--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/llvm-xray/xray-registry.h	Mon May 25 11:07:02 2020 +0900
@@ -0,0 +1,40 @@
+//===- xray-registry.h - Define registry mechanism for commands. ----------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Implement a simple subcommand registry.
+//
+//===----------------------------------------------------------------------===//
+#ifndef TOOLS_LLVM_XRAY_XRAY_REGISTRY_H
+#define TOOLS_LLVM_XRAY_XRAY_REGISTRY_H
+
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Error.h"
+
+namespace llvm {
+namespace xray {
+
+// Use |CommandRegistration| as a global initialiser that registers a function
+// and associates it with |SC|. This requires that a command has not been
+// registered to a given |SC|.
+//
+// Usage:
+//
+//   // At namespace scope.
+//   static CommandRegistration Unused(&MySubCommand, [] { ... });
+//
+struct CommandRegistration {
+  CommandRegistration(cl::SubCommand *SC, std::function<Error()> Command);
+};
+
+// Requires that |SC| is not null and has an associated function to it.
+std::function<Error()> dispatch(cl::SubCommand *SC);
+
+} // namespace xray
+} // namespace llvm
+
+#endif // TOOLS_LLVM_XRAY_XRAY_REGISTRY_H