1 files changed, 43 insertions, 0 deletions
diff --git a/src/main/scala/firrtl/options/phases/DeletedWrapper.scala b/src/main/scala/firrtl/options/phases/DeletedWrapper.scala
new file mode 100644
index 00000000..0a959f32
--- /dev/null
+++ b/src/main/scala/firrtl/options/phases/DeletedWrapper.scala
@@ -0,0 +1,43 @@
+// See LICENSE for license details.
+
+package firrtl.options.phases
+
+import firrtl.AnnotationSeq
+import firrtl.annotations.DeletedAnnotation
+import firrtl.options.{Phase, Translator}
+
+import scala.collection.mutable
+
+/** Wrap a [[firrtl.options.Phase Phase]] such that any [[firrtl.annotations.Annotation Annotation]] removed by the
+  * wrapped [[firrtl.options.Phase Phase]] will be added as [[firrtl.annotations.DeletedAnnotation DeletedAnnotation]]s.
+  * @param p a [[firrtl.options.Phase Phase]] to wrap
+  */
+class DeletedWrapper(p: Phase) extends Phase with Translator[AnnotationSeq, (AnnotationSeq, AnnotationSeq)] {
+
+  override lazy val name: String = p.name
+
+  def aToB(a: AnnotationSeq): (AnnotationSeq, AnnotationSeq) = (a, a)
+
+  def bToA(b: (AnnotationSeq, AnnotationSeq)): AnnotationSeq = {
+
+    val (in, out) = (mutable.LinkedHashSet() ++ b._1, mutable.LinkedHashSet() ++ b._2)
+
+    (in -- out).map {
+      case DeletedAnnotation(n, a) => DeletedAnnotation(s"$n+$name", a)
+      case a                       => DeletedAnnotation(name, a)
+    }.toSeq ++ b._2
+
+  }
+
+  def internalTransform(b: (AnnotationSeq, AnnotationSeq)): (AnnotationSeq, AnnotationSeq) = (b._1, p.transform(b._2))
+
+}
+
+object DeletedWrapper {
+
+  /** Wrap a [[firrtl.options.Phase Phase]] in a [[DeletedWrapper]]
+    * @param p a [[firrtl.options.Phase Phase]] to wrap
+    */
+  def apply(p: Phase): DeletedWrapper = new DeletedWrapper(p)
+
+}