RFR 10 JDK-8159995: Rename internal Unsafe.compare methods

[David Holmes]

Hi Ron,

On 6/05/2017 5:27 AM, Ron Pressler wrote:
> Hi,
> Please review the following core/hotspot change:
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8159995
> core webrev:
> http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8159995-unsafe-compare-and-swap-to-set-jdk/webrev/
>
> hotspot webrev:
> http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8159995-unsafe-compare-and-swap-to-set-hotspot/webrev/
>
>
> This change is covered by existing tests.
>
> The following renaming was applied:
>
> - compareAndExchange*Volatile -> compareAndExchange*
> - compareAndSwap* -> compareAndSet*

So to clarify this for others, there was confusion surrounding the use 
of "swap" versus "exchange" when both words mean the same thing 
effectively, but the "swap" functions return a boolean, while the 
"exchange" functions return the old value. So we changed "swap" to "set" 
across the APIs - _except_ for the old 
/jdk.unsupported/share/classes/sun/misc/Unsafe.java because we can't 
change its exported API for compatibility reasons.

Given any "swap(exp, new)" function can be implemented as "exchange(exp, 
new) == exp" I'm not sure why we have two complete sets of functions all 
the way through. But I guess that is a different issue. :)

> - weakCompareAndSwap* -> weakCompareAndSet*Plain
> - weakCompareAndSwap*Volatile -> weakCompareAndSet*
>
> At this stage, only method and hotspot intrinsic names were changed;
> node names were left as-is, and may be handled in a separate issue.

Overall looks good for libs and hotspot changes.

One nit I spotted:

src/java.base/share/classes/java/util/concurrent/atomic/AtomicLong.java

+     * compareAndSwap for longs. While the intrinsic compareAndSetLong

compareAndSwap should be compareAndSet

---

All hotspot files need their copyright years updated to 2017 (if not 
already).

As there are hotspot changes this must be pushed using JPRT and 
"-testset hotspot" (but your sponsor should know that :) ).

Thanks,
David

> Ron