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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/91213] Missed optimization: (sub X Y) -> (xor X Y)
 when Y <= X and isPowerOf2(X + 1)
Date: Mon, 29 Aug 2022 15:25:44 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D91213

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to rdapp from comment #6)
> What's the mechanism to get range information at RTL level? The only rela=
ted
> thing I saw in (e.g.) simplify-rtx.cc is nonzero_bits and this does not s=
eem
> to be propagated from gimple.

You can get it at expand time, is that enough? Which I think the patch I ha=
d.

As far as nonzero_bits there is a project being working by Segher but I don=
't
know the status of it.=