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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/112723] [11/12/13/14 Regression] Missed
 optimization for invariants 'c+c' when c += -2147483647-1 and c is a global
 variable
Date: Thu, 28 Mar 2024 17:18:23 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112723

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
gimple-ssa-strength-reduction definitely should be improved to handle this =
case
where it should understand that (a+CSTWITHLASTBITSET)*2 can be done as
a*2+NEWCST if the type can wrap. Only can do that if wrapping rather than if
overflow is undefined.

For a non-signed case which should be handled:
```
unsigned a, b, c;
void test() {
    a =3D c + c;
    c +=3D -2147483648u;
    b =3D c + c;
}
```

Maybe I will look at this for GCC 15. It might improve other code ...=