https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87555
--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Hongtao.liu from comment #10)
> > Note I'm not sure that doing fmaddsub as merge of fma and fms will be
> > optimal since that most definitely will preclude combine from recognizing
> > fmaddsub from (addsub (mul ..) x) which would be another goal to support
> > (PR81904)
>
> I guess you're talking about
>
> #include <x86intrin.h>
> __m128d f(__m128d x, __m128d y, __m128d z){
> return _mm_addsub_pd(_mm_mul_pd(x,y),z);
> }
>
> which pass_combine tries
>
> Failed to match this instruction:
> (set (reg:V2DF 88)
> (vec_merge:V2DF (minus:V2DF (mult:V2DF (reg:V2DF 90)
> (reg:V2DF 91))
> (reg:V2DF 92))
> (plus:V2DF (mult:V2DF (reg:V2DF 90)
> (reg:V2DF 91))
> (reg:V2DF 92))
> (const_int 1 [0x1])))
>
> but doesn't realize fisrt merge operand is fms and second is fma.
Yes. This situation will happen when I push the SLP pattern detection
for addsub - we then no longer detect FMA on the GIMPLE level (we might
want to improve that as well, of course, exposing standard pattern names
for fmaddsub and fmsubadd).
