public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug tree-optimization/104521] New: wrong code at -O2 and -O3 on x86_64-linux-gnu
@ 2022-02-13 17:59 zhendong.su at inf dot ethz.ch
2022-02-13 18:00 ` [Bug tree-optimization/104521] " zhendong.su at inf dot ethz.ch
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: zhendong.su at inf dot ethz.ch @ 2022-02-13 17:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104521
Bug ID: 104521
Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zhendong.su at inf dot ethz.ch
Target Milestone: ---
It appears to be a recent regression and is very likely related to PR 104519.
But opposite to PR 104519, it doesn't reproduce at -Os, and instead reproduces
at -O2 and -O3. At -Os, there is a spurious UB warning though.
[611] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/suz-local/software/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/12.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--prefix=/local/suz-local/software/local/gcc-trunk --enable-languages=c,c++
--disable-werror --enable-multilib --with-system-zlib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.1 20220213 (experimental) [master r12-7216-g7e204bd2f18] (GCC)
[612] %
[612] % gcctk -Os small.c; ./a.out
small.c: In function ‘main’:
small.c:6:30: warning: iteration 42 invokes undefined behavior
[-Waggressive-loop-optimizations]
6 | for (c = 0; c != -4; c -= 3) {
| ^~
small.c:6:21: note: within this loop
6 | for (c = 0; c != -4; c -= 3) {
| ~~^~~~~
[613] %
[613] % gcctk -O2 small.c
[614] % timeout -s 9 5 ./a.out
Killed
[615] %
[615] % cat small.c
char a, b, c;
int main() {
unsigned char d = 1;
while (1) {
if (c >= a) {
for (c = 0; c != -4; c -= 3) {
while (!d)
b = 0;
continue;
}
}
d = ~a;
if (!d)
continue;
return 0;
}
}
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/104521] wrong code at -O2 and -O3 on x86_64-linux-gnu
2022-02-13 17:59 [Bug tree-optimization/104521] New: wrong code at -O2 and -O3 on x86_64-linux-gnu zhendong.su at inf dot ethz.ch
@ 2022-02-13 18:00 ` zhendong.su at inf dot ethz.ch
2022-02-13 22:29 ` [Bug tree-optimization/104521] [12 Regression] wrong code at -O2 and -O3 with char as loop induction variable pinskia at gcc dot gnu.org
2022-02-13 22:30 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: zhendong.su at inf dot ethz.ch @ 2022-02-13 18:00 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104521
--- Comment #1 from Zhendong Su <zhendong.su at inf dot ethz.ch> ---
>From Compiler Explorer: https://godbolt.org/z/Y37Wo9e8c
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/104521] [12 Regression] wrong code at -O2 and -O3 with char as loop induction variable
2022-02-13 17:59 [Bug tree-optimization/104521] New: wrong code at -O2 and -O3 on x86_64-linux-gnu zhendong.su at inf dot ethz.ch
2022-02-13 18:00 ` [Bug tree-optimization/104521] " zhendong.su at inf dot ethz.ch
@ 2022-02-13 22:29 ` pinskia at gcc dot gnu.org
2022-02-13 22:30 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-02-13 22:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104521
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|wrong code at -O2 and -O3 |[12 Regression] wrong code
|on x86_64-linux-gnu |at -O2 and -O3 with char as
| |loop induction variable
Target Milestone|--- |12.0
Known to work| |11.2.0
Known to fail| |12.0
Keywords| |diagnostic, wrong-code
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I suspect it was introduced by r12-6844-gf1af8528d3 .
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/104521] [12 Regression] wrong code at -O2 and -O3 with char as loop induction variable
2022-02-13 17:59 [Bug tree-optimization/104521] New: wrong code at -O2 and -O3 on x86_64-linux-gnu zhendong.su at inf dot ethz.ch
2022-02-13 18:00 ` [Bug tree-optimization/104521] " zhendong.su at inf dot ethz.ch
2022-02-13 22:29 ` [Bug tree-optimization/104521] [12 Regression] wrong code at -O2 and -O3 with char as loop induction variable pinskia at gcc dot gnu.org
@ 2022-02-13 22:30 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-02-13 22:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104521
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 104519.
*** This bug has been marked as a duplicate of bug 104519 ***
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-02-13 22:30 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-02-13 17:59 [Bug tree-optimization/104521] New: wrong code at -O2 and -O3 on x86_64-linux-gnu zhendong.su at inf dot ethz.ch
2022-02-13 18:00 ` [Bug tree-optimization/104521] " zhendong.su at inf dot ethz.ch
2022-02-13 22:29 ` [Bug tree-optimization/104521] [12 Regression] wrong code at -O2 and -O3 with char as loop induction variable pinskia at gcc dot gnu.org
2022-02-13 22:30 ` pinskia at gcc dot gnu.org
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).