RFR (S) #2: CR 8004318/JEP 171: Fences intrinsics

[Aleksey Shipilev]

Hi,

This is the updated webrev for Fences intrinsics [1]:
 http://shipilev.net/pub/jdk/hotspot/fences/webrev-2/

It includes the review fixes from Christian.

Testing:
  - built and tested in Linux x86_64
  - java-concurrency-torture [2] Fences tests [3] are passing
  - JPRT passes on all platforms, with no regressions [*]

I think this patch is ready for the inclusion, and we need a sponsor for
it. Original JEP still needs to be pushed to "Funded" state in order to
get clearance for push though.

-Aleksey.

[1] http://openjdk.java.net/jeps/171
[2] https://github.com/shipilev/java-concurrency-torture
[3] java -jar concurrency-torture.jar -t ".*fences.*"
[*] There is a single unrelated failure, which is reproduced on clean
hotspot-comp build as well (langtools/DefaultMethodRegressionTests)