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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/103300] New: wrong code at -O3 on
 x86_64-linux-gnu
Date: Wed, 17 Nov 2021 10:17:14 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103300

            Bug ID: 103300
           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 appears to be a recent regression.

[596] % 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 20211117 (experimental) [master r12-5333-g1a15a91a001] (=
GCC)=20
[597] %=20
[597] % gcctk -O2 small.c; ./a.out
[598] %=20
[598] % gcc110 -O3 small.c; ./a.out
[599] %=20
[599] % gcctk -O3 small.c
[600] % ./a.out
Aborted
[601] %=20
[601] % cat small.c
int a, b[2], c, d, e, f;
int g(int h, int i) { return !i || h && i =3D=3D 1 ? 0 : h % i; }
void j() {
  while (1)
    while (1) {
      if (d)
      L:
        if (f)
          break;
      if (e)
        goto L;
      return;
    }
}
int main() {
  j();
  for (c =3D 0; c < 3; c++)
    for (a =3D 0; a < 2; a++)
      if (g(0, b[a]++))
        while (1)
          ;
  if (b[1] !=3D 3)
    __builtin_abort();
  return 0;
}=