[Bug c/111811] [14 Regression] ICE with vector float bitfield after error

["rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811

--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> ---
On Mon, 13 Nov 2023, joseph at codesourcery dot com wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111811
> 
> --- Comment #4 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
> The checks are in check_bitfield_type_and_width.  I expect the attribute - 
> in this position a declaration attribute - gets applied after that (and 
> while applying it results in a change to the type, and thus in the 
> declaration being laid out again, this check doesn't get repeated).
> 
> In this case, the existing check is correct but not sufficient.  In 
> another case the check is arguably too early:
> 
> struct s { int __attribute__ ((__mode__ (DI))) x : 50; };
> 
> Considering int __attribute__ ((__mode__ (DI))) as a DImode integer type, 
> that bit-field width is valid - but it's rejected because the check is 
> carried out on int, before the attribute gets applied.  Getting that case 
> to work might require extracting early those declaration attributes that 
> actually affect the type, so they can be applied to the type before the 
> declaration gets constructed and such checks are carried out.

Ah, and when applying the vector_size attribute the FIELD_DECL hasn't been
updated to indicate we identified it as bitfield (so we could reject
the attribute) ...

I'll leave this to frontend folks to sort out.