1 //===- LoopRotation.cpp - Loop Rotation Pass ------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements Loop Rotation Pass. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "llvm/Transforms/Scalar/LoopRotation.h" 14 #include "llvm/ADT/Statistic.h" 15 #include "llvm/Analysis/InstructionSimplify.h" 16 #include "llvm/Analysis/LoopPass.h" 17 #include "llvm/Analysis/MemorySSA.h" 18 #include "llvm/Analysis/MemorySSAUpdater.h" 19 #include "llvm/Analysis/ScalarEvolution.h" 20 #include "llvm/Analysis/TargetTransformInfo.h" 21 #include "llvm/InitializePasses.h" 22 #include "llvm/Support/CommandLine.h" 23 #include "llvm/Support/Debug.h" 24 #include "llvm/Transforms/Scalar.h" 25 #include "llvm/Transforms/Scalar/LoopPassManager.h" 26 #include "llvm/Transforms/Utils/LoopRotationUtils.h" 27 #include "llvm/Transforms/Utils/LoopUtils.h" 28 using namespace llvm; 29 30 #define DEBUG_TYPE "loop-rotate" 31 32 static cl::opt<unsigned> DefaultRotationThreshold( 33 "rotation-max-header-size", cl::init(16), cl::Hidden, 34 cl::desc("The default maximum header size for automatic loop rotation")); 35 36 LoopRotatePass::LoopRotatePass(bool EnableHeaderDuplication) 37 : EnableHeaderDuplication(EnableHeaderDuplication) {} 38 39 PreservedAnalyses LoopRotatePass::run(Loop &L, LoopAnalysisManager &AM, 40 LoopStandardAnalysisResults &AR, 41 LPMUpdater &) { 42 int Threshold = EnableHeaderDuplication ? DefaultRotationThreshold : 0; 43 const DataLayout &DL = L.getHeader()->getModule()->getDataLayout(); 44 const SimplifyQuery SQ = getBestSimplifyQuery(AR, DL); 45 46 Optional<MemorySSAUpdater> MSSAU; 47 if (AR.MSSA) 48 MSSAU = MemorySSAUpdater(AR.MSSA); 49 bool Changed = LoopRotation(&L, &AR.LI, &AR.TTI, &AR.AC, &AR.DT, &AR.SE, 50 MSSAU.hasValue() ? MSSAU.getPointer() : nullptr, 51 SQ, false, Threshold, false); 52 53 if (!Changed) 54 return PreservedAnalyses::all(); 55 56 if (AR.MSSA && VerifyMemorySSA) 57 AR.MSSA->verifyMemorySSA(); 58 59 auto PA = getLoopPassPreservedAnalyses(); 60 if (AR.MSSA) 61 PA.preserve<MemorySSAAnalysis>(); 62 return PA; 63 } 64 65 namespace { 66 67 class LoopRotateLegacyPass : public LoopPass { 68 unsigned MaxHeaderSize; 69 70 public: 71 static char ID; // Pass ID, replacement for typeid 72 LoopRotateLegacyPass(int SpecifiedMaxHeaderSize = -1) : LoopPass(ID) { 73 initializeLoopRotateLegacyPassPass(*PassRegistry::getPassRegistry()); 74 if (SpecifiedMaxHeaderSize == -1) 75 MaxHeaderSize = DefaultRotationThreshold; 76 else 77 MaxHeaderSize = unsigned(SpecifiedMaxHeaderSize); 78 } 79 80 // LCSSA form makes instruction renaming easier. 81 void getAnalysisUsage(AnalysisUsage &AU) const override { 82 AU.addRequired<AssumptionCacheTracker>(); 83 AU.addRequired<TargetTransformInfoWrapperPass>(); 84 if (EnableMSSALoopDependency) 85 AU.addPreserved<MemorySSAWrapperPass>(); 86 getLoopAnalysisUsage(AU); 87 } 88 89 bool runOnLoop(Loop *L, LPPassManager &LPM) override { 90 if (skipLoop(L)) 91 return false; 92 Function &F = *L->getHeader()->getParent(); 93 94 auto *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); 95 const auto *TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F); 96 auto *AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); 97 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 98 auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE(); 99 const SimplifyQuery SQ = getBestSimplifyQuery(*this, F); 100 Optional<MemorySSAUpdater> MSSAU; 101 if (EnableMSSALoopDependency) { 102 // Not requiring MemorySSA and getting it only if available will split 103 // the loop pass pipeline when LoopRotate is being run first. 104 auto *MSSAA = getAnalysisIfAvailable<MemorySSAWrapperPass>(); 105 if (MSSAA) 106 MSSAU = MemorySSAUpdater(&MSSAA->getMSSA()); 107 } 108 return LoopRotation(L, LI, TTI, AC, &DT, &SE, 109 MSSAU.hasValue() ? MSSAU.getPointer() : nullptr, SQ, 110 false, MaxHeaderSize, false); 111 } 112 }; 113 } // end namespace 114 115 char LoopRotateLegacyPass::ID = 0; 116 INITIALIZE_PASS_BEGIN(LoopRotateLegacyPass, "loop-rotate", "Rotate Loops", 117 false, false) 118 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) 119 INITIALIZE_PASS_DEPENDENCY(LoopPass) 120 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) 121 INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass) 122 INITIALIZE_PASS_END(LoopRotateLegacyPass, "loop-rotate", "Rotate Loops", false, 123 false) 124 125 Pass *llvm::createLoopRotatePass(int MaxHeaderSize) { 126 return new LoopRotateLegacyPass(MaxHeaderSize); 127 } 128