[Bug rtl-optimization/66489] combine fails to merge insns if some are reused later on

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66489

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This was the reason why the pass on the tree level to fused multiply add was
added.  Maybe we can do the same.

Do you know how often this shows up?