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* [Bug target/104525] New: timeout on signed overflow at O0 fwrapv
@ 2022-02-14 8:09 guojiufu at gcc dot gnu.org
2022-02-14 8:29 ` [Bug target/104525] " guojiufu at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: guojiufu at gcc dot gnu.org @ 2022-02-14 8:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104525
Bug ID: 104525
Summary: timeout on signed overflow at O0 fwrapv
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: guojiufu at gcc dot gnu.org
Target Milestone: ---
When checking the case in PR104521, a timeout occurs on the case at ppc64le.
The timeout also occurs with -O0 -fwrapv (without -fwrapv, the signed overflow
which would be a UB). This issue seems to exist for a long time (gcc6).
> 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;
}
}
> gcc -fwrapv -O0 small.c ; timeout -s 9 5 ./a.out
Killed
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/104525] timeout on signed overflow at O0 fwrapv
2022-02-14 8:09 [Bug target/104525] New: timeout on signed overflow at O0 fwrapv guojiufu at gcc dot gnu.org
@ 2022-02-14 8:29 ` guojiufu at gcc dot gnu.org
2022-02-14 8:33 ` pinskia at gcc dot gnu.org
2022-02-14 10:30 ` jakub at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: guojiufu at gcc dot gnu.org @ 2022-02-14 8:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104525
--- Comment #1 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> ---
with "-fsigned-char", the case run ok.
When 'char' is treated as 'unsigned': "c != -4" would not be true is any value
of 'c'.
So, this PR would be invalid.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/104525] timeout on signed overflow at O0 fwrapv
2022-02-14 8:09 [Bug target/104525] New: timeout on signed overflow at O0 fwrapv guojiufu at gcc dot gnu.org
2022-02-14 8:29 ` [Bug target/104525] " guojiufu at gcc dot gnu.org
@ 2022-02-14 8:33 ` pinskia at gcc dot gnu.org
2022-02-14 10:30 ` jakub at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-02-14 8:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104525
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Yes on PowerPC (and ARM and aarch64), plain char is unsigned by default.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/104525] timeout on signed overflow at O0 fwrapv
2022-02-14 8:09 [Bug target/104525] New: timeout on signed overflow at O0 fwrapv guojiufu at gcc dot gnu.org
2022-02-14 8:29 ` [Bug target/104525] " guojiufu at gcc dot gnu.org
2022-02-14 8:33 ` pinskia at gcc dot gnu.org
@ 2022-02-14 10:30 ` jakub at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: jakub at gcc dot gnu.org @ 2022-02-14 10:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104525
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
And on -fsigned-char targets, -fwrapv isn't needed, there isn't signed integer
overflow, because c -= 3 promotes to int, so it is actually
c = (signed char) ((int) c - 3)
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-02-14 10:30 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2022-02-14 8:09 [Bug target/104525] New: timeout on signed overflow at O0 fwrapv guojiufu at gcc dot gnu.org
2022-02-14 8:29 ` [Bug target/104525] " guojiufu at gcc dot gnu.org
2022-02-14 8:33 ` pinskia at gcc dot gnu.org
2022-02-14 10:30 ` jakub at gcc dot gnu.org
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