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* [Bug tree-optimization/115697] New: Miscompilation with -fgraphite-identity at -O2
@ 2024-06-28 10:14 michael at orlitzky dot com
2024-06-28 11:47 ` [Bug tree-optimization/115697] [11/12/13/14/15 Regression] " xry111 at gcc dot gnu.org
2024-06-28 21:01 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: michael at orlitzky dot com @ 2024-06-28 10:14 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115697
Bug ID: 115697
Summary: Miscompilation with -fgraphite-identity at -O2
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: michael at orlitzky dot com
Target Milestone: ---
While debugging a test failure in the flint library
(https://github.com/flintlib/flint/issues/2029), we seem to have discovered a
miscompilation. Fredrik Johansson was able to come up with a minimal
reproducer. This may be a duplicate of bug 47048, but having more reproducible
test cases never hurts.
$ gcc-15 -O2 -Wall -Wextra main.c
$ ./a.out
6 4 1
$ gcc-15 -O2 -fgraphite-identity -Wall -Wextra main.c
$ ./a.out
3 2 1
$ cat main.c
#include <stdio.h>
void
shift(long * c, long n)
{
long i, j;
if (n <= 62)
{
for (i = n - 2; i >= 0; i--)
for (j = i; j < n - 1; j++)
c[j] += c[j + 1];
}
}
int main(void)
{
long c[3];
volatile long n = 3;
c[0] = 3;
c[1] = 2;
c[2] = 1;
shift(c, n);
printf("%ld %ld %ld\n", c[0], c[1], c[2]);
}
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/115697] [11/12/13/14/15 Regression] Miscompilation with -fgraphite-identity at -O2
2024-06-28 10:14 [Bug tree-optimization/115697] New: Miscompilation with -fgraphite-identity at -O2 michael at orlitzky dot com
@ 2024-06-28 11:47 ` xry111 at gcc dot gnu.org
2024-06-28 21:01 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: xry111 at gcc dot gnu.org @ 2024-06-28 11:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115697
Xi Ruoyao <xry111 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |xry111 at gcc dot gnu.org
Known to fail| |11.1.0
Summary|Miscompilation with |[11/12/13/14/15 Regression]
|-fgraphite-identity at -O2 |Miscompilation with
| |-fgraphite-identity at -O2
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2024-06-28
Keywords| |needs-bisection
Known to work| |10.5.0
--- Comment #1 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
Confirmed.
- Code from GCC 6 - 10 outputs "6 4 1" correctly.
- Code from GCC 11 - 14 outputs "3 2 1".
- Code from GCC 5 crashes with SIGFPE.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/115697] [11/12/13/14/15 Regression] Miscompilation with -fgraphite-identity at -O2
2024-06-28 10:14 [Bug tree-optimization/115697] New: Miscompilation with -fgraphite-identity at -O2 michael at orlitzky dot com
2024-06-28 11:47 ` [Bug tree-optimization/115697] [11/12/13/14/15 Regression] " xry111 at gcc dot gnu.org
@ 2024-06-28 21:01 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-06-28 21:01 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115697
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |11.5
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2024-06-28 21:01 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2024-06-28 10:14 [Bug tree-optimization/115697] New: Miscompilation with -fgraphite-identity at -O2 michael at orlitzky dot com
2024-06-28 11:47 ` [Bug tree-optimization/115697] [11/12/13/14/15 Regression] " xry111 at gcc dot gnu.org
2024-06-28 21:01 ` pinskia at gcc dot gnu.org
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