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* [Bug tree-optimization/97961] New: unnecessary moves with __builtin_{add,sub}_overflow_p and __int128
@ 2020-11-23 17:58 denis.campredon at gmail dot com
2022-11-08 0:14 ` [Bug rtl-optimization/97961] " pinskia at gcc dot gnu.org
2023-01-19 23:23 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: denis.campredon at gmail dot com @ 2020-11-23 17:58 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97961
Bug ID: 97961
Summary: unnecessary moves with __builtin_{add,sub}_overflow_p
and __int128
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: denis.campredon at gmail dot com
Target Milestone: ---
In #97950 Jackub told me to open a new bug for that.
The snippet bellow has the following problems
- f1 and f2 generate 4 unnecessary moves
mov r9, rdi
mov r8, rsi
mov rsi, r9
mov rdi, r8
- f4 has "only" 2 unnecessary moves
mov r9, rdi
mov rdi, rsi
- f3 should be identical to f4 except for the flag checking.
------------
bool f1(unsigned __int128 a,unsigned __int128 b) {
return __builtin_add_overflow_p(a, b, (unsigned __int128)0);
}
bool f2(__int128 a,__int128 b) {
return __builtin_add_overflow_p(a, b, (__int128)0);
}
bool f3(unsigned __int128 a,unsigned __int128 b) {
return __builtin_sub_overflow_p(a, b, (unsigned __int128)0);
}
bool f4(__int128 a,__int128 b) {
return __builtin_sub_overflow_p(a, b, (__int128)0);
}
------------
asm generated
------------
f1(unsigned __int128, unsigned __int128):
mov r9, rdi
mov r8, rsi
mov rsi, r9
mov rdi, r8
add rsi, rdx
adc rdi, rcx
setc al
ret
f2(__int128, __int128):
mov r9, rdi
mov r8, rsi
mov rsi, r9
mov rdi, r8
add rsi, rdx
adc rdi, rcx
seto al
ret
f3(unsigned __int128, unsigned __int128):
mov r9, rdi
mov r8, rsi
mov rdi, r8
mov rax, r9
mov r8, rdx
sub rax, r8
mov rdx, rdi
sbb rdx, rcx
cmp r9, rax
mov rcx, rdi
sbb rcx, rdx
setc al
ret
f4(__int128, __int128):
mov r9, rdi
mov rdi, rsi
cmp r9, rdx
sbb rdi, rcx
seto al
ret
-------------------
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug rtl-optimization/97961] unnecessary moves with __builtin_{add,sub}_overflow_p and __int128
2020-11-23 17:58 [Bug tree-optimization/97961] New: unnecessary moves with __builtin_{add,sub}_overflow_p and __int128 denis.campredon at gmail dot com
@ 2022-11-08 0:14 ` pinskia at gcc dot gnu.org
2023-01-19 23:23 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-11-08 0:14 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97961
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2022-11-08
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
aarch64 produces the code without any extra moves ...
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug rtl-optimization/97961] unnecessary moves with __builtin_{add,sub}_overflow_p and __int128
2020-11-23 17:58 [Bug tree-optimization/97961] New: unnecessary moves with __builtin_{add,sub}_overflow_p and __int128 denis.campredon at gmail dot com
2022-11-08 0:14 ` [Bug rtl-optimization/97961] " pinskia at gcc dot gnu.org
@ 2023-01-19 23:23 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-01-19 23:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97961
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 94804. The problem is arguments.
If we do:
```
bool f1(unsigned __int128 *a,unsigned __int128 *b) {
return __builtin_add_overflow_p(*a, *b, (unsigned __int128)0);
}
bool f2(__int128 *a,__int128 *b) {
return __builtin_add_overflow_p(*a, *b, (__int128)0);
}
bool f3(unsigned __int128 *a,unsigned __int128 *b) {
return __builtin_sub_overflow_p(*a, *b, (unsigned __int128)0);
}
bool f4(__int128 *a,__int128 *b) {
return __builtin_sub_overflow_p(*a, *b, (__int128)0);
}
```
We don't get extra mov's.
*** This bug has been marked as a duplicate of bug 94804 ***
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-11-23 17:58 [Bug tree-optimization/97961] New: unnecessary moves with __builtin_{add,sub}_overflow_p and __int128 denis.campredon at gmail dot com
2022-11-08 0:14 ` [Bug rtl-optimization/97961] " pinskia at gcc dot gnu.org
2023-01-19 23:23 ` pinskia at gcc dot gnu.org
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