https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112835
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2023-12-03
Target| |x86_64-linux-gnu
| |aarch64-linux-gnu
Component|target |middle-end
Keywords| |missed-optimization
Ever confirmed|0 |1
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
aarch64 code generation is slightly better:
...
.L2:
mov w0, 1
eor w0, w0, 1
ret
...
mov w0, 0
eor w0, w0, 1
ret
But there is no reason for the mov followed by eor there, it should just be a
mov.
Note the gimple level is fine:
_1 = __builtin_memcmp_eq (a_3(D), b_4(D), 12);
_5 = _1 == 0;
Expansion does:
```
(jump_insn 14 13 33 4 (set (pc)
(if_then_else (ne (reg:CC 66 cc)
(const_int 0 [0]))
(label_ref 19)
(pc))) "/app/example.cpp":5:24 -1
(int_list:REG_BR_PROB 708669604 (nil))
-> 19)
(note 33 14 15 5 [bb 5] NOTE_INSN_BASIC_BLOCK)
(insn 15 33 16 5 (set (reg:SI 92 [ _1 ])
(const_int 0 [0])) "/app/example.cpp":5:24 -1
(nil))
(jump_insn 16 15 17 5 (set (pc)
(label_ref 21)) "/app/example.cpp":5:24 -1
(nil)
-> 21)
(barrier 17 16 18)
(barrier 18 17 19)
(code_label 19 18 34 6 2 (nil) [2 uses])
(note 34 19 20 6 [bb 6] NOTE_INSN_BASIC_BLOCK)
(insn 20 34 21 6 (set (reg:SI 92 [ _1 ])
(const_int 1 [0x1])) "/app/example.cpp":5:24 -1
(nil))
(code_label 21 20 35 7 3 (nil) [1 uses])
(note 35 21 22 7 [bb 7] NOTE_INSN_BASIC_BLOCK)
(insn 22 35 23 7 (set (reg:CC 66 cc)
(compare:CC (reg:SI 92 [ _1 ])
(const_int 0 [0]))) "/app/example.cpp":5:33 discrim 1 -1
(nil))
(insn 23 22 24 7 (set (reg:SI 102)
(eq:SI (reg:CC 66 cc)
(const_int 0 [0]))) "/app/example.cpp":5:33 discrim 1 -1
(nil))
```
Seems like we could do a better job at expansion here ...
