llvm/lib/Transforms/Vectorize/VPlanUtils.h

//===- VPlanUtils.h - VPlan-related utilities -------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TRANSFORMS_VECTORIZE_VPLANUTILS_H
#define LLVM_TRANSFORMS_VECTORIZE_VPLANUTILS_H

#include "VPlan.h"
#include "VPlanPatternMatch.h"
#include "llvm/Support/Compiler.h"

namespace llvm {
class MemoryLocation;
class ScalarEvolution;
class SCEV;
class PredicatedScalarEvolution;
} // namespace llvm

namespace llvm {

namespace vputils {
/// Returns true if only the first lane of \p Def is used.
bool onlyFirstLaneUsed(const VPValue *Def);

/// Returns true if only the first part of \p Def is used.
bool onlyFirstPartUsed(const VPValue *Def);

/// Returns true if only scalar values of \p Def are used by all users.
bool onlyScalarValuesUsed(const VPValue *Def);

/// Get or create a VPValue that corresponds to the expansion of \p Expr. If \p
/// Expr is a SCEVConstant or SCEVUnknown, return a VPValue wrapping the live-in
/// value. Otherwise return a VPExpandSCEVRecipe to expand \p Expr. If \p Plan's
/// pre-header already contains a recipe expanding \p Expr, return it. If not,
/// create a new one.
VPValue *getOrCreateVPValueForSCEVExpr(VPlan &Plan, const SCEV *Expr);

/// Return the SCEV expression for \p V. Returns SCEVCouldNotCompute if no
/// SCEV expression could be constructed.
const SCEV *getSCEVExprForVPValue(const VPValue *V,
                                  PredicatedScalarEvolution &PSE,
                                  const Loop *L = nullptr);

/// Returns true if \p Addr is an address SCEV that can be passed to
/// TTI::getAddressComputationCost, i.e. the address SCEV is loop invariant, an
/// affine AddRec (i.e. induction ), or an add expression of such operands or a
/// sign-extended AddRec.
bool isAddressSCEVForCost(const SCEV *Addr, ScalarEvolution &SE, const Loop *L);

/// Returns true if \p VPV is a single scalar, either because it produces the
/// same value for all lanes or only has its first lane used.
bool isSingleScalar(const VPValue *VPV);

/// Return true if \p V is a header mask in \p Plan.
bool isHeaderMask(const VPValue *V, const VPlan &Plan);

/// Checks if \p V is uniform across all VF lanes and UF parts. It is considered
/// as such if it is either loop invariant (defined outside the vector region)
/// or its operands are known to be uniform across all VFs and UFs (e.g.
/// VPDerivedIV or the canonical IV).
bool isUniformAcrossVFsAndUFs(const VPValue *V);

/// Returns the header block of the first, top-level loop, or null if none
/// exist.
VPBasicBlock *getFirstLoopHeader(VPlan &Plan, VPDominatorTree &VPDT);

/// Get the VF scaling factor applied to the recipe's output, if the recipe has
/// one.
unsigned getVFScaleFactor(VPRecipeBase *R);

/// Return true if we do not know how to (mechanically) hoist or sink \p R.
/// When sinking, passing \p Sinking = true ensures that assumes aren't sunk.
bool cannotHoistOrSinkRecipe(const VPRecipeBase &R, bool Sinking = false);

/// Returns the VPValue representing the uncountable exit comparison used by
/// AnyOf if the recipes it depends on can be traced back to live-ins and
/// the addresses (in GEP/PtrAdd form) of any (non-masked) load used in
/// generating the values for the comparison. The recipes are stored in
/// \p Recipes, and recipes forming an address for a load are also added to
/// \p GEPs.
LLVM_ABI_FOR_TEST
std::optional<VPValue *>
getRecipesForUncountableExit(SmallVectorImpl<VPInstruction *> &Recipes,
                             SmallVectorImpl<VPInstruction *> &GEPs,
                             VPBasicBlock *LatchVPBB);

/// Return a MemoryLocation for \p R with noalias metadata populated from
/// \p R, if the recipe is supported and std::nullopt otherwise. The pointer of
/// the location is conservatively set to nullptr.
std::optional<MemoryLocation> getMemoryLocation(const VPRecipeBase &R);

/// Extracts and returns NoWrap and FastMath flags from the induction binop in
/// \p ID.
inline VPIRFlags getFlagsFromIndDesc(const InductionDescriptor &ID) {
  if (ID.getKind() == InductionDescriptor::IK_FpInduction)
    return ID.getInductionBinOp()->getFastMathFlags();

  if (auto *OBO = dyn_cast_if_present<OverflowingBinaryOperator>(
          ID.getInductionBinOp()))
    return VPIRFlags::WrapFlagsTy(OBO->hasNoUnsignedWrap(),
                                  OBO->hasNoSignedWrap());

  assert(ID.getKind() == InductionDescriptor::IK_IntInduction &&
         "Expected int induction");
  return VPIRFlags::WrapFlagsTy(false, false);
}

/// Search \p Start's users for a recipe satisfying \p Pred, looking through
/// recipes with definitions.
template <typename PredT>
inline VPRecipeBase *findRecipe(VPValue *Start, PredT Pred) {
  SetVector<VPValue *> Worklist;
  Worklist.insert(Start);
  for (unsigned I = 0; I != Worklist.size(); ++I) {
    VPValue *Cur = Worklist[I];
    auto *R = Cur->getDefiningRecipe();
    if (!R)
      continue;
    if (Pred(R))
      return R;
    for (VPUser *U : Cur->users()) {
      for (VPValue *V : cast<VPRecipeBase>(U)->definedValues())
        Worklist.insert(V);
    }
  }
  return nullptr;
}

/// If \p V is used by a recipe matching pattern \p P, return it. Otherwise
/// return nullptr;
template <typename MatchT>
static VPRecipeBase *findUserOf(VPValue *V, const MatchT &P) {
  using namespace llvm::VPlanPatternMatch;
  auto It = find_if(V->users(), match_fn(P));
  return It == V->user_end() ? nullptr : cast<VPRecipeBase>(*It);
}

/// If \p V is used by a VPInstruction with \p Opcode, return it. Otherwise
/// return nullptr.
template <unsigned Opcode> static VPInstruction *findUserOf(VPValue *V) {
  using namespace llvm::VPlanPatternMatch;
  return cast_or_null<VPInstruction>(findUserOf(V, m_VPInstruction<Opcode>()));
}

template <typename RecipeTy> static RecipeTy *findUserOf(VPValue *V) {
  using namespace llvm::VPlanPatternMatch;
  return cast_or_null<RecipeTy>(findUserOf(V, m_Isa<RecipeTy>()));
}

/// Find the canonical IV increment of \p Plan's vector loop region. Returns
/// nullptr if not found.
VPInstruction *findCanonicalIVIncrement(VPlan &Plan);

/// Returns the GEP nowrap flags for \p Ptr, looking through pointer casts
/// mirroring Value::stripPointerCasts.
GEPNoWrapFlags getGEPFlagsForPtr(VPValue *Ptr);

/// Find the ComputeReductionResult recipe for \p PhiR, looking through selects
/// inserted for predicated reductions or tail folding.
VPInstruction *findComputeReductionResult(VPReductionPHIRecipe *PhiR);

/// Collect the header mask with the pattern:
/// (ICMP_ULE, WideCanonicalIV, backedge-taken-count)
/// TODO: Introduce explicit recipe for header-mask instead of searching
/// the header-mask pattern manually.
VPSingleDefRecipe *findHeaderMask(VPlan &Plan);

} // namespace vputils

//===----------------------------------------------------------------------===//
// Utilities for modifying predecessors and successors of VPlan blocks.
//===----------------------------------------------------------------------===//

/// Class that provides utilities for VPBlockBases in VPlan.
class VPBlockUtils {
public:
  VPBlockUtils() = delete;

  /// Insert disconnected VPBlockBase \p NewBlock after \p BlockPtr. Add \p
  /// NewBlock as successor of \p BlockPtr and \p BlockPtr as predecessor of \p
  /// NewBlock, and propagate \p BlockPtr parent to \p NewBlock. \p BlockPtr's
  /// successors are moved from \p BlockPtr to \p NewBlock. \p NewBlock must
  /// have neither successors nor predecessors.
  static void insertBlockAfter(VPBlockBase *NewBlock, VPBlockBase *BlockPtr) {
    assert(!NewBlock->hasSuccessors() && !NewBlock->hasPredecessors() &&
           "Can't insert new block with predecessors or successors.");
    NewBlock->setParent(BlockPtr->getParent());
    transferSuccessors(BlockPtr, NewBlock);
    connectBlocks(BlockPtr, NewBlock);
  }

  /// Insert disconnected block \p NewBlock before \p Blockptr. First
  /// disconnects all predecessors of \p BlockPtr and connects them to \p
  /// NewBlock. Add \p NewBlock as predecessor of \p BlockPtr and \p BlockPtr as
  /// successor of \p NewBlock.
  static void insertBlockBefore(VPBlockBase *NewBlock, VPBlockBase *BlockPtr) {
    assert(!NewBlock->hasSuccessors() && !NewBlock->hasPredecessors() &&
           "Can't insert new block with predecessors or successors.");
    NewBlock->setParent(BlockPtr->getParent());
    for (VPBlockBase *Pred : to_vector(BlockPtr->predecessors())) {
      Pred->replaceSuccessor(BlockPtr, NewBlock);
      NewBlock->appendPredecessor(Pred);
    }
    BlockPtr->clearPredecessors();
    connectBlocks(NewBlock, BlockPtr);
  }

  /// Insert disconnected VPBlockBases \p IfTrue and \p IfFalse after \p
  /// BlockPtr. Add \p IfTrue and \p IfFalse as succesors of \p BlockPtr and \p
  /// BlockPtr as predecessor of \p IfTrue and \p IfFalse. Propagate \p BlockPtr
  /// parent to \p IfTrue and \p IfFalse. \p BlockPtr must have no successors
  /// and \p IfTrue and \p IfFalse must have neither successors nor
  /// predecessors.
  static void insertTwoBlocksAfter(VPBlockBase *IfTrue, VPBlockBase *IfFalse,
                                   VPBlockBase *BlockPtr) {
    assert(!IfTrue->hasSuccessors() && "Can't insert IfTrue with successors.");
    assert(!IfFalse->hasSuccessors() &&
           "Can't insert IfFalse with successors.");
    BlockPtr->setTwoSuccessors(IfTrue, IfFalse);
    IfTrue->setPredecessors({BlockPtr});
    IfFalse->setPredecessors({BlockPtr});
    IfTrue->setParent(BlockPtr->getParent());
    IfFalse->setParent(BlockPtr->getParent());
  }

  /// Connect VPBlockBases \p From and \p To bi-directionally. If \p PredIdx is
  /// -1, append \p From to the predecessors of \p To, otherwise set \p To's
  /// predecessor at \p PredIdx to \p From. If \p SuccIdx is -1, append \p To to
  /// the successors of \p From, otherwise set \p From's successor at \p SuccIdx
  /// to \p To. Both VPBlockBases must have the same parent, which can be null.
  /// Both VPBlockBases can be already connected to other VPBlockBases.
  static void connectBlocks(VPBlockBase *From, VPBlockBase *To,
                            unsigned PredIdx = -1u, unsigned SuccIdx = -1u) {
    assert((From->getParent() == To->getParent()) &&
           "Can't connect two block with different parents");

    if (SuccIdx == -1u)
      From->appendSuccessor(To);
    else
      From->getSuccessors()[SuccIdx] = To;

    if (PredIdx == -1u)
      To->appendPredecessor(From);
    else
      To->getPredecessors()[PredIdx] = From;
  }

  /// Disconnect VPBlockBases \p From and \p To bi-directionally. Remove \p To
  /// from the successors of \p From and \p From from the predecessors of \p To.
  static void disconnectBlocks(VPBlockBase *From, VPBlockBase *To) {
    assert(To && "Successor to disconnect is null.");
    From->removeSuccessor(To);
    To->removePredecessor(From);
  }

  /// Reassociate all the blocks connected to \p Old so that they now point to
  /// \p New.
  static void reassociateBlocks(VPBlockBase *Old, VPBlockBase *New) {
    for (auto *Pred : to_vector(Old->getPredecessors()))
      Pred->replaceSuccessor(Old, New);
    for (auto *Succ : to_vector(Old->getSuccessors()))
      Succ->replacePredecessor(Old, New);
    New->setPredecessors(Old->getPredecessors());
    New->setSuccessors(Old->getSuccessors());
    Old->clearPredecessors();
    Old->clearSuccessors();
  }

  /// Transfer successors from \p Old to \p New. \p New must have no successors.
  static void transferSuccessors(VPBlockBase *Old, VPBlockBase *New) {
    for (auto *Succ : Old->getSuccessors())
      Succ->replacePredecessor(Old, New);
    New->setSuccessors(Old->getSuccessors());
    Old->clearSuccessors();
  }

  /// Clone the CFG for all nodes reachable from \p Entry, including cloning
  /// the blocks and their recipes. Operands of cloned recipes will NOT be
  /// updated. Remapping of operands must be done separately. Returns a pair
  /// with the new entry and exiting blocks of the cloned region. If \p Entry
  /// isn't part of a region, return nullptr for the exiting block.
  static std::pair<VPBlockBase *, VPBlockBase *> cloneFrom(VPBlockBase *Entry);

  /// Return an iterator range over \p Range which only includes \p BlockTy
  /// blocks. The accesses are casted to \p BlockTy.
  template <typename BlockTy, typename T> static auto blocksOnly(T &&Range) {
    // Create BaseTy with correct const-ness based on BlockTy.
    using BaseTy = std::conditional_t<std::is_const<BlockTy>::value,
                                      const VPBlockBase, VPBlockBase>;

    // We need to first create an iterator range over (const) BlocktTy & instead
    // of (const) BlockTy * for filter_range to work properly.
    auto Mapped =
        map_range(Range, [](BaseTy *Block) -> BaseTy & { return *Block; });
    auto Filter = make_filter_range(
        Mapped, [](BaseTy &Block) { return isa<BlockTy>(&Block); });
    return map_range(Filter, [](BaseTy &Block) -> BlockTy * {
      return cast<BlockTy>(&Block);
    });
  }

  /// Returns the blocks between \p FirstBB and \p LastBB, where FirstBB
  /// to LastBB forms a single-sucessor chain.
  static SmallVector<VPBasicBlock *>
  blocksInSingleSuccessorChainBetween(VPBasicBlock *FirstBB,
                                      VPBasicBlock *LastBB);

  /// Inserts \p BlockPtr on the edge between \p From and \p To. That is, update
  /// \p From's successor to \p To to point to \p BlockPtr and \p To's
  /// predecessor from \p From to \p BlockPtr. \p From and \p To are added to \p
  /// BlockPtr's predecessors and successors respectively. There must be a
  /// single edge between \p From and \p To.
  static void insertOnEdge(VPBlockBase *From, VPBlockBase *To,
                           VPBlockBase *BlockPtr) {
    unsigned SuccIdx = From->getIndexForSuccessor(To);
    unsigned PredIx = To->getIndexForPredecessor(From);
    VPBlockUtils::connectBlocks(From, BlockPtr, -1, SuccIdx);
    VPBlockUtils::connectBlocks(BlockPtr, To, PredIx, -1);
  }

  /// Returns true if \p VPB is a loop header, based on regions or \p VPDT in
  /// their absence.
  static bool isHeader(const VPBlockBase *VPB, const VPDominatorTree &VPDT);

  /// Returns true if \p VPB is a loop latch, using isHeader().
  static bool isLatch(const VPBlockBase *VPB, const VPDominatorTree &VPDT);
};

} // namespace llvm

#endif