RFR(M): 8154826: AArch64: take better advantage of base + shifted offset addressing mode

[Roland Westrelin]

Thanks for looking at this, Vladimir.

> You did not remove Matcher::clone_shift_expressions variable
> initialization from all .ad files.
> 
> Changes look correct - you cloned shared code into .ad files and make
> code platform specific.
> But duplicated code will increase maintenance cost. Can you leave code
> for clone_shift_expressions=false case (same code on several platforms)
> in matcher.cpp?

What about this?

http://cr.openjdk.java.net/~roland/8154826/webrev.02/

Roland.