());
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// If the -s command line option was specified, strip the symbols out of the
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// resulting program to make it smaller. -s is a GLD option that we are
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// supporting.
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Passes.add(createStripSymbolsPass());
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// Propagate constants at call sites into the functions they call.
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Passes.add(createIPConstantPropagationPass());
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// Remove unused arguments from functions...
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Passes.add(createDeadArgEliminationPass());
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Passes.add(createFunctionInliningPass()); // Inline small functions
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Passes.add(createPruneEHPass()); // Remove dead EH info
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Passes.add(createGlobalDCEPass()); // Remove dead functions
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// If we didn't decide to inline a function, check to see if we can
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// transform it to pass arguments by value instead of by reference.
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Passes.add(createArgumentPromotionPass());
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// The IPO passes may leave cruft around. Clean up after them.
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Passes.add(createInstructionCombiningPass());
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Passes.add(createScalarReplAggregatesPass()); // Break up allocas
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// Run a few AA driven optimizations here and now, to cleanup the code.
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Passes.add(createGlobalsModRefPass()); // IP alias analysis
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Passes.add(createLICMPass()); // Hoist loop invariants
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Passes.add(createLoadValueNumberingPass()); // GVN for load instrs
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Passes.add(createGCSEPass()); // Remove common subexprs
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Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores
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// Cleanup and simplify the code after the scalar optimizations.
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Passes.add(createInstructionCombiningPass());
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// Delete basic blocks, which optimization passes may have killed...
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Passes.add(createCFGSimplificationPass());
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// Now that we have optimized the program, discard unreachable functions...
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Passes.add(createGlobalDCEPass());
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// Make sure everything is still good.
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Passes.add(createVerifierPass());
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Target.addPassesToEmitFile(Passes, Out, TargetMachine::AssemblyFile, true);
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// Run our queue of passes all at once now, efficiently.
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Passes.run(*M);
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return LTO_OPT_SUCCESS;
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}
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///Link all modules together and optimize them using IPO. Generate
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/// native object file using OutputFilename
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/// Return appropriate LTOStatus.
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enum LTOStatus
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LinkTimeOptimizer::optimizeModules(const std::string &OutputFilename,
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std::vector<const char *> &exportList)
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{
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if (modules.empty())
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return LTO_NO_WORK;
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std::ios::openmode io_mode =
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std::ios::out | std::ios::trunc | std::ios::binary;
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std::string *errMsg = NULL;
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Module *bigOne = modules[0];
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Linker theLinker("LinkTimeOptimizer", bigOne, false);
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for (unsigned i = 1, e = modules.size(); i != e; ++i)
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if (theLinker.LinkModules(bigOne, modules[i], errMsg))
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return LTO_MODULE_MERGE_FAILURE;
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#if 0
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// Enable this when -save-temps is used
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std::ofstream Out("big.bc", io_mode);
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WriteBytecodeToFile(bigOne, Out, true);
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#endif
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// Strip leading underscore because it was added to match names
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// seen by liner.
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for (unsigned i = 0, e = exportList.size(); i != e; ++i) {
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const char *name = exportList[i];
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if (strlen(name) > 2 && name[0] == '_')
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exportList[i] = &name[1];
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}
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sys::Path tmpAsmFilePath("/tmp/");
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tmpAsmFilePath.createTemporaryFileOnDisk();
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sys::RemoveFileOnSignal(tmpAsmFilePath);
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std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode);
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if (!asmFile.is_open() || asmFile.bad()) {
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if (tmpAsmFilePath.exists())
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tmpAsmFilePath.eraseFromDisk();
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return LTO_WRITE_FAILURE;
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}
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enum LTOStatus status = lto_optimize(bigOne, asmFile, exportList);
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asmFile.close();
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if (status != LTO_OPT_SUCCESS) {
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tmpAsmFilePath.eraseFromDisk();
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return status;
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}
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// Run GCC to assemble and link the program into native code.
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//
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// Note:
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// We can't just assemble and link the file with the system assembler
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// and linker because we don't know where to put the _start symbol.
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// GCC mysteriously knows how to do it.
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const sys::Path gcc = FindExecutable("gcc", "/");
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if (gcc.isEmpty()) {
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tmpAsmFilePath.eraseFromDisk();
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return LTO_ASM_FAILURE;
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}
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std::vector<const char*> args;
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args.push_back(gcc.c_str());
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args.push_back("-c");
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args.push_back("-x");
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args.push_back("assembler");
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args.push_back("-o");
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args.push_back(OutputFilename.c_str());
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args.push_back(tmpAsmFilePath.c_str());
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args.push_back(0);
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int R1 = sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1);
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tmpAsmFilePath.eraseFromDisk();
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return LTO_OPT_SUCCESS;
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}
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