What kind of bug is it?  It's a timeout bug.  Of course.
Avoid an infinite loop in realias analysis if the PTS computation
isn't quite right.  This is safe, because the PTT is always a
conservative approximation, and means that we have a monotonic update
regardless of what poiontsToSetForExpr actually does.
Yet another timeout bug.
Improve CDG a littel by including information from assertion
annotations.
Whoops: CDG optimisation can invalidate the predecessor map, which
then confuses alias analysis later on.  Fix that.
The use-of-undefined warning in realias is loud and uninformative.
Get rid of it.
Lots of extra debug for breadthFirstEnumBackwards.
Minor improvement in debugging for realias.
The condition to traverse the edge A->B can be calculated by either
taking the condition to get to B and adding in the condition
associated with the edge or by taking the condition to get to A and
adding the edge condition.  Doing the latter tends to give better
results, so switch over.
Turn down some debug a bit.
Make sure that the CDG gets the sense of assertions right.
Marginal improvements to debuggability.
New optimisation pass: if we're in SSA mode, we can safely pull all
ImportRegisters up to the root, which allows more canonicalisation.
Remove a bad assertion.