ARM64: Use macros for saving/restoring registers in assembly.

And for read barrier entrypoints, store LR conventionally
at the top of the frame instead of having a padding there.

Test: m test-art-target on Nexus 9.
Test: m test-art-target with CC on Nexus 9.
Change-Id: I48eaba3ee71c0629d2cc851fdd802590256a0739
1 file changed