Code motion around labels

[law@redhat.com]

  In message < 10104132059.AA18733@vlsi1.ultra.nyu.edu >you write:
  > Suppose I have a series of labels in a function whose address is taken.
  > I'd argue that we shouldn't be moving a block of code past one of
  > those labels.  But there doesn't currently seem to be any code to
  > prevent that.  Why?
Because if the labels are important from a code motion standpoint,
it should be reflected in the CFG, which is what drives the dataflow
analysis used by code motion.

jeff