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

[Mehdi Amini]

================
@@ -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.
+  if (!toPtr || toPtr.getPtr().getType() != getType())
+    return nullptr;
+  Value md = getMetadata();
+  if (!md)
+    return toPtr.getPtr();
----------------
joker-eph wrote:

I'm not sure about this condition.
It seems to imply that all the metadata are statically encoded in the type. Couldn't there be a type where some runtime metadata are default initialized? In which case round-tripping to a `ptr` would be erasing them and folding would undo this erasing.

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