[VonTum]

For the uninitiated in AArch64, are there specific parts of it you're referring to here? Mostly what I find is that it lets you stitch common instruction combinations together, like shift + add and fancier adressing. Since the whole point of RISC-V was a RISC instruction set, these things are superfluous.

[zozbot234]

RISC-V has shift+add instructions as part of the Zba extension. Zba is part of B, so it's included in many recent RISC-V profiles.