https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95523
rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
--- Comment #3 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org>
---
(In reply to [email protected] from comment #2)
> (In reply to [email protected] from comment #1)
> > The reason for the assert is that the alignment is part of the
> > ABI of the types and is relied on when using LDR and STR for
> > some moves. Even though -fpack-struct=N changes the ABI in general,
> > I don't think it should change it in this particular case.
> >
> > I have to wonder why GCC even has -fpack-struct= though. Do you have
> > a specific need for it, or was this caught by option coverage testing?
> >
> > If there is no specific need, I'd be tempted to make -fpack-struct
> > unsupported for AArch64. I think there are so many other things
> > that could go wrong if it is used.
>
> We use the option in some projects. If this option is not supported, the
> impact is relatively large.
Ah, OK. If it's an issue that affects real use-cases then
let's make it work.
> I think it can make the error reporting more
> friendly, so that this option can still be used normally without sve.
>
> like:
> diff --git a/gcc/config/aarch64/aarch64-sve-builtins.cc
> b/gcc/config/aarch64/aarch64-sve-builtins.cc
> index bdb04e8170d..e93e766aba6 100644
> --- a/gcc/config/aarch64/aarch64-sve-builtins.cc
> +++ b/gcc/config/aarch64/aarch64-sve-builtins.cc
> @@ -3504,6 +3504,12 @@ handle_arm_sve_h ()
> return;
> }
>
> + if (maximum_field_alignment)
> + {
> + error ("SVE is incompatible with the use of %qs or %qs",
> "-fpack-struct", "#pragma pack");
> + return;
> + }
> +
> sve_switcher sve;
>
> /* Define the vector and tuple types. */
>
> Any suggestions?
Could you try setting DECL_USER_ALIGN on the FIELD_DECL?
that should (hopefully) force the field to keep its
natural alignment.
