[Mlir-commits] [mlir] [memref] Support non-scalar copies in `reinterpret_cast` elision (PR #203873)

[Andrzej Warzyński]

================
@@ -29,171 +31,408 @@ using namespace mlir;
 
 namespace {
 
-/// Returns true if `rc` represents a scalar view (all sizes == 1)
-/// into a memref that has exactly one non-unit dimension located at
-/// either the first or last position (i.e. a "row" or "column").
-///
-/// Examples that return true:
-///
-///   // Row-major slice (last dim is non-unit)
-///   memref.reinterpret_cast %buff to offset: [%off],
-///     sizes: [1, 1, 1], strides: [1, 1, 1]
-///     : memref<1x1x8xi32> to memref<1x1x1xi32>
+//===----------------------------------------------------------------------===//
+// Copy Rewrite Helpers
+//===----------------------------------------------------------------------===//
+
+/// Non-unit reinterpret_cast result dimension and the source dimension it
+/// advances through.
+struct NonUnitDimAssocMapForRC {
+  unsigned resultDimPos;
+  unsigned sourceDimPos;
+};
+
+/// Copy-relevant information derived from a reinterpret_cast.
+struct AssocMapAndOffsetsForRC {
+  // Non-unit dimensions of the reinterpret_cast result.
+  SmallVector<NonUnitDimAssocMapForRC> assocMap;
+  // Delinearized offsets to in-bounds reinterpret_cast source indices.
+  // Optional since it is only supported for static offsets.
+  std::optional<SmallVector<int64_t>> delinearizedOffsets;
+};
+
+/// Records the reinterpret_cast result dimensions that span more than one
+/// element and maps each one to its corresponding source dimension.
----------------
banach-space wrote:

Could you document what it means to return `true` vs `false`?

https://github.com/llvm/llvm-project/pull/203873