RFR: Cherry-pick JDK-8203628: Optimize (masked) byte memory comparisons on x86

[Zhengyu Gu]

Okay.

-Zhengyu

On 05/30/2018 12:01 PM, Aleksey Shipilev wrote:
> http://cr.openjdk.java.net/~shade/shenandoah/pick-8203628/webrev.01/
> 
> This is something we have upstreamed, and now it comes back in this form. Let's cherry-pick to
> simplify the merge.
> 
> Testing: hotspot_fast_gc_shenandoah
> 
> Thanks,
> -Aleksey
>