Add support for assembling the FMA instructions present in the LoongArch
base ISA v1.00. This requires adding a new instruction format and making
use of a third source operand, which is put in RestArgs[0].
The single-precision instructions have the `.s` prefix in their official
mnemonics, and similar Go asm instructions all have `S` prefix for the
other architectures having FMA support, but in this change they instead
have `F` prefix in Go asm because loong64 currently follows the mips
backends in the naming convention. This could be changed later because
FMA is fully expressible in pure Go, making it unlikely to have to hand-
write such assembly in the wild.
Example mapping between actual encoding and Go asm syntax:
fmadd.s fd, fd, fk, fa -> FMADDF fa, fk, fd
(prog.From = fa, prog.Reg = fk and prog.To = fd)
This patch is a copy of CL 477716. Co-authored-by: WANG Xuerui <git@xen0n.name>
Change-Id: I9b4e4c601d6c5a854ee238f085849666e4faf090
Reviewed-on: https://go-review.googlesource.com/c/go/+/623877 Reviewed-by: abner chenc <chenguoqi@loongson.cn> Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Carlos Amedee <carlos@golang.org>