Treegion has two interesting features:
 1. Treegion + Denpendence Height Scheduling gives a
scheduling tech independent of profiling.
 2. Scheduling in the entire treegion.

I think the idea of scheduling all the instructions in the
entire treegion is too aggressive. The scheduling of rarely
executed instructions may consume unnecessary execution time.
Moreover, we have to repair it's damage. The waste happens
frequently. The idea of Global Weight Treegion Scheduling
gives a clue to the solution of the problem. But it returns to
superblock somehow. (BTW, because of the tree structure of
treegion, the bb weight reveals lots of execution info.) The
scheduling of rarle executed instructions is a possible benifit.
At the same time, it is something the scheduler should really be
careful to do.

Besides execution frequency, data dependence, I think scheduling
should also consider the penalty. The scheduler schedules rarely
executed instruction only when it requires no or very little
extra effort. This is dependent on architecture. But the accurate
description is hardly available.

Shaojie Wang