The warp-opkill pass is generating incorrect code. It is placing an
OpUnreachable at the end of a basic block, when the block can be
reached. We can't reach the end of the block, but we can reach the end.
Instead we will add a return instruction.
Fixes#2875.
We are no able to inline OpKill instructions into a continue construct.
See #2433. However, we have to be able to inline to correctly do
legalization. This commit creates a pass that will wrap OpKill
instructions into a function of its own. That way we are able to inline
the rest of the code.
The follow up to this will be to not inline any function that contains
an OpKill.
Fixes#2726