i386.c (ix86_expand_vec_perm): In merge_two use mode SUBREG of operands[0] as target.

i386.c (ix86_expand_vec_perm): In merge_two use mode SUBREG of operands[0] as target.

	* config/i386/i386.c (ix86_expand_vec_perm): In merge_two use
	mode SUBREG of operands[0] as target.
	(valid_perm_using_mode_p): Don't ignore higher bits of d->perm.
	(expand_vec_pshufb): For V8SImode vmode emit avx2_permvarv8si.
	(expand_vec_perm_1): Handle identity and some broadcast
	permutations.
	(expand_vec_perm_interleave2): Handle also 32-byte modes, using
	vperm2[fi]128 or vpunpck[lh]* followed by single insn permutation.
	For d->testing_p return true earlier to avoid creating more GC
	garbage.
	(expand_vec_perm_vpermq_perm_1): New function.
	(expand_vec_perm_vpshufb2_vpermq): For d->testing_p return true
	earlier to avoid creating more GC garbage.  Fix handling of
	V16HImode.  Avoid some SUBREGs in SET_DEST.
	(expand_vec_perm_broadcast_1): Return false for 32-byte integer
	vector modes.
	(expand_vec_perm_vpshufb4_vpermq2): New function.
	(ix86_expand_vec_perm_builtin_1): Call expand_vec_perm_vpermq_perm_1
	and expand_vec_perm_vpshufb4_vpermq2.

From-SVN: r180169