http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41082
--- Comment #61 from Jakub Jelinek <jakub at gcc dot gnu.org> 2010-12-07 22:07:59 UTC --- I've managed to massage both -O3 -m64 -mtune={rs64,power4} darwin assembly into ppc64-linux assembly. Before DSE2 we have: (insn 460 483 925 33 (set (reg:CC 75 cr7) (compare:CC (reg:SI 11 r11 [orig:866 reduce+32 ] [866]) (const_int 6 [0x6]))) where_2.f90:11 451 {*cmpsi_internal1} (nil)) (insn 925 460 926 33 (set (reg:CC 0 r0) (reg:CC 75 cr7)) where_2.f90:11 358 {*movcc_internal1} (nil)) (insn 926 925 467 33 (set (mem/c:CC (plus:DI (reg/f:DI 1 r1) (const_int 272 [0x110])) [5 %sfp+272 S4 A32]) (reg:CC 0 r0)) where_2.f90:11 358 {*movcc_internal1} (nil)) ... # %sfp+272 not used anywhere here (insn 931 415 932 33 (set (reg:CC 19 r19) (mem/c:CC (plus:DI (reg/f:DI 1 r1) (const_int 272 [0x110])) [5 %sfp+272 S4 A32])) where_2.f90:11 358 {*movcc_internal1} (nil)) (insn 932 931 461 33 (set (reg:CC 74 cr6) (reg:CC 19 r19)) where_2.f90:11 358 {*movcc_internal1} (nil)) (insn 461 932 422 33 (set (reg:SI 27 r27 [712]) (gt:SI (reg:CC 74 cr6) (const_int 0 [0]))) where_2.f90:11 462 {*rs6000.md:13486} (nil)) and DSE2 somehow decides to nuke the insn 926 store. The error could be also that RA decides to share %sfp+272 not just for the CCmode stuff, but also before that for a SImode value. Looking into it...