On Tue, Feb 28, 2023 at 12:05:20PM +0000, Richard Biener via Gcc-patches wrote:
> > + p = &TYPE_POINTER_TO (TREE_TYPE (t));
> > + else if (TREE_CODE (t) == REFERENCE_TYPE && !TYPE_REF_IS_RVALUE (t))
> > + p = &TYPE_REFERENCE_TO (TREE_TYPE (t));
> > + if (p)
> > + {
> > + tree t2;
> > + for (t2 = *p; t2; t2 = TYPE_NEXT_PTR_TO (t2))
> > + if (TYPE_MODE (t2) == TYPE_MODE (t)
> > + && TYPE_REF_CAN_ALIAS_ALL (t2) == TYPE_REF_CAN_ALIAS_ALL (t))
> > + break;
>
> Can we elide this searching please? Having duplicated should be harmless
> unless proved otherwise.
I've posted 2 patches (one inlined, another attached), the second one
didn't do this at all.
Having (too many) duplicates would be harmful because build_pointer_type
etc. walk up to the whole length of list all the time. When the list
length is bounded (say at most 2 modes - ptr_mode/Pmode, times 2 (the
can alias all bool), then it doesn't hurt, if it could in theory be
arbitrarily long, it would be a compile time problem.
But given that we with the !TYPE_ATTRIBUTES/!TYPE_REF_IS_RVALUE change
don't have a testcase that would show it is a problem actually ever
encounterable, the second patch without this is fine I think.
>
> OK with that change.
Jakub
