[Mlir-commits] [mlir] [mlir][core|ptr] Add `PtrLikeTypeInterface` and casting ops to the `ptr` dialect (PR #137469)

[Fabian Mora]

================
@@ -41,6 +41,54 @@ void PtrDialect::initialize() {
       >();
 }
 
+//===----------------------------------------------------------------------===//
+// FromPtrOp
+//===----------------------------------------------------------------------===//
+
+OpFoldResult FromPtrOp::fold(FoldAdaptor adaptor) {
+  // Fold the pattern:
+  // %ptr = ptr.to_ptr %v : type -> ptr
+  // (%mda = ptr.get_metadata %v : type)?
+  // %val = ptr.from_ptr %ptr (metadata %mda)? : ptr -> type
+  // To:
+  // %val -> %v
+  auto toPtr = dyn_cast_or_null<ToPtrOp>(getPtr().getDefiningOp());
+  // Cannot fold if it's not a `to_ptr` op or the initial and final types are
+  // different.
----------------
fabianmcg wrote:

So there are 2 types of chains:
1. `from_ptr -> to_ptr -> from_ptr -> .... to_ptr` can always be simplified, because getting the ptr is always loss-less.
2. `to_ptr -> from_ptr -> ... from_ptr` is not always guaranteed to be a lossless conversion. The only case where it's guaranteed that it can be folded safely, is when we know the metadata will match.


The first case is handle by the `to_ptr` folder, while the second with the `from_ptr` folder.

https://github.com/llvm/llvm-project/pull/137469