mirror of
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0b8c9a80f2
into their new header subdirectory: include/llvm/IR. This matches the directory structure of lib, and begins to correct a long standing point of file layout clutter in LLVM. There are still more header files to move here, but I wanted to handle them in separate commits to make tracking what files make sense at each layer easier. The only really questionable files here are the target intrinsic tablegen files. But that's a battle I'd rather not fight today. I've updated both CMake and Makefile build systems (I think, and my tests think, but I may have missed something). I've also re-sorted the includes throughout the project. I'll be committing updates to Clang, DragonEgg, and Polly momentarily. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171366 91177308-0d34-0410-b5e6-96231b3b80d8
135 lines
4.3 KiB
C++
135 lines
4.3 KiB
C++
//===- DCE.cpp - Code to perform dead code elimination --------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements dead inst elimination and dead code elimination.
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//
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// Dead Inst Elimination performs a single pass over the function removing
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// instructions that are obviously dead. Dead Code Elimination is similar, but
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// it rechecks instructions that were used by removed instructions to see if
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// they are newly dead.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "dce"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/IR/Instruction.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/InstIterator.h"
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#include "llvm/Target/TargetLibraryInfo.h"
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#include "llvm/Transforms/Utils/Local.h"
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using namespace llvm;
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STATISTIC(DIEEliminated, "Number of insts removed by DIE pass");
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STATISTIC(DCEEliminated, "Number of insts removed");
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namespace {
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//===--------------------------------------------------------------------===//
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// DeadInstElimination pass implementation
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//
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struct DeadInstElimination : public BasicBlockPass {
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static char ID; // Pass identification, replacement for typeid
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DeadInstElimination() : BasicBlockPass(ID) {
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initializeDeadInstEliminationPass(*PassRegistry::getPassRegistry());
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}
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virtual bool runOnBasicBlock(BasicBlock &BB) {
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TargetLibraryInfo *TLI = getAnalysisIfAvailable<TargetLibraryInfo>();
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bool Changed = false;
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for (BasicBlock::iterator DI = BB.begin(); DI != BB.end(); ) {
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Instruction *Inst = DI++;
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if (isInstructionTriviallyDead(Inst, TLI)) {
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Inst->eraseFromParent();
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Changed = true;
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++DIEEliminated;
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}
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}
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return Changed;
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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}
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};
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}
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char DeadInstElimination::ID = 0;
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INITIALIZE_PASS(DeadInstElimination, "die",
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"Dead Instruction Elimination", false, false)
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Pass *llvm::createDeadInstEliminationPass() {
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return new DeadInstElimination();
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}
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namespace {
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//===--------------------------------------------------------------------===//
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// DeadCodeElimination pass implementation
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//
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struct DCE : public FunctionPass {
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static char ID; // Pass identification, replacement for typeid
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DCE() : FunctionPass(ID) {
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initializeDCEPass(*PassRegistry::getPassRegistry());
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}
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virtual bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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}
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};
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}
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char DCE::ID = 0;
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INITIALIZE_PASS(DCE, "dce", "Dead Code Elimination", false, false)
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bool DCE::runOnFunction(Function &F) {
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TargetLibraryInfo *TLI = getAnalysisIfAvailable<TargetLibraryInfo>();
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// Start out with all of the instructions in the worklist...
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std::vector<Instruction*> WorkList;
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for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
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WorkList.push_back(&*i);
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// Loop over the worklist finding instructions that are dead. If they are
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// dead make them drop all of their uses, making other instructions
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// potentially dead, and work until the worklist is empty.
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//
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bool MadeChange = false;
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while (!WorkList.empty()) {
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Instruction *I = WorkList.back();
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WorkList.pop_back();
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if (isInstructionTriviallyDead(I, TLI)) { // If the instruction is dead.
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// Loop over all of the values that the instruction uses, if there are
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// instructions being used, add them to the worklist, because they might
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// go dead after this one is removed.
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//
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for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
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if (Instruction *Used = dyn_cast<Instruction>(*OI))
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WorkList.push_back(Used);
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// Remove the instruction.
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I->eraseFromParent();
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// Remove the instruction from the worklist if it still exists in it.
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WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
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WorkList.end());
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MadeChange = true;
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++DCEEliminated;
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}
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}
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return MadeChange;
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}
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FunctionPass *llvm::createDeadCodeEliminationPass() {
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return new DCE();
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}
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