1 files changed, 39 insertions, 0 deletions
diff --git a/src/main/scala/firrtl/annotations/Annotation.scala b/src/main/scala/firrtl/annotations/Annotation.scala
index 8aba4826..adde816a 100644
--- a/src/main/scala/firrtl/annotations/Annotation.scala
+++ b/src/main/scala/firrtl/annotations/Annotation.scala
@@ -77,6 +77,45 @@ trait SingleTargetAnnotation[T <: Named] extends Annotation {
   }
 }
 
+/** [[MultiTargetAnnotation]] keeps the renamed targets grouped within a single annotation. */
+trait MultiTargetAnnotation extends Annotation {
+  /** Contains a sequence of [[Target]].
+    * When creating in [[toFirrtl]], [[targets]] should be assigned by `Seq(Seq(TargetA), Seq(TargetB), Seq(TargetC))`
+    * */
+  val targets: Seq[Seq[Target]]
+
+  /** Create another instance of this Annotation*/
+  def duplicate(n: Seq[Seq[Target]]): Annotation
+
+  /** Assume [[RenameMap]] is `Map(TargetA -> Seq(TargetA1, TargetA2, TargetA3), TargetB -> Seq(TargetB1, TargetB2))`
+    * in the update, this Annotation is still one annotation, but the contents are renamed in the below form
+    * Seq(Seq(TargetA1, TargetA2, TargetA3), Seq(TargetB1, TargetB2), Seq(TargetC))
+    **/
+  def update(renames: RenameMap): Seq[Annotation] = Seq(duplicate(targets.map(ts => ts.flatMap(renames(_)))))
+
+  private def crossJoin[T](list: Seq[Seq[T]]): Seq[Seq[T]] =
+    list match {
+      case Nil => Nil
+      case x :: Nil => x map (Seq(_))
+      case x :: xs =>
+        val xsJoin = crossJoin(xs)
+        for {
+          i <- x
+          j <- xsJoin
+        } yield {
+          Seq(i) ++ j
+        }
+    }
+
+  /** Assume [[RenameMap]] is `Map(TargetA -> Seq(TargetA1, TargetA2, TargetA3), TargetB -> Seq(TargetB1, TargetB2))`
+    * After flat, this Annotation will be flat to the [[AnnotationSeq]] in the below form
+    * Seq(Seq(TargetA1), Seq(TargetB1), Seq(TargetC)); Seq(Seq(TargetA1), Seq(TargetB2), Seq(TargetC))
+    * Seq(Seq(TargetA2), Seq(TargetB1), Seq(TargetC)); Seq(Seq(TargetA2), Seq(TargetB2), Seq(TargetC))
+    * Seq(Seq(TargetA3), Seq(TargetB1), Seq(TargetC)); Seq(Seq(TargetA3), Seq(TargetB2), Seq(TargetC))
+    * */
+  def flat(): AnnotationSeq = crossJoin(targets).map(r => duplicate(r.map(Seq(_))))
+}
+
 @deprecated("Just extend NoTargetAnnotation", "1.1")
 trait SingleStringAnnotation extends NoTargetAnnotation {
   def value: String