[aarch64-port-dev ] RFR: backport volatile put/get and CAS optimization to JDK8

[Andrew Dinn]

Here is a webrev against the latest aarch64-port-dev/jdk8/hotspot for
review:

  http://cr.openjdk.java.net/~adinn/jdk8volcasopt/webrev.00

It backports the jdk9-aarch64 optimizations which use ldar and stlr for
volatile gets and puts and unsafe CAS operations to jdk8-aarch64

So far, I have tested it (successfully) by eyeballing generated code for
some hand cranked tests that use volatiles and CASes in all 5 relevant
GC configurations (see below ***) and also running by netbeans and
eyeballing generated hash table code.

I am currently running jcstress to fully test it on a Mustang in all GC
configs.

Ed, would you be able to check that jcstress works fine on other hardware?

*** GC configs are
    -XX:+UseConcMarkSweepGC -XX:+UseCondCardMark
    -XX:+UseConcMarkSweepGC -XX:-UseCondCardMark
    -XX:+UseG1GC
    -XX:+UseParallelGC -XX:+UseCondCardMark
    -XX:+UseParallelGC -XX:-UseCondCardMark

regards,


Andrew Dinn
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