Re: GNU_PROPERTY_X86_* questions

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Oct 10, 2019 at 6:33 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> H.J.,
>
> I think I'm seeing a number of issues with the handling of these
> properties in gas, but without the original commit referencing a
> specification I can't really determine if some or all of these
> are actually "working as designed".
>
> Some of the points are:
> - What is the actual meaning of a set bit? I.e. should e.g. -O

https://github.com/hjl-tools/x86-psABI/wiki/X86-psABI

>   converting between ISAs actually be reflected in the produced
>   note?

It records what are in the object file.

> - What is the rule of ISAs to get (or not get) a flag defined?
>   E.g. why are there AVX, AVX2, and FMA flags, but no XOP nor
>   FMA4 ones?

One can propose them.

> - What is the rule of register sets getting feature flags
>   defined? E.g. why are there XMM etc flags but there's no mask
>   register one?

One can propose them.

> - What are the rules for the feature flags actually getting set?
>   I find it puzzling that there are straight use
>   i.has_reg{x,y,z}mm flags (which could be easily done away
>   with), but for MMX quite a bit of extra logic is involved.
>

MMX is set for pure MMX related instructions.

-- 
H.J.