Add leading scalable dim test

Author: MacDue

mlir/test/Dialect/Vector/vector-bitcast-lowering-transforms.mlir

@@ -62,6 +62,17 @@ func.func @vector_bitcast_2d_trailing_scalable_dim(%arg0: vector<2x[2]xi64>) ->
 // CHECK:         %[[B2:.+]] = vector.bitcast %[[V2]] : vector<[2]xi64> to vector<[4]xi32>
 // CHECK:         %[[R2:.+]] = vector.insert %[[B2]], %[[R1]] [1] : vector<[4]xi32> into vector<2x[4]xi32>
 // CHECK:         return %[[R2]] : vector<2x[4]xi32>
+
+func.func @vector_bitcast_2d_leading_scalable_dim(%arg0: vector<[2]x2xi64>) -> vector<[2]x4xi32>
+{
+  %0 = vector.bitcast %arg0 : vector<[2]x2xi64> to vector<[2]x4xi32>
+  return %0 : vector<[2]x4xi32>
+}
+// CHECK-LABEL: func.func @vector_bitcast_2d_leading_scalable_dim
+// CHECK-SAME:    %[[IN:[a-zA-Z0-9]+]]
+// CHECK:         %[[RES:.+]] = vector.bitcast %[[IN]] : vector<[2]x2xi64> to vector<[2]x4xi32>
+// CHECK:         return %[[RES]] : vector<[2]x4xi32>
+
 module attributes {transform.with_named_sequence} {
   transform.named_sequence @__transform_main(%module_op: !transform.any_op {transform.readonly}) {
     %f = transform.structured.match ops{["func.func"]} in %module_op