Fix GroupComponents to work with unused components

Previously, components that did not affect the output would cause
exceptions because they were missing from the label2group Map. This
commit treats them as "reachable" by the ports so they are included in
the default "ungrouped" group.

2 files changed, 45 insertions, 1 deletions

diff --git a/src/main/scala/firrtl/transforms/GroupComponents.scala b/src/main/scala/firrtl/transforms/GroupComponents.scala
index 805b534e..8c36bb6d 100644
--- a/src/main/scala/firrtl/transforms/GroupComponents.scala
+++ b/src/main/scala/firrtl/transforms/GroupComponents.scala
@@ -119,6 +119,11 @@ class GroupComponents extends firrtl.Transform {
       }
     }
 
+    // Unused nodes are not reachable from any group nor the root--add them to root group
+    for ((v, _) <- deps.getEdgeMap) {
+      reachableNodes.getOrElseUpdate(v, mutable.Set(""))
+    }
+
     // Add nodes who are reached by a single group, to that group
     reachableNodes.foreach { case (node, membership) =>
       if(membership.size == 1) {
@@ -307,7 +312,9 @@ class GroupComponents extends firrtl.Transform {
     }
     def onStmt(stmt: Statement): Unit = stmt match {
       case w: WDefInstance =>
-      case h: IsDeclaration => h map onExpr(WRef(h.name))
+      case h: IsDeclaration =>
+        bidirGraph.addVertex(h.name)
+        h map onExpr(WRef(h.name))
       case Attach(_, exprs) => // Add edge between each expression
         exprs.tail map onExpr(getWRef(exprs.head))
       case Connect(_, loc, expr) =>
diff --git a/src/test/scala/firrtlTests/transforms/GroupComponentsSpec.scala b/src/test/scala/firrtlTests/transforms/GroupComponentsSpec.scala
index f51d44ae..c54e02e3 100644
--- a/src/test/scala/firrtlTests/transforms/GroupComponentsSpec.scala
+++ b/src/test/scala/firrtlTests/transforms/GroupComponentsSpec.scala
@@ -46,6 +46,43 @@ class GroupComponentsSpec extends LowTransformSpec {
       """.stripMargin
     execute(input, check, groups)
   }
+  "Grouping" should "work even when there are unused nodes" in {
+    val input =
+    s"""circuit $top :
+        |  module $top :
+        |    input in: UInt<16>
+        |    output out: UInt<16>
+        |    node n = UInt<16>("h0")
+        |    wire w : UInt<16>
+        |    wire a : UInt<16>
+        |    wire b : UInt<16>
+        |    a <= UInt<16>("h0")
+        |    b <= a
+        |    w <= in
+        |    out <= w
+      """.stripMargin
+    val groups = Seq(
+      GroupAnnotation(Seq(topComp("w")), "Child", "inst", Some("_OUT"), Some("_IN"))
+    )
+    val check =
+     s"""circuit Top :
+        |  module $top :
+        |    input in: UInt<16>
+        |    output out: UInt<16>
+        |    inst inst of Child
+        |    node n = UInt<16>("h0")
+        |    inst.in_IN <= in
+        |    node a = UInt<16>("h0")
+        |    node b = a
+        |    out <= inst.w_OUT
+        |  module Child :
+        |    input in_IN : UInt<16>
+        |    output w_OUT : UInt<16>
+        |    node w = in_IN
+        |    w_OUT <= w
+      """.stripMargin
+    execute(input, check, groups)
+  }
 
   "The two sets of instances" should "be grouped" in {
     val input =