On Fri, Jun 09, 2023 at 08:37:20PM +0800, Xi Ruoyao wrote:
> Ping (in hopes that someone can review before the weekend).
>
> On Sat, 2023-06-03 at 19:25 +0800, Xi Ruoyao wrote:
> > We used to skip ifunc check when CX16 is available. But now we use
> > CX16+AVX+Intel/AMD for the "perfect" 16b load implementation, so CX16
> > alone is not a sufficient reason not to use ifunc (see PR104688).
> >
> > This causes a subtle and annoying issue: when GCC is built with a
> > higher -march= setting in CFLAGS_FOR_TARGET, ifunc is disabled and
> > the worst (locked) implementation of __atomic_load_16 is always used.
> >
> > There seems no good way to check if the CPU is Intel or AMD from
> > the built-in macros (maybe we can check every known model like
> > __skylake,
> > __bdver2, ..., but it will be very error-prune and require an update
> > whenever we add the support for a new x86 model). The best thing we
> > can
> > do seems "always try ifunc" here.
> >
> > Bootstrapped and tested on x86_64-linux-gnu. Ok for trunk?
> >
> > libatomic/ChangeLog:
> >
> > * configure.tgt: For x86_64, always set try_ifunc=yes.
Ok, thanks.
Jakub
