[PATCH v2] x86: Use flag output operands for inline asm in atomic-machine.h

[Florian Weimer]

* Uros Bizjak:

> Use the flag output constraints feature available in gcc 6+
> ("=@cc<cond>") instead of explicitly setting a boolean variable
> with SETcc instruction.  This approach decouples the instruction
> that sets the flags from the code that consumes them, allowing
> the compiler to create better code when working with flags users.
> Instead of e.g.:
>
>    lock add %esi,(%rdi)
>    sets   %sil
>    test   %sil,%sil
>    jne    <...>
>
> the compiler now generates:
>
>    lock add %esi,(%rdi)
>    js     <...>
>
> No functional changes intended.
>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> Cc: H.J.Lu <hjl.tools@gmail.com>
> Cc: Florian Weimer <fweimer@redhat.com>
> Cc: Carlos O'Donell <carlos@redhat.com>

Thanks, this now looks good to me.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

Florian