https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83628
--- Comment #6 from Uroš Bizjak <ubizjak at gmail dot com> --- On a related note, gcc-5 (-O2) was able to also simplify: int test (int a, int b, int c) { return (a < b) * 4 + c; } cmplt $16,$17,$17 s4addl $17,$18,$0 ret $31,($26),1 where gcc-8 emits: cmplt $16,$17,$0 s4addq $0,0,$0 addl $0,$18,$0 ret $31,($26),1 gcc-5 is able to if-convert to: (insn 30 10 15 2 (set (reg:DI 70 [ D.1498 ]) (if_then_else:DI (ne (reg:DI 76) (const_int 0 [0])) (const_int 4 [0x4]) (const_int 0 [0]))) cmp1.c:5 161 {*movdicc_internal} (nil)) which is later combined with: (insn 15 30 16 2 (set (reg:SI 77 [ D.1498 ]) (plus:SI (subreg/s/u:SI (reg:DI 70 [ D.1498 ]) 0) (subreg/s/u:SI (reg/v:DI 75 [ c ]) 0))) cmp1.c:5 3 {addsi3} (expr_list:REG_DEAD (reg/v:DI 75 [ c ]) (expr_list:REG_DEAD (reg:DI 70 [ D.1498 ]) (nil)))) to: Trying 30 -> 15: Successfully matched this instruction: (set (reg:SI 77 [ D.1498 ]) (plus:SI (mult:SI (subreg:SI (reg:DI 76) 0) (const_int 4 [0x4])) (reg:SI 18 $18 [ c ]))) gcc-8 is not able to if-convert...