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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109638] New: unsigned > 1 ? 0 : n is not optimized to n == 1
Date: Wed, 26 Apr 2023 21:00:31 +0000 [thread overview]
Message-ID: <bug-109638-4@http.gcc.gnu.org/bugzilla/> (raw)
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.
next reply other threads:[~2023-04-26 21:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-26 21:00 pinskia at gcc dot gnu.org [this message]
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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