[dev.regabi] cmd/compile: remove Orig, SetOrig from Node interface
These are only needed for a few opcodes, and we can avoid
wasting storage in every implementation by using the extension
interface pattern with a helper function for access.
Of course, in the current codebase, there is only one Node
implementation (*node) and it has these methods, so there
is no danger of a functional change in this particular CL.
Passes buildall w/ toolstash -cmp.
Change-Id: I440c6c232f1fe7b56b852a00dc530f8f49a6b12d
Reviewed-on: https://go-review.googlesource.com/c/go/+/274089
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>