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

[Fabian Mora]

================
@@ -63,6 +64,54 @@ def Ptr_PtrType : Ptr_Type<"Ptr", "ptr", [
       return $_get(memorySpace.getContext(), memorySpace);
     }]>
   ];
+  let extraClassDeclaration = [{
+    // `PtrLikeTypeInterface` interface methods.
+    /// Returns `Type()` as this pointer type is opaque.
+    Type getElementType() const {
+      return Type();
+    }
+    /// Clones the pointer with specified memory space or returns failure
+    /// if an `elementType` was specified or if the memory space doesn't
+    /// implement `MemorySpaceAttrInterface`.
+    FailureOr<PtrLikeTypeInterface> clonePtrWith(Attribute memorySpace,
+      std::optional<Type> elementType) const {
+      if (elementType)
+        return failure();
+      if (auto ms = dyn_cast<MemorySpaceAttrInterface>(memorySpace))
+        return cast<PtrLikeTypeInterface>(get(ms));
+      return failure();
+    }
+    /// `!ptr.ptr` types are seen as ptr-like objects with no metadata.
+    bool hasPtrMetadata() const {
+      return false;
+    }
+  }];
+}
+
+def Ptr_PtrMetadata : Ptr_Type<"PtrMetadata", "ptr_metadata"> {
+  let summary = "Pointer metadata type";
+  let description = [{
+    The `ptr_metadata` type represents an opaque-view of the metadata associated
+    with a `ptr-like` object type.
+    It's an error to get a `ptr_metadata` using `ptr-like` type with no
+    metadata.
----------------
fabianmcg wrote:

Yes, `ptr_metadata` has a verifier:
```c++
LogicalResult
PtrMetadataType::verify(function_ref<InFlightDiagnostic()> emitError,
                        PtrLikeTypeInterface type) {
  if (!type.hasPtrMetadata())
    return emitError() << "the ptr-like type has no metadata";
  return success();
}
```
Therefore, things like `!ptr.ptr_metadata<i32>` will produce an error. If a remember correctly, in assert builds it also generates an assertion. I'll clarify the note. 

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