[Bug tree-optimization/55761] process_assignment assumes -1 can be created

[pa...@matos-sorge.com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55761

--- Comment #12 from Paulo J. Matos <pa...@matos-sorge.com> ---
Also, I haven't touched tree-tailcall.c on my patches but I can't see why you
would need to do it.