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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/101179] y % (x ? 16 : 4) and y % (4 << (2 *
 (bool)x)) produce different code
Date: Wed, 23 Jun 2021 18:05:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101179

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
But here are two other functions which all should have the same code gen as=
 the
original two:
int f3(int y)
{
    const bool x =3D y % 100 =3D=3D 0;
    return (x ? y%16 : y%4) =3D=3D 0;
}

int f4(int y)
{
    const bool x =3D y % 100 =3D=3D 0;
    return (x ? (y%16) =3D=3D 0 : (y%4) =3D=3D 0);
}

Only the last one produces the best code.=