[Bug tree-optimization/126808] Let popcount (X & -X) look through a widening conversion

"pinskia at gcc dot gnu.org via Gcc-bugs" <[email protected]> Thu, 13 Aug 2026 06:35:04 +0000

Newsgroups	gmane.comp.gcc.bugs
Message-ID	<[email protected]/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126808

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |easyhack
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2026-08-13

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Currently it allows for truncation if I read the pattern.
widening requires the inner type being unsigned I think. Otherwise you can get
sign extension so the popcount adds those too for the case of SIGNED MIN being
done.