RFR: 8073093: AARCH64: C2 generates poor code for ByteBuffer accesses

[Andrew Haley]

java.​nio.​DirectByteBuffer.getXXX is slow for types larger than byte
because the runtime does not know that AArch64 can perform unaligned
memory accesses.

The problem is due to this code in java.nio.Bits.unaligned():

        unaligned = arch.equals("i386") || arch.equals("x86")
            || arch.equals("amd64") || arch.equals("x86_64");

If we add AArch64 to this list code quality is very much improved.

http://cr.openjdk.java.net/~aph/8073093/

Thanks,
Andrew.