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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/85234] missed optimisation opportunity for
 (~x >> CST)!=0 is not optimized to   (((unsigned)x) < ~((1<<CST) - 1))
Date: Tue, 20 Jul 2021 23:44:03 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D85234

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|missed optimisation         |missed optimisation
                   |opportunity for (~x >> n) ? |opportunity for (~x >>
                   |a : b with n, a, b          |CST)!=3D0 is not optimized=
 to
                   |constants                   |  (((unsigned)x) <
                   |                            |~((1<<CST) - 1))
          Component|middle-end                  |tree-optimization

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
int f(int x)
{
    return (~x >> 3) !=3D0;
}
int f2(int x)
{
    return (((unsigned)x) < ~((1<<3) - 1));
}

The above is what LLVM does really=