[mlir][tensor][NFC] Refactor common methods for bubbling extract_slice op (llvm#153675)

Exposes the `tensor.extract_slice` reshaping logic in
`BubbleUpExpandShapeThroughExtractSlice` and
`BubbleUpCollapseShapeThroughExtractSlice` through two corresponding
utility functions. These compute the offsets/sizes/strides of an extract
slice after either collapsing or expanding.

This should also make it easier to implement the two other bubbling
cases: (1) the `collapse_shape` is a consumer or (2) the `expand_shape`
is a consumer.

---------

Signed-off-by: Ian Wood <[email protected]>

Author: IanWood1

mlir/include/mlir/Dialect/Tensor/Transforms/Transforms.h

@@ -142,6 +142,32 @@ FailureOr<Value> buildIndependentOp(OpBuilder &b, tensor::PadOp padOp,
 FailureOr<Value> buildIndependentOp(OpBuilder &b, tensor::EmptyOp emptyOp,
                                     ValueRange independencies);
 
+/// Computes the offsets, sizes, and strides needed to build a collapsed
+/// `sliceOp`. The dimensions to collapse are specified by `reassociation`.
+///
+/// This fails when the specified collapse cannot be represented by a valid
+/// ExtractSliceOp.
+LogicalResult
+getCollapsedExtractSliceInfo(OpBuilder &b, tensor::ExtractSliceOp sliceOp,
+                             ArrayRef<ReassociationIndices> reassociation,
+                             SmallVectorImpl<OpFoldResult> &collapsedOffsets,
+                             SmallVectorImpl<OpFoldResult> &collapsedSizes,
+                             SmallVectorImpl<OpFoldResult> &collapsedStrides);
+
+/// Computes the offsets, sizes, and strides needed to build an expanded
+/// `sliceOp`. The dimensions to expand are specified by `reassociation` and
+/// `expandedShape`.
+///
+/// This fails when the specified expansion cannot be represented by a valid
+/// ExtractSliceOp.
+LogicalResult
+getExpandedExtractSliceInfo(OpBuilder &b, tensor::ExtractSliceOp sliceOp,
+                            ArrayRef<ReassociationIndices> reassociation,
+                            ArrayRef<int64_t> expandedShape,
+                            SmallVectorImpl<OpFoldResult> &expandedOffsets,
+                            SmallVectorImpl<OpFoldResult> &expandedSizes,
+                            SmallVectorImpl<OpFoldResult> &expandedStrides);
+
 } // namespace tensor
 } // namespace mlir