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* [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
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

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