[Bug tree-optimization/121279] [14/15/16 Regression] wrong code due to load of a bool from an union being pulled out of loop

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121279

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
One idea is to have
gimple_needing_rewrite_undefined/rewrite_to_defined_unconditional do the
rewriting for moving BOOLEAN_TYPE loads.

The other idea is to reject moving loads of booleans. 

The first idea is better but I don't know if it is just boolean types would
cause these kind of issues; bitfield and BitInt loads remove the other bits so
it is not an issue there.