[aarch64-port-dev ] [8u] Patches needed in 8u aarch64

[Wang Zhuo(Zhuoren)]

Hello, very glad to see aarch64 support integrated in 8u.
Alibaba ported a number of online applications last year, and we found these patches were useful for current 8u aarch64.
P1: 
JDK-8069191:moving predicate out of loops may cause array accesses to bypass null check
Link: https://bugs.openjdk.java.net/browse/JDK-8069191
This bug caused a lot of applications crashed during our test, easy to reproduce. I think it is a must-have.

P2:
JDK-8155949: Support relaxed semantics in cmpxchg
https://bugs.openjdk.java.net/browse/JDK-8155949

JDK-8157904: Atomic::cmpxchg for jbyte is missing a fence on initial failure
https://bugs.openjdk.java.net/browse/JDK-8157904

JDK-8196064 : AArch64: Merging ld/st into ldp/stp in macro-assembler
https://bugs.openjdk.java.net/browse/JDK-8196064

JDK-8183543: Aarch64: C2 compilation often fails with "failed spill-split-recycle sanity check"
https://bugs.openjdk.java.net/browse/JDK-8183543

The above four patches can improve performance. 
Please give some comments.

Regards,
Zhuo