[mlir][vector] Update the folder for vector.{insert|extract} (#136579)

This is a minor follow-up to #135498. It ensures that operations like
the following are not treated as out-of-bounds accesses and can be
folded correctly (*):

```mlir
  %c_neg_1 = arith.constant -1 : index
  %0 = vector.insert %value_to_store, %dest[%c_neg_1] : vector<5xf32> into vector<4x5xf32>
  %1 = vector.extract %src[%c_neg_1, 0] : f32 from vector<4x5xf32>
```

In addition to adding tests for the case above, this PR also relocates
the tests from #135498 to be alongside existing tests for the
`vector.{insert|extract}` folder, and reformats them to follow:
  * https://mlir.llvm.org/getting_started/TestingGuide/

For example:
  * The "no_fold" prefix is now used to label negative tests.
  * Redundant check lines have been removed (e.g., CHECK: vector.insert
    is sufficient to verify that folding did not occur).

(*) As per https://mlir.llvm.org/docs/Dialects/Vector/#vectorinsert-vectorinsertop,
these are poison values.

Author: banach-space

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

@@ -2045,8 +2045,9 @@ static Value extractInsertFoldConstantOp(OpType op, AdaptorType adaptor,
     Value position = dynamicPosition[index++];
     if (auto attr = mlir::dyn_cast_if_present<IntegerAttr>(positionAttr)) {
       int64_t value = attr.getInt();
-      // Do not fold if the value is out of bounds.
-      if (value >= 0 && value < vectorShape[i]) {
+      // Do not fold if the value is out of bounds (-1 signifies a poison
+      // value rather than OOB index).
+      if (value >= -1 && value < vectorShape[i]) {
         staticPosition[i] = attr.getInt();
         opChange = true;
         continue;

mlir/test/Dialect/Vector/canonicalize.mlir

@@ -165,6 +165,33 @@ func.func @extract_scalar_poison_idx(%a: vector<4x5xf32>) -> f32 {
   return %0 : f32
 }
 
+// -----
+
+// Similar to the test above, but the index is not a static constant.
+
+// CHECK-LABEL: @extract_scalar_poison_idx_non_cst
+func.func @extract_scalar_poison_idx_non_cst(%a: vector<4x5xf32>) -> f32 {
+  // CHECK-NEXT: %[[UB:.*]] = ub.poison : f32
+  //  CHECK-NOT: vector.extract
+  // CHECK-NEXT: return %[[UB]] : f32
+  %c_neg_1 = arith.constant -1 : index
+  %0 = vector.extract %a[%c_neg_1, 0] : f32 from vector<4x5xf32>
+  return %0 : f32
+}
+
+// -----
+
+// Similar to test above, but now the index is out-of-bounds.
+
+// CHECK-LABEL: @no_fold_extract_scalar_oob_idx
+func.func @no_fold_extract_scalar_oob_idx(%a: vector<4x5xf32>) -> f32 {
+  //  CHECK: vector.extract
+  %c_neg_2 = arith.constant -2 : index
+  %0 = vector.extract %a[%c_neg_2, 0] : f32 from vector<4x5xf32>
+  return %0 : f32
+}
+
+
 // -----
 
 // CHECK-LABEL: @extract_vector_poison_idx
@@ -3062,6 +3089,34 @@ func.func @insert_vector_poison_idx(%a: vector<4x5xf32>, %b: vector<5xf32>)
 
 // -----
 
+// Similar to the test above, but the index is not a static constant.
+
+// CHECK-LABEL: @insert_vector_poison_idx_non_cst
+func.func @insert_vector_poison_idx_non_cst(%a: vector<4x5xf32>, %b: vector<5xf32>)
+    -> vector<4x5xf32> {
+  // CHECK-NEXT: %[[UB:.*]] = ub.poison : vector<4x5xf32>
+  //  CHECK-NOT: vector.insert
+  // CHECK-NEXT: return %[[UB]] : vector<4x5xf32>
+  %c_neg_1 = arith.constant -1 : index
+  %0 = vector.insert %b, %a[%c_neg_1] : vector<5xf32> into vector<4x5xf32>
+  return %0 : vector<4x5xf32>
+}
+
+// -----
+
+// Similar to test above, but now the index is out-of-bounds.
+
+// CHECK-LABEL: @no_fold_insert_scalar_idx_oob
+func.func @no_fold_insert_scalar_idx_oob(%a: vector<4x5xf32>, %b: vector<5xf32>)
+    -> vector<4x5xf32> {
+  //  CHECK: vector.insert
+  %c_neg_2 = arith.constant -2 : index
+  %0 = vector.insert %b, %a[%c_neg_2] : vector<5xf32> into vector<4x5xf32>
+  return %0 : vector<4x5xf32>
+}
+
+// -----
+
 // CHECK-LABEL: @insert_multiple_poison_idx
 func.func @insert_multiple_poison_idx(%a: vector<4x5x8xf32>, %b: vector<8xf32>)
     -> vector<4x5x8xf32> {
@@ -3311,41 +3366,3 @@ func.func @fold_insert_constant_indices(%arg : vector<4x1xi32>) -> vector<4x1xi3
   %res = vector.insert %1, %arg[%0, %0] : i32 into vector<4x1xi32>
   return %res : vector<4x1xi32>
 }
-
-// -----
-
-// Check that out of bounds indices are not folded for vector.insert.
-
-// CHECK-LABEL: @fold_insert_oob
-//  CHECK-SAME:   %[[ARG:.*]]: vector<4x1x2xi32>) -> vector<4x1x2xi32> {
-//       CHECK:   %[[OOB1:.*]] = arith.constant -2 : index
-//       CHECK:   %[[OOB2:.*]] = arith.constant 2 : index
-//       CHECK:   %[[VAL:.*]] = arith.constant 1 : i32
-//       CHECK:   %[[RES:.*]] = vector.insert %[[VAL]], %[[ARG]] [0, %[[OOB1]], %[[OOB2]]] : i32 into vector<4x1x2xi32>
-//       CHECK:   return %[[RES]] : vector<4x1x2xi32>
-func.func @fold_insert_oob(%arg : vector<4x1x2xi32>) -> vector<4x1x2xi32> {
-  %c0 = arith.constant 0 : index
-  %c-2 = arith.constant -2 : index
-  %c2 = arith.constant 2 : index
-  %c1 = arith.constant 1 : i32
-  %res = vector.insert %c1, %arg[%c0, %c-2, %c2] : i32 into vector<4x1x2xi32>
-  return %res : vector<4x1x2xi32>
-}
-
-// -----
-
-// Check that out of bounds indices are not folded for vector.extract.
-
-// CHECK-LABEL: @fold_extract_oob
-//  CHECK-SAME:   %[[ARG:.*]]: vector<4x1x2xi32>) -> i32 {
-//       CHECK:   %[[OOB1:.*]] = arith.constant -2 : index
-//       CHECK:   %[[OOB2:.*]] = arith.constant 2 : index
-//       CHECK:   %[[RES:.*]] = vector.extract %[[ARG]][0, %[[OOB1]], %[[OOB2]]] : i32 from vector<4x1x2xi32>
-//       CHECK:   return %[[RES]] : i32
-func.func @fold_extract_oob(%arg : vector<4x1x2xi32>) -> i32 {
-  %c0 = arith.constant 0 : index
-  %c-2 = arith.constant -2 : index
-  %c2 = arith.constant 2 : index
-  %res = vector.extract %arg[%c0, %c-2, %c2] : i32 from vector<4x1x2xi32>
-  return %res : i32
-}