simplifying tweaks

Author: newling

mlir/lib/Dialect/Vector/IR/VectorOps.cpp

@@ -6481,18 +6481,7 @@ struct TransposeToShapeCast final
   LogicalResult matchAndRewrite(vector::TransposeOp transpose,
                                 PatternRewriter &rewriter) const override {
 
-    // This folder does
-    //    shape_cast(transpose) -> shape_cast
-    // But another pattern, ConvertIllegalShapeCastOpsToTransposes, does
-    //    shape_cast -> shape_cast(transpose)
-    // i.e. the complete opposite. When paired, these 2 patterns can cause
-    // infinite cycles in pattern rewriting.
-    // ConvertIllegalShapeCastOpsToTransposes only matches on scalable
-    // vectors, so by disabling this folder for scalable vectors the
-    // cycle is avoided.
-    // TODO: Check if ConvertIllegalShapeCastOpsToTransposes is
-    // still needed. If it's not, then we can fold here.
-    if (!isOrderPreserving(transpose) || transpose.getType().isScalable()) {
+    if (!isOrderPreserving(transpose)) {
       return rewriter.notifyMatchFailure(
           transpose, "not order preserving, so not semantically a 'copy'");
     }

mlir/test/Dialect/Vector/canonicalize/vector-shape-cast.mlir

@@ -100,25 +100,21 @@ func.func @negative_transpose_to_shape_cast(%arg : vector<1x4x4x1xi8>) -> vector
 
 // -----
 
-// Currently the conversion shape_cast(transpose) -> shape_cast is disabled for
-// scalable vectors because of bad interaction with ConvertIllegalShapeCastOpsToTransposes
-// CHECK-LABEL: @negative_shape_cast_of_transpose_scalable
-//       CHECK:  vector.transpose
-//       CHECK:  vector.shape_cast
-func.func @negative_shape_cast_of_transpose_scalable(%arg : vector<[4]x1xi8>) -> vector<[4]xi8> {
+// CHECK-LABEL: @shape_cast_of_transpose_scalable
+//  CHECK-NEXT:  vector.shape_cast
+//  CHECK-NEXT:  return
+func.func @shape_cast_of_transpose_scalable(%arg : vector<[4]x1xi8>) -> vector<[4]xi8> {
   %0 = vector.transpose %arg, [1, 0] : vector<[4]x1xi8> to vector<1x[4]xi8>
   %1 = vector.shape_cast %0 : vector<1x[4]xi8> to vector<[4]xi8>
   return %1 : vector<[4]xi8>
 }
 
 // -----
 
-// The conversion transpose(shape_cast) -> shape_cast is currently disabled for scalable
-// vectors.
-// CHECK-LABEL: @negative_transpose_of_shape_cast_scalable
-//       CHECK: vector.shape_cast
-//       CHECK: vector.transpose
-func.func @negative_transpose_of_shape_cast_scalable(%arg : vector<[4]xi8>) -> vector<[4]x1xi8> {
+// CHECK-LABEL: @transpose_of_shape_cast_scalable
+//  CHECK-NEXT: vector.shape_cast
+//  CHECK-NEXT: return
+func.func @transpose_of_shape_cast_scalable(%arg : vector<[4]xi8>) -> vector<[4]x1xi8> {
   %0 = vector.shape_cast %arg : vector<[4]xi8> to vector<1x[4]xi8>
   %1 = vector.transpose %0, [1, 0] : vector<1x[4]xi8> to vector<[4]x1xi8>
   return %1 : vector<[4]x1xi8>