[Bug c/80632] error: invalid PHI argument with -O2

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80632

--- Comment #1 from David Binderman <dcb314 at hotmail dot com> ---
This bugs seems to have appeared between revision 247534
and 247578.

I'll have a go at reducing it.