[13] RFR(XS):8226287: Make process_users_of_allocation handle gc barriers

[Roland Westrelin]

> _igvn.replace_node(ctrl_proj, init->in(TypeFunc::Control)) should always 
> work.
>
> I added the checks to be able to keep the 
> "assert(init->in(TypeFunc::Control) == _fallthroughcatchproj, 
> "allocation control projection");"
>
> Mostly because it could be nice to catch any other malformed control 
> flow here. And from the beginning I was a bit unsure if there where 
> other code paths that assumes the 
> alloc->proj->catch->catchproj->initialize pattern.
>
> I can remove it if you want to. It definitely gets easier to read.

It makes sense now. I think it would be better to not make:

_igvn.replace_node(ctrl_proj, init->in(TypeFunc::Control));

conditional but modify the assert:

assert(init->in(TypeFunc::Control) == _fallthroughcatchproj ||
(bs->is_gc_barrier_node(init->in(TypeFunc::Control ...)

Otherwise it seems that sometimes we don't remove the init barrier but
it's unclear why. Also a comment would be nice.

Roland.