http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52419
Richard Guenther <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|REOPENED |NEW --- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-02-29 13:28:00 UTC --- Confirmed. foo: .LFB0: .cfi_startproc pxor %xmm1, %xmm1 movhps .LC0(%rip), %xmm1 movdqu %xmm1, (%rdi) ret it looks like (insn 6 5 7 (set (reg:DI 61) (const_int 5 [0x5])) t.c:23 -1 (nil)) (insn 7 6 8 (set (reg:DI 62) (vec_select:DI (reg:V2DI 60) (parallel [ (const_int 0 [0]) ]))) t.c:23 -1 (nil)) (insn 8 7 9 (set (reg:V2DI 60) (vec_concat:V2DI (reg:DI 62) (reg:DI 61))) t.c:23 -1 (nil)) (insn 9 8 0 (set (mem:V16QI (reg/v/f:DI 59 [ p ]) [0 *p_1(D)+0 S16 A8]) (unspec:V16QI [ (subreg:V16QI (reg:V2DI 60) 0) ] UNSPEC_MOVU)) t.c:23 -1 (nil)) which of course does not work as ref:V2DI 60 is unsed uninitialized in insn 7.