[Bug rtl-optimization/126765] [15/16/17 Regression] wrong code with -O2

"pinskia at gcc dot gnu.org via Gcc-bugs" <[email protected]> Mon, 10 Aug 2026 15:48:12 +0000

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126765

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|tree-optimization           |rtl-optimization
             Target|                            |x86_64
   Last reconfirmed|                            |2026-08-10
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

The gimple level looks fine.
In fact without:
    g14 = g14 > (v16u64){};

The code works and the gimple level with and without that looks almost exactly
the same (minus the code for g14 modification).

Adding -fno-ext-dce makes it works ...