RFR: 8159063: aarch64: optimise unaligned array copy long

[Edward Nevill]

Hi,

Please review the following webrev

http://cr.openjdk.java.net/~enevill/8159063/webrev

JIRA Issue: https://bugs.openjdk.java.net/browse/JDK-8159063

This webrev optimises the code generate for copy array long to ensure
that loads/stores are always done on 128 bit boundaries.

This can be switched on/off with -XX:+/-AvoidUnalignedAccesses which is
set by default for those partners where there is a benefit.

The following is my test case.

http://cr.openjdk.java.net/~enevill/8159063/ArrayCopyAligned.java

To run do

java ArrayCopyAligned <iters> <start> <end> <step>

This shows the results for partners A and B with the parameters 10 0
1024 32.

http://cr.openjdk.java.net/~enevill/8159063/arraycopy.pdf

OK to push to jdk8u now (and later to jdk9)?

Thanks,
Ed.