https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101393
Segher Boessenkool <segher at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |amodra at gcc dot gnu.org
--- Comment #8 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Franz Sirl from comment #7)
> Created attachment 51189 [details]
> More complete trial patch to overhaul ASM_CPU_SPEC
>
> This patch should be more complete now. It does the following basic things:
If it does a few things, it should be a few patches, not one.
> - Only pass -many to the assembler when -massembler-any is given
Interesting idea! I wonder how well that works, how many programs will
need to use that new flag (for their inline assembler code).
> - Unify the non-AIX (for now) asm_cpu spec settings into rs6000-cpus.def.
> Currently this uses a "static inline" function because I developed on GCC10,
> on GCC11 and later using a constexpr would be much nicer.
>
> Now, the other stuff to reliably handle -many would need some gas support,
> where I likely need some help, because I've no expertise there.
>
> First, I suggest to introduce 2 assembler warning options:
>
> -wany-duplicates: Warn if the mnemonic to assemble has duplicates because
> of -many, this should limit the warnings to the most difficult cases. In the
> patch it's automatically enabled when -massembler-any is used.
> -wany-strict: Warn if any mnemonic to assemble is only fulfilled because of
> -many.
You'll have to discuss this on binut...@sourceware.org .
> And also some additional/changed options for .machine:
>
> .machine "resetsticky": Reset the sticky flags (eg. VSX, AltiVec, ANY)
> .machine "pushsticky": Push CPU+sticky settings, reset the sticky flags
> .machine "push": Change to push CPU+sticky, keep the sticky flags
> .machine "pop": Change to pop CPU+sticky
Why would you want this concept? It is mixing .machine selection with
other things.
> The attached patch tries to make use of such a TBD change to gas.
>
> Alternatively, gas could be changed to have -madditive-sticky and/or
> '.machine "additive-sticky"' to make any '.machine "realcpu"' reset the
> sticky flags and they have to be re-added again afterwards if needed. Maybe
> this push/pop-less solution would be even easier to handle in the compiler?
>
> What do you think? I hope I addressed most of your concerns, suggestions
> welcome.
I don't think it is a good idea to add workaround upon workaround to avoid
some of the not-so-useful behaviours of -many. Instead, we should just
not use -many?
[ Cc: Alan, for the binutils side of things ]
