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From: "zhendong.su at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/104543] New: wrong code at -O3 on
 x86_64-linux-gnu
Date: Tue, 15 Feb 2022 06:56:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104543

            Bug ID: 104543
           Summary: wrong code at -O3 on x86_64-linux-gnu
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhendong.su at inf dot ethz.ch
  Target Milestone: ---

This appears to be a recent regression.

[588] % gcctk -v
Using built-in specs.
COLLECT_GCC=3Dgcctk
COLLECT_LTO_WRAPPER=3D/local/suz-local/software/local/gcc-trunk/libexec/gcc=
/x86_64-pc-linux-gnu/12.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--prefix=3D/local/suz-local/software/local/gcc-trunk --enable-languages=3Dc=
,c++
--disable-werror --enable-multilib --with-system-zlib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.1 20220215 (experimental) [master r12-7236-g2c3309e3d0f] (=
GCC)=20
[589] %=20
[589] % gcctk -O2 small.c; ./a.out
[590] %=20
[590] % gcctk -O3 small.c
[591] % ./a.out
Aborted
[592] %=20
[592] % cat small.c
int a[3], b, c;
int e() {
  if (!c) {
    for (b =3D 0; b < 3; b++)
      for (c =3D 0; c < 3; c++)
        a[c] ^=3D 1;
    return -1;
  }
  return 0;
}
int main() {
  e();
  if (a[1] !=3D 1)
    __builtin_abort();
  return 0;
}=