RFR (S): 8035326: Assume non-NULL references in G1CollectedHeap::in_cset_fast_test

[Thomas Schatzl]

Hi all,

  can I get reviews for the following change that lifts the assumption
that the oop* passed to G1CollectedHeap::in_cset_fast_test is non-null,
allowing manual optimization of code.

Almost all uses of G1CollectedHeap::in_cset_fast_test() already made
sure that non-null references are passed to it. The only remaining one,
in G1ParCopyClosure::do_oop_work() actually benefits from lifting this
restriction by allowing removal of some additional checks.

Also removes another superfluous check in the same method.

CR:
https://bugs.openjdk.java.net/browse/JDK-8035326

Webrev:
http://cr.openjdk.java.net/~tschatzl/8035326/webrev/

This is based on the change for 8027559.

Testing:
jprt



Thanks,
  Thomas