RFR (S) 8229419: Shenandoah: Cleanup LRB strength selector code

[Aleksey Shipilev]

On 8/12/19 7:11 PM, Aleksey Shipilev wrote:
> RFE:
>  https://bugs.openjdk.java.net/browse/JDK-8229419
>  https://cr.openjdk.java.net/~shade/8229419/webrev.01/

https://cr.openjdk.java.net/~shade/8229419/webrev.02/

Last minute cleanup:
 - invert Op_CmpP condition from && to ||, makes simpler statement;
 - return strength=NONE from "Do not need barriers" block;
 - a bit better grouping;

Still passes hotspot_gc_shenandoah

-- 
Thanks,
-Aleksey