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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/111282] `a & (b ^ ~a)` (or `a & ~(a ^ b)`)
 not optimized to `a & b` in gimple
Date: Tue, 03 Oct 2023 03:12:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111282

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> Note we will need to detect both `a & (b ^ ~a)` and `a & ~(a ^ b)` since a
> might be comparison too.

Well and that will handle:
```
int f0(int a, int b)
{
        return (~a) & (b ^ a); // ~a & b
}
```
Which we don't currently.

on the RTL level, we currently simplify that to:
(a | b) ^ a


The interesting thing is we do simplify the above in tree via the following
pattern:
/* (X | Y) ^ X -> Y & ~ X */=