Make it possible to GC Data instances

No longer create a pointer from parent to every HasId, only do it by
default for BaseModules and MemBases. Add pointer from parent to Data
upon binding the Data.

* Add MemTypeBinding for port types of Mems

This binding is similar to the SampleElementBinding for Vecs in that
these Data are not truly hardware, but are represented in the FIRRTL IR
and thus need some representation.

* Call _onModuleClose on unbound Records

This maintains some corner-case behavior that is nevertheless relied
upon. It ensures that refs are set for the elements of Records, even if
they are not bound to any real hardware.

1 files changed, 3 insertions, 2 deletions

diff --git a/core/src/main/scala/chisel3/Data.scala b/core/src/main/scala/chisel3/Data.scala
index 332527bf..377a94e6 100644
--- a/core/src/main/scala/chisel3/Data.scala
+++ b/core/src/main/scala/chisel3/Data.scala
@@ -339,13 +339,14 @@ abstract class Data extends HasId with NamedComponent with SourceInfoDoc {
   private[chisel3] final def isSynthesizable: Boolean = _binding.map {
     case ChildBinding(parent) => parent.isSynthesizable
     case _: TopBinding => true
-    case _: SampleElementBinding[_] => false
+    case (_: SampleElementBinding[_] | _: MemTypeBinding[_]) => false
   }.getOrElse(false)
 
   private[chisel3] def topBindingOpt: Option[TopBinding] = _binding.flatMap {
     case ChildBinding(parent) => parent.topBindingOpt
     case bindingVal: TopBinding => Some(bindingVal)
     case SampleElementBinding(parent) => parent.topBindingOpt
+    case _: MemTypeBinding[_] => None
   }
 
   private[chisel3] def topBinding: TopBinding = topBindingOpt.get
@@ -355,7 +356,7 @@ abstract class Data extends HasId with NamedComponent with SourceInfoDoc {
     * node is the top-level.
     * binding and direction are valid after this call completes.
     */
-  private[chisel3] def bind(target: Binding, parentDirection: SpecifiedDirection = SpecifiedDirection.Unspecified)
+  private[chisel3] def bind(target: Binding, parentDirection: SpecifiedDirection = SpecifiedDirection.Unspecified): Unit
 
   // Both _direction and _resolvedUserDirection are saved versions of computed variables (for
   // efficiency, avoid expensive recomputation of frequent operations).