Optimize load double into xmm with zero_extend

Optimize load double into xmm with zero_extend

"movq" should used to load double into xmm register with zero_extend:

(set (reg:V2DF 90)
     (vec_concat:V2DF (reg/v:DF 88 [ d ])
                      (const_double:DF 0.0 [0x0.0p+0])))

Unlike "movsd", which only works with load from memory, "movq" works
with both memory and xmm register.

gcc/

	PR target/70708
	* config/i386/sse.md (sse2_loadlpd): Accept load from "xm" and
	replace %vmovsd with "%vmovq".
	(vec_concatv2df): Likewise.

gcc/testsuite/

	PR target/70708
	* gcc.target/i386/pr70708.c: New test.

From-SVN: r235169