RFR: Fix CAS-obj predicates and add expected-null-versions for cmpxchg-narrow-oop

[Aleksey Shipilev]

On 07/12/2018 07:10 PM, Roman Kennke wrote:
> I did some experiments and found that the expected-null-optimization in
> the .ad files never actually trigger. Roland's recent aarch64 patch
> seems to solve it, and this is the same for x86:
> 
> http://cr.openjdk.java.net/~rkennke/fixcaspredicates/webrev.01/

It looks good for me.

-Aleksey