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

[Roland Westrelin]

Hi Martin,

> seems like this issue is related to what I have sent out today:
> RFR(S): 8154836: VM crash due to "Base pointers must match"
> I also had to change the AddP case of final graph reshaping.
> 
> In one part of my change, I skip the graph transformation on non-X86 platforms when we're running in heap based compressed oops mode.
> 
> Maybe I have to remove that part of my change, or at least adapt it.
> We should make sure that the changes don't get pushed on the same day.

Thanks for the heads up. It looks like your change will get in before
mine. I'll send an updated webrev once it's integrated.

Roland.