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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/106112] New: wrong code at -Os and above on
 x86_64-linux-gnu
Date: Tue, 28 Jun 2022 09:59:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106112

            Bug ID: 106112
           Summary: wrong code at -Os and above 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 regression from 9.*, and affect 10.* and later.=20

[574] % 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/13.0.0/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-sanitizers
--enable-languages=3Dc,c++ --disable-werror --enable-multilib --with-system=
-zlib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 13.0.0 20220628 (experimental) [master r13-1313-gf9764ea128c] (=
GCC)=20
[575] %=20
[575] % gcctk -O1 small.c; ./a.out
[576] %=20
[576] % gcctk -Os small.c
[577] % ./a.out
Aborted
[578] %=20
[578] % cat small.c
int a =3D 5, b, c, d;
unsigned long e =3D 20862985922;
int main() {
  unsigned f =3D 4294967292;
  e =3D e | f;
  c =3D -1 % ((~f ^ 4294967292) - (e - d));
  b =3D ~-~e % ~-d;
  if (b)
    a =3D 0;
  if (a < 1)
    __builtin_abort();
  return 0;
}=