[llvm] [DominanceFrontier] Support post-dominators on graphs with single root (PR #179336)

[Andrei Elovikov via llvm-commits]

================
@@ -0,0 +1,94 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../lib/Transforms/Vectorize/VPlan.h"
+
+#include "VPlanTestBase.h"
+#include "llvm/Analysis/DominanceFrontier.h"
+#include "llvm/Analysis/DominanceFrontierImpl.h"
----------------
eas wrote:

Here or in general? IIUC, for the latter, it's there for the "extern template" to only instantiate definitions in one TU.

https://github.com/llvm/llvm-project/pull/179336