cmd/compile: in prove pass, check for unsat before adding local facts
Local facts can get us to unsatisfiable because there is an
unconditional panic in the block. That shouldn't declare the whole
block as unreachable, because we do still need to enter it to get
that panic.
Fixes #68816
Change-Id: I9220edb46089690702d2eb61d112815c7ac91f16
Reviewed-on: https://go-review.googlesource.com/c/go/+/604118 Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Keith Randall <khr@golang.org>