[release-branch.go1.18] cmd/compile: backport fix for #51840
This CL is a manual backport of CLs 403837 and 404914 to Go 1.18.
CL 403837 was intended just as a simplification CL, but evidently it
also fixed #51840. However, for backporting to Go 1.18, the existing
logic needs to be preserved to support -G=0 mode (which still relies
on Ntype).
Fixes #51849.
Change-Id: Ib060b0bc67ecf26de8a65d5b4d2f8a65cd547517
Reviewed-on: https://go-review.googlesource.com/c/go/+/405436
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Keith Randall <khr@google.com>