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 DependenceInfo;
  28 class DominatorTree;
  29 class Loop;
  30 class LoopInfo;
  31 class MDNode;
  32 class OptimizationRemarkEmitter;
  33 class ScalarEvolution;
  34
  35 using NewLoopsMap = SmallDenseMap<const Loop *, Loop *, 4>;
  36
  37 /// @{
  38 /// Metadata attribute names
  39 const char *const LLVMLoopUnrollFollowupAll = "llvm.loop.unroll.followup_all";
  40 const char *const LLVMLoopUnrollFollowupUnrolled =
  41     "llvm.loop.unroll.followup_unrolled";
  42 const char *const LLVMLoopUnrollFollowupRemainder =
  43     "llvm.loop.unroll.followup_remainder";
  44 /// @}
  45
  46 const Loop* addClonedBlockToLoopInfo(BasicBlock *OriginalBB,
  47                                      BasicBlock *ClonedBB, LoopInfo *LI,
  48                                      NewLoopsMap &NewLoops);
  49
  50 /// Represents the result of a \c UnrollLoop invocation.
  51 enum class LoopUnrollResult {
  52   /// The loop was not modified.
  53   Unmodified,
  54
  55   /// The loop was partially unrolled -- we still have a loop, but with a
  56   /// smaller trip count.  We may also have emitted epilogue loop if the loop
  57   /// had a non-constant trip count.
  58   PartiallyUnrolled,
  59
  60   /// The loop was fully unrolled into straight-line code.  We no longer have
  61   /// any back-edges.
  62   FullyUnrolled
  63 };
  64
  65 LoopUnrollResult UnrollLoop(Loop *L, unsigned Count, unsigned TripCount,
  66                             bool Force, bool AllowRuntime,
  67                             bool AllowExpensiveTripCount, bool PreserveCondBr,
  68                             bool PreserveOnlyFirst, unsigned TripMultiple,
  69                             unsigned PeelCount, bool UnrollRemainder,
  70                             LoopInfo *LI, ScalarEvolution *SE,
  71                             DominatorTree *DT, AssumptionCache *AC,
  72                             OptimizationRemarkEmitter *ORE, bool PreserveLCSSA,
  73                             Loop **RemainderLoop = nullptr);
  74
  75 bool UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
  76                                 bool AllowExpensiveTripCount,
  77                                 bool UseEpilogRemainder, bool UnrollRemainder,
  78                                 LoopInfo *LI, ScalarEvolution *SE,
  79                                 DominatorTree *DT, AssumptionCache *AC,
  80                                 bool PreserveLCSSA,
  81                                 Loop **ResultLoop = nullptr);
  82
  83 void computePeelCount(Loop *L, unsigned LoopSize,
  84                       TargetTransformInfo::UnrollingPreferences &UP,
  85                       unsigned &TripCount, ScalarEvolution &SE);
  86
  87 bool canPeel(Loop *L);
  88
  89 bool peelLoop(Loop *L, unsigned PeelCount, LoopInfo *LI, ScalarEvolution *SE,
  90               DominatorTree *DT, AssumptionCache *AC, bool PreserveLCSSA);
  91
  92 LoopUnrollResult UnrollAndJamLoop(Loop *L, unsigned Count, unsigned TripCount,
  93                                   unsigned TripMultiple, bool UnrollRemainder,
  94                                   LoopInfo *LI, ScalarEvolution *SE,
  95                                   DominatorTree *DT, AssumptionCache *AC,
  96                                   OptimizationRemarkEmitter *ORE,
  97                                   Loop **EpilogueLoop = nullptr);
  98
  99 bool isSafeToUnrollAndJam(Loop *L, ScalarEvolution &SE, DominatorTree &DT,
 100                           DependenceInfo &DI);
 101
 102 bool computeUnrollCount(Loop *L, const TargetTransformInfo &TTI,
 103                         DominatorTree &DT, LoopInfo *LI, ScalarEvolution &SE,
 104                         const SmallPtrSetImpl<const Value *> &EphValues,
 105                         OptimizationRemarkEmitter *ORE, unsigned &TripCount,
 106                         unsigned MaxTripCount, unsigned &TripMultiple,
 107                         unsigned LoopSize,
 108                         TargetTransformInfo::UnrollingPreferences &UP,
 109                         bool &UseUpperBound);
 110
 111 BasicBlock *foldBlockIntoPredecessor(BasicBlock *BB, LoopInfo *LI,
 112                                      ScalarEvolution *SE, DominatorTree *DT);
 113
 114 void remapInstruction(Instruction *I, ValueToValueMapTy &VMap);
 115
 116 void simplifyLoopAfterUnroll(Loop *L, bool SimplifyIVs, LoopInfo *LI,
 117                              ScalarEvolution *SE, DominatorTree *DT,
 118                              AssumptionCache *AC);
 119
 120 MDNode *GetUnrollMetadata(MDNode *LoopID, StringRef Name);
 121
 122 TargetTransformInfo::UnrollingPreferences gatherUnrollingPreferences(
 123     Loop *L, ScalarEvolution &SE, const TargetTransformInfo &TTI, int OptLevel,
 124     Optional<unsigned> UserThreshold, Optional<unsigned> UserCount,
 125     Optional<bool> UserAllowPartial, Optional<bool> UserRuntime,
 126     Optional<bool> UserUpperBound, Optional<bool> UserAllowPeeling);
 127
 128 unsigned ApproximateLoopSize(const Loop *L, unsigned &NumCalls,
 129                              bool &NotDuplicatable, bool &Convergent,
 130                              const TargetTransformInfo &TTI,
 131                              const SmallPtrSetImpl<const Value *> &EphValues,
 132                              unsigned BEInsns);
 133
 134 } // end namespace llvm
 135
 136 #endif // LLVM_TRANSFORMS_UTILS_UNROLLLOOP_H