cmd/compile: ignore non-code nodes when inlining

Avoid counting nodes that don't generate code (eg, constants) against the
inlining budget.

Fixes #21749

Change-Id: I10fca073e64be7d304709ef33e125eb8c78d5e4d
Reviewed-on: https://go-review.googlesource.com/61250Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/inl.go

@@ -279,6 +279,10 @@ func (v *hairyVisitor) visit(n *Node) bool {
 		ORETJMP:
 		v.reason = "unhandled op " + n.Op.String()
 		return true
+
+	case ODCLCONST, OEMPTY, OFALL, OLABEL:
+		// These nodes don't produce code; omit from inlining budget.
+		return false
 	}
 
 	v.budget--