address reviewer comments and rebase

Author: fabianmcg

mlir/lib/Dialect/Ptr/IR/PtrDialect.cpp

@@ -61,13 +61,15 @@ OpFoldResult FromPtrOp::fold(FoldAdaptor adaptor) {
     if (!toPtr || toPtr.getPtr().getType() != fromPtr.getType())
       return ptrLike;
     Value md = fromPtr.getMetadata();
-    // If there's no metadata in the op fold the op.
-    if (!md)
-      ptrLike = toPtr.getPtr();
-    // Fold if the metadata can be verified to be equal.
-    else if (auto mdOp = dyn_cast_or_null<GetMetadataOp>(md.getDefiningOp());
-             mdOp && mdOp.getPtr() == toPtr.getPtr())
+    // If the type has trivial metadata fold.
+    if (!fromPtr.getType().hasPtrMetadata()) {
       ptrLike = toPtr.getPtr();
+    } else if (md) {
+      // Fold if the metadata can be verified to be equal.
+      if (auto mdOp = dyn_cast_or_null<GetMetadataOp>(md.getDefiningOp());
+          mdOp && mdOp.getPtr() == toPtr.getPtr())
+        ptrLike = toPtr.getPtr();
+    }
     // Check for a sequence of casts.
     fromPtr = dyn_cast_or_null<FromPtrOp>(ptrLike ? ptrLike.getDefiningOp()
                                                   : nullptr);

mlir/test/Dialect/Ptr/canonicalize.mlir

@@ -28,12 +28,12 @@ func.func @test_from_ptr_0(%mr: memref<f32, #ptr.generic_space>) -> memref<f32,
   return %res : memref<f32, #ptr.generic_space>
 }
 
+/// Check the op doesn't fold because folding a ptr-type with metadata requires knowing the origin of the metadata.
 // CHECK-LABEL: @test_from_ptr_1
 // CHECK-SAME: (%[[MEM_REF:.*]]: memref<f32, #ptr.generic_space>)
 func.func @test_from_ptr_1(%mr: memref<f32, #ptr.generic_space>) -> memref<f32, #ptr.generic_space> {
-  // CHECK-NOT: ptr.to_ptr
-  // CHECK-NOT: ptr.from_ptr
-  // CHECK: return %[[MEM_REF]]
+  // CHECK: ptr.to_ptr
+  // CHECK: ptr.from_ptr
   %ptr = ptr.to_ptr %mr : memref<f32, #ptr.generic_space> -> !ptr.ptr<#ptr.generic_space>
   %res = ptr.from_ptr %ptr : !ptr.ptr<#ptr.generic_space> -> memref<f32, #ptr.generic_space>
   return %res : memref<f32, #ptr.generic_space>