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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/96563] Failure to optimize loop with
 condition to simple arithmetic
Date: Thu, 19 Aug 2021 23:22:48 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96563

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2020-08-11 00:00:00         |2021-8-19

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So I looked into this a little bit, clang is able to do it because it "unro=
lls"
the loop.

The reason why I say that is if you take:
int f(int x, int y)
{
    int i =3D 0;
    while (i <=3D y)
    {
        if (i =3D=3D x)
            return 8;
        ++i;
    }
    return 4;
}

No compiler is able to optimize this at all.
Which should get us: 4 + ((x <=3D y && x >=3D 0)*4).

Even changing the original 9 to 1000, clang does not do the optimization ..=
..

>although of course it would be nice if it also worked for 99 instead of 9,=
 where we are not going to unroll.
Yes it would but not even clang/LLVM does that :)=