RFR: AARCH64: 8138575: Improve generated code for profile counters

[Andrew Haley]

AArch64 generates suboptimal code for profile counters.

This

    add xscratch2, x0, #0x218
    ldr xscratch1, [xscratch2]
    add xscratch1, xscratch1, #0x1
    str xscratch1, [xscratch2]

can be this:

    ldr xscratch1, [x0, #0x218]
    add xscratch1, xscratch1, #0x1
    str xscratch1, [x0, #0x218]

Although this looks like a very minor improvement, the same pattern
is repeated many times in C1-generated code.

http://cr.openjdk.java.net/~aph/8138575/

Thanks,
Andrew.