cmd/compile/internal/devirtualize: improve concrete type analysis
This change improves the concrete type analysis in the devirtualizer,
it not longer relies on ir.Reassigned, it now statically tries to
determine the concrete type of an interface, even when assigned
multiple times, following type assertions and iface conversions.
Alternative to CL 649195
Updates #69521
Fixes #64824
Change-Id: Ib1656e19f3619ab2e1e6b2c78346cc320490b2af
GitHub-Last-Rev:
e8fa0b12f0a7b1d7ae00e5edb54ce04d1f702c09
GitHub-Pull-Request: golang/go#71935
Reviewed-on: https://go-review.googlesource.com/c/go/+/652036
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Keith Randall <khr@golang.org>