On Tue, Jan 21, 2025 at 06:31:43AM -0300, Alexandre Oliva wrote:
> On Jan 21, 2025, Richard Biener <richard.guent...@gmail.com> wrote:
>
> > you can use bit_field_size () and bit_field_offset () unconditionally,
>
> Nice, thanks!
>
> > Now, we don't have the same handling on BIT_FIELD_REFs but it
> > seems it's enough to apply the check to those with a DECL as
> > object to operate on.
>
> I doubt that will be enough. I'm pretty sure the cases I saw in libgnat
> in which BIT_FIELD_REF changed could_trap status, compared with the
> preexisting convert-and-access-field it replaced, were not DECLs, but
> dereferences. But I'll check and report back. (I'll be AFK for most of
> the day, alas)
I'd think if we know for sure access is out of bounds, we shouldn't be
creating BIT_FIELD_REF for it (so in case of combine punt on the
optimization).
A different thing is if we don't know it, where the base is say a MEM_REF
or something similar.
Jakub
