RFR (M) [7u60]: Backport of JDK-8014555 G1: Memory ordering problem with Conc refinement and card marking

[Mikael Gerdin]

Hi all,

Please review this backport for the introduction of the StoreLoad barrier into 
G1's write barrier.

The patch from 8 does not apply cleanly to 7u60 since the MacroAssembler code 
was broken out of assembler_*.[ch]pp into macroAssembler_*.[ch]pp.
When I manually edited the patch file to apply the change to the assembler*-
files the patch applies with a line offset so the code has not been changed, 
just moved.

(this fix depends on JDK-8029335, however that change backports cleanly so as 
per the process no extra code review is required for the backport.)

Webrev: http://cr.openjdk.java.net/~mgerdin/8014555-backport/webrev.0
Bug link: https://bugs.openjdk.java.net/browse/JDK-8014555

/Mikael