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/Analysis/AssumptionCache.h" 15 #include "llvm/Analysis/InstructionSimplify.h" 16 #include "llvm/Analysis/LazyBlockFrequencyInfo.h" 17 #include "llvm/Analysis/LoopInfo.h" 18 #include "llvm/Analysis/LoopPass.h" 19 #include "llvm/Analysis/MemorySSA.h" 20 #include "llvm/Analysis/MemorySSAUpdater.h" 21 #include "llvm/Analysis/ScalarEvolution.h" 22 #include "llvm/Analysis/TargetTransformInfo.h" 23 #include "llvm/InitializePasses.h" 24 #include "llvm/Support/CommandLine.h" 25 #include "llvm/Transforms/Scalar.h" 26 #include "llvm/Transforms/Utils/LoopRotationUtils.h" 27 #include "llvm/Transforms/Utils/LoopUtils.h" 28 #include <optional> 29 using namespace llvm; 30 31 #define DEBUG_TYPE "loop-rotate" 32 33 static cl::opt<unsigned> DefaultRotationThreshold( 34 "rotation-max-header-size", cl::init(16), cl::Hidden, 35 cl::desc("The default maximum header size for automatic loop rotation")); 36 37 static cl::opt<bool> PrepareForLTOOption( 38 "rotation-prepare-for-lto", cl::init(false), cl::Hidden, 39 cl::desc("Run loop-rotation in the prepare-for-lto stage. This option " 40 "should be used for testing only.")); 41 42 LoopRotatePass::LoopRotatePass(bool EnableHeaderDuplication, bool PrepareForLTO) 43 : EnableHeaderDuplication(EnableHeaderDuplication), 44 PrepareForLTO(PrepareForLTO) {} 45 46 void LoopRotatePass::printPipeline( 47 raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) { 48 static_cast<PassInfoMixin<LoopRotatePass> *>(this)->printPipeline( 49 OS, MapClassName2PassName); 50 OS << "<"; 51 if (!EnableHeaderDuplication) 52 OS << "no-"; 53 OS << "header-duplication;"; 54 55 if (!PrepareForLTO) 56 OS << "no-"; 57 OS << "prepare-for-lto"; 58 OS << ">"; 59 } 60 61 PreservedAnalyses LoopRotatePass::run(Loop &L, LoopAnalysisManager &AM, 62 LoopStandardAnalysisResults &AR, 63 LPMUpdater &) { 64 // Vectorization requires loop-rotation. Use default threshold for loops the 65 // user explicitly marked for vectorization, even when header duplication is 66 // disabled. 67 int Threshold = 68 (EnableHeaderDuplication && !L.getHeader()->getParent()->hasMinSize()) || 69 hasVectorizeTransformation(&L) == TM_ForcedByUser 70 ? DefaultRotationThreshold 71 : 0; 72 const DataLayout &DL = L.getHeader()->getDataLayout(); 73 const SimplifyQuery SQ = getBestSimplifyQuery(AR, DL); 74 75 std::optional<MemorySSAUpdater> MSSAU; 76 if (AR.MSSA) 77 MSSAU = MemorySSAUpdater(AR.MSSA); 78 bool Changed = LoopRotation(&L, &AR.LI, &AR.TTI, &AR.AC, &AR.DT, &AR.SE, 79 MSSAU ? &*MSSAU : nullptr, SQ, false, Threshold, 80 false, PrepareForLTO || PrepareForLTOOption); 81 82 if (!Changed) 83 return PreservedAnalyses::all(); 84 85 if (AR.MSSA && VerifyMemorySSA) 86 AR.MSSA->verifyMemorySSA(); 87 88 auto PA = getLoopPassPreservedAnalyses(); 89 if (AR.MSSA) 90 PA.preserve<MemorySSAAnalysis>(); 91 return PA; 92 } 93