[Bug tree-optimization/121488] A missing BIT_FIELD_REF mem optimization due to type differences

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121488

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I should mention `-O2 -mavx2` on x86_64.

For some reason without -mavx2, we can optimize it on x86_64 due some changes
in forwprop2. On aarch64 that forwprop does not happen either.