[12] RFR(S): 8209697: ARM: Explicit barriers for C1/assembler

[Aleksei Voitylov]

Hi,

please review this patch which adds explicit barriers for C1/assembler 
on ARM similar to how it was done on x86 and Aarch64:

webrev: http://cr.openjdk.java.net/~avoitylov/webrev.8209697.01/
issue: https://bugs.openjdk.java.net/browse/JDK-8209697

here is the issue where this functionality was added on x86 and Aarch64: 
https://bugs.openjdk.java.net/browse/JDK-8209668

Tested by running hotspot tests.

Thanks,

-Aleksei