i386: Tweak ix86_expand_int_compare to use PTEST for vector equality.

I've come up with an alternate/complementary/supplementary fix to the
patch https://gcc.gnu.org/pipermail/gcc-patches/2023-June/622706.html
for generating the PTEST during RTL expansion, rather than rely on
this being caught/optimized later during STV.

You'll notice in this patch, the tests for TARGET_SSE4_1 and TImode
appear last.  When I was writing this, I initially also added support
for AVX VPTEST and OImode, before realizing that x86 doesn't (yet)
support 256-bit OImode (which also explains why we don't have an OImode
to V1OImode scalar-to-vector pass).  Retaining this clause ordering
should minimize the lines changed if things change in future.

2023-07-12  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/i386/i386-expand.cc (ix86_expand_int_compare): If
	testing a TImode SUBREG of a 128-bit vector register against
	zero, use a PTEST instruction instead of first moving it to
	a pair of scalar registers.

0 files changed, 0 insertions, 0 deletions