https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102811
--- Comment #20 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Uroš Bizjak from comment #18)
> (In reply to Uroš Bizjak from comment #17)
> > (In reply to Hongtao.liu from comment #16)
> >
> > > ix86_expand_vector_set is mainly used by vec_set_optab which exactly takes
> > > target as both input and output, it seems we can't create a new target for
> > > that.
> >
> > OK, let's try to optimize it with gen_pinsr, as you proposed.
> >
> > (It looks that the add-on patch from Comment #6 will generate VPBLEND in
> > this case, too.)
>
> We should manually generate vinsertps from truncsfhf2, too. There is no
> point to call ix86_expand_vector_set if we already know the instruction. It
> will use vec_set<VI4F_128:mode>_0 insn pattern, which has quite some
> alternatives.
For AVX2, your attached patch will optimize
vpxor %xmm2, %xmm2, %xmm2
- vpbroadcastw %xmm1, %xmm1
- vpbroadcastw %xmm0, %xmm0
vpblendw $1, %xmm0, %xmm2, %xmm0
vpblendw $1, %xmm1, %xmm2, %xmm2
vcvtph2ps %xmm2, %xmm2
Since upper bits of xmm1/xmm0 is not selected by vpblendw.
