Output vextract{i,f}{32x4,64x2} for (vec_select:(reg:Vmode) idx) when byte_offset of idx % 16 == 0.

2020-09-13  Hongtao Liu  <hongtao.liu@intel.com>
	    Peter Cordes  <peter@cordes.ca>
gcc/ChangeLog:

	PR target/91103
	* config/i386/sse.md (extract_suf): Add V8SF/V8SI/V4DF/V4DI.
	(*vec_extract<mode><ssescalarmodelower>_valign): Output
	vextract{i,f}{32x4,64x2} instruction when byte_offset % 16 ==
	0.

gcc/testsuite/ChangeLog:

	PR target/91103
	* gcc.target/i386/pr91103-1.c: Add extract tests.
	* gcc.target/i386/pr91103-2.c: Ditto.