On Tue, Jul 13, 2021 at 10:53 AM Kewen.Lin <li...@linux.ibm.com> wrote:
>
> Hi,
>
> When I added the support for Power10 newly introduced multiply
> highpart instrutions, I noticed that currently vectorizer
> doesn't try to vectorize multiply highpart pattern, I hope
> this isn't intentional?
>
> This patch is to extend the existing pattern mulhs handlings
> to cover multiply highpart. Another alternative seems to
> recog mul_highpart operation in a general place applied for
> scalar code when the target supports the optab for the scalar
> operation, it's based on the assumption that one target which
> supports vector version of multiply highpart should have the
> scalar version. I noticed that the function can_mult_highpart_p
> can check/handle mult_highpart well even without mul_highpart
> optab support, I think to recog this pattern in vectorizer
> is better. Is it on the right track?
I think it's on the right track, using IFN_LAST is a bit awkward
in case yet another case pops up so maybe you can use
a code_helper instance instead which unifies tree_code,
builtin_code and internal_fn?
I also notice that can_mult_highpart_p will return true if
only vec_widen_[us]mult_{even,odd,hi,lo} are available,
but then the result might be less optimal (or even not
handled later)?
That is, what about adding optab internal functions
for [us]mul_highpart instead, much like the existing
ones for MULH{R,}S?
Richard.
>
> Bootstrapped & regtested on powerpc64le-linux-gnu P9,
> x86_64-redhat-linux and aarch64-linux-gnu.
>
> BR,
> Kewen
> -----
> gcc/ChangeLog:
>
> * tree-vect-patterns.c (vect_recog_mulhs_pattern): Add support to
> recog normal multiply highpart.
>
