LowerVectorTransfer.cpp

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//===- VectorTransferPermutationMapRewritePatterns.cpp - Xfer map rewrite -===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements rewrite patterns for the permutation_map attribute of
// vector.transfer operations.
//
//===----------------------------------------------------------------------===//
 
#include "mlir/Dialect/MemRef/IR/MemRef.h"
#include "mlir/Dialect/Vector/Transforms/LoweringPatterns.h"
 
using namespace mlir;
using namespace mlir::vector;
 
/// Transpose a vector transfer op's `in_bounds` attribute by applying reverse
/// permutation based on the given indices.
static ArrayAttr
inverseTransposeInBoundsAttr(OpBuilder &builder, ArrayAttr attr,
                             const SmallVector<unsigned> &permutation) {
  SmallVector<bool> newInBoundsValues(permutation.size());
  size_t index = 0;
  for (unsigned pos : permutation)
    newInBoundsValues[pos] =
        cast<BoolAttr>(attr.getValue()[index++]).getValue();
  return builder.getBoolArrayAttr(newInBoundsValues);
}
 
/// Insert unit dims into `vec` so that they are at `unitDimPositions` in the
/// result, e.g. position 1 turns `vector<4x8xf32>` into `vector<4x1x8xf32>`.
static Value insertUnitDims(OpBuilder &builder, Location loc, Value vec,
                            ArrayRef<int64_t> unitDimPositions) {
  auto vecType = cast<VectorType>(vec.getType());
  int64_t numUnitDims = unitDimPositions.size();
  // Broadcast to add the unit dims as the outermost dims.
  SmallVector<int64_t> newDims(numUnitDims, 1);
  llvm::append_range(newDims, vecType.getShape());
  SmallVector<bool> newScalableFlags(numUnitDims, false);
  llvm::append_range(newScalableFlags, vecType.getScalableDims());
  VectorType newVecType =
      VectorType::get(newDims, vecType.getElementType(), newScalableFlags);
  Value broadcast = vector::BroadcastOp::create(builder, loc, newVecType, vec);
  // Transpose them into place. The other dims keep their order.
  SmallVector<int64_t> permutation(newDims.size(), -1);
  for (auto [i, pos] : llvm::enumerate(unitDimPositions))
    permutation[pos] = i;
  int64_t nextDim = numUnitDims;
  for (int64_t &dim : permutation)
    if (dim == -1)
      dim = nextDim++;
  if (isIdentityPermutation(permutation))
    return broadcast;
  return vector::TransposeOp::create(builder, loc, broadcast, permutation);
}
 
//===----------------------------------------------------------------------===//
// populateVectorTransferPermutationMapLoweringPatterns
//===----------------------------------------------------------------------===//
 
namespace {
/// Lower transfer_read op with permutation into a transfer_read with a
/// permutation map composed of leading zeros followed by a minor identiy +
/// vector.transpose op.
/// Ex:
///     vector.transfer_read ...
///         permutation_map: (d0, d1, d2) -> (0, d1)
/// into:
///     %v = vector.transfer_read ...
///         permutation_map: (d0, d1, d2) -> (d1, 0)
///     vector.transpose %v, [1, 0]
///
///     vector.transfer_read ...
///         permutation_map: (d0, d1, d2, d3) -> (0, 0, 0, d1, d3)
/// into:
///     %v = vector.transfer_read ...
///         permutation_map: (d0, d1, d2, d3) -> (0, 0, d1, 0, d3)
///     vector.transpose %v, [0, 1, 3, 2, 4]
/// Note that an alternative is to transform it to linalg.transpose +
/// vector.transfer_read to do the transpose in memory instead.
struct TransferReadPermutationLowering
    : public MaskableOpRewritePattern<vector::TransferReadOp> {
  using MaskableOpRewritePattern::MaskableOpRewritePattern;
 
  FailureOr<mlir::Value>
  matchAndRewriteMaskableOp(vector::TransferReadOp op,
                            MaskingOpInterface maskOp,
                            PatternRewriter &rewriter) const override {
    // TODO: support 0-d corner case.
    if (op.getTransferRank() == 0)
      return rewriter.notifyMatchFailure(op, "0-d corner case not supported");
 
    SmallVector<unsigned> permutation;
    AffineMap map = op.getPermutationMap();
    if (map.getNumResults() == 0)
      return rewriter.notifyMatchFailure(op, "0 result permutation map");
    if (!map.isPermutationOfMinorIdentityWithBroadcasting(permutation)) {
      return rewriter.notifyMatchFailure(
          op, "map is not permutable to minor identity, apply another pattern");
    }
    AffineMap permutationMap =
        map.getPermutationMap(permutation, op.getContext());
    if (permutationMap.isIdentity())
      return rewriter.notifyMatchFailure(op, "map is not identity");
 
    permutationMap = map.getPermutationMap(permutation, op.getContext());
    // Caluclate the map of the new read by applying the inverse permutation.
    permutationMap = inversePermutation(permutationMap);
    AffineMap newMap = permutationMap.compose(map);
    // Apply the reverse transpose to deduce the type of the transfer_read.
    ArrayRef<int64_t> originalShape = op.getVectorType().getShape();
    SmallVector<int64_t> newVectorShape(originalShape.size());
    ArrayRef<bool> originalScalableDims = op.getVectorType().getScalableDims();
    SmallVector<bool> newScalableDims(originalShape.size());
    for (const auto &pos : llvm::enumerate(permutation)) {
      newVectorShape[pos.value()] = originalShape[pos.index()];
      newScalableDims[pos.value()] = originalScalableDims[pos.index()];
    }
 
    // Transpose in_bounds attribute.
    ArrayAttr newInBoundsAttr =
        inverseTransposeInBoundsAttr(rewriter, op.getInBounds(), permutation);
 
    // Generate new transfer_read operation.
    VectorType newReadType = VectorType::get(
        newVectorShape, op.getVectorType().getElementType(), newScalableDims);
    Operation *newRead = vector::TransferReadOp::create(
        rewriter, op.getLoc(), newReadType, op.getBase(), op.getIndices(),
        AffineMapAttr::get(newMap), op.getPadding(), op.getMask(),
        newInBoundsAttr);
 
    SmallVector<int64_t> transposePerm(permutation.begin(), permutation.end());
 
    // Re-apply an enclosing vector.mask. Its mask is indexed in memory order,
    // so only the passthru has to be transposed.
    if (maskOp) {
      Value passthru = maskOp.getPassthru();
      if (passthru)
        passthru =
            vector::TransposeOp::create(rewriter, op.getLoc(), passthru,
                                        invertPermutationVector(transposePerm));
      newRead =
          vector::maskOperation(rewriter, newRead, maskOp.getMask(), passthru);
    }
 
    // Transpose result of transfer_read.
    return vector::TransposeOp::create(rewriter, op.getLoc(),
                                       newRead->getResult(0), transposePerm)
        .getResult();
  }
};
 
/// Lower transfer_write op with permutation into a transfer_write with a
/// minor identity permutation map. (transfer_write ops cannot have broadcasts.)
/// Ex:
///     vector.transfer_write %v ...
///         permutation_map: (d0, d1, d2) -> (d2, d0, d1)
/// into:
///     %tmp = vector.transpose %v, [2, 0, 1]
///     vector.transfer_write %tmp ...
///         permutation_map: (d0, d1, d2) -> (d0, d1, d2)
///
///     vector.transfer_write %v ...
///         permutation_map: (d0, d1, d2, d3) -> (d3, d2)
/// into:
///     %tmp = vector.transpose %v, [1, 0]
///     %v = vector.transfer_write %tmp ...
///         permutation_map: (d0, d1, d2, d3) -> (d2, d3)
struct TransferWritePermutationLowering
    : public MaskableOpRewritePattern<vector::TransferWriteOp> {
  using MaskableOpRewritePattern::MaskableOpRewritePattern;
 
  FailureOr<mlir::Value>
  matchAndRewriteMaskableOp(vector::TransferWriteOp op,
                            MaskingOpInterface maskOp,
                            PatternRewriter &rewriter) const override {
    // TODO: support 0-d corner case.
    if (op.getTransferRank() == 0)
      return rewriter.notifyMatchFailure(op, "0-d corner case not supported");
 
    SmallVector<unsigned> permutation;
    AffineMap map = op.getPermutationMap();
    if (map.isMinorIdentity())
      return rewriter.notifyMatchFailure(op, "map is already minor identity");
 
    if (!map.isPermutationOfMinorIdentityWithBroadcasting(permutation)) {
      return rewriter.notifyMatchFailure(
          op, "map is not permutable to minor identity, apply another pattern");
    }
 
    // Remove unused dims from the permutation map. E.g.:
    // E.g.:  (d0, d1, d2, d3, d4, d5) -> (d5, d3, d4)
    // comp = (d0, d1, d2) -> (d2, d0, d1)
    auto comp = compressUnusedDims(map);
    AffineMap permutationMap = inversePermutation(comp);
    // Get positions of remaining result dims.
    SmallVector<int64_t> indices;
    llvm::transform(permutationMap.getResults(), std::back_inserter(indices),
                    [](AffineExpr expr) {
                      return dyn_cast<AffineDimExpr>(expr).getPosition();
                    });
 
    // Transpose in_bounds attribute.
    ArrayAttr newInBoundsAttr =
        inverseTransposeInBoundsAttr(rewriter, op.getInBounds(), permutation);
 
    // Generate new transfer_write operation.
    Value newVec = vector::TransposeOp::create(rewriter, op.getLoc(),
                                               op.getVector(), indices);
    auto newMap = AffineMap::getMinorIdentityMap(
        map.getNumDims(), map.getNumResults(), rewriter.getContext());
    auto newWrite = vector::TransferWriteOp::create(
        rewriter, op.getLoc(), newVec, op.getBase(), op.getIndices(),
        AffineMapAttr::get(newMap), op.getMask(), newInBoundsAttr);
 
    // Re-apply an enclosing vector.mask. Its mask is indexed in memory order,
    // so transposing the written vector leaves it unchanged.
    Operation *rewritten = newWrite;
    if (maskOp)
      rewritten = vector::maskOperation(rewriter, newWrite, maskOp.getMask());
 
    if (newWrite.hasPureTensorSemantics())
      return rewritten->getResult(0);
    // In the memref case there's no return value. Use empty value to signal
    // success.
    return Value();
  }
};
 
/// Convert a transfer.write op with a map which isn't the permutation of a
/// minor identity into a vector.broadcast + transfer_write with permutation of
/// minor identity map by adding unit dim on inner dimension. Ex:
/// ```
///   vector.transfer_write %v
///     {permutation_map = affine_map<(d0, d1, d2, d3) -> (d1, d2)>} :
///     vector<8x16xf32>
/// ```
/// into:
/// ```
///   %v1 = vector.broadcast %v : vector<8x16xf32> to vector<1x8x16xf32>
///   vector.transfer_write %v1
///     {permutation_map = affine_map<(d0, d1, d2, d3) -> (d3, d1, d2)>} :
///     vector<1x8x16xf32>
/// ```
struct TransferWriteNonPermutationLowering
    : public MaskableOpRewritePattern<vector::TransferWriteOp> {
  using MaskableOpRewritePattern::MaskableOpRewritePattern;
 
  FailureOr<mlir::Value>
  matchAndRewriteMaskableOp(vector::TransferWriteOp op,
                            MaskingOpInterface maskOp,
                            PatternRewriter &rewriter) const override {
    // TODO: support 0-d corner case.
    if (op.getTransferRank() == 0)
      return rewriter.notifyMatchFailure(op, "0-d corner case not supported");
    // TODO: Support transfer_write inside MaskOp case.
    if (maskOp)
      return rewriter.notifyMatchFailure(op, "Masked case not supported");
 
    SmallVector<unsigned> permutation;
    AffineMap map = op.getPermutationMap();
    if (map.isPermutationOfMinorIdentityWithBroadcasting(permutation)) {
      return rewriter.notifyMatchFailure(
          op,
          "map is already permutable to minor identity, apply another pattern");
    }
 
    // Missing outer dimensions are allowed, find the most outer existing
    // dimension then deduce the missing inner dimensions.
    SmallVector<bool> foundDim(map.getNumDims(), false);
    for (AffineExpr exp : map.getResults())
      foundDim[cast<AffineDimExpr>(exp).getPosition()] = true;
    SmallVector<AffineExpr> exprs;
    std::optional<size_t> firstDim;
    SmallVector<int64_t> missingInnerDim;
    for (size_t i = 0; i < foundDim.size(); i++) {
      if (foundDim[i]) {
        if (!firstDim)
          firstDim = i;
        continue;
      }
      if (!firstDim)
        continue;
      // Once we found one outer dimension existing in the map keep track of all
      // the missing dimensions after that, relative to that dimension.
      missingInnerDim.push_back(i - *firstDim);
      exprs.push_back(rewriter.getAffineDimExpr(i));
    }
    // Vector: add unit dims at the beginning of the shape.
    Value newVec = insertUnitDims(
        rewriter, op.getLoc(), op.getVector(),
        llvm::to_vector(llvm::seq<int64_t>(missingInnerDim.size())));
    // Mask: add unit dims at the positions of the missing dimensions. Dim 0 of
    // the mask is the first written dim.
    Value newMask;
    if (op.getMask())
      newMask =
          insertUnitDims(rewriter, op.getLoc(), op.getMask(), missingInnerDim);
    exprs.append(map.getResults().begin(), map.getResults().end());
    AffineMap newMap =
        AffineMap::get(map.getNumDims(), 0, exprs, op.getContext());
    // All the new dimensions added are inbound.
    SmallVector<bool> newInBoundsValues(missingInnerDim.size(), true);
    for (int64_t i = 0, e = op.getVectorType().getRank(); i < e; ++i) {
      newInBoundsValues.push_back(op.isDimInBounds(i));
    }
    ArrayAttr newInBoundsAttr = rewriter.getBoolArrayAttr(newInBoundsValues);
    auto newWrite = vector::TransferWriteOp::create(
        rewriter, op.getLoc(), newVec, op.getBase(), op.getIndices(),
        AffineMapAttr::get(newMap), newMask, newInBoundsAttr);
    if (newWrite.hasPureTensorSemantics())
      return newWrite.getResult();
    // In the memref case there's no return value. Use empty value to signal
    // success.
    return Value();
  }
};
 
/// Lower transfer_read op with broadcast in the leading dimensions into
/// transfer_read of lower rank + vector.broadcast.
/// Ex: vector.transfer_read ...
///         permutation_map: (d0, d1, d2, d3) -> (0, d1, 0, d3)
/// into:
///     %v = vector.transfer_read ...
///         permutation_map: (d0, d1, d2, d3) -> (d1, 0, d3)
///     vector.broadcast %v
struct TransferOpReduceRank
    : public MaskableOpRewritePattern<vector::TransferReadOp> {
  using MaskableOpRewritePattern::MaskableOpRewritePattern;
 
  FailureOr<mlir::Value>
  matchAndRewriteMaskableOp(vector::TransferReadOp op,
                            MaskingOpInterface maskOp,
                            PatternRewriter &rewriter) const override {
    // TODO: support 0-d corner case.
    if (op.getTransferRank() == 0)
      return rewriter.notifyMatchFailure(op, "0-d corner case not supported");
    // TODO: support masked case.
    if (maskOp)
      return rewriter.notifyMatchFailure(op, "Masked case not supported");
 
    AffineMap map = op.getPermutationMap();
    unsigned numLeadingBroadcast = 0;
    for (auto expr : map.getResults()) {
      auto dimExpr = dyn_cast<AffineConstantExpr>(expr);
      if (!dimExpr || dimExpr.getValue() != 0)
        break;
      numLeadingBroadcast++;
    }
    // If there are no leading zeros in the map there is nothing to do.
    if (numLeadingBroadcast == 0)
      return rewriter.notifyMatchFailure(op, "no leading broadcasts in map");
 
    VectorType originalVecType = op.getVectorType();
    unsigned reducedShapeRank = originalVecType.getRank() - numLeadingBroadcast;
    // Calculate new map, vector type and masks without the leading zeros.
    AffineMap newMap = AffineMap::get(
        map.getNumDims(), 0, map.getResults().take_back(reducedShapeRank),
        op.getContext());
    // Only remove the leading zeros if the rest of the map is a minor identity
    // with broadasting. Otherwise we first want to permute the map.
    if (!newMap.isMinorIdentityWithBroadcasting()) {
      return rewriter.notifyMatchFailure(
          op, "map is not a minor identity with broadcasting");
    }
 
    SmallVector<int64_t> newShape(
        originalVecType.getShape().take_back(reducedShapeRank));
    SmallVector<bool> newScalableDims(
        originalVecType.getScalableDims().take_back(reducedShapeRank));
 
    VectorType newReadType = VectorType::get(
        newShape, originalVecType.getElementType(), newScalableDims);
    ArrayAttr newInBoundsAttr =
        op.getInBounds()
            ? rewriter.getArrayAttr(
                  op.getInBoundsAttr().getValue().take_back(reducedShapeRank))
            : ArrayAttr();
    Value newRead = vector::TransferReadOp::create(
        rewriter, op.getLoc(), newReadType, op.getBase(), op.getIndices(),
        AffineMapAttr::get(newMap), op.getPadding(), op.getMask(),
        newInBoundsAttr);
    return vector::BroadcastOp::create(rewriter, op.getLoc(), originalVecType,
                                       newRead)
        .getResult();
  }
};
 
} // namespace
 
void mlir::vector::populateVectorTransferPermutationMapLoweringPatterns(
    RewritePatternSet &patterns, PatternBenefit benefit) {
  patterns
      .add<TransferReadPermutationLowering, TransferWritePermutationLowering,
           TransferOpReduceRank, TransferWriteNonPermutationLowering>(
          patterns.getContext(), benefit);
}
 
//===----------------------------------------------------------------------===//
// populateVectorTransferLoweringPatterns
//===----------------------------------------------------------------------===//
 
namespace {
/// Progressive lowering of transfer_read. This pattern supports lowering of
/// `vector.transfer_read` to a combination of `vector.load` and
/// `vector.broadcast` if all of the following hold:
/// - Stride of most minor memref dimension must be 1.
/// - Out-of-bounds masking is not required.
/// - If the memref's element type is a vector type then it coincides with the
///   result type.
/// - The permutation map doesn't perform permutation (broadcasting is allowed).
struct TransferReadToVectorLoadLowering
    : public MaskableOpRewritePattern<vector::TransferReadOp> {
  TransferReadToVectorLoadLowering(MLIRContext *context,
                                   std::optional<unsigned> maxRank,
                                   PatternBenefit benefit = 1)
      : MaskableOpRewritePattern<vector::TransferReadOp>(context, benefit),
        maxTransferRank(maxRank) {}
 
  FailureOr<mlir::Value>
  matchAndRewriteMaskableOp(vector::TransferReadOp read,
                            MaskingOpInterface maskOp,
                            PatternRewriter &rewriter) const override {
    if (maxTransferRank && read.getVectorType().getRank() > *maxTransferRank) {
      return rewriter.notifyMatchFailure(
          read, "vector type is greater than max transfer rank");
    }
 
    if (maskOp)
      return rewriter.notifyMatchFailure(read, "Masked case not supported");
    SmallVector<unsigned> broadcastedDims;
    // Permutations are handled by VectorToSCF or
    // populateVectorTransferPermutationMapLoweringPatterns.
    // We let the 0-d corner case pass-through as it is supported.
    if (!read.getPermutationMap().isMinorIdentityWithBroadcasting(
            &broadcastedDims))
      return rewriter.notifyMatchFailure(read, "not minor identity + bcast");
 
    auto memRefType = dyn_cast<MemRefType>(read.getShapedType());
    if (!memRefType)
      return rewriter.notifyMatchFailure(read, "not a memref source");
 
    // Non-unit strides are handled by VectorToSCF.
    if (!memRefType.isLastDimUnitStride())
      return rewriter.notifyMatchFailure(read, "!= 1 stride needs VectorToSCF");
 
    // If there is broadcasting involved then we first load the unbroadcasted
    // vector, and then broadcast it with `vector.broadcast`.
    ArrayRef<int64_t> vectorShape = read.getVectorType().getShape();
    SmallVector<int64_t> unbroadcastedVectorShape(vectorShape);
    for (unsigned i : broadcastedDims)
      unbroadcastedVectorShape[i] = 1;
    VectorType unbroadcastedVectorType = read.getVectorType().cloneWith(
        unbroadcastedVectorShape, read.getVectorType().getElementType());
 
    // `vector.load` supports vector types as memref's elements only when the
    // resulting vector type is the same as the element type.
    auto memrefElTy = memRefType.getElementType();
    if (isa<VectorType>(memrefElTy) && memrefElTy != unbroadcastedVectorType)
      return rewriter.notifyMatchFailure(read, "incompatible element type");
 
    // Otherwise, element types of the memref and the vector must match.
    if (!isa<VectorType>(memrefElTy) &&
        memrefElTy != read.getVectorType().getElementType())
      return rewriter.notifyMatchFailure(read, "non-matching element type");
 
    // Out-of-bounds dims are handled by MaterializeTransferMask.
    if (read.hasOutOfBoundsDim())
      return rewriter.notifyMatchFailure(read, "out-of-bounds needs mask");
 
    // Create vector load op.
    Operation *res;
    if (read.getMask()) {
      if (read.getVectorType().getRank() != 1)
        // vector.maskedload operates on 1-D vectors.
        return rewriter.notifyMatchFailure(
            read, "vector type is not rank 1, can't create masked load, needs "
                  "VectorToSCF");
 
      Value fill = vector::BroadcastOp::create(
          rewriter, read.getLoc(), unbroadcastedVectorType, read.getPadding());
      res = vector::MaskedLoadOp::create(
          rewriter, read.getLoc(), unbroadcastedVectorType, read.getBase(),
          read.getIndices(), read.getMask(), fill);
    } else {
      res = vector::LoadOp::create(rewriter, read.getLoc(),
                                   unbroadcastedVectorType, read.getBase(),
                                   read.getIndices());
    }
 
    // Insert a broadcasting op if required.
    if (!broadcastedDims.empty())
      res = vector::BroadcastOp::create(
          rewriter, read.getLoc(), read.getVectorType(), res->getResult(0));
    return res->getResult(0);
  }
 
  std::optional<unsigned> maxTransferRank;
};
 
/// Progressive lowering of transfer_write. This pattern supports lowering of
/// `vector.transfer_write` to `vector.store` if all of the following hold:
/// - Stride of most minor memref dimension must be 1.
/// - Out-of-bounds masking is not required.
/// - If the memref's element type is a vector type then it coincides with the
///   type of the written value.
/// - The permutation map is the minor identity map (neither permutation nor
///   broadcasting is allowed).
struct TransferWriteToVectorStoreLowering
    : public MaskableOpRewritePattern<vector::TransferWriteOp> {
  TransferWriteToVectorStoreLowering(MLIRContext *context,
                                     std::optional<unsigned> maxRank,
                                     PatternBenefit benefit = 1)
      : MaskableOpRewritePattern<vector::TransferWriteOp>(context, benefit),
        maxTransferRank(maxRank) {}
 
  FailureOr<mlir::Value>
  matchAndRewriteMaskableOp(vector::TransferWriteOp write,
                            MaskingOpInterface maskOp,
                            PatternRewriter &rewriter) const override {
    if (maxTransferRank && write.getVectorType().getRank() > *maxTransferRank) {
      return rewriter.notifyMatchFailure(
          write, "vector type is greater than max transfer rank");
    }
    if (maskOp)
      return rewriter.notifyMatchFailure(write, "Masked case not supported");
 
    // Permutations are handled by VectorToSCF or
    // populateVectorTransferPermutationMapLoweringPatterns.
    if ( // pass-through for the 0-d corner case.
        !write.getPermutationMap().isMinorIdentity())
      return rewriter.notifyMatchFailure(write.getLoc(), [=](Diagnostic &diag) {
        diag << "permutation map is not minor identity: " << write;
      });
 
    auto memRefType = dyn_cast<MemRefType>(write.getShapedType());
    if (!memRefType)
      return rewriter.notifyMatchFailure(write.getLoc(), [=](Diagnostic &diag) {
        diag << "not a memref type: " << write;
      });
 
    // Non-unit strides are handled by VectorToSCF.
    if (!memRefType.isLastDimUnitStride())
      return rewriter.notifyMatchFailure(write.getLoc(), [=](Diagnostic &diag) {
        diag << "most minor stride is not 1: " << write;
      });
 
    // `vector.store` supports vector types as memref's elements only when the
    // type of the vector value being written is the same as the element type.
    auto memrefElTy = memRefType.getElementType();
    if (isa<VectorType>(memrefElTy) && memrefElTy != write.getVectorType())
      return rewriter.notifyMatchFailure(write.getLoc(), [=](Diagnostic &diag) {
        diag << "elemental type mismatch: " << write;
      });
 
    // Otherwise, element types of the memref and the vector must match.
    if (!isa<VectorType>(memrefElTy) &&
        memrefElTy != write.getVectorType().getElementType())
      return rewriter.notifyMatchFailure(write.getLoc(), [=](Diagnostic &diag) {
        diag << "elemental type mismatch: " << write;
      });
 
    // Out-of-bounds dims are handled by MaterializeTransferMask.
    if (write.hasOutOfBoundsDim())
      return rewriter.notifyMatchFailure(write.getLoc(), [=](Diagnostic &diag) {
        diag << "out of bounds dim: " << write;
      });
    if (write.getMask()) {
      if (write.getVectorType().getRank() != 1)
        // vector.maskedstore operates on 1-D vectors.
        return rewriter.notifyMatchFailure(
            write.getLoc(), [=](Diagnostic &diag) {
              diag << "vector type is not rank 1, can't create masked store, "
                      "needs VectorToSCF: "
                   << write;
            });
 
      vector::MaskedStoreOp::create(rewriter, write.getLoc(), write.getBase(),
                                    write.getIndices(), write.getMask(),
                                    write.getVector());
    } else {
      vector::StoreOp::create(rewriter, write.getLoc(), write.getVector(),
                              write.getBase(), write.getIndices());
    }
    // There's no return value for StoreOps. Use Value() to signal success to
    // matchAndRewrite.
    return Value();
  }
 
  std::optional<unsigned> maxTransferRank;
};
} // namespace
 
void mlir::vector::populateVectorTransferLoweringPatterns(
    RewritePatternSet &patterns, std::optional<unsigned> maxTransferRank,
    PatternBenefit benefit) {
  patterns.add<TransferReadToVectorLoadLowering,
               TransferWriteToVectorStoreLowering>(patterns.getContext(),
                                                   maxTransferRank, benefit);
}