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* [Bug tree-optimization/97223] New: Failure to optimize comparison of char arithmetic to comparison
@ 2020-09-28 7:14 gabravier at gmail dot com
2020-09-28 7:33 ` [Bug tree-optimization/97223] Failure to optimize comparison of char arithmetic to single comparison rguenth at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: gabravier at gmail dot com @ 2020-09-28 7:14 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97223
Bug ID: 97223
Summary: Failure to optimize comparison of char arithmetic to
comparison
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gabravier at gmail dot com
Target Milestone: ---
bool f(char x)
{
return x < (char)(x + some_constant);
}
This (where `some-constant` is replaced by a constant expression) can be
optimized to `return x <= (CHAR_MAX - some_constant);`. This optimization is
done by LLVM, but not by GCC.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/97223] Failure to optimize comparison of char arithmetic to single comparison
2020-09-28 7:14 [Bug tree-optimization/97223] New: Failure to optimize comparison of char arithmetic to comparison gabravier at gmail dot com
@ 2020-09-28 7:33 ` rguenth at gcc dot gnu.org
2020-10-31 5:18 ` erozen at microsoft dot com
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2020-09-28 7:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97223
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2020-09-28
Status|UNCONFIRMED |NEW
Keywords| |easyhack
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
It works for 'unsigned char' but not for signed char (or signed short) which
are promoted to 'int' and then shortened to unsigned arithmetic:
return <retval> = (short int) ((unsigned short) x + 5) > x;
there's existing patterns that would need to be amended for the extra
conversion.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/97223] Failure to optimize comparison of char arithmetic to single comparison
2020-09-28 7:14 [Bug tree-optimization/97223] New: Failure to optimize comparison of char arithmetic to comparison gabravier at gmail dot com
2020-09-28 7:33 ` [Bug tree-optimization/97223] Failure to optimize comparison of char arithmetic to single comparison rguenth at gcc dot gnu.org
@ 2020-10-31 5:18 ` erozen at microsoft dot com
2020-11-07 1:54 ` erozen at microsoft dot com
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: erozen at microsoft dot com @ 2020-10-31 5:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97223
Eugene Rozenfeld <erozen at microsoft dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |erozen at microsoft dot com
--- Comment #2 from Eugene Rozenfeld <erozen at microsoft dot com> ---
Created attachment 49475
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49475&action=edit
Proposed patch.
The patch was approved by Richard Beiner:
https://gcc.gnu.org/pipermail/gcc-patches/2020-October/557584.html
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/97223] Failure to optimize comparison of char arithmetic to single comparison
2020-09-28 7:14 [Bug tree-optimization/97223] New: Failure to optimize comparison of char arithmetic to comparison gabravier at gmail dot com
2020-09-28 7:33 ` [Bug tree-optimization/97223] Failure to optimize comparison of char arithmetic to single comparison rguenth at gcc dot gnu.org
2020-10-31 5:18 ` erozen at microsoft dot com
@ 2020-11-07 1:54 ` erozen at microsoft dot com
2021-01-14 21:13 ` erozen at microsoft dot com
2021-08-24 19:38 ` arjun.is at lostca dot se
4 siblings, 0 replies; 6+ messages in thread
From: erozen at microsoft dot com @ 2020-11-07 1:54 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97223
--- Comment #3 from Eugene Rozenfeld <erozen at microsoft dot com> ---
The proposed patch was committed to the trunk by Jeff Law.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/97223] Failure to optimize comparison of char arithmetic to single comparison
2020-09-28 7:14 [Bug tree-optimization/97223] New: Failure to optimize comparison of char arithmetic to comparison gabravier at gmail dot com
` (2 preceding siblings ...)
2020-11-07 1:54 ` erozen at microsoft dot com
@ 2021-01-14 21:13 ` erozen at microsoft dot com
2021-08-24 19:38 ` arjun.is at lostca dot se
4 siblings, 0 replies; 6+ messages in thread
From: erozen at microsoft dot com @ 2021-01-14 21:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97223
--- Comment #4 from Eugene Rozenfeld <erozen at microsoft dot com> ---
The commit that fixed this:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=32ee472864ada44ef05b2a3b087b8ce413bee282
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/97223] Failure to optimize comparison of char arithmetic to single comparison
2020-09-28 7:14 [Bug tree-optimization/97223] New: Failure to optimize comparison of char arithmetic to comparison gabravier at gmail dot com
` (3 preceding siblings ...)
2021-01-14 21:13 ` erozen at microsoft dot com
@ 2021-08-24 19:38 ` arjun.is at lostca dot se
4 siblings, 0 replies; 6+ messages in thread
From: arjun.is at lostca dot se @ 2021-08-24 19:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97223
Arjun Shankar <arjun.is at lostca dot se> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Target Milestone|--- |11.0
Resolution|--- |FIXED
CC| |arjun.is at lostca dot se
--- Comment #5 from Arjun Shankar <arjun.is at lostca dot se> ---
Looks like this was fixed by the time GCC 11 was released. I'm closing this bug
out.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-08-24 19:38 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2020-09-28 7:14 [Bug tree-optimization/97223] New: Failure to optimize comparison of char arithmetic to comparison gabravier at gmail dot com
2020-09-28 7:33 ` [Bug tree-optimization/97223] Failure to optimize comparison of char arithmetic to single comparison rguenth at gcc dot gnu.org
2020-10-31 5:18 ` erozen at microsoft dot com
2020-11-07 1:54 ` erozen at microsoft dot com
2021-01-14 21:13 ` erozen at microsoft dot com
2021-08-24 19:38 ` arjun.is at lostca dot se
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