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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/100934] New: wrong code at -O3 on
 x86_64-linux-gnu
Date: Sun, 06 Jun 2021 20:49:44 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100934

            Bug ID: 100934
           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: ---

It seems to affect all versions since GCC 8.4 (but not GCC 8.3).=20

[583] % 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/12.0.0/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 12.0.0 20210606 (experimental) [master revision
28c62475050:a6bc26893ec:a589877a0036fc2f66b7a957859940c53efdc7c9] (GCC)=20
[584] %=20
[584] % gcctk -O2 small.c; ./a.out
[585] %=20
[585] % gcctk -O3 small.c
[586] % ./a.out
Segmentation fault
[587] %=20
[587] % cat small.c
int a, b, c, d, e;
int main() {
  int f =3D 0, g =3D 0;
  for (; f < 2; f++) {
    int h, i;
    for (h =3D 0; h < 2; h++) {
      b =3D e =3D g ? a % g : 0;
      c =3D d;
      for (i =3D 0; i < 1; i++)
        g =3D 0;
      for (; g < 2; g++)
        ;
    }
  }
  return 0;
}=