ssa: clarify semantics of ID-to-PC translation function
Make it clear that the `block` argument is not always used, and stop
passing it in a case where it didn't really make sense - at the end of a
function.
Change-Id: I2fa86bed6ceb53a1b1cbfda5c3392e7e9da9579d
Reviewed-on: https://go-review.googlesource.com/c/go/+/502115
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: David Chase <drchase@google.com> Reviewed-by: David Chase <drchase@google.com>