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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/103006] New: wrong code at -O2 (only) on
 x86_64-linux-gnu
Date: Sat, 30 Oct 2021 17:45:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103006

            Bug ID: 103006
           Summary: wrong code at -O2 (only) 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 is quite long-latent, affecting GCC 7.* and later.

[856] % 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 20211030 (experimental) [master r12-4804-g75c9fa318e3] (=
GCC)
[857] %
[857] % gcctk -O1 small.c; ./a.out
0
[858] % gcctk -O2 small.c
[859] % ./a.out
0
Aborted
[860] %
[860] % cat small.c
int printf(const char *, ...);
int a, *b, c, e, f;
void g() {
  int *d[7];
  d[6] =3D b =3D (int *)d;
  printf("0\n");
}
int i() {
  for (c =3D 0; c < 2; c++) {
    long h[6][2];
    for (e =3D 0; e < 6; e++)
      for (f =3D 0; f < 2; f++)
        h[e][f] =3D 1;
    if (c) {
      g();
      return h[3][0];
    }
  }
  return 0;
}
int main() {
  if (i() !=3D 1)
    __builtin_abort ();
  return 0;
}=