[Bug rtl-optimization/48037] Missed optimization: unnecessary register moves

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48037

--- Comment #8 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-03-15 
12:41:57 UTC ---
The patch fixed the pass-by-value cases to no longer go through stack memory.
The useless reg-reg moves prevail:

_Z6vsqrt2U8__vectord:
.LFB520:
        .cfi_startproc
        sqrtsd  %xmm0, %xmm1
        unpckhpd        %xmm0, %xmm0
        movapd  %xmm1, %xmm2
        sqrtsd  %xmm0, %xmm0
        unpcklpd        %xmm0, %xmm2
        movapd  %xmm2, %xmm0
        ret

both movapds can be avoided by better register allocation.