[JS IR DCE] Add CLI option to print reachability info

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArguments.kt

@@ -1,17 +1,6 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
 package org.jetbrains.kotlin.cli.common.arguments
@@ -133,6 +122,9 @@ class K2JSCompilerArguments : CommonCompilerArguments() {
     @Argument(value = "-Xir-dce-driven", description = "Perform a more experimental faster dead code elimination")
     var irDceDriven: Boolean by FreezableVar(false)
 
+    @Argument(value = "-Xir-dce-print-reachability-info", description = "Print declarations' reachability info to stdout during performing DCE")
+    var irDcePrintReachabilityInfo: Boolean by FreezableVar(false)
+
     @Argument(value = "-Xir-only", description = "Disables pre-IR backend")
     var irOnly: Boolean by FreezableVar(false)