[mlir][Vector] Add transformation + pattern to split vector.transfer_read into full and partial copies.

[nicolasvasilache]

Summary

This revision adds a transformation and a pattern that rewrites a "maybe masked" vector.transfer_read %view[...], %pad into a pattern resembling:

%1:3 = scf.if (%inBounds) {
   scf.yield %view : memref<A...>, index, index
 } else {
   %2 = vector.transfer_read %view[...], %pad : memref<A...>, vector<...>
   %3 = vector.type_cast %extra_alloc : memref<...> to
   memref<vector<...>> store %2, %3[] : memref<vector<...>> %4 =
   memref_cast %extra_alloc: memref<B...> to memref<A...> scf.yield %4 :
   memref<A...>, index, index
}
%res= vector.transfer_read %1#0[%1#1, %1#2] {masked = [false ... false]}

where extra_alloc is a top of the function alloca'ed buffer of one vector.

This rewrite makes it possible to realize the "always full tile" abstraction where vector.transfer_read operations are guaranteed to read from a padded full buffer.
The extra work only occurs on the boundary tiles.

[nicolasvasilache]

Drop CMake changes.

[nicolasvasilache]

Fix map capture, $ is now required for globals.

[nicolasvasilache]

Make alloca default again.

[asaadaldien]

mlir/lib/Dialect/Vector/VectorTransforms.cpp

2041

duplicate condition, remove ?

[aartbik]

mlir/include/mlir/Dialect/Vector/VectorTransforms.h

24

lint wants

// namespace scf

113

The "If ...." sentence seems hanging. Does it belong to anything?

[nicolasvasilache]

Address review.

[nicolasvasilache]

Deterministic IR.

[aartbik]

Change LGTM, however, consider adding a bit more comments to make the large blocks a bit more readable.

mlir/lib/Dialect/Vector/VectorTransforms.cpp

2017

By adding a bit more comments to the zipResultAndIndexing body, the structure of this call may be a bit more clear

2082

you have a good documenting comment in the header file for matchAndRewrite(). However, this implementation code would benefit if you repeat some of what you are doing here, just to link it back to what you are generating where.

[nicolasvasilache]

mlir/lib/Dialect/Vector/VectorTransforms.cpp

2082

Some like to reproduce comments in both the .h and the .cpp
I went ahead and did that.

[nicolasvasilache]

Add comments.

mlir/include/mlir/Dialect/Vector/VectorTransforms.h

 #include "mlir/Dialect/Vector/VectorOps.h"
 #include "mlir/Dialect/Vector/VectorUtils.h"
 #include "mlir/IR/Function.h"
 #include "mlir/IR/PatternMatch.h"
 
 namespace mlir {
 class MLIRContext;
 class OwningRewritePatternList;
+class VectorTransferOpInterface;
+
+namespace scf {
+class IfOp;
+};
 
 /// Collect a set of patterns to convert from the Vector dialect to itself.
 /// Should be merged with populateVectorToSCFLoweringPattern.
 void populateVectorToVectorConversionPatterns(
     MLIRContext *context, OwningRewritePatternList &patterns,
     ArrayRef<int64_t> coarseVectorShape = {},
     ArrayRef<int64_t> fineVectorShape = {});
 
LogicalResult matchAndRewrite(OpTy op,
     return success();
   }
 
 private:
   SmallVector<int64_t, 4> targetShape;
   FilterConstraintType filter;
 };
 
+/// Split a vector.transfer operation into an unmasked fastpath vector.transfer
+/// and a slowpath masked vector.transfer. If `ifOp` is not null and the result
+/// is `success`. To accomodate for the fact that the original vector.transfer
+/// indexing may be arbitrary and the slow path indexes @[0...0] in the
+/// temporary buffer, the scf.if op returns a view and values of type index.
+/// At this time, only vector.transfer_read is implemented.
+///
+/// Example (a 2-D vector.transfer_read):
+/// ```
+///    %1 = vector.transfer_read %0[...], %pad : memref<A...>, vector<...>
+/// ```
+/// is transformed into:
+/// ```
+///    %1:3 = scf.if (%inBounds) {
+///       scf.yield %0 : memref<A...>, index, index
+///     } else {
+///       %2 = vector.transfer_read %0[...], %pad : memref<A...>, vector<...>
+///       %3 = vector.type_cast %extra_alloc : memref<...> to
+///       memref<vector<...>> store %2, %3[] : memref<vector<...>> %4 =
+///       memref_cast %extra_alloc: memref<B...> to memref<A...> scf.yield %4 :
+///       memref<A...>, index, index
+//     }
+///    %0 = vector.transfer_read %1#0[%1#1, %1#2] {masked = [false ... false]}
+/// ```
+/// where `extra_alloc` is a top of the function alloca'ed buffer of one vector.
+///
+/// Preconditions:
+///  1. `xferOp.permutation_map()` must be a minor identity map
+///  2. the rank of the `xferOp.memref()` and the rank of the `xferOp.vector()`
+///  must be equal. This will be relaxed in the future but requires
+///  rank-reducing subviews.
+LogicalResult
+splitFullAndPartialTransferPrecondition(VectorTransferOpInterface xferOp);
+LogicalResult splitFullAndPartialTransfer(OpBuilder &b,
+                                          VectorTransferOpInterface xferOp,
+                                          scf::IfOp *ifOp = nullptr);
+
+/// Apply `splitFullAndPartialTransfer` selectively via a pattern. This pattern
+/// may take an extra filter to perform selection at a finer granularity.
+struct VectorTransferFullPartialRewriter : public RewritePattern {
+  using FilterConstraintType =
+      std::function<LogicalResult(VectorTransferOpInterface op)>;
+
+  explicit VectorTransferFullPartialRewriter(
+      MLIRContext *context,
+      FilterConstraintType filter =
+          [](VectorTransferOpInterface op) { return success(); },
+      PatternBenefit benefit = 1)
+      : RewritePattern(benefit, MatchAnyOpTypeTag()), filter(filter) {}
+
+  /// Performs the rewrite.
+  LogicalResult matchAndRewrite(Operation *op,
+                                PatternRewriter &rewriter) const override;
+
+private:
+  FilterConstraintType filter;
+};
+
 } // namespace vector
 
 //===----------------------------------------------------------------------===//
 // Finer-grained patterns exposed for more control over individual lowerings.
 //===----------------------------------------------------------------------===//
 
 /// Progressive lowering of a `vector.contract %a, %b, %c` with row-major matmul
 /// semantics to:

mlir/include/mlir/Interfaces/VectorInterfaces.td

InterfaceMethod<
       /*retTy=*/"unsigned",
       /*methodName=*/"getLeadingMemRefRank",
       /*args=*/(ins),
       /*methodBody=*/"",
       /*defaultImplementation=*/
         "return $_op.getMemRefType().getRank() - $_op.getTransferRank();"
     >,
     InterfaceMethod<
+      /*desc=*/[{ Returns true if at least one of the dimensions is masked.}],
+      /*retTy=*/"bool",
+      /*methodName=*/"hasMaskedDim",
+      /*args=*/(ins),
+      /*methodBody=*/"",
+      /*defaultImplementation=*/[{
+        for (unsigned idx = 0, e = $_op.getTransferRank(); idx < e; ++idx)
+          if ($_op.isMaskedDim(idx))
+            return true;
+        return false;
+      }]
+    >,
+    InterfaceMethod<
       /*desc=*/[{
       Helper function to account for the fact that `permutationMap` results and
       `op.indices` sizes may not match and may not be aligned. The first
       `getLeadingMemRefRank()` indices may just be indexed and not transferred
       from/into the vector.
       For example:
       ```
          vector.transfer %0[%i, %j, %k, %c0] :

mlir/lib/Dialect/Vector/VectorTransforms.cpp

 //===- VectorTransforms.cpp - Conversion within the Vector dialect --------===//
 //
 // 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 target-independent rewrites as 1->N patterns.
 //
 //===----------------------------------------------------------------------===//
 
 #include <type_traits>
 
+#include "mlir/Dialect/Affine/EDSC/Intrinsics.h"
 #include "mlir/Dialect/Affine/IR/AffineOps.h"
+#include "mlir/Dialect/SCF/EDSC/Intrinsics.h"
+#include "mlir/Dialect/StandardOps/EDSC/Intrinsics.h"
 #include "mlir/Dialect/StandardOps/IR/Ops.h"
 #include "mlir/Dialect/Utils/StructuredOpsUtils.h"
+#include "mlir/Dialect/Vector/EDSC/Intrinsics.h"
 #include "mlir/Dialect/Vector/VectorOps.h"
 #include "mlir/Dialect/Vector/VectorTransforms.h"
 #include "mlir/Dialect/Vector/VectorUtils.h"
 #include "mlir/IR/AffineExpr.h"
 #include "mlir/IR/AffineMap.h"
 #include "mlir/IR/Attributes.h"
 #include "mlir/IR/Builders.h"
 #include "mlir/IR/Function.h"
for (int64_t d = 0; d < dimSize; ++d) {
     result = rewriter.create<vector::ContractionOp>(loc, lhs, rhs, result,
                                                     lowAffine, lowIter);
   }
   return result;
 }
 
 } // namespace mlir
 
+static Optional<int64_t> extractConstantIndex(Value v) {
+  if (auto cstOp = v.getDefiningOp<ConstantIndexOp>())
+    return cstOp.getValue();
+  if (auto affineApplyOp = v.getDefiningOp<AffineApplyOp>())
+    if (affineApplyOp.getAffineMap().isSingleConstant())
+      return affineApplyOp.getAffineMap().getSingleConstantResult();
+  return None;
+}
+
+// Missing foldings of scf.if make it necessary to perform poor man's folding
+// eagerly, especially in the case of unrolling. In the future, this should go
+// away once scf.if folds properly.
+static Value createScopedFoldedSLE(Value v, Value ub) {
+  using namespace edsc::op;
+  auto maybeCstV = extractConstantIndex(v);
+  auto maybeCstUb = extractConstantIndex(ub);
+  if (maybeCstV && maybeCstUb && *maybeCstV < *maybeCstUb)
+    return Value();
+  return sle(v, ub);
+}
+
+// Operates under a scoped context to build the condition to ensure that a
+// particular VectorTransferOpInterface is unmasked.
+static Value createScopedInBoundsCond(VectorTransferOpInterface xferOp) {
+  Value inBoundsCond;
+  xferOp.zipResultAndIndexing([&](int64_t resultIdx, int64_t indicesIdx) {
+    if (!xferOp.isMaskedDim(resultIdx))
+      return;
+    int64_t vectorSize = xferOp.getVectorType().getDimSize(resultIdx);
+    using namespace edsc::op;
+    using namespace edsc::intrinsics;
+    Value cond = createScopedFoldedSLE(xferOp.indices()[indicesIdx] +
+                                           std_constant_index(vectorSize),
+                                       std_dim(xferOp.memref(), indicesIdx));
+    if (!cond)
+      return;
+    inBoundsCond = inBoundsCond ? inBoundsCond && cond : cond;
+  });
+  return inBoundsCond;
+}
+
+LogicalResult mlir::vector::splitFullAndPartialTransferPrecondition(
+    VectorTransferOpInterface xferOp) {
+  // TODO: expand support to these 2 cases.
+  if (!xferOp.permutation_map().isMinorIdentity())
+    return failure();
+  // TODO: relax this precondition. This will require rank-reducing subviews.
+  if (xferOp.getMemRefType().getRank() != xferOp.getTransferRank())
+    return failure();
+  if (xferOp.getMemRefType().getRank() != xferOp.getTransferRank())
+    return failure();
+  // Must have some masked dimension to be a candidate for splitting.
+  if (!xferOp.hasMaskedDim())
+    return failure();
+  // Don't split transfer operations under IfOp, this avoids applying the
+  // pattern recursively.
+  // TODO: improve the condition to make it more applicable.
+  if (xferOp.getParentOfType<scf::IfOp>())
+    return failure();
+  return success();
+}
+
+MemRefType getCastCompatibleMemRefType(MemRefType aT, MemRefType bT) {
+  if (MemRefCastOp::areCastCompatible(aT, bT))
+    return aT;
+  if (aT.getRank() != bT.getRank())
+    return MemRefType();
+  int64_t aOffset, bOffset;
+  SmallVector<int64_t, 4> aStrides, bStrides;
+  if (failed(getStridesAndOffset(aT, aStrides, aOffset)) ||
+      failed(getStridesAndOffset(bT, bStrides, bOffset)) ||
+      aStrides.size() != bStrides.size())
+    return MemRefType();
+
+  ArrayRef<int64_t> aShape = aT.getShape(), bShape = bT.getShape();
+  int64_t resOffset;
+  SmallVector<int64_t, 4> resShape(aT.getRank(), 0),
+      resStrides(bT.getRank(), 0);
+  for (int64_t idx = 0, e = aT.getRank(); idx < e; ++idx) {
+    resShape[idx] =
+        (aShape[idx] == bShape[idx]) ? aShape[idx] : MemRefType::kDynamicSize;
+    resStrides[idx] = (aStrides[idx] == bStrides[idx])
+                          ? aStrides[idx]
+                          : MemRefType::kDynamicStrideOrOffset;
+  }
+  resOffset =
+      (aOffset == bOffset) ? aOffset : MemRefType::kDynamicStrideOrOffset;
+  return MemRefType::get(
+      resShape, aT.getElementType(),
+      makeStridedLinearLayoutMap(resStrides, resOffset, aT.getContext()));
+}
+
+LogicalResult mlir::vector::splitFullAndPartialTransfer(
+    OpBuilder &b, VectorTransferOpInterface xferOp, scf::IfOp *ifOp) {
+  using namespace edsc;
+  using namespace edsc::intrinsics;
+
+  assert(succeeded(splitFullAndPartialTransferPrecondition(xferOp)) &&
+         "Expected splitFullAndPartialTransferPrecondition to hold");
+  auto xferReadOp = dyn_cast<vector::TransferReadOp>(xferOp.getOperation());
+
+  // TODO: add support for write case.
+  if (!xferReadOp)
+    return failure();
+
+  OpBuilder::InsertionGuard guard(b);
+  if (xferOp.memref().getDefiningOp())
+    b.setInsertionPointAfter(xferOp.memref().getDefiningOp());
+  else
+    b.setInsertionPoint(xferOp);
+  ScopedContext scope(b, xferOp.getLoc());
+  Value inBoundsCond = createScopedInBoundsCond(
+      cast<VectorTransferOpInterface>(xferOp.getOperation()));
+  if (!inBoundsCond)
+    return failure();
+
+  // Top of the function `alloc` for transient storage.
+  Value alloc;
+  {
+    FuncOp funcOp = xferOp.getParentOfType<FuncOp>();
+    OpBuilder::InsertionGuard guard(b);
+    b.setInsertionPointToStart(&funcOp.getRegion().front());
+    auto shape = xferOp.getVectorType().getShape();
+    Type elementType = xferOp.getVectorType().getElementType();
+    alloc = std_alloca(MemRefType::get(shape, elementType), ValueRange{},
+                       b.getI64IntegerAttr(32));
+  }
+
+  Value memref = xferOp.memref();
+  SmallVector<bool, 4> bools(xferOp.getTransferRank(), false);
+  auto unmaskedAttr = b.getBoolArrayAttr(bools);
+
+  MemRefType compatibleMemRefType = getCastCompatibleMemRefType(
+      xferOp.getMemRefType(), alloc.getType().cast<MemRefType>());
+
+  // Read case: full fill + partial copy -> unmasked vector.xfer_read.
+  Value zero = std_constant_index(0);
+  SmallVector<Type, 4> returnTypes(1 + xferOp.getTransferRank(),
+                                   b.getIndexType());
+  returnTypes[0] = compatibleMemRefType;
+  scf::IfOp fullPartialIfOp;
+  conditionBuilder(
+      returnTypes, inBoundsCond,
+      [&]() -> scf::ValueVector {
+        Value res = memref;
+        if (compatibleMemRefType != xferOp.getMemRefType())
+          res = std_memref_cast(memref, compatibleMemRefType);
+        scf::ValueVector viewAndIndices{res};
+        viewAndIndices.insert(viewAndIndices.end(), xferOp.indices().begin(),
+                              xferOp.indices().end());
+        return viewAndIndices;
+      },
+      [&]() -> scf::ValueVector {
+        Operation *newXfer =
+            ScopedContext::getBuilderRef().clone(*xferOp.getOperation());
+        Value vector = cast<VectorTransferOpInterface>(newXfer).vector();
+        std_store(vector, vector_type_cast(
+                              MemRefType::get({}, vector.getType()), alloc));
+
+        Value casted = std_memref_cast(alloc, compatibleMemRefType);
+        scf::ValueVector viewAndIndices{casted};
+        viewAndIndices.insert(viewAndIndices.end(), xferOp.getTransferRank(),
+                              zero);
+
+        return viewAndIndices;
+      },
+      &fullPartialIfOp);
+  if (ifOp)
+    *ifOp = fullPartialIfOp;
+
+  // Unmask the existing read op, it always reads from a full buffer.
+  for (unsigned i = 0, e = returnTypes.size(); i != e; ++i)
+    xferReadOp.setOperand(i, fullPartialIfOp.getResult(i));
+  xferOp.setAttr(vector::TransferReadOp::getMaskedAttrName(), unmaskedAttr);
+
+  return success();
+}
+
+LogicalResult mlir::vector::VectorTransferFullPartialRewriter::matchAndRewrite(
+    Operation *op, PatternRewriter &rewriter) const {
+  auto xferOp = dyn_cast<VectorTransferOpInterface>(op);
+  if (!xferOp || failed(splitFullAndPartialTransferPrecondition(xferOp)) ||
+      failed(filter(xferOp)))
+    return failure();
+  rewriter.startRootUpdate(xferOp);
+  if (succeeded(splitFullAndPartialTransfer(rewriter, xferOp))) {
+    rewriter.finalizeRootUpdate(xferOp);
+    return success();
+  }
+  rewriter.cancelRootUpdate(xferOp);
+  return failure();
+}
+
 // TODO: Add pattern to rewrite ExtractSlices(ConstantMaskOp).
 // TODO: Add this as DRR pattern.
 void mlir::vector::populateVectorToVectorTransformationPatterns(
     OwningRewritePatternList &patterns, MLIRContext *context) {
   // clang-format off
   patterns.insert<ShapeCastOpDecomposer,
                   ShapeCastOpFolder,
                   SplitTransferReadOp,

mlir/test/Dialect/Vector/vector-transfer-full-partial-split.mlir

+// RUN: mlir-opt %s -test-vector-transfer-full-partial-split | FileCheck %s
+
+// CHECK-DAG: #[[$map_p4:.*]] = affine_map<()[s0] -> (s0 + 4)>
+// CHECK-DAG: #[[$map_p8:.*]] = affine_map<()[s0] -> (s0 + 8)>
+// CHECK-DAG: #[[$map_2d_stride_1:.*]] = affine_map<(d0, d1)[s0, s1] -> (d0 * s1 + s0 + d1)>
+
+// CHECK-LABEL: split_vector_transfer_read_2d(
+//  CHECK-SAME: %[[A:[a-zA-Z0-9]*]]: memref
+//  CHECK-SAME: %[[i:[a-zA-Z0-9]*]]: index
+//  CHECK-SAME: %[[j:[a-zA-Z0-9]*]]: index
+func @split_vector_transfer_read_2d(%A: memref<?x8xf32>, %i: index, %j: index) -> vector<4x8xf32> {
+  %c0 = constant 0 : index
+  %f0 = constant 0.0 : f32
+
+  //  CHECK-DAG: %[[c0:.*]] = constant 0 : index
+  //  CHECK-DAG: %[[c8:.*]] = constant 8 : index
+  //  CHECK-DAG: %[[cst:.*]] = constant 0.000000e+00 : f32
+  // alloca for boundary full tile
+  //      CHECK: %[[alloc:.*]] = alloca() {alignment = 32 : i64} : memref<4x8xf32>
+  // %i + 4 <= dim(%A, 0)
+  //      CHECK: %[[idx0:.*]] = affine.apply #[[$map_p4]]()[%[[i]]]
+  //      CHECK: %[[d0:.*]] = dim %[[A]], %[[c0]] : memref<?x8xf32>
+  //      CHECK: %[[cmp0:.*]] = cmpi "sle", %[[idx0]], %[[d0]] : index
+  // %j + 8 <= dim(%A, 1)
+  //      CHECK: %[[idx1:.*]] = affine.apply #[[$map_p8]]()[%[[j]]]
+  //      CHECK: %[[cmp1:.*]] = cmpi "sle", %[[idx1]], %[[c8]] : index
+  // are both conds true
+  //      CHECK: %[[cond:.*]] = and %[[cmp0]], %[[cmp1]] : i1
+  //      CHECK: %[[ifres:.*]]:3 = scf.if %[[cond]] -> (memref<?x8xf32>, index, index) {
+  //               inBounds, just yield %A
+  //      CHECK:   scf.yield %[[A]], %[[i]], %[[j]] : memref<?x8xf32>, index, index
+  //      CHECK: } else {
+  //               slow path, fill tmp alloc and yield a memref_casted version of it
+  //      CHECK:   %[[slow:.*]] = vector.transfer_read %[[A]][%[[i]], %[[j]]], %cst :
+  // CHECK-SAME:     memref<?x8xf32>, vector<4x8xf32>
+  //      CHECK:   %[[cast_alloc:.*]] = vector.type_cast %[[alloc]] :
+  // CHECK-SAME:     memref<4x8xf32> to memref<vector<4x8xf32>>
+  //      CHECK:   store %[[slow]], %[[cast_alloc]][] : memref<vector<4x8xf32>>
+  //      CHECK:   %[[yielded:.*]] = memref_cast %[[alloc]] :
+  // CHECK-SAME:     memref<4x8xf32> to memref<?x8xf32>
+  //      CHECK:   scf.yield %[[yielded]], %[[c0]], %[[c0]] :
+  // CHECK-SAME:     memref<?x8xf32>, index, index
+  //      CHECK: }
+  //      CHECK: %[[res:.*]] = vector.transfer_read %[[ifres]]#0[%[[ifres]]#1, %[[ifres]]#2], %[[cst]]
+  // CHECK_SAME:   {masked = [false, false]} : memref<?x8xf32>, vector<4x8xf32>
+  %1 = vector.transfer_read %A[%i, %j], %f0 : memref<?x8xf32>, vector<4x8xf32>
+
+  // CHECK: return %[[res]] : vector<4x8xf32>
+  return %1: vector<4x8xf32>
+}
+
+// CHECK-LABEL: split_vector_transfer_read_strided_2d(
+//  CHECK-SAME: %[[A:[a-zA-Z0-9]*]]: memref
+//  CHECK-SAME: %[[i:[a-zA-Z0-9]*]]: index
+//  CHECK-SAME: %[[j:[a-zA-Z0-9]*]]: index
+func @split_vector_transfer_read_strided_2d(
+    %A: memref<7x8xf32, offset:?, strides:[?, 1]>,
+    %i: index, %j: index) -> vector<4x8xf32> {
+  %c0 = constant 0 : index
+  %f0 = constant 0.0 : f32
+
+  //  CHECK-DAG: %[[c0:.*]] = constant 0 : index
+  //  CHECK-DAG: %[[c7:.*]] = constant 7 : index
+  //  CHECK-DAG: %[[c8:.*]] = constant 8 : index
+  //  CHECK-DAG: %[[cst:.*]] = constant 0.000000e+00 : f32
+  // alloca for boundary full tile
+  //      CHECK: %[[alloc:.*]] = alloca() {alignment = 32 : i64} : memref<4x8xf32>
+  // %i + 4 <= dim(%A, 0)
+  //      CHECK: %[[idx0:.*]] = affine.apply #[[$map_p4]]()[%[[i]]]
+  //      CHECK: %[[cmp0:.*]] = cmpi "sle", %[[idx0]], %[[c7]] : index
+  // %j + 8 <= dim(%A, 1)
+  //      CHECK: %[[idx1:.*]] = affine.apply #[[$map_p8]]()[%[[j]]]
+  //      CHECK: %[[cmp1:.*]] = cmpi "sle", %[[idx1]], %[[c8]] : index
+  // are both conds true
+  //      CHECK: %[[cond:.*]] = and %[[cmp0]], %[[cmp1]] : i1
+  //      CHECK: %[[ifres:.*]]:3 = scf.if %[[cond]] -> (memref<?x8xf32, #[[$map_2d_stride_1]]>, index, index) {
+  //               inBounds but not cast-compatible: yield a memref_casted form of %A
+  //      CHECK:   %[[casted:.*]] = memref_cast %arg0 :
+  // CHECK-SAME:     memref<7x8xf32, #[[$map_2d_stride_1]]> to memref<?x8xf32, #[[$map_2d_stride_1]]>
+  //      CHECK:   scf.yield %[[casted]], %[[i]], %[[j]] :
+  // CHECK-SAME:     memref<?x8xf32, #[[$map_2d_stride_1]]>, index, index
+  //      CHECK: } else {
+  //               slow path, fill tmp alloc and yield a memref_casted version of it
+  //      CHECK:   %[[slow:.*]] = vector.transfer_read %[[A]][%[[i]], %[[j]]], %cst :
+  // CHECK-SAME:     memref<7x8xf32, #[[$map_2d_stride_1]]>, vector<4x8xf32>
+  //      CHECK:   %[[cast_alloc:.*]] = vector.type_cast %[[alloc]] :
+  // CHECK-SAME:     memref<4x8xf32> to memref<vector<4x8xf32>>
+  //      CHECK:   store %[[slow]], %[[cast_alloc]][] :
+  // CHECK-SAME:     memref<vector<4x8xf32>>
+  //      CHECK:   %[[yielded:.*]] = memref_cast %[[alloc]] :
+  // CHECK-SAME:     memref<4x8xf32> to memref<?x8xf32, #[[$map_2d_stride_1]]>
+  //      CHECK:   scf.yield %[[yielded]], %[[c0]], %[[c0]] :
+  // CHECK-SAME:     memref<?x8xf32, #[[$map_2d_stride_1]]>, index, index
+  //      CHECK: }
+  //      CHECK: %[[res:.*]] = vector.transfer_read {{.*}} {masked = [false, false]} :
+  // CHECK-SAME:   memref<?x8xf32, #[[$map_2d_stride_1]]>, vector<4x8xf32>
+  %1 = vector.transfer_read %A[%i, %j], %f0 :
+    memref<7x8xf32, offset:?, strides:[?, 1]>, vector<4x8xf32>
+
+  // CHECK: return %[[res]] : vector<4x8xf32>
+  return %1 : vector<4x8xf32>
+}

mlir/test/lib/Transforms/TestVectorTransforms.cpp

void runOnFunction() override {
     patterns.insert<UnrollVectorPattern<vector::ContractionOp>>(
         ArrayRef<int64_t>{2, 2, 2}, ctx);
     populateVectorToVectorCanonicalizationPatterns(patterns, ctx);
     populateVectorToVectorTransformationPatterns(patterns, ctx);
     applyPatternsAndFoldGreedily(getFunction(), patterns);
   }
 };
 
+struct TestVectorTransferFullPartialSplitPatterns
+    : public PassWrapper<TestVectorTransferFullPartialSplitPatterns,
+                         FunctionPass> {
+  void runOnFunction() override {
+    MLIRContext *ctx = &getContext();
+    OwningRewritePatternList patterns;
+    patterns.insert<VectorTransferFullPartialRewriter>(ctx);
+    applyPatternsAndFoldGreedily(getFunction(), patterns);
+  }
+};
+
 } // end anonymous namespace
 
 namespace mlir {
 void registerTestVectorConversions() {
   PassRegistration<TestVectorToVectorConversion> vectorToVectorPass(
       "test-vector-to-vector-conversion",
       "Test conversion patterns between ops in the vector dialect");
 
   PassRegistration<TestVectorSlicesConversion> slicesPass(
       "test-vector-slices-conversion",
       "Test conversion patterns that lower slices ops in the vector dialect");
 
   PassRegistration<TestVectorContractionConversion> contractionPass(
       "test-vector-contraction-conversion",
       "Test conversion patterns that lower contract ops in the vector dialect");
 
   PassRegistration<TestVectorUnrollingPatterns> contractionUnrollingPass(
       "test-vector-unrolling-patterns",
       "Test conversion patterns to unroll contract ops in the vector dialect");
+
+  PassRegistration<TestVectorTransferFullPartialSplitPatterns>
+      vectorTransformFullPartialPass("test-vector-transfer-full-partial-split",
+                                     "Test conversion patterns to split "
+                                     "transfer ops via scf.if + linalg ops");
 }
 } // namespace mlir