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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/106244] Failure to optimize (1 << x) & 1 to
 `x == 0` if separated into multiple statements
Date: Sun, 10 Jul 2022 20:22:31 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106244

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-07-10
     Ever confirmed|0                           |1
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Actually it is not optimized if it was in one statement:
int8_t f1(int8_t x)
{
    return ((int8_t)(1 << x)) & 1;
}

The IR has:
  _4 =3D (int) x_1(D);
  _5 =3D 1 << _4;
  sh_6 =3D (int8_t) _5;
  _7 =3D sh_6 & 1;

We optimize directly "(1 << x) & 1" but not with a cast.=