cmd/compile/internal/ssa: combine shift and addition for riscv64 rva22u64
When GORISCV64 enables rva22u64, combined shift and addition using the
SH1ADD, SH2ADD and SH3ADD instructions that are available via the Zba
extension. This results in more than 2000 instructions being removed
from the Go binary on riscv64.
Change-Id: Ia62ae7dda3d8083cff315113421bee73f518eea8
Reviewed-on: https://go-review.googlesource.com/c/go/+/606636
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Mark Ryan <markdryan@rivosinc.com> Reviewed-by: Michael Pratt <mpratt@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com>