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Re: [PATCH][x86] Match movss and movsd "blend" instructions


On Donnerstag, 2. August 2018 23:46:37 CEST Jakub Jelinek wrote:
> On Thu, Aug 02, 2018 at 10:50:58PM +0200, Allan Sandfeld Jensen wrote:
> > Here is the version with __builtin_shuffle. It might be more expectable
> > -O0, but it is also uglier.
> 
> I don't find anything ugly on it, except the formatting glitches (missing
> space before (, overlong line, and useless __extension__.
> Improving code generated for __builtin_shuffle is desirable too.
> 

__extension__ is needed when using the the {...} initialization otherwise -
std=C89 will produce warnings about standards.  The line is a bit long, but I 
thought it looked better like this rather than adding any emergency line 
breaks. Is there a hard limit?

> > --- a/gcc/config/i386/xmmintrin.h
> > +++ b/gcc/config/i386/xmmintrin.h
> > @@ -1011,7 +1011,8 @@ _mm_storer_ps (float *__P, __m128 __A)
> > 
> >  extern __inline __m128 __attribute__((__gnu_inline__, __always_inline__,
> >  __artificial__)) _mm_move_ss (__m128 __A, __m128 __B)
> >  {
> > 
> > -  return (__m128) __builtin_ia32_movss ((__v4sf)__A, (__v4sf)__B);
> > +  return __extension__ (__m128) __builtin_shuffle((__v4sf)__A,
> > (__v4sf)__B, +                                                 
> > (__attribute__((__vector_size__ (16))) int){4, 1, 2, 3});
> And obviously use __v4si here instead of __attribute__((__vector_size__
> (16))) int.
> 
__v4si is declared in emmintrin.h, so I couldn't use it here unless I moved 
the definition. I tried changing as little as possible to not trigger bike 
shedding.

'Allan




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