cmd/compile/internal/ssa: improve carry addition rules on PPC64
Fold constant int16 addends for usages of math/bits.Add64(x,const,0)
on PPC64. This usage shows up in a few crypto implementations;
notably the go wrapper for CL 626176.
Change-Id: I6963163330487d04e0479b4fdac235f97bb96889
Reviewed-on: https://go-review.googlesource.com/c/go/+/625899 Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Emmanuel Odeke <emmanuel@orijtech.com> Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Keith Randall <khr@golang.org>