On Tue, Feb 25, 2020 at 07:43:09PM -0600, Bill Schmidt wrote:
> The reason that homogeneous aggregates matter (at least somewhat) is that
> the ABI ^H^H^H^HAPI requires establishing a calling convention and a name-
> mangling formula that includes the length of parameters and return values.
> Since ELFv2 and ELFv1 do not have the same calling convention, and ELFv2
> has a superior one, we chose to use ELFv2's calling convention and make use
> of homogeneous aggregates for return values in registers for the case of
> vectorized sincos.
Can you please explain how do you want to pass the
void sincos (double, double *, double *);
arguments? I must say it isn't entirely clear from the document.
You talk there about double[2], but sincos certainly doesn't have such an
argument.
Also, I'd say ignoring the masked variants is a mistake, are you going to
warn any time the user uses inbranch or even doesn't specify notinbranch?
The masking can be implemented even without highly specialized instructions,
e.g. on x86 only AVX512F has full masking support, for older ISAs all that
is there is conditional store or e.g. for integral operations that can't
trap/raise exceptions just doing blend-like operations (or even and/or) is
all that is needed; just let the vectorizer do its job.
Even if you don't want it for libmvec, just use
__attribute__((simd ("notinbranch")))
for those, but allow the user to use it where it makes sense.
Jakub
