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?

Bootstrapped & regtested on powerpc64le-linux-gnu P9,
x86_64-redhat-linux and aarch64-linux-gnu.

BR,
Kewen
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gcc/ChangeLog:

	* tree-vect-patterns.c (vect_recog_mulhs_pattern): Add support to
	recog normal multiply highpart.