cmd/compile: don't treat an InlMark as a read during deadstore
An InlMark "read" can't make an otherwise dead store live. Without this
CL, we sometimes zero an object twice in succession because we think
there is a reader in between.
Kind of challenging to make a test for this. The second zeroing has the
same instruction on the same line number, so codegen tests can't see it.
Fixes #67957
Change-Id: I7fb97ebff50d8eb6246fc4802d1136b7cc76c45f
Reviewed-on: https://go-review.googlesource.com/c/go/+/592615 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>