Added RemoveEmpty.scala, which removes Empty and nested Blocks (#218)

* Added RemoveEmpty.scala, which removes Empty and nested Blocks

* Reused squashEmpty from ExpandWhens by moving it to Utils

* Squash EmptyStmts in ExpandWhens correctly

1 files changed, 14 insertions, 0 deletions

diff --git a/src/main/scala/firrtl/Utils.scala b/src/main/scala/firrtl/Utils.scala
index 383d4df7..be70ac77 100644
--- a/src/main/scala/firrtl/Utils.scala
+++ b/src/main/scala/firrtl/Utils.scala
@@ -62,6 +62,20 @@ object Utils extends LazyLogging {
     result
   }
 
+  /** Removes all [[firrtl.ir.Empty]] statements and condenses
+   * [[firrtl.ir.Block]] statements.
+    */
+  def squashEmpty(s: Statement): Statement = s map squashEmpty match {
+    case Block(stmts) =>
+      val newStmts = stmts filter (_ != EmptyStmt)
+      newStmts.size match {
+        case 0 => EmptyStmt
+        case 1 => newStmts.head
+        case _ => Block(newStmts)
+      }
+    case s => s
+  }
+
   /** Indent the results of [[ir.FirrtlNode.serialize]] */
   def indent(str: String) = str replaceAllLiterally ("\n", "\n  ")
   def serialize(bi: BigInt): String =