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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/103399] [12 Regression] Wrong code with -O2
Date: Wed, 24 Nov 2021 02:00:05 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103399

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-11-24

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed reduced testcase:
int t1 =3D -2;
int e(int) __attribute__((noipa));
int e(int f) {
    int t =3D 0;
  for (int d =3D 0; d < f; d ++) {
    for (int c =3D 0; c < ((f ? t1 : 0) ^ t1) + 1; c++)
      t=3D 42;
  }
 return t;
}
int main() {
  unsigned a =3D e(1);
  printf("%u\n", a);
  if (a !=3D 42)
    __builtin_abort ();
}

Note the t1 being negative is important. t1 being global is also important,=
 if
you do a load of t1 before either loop, you end up with working code.

THis is another bswap issue ...=