Re: [PATCH] rs6000: Add Power10 optimization for _mm_blendv*

[David Edelsohn <dje.gcc@gmail.com>]

On Fri, Jan 7, 2022 at 3:32 PM Paul A. Clarke <pc@us.ibm.com> wrote:
>
> On Fri, Jan 07, 2022 at 02:15:22PM -0500, David Edelsohn wrote:
> > > Power10 ISA added `xxblendv*` instructions which are realized in the
> > > `vec_blendv` instrinsic.
> > >
> > > Use `vec_blendv` for `_mm_blendv_epi8`, `_mm_blendv_ps`, and
> > > `_mm_blendv_pd` compatibility intrinsics, when `_ARCH_PWR10`.
> > >
> > > Also, copy a test from i386 for testing `_mm_blendv_ps`.
> > > This should have come with commit ed04cf6d73e233c74c4e55c27f1cbd89ae4710e8,
> > > but was inadvertently omitted.
> > >
> > > 2021-10-20  Paul A. Clarke  <pc@us.ibm.com>
> > >
> > > gcc
> > > * config/rs6000/smmintrin.h (_mm_blendv_epi8): Use vec_blendv
> > > when _ARCH_PWR10.
> > > (_mm_blendv_ps): Likewise.
> > > (_mm_blendv_pd): Likewise.
> > >
> > > gcc/testsuite
> > > * gcc.target/powerpc/sse4_1-blendvps.c: Copy from gcc.target/i386,
> > > adjust dg directives to suit.
> > > ---
> > > Tested on Power10 powerpc64le-linux (compiled with and without
> > > `-mcpu=power10`).
> > >
> > > OK for trunk?
> >
> > This is okay modulo
> >
> > > + return (__m128i) vec_blendv ((__v16qu) __A, (__v16qu) __B, (__v16qu) __mask);
> >
> > Should the above be __v16qi like x86?
>
> That does arguably match the types involved (epi8) better.
>
> Shall I change the original implementation as well (4 lines later)?
>
> >   return (__m128i) vec_sel ((__v16qi) __A, (__v16qi) __B, __lmask);

vec_blendv supports the signed type, so it seems that the function
should use that type, unless unsigned is preferred because PowerPC
defaults to unsigned char.

I wasn't going to recommend changing the existing code because I don't
know how the signed type interacts with the other builtins.

Thanks, David