https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107172
--- Comment #10 from Segher Boessenkool <segher at gcc dot gnu.org> --- The input to combine has (insn 49 10 50 2 (parallel [ (set (reg:CCC 17 flags) (ne:CCC (reg:SI 82 [ a.1_2 ]) (const_int 0 [0]))) (set (reg:SI 92) (neg:SI (reg:SI 82 [ a.1_2 ]))) ]) "107172.c":4:10 680 {*negsi_ccc_1} (expr_list:REG_DEAD (reg:SI 82 [ a.1_2 ]) (expr_list:REG_UNUSED (reg:SI 92) (nil)))) (insn 50 49 51 2 (parallel [ (set (reg:SI 93) (neg:SI (ltu:SI (reg:CCC 17 flags) (const_int 0 [0])))) (clobber (reg:CC 17 flags)) ]) "107172.c":4:10 1258 {*x86_movsicc_0_m1_neg} (expr_list:REG_DEAD (reg:CCC 17 flags) (expr_list:REG_UNUSED (reg:CC 17 flags) (nil)))) This is incorrect already: insn 49 has to do a cmp, not a ne, for it to be valid. It was created by the ce1 pass.