[Bug c/90356] Missed optimization for variables initialized to 0.0

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90356

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So the optimization asked for in this case is:
a+0.0+0.0 to just a+0.0