public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu
@ 2023-05-25 14:15 shaohua.li at inf dot ethz.ch
2023-05-25 18:16 ` [Bug middle-end/109967] " pinskia at gcc dot gnu.org
` (10 more replies)
0 siblings, 11 replies; 12+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2023-05-25 14:15 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Bug ID: 109967
Summary: Wrong code at -O2 on x86_64-linux-gnu
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: shaohua.li at inf dot ethz.ch
Target Milestone: ---
For the following code, gcc trunk at -O2 emits the wrong code. This seems to be
a long latent bug since GCC-7 (I tried gcc-7.4 on compiler explorer, which
still emits the wrong result.)
Compiler explorer: https://godbolt.org/z/YGeWedWq7
$ cat a.c
int printf(const char *, ...);
int a, c;
int main() {
long f[2];
int e = 0;
for (; e < 2; e++) {
{
char g[20];
char *b = g;
int d = 48, e = 0;
while (d && e < 5)
b[e++] = d /= 10;
c = e;
}
f[c - 2 + e] = 1;
}
a = f[0];
printf("%d\n", a);
}
$
$ gcc-tk -O0 a.c && ./a.out
1
$ gcc-tk -O2 a.c && ./a.out
4
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=gcc-tk
COLLECT_LTO_WRAPPER=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-8d5f050dabbf6dd3b992c3b46661848dbcf30d9e/libexec/gcc/x86_64-pc-linux-gnu/14.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --disable-multilib --disable-bootstrap
--enable-languages=c,c++
--prefix=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-8d5f050dabbf6dd3b992c3b46661848dbcf30d9e
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230523 (experimental) (GCC)
$
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
@ 2023-05-25 18:16 ` pinskia at gcc dot gnu.org
2023-05-25 18:19 ` [Bug middle-end/109967] [10/11/12/13/14 Regression] " pinskia at gcc dot gnu.org
` (9 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-05-25 18:16 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |x86_64-linux-gnu
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So if I initialize f the code works.
Note the gimple level code looks the same.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [10/11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
2023-05-25 18:16 ` [Bug middle-end/109967] " pinskia at gcc dot gnu.org
@ 2023-05-25 18:19 ` pinskia at gcc dot gnu.org
2023-05-26 6:01 ` rguenth at gcc dot gnu.org
` (8 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-05-25 18:19 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|Wrong code at -O2 on |[10/11/12/13/14 Regression]
|x86_64-linux-gnu |Wrong code at -O2 on
| |x86_64-linux-gnu
Target Milestone|--- |10.5
Known to work| |6.1.0
Known to fail| |7.1.0
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The problem is the Partition code in expand.
Without the ={0,0}, we get:
Partition 1: size 20 align 16
g f
With we get:
Partition 1: size 20 align 16
g
Partition 0: size 16 align 16
f
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [10/11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
2023-05-25 18:16 ` [Bug middle-end/109967] " pinskia at gcc dot gnu.org
2023-05-25 18:19 ` [Bug middle-end/109967] [10/11/12/13/14 Regression] " pinskia at gcc dot gnu.org
@ 2023-05-26 6:01 ` rguenth at gcc dot gnu.org
2023-06-05 11:13 ` davmac at davmac dot org
` (7 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: rguenth at gcc dot gnu.org @ 2023-05-26 6:01 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P2
Last reconfirmed| |2023-05-26
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [10/11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
` (2 preceding siblings ...)
2023-05-26 6:01 ` rguenth at gcc dot gnu.org
@ 2023-06-05 11:13 ` davmac at davmac dot org
2023-06-05 15:39 ` amonakov at gcc dot gnu.org
` (6 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: davmac at davmac dot org @ 2023-06-05 11:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Davin McCall <davmac at davmac dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |davmac at davmac dot org
--- Comment #3 from Davin McCall <davmac at davmac dot org> ---
-fdisable-tree-cunroll avoids it.
This is the take of someone who is new to poking GCC internals, so take this
with a grain of salt, but:
It looks like cunroll duplicates (partially unrolls, I suppose) the inner loop,
meaning that `g' is live in two disjoint ranges, with a CLOBBER between them.
Then later passes (fre5, but disabling it doesn't seem to help) recognise that
&g and &g are the same in both ranges and so use a single temporary for both.
This confuses cfgexpand (as Andrew Pinski notes) because the memory dereference
of the temporary isn't seen as an access of g (in
add_scope_conflicts()/add_scope_conflicts_1()/visit_conflict()).
I don't understand the IR semantics well enough to know the right fix - perhaps
cunroll should be removing the clobber (does a clobber affect storage lifetime
or only value?), or perhaps cfgexpand should be more conservative when it sees
a memory access.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [10/11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
` (3 preceding siblings ...)
2023-06-05 11:13 ` davmac at davmac dot org
@ 2023-06-05 15:39 ` amonakov at gcc dot gnu.org
2023-07-07 10:45 ` [Bug middle-end/109967] [11/12/13/14 " rguenth at gcc dot gnu.org
` (5 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: amonakov at gcc dot gnu.org @ 2023-06-05 15:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Alexander Monakov <amonakov at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |amonakov at gcc dot gnu.org
--- Comment #4 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
See PR 90348 for the discussion of problematic lifetime semantics.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
` (4 preceding siblings ...)
2023-06-05 15:39 ` amonakov at gcc dot gnu.org
@ 2023-07-07 10:45 ` rguenth at gcc dot gnu.org
2023-07-28 11:47 ` shaohua.li at inf dot ethz.ch
` (4 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: rguenth at gcc dot gnu.org @ 2023-07-07 10:45 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|10.5 |11.5
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
` (5 preceding siblings ...)
2023-07-07 10:45 ` [Bug middle-end/109967] [11/12/13/14 " rguenth at gcc dot gnu.org
@ 2023-07-28 11:47 ` shaohua.li at inf dot ethz.ch
2023-09-25 12:59 ` shaohua.li at inf dot ethz.ch
` (3 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2023-07-28 11:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
--- Comment #6 from Shaohua Li <shaohua.li at inf dot ethz.ch> ---
Bisected to r9-2635-g78ea9abc201
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
` (6 preceding siblings ...)
2023-07-28 11:47 ` shaohua.li at inf dot ethz.ch
@ 2023-09-25 12:59 ` shaohua.li at inf dot ethz.ch
2023-09-25 15:02 ` xry111 at gcc dot gnu.org
` (2 subsequent siblings)
10 siblings, 0 replies; 12+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2023-09-25 12:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
--- Comment #7 from Shaohua Li <shaohua.li at inf dot ethz.ch> ---
This test case does not reproduce anymore on the current trunk. Maybe one of
the recent fixes fixed the underlying issue as well.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
` (7 preceding siblings ...)
2023-09-25 12:59 ` shaohua.li at inf dot ethz.ch
@ 2023-09-25 15:02 ` xry111 at gcc dot gnu.org
2023-09-25 17:27 ` xry111 at gcc dot gnu.org
2024-02-08 18:54 ` jakub at gcc dot gnu.org
10 siblings, 0 replies; 12+ messages in thread
From: xry111 at gcc dot gnu.org @ 2023-09-25 15:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Xi Ruoyao <xry111 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |xry111 at gcc dot gnu.org
--- Comment #8 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to Shaohua Li from comment #7)
> This test case does not reproduce anymore on the current trunk. Maybe one of
> the recent fixes fixed the underlying issue as well.
But we still need to ensure the fix backported into 11/12/13. And there is
still a chance that the issue might be covered up by an unrelated change.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
` (8 preceding siblings ...)
2023-09-25 15:02 ` xry111 at gcc dot gnu.org
@ 2023-09-25 17:27 ` xry111 at gcc dot gnu.org
2024-02-08 18:54 ` jakub at gcc dot gnu.org
10 siblings, 0 replies; 12+ messages in thread
From: xry111 at gcc dot gnu.org @ 2023-09-25 17:27 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Xi Ruoyao <xry111 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=111294
CC| |rguenther at suse dot de
--- Comment #9 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
Bisect shows r14-4089 (the fix for PR111294) either fixes or "covers up" the
issue.
^ permalink raw reply [flat|nested] 12+ messages in thread
* [Bug middle-end/109967] [11/12/13/14 Regression] Wrong code at -O2 on x86_64-linux-gnu
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
` (9 preceding siblings ...)
2023-09-25 17:27 ` xry111 at gcc dot gnu.org
@ 2024-02-08 18:54 ` jakub at gcc dot gnu.org
10 siblings, 0 replies; 12+ messages in thread
From: jakub at gcc dot gnu.org @ 2024-02-08 18:54 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109967
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Plus we have the r14-7274 workaround on the trunk now, wouldn't that make the
problem go away too?
^ permalink raw reply [flat|nested] 12+ messages in thread
end of thread, other threads:[~2024-02-08 18:54 UTC | newest]
Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-05-25 14:15 [Bug c/109967] New: Wrong code at -O2 on x86_64-linux-gnu shaohua.li at inf dot ethz.ch
2023-05-25 18:16 ` [Bug middle-end/109967] " pinskia at gcc dot gnu.org
2023-05-25 18:19 ` [Bug middle-end/109967] [10/11/12/13/14 Regression] " pinskia at gcc dot gnu.org
2023-05-26 6:01 ` rguenth at gcc dot gnu.org
2023-06-05 11:13 ` davmac at davmac dot org
2023-06-05 15:39 ` amonakov at gcc dot gnu.org
2023-07-07 10:45 ` [Bug middle-end/109967] [11/12/13/14 " rguenth at gcc dot gnu.org
2023-07-28 11:47 ` shaohua.li at inf dot ethz.ch
2023-09-25 12:59 ` shaohua.li at inf dot ethz.ch
2023-09-25 15:02 ` xry111 at gcc dot gnu.org
2023-09-25 17:27 ` xry111 at gcc dot gnu.org
2024-02-08 18:54 ` jakub 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).