For instructions with xmm operand:

op %xmmN,%xmmQ,%xmmQ ----> op %xmmN, %xmmN, %xmmQ

for instruction with mem operand or gpr operand:

op mem/gpr, %xmmQ, %xmmQ

--->  using pass rpad ---->

xorps %xmmN, %xmmN, %xxN
op mem/gpr, %xmmN, %xmmQ

Performance influence of SPEC2017 fprate which is tested on SKX
----
503.bwaves_r	-0.03%
507.cactuBSSN_r -0.22%
508.namd_r	-0.02%
510.parest_r	0.37%
511.povray_r	0.74%
519.lbm_r	0.24%
521.wrf_r	2.35%
526.blender_r	0.71%
527.cam4_r	0.65%
538.imagick_r	0.95%
544.nab_r	-0.37
549.fotonik3d_r 0.24%
554.roms_r	0.90%
fprate geomean	0.50%
-----

Changelog
gcc/
	* config/i386/i386.md (*rcpsf2_sse): Add
	avx_partial_xmm_update, prefer m constraint for TARGET_AVX.
	(*rsqrtsf2_sse): Ditto.
	(*sqrt<mode>2_sse): Ditto.
	(sse4_1_round<mode>2): separate constraint vm, add
	avx_partail_xmm_update, prefer m constraint for TARGET_AVX.
	* config/i386/sse.md (*sse_vmrcpv4sf2"): New define_insn used
	by pass rpad.
	(*<sse>_vmsqrt<mode>2<mask_scalar_name><round_scalar_name>*):
	Ditto.
	(*sse_vmrsqrtv4sf2): Ditto.
	(*avx512f_rndscale<mode><round_saeonly_name>): Ditto.
	(*sse4_1_round<ssescalarmodesuffix>): Ditto.
	(sse4_1_round<ssescalarmodesuffix>): Add m constraint and
	<iptr> pointer size modifier since vround support memory operand.

gcc/testsuite
	* gcc.target/i386/pr87007-4.c: New test.
	* gcc.target/i386/pr87007-5.c: Ditto.

From-SVN: r277469