[Bug tree-optimization/128638] [16/17 Regression] wrong code at -O3: PRE moves a load past a long long store by TBAA; the executed read is a memcpy

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128638

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2026-11-12
     Ever confirmed|0                           |1
           Keywords|                            |needs-bisection
             Status|UNCONFIRMED                 |NEW
            Summary|[16/17 Regression] wrong    |[16/17 Regression] wrong
                   |code at -O3: PRE moves a    |code at -O3: PRE moves a
                   |load past a long long store |load past a long long store
                   |by TBAA; the executed read  |by TBAA; the executed read
                   |is a memcpy since r12-3918  |is a memcpy

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
r12-3918 looks like broke it in GCC 12 (and then was fixed in GCC 13) but a
change in GCC 16 reintroduce the issue.  The IR before pre is the same so I am
going to assume some change to pre or vn caused it.