Code motion around labels

[law@redhat.com]

  In message < 10104132128.AA18847@vlsi1.ultra.nyu.edu >you write:
  > Well I don't see anyplace where it consults the CFG either, nor am
  > I sure how you'd encode the restriction in the CFG.  What did you
  > mean?
Presumably you're talking about gcse/lcm?  Look at the code in lcm.c
and sbitmap.c

Look for stuff like sbitmap_{union,intersection}_of_{preds,succs} and
how they're used to merge information from multiple edges at joins
in the CFG.

The information you want to encode in the CFG is from what points are
those labels reachable.  ie, compute an accurate CFG and the code motion
algorithms will DTRT.  You may want to refer to recent texts which
describe how these algorithms work.