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From: "zhendong.su at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/114902] New: wrong code at -O3 with
 "-fno-tree-vrp -fno-expensive-optimizations -fno-tree-dominator-opts" on
 x86_64-linux-gnu
Date: Tue, 30 Apr 2024 22:13:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114902

            Bug ID: 114902
           Summary: wrong code at -O3 with "-fno-tree-vrp
                    -fno-expensive-optimizations -fno-tree-dominator-opts"
                    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 as it doesn't reproduce with 13.2.=20

Compiler Explorer: https://godbolt.org/z/7ssP5W57E


[587] % 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/15.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--enable-checking=3Dyes --prefix=3D/local/suz-local/software/local/gcc-trunk
--enable-sanitizers --enable-languages=3Dc,c++ --disable-werror --enable-mu=
ltilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 15.0.0 20240430 (experimental) (GCC)=20
[588] %=20
[588] % gcctk -O3 -fno-tree-vrp -fno-expensive-optimizations
-fno-tree-dominator-opts small.c
[589] % ./a.out
Floating point exception
[590] %=20
[590] % gcctk -O3 small.c; ./a.out
[591] %=20
[591] % cat small.c
volatile int a, c;
unsigned b =3D 1;
int main() {
  for (; a < 2; a++)
    if (a)
      for (; c < 2; c++) {
        int d =3D -1, e =3D -(-d & ~b), f =3D -~(1 && b % a);
        a % f || a;
        if (d <=3D e)
          e =3D a;
        a =3D e;
      }
  return 0;
}=