Re: [PATCH v2] Handle OPAQUE_TYPE specially in verify_type [PR106833]

[Richard Biener <richard.guenther@gmail.com>]

On Fri, Sep 9, 2022 at 8:51 AM Kewen.Lin <linkw@linux.ibm.com> wrote:
>
> Hi Richi,
>
> Thanks for the review comments!
>
> on 2022/9/8 15:36, Richard Biener wrote:
> >
> >
> >> Am 08.09.2022 um 07:53 schrieb Kewen.Lin <linkw@linux.ibm.com>:
> >>
> >> Hi,
> >>
> >> As PR106833 shows, cv-qualified opaque type can cause ICE
> >> during LTO.  It exposes that we missd to handle OPAQUE_TYPE
> >> well in type verification.  As Richi pointed out, also
> >> assuming that target will always define TYPE_MAIN_VARIANT
> >> and TYPE_CANONICAL for opaque type, this patch is to check
> >> both are OPAQUE_TYPE_P.  Besides, it also checks the only
> >> available size and alignment information as well as type
> >> mode for TYPE_MAIN_VARIANT.
> >>
> ...
> >> +
> >> +  if (t != tv)
> >> +    {
> >> +      verify_match (TREE_CODE, t, tv);
> >> +      verify_match (TYPE_MODE, t, tv);
> >> +      verify_match (TYPE_SIZE, t, tv);
> >
> > TYPE_SIZE is a tree, you should probably
> > Compare this with operand_equal_p.  It’s
> > Not documented to be a constant size?
> > Thus some VLA vector mode might be allowed ( a poly_int size),
>
> Thanks for catching, I was referencing the code in function
> verify_type_variant, that corresponding part seems imperfect:
>
>       if (TREE_CODE (TYPE_SIZE (t)) != PLACEHOLDER_EXPR
>           && TREE_CODE (TYPE_SIZE (tv)) != PLACEHOLDER_EXPR)
>         verify_variant_match (TYPE_SIZE);
>
> I agree poly_int size is allowed, the patch was updated for it.
>
> BLKmode
> > Is ruled out(?),
>
> Yes, it requires a mode of MODE_OPAQUE class.
>
> the docs say we have
> > ‚An MODE_Opaque‘ here but I don’t see
> > This being verified?
> >
>
> There is a MODE equality check, I assumed the given t already
> has one MODE_OPAQUE mode, but the patch was updated to make
> it explicit as you concerned.
>
> > The macro makes this a bit unworldly
> > For the only benefit of elaborate diagnostic
> > Which I think isn’t really necessary
>
> OK, fixed!
>
> The previous version makes just one check on TYPE_CANONICAL to
> be cheap as gimple_canonical_types_compatible_p said, but
> since there are just several fields to be check, this updated
> version adjusted it to be the same as what's for TYPE_MAIN_VARIANT.
> Hope it's fine. :)

I think we'll call verify_type on the main variant as well so that would be
redundant (ensured by transitivity), can you check?

> Tested as before.
>
> Does this updated patch look good to you?

Yes, please remove the checks against the main variant if the above holds,
OK with or without that change depending on this outcome.

Thanks,
Richard.


>
> BR,
> Kewen
> ------