RFR: [11u] 8216350: AArch64: monitor unlock fast path not called

[Nick Gasson]

Hi,

Please review this backport of the fix for 8216350 to 11u:

Original bug: https://bugs.openjdk.java.net/browse/JDK-8216350
Webrev: http://cr.openjdk.java.net/~ngasson/8216350/webrev.11u.0/

Justification is that it improves performance in non-micro benchmarks 
(SPECjbb).

The original patch has been modified slightly so it applies cleanly on 
11u. Most of the conflicts were from checking the EmitSync flag in 11 
which has been removed in 12/13. I've also removed the change to the 
micro benchmark as these files are not in 11u.

Testing: jtreg, jcstress (*), and ran the micro benchmark to check the 
performance regression is fixed.

* Note that some jcstress tests are failing on 11u (with and without 
this patch). You can reproduce this easily by running jcstress with "-t 
varHandles.*GetAndSetTest". This was fixed in 12/13 by:

   8211320: Aarch64: unsafe.compareAndSetByte() and 
unsafe.compareAndSetShort() c2 intrinsics broken with negative expected 
value

I suggest we also backport the above to 11u?

Thanks,
Nick