lib/Transforms/Scalar/LoopRotation.cpp

   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/Support/Debug.h"
  22 #include "llvm/Transforms/Scalar.h"
  23 #include "llvm/Transforms/Scalar/LoopPassManager.h"
  24 #include "llvm/Transforms/Utils/LoopRotationUtils.h"
  25 #include "llvm/Transforms/Utils/LoopUtils.h"
  26 using namespace llvm;
  27
  28 #define DEBUG_TYPE "loop-rotate"
  29
  30 static cl::opt<unsigned> DefaultRotationThreshold(
  31     "rotation-max-header-size", cl::init(16), cl::Hidden,
  32     cl::desc("The default maximum header size for automatic loop rotation"));
  33
  34 LoopRotatePass::LoopRotatePass(bool EnableHeaderDuplication)
  35     : EnableHeaderDuplication(EnableHeaderDuplication) {}
  36
  37 PreservedAnalyses LoopRotatePass::run(Loop &L, LoopAnalysisManager &AM,
  38                                       LoopStandardAnalysisResults &AR,
  39                                       LPMUpdater &) {
  40   int Threshold = EnableHeaderDuplication ? DefaultRotationThreshold : 0;
  41   const DataLayout &DL = L.getHeader()->getModule()->getDataLayout();
  42   const SimplifyQuery SQ = getBestSimplifyQuery(AR, DL);
  43
  44   Optional<MemorySSAUpdater> MSSAU;
  45   if (AR.MSSA)
  46     MSSAU = MemorySSAUpdater(AR.MSSA);
  47   bool Changed = LoopRotation(&L, &AR.LI, &AR.TTI, &AR.AC, &AR.DT, &AR.SE,
  48                               MSSAU.hasValue() ? MSSAU.getPointer() : nullptr,
  49                               SQ, false, Threshold, false);
  50
  51   if (!Changed)
  52     return PreservedAnalyses::all();
  53
  54   if (AR.MSSA && VerifyMemorySSA)
  55     AR.MSSA->verifyMemorySSA();
  56
  57   return getLoopPassPreservedAnalyses();
  58 }
  59
  60 namespace {
  61
  62 class LoopRotateLegacyPass : public LoopPass {
  63   unsigned MaxHeaderSize;
  64
  65 public:
  66   static char ID; // Pass ID, replacement for typeid
  67   LoopRotateLegacyPass(int SpecifiedMaxHeaderSize = -1) : LoopPass(ID) {
  68     initializeLoopRotateLegacyPassPass(*PassRegistry::getPassRegistry());
  69     if (SpecifiedMaxHeaderSize == -1)
  70       MaxHeaderSize = DefaultRotationThreshold;
  71     else
  72       MaxHeaderSize = unsigned(SpecifiedMaxHeaderSize);
  73   }
  74
  75   // LCSSA form makes instruction renaming easier.
  76   void getAnalysisUsage(AnalysisUsage &AU) const override {
  77     AU.addRequired<AssumptionCacheTracker>();
  78     AU.addRequired<TargetTransformInfoWrapperPass>();
  79     if (EnableMSSALoopDependency) {
  80       AU.addRequired<MemorySSAWrapperPass>();
  81       AU.addPreserved<MemorySSAWrapperPass>();
  82     }
  83     getLoopAnalysisUsage(AU);
  84   }
  85
  86   bool runOnLoop(Loop *L, LPPassManager &LPM) override {
  87     if (skipLoop(L))
  88       return false;
  89     Function &F = *L->getHeader()->getParent();
  90
  91     auto *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
  92     const auto *TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
  93     auto *AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
  94     auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
  95     auto *DT = DTWP ? &DTWP->getDomTree() : nullptr;
  96     auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>();
  97     auto *SE = SEWP ? &SEWP->getSE() : nullptr;
  98     const SimplifyQuery SQ = getBestSimplifyQuery(*this, F);
  99     Optional<MemorySSAUpdater> MSSAU;
 100     if (EnableMSSALoopDependency) {
 101       MemorySSA *MSSA = &getAnalysis<MemorySSAWrapperPass>().getMSSA();
 102       MSSAU = MemorySSAUpdater(MSSA);
 103     }
 104     return LoopRotation(L, LI, TTI, AC, DT, SE,
 105                         MSSAU.hasValue() ? MSSAU.getPointer() : nullptr, SQ,
 106                         false, MaxHeaderSize, false);
 107   }
 108 };
 109 }
 110
 111 char LoopRotateLegacyPass::ID = 0;
 112 INITIALIZE_PASS_BEGIN(LoopRotateLegacyPass, "loop-rotate", "Rotate Loops",
 113                       false, false)
 114 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
 115 INITIALIZE_PASS_DEPENDENCY(LoopPass)
 116 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
 117 INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)
 118 INITIALIZE_PASS_END(LoopRotateLegacyPass, "loop-rotate", "Rotate Loops", false,
 119                     false)
 120
 121 Pass *llvm::createLoopRotatePass(int MaxHeaderSize) {
 122   return new LoopRotateLegacyPass(MaxHeaderSize);
 123 }