i386: Do not sanitize upper part of V2SFmode reg with -fno-trapping-math [PR110832]

i386: Do not sanitize upper part of V2SFmode reg with -fno-trapping-math [PR110832]

Also introduce -m[no-]partial-vector-fp-math option to disable trapping
V2SF named patterns in order to avoid generation of partial vector V4SFmode
trapping instructions.

The new option is enabled by default, because even with sanitization,
a small but consistent speed up of 2 to 3% with Polyhedron capacita
benchmark can be achieved vs. scalar code.

Using -fno-trapping-math improves Polyhedron capacita runtime 8 to 9%
vs. scalar code.  This is what clang does by default, as it defaults
to -fno-trapping-math.

	PR target/110832

gcc/ChangeLog:

	* config/i386/i386.opt (mpartial-vector-fp-math): New option.
	* config/i386/mmx.md (movq_<mode>_to_sse): Do not sanitize
	upper part of V2SFmode register with -fno-trapping-math.
	(<plusminusmult:insn>v2sf3): Enable for ix86_partial_vec_fp_math.
	(divv2sf3): Ditto.
	(<smaxmin:code>v2sf3): Ditto.
	(sqrtv2sf2): Ditto.
	(*mmx_haddv2sf3_low): Ditto.
	(*mmx_hsubv2sf3_low): Ditto.
	(vec_addsubv2sf3): Ditto.
	(vec_cmpv2sfv2si): Ditto.
	(vcond<V2FI:mode>v2sf): Ditto.
	(fmav2sf4): Ditto.
	(fmsv2sf4): Ditto.
	(fnmav2sf4): Ditto.
	(fnmsv2sf4): Ditto.
	(fix_truncv2sfv2si2): Ditto.
	(fixuns_truncv2sfv2si2): Ditto.
	(floatv2siv2sf2): Ditto.
	(floatunsv2siv2sf2): Ditto.
	(nearbyintv2sf2): Ditto.
	(rintv2sf2): Ditto.
	(lrintv2sfv2si2): Ditto.
	(ceilv2sf2): Ditto.
	(lceilv2sfv2si2): Ditto.
	(floorv2sf2): Ditto.
	(lfloorv2sfv2si2): Ditto.
	(btruncv2sf2): Ditto.
	(roundv2sf2): Ditto.
	(lroundv2sfv2si2): Ditto.
	* doc/invoke.texi (x86 Options): Document
	-mpartial-vector-fp-math option.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr110832-1.c: New test.
	* gcc.target/i386/pr110832-2.c: New test.
	* gcc.target/i386/pr110832-3.c: New test.