[Bug rtl-optimization/126560] [15/16/17 Regression] wrong code at -O3 on aarch64

"pinskia at gcc dot gnu.org via Gcc-bugs" <[email protected]> Sun, 02 Aug 2026 05:32:15 +0000

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126560

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|target                      |rtl-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2026-08-02
     Ever confirmed|0                           |1

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

Looks like an ext_dce issue.
(insn 111 50 51 9 (set (reg:SI 140 [ prephitmp_32 ])
        (zero_extend:SI (subreg:QI (reg:SI 108 [ pretmp_47 ]) 0))) 114
{*zero_extendqisi2_aarch64}
     (nil))

Being turned into:
(insn 111 50 51 9 (set (reg:SI 140 [ prephitmp_32 ])
        (zero_extend:SI (subreg:QI (reg:SI 108 [ pretmp_47 ]) 0))) 114
{*zero_extendqisi2_aarch64}
     (nil))