cmd/compile: debug trace output for -N variable location gen
Add some rudimentary debug trace output for -N location list
generation if "-d=ssa/locationlists" is set.
Updates #45948.
Change-Id: If1a95730538a6e7def7ebe1ece1a71da8e5f0975
Reviewed-on: https://go-review.googlesource.com/c/go/+/317089
Trust: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>