llvm/lib/Transforms/Vectorize/VPlanTransforms.h

   1 //===- VPlanTransforms.h - Utility VPlan to VPlan transforms --------------===//
   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 /// \file
  10 /// This file provides utility VPlan to VPlan transformations.
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_TRANSFORMS_VECTORIZE_VPLANTRANSFORMS_H
  14 #define LLVM_TRANSFORMS_VECTORIZE_VPLANTRANSFORMS_H
  15
  16 #include "VPlan.h"
  17 #include "llvm/ADT/STLFunctionalExtras.h"
  18
  19 namespace llvm {
  20
  21 class InductionDescriptor;
  22 class Instruction;
  23 class PHINode;
  24 class ScalarEvolution;
  25 class Loop;
  26 class PredicatedScalarEvolution;
  27 class TargetLibraryInfo;
  28 class VPBuilder;
  29 class VPRecipeBuilder;
  30
  31 struct VPlanTransforms {
  32   /// Replaces the VPInstructions in \p Plan with corresponding
  33   /// widen recipes.
  34   static void
  35   VPInstructionsToVPRecipes(VPlanPtr &Plan,
  36                             function_ref<const InductionDescriptor *(PHINode *)>
  37                                 GetIntOrFpInductionDescriptor,
  38                             ScalarEvolution &SE, const TargetLibraryInfo &TLI);
  39
  40   /// Sink users of fixed-order recurrences after the recipe defining their
  41   /// previous value. Then introduce FirstOrderRecurrenceSplice VPInstructions
  42   /// to combine the value from the recurrence phis and previous values. The
  43   /// current implementation assumes all users can be sunk after the previous
  44   /// value, which is enforced by earlier legality checks.
  45   /// \returns true if all users of fixed-order recurrences could be re-arranged
  46   /// as needed or false if it is not possible. In the latter case, \p Plan is
  47   /// not valid.
  48   static bool adjustFixedOrderRecurrences(VPlan &Plan, VPBuilder &Builder);
  49
  50   /// Clear NSW/NUW flags from reduction instructions if necessary.
  51   static void clearReductionWrapFlags(VPlan &Plan);
  52
  53   /// Optimize \p Plan based on \p BestVF and \p BestUF. This may restrict the
  54   /// resulting plan to \p BestVF and \p BestUF.
  55   static void optimizeForVFAndUF(VPlan &Plan, ElementCount BestVF,
  56                                  unsigned BestUF,
  57                                  PredicatedScalarEvolution &PSE);
  58
  59   /// Apply VPlan-to-VPlan optimizations to \p Plan, including induction recipe
  60   /// optimizations, dead recipe removal, replicate region optimizations and
  61   /// block merging.
  62   static void optimize(VPlan &Plan, ScalarEvolution &SE);
  63
  64   /// Wrap predicated VPReplicateRecipes with a mask operand in an if-then
  65   /// region block and remove the mask operand. Optimize the created regions by
  66   /// iteratively sinking scalar operands into the region, followed by merging
  67   /// regions until no improvements are remaining.
  68   static void createAndOptimizeReplicateRegions(VPlan &Plan);
  69
  70   /// Replace (ICMP_ULE, wide canonical IV, backedge-taken-count) checks with an
  71   /// (active-lane-mask recipe, wide canonical IV, trip-count). If \p
  72   /// UseActiveLaneMaskForControlFlow is true, introduce an
  73   /// VPActiveLaneMaskPHIRecipe. If \p DataAndControlFlowWithoutRuntimeCheck is
  74   /// true, no minimum-iteration runtime check will be created (during skeleton
  75   /// creation) and instead it is handled using active-lane-mask. \p
  76   /// DataAndControlFlowWithoutRuntimeCheck implies \p
  77   /// UseActiveLaneMaskForControlFlow.
  78   static void addActiveLaneMask(VPlan &Plan,
  79                                 bool UseActiveLaneMaskForControlFlow,
  80                                 bool DataAndControlFlowWithoutRuntimeCheck);
  81
  82 private:
  83   /// Remove redundant VPBasicBlocks by merging them into their predecessor if
  84   /// the predecessor has a single successor.
  85   static bool mergeBlocksIntoPredecessors(VPlan &Plan);
  86
  87   /// Remove redundant casts of inductions.
  88   ///
  89   /// Such redundant casts are casts of induction variables that can be ignored,
  90   /// because we already proved that the casted phi is equal to the uncasted phi
  91   /// in the vectorized loop. There is no need to vectorize the cast - the same
  92   /// value can be used for both the phi and casts in the vector loop.
  93   static void removeRedundantInductionCasts(VPlan &Plan);
  94
  95   /// Try to replace VPWidenCanonicalIVRecipes with a widened canonical IV
  96   /// recipe, if it exists.
  97   static void removeRedundantCanonicalIVs(VPlan &Plan);
  98
  99   static void removeDeadRecipes(VPlan &Plan);
 100
 101   /// If any user of a VPWidenIntOrFpInductionRecipe needs scalar values,
 102   /// provide them by building scalar steps off of the canonical scalar IV and
 103   /// update the original IV's users. This is an optional optimization to reduce
 104   /// the needs of vector extracts.
 105   static void optimizeInductions(VPlan &Plan, ScalarEvolution &SE);
 106
 107   /// Remove redundant EpxandSCEVRecipes in \p Plan's entry block by replacing
 108   /// them with already existing recipes expanding the same SCEV expression.
 109   static void removeRedundantExpandSCEVRecipes(VPlan &Plan);
 110
 111 };
 112
 113 } // namespace llvm
 114
 115 #endif // LLVM_TRANSFORMS_VECTORIZE_VPLANTRANSFORMS_H