forked from OSchip/llvm-project
110 lines
3.8 KiB
C++
110 lines
3.8 KiB
C++
//===--------- LoopSimplifyCFG.cpp - Loop CFG Simplification Pass ---------===//
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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 the Loop SimplifyCFG Pass. This pass is responsible for
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// basic loop CFG cleanup, primarily to assist other loop passes. If you
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// encounter a noncanonical CFG construct that causes another loop pass to
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// perform suboptimally, this is the place to fix it up.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar/LoopSimplifyCFG.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/AssumptionCache.h"
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#include "llvm/Analysis/BasicAliasAnalysis.h"
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#include "llvm/Analysis/DependenceAnalysis.h"
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#include "llvm/Analysis/GlobalsModRef.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Analysis/ScalarEvolution.h"
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#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
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#include "llvm/Analysis/TargetTransformInfo.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Scalar/LoopPassManager.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Transforms/Utils/LoopUtils.h"
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using namespace llvm;
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#define DEBUG_TYPE "loop-simplifycfg"
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static bool simplifyLoopCFG(Loop &L, DominatorTree &DT, LoopInfo &LI) {
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bool Changed = false;
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// Copy blocks into a temporary array to avoid iterator invalidation issues
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// as we remove them.
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SmallVector<WeakTrackingVH, 16> Blocks(L.blocks());
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for (auto &Block : Blocks) {
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// Attempt to merge blocks in the trivial case. Don't modify blocks which
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// belong to other loops.
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BasicBlock *Succ = cast_or_null<BasicBlock>(Block);
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if (!Succ)
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continue;
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BasicBlock *Pred = Succ->getSinglePredecessor();
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if (!Pred || !Pred->getSingleSuccessor() || LI.getLoopFor(Pred) != &L)
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continue;
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// Pred is going to disappear, so we need to update the loop info.
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if (L.getHeader() == Pred)
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L.moveToHeader(Succ);
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LI.removeBlock(Pred);
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MergeBasicBlockIntoOnlyPred(Succ, &DT);
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Changed = true;
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}
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return Changed;
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}
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PreservedAnalyses LoopSimplifyCFGPass::run(Loop &L, LoopAnalysisManager &AM,
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LoopStandardAnalysisResults &AR,
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LPMUpdater &) {
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if (!simplifyLoopCFG(L, AR.DT, AR.LI))
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return PreservedAnalyses::all();
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return getLoopPassPreservedAnalyses();
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}
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namespace {
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class LoopSimplifyCFGLegacyPass : public LoopPass {
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public:
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static char ID; // Pass ID, replacement for typeid
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LoopSimplifyCFGLegacyPass() : LoopPass(ID) {
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initializeLoopSimplifyCFGLegacyPassPass(*PassRegistry::getPassRegistry());
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}
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bool runOnLoop(Loop *L, LPPassManager &) override {
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if (skipLoop(L))
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return false;
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DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
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LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
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return simplifyLoopCFG(*L, DT, LI);
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addPreserved<DependenceAnalysisWrapperPass>();
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getLoopAnalysisUsage(AU);
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}
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};
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}
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char LoopSimplifyCFGLegacyPass::ID = 0;
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INITIALIZE_PASS_BEGIN(LoopSimplifyCFGLegacyPass, "loop-simplifycfg",
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"Simplify loop CFG", false, false)
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INITIALIZE_PASS_DEPENDENCY(LoopPass)
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INITIALIZE_PASS_END(LoopSimplifyCFGLegacyPass, "loop-simplifycfg",
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"Simplify loop CFG", false, false)
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Pass *llvm::createLoopSimplifyCFGPass() {
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return new LoopSimplifyCFGLegacyPass();
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}
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