cmd/compile: add PPC64 ssa ops to support carry chain arithmetic
These are the opcodes required to lower math/bits.Add64 and
math/bits.Sub64 directly into ssa form. Likewise, opcodes which
clobber CA are marked.
This does not alter code generation. It prepares for future changes
to support scheduling carry chaining ops more effectively, and then
changes to lower into PPC64 opcodes.
Change-Id: I2723deee4a98b3c365f691857512df53280ae40f
Reviewed-on: https://go-review.googlesource.com/c/go/+/394594
Trust: Keith Randall <khr@golang.org>
Run-TryBot: Paul Murphy <murp@ibm.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Cherry Mui <cherryyz@google.com>