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* [Bug c/110732] New: Wrong code at -Os on x86_64-linux-gnu (recent regression)
@ 2023-07-19 7:36 shaohua.li at inf dot ethz.ch
2023-07-19 7:41 ` [Bug c/110732] " pinskia at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: shaohua.li at inf dot ethz.ch @ 2023-07-19 7:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110732
Bug ID: 110732
Summary: Wrong code at -Os on x86_64-linux-gnu (recent
regression)
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: ---
This looks like a recent regression. gcc at -Os produces the wrong code.
Compiler explorer: https://godbolt.org/z/WWdxfzPrc
$ cat a.c
int printf(const char *, ...);
int a;
char c[] = {0, 0, -4L};
char d, e;
int main() {
int f;
int *g = &a;
*g = 1;
for (; e <= 2; e++)
for (;;) {
{
{
int b = c[e];
f = b < 0 ? b : b >> 6;
}
d = f && a;
}
break;
}
printf("%d\n", d);
}
$
$ gcc-tk -O0 a.c && ./a.out
1
$ gcc-tk -Os a.c && ./a.out
-1
$
$ gcc-tk -v
Using built-in specs.
COLLECT_GCC=gcc-tk
COLLECT_LTO_WRAPPER=/zdata/shaoli/compilers/ccbuilder-compilers/gcc-322d17ae51ea0137167424e0018d7fa355948f9f/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-322d17ae51ea0137167424e0018d7fa355948f9f
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.0.0 20230711 (experimental) (GCC)
$
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug c/110732] Wrong code at -Os on x86_64-linux-gnu (recent regression)
2023-07-19 7:36 [Bug c/110732] New: Wrong code at -Os on x86_64-linux-gnu (recent regression) shaohua.li at inf dot ethz.ch
@ 2023-07-19 7:41 ` pinskia at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-07-19 7:41 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110732
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |DUPLICATE
Status|UNCONFIRMED |RESOLVED
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
phiopt match-simplify trying:
b_15 >= 0 ? iftmp.1_16 : 1
Matching expression match.pd:2006, gimple-match-5.cc:23
Matching expression match.pd:2006, gimple-match-5.cc:23
Applying pattern match.pd:5311, gimple-match-1.cc:3381
Applying pattern match.pd:1393, gimple-match-2.cc:7726
Applying pattern match.pd:1901, gimple-match-4.cc:680
Applying pattern match.pd:4781, gimple-match-10.cc:16483
Folded into the sequence:
_11 = b_15 >= 0;
_20 = (int) _11;
_19 = b_15 < 0;
_26 = (int) _19;
_18 = iftmp.1_16 | _26;
statement un-sinked:
iftmp.1_16 = b_15 >> 6;
Before:
# RANGE [irange] int [0, 1]
iftmp.1_16 = b_15 >> 6;
Dup of bug 110252.
*** This bug has been marked as a duplicate of bug 110252 ***
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-07-19 7:36 [Bug c/110732] New: Wrong code at -Os on x86_64-linux-gnu (recent regression) shaohua.li at inf dot ethz.ch
2023-07-19 7:41 ` [Bug c/110732] " pinskia at gcc dot gnu.org
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