Re: [PATCH][AArch64] Implement new intrinsics vabsd_s64 and vnegd_s64

[Vlad Lazar <vlad dot lazar at arm dot com>]

On 31/07/18 22:48, James Greenhalgh wrote:
> On Fri, Jul 20, 2018 at 04:37:34AM -0500, Vlad Lazar wrote:
> > Hi,
> >
> > The patch adds implementations for the NEON intrinsics vabsd_s64 and vnegd_s64.
> > (https://developer.arm.com/products/architecture/cpu-architecture/a-profile/docs/ihi0073/latest/arm-neon-intrinsics-reference-architecture-specification)
> >
> > Bootstrapped and regtested on aarch64-none-linux-gnu and there are no regressions.
> >
> > OK for trunk?
> >
> > +__extension__ extern __inline int64_t
> > +__attribute__ ((__always_inline__, __gnu_inline__, __artificial__))
> > +vnegd_s64 (int64_t __a)
> > +{
> > +  return -__a;
> > +}
>
> Does this give the correct behaviour for the minimum value of int64_t? That
> would be undefined behaviour in C, but well-defined under ACLE.
>
> Thanks,
> James

Hi. Thanks for the review.

For the minimum value of int64_t it behaves as the ACLE specifies:
"The negative of the minimum (signed) value is itself."

Thanks,
Vlad