Mercurial > hg > Members > tobaru > cbc > CbC_llvm
view lib/Transforms/Scalar/ConstantProp.cpp @ 83:60c9769439b8
LLVM 3.7
author | Tatsuki IHA <e125716@ie.u-ryukyu.ac.jp> |
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date | Wed, 18 Feb 2015 14:55:36 +0900 |
parents | 54457678186b |
children | afa8332a0e37 |
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//===- ConstantProp.cpp - Code to perform Simple Constant Propagation -----===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements constant propagation and merging: // // Specifically, this: // * Converts instructions like "add int 1, 2" into 3 // // Notice that: // * This pass has a habit of making definitions be dead. It is a good idea // to run a DIE pass sometime after running this pass. // //===----------------------------------------------------------------------===// #include "llvm/Transforms/Scalar.h" #include "llvm/ADT/Statistic.h" #include "llvm/Analysis/ConstantFolding.h" #include "llvm/IR/Constant.h" #include "llvm/IR/DataLayout.h" #include "llvm/IR/InstIterator.h" #include "llvm/IR/Instruction.h" #include "llvm/Pass.h" #include "llvm/Analysis/TargetLibraryInfo.h" #include <set> using namespace llvm; #define DEBUG_TYPE "constprop" STATISTIC(NumInstKilled, "Number of instructions killed"); namespace { struct ConstantPropagation : public FunctionPass { static char ID; // Pass identification, replacement for typeid ConstantPropagation() : FunctionPass(ID) { initializeConstantPropagationPass(*PassRegistry::getPassRegistry()); } bool runOnFunction(Function &F) override; void getAnalysisUsage(AnalysisUsage &AU) const override { AU.setPreservesCFG(); AU.addRequired<TargetLibraryInfoWrapperPass>(); } }; } char ConstantPropagation::ID = 0; INITIALIZE_PASS_BEGIN(ConstantPropagation, "constprop", "Simple constant propagation", false, false) INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) INITIALIZE_PASS_END(ConstantPropagation, "constprop", "Simple constant propagation", false, false) FunctionPass *llvm::createConstantPropagationPass() { return new ConstantPropagation(); } bool ConstantPropagation::runOnFunction(Function &F) { // Initialize the worklist to all of the instructions ready to process... std::set<Instruction*> WorkList; for(inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i) { WorkList.insert(&*i); } bool Changed = false; DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>(); const DataLayout *DL = DLP ? &DLP->getDataLayout() : nullptr; TargetLibraryInfo *TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); while (!WorkList.empty()) { Instruction *I = *WorkList.begin(); WorkList.erase(WorkList.begin()); // Get an element from the worklist... if (!I->use_empty()) // Don't muck with dead instructions... if (Constant *C = ConstantFoldInstruction(I, DL, TLI)) { // Add all of the users of this instruction to the worklist, they might // be constant propagatable now... for (User *U : I->users()) WorkList.insert(cast<Instruction>(U)); // Replace all of the uses of a variable with uses of the constant. I->replaceAllUsesWith(C); // Remove the dead instruction. WorkList.erase(I); I->eraseFromParent(); // We made a change to the function... Changed = true; ++NumInstKilled; } } return Changed; }