cmd/compile: convert to using a map in getInstInfo, rather than SetImplicit()
SetImplicit() has an explicit meaning and really shouldn't be used in
this way - its use is left over from early prototype of the dictionary
code. Convert from using SetImplicit to just using a map during
traversal.
Change-Id: I3d257c101a859f000e159d7ced307d1b7cf990d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/356310
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>