include/llvm/Transforms/Utils/UnrollLoop.h

   1 //===- llvm/Transforms/Utils/UnrollLoop.h - Unrolling utilities -*- C++ -*-===//
   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 defines some loop unrolling utilities. It does not define any
  10 // actual pass or policy, but provides a single function to perform loop
  11 // unrolling.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #ifndef LLVM_TRANSFORMS_UTILS_UNROLLLOOP_H
  16 #define LLVM_TRANSFORMS_UTILS_UNROLLLOOP_H
  17
  18 #include "llvm/ADT/DenseMap.h"
  19 #include "llvm/ADT/StringRef.h"
  20 #include "llvm/Analysis/TargetTransformInfo.h"
  21 #include "llvm/Transforms/Utils/ValueMapper.h"
  22
  23 namespace llvm {
  24
  25 class AssumptionCache;
  26 class BasicBlock;
  27 class BlockFrequencyInfo;
  28 class DependenceInfo;
  29 class DominatorTree;
  30 class Loop;
  31 class LoopInfo;
  32 class MDNode;
  33 class ProfileSummaryInfo;
  34 class OptimizationRemarkEmitter;
  35 class ScalarEvolution;
  36
  37 using NewLoopsMap = SmallDenseMap<const Loop *, Loop *, 4>;
  38
  39 /// @{
  40 /// Metadata attribute names
  41 const char *const LLVMLoopUnrollFollowupAll = "llvm.loop.unroll.followup_all";
  42 const char *const LLVMLoopUnrollFollowupUnrolled =
  43     "llvm.loop.unroll.followup_unrolled";
  44 const char *const LLVMLoopUnrollFollowupRemainder =
  45     "llvm.loop.unroll.followup_remainder";
  46 /// @}
  47
  48 const Loop* addClonedBlockToLoopInfo(BasicBlock *OriginalBB,
  49                                      BasicBlock *ClonedBB, LoopInfo *LI,
  50                                      NewLoopsMap &NewLoops);
  51
  52 /// Represents the result of a \c UnrollLoop invocation.
  53 enum class LoopUnrollResult {
  54   /// The loop was not modified.
  55   Unmodified,
  56
  57   /// The loop was partially unrolled -- we still have a loop, but with a
  58   /// smaller trip count.  We may also have emitted epilogue loop if the loop
  59   /// had a non-constant trip count.
  60   PartiallyUnrolled,
  61
  62   /// The loop was fully unrolled into straight-line code.  We no longer have
  63   /// any back-edges.
  64   FullyUnrolled
  65 };
  66
  67 struct UnrollLoopOptions {
  68   unsigned Count;
  69   unsigned TripCount;
  70   bool Force;
  71   bool AllowRuntime;
  72   bool AllowExpensiveTripCount;
  73   bool PreserveCondBr;
  74   bool PreserveOnlyFirst;
  75   unsigned TripMultiple;
  76   unsigned PeelCount;
  77   bool UnrollRemainder;
  78   bool ForgetAllSCEV;
  79 };
  80
  81 LoopUnrollResult UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
  82                             ScalarEvolution *SE, DominatorTree *DT,
  83                             AssumptionCache *AC, OptimizationRemarkEmitter *ORE,
  84                             bool PreserveLCSSA, Loop **RemainderLoop = nullptr);
  85
  86 bool UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
  87                                 bool AllowExpensiveTripCount,
  88                                 bool UseEpilogRemainder, bool UnrollRemainder,
  89                                 bool ForgetAllSCEV, LoopInfo *LI,
  90                                 ScalarEvolution *SE, DominatorTree *DT,
  91                                 AssumptionCache *AC, bool PreserveLCSSA,
  92                                 Loop **ResultLoop = nullptr);
  93
  94 void computePeelCount(Loop *L, unsigned LoopSize,
  95                       TargetTransformInfo::UnrollingPreferences &UP,
  96                       unsigned &TripCount, ScalarEvolution &SE);
  97
  98 bool canPeel(Loop *L);
  99
 100 bool peelLoop(Loop *L, unsigned PeelCount, LoopInfo *LI, ScalarEvolution *SE,
 101               DominatorTree *DT, AssumptionCache *AC, bool PreserveLCSSA);
 102
 103 LoopUnrollResult UnrollAndJamLoop(Loop *L, unsigned Count, unsigned TripCount,
 104                                   unsigned TripMultiple, bool UnrollRemainder,
 105                                   LoopInfo *LI, ScalarEvolution *SE,
 106                                   DominatorTree *DT, AssumptionCache *AC,
 107                                   OptimizationRemarkEmitter *ORE,
 108                                   Loop **EpilogueLoop = nullptr);
 109
 110 bool isSafeToUnrollAndJam(Loop *L, ScalarEvolution &SE, DominatorTree &DT,
 111                           DependenceInfo &DI);
 112
 113 bool computeUnrollCount(Loop *L, const TargetTransformInfo &TTI,
 114                         DominatorTree &DT, LoopInfo *LI, ScalarEvolution &SE,
 115                         const SmallPtrSetImpl<const Value *> &EphValues,
 116                         OptimizationRemarkEmitter *ORE, unsigned &TripCount,
 117                         unsigned MaxTripCount, bool MaxOrZero,
 118                         unsigned &TripMultiple, unsigned LoopSize,
 119                         TargetTransformInfo::UnrollingPreferences &UP,
 120                         bool &UseUpperBound);
 121
 122 void remapInstruction(Instruction *I, ValueToValueMapTy &VMap);
 123
 124 void simplifyLoopAfterUnroll(Loop *L, bool SimplifyIVs, LoopInfo *LI,
 125                              ScalarEvolution *SE, DominatorTree *DT,
 126                              AssumptionCache *AC);
 127
 128 MDNode *GetUnrollMetadata(MDNode *LoopID, StringRef Name);
 129
 130 TargetTransformInfo::UnrollingPreferences gatherUnrollingPreferences(
 131     Loop *L, ScalarEvolution &SE, const TargetTransformInfo &TTI,
 132     BlockFrequencyInfo *BFI, ProfileSummaryInfo *PSI, int OptLevel,
 133     Optional<unsigned> UserThreshold, Optional<unsigned> UserCount,
 134     Optional<bool> UserAllowPartial, Optional<bool> UserRuntime,
 135     Optional<bool> UserUpperBound, Optional<bool> UserAllowPeeling,
 136     Optional<bool> UserAllowProfileBasedPeeling,
 137     Optional<unsigned> UserFullUnrollMaxCount);
 138
 139 unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls,
 140                              bool &NotDuplicatable, bool &Convergent,
 141                              const TargetTransformInfo &TTI,
 142                              const SmallPtrSetImpl<const Value *> &EphValues,
 143                              unsigned BEInsns);
 144
 145 } // end namespace llvm
 146
 147 #endif // LLVM_TRANSFORMS_UTILS_UNROLLLOOP_H