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* [Bug tree-optimization/109638] New: unsigned > 1 ? 0 : n is not optimized to n == 1
@ 2023-04-26 21:00 pinskia at gcc dot gnu.org
2023-04-26 21:03 ` [Bug tree-optimization/109638] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-04-26 21:00 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109638
Bug ID: 109638
Summary: unsigned > 1 ? 0 : n is not optimized to n == 1
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Take:
```
unsigned test_cst (unsigned n)
{
if (n > 1)
n = 0;
return n;
}
unsigned test_cst1 (unsigned n)
{
return (n == 1);
}
```
For gimple at least the second one is smaller. I suspect for x86 the second
version is also faster because it uses sete rather than cmov.
But these 2 functions should produce the same code.
I found this on accident while looking at gcc.dg/tree-ssa/builtin-snprintf-2.c
testcase.
This can only be done for 1 too.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/109638] unsigned > 1 ? 0 : n is not optimized to n == 1
2023-04-26 21:00 [Bug tree-optimization/109638] New: unsigned > 1 ? 0 : n is not optimized to n == 1 pinskia at gcc dot gnu.org
@ 2023-04-26 21:03 ` pinskia at gcc dot gnu.org
2023-04-27 6:42 ` rguenth at gcc dot gnu.org
2023-09-05 4:25 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-04-26 21:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109638
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This should do it, I think:
(simplify
(cond (lt @1 integer_onep@2) integer_zerop @1)
(if (TYPE_UNSIGNED (type))
(convert (eq @1 @2))))
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/109638] unsigned > 1 ? 0 : n is not optimized to n == 1
2023-04-26 21:00 [Bug tree-optimization/109638] New: unsigned > 1 ? 0 : n is not optimized to n == 1 pinskia at gcc dot gnu.org
2023-04-26 21:03 ` [Bug tree-optimization/109638] " pinskia at gcc dot gnu.org
@ 2023-04-27 6:42 ` rguenth at gcc dot gnu.org
2023-09-05 4:25 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2023-04-27 6:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109638
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, but more generally
if (n != x)
n = 0;
return n != 0;
could be handled as well. Or
if (n != x)
n = 0;
return n;
->
return (n == x) * x;
-1 might be another special case that CPUs can efficiently handle.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/109638] unsigned > 1 ? 0 : n is not optimized to n == 1
2023-04-26 21:00 [Bug tree-optimization/109638] New: unsigned > 1 ? 0 : n is not optimized to n == 1 pinskia at gcc dot gnu.org
2023-04-26 21:03 ` [Bug tree-optimization/109638] " pinskia at gcc dot gnu.org
2023-04-27 6:42 ` rguenth at gcc dot gnu.org
@ 2023-09-05 4:25 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-09-05 4:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109638
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Target Milestone|--- |14.0
Status|UNCONFIRMED |RESOLVED
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This got fixed by r14-3036-gb57bd27cb68fdb .
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2023-09-05 4:25 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2023-04-26 21:00 [Bug tree-optimization/109638] New: unsigned > 1 ? 0 : n is not optimized to n == 1 pinskia at gcc dot gnu.org
2023-04-26 21:03 ` [Bug tree-optimization/109638] " pinskia at gcc dot gnu.org
2023-04-27 6:42 ` rguenth at gcc dot gnu.org
2023-09-05 4:25 ` pinskia at gcc dot gnu.org
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