[mlir][vector] Refactor vector-transfer-flatten.mlir (nfc) (2/n)

The main goal of this and subsequent PRs is to unify and categorize
tests in:
  * vector-transfer-flatten.mlir
This should make it easier to identify the edge cases being tested (and
how they differ), remove duplicates and to add tests for scalable
vectors.

The main contributions of this PR:
1. `@transfer_{read|write}_dims_mismatch_non_contiguous` and
   `@transfer_read_flattenable_negative` duplicated
   `@transfer_{read|write}_dims_mismatch_non_contiguous_slice`. Both
   tests are deleted
   (`@transfer_{read|write}_dims_mismatch_non_contiguous_slice` is
   preserved).

2. `@transfer_read_flattenable_negative2` is replaced with
   `@transfer_read_non_contiguous_src` and
   `@transfer_write_non_contiguous_src` (i.e. a dedicated test for
   xfer_read and xfer_read with more descriptive func names)

Depends on #95743.

**Only review the top commit.**

Author: banach-space

mlir/test/Dialect/Vector/vector-transfer-flatten.mlir

@@ -131,25 +131,6 @@ func.func @transfer_read_dims_mismatch_non_contiguous_non_zero_indices(
 
 // -----
 
-func.func @transfer_read_dims_mismatch_non_contiguous(
-    %arg : memref<5x4x3x2xi8, strided<[24, 6, 2, 1], offset: ?>>) -> vector<2x1x2x2xi8> {
-
-  %c0 = arith.constant 0 : index
-  %cst = arith.constant 0 : i8
-  %v = vector.transfer_read %arg[%c0, %c0, %c0, %c0], %cst :
-    memref<5x4x3x2xi8, strided<[24, 6, 2, 1], offset: ?>>, vector<2x1x2x2xi8>
-  return %v : vector<2x1x2x2xi8>
-}
-
-// CHECK-LABEL: func.func @transfer_read_dims_mismatch_non_contiguous
-// CHECK-NOT: memref.collapse_shape
-// CHECK-NOT: vector.shape_cast
-
-// CHECK-128B-LABEL: func @transfer_read_dims_mismatch_non_contiguous(
-//   CHECK-128B-NOT:   memref.collapse_shape
-
-// -----
-
 // The input memref has a dynamic trailing shape and hence is not flattened.
 // TODO: This case could be supported via memref.dim
 
@@ -214,6 +195,28 @@ func.func @transfer_read_0d(
 
 // -----
 
+// Strides make the input memref non-contiguous, hence non-flattenable.
+
+func.func @transfer_read_non_contiguous_src(
+    %arg : memref<5x4x3x2xi8, strided<[24, 8, 2, 1], offset: ?>>) -> vector<5x4x3x2xi8> {
+
+  %c0 = arith.constant 0 : index
+  %cst = arith.constant 0 : i8
+  %v = vector.transfer_read %arg[%c0, %c0, %c0, %c0], %cst :
+    memref<5x4x3x2xi8, strided<[24, 8, 2, 1], offset: ?>>, vector<5x4x3x2xi8>
+  return %v : vector<5x4x3x2xi8>
+}
+
+// CHECK-LABEL: func.func @transfer_read_non_contiguous_src
+// CHECK-NOT: memref.collapse_shape
+// CHECK-NOT: vector.shape_cast
+
+// CHECK-128B-LABEL: func @transfer_read_non_contiguous_src
+//   CHECK-128B-NOT:   memref.collapse_shape
+//   CHECK-128B-NOT:   vector.shape_cast
+
+// -----
+
 ///----------------------------------------------------------------------------------------
 /// vector.transfer_write
 /// [Pattern: FlattenContiguousRowMajorTransferWritePattern]
@@ -342,25 +345,6 @@ func.func @transfer_write_dims_mismatch_non_contiguous_non_zero_indices(
 
 // -----
 
-func.func @transfer_write_dims_mismatch_non_contiguous(
-    %arg : memref<5x4x3x2xi8, strided<[24, 6, 2, 1], offset: ?>>,
-    %vec : vector<2x1x2x2xi8>) {
-
-  %c0 = arith.constant 0 : index
-  vector.transfer_write %vec, %arg [%c0, %c0, %c0, %c0] :
-    vector<2x1x2x2xi8>, memref<5x4x3x2xi8, strided<[24, 6, 2, 1], offset: ?>>
-  return
-}
-
-// CHECK-LABEL: func.func @transfer_write_dims_mismatch_non_contiguous
-// CHECK-NOT: memref.collapse_shape
-// CHECK-NOT: vector.shape_cast
-
-// CHECK-128B-LABEL: func @transfer_write_dims_mismatch_non_contiguous(
-//   CHECK-128B-NOT:   memref.collapse_shape
-
-// -----
-
 // The input memref has a dynamic trailing shape and hence is not flattened.
 // TODO: This case could be supported via memref.dim
 
@@ -427,6 +411,28 @@ func.func @transfer_write_0d(
 
 // -----
 
+// The strides make the input memref non-contiguous, hence non-flattenable.
+
+func.func @transfer_write_non_contiguous_src(
+    %arg : memref<5x4x3x2xi8, strided<[24, 8, 2, 1], offset: ?>>,
+    %vec : vector<5x4x3x2xi8>) {
+
+  %c0 = arith.constant 0 : index
+  vector.transfer_write %vec, %arg[%c0, %c0, %c0, %c0] :
+   vector<5x4x3x2xi8>, memref<5x4x3x2xi8, strided<[24, 8, 2, 1], offset: ?>>
+  return
+}
+
+// CHECK-LABEL: func.func @transfer_write_non_contiguous_src
+// CHECK-NOT: memref.collapse_shape
+// CHECK-NOT: vector.shape_cast
+
+// CHECK-128B-LABEL: func @transfer_write_non_contiguous_src
+//   CHECK-128B-NOT:   memref.collapse_shape
+//   CHECK-128B-NOT:   vector.shape_cast
+
+// -----
+
 ///----------------------------------------------------------------------------------------
 /// TODO: Categorize + re-format
 ///----------------------------------------------------------------------------------------
@@ -478,40 +484,6 @@ func.func @transfer_write_flattenable_with_dynamic_dims_and_indices(%vec : vecto
 
 // -----
 
-func.func @transfer_read_flattenable_negative(
-      %arg : memref<5x4x3x2xi8, strided<[24, 6, 2, 1], offset: ?>>) -> vector<2x2x2x2xi8> {
-    %c0 = arith.constant 0 : index
-    %cst = arith.constant 0 : i8
-    %v = vector.transfer_read %arg[%c0, %c0, %c0, %c0], %cst :
-      memref<5x4x3x2xi8, strided<[24, 6, 2, 1], offset: ?>>, vector<2x2x2x2xi8>
-    return %v : vector<2x2x2x2xi8>
-}
-
-// CHECK-LABEL: func @transfer_read_flattenable_negative
-//       CHECK:   vector.transfer_read {{.*}} vector<2x2x2x2xi8>
-
-// CHECK-128B-LABEL: func @transfer_read_flattenable_negative(
-//   CHECK-128B-NOT:   memref.collapse_shape
-
-// -----
-
-func.func @transfer_read_flattenable_negative2(
-      %arg : memref<5x4x3x2xi8, strided<[24, 8, 2, 1], offset: ?>>) -> vector<5x4x3x2xi8> {
-    %c0 = arith.constant 0 : index
-    %cst = arith.constant 0 : i8
-    %v = vector.transfer_read %arg[%c0, %c0, %c0, %c0], %cst :
-      memref<5x4x3x2xi8, strided<[24, 8, 2, 1], offset: ?>>, vector<5x4x3x2xi8>
-    return %v : vector<5x4x3x2xi8>
-}
-
-// CHECK-LABEL: func @transfer_read_flattenable_negative2
-//       CHECK:   vector.transfer_read {{.*}} vector<5x4x3x2xi8>
-
-// CHECK-128B-LABEL: func @transfer_read_flattenable_negative2(
-//   CHECK-128B-NOT:   memref.collapse_shape
-
-// -----
-
 func.func @fold_unit_dim_add_basic(%arg0 : vector<1x8xi32>) -> vector<1x8xi32> {
    %add = arith.addi %arg0, %arg0 : vector<1x8xi32>
    return %add : vector<1x8xi32>