[Bug c/66348] Simple loop has only lower half of the 64-bit counter initialized correctly

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66348

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I suspect there is an alias violation here rather what is described. 


In x86_64, almost all of the instructions which act on 32bit half of the
registers will zero extend. That includes xorl.