RFR: Barriers for locks rewrite

[Roman Kennke]

Am Montag, den 10.10.2016, 09:28 +0100 schrieb Andrew Haley:
> On 10/10/16 09:14, Roman Kennke wrote:
> > 
> > http://cr.openjdk.java.net/~rkennke/lockbarriers/webrev.00/
> > 
> > Ok?
> 
> What to do about AArch64?

Good point!

Not doing anything should be safe & conservative.

If we want to do similar improvement as on x86, seek out all the places
where we modify the mark word (e.g. grep for mark_offset_in_bytes...
hopefully we haven't used any 0s in there ;-) ) and place an
appropriate barrier right before that. In x86, the tricky part was to
get the interpreter_write_barrier() code correct for use with c1. (Side
note: I would like to use the stub that's used by C2 for C1 and
interpreter too... should not be hard). And then remove the early
write-barriers in the monitorenter/exit code for interpreter and c1.

Roman