cmd/internal/obj: support Zba, Zbb, Zbs extensions in riscv64 assembler
Add assembler support for Zba, Zbb, Zbs extensions, which are
mandatory in the rva22u64 profile. These can be used to accelerate
address computation and bit manipulation.
Change-Id: Ie90fe6b76b1382cf69984a0e71a72d3cba0e750a
Reviewed-on: https://go-review.googlesource.com/c/go/+/559655 Reviewed-by: M Zhuo <mengzhuo1203@gmail.com>
Run-TryBot: Joel Sing <joel@sing.id.au> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Joel Sing <joel@sing.id.au> Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>