add inplace_view tag to resize_() (#82667)

`resize_()` is annoying because it needs special casing for functionalization. It's technically an inplace-view op, but it can't really have a pure view variant, since calling resize_() might bust the old storage. I gave it an `inplace_view` tag so that stuff like `FakeTensor` that relies on tags will pick it up properly, which required  jumping through some codegen hoops.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/82667
Approved by: https://github.com/eellison

aten/src/ATen/native/native_functions.yaml

@@ -2076,6 +2076,7 @@
   variants: method
   device_check: NoCheck
   device_guard: False
+  tags: inplace_view
   dispatch:
     CPU, Meta: resize_
     CUDA: resize_cuda_

torchgen/gen.py

@@ -244,7 +244,12 @@ def error_check_native_functions(funcs: Sequence[NativeFunction]) -> None:
                 f"{f.structured_delegate}, but {f.structured_delegate} is not marked as structured. "
                 f"Consider adding 'structured=True' to the delegated operator"
             )
-        if "inplace_view" in f.tags:
+        # See Note [resize_ in Functionalization]
+        # resize_() is technically an inplace view op (and therefore needs the tag),
+        # but it would be overkill to add a true "view" variant of resize.
+        # Instead, resize_() gets special treatment in functionalization,
+        # and we have a resize() op that is non-aliasing + functional.
+        if "inplace_view" in f.tags and str(f.func.name) != "resize_":
             base_name = f.func.name.name
             overload_name = f.func.name.overload_name
             assert base_name.inplace, (

torchgen/gen_functionalization_type.py

@@ -53,6 +53,8 @@ MUTABLE_OPS_NOT_USING_FUNCTIONALIZATION = (
         # It will be BC-breaking, but we should fix their schemas.
         # should be inplace?
         "record_stream",
+        # See Note [resize_ in Functionalization]
+        "resize_",
     ]
 )
 

torchgen/model.py

@@ -890,7 +890,10 @@ class NativeFunction:
         is_non_mutating_view = len(rets) > 0 and any(
             r.annotation is not None and not r.annotation.is_write for r in rets
         )
-        is_inplace_view = "inplace_view" in self.tags
+        # See Note [resize_ in Functionalization] for more dtails
+        is_inplace_view = (
+            "inplace_view" in self.tags and str(self.func.name) != "resize_"
+        )
         is_wildcard_view = any(
             inp.annotation is not None and inp.annotation.alias_set_after != ""
             for inp in self.func.schema_order_arguments()

torchgen/native_function_generation.py

@@ -304,9 +304,7 @@ def add_generated_native_functions(
             # Don't bother generating functions trio's for native functions that bypass the dispatcher.
             are_manual = all(f.manual_cpp_binding for f in d.values())
             # Don't bother generating functional + out= variants for view operators
-            has_view_ops = (
-                has_inplace and "inplace_view" in d[SchemaKind.inplace].tags
-            ) or any(f.is_view_op for f in d.values())
+            has_view_ops = any(f.is_view_op for f in d.values())
             # Don't generate the other variants for CompositeImplicitAutograd operators.
             # We could probably do this, but the main benefit of generating the function triplets
             # is for transforms that need them, and transforms don't need to act directly