Why is delete_null_pointer_checks called twice

[law@redhat.com]

In message <20030222230257.GM27695@kam.mff.cuni.cz>, Jan Hubicka writes:
 >Hi,
 >the delete_null_pointer_checks is called twice - once before and once
 >after CSE1 pass.  Why we are doing so?  Is this really needed?
The two passes interact with each other.  Removal of null pointers 
leads to more CSE opportunities and some of the CSE simplifications
can lead to more null pointer check removals.

It wasn't deemed worth the effort to iterate until nothing changed or
to run the null pointer check removal after cse2.
jeff