cmd/compile: allow multi-field structs to be stored directly in interfaces
If the struct is a bunch of 0-sized fields and one pointer field.
Merged revert-of-revert for 4 CLs.
original revert
681937 695016
693415 694996
693615 695015
694195 694995
Fixes #74092
Update #74888
Update #74908
Update #74935
(updated issues are bugs in the last attempt at this)
Change-Id: I32246d49b8bac3bb080972dc06ab432a5480d560
Reviewed-on: https://go-review.googlesource.com/c/go/+/714421
Auto-Submit: Keith Randall <khr@golang.org> Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Keith Randall <khr@google.com>