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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/107269] New: wrong code at -O1 and above with
 "-fno-tree-ccp" on x86_64-linux-gnu
Date: Fri, 14 Oct 2022 18:22:20 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107269

            Bug ID: 107269
           Summary: wrong code at -O1 and above with "-fno-tree-ccp" 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.

Compiler Explorer: https://godbolt.org/z/WdcsavxTh


[593] % 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
--enable-checking=3Dyes --prefix=3D/local/suz-local/software/local/gcc-trunk
--enable-sanitizers --enable-languages=3Dc,c++ --disable-werror --enable-mu=
ltilib
--with-system-zlib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 13.0.0 20221014 (experimental) [master r13-3307-g8efc38347a7] (=
GCC)=20
[594] %=20
[594] % gcctk -O1 small.c; ./a.out
[595] %=20
[595] % gcctk -O1 -fno-tree-ccp small.c
[596] % ./a.out
Floating point exception
[597] %=20
[597] % cat small.c
int a, b, f;
char c =3D 3;
unsigned d =3D 1;
short e;
int main() {
  int h =3D 2357999721;
  char i =3D a =3D 3;
  for (; a >=3D 0; a--) {
    int *j =3D &h;
    char k =3D i || c;
    short l =3D ~h;
    b =3D ~(d % h);
    f =3D ~i / b;
    if (h >=3D -1936967575) {
      int m =3D h / d / 110000000 ^ (f & c);
      short n =3D c;
      if (h <=3D -1936967575)
        n =3D e;
      h =3D m;
      c =3D ~(n + f);
      d =3D -1;
    }
    i =3D ~l - k;
  }
  return 0;
}=