cmd/internal/obj/ppc64: improve large prologue generation
Avoid needing an unsafe section to store LR and adjust SP
for large constants by using the stdux (MOVDU) instruction.
This is also a few instructions shorter as the large
constant adjustment is only created once.
Change-Id: I6ff7a24181cdadb1846a33129fc148dcf59b76d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/710197 Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>