"root" of ChunkPerFunc chunk

[Stephen Weeks]

Thanks for the explanation.  It all makes sense now (to me).

> But, I've put enough
> effort into the register allocator that it's fairly good about just doing
> register renaming for moves with dead pseudo-regs as the source.  So,
> looking at the assembly, you shouldn't be able to distinguish between the
> optimization happening in the simplifier and in the allocator.  (That's
> why all of the temps in the overflow checks go away.)

So the upshot is that the overflow checks are (in almost all cases) not
interfering with the results of the code generator other than inserting jo's,
right?  If that's the case, then other possible explanations for the slowdown
due to overflow checks are

* The jo instructions
* Missed CPS simplification

Anything else?  Would it be easy to run the benchmarks, once with jo's and once
without, everything else being equal?