i386: Fix up V2SFmode vcond* with -mxop [PR100581]

i386: Fix up V2SFmode vcond* with -mxop [PR100581]

ix86_expand_sse_movcc has special TARGET_XOP handling and the recent
addition of support of v*cond* patterns for V2SFmode results in
ICEs because the expected pattern doesn't exist.  We can handle it
using 128-bit vpcmov (if we ignore the upper 64 bits like we ignore in
other TARGET_MMX_WITH_SSE support).

2021-05-13  Uroš Bizjak  <ubizjak@gmail.com>

gcc/
	PR target/100581
	* config/i386/i386-expand.c (ix86_expand_sse_movcc): Force mode
	sizes < 16 to a register when constructing vpcmov pattern.
	* config/i386/mmx.md (*xop_pcmov_<mode>): Use MMXMODE124 mode.

gcc/testsuite/

	PR target/100581
	* g++.target/i386/pr100581.C: New test.