cmd/compile: fix PrefetchStreamed builtin implementation on PPC64
This CL fixes encoding of PrefetchStreamed on PPC64 to be consistent
with what is implemented on AMD64 and ARM64 platforms which is
prefetchNTA (prefetch non-temporal access). Looking at the definition
of prefetchNTA, the closest corresponding Touch hint (TH) value to be
used on PPC64 is 16 that states that the address is accessed in a
transient manner. Current usage of TH=8 may cause degraded
performance.
Change-Id: I393bf5a9b971a22f632b3cbfb4fa659062af9a27
Reviewed-on: https://go-review.googlesource.com/c/go/+/390316 Reviewed-by: Paul Murphy <murp@ibm.com> Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>