[mlir][vector] Update tests for collapse 3/n (nfc)

The main goal of this PR (and subsequent PRs), is to add more tests with
scalable vectors to:
  * vector-transfer-collapse-inner-most-dims.mlir

There's quite a few cases to consider, hence this is split into multiple
PRs. In this PR, the very first test for `vector.transfer_write` is
complemented with all the possible combinations:
  * scalable (rather than fixed) unit trailing dim,
  * dynamic (rather than static) trailing dim in the source memref.

To this end, the following tests:
  * `@leading_scalable_dimension_transfer_write`
    `@trailing_scalable_one_dim_transfer_write`

are replaced with:
  * `@drop_two_inner_most_dim_scalable_inner_dim` and
    `@negative_scalable_unit_dim`,

respectively. In addition:
  * "_for_transfer_write" is removed from function names (to reduce
    noise).

This is a follow-up for: #94490, #94604

NOTE: This PR is limited to tests for `vector.transfer_write`.

Author: banach-space

mlir/test/Dialect/Vector/vector-transfer-collapse-inner-most-dims.mlir

@@ -254,14 +254,14 @@ func.func @negative_non_unit_inner_memref_dim(%arg0: memref<4x8xf32>) -> vector<
 // 2. vector.transfer_write
 //-----------------------------------------------------------------------------
 
-func.func @drop_two_inner_most_dim_for_transfer_write(%arg0: memref<1x512x16x1x1xf32>, %arg1: vector<1x16x16x1x1xf32>, %arg2: index) {
+func.func @drop_two_inner_most_dim(%arg0: memref<1x512x16x1x1xf32>, %arg1: vector<1x16x16x1x1xf32>, %arg2: index) {
   %c0 = arith.constant 0 : index
   vector.transfer_write %arg1, %arg0[%c0, %arg2, %c0, %c0, %c0]
     {in_bounds = [true, true, true, true, true]}
     : vector<1x16x16x1x1xf32>, memref<1x512x16x1x1xf32>
   return
 }
-// CHECK:      func.func @drop_two_inner_most_dim_for_transfer_write
+// CHECK:      func.func @drop_two_inner_most_dim
 // CHECK-SAME:   %[[DEST:[a-zA-Z0-9]+]]
 // CHECK-SAME:   %[[VEC:[a-zA-Z0-9]+]]
 // CHECK-SAME:   %[[IDX:[a-zA-Z0-9]+]]
@@ -272,16 +272,67 @@ func.func @drop_two_inner_most_dim_for_transfer_write(%arg0: memref<1x512x16x1x1
 // CHECK:        vector.transfer_write %[[CAST]], %[[SUBVIEW]]
 // CHECK-SAME:     [%[[C0]], %[[IDX]], %[[C0]]]
 
+// Same as the top example within this split, but with the inner vector
+// dim scalable. Note that this example only makes sense when "16 = [16]" (i.e.
+// vscale = 1). This is assumed (implicitly) via the `in_bounds` attribute.
+
+func.func @drop_two_inner_most_dim_scalable_inner_dim(%arg0: memref<1x512x16x1x1xf32>, %arg1: vector<1x16x[16]x1x1xf32>, %arg2: index) {
+  %c0 = arith.constant 0 : index
+  vector.transfer_write %arg1, %arg0[%c0, %arg2, %c0, %c0, %c0]
+    {in_bounds = [true, true, true, true, true]}
+    : vector<1x16x[16]x1x1xf32>, memref<1x512x16x1x1xf32>
+  return
+}
+// CHECK:      func.func @drop_two_inner_most_dim_scalable_inner_dim
+// CHECK-SAME:   %[[DEST:[a-zA-Z0-9]+]]
+// CHECK-SAME:   %[[VEC:[a-zA-Z0-9]+]]
+// CHECK-SAME:   %[[IDX:[a-zA-Z0-9]+]]
+// CHECK-DAG:    %[[C0:.+]] = arith.constant 0 : index
+// CHECK:        %[[SUBVIEW:.+]] = memref.subview %[[DEST]]
+// CHECK-SAME:     memref<1x512x16x1x1xf32> to memref<1x512x16xf32, strided<[8192, 16, 1]>>
+// CHECK:        %[[CAST:.+]] = vector.shape_cast %[[VEC]] : vector<1x16x[16]x1x1xf32> to vector<1x16x[16]xf32>
+// CHECK:        vector.transfer_write %[[CAST]], %[[SUBVIEW]]
+// CHECK-SAME:     [%[[C0]], %[[IDX]], %[[C0]]]
+
+// Same as the top example within this split, but the trailing unit dim was
+// replaced with a dyn dim - not supported
+
+func.func @negative_non_unit_trailing_dim(%arg0: memref<1x512x16x1x?xf32>, %arg1: vector<1x16x16x1x1xf32>, %arg2: index) {
+  %c0 = arith.constant 0 : index
+  vector.transfer_write %arg1, %arg0[%c0, %arg2, %c0, %c0, %c0]
+    {in_bounds = [true, true, true, true, true]}
+    : vector<1x16x16x1x1xf32>, memref<1x512x16x1x?xf32>
+  return
+}
+// CHECK:      func.func @negative_non_unit_trailing_dim
+// CHECK-NOT: memref.subview
+// CHECK-NOT: vector.shape_cast
+
+// Same as the top example within this split, but with a scalable unit dim in
+// the output vector - not supported
+
+func.func @negative_scalable_unit_dim(%arg0: memref<1x512x16x1x1xf32>, %arg1: vector<1x16x16x1x[1]xf32>, %arg2: index) {
+  %c0 = arith.constant 0 : index
+  vector.transfer_write %arg1, %arg0[%c0, %arg2, %c0, %c0, %c0]
+    {in_bounds = [true, true, true, true, true]}
+    : vector<1x16x16x1x[1]xf32>, memref<1x512x16x1x1xf32>
+  return
+}
+
+// CHECK:     func.func @negative_scalable_unit_dim
+// CHECK-NOT: memref.subview
+// CHECK-NOT: vector.shape_cast
+
 // -----
 
-func.func @drop_inner_most_dim_for_transfer_write(%arg0: memref<1x512x16x1xf32, strided<[8192, 16, 1, 1], offset: ?>>, %arg1: vector<1x16x16x1xf32>, %arg2: index) {
+func.func @drop_inner_most_dim(%arg0: memref<1x512x16x1xf32, strided<[8192, 16, 1, 1], offset: ?>>, %arg1: vector<1x16x16x1xf32>, %arg2: index) {
   %c0 = arith.constant 0 : index
   vector.transfer_write %arg1, %arg0[%c0, %arg2, %c0, %c0]
     {in_bounds = [true, true, true, true]}
     : vector<1x16x16x1xf32>, memref<1x512x16x1xf32, strided<[8192, 16, 1, 1], offset: ?>>
   return
 }
-// CHECK:      func.func @drop_inner_most_dim_for_transfer_write
+// CHECK:      func.func @drop_inner_most_dim
 // CHECK-SAME:   %[[DEST:[a-zA-Z0-9]+]]
 // CHECK-SAME:   %[[VEC:[a-zA-Z0-9]+]]
 // CHECK-SAME:   %[[IDX:[a-zA-Z0-9]+]]
@@ -294,14 +345,14 @@ func.func @drop_inner_most_dim_for_transfer_write(%arg0: memref<1x512x16x1xf32,
 
 // -----
 
-func.func @outer_dyn_drop_inner_most_dim_for_transfer_write(%arg0: memref<?x512x16x1xf32, strided<[8192, 16, 1, 1], offset: ?>>, %arg1: vector<1x16x16x1xf32>, %arg2: index) {
+func.func @outer_dyn_drop_inner_most_dim(%arg0: memref<?x512x16x1xf32, strided<[8192, 16, 1, 1], offset: ?>>, %arg1: vector<1x16x16x1xf32>, %arg2: index) {
   %c0 = arith.constant 0 : index
   vector.transfer_write %arg1, %arg0[%arg2, %c0, %c0, %c0]
     {in_bounds = [true, true, true, true]}
     : vector<1x16x16x1xf32>, memref<?x512x16x1xf32, strided<[8192, 16, 1, 1], offset: ?>>
   return
 }
-// CHECK:      func.func @outer_dyn_drop_inner_most_dim_for_transfer_write
+// CHECK:      func.func @outer_dyn_drop_inner_most_dim
 // CHECK-SAME:   %[[DEST:[a-zA-Z0-9]+]]
 // CHECK-SAME:   %[[VEC:[a-zA-Z0-9]+]]
 // CHECK-SAME:   %[[IDX:[a-zA-Z0-9]+]]
@@ -325,30 +376,3 @@ func.func @non_unit_strides(%arg0: memref<512x16x1xf32, strided<[8192, 16, 4], o
 // The inner most unit dims can not be dropped if the strides are not ones.
 // CHECK:     func.func @non_unit_strides
 // CHECK-NOT:   memref.subview
-
-// -----
-
-func.func @leading_scalable_dimension_transfer_write(%dest : memref<24x1xf32>, %vec: vector<[4]x1xf32>) {
-  %c0 = arith.constant 0 : index
-  vector.transfer_write %vec, %dest[%c0, %c0] {in_bounds = [true, true]} : vector<[4]x1xf32>,  memref<24x1xf32>
-  return
-}
-// CHECK:      func.func @leading_scalable_dimension_transfer_write
-// CHECK-SAME:   %[[DEST:[a-zA-Z0-9]+]]
-// CHECK-SAME:   %[[VEC:[a-zA-Z0-9]+]]
-// CHECK:        %[[SUBVIEW:.+]] = memref.subview %[[DEST]][0, 0] [24, 1] [1, 1] : memref<24x1xf32> to memref<24xf32, strided<[1]>>
-// CHECK:        %[[CAST:.+]] = vector.shape_cast %[[VEC]] : vector<[4]x1xf32> to vector<[4]xf32>
-// CHECK:        vector.transfer_write %[[CAST]], %[[SUBVIEW]]{{.*}} {in_bounds = [true]} : vector<[4]xf32>, memref<24xf32, strided<[1]>>
-
-// -----
-
-// Negative test: [1] (scalable 1) is _not_ a unit dimension.
-func.func @trailing_scalable_one_dim_transfer_write(%dest : memref<24x1xf32>, %vec: vector<4x[1]xf32>, %index: index) {
-  %c0 = arith.constant 0 : index
-  vector.transfer_write %vec, %dest[%index, %c0] {in_bounds = [true, true]} : vector<4x[1]xf32>,  memref<24x1xf32>
-  return
-}
-// CHECK:      func.func @trailing_scalable_one_dim_transfer_write
-// CHECK-NOT:    vector.shape_cast
-// CHECK:        vector.transfer_write {{.*}} : vector<4x[1]xf32>,  memref<24x1xf32>
-// CHECK-NOT:    vector.shape_cast