RFR: Fix, improve and refactor matrix barrier on AAarch64

[Aleksey Shipilev]

On 09/14/2017 04:39 PM, Roman Kennke wrote:
> Am 14.09.2017 um 15:52 schrieb Aleksey Shipilev:
>> *) Passing third parameter makes the method consistent with what? shenandoah_write_barrier_post in
>> x86 uses rscratch1 without having it passed via register. g1_write_barrier_post also does not pass
>> rscratch1, but uses it.
> Most with itself. It seemed wrong to me to declare two temp regs as args, then use 3, and use 1
> implicitely. Also, it made experimenting/changing temp reg while debugging easier. Do you want me to
> change it back?

Yeah, change it back: I'd like to be consistent across arches and collectors.

> http://cr.openjdk.java.net/~rkennke/fix-matrix-barrier-aarch64/webrev.01/

Good, except for rscratch1 change.

-Aleksey