VPlanTransforms.h

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//===- VPlanTransforms.h - Utility VPlan to VPlan transforms --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file provides utility VPlan to VPlan transformations.
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_TRANSFORMS_VECTORIZE_VPLANTRANSFORMS_H
#define LLVM_TRANSFORMS_VECTORIZE_VPLANTRANSFORMS_H
 
#include "VPlan.h"
#include "llvm/ADT/STLFunctionalExtras.h"
 
namespace llvm {
 
class InductionDescriptor;
class Instruction;
class PHINode;
class ScalarEvolution;
class PredicatedScalarEvolution;
class TargetLibraryInfo;
class VPBuilder;
class VPRecipeBuilder;
 
struct VPlanTransforms {
  /// Replaces the VPInstructions in \p Plan with corresponding
  /// widen recipes.
  static void
  VPInstructionsToVPRecipes(VPlanPtr &Plan,
                            function_ref<const InductionDescriptor *(PHINode *)>
                                GetIntOrFpInductionDescriptor,
                            ScalarEvolution &SE, const TargetLibraryInfo &TLI);
 
  /// Try to have all users of fixed-order recurrences appear after the recipe
  /// defining their previous value, by either sinking users or hoisting recipes
  /// defining their previous value (and its operands). Then introduce
  /// FirstOrderRecurrenceSplice VPInstructions to combine the value from the
  /// recurrence phis and previous values.
  /// \returns true if all users of fixed-order recurrences could be re-arranged
  /// as needed or false if it is not possible. In the latter case, \p Plan is
  /// not valid.
  static bool adjustFixedOrderRecurrences(VPlan &Plan, VPBuilder &Builder);
 
  /// Clear NSW/NUW flags from reduction instructions if necessary.
  static void clearReductionWrapFlags(VPlan &Plan);
 
  /// Explicitly unroll \p Plan by \p UF.
  static void unrollByUF(VPlan &Plan, unsigned UF, LLVMContext &Ctx);
 
  /// Optimize \p Plan based on \p BestVF and \p BestUF. This may restrict the
  /// resulting plan to \p BestVF and \p BestUF.
  static void optimizeForVFAndUF(VPlan &Plan, ElementCount BestVF,
                                 unsigned BestUF,
                                 PredicatedScalarEvolution &PSE);
 
  /// Apply VPlan-to-VPlan optimizations to \p Plan, including induction recipe
  /// optimizations, dead recipe removal, replicate region optimizations and
  /// block merging.
  static void optimize(VPlan &Plan);
 
  /// Wrap predicated VPReplicateRecipes with a mask operand in an if-then
  /// region block and remove the mask operand. Optimize the created regions by
  /// iteratively sinking scalar operands into the region, followed by merging
  /// regions until no improvements are remaining.
  static void createAndOptimizeReplicateRegions(VPlan &Plan);
 
  /// Replace (ICMP_ULE, wide canonical IV, backedge-taken-count) checks with an
  /// (active-lane-mask recipe, wide canonical IV, trip-count). If \p
  /// UseActiveLaneMaskForControlFlow is true, introduce an
  /// VPActiveLaneMaskPHIRecipe. If \p DataAndControlFlowWithoutRuntimeCheck is
  /// true, no minimum-iteration runtime check will be created (during skeleton
  /// creation) and instead it is handled using active-lane-mask. \p
  /// DataAndControlFlowWithoutRuntimeCheck implies \p
  /// UseActiveLaneMaskForControlFlow.
  static void addActiveLaneMask(VPlan &Plan,
                                bool UseActiveLaneMaskForControlFlow,
                                bool DataAndControlFlowWithoutRuntimeCheck);
 
  /// Insert truncates and extends for any truncated recipe. Redundant casts
  /// will be folded later.
  static void
  truncateToMinimalBitwidths(VPlan &Plan,
                             const MapVector<Instruction *, uint64_t> &MinBWs);
 
  /// Drop poison flags from recipes that may generate a poison value that is
  /// used after vectorization, even when their operands are not poison. Those
  /// recipes meet the following conditions:
  ///  * Contribute to the address computation of a recipe generating a widen
  ///    memory load/store (VPWidenMemoryInstructionRecipe or
  ///    VPInterleaveRecipe).
  ///  * Such a widen memory load/store has at least one underlying Instruction
  ///    that is in a basic block that needs predication and after vectorization
  ///    the generated instruction won't be predicated.
  /// Uses \p BlockNeedsPredication to check if a block needs predicating.
  /// TODO: Replace BlockNeedsPredication callback with retrieving info from
  ///       VPlan directly.
  static void dropPoisonGeneratingRecipes(
      VPlan &Plan, function_ref<bool(BasicBlock *)> BlockNeedsPredication);
 
  /// Add a VPEVLBasedIVPHIRecipe and related recipes to \p Plan and
  /// replaces all uses except the canonical IV increment of
  /// VPCanonicalIVPHIRecipe with a VPEVLBasedIVPHIRecipe.
  /// VPCanonicalIVPHIRecipe is only used to control the loop after
  /// this transformation.
  /// \returns true if the transformation succeeds, or false if it doesn't.
  static bool
  tryAddExplicitVectorLength(VPlan &Plan,
                             const std::optional<unsigned> &MaxEVLSafeElements);
 
  // For each Interleave Group in \p InterleaveGroups replace the Recipes
  // widening its memory instructions with a single VPInterleaveRecipe at its
  // insertion point.
  static void createInterleaveGroups(
      VPlan &Plan,
      const SmallPtrSetImpl<const InterleaveGroup<Instruction> *>
          &InterleaveGroups,
      VPRecipeBuilder &RecipeBuilder, bool ScalarEpilogueAllowed);
 
  /// Remove dead recipes from \p Plan.
  static void removeDeadRecipes(VPlan &Plan);
 
  /// Update \p Plan to account for the uncountable early exit block in \p
  /// UncountableExitingBlock by
  ///  * updating the condition exiting the vector loop to include the early
  ///    exit conditions
  ///  * splitting the original middle block to branch to the early exit block
  ///    if taken.
  static void handleUncountableEarlyExit(VPlan &Plan, ScalarEvolution &SE,
                                         Loop *OrigLoop,
                                         BasicBlock *UncountableExitingBlock,
                                         VPRecipeBuilder &RecipeBuilder);
 
  /// Lower abstract recipes to concrete ones, that can be codegen'd.
  static void convertToConcreteRecipes(VPlan &Plan);
};
 
} // namespace llvm
 
#endif // LLVM_TRANSFORMS_VECTORIZE_VPLANTRANSFORMS_H