public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
* [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) -- links below jump to the message on this page -- 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
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).