Share Node objects between siblings (backport #4259)

build.sbt

@@ -394,7 +394,9 @@ lazy val unipublish =
         ProblemFilters.exclude[DirectMissingMethodProblem]("chisel3.*.hasAutoSeed"),
         // _circuit was package private
         ProblemFilters.exclude[DirectMissingMethodProblem]("chisel3.*._circuit"),
-        ProblemFilters.exclude[DirectMissingMethodProblem]("chisel3.*._circuit_=")
+        ProblemFilters.exclude[DirectMissingMethodProblem]("chisel3.*._circuit_="),
+        // setRef was package private
+        ProblemFilters.exclude[IncompatibleMethTypeProblem]("chisel3.*.setRef")
       ),
       // Forward doc command to unidoc
       Compile / doc := (ScalaUnidoc / doc).value,

core/src/main/scala/chisel3/Aggregate.scala

@@ -230,8 +230,9 @@ sealed class Vec[T <: Data] private[chisel3] (gen: => T, val length: Int) extend
   // simpler.
   private lazy val self: Seq[T] = {
     val _self = Vector.fill(length)(gen)
+    val thisNode = Node(this) // Share the same Node for all elements.
     for ((elt, i) <- _self.zipWithIndex)
-      elt.setRef(this, i)
+      elt.setRef(thisNode, i)
     _self
   }
 
@@ -382,7 +383,7 @@ sealed class Vec[T <: Data] private[chisel3] (gen: => T, val length: Int) extend
     port.bind(ChildBinding(this), reconstructedResolvedDirection)
 
     val i = Vec.truncateIndex(p, length)(UnlocatableSourceInfo)
-    port.setRef(this, i)
+    port.setRef(Node(this), i)
 
     port
   }
@@ -992,9 +993,10 @@ abstract class Record extends Aggregate {
       !opaqueType || (_elements.size == 1 && _elements.head._1 == ""),
       s"Opaque types must have exactly one element with an empty name, not ${_elements.size}: ${elements.keys.mkString(", ")}"
     )
+    val thisNode = Node(this) // Share the same Node for all elements.
     // Names of _elements have already been namespaced (and therefore sanitized)
     for ((name, elt) <- _elements) {
-      elt.setRef(this, name, opaque = opaqueType)
+      elt.setRef(thisNode, name, opaque = opaqueType)
     }
   }
 

core/src/main/scala/chisel3/internal/Builder.scala

@@ -259,13 +259,13 @@ private[chisel3] trait HasId extends chisel3.InstanceId {
       _refVar = imm
     }
   }
-  private[chisel3] def setRef(parent: HasId, name: String, opaque: Boolean = false): Unit = {
-    if (!opaque) setRef(Slot(Node(parent), name))
-    else setRef(OpaqueSlot(Node(parent)))
+  private[chisel3] def setRef(parent: Node, name: String, opaque: Boolean = false): Unit = {
+    if (!opaque) setRef(Slot(parent, name))
+    else setRef(OpaqueSlot(parent))
   }
 
-  private[chisel3] def setRef(parent: HasId, index: Int):  Unit = setRef(Index(Node(parent), ILit(index)))
-  private[chisel3] def setRef(parent: HasId, index: UInt): Unit = setRef(Index(Node(parent), index.ref))
+  private[chisel3] def setRef(parent: Node, index: Int):  Unit = setRef(Index(parent, ILit(index)))
+  private[chisel3] def setRef(parent: Node, index: UInt): Unit = setRef(Index(parent, index.ref))
   private[chisel3] def getRef:       Arg = _ref.get
   private[chisel3] def getOptionRef: Option[Arg] = _ref
 

core/src/main/scala/chisel3/properties/Object.scala

@@ -6,7 +6,7 @@ import scala.language.experimental.macros
 
 import chisel3.{Module, RawModule, SpecifiedDirection}
 import chisel3.experimental.{BaseModule, SourceInfo}
-import chisel3.internal.firrtl.ir.{DefClass, DefObject}
+import chisel3.internal.firrtl.ir.{DefClass, DefObject, Node}
 import chisel3.internal.sourceinfo.InstTransform
 import chisel3.internal.{throwException, Builder, HasId, NamedComponent, ObjectFieldBinding}
 
@@ -65,14 +65,14 @@ class DynamicObject private[chisel3] (val className: ClassType) extends HasId wi
     */
   def getField[T](name: String)(implicit tpe: PropertyType[T]): Property[tpe.Type] = {
     val field = Property[T]()
-    field.setRef(this, name)
+    field.setRef(Node(this), name)
     field.bind(ObjectFieldBinding(_parent.get), SpecifiedDirection.Unspecified)
     field
   }
 
   def getField[T](name: String, property: Property[T]): Property[T] = {
     val field = property.cloneType
-    field.setRef(this, name)
+    field.setRef(Node(this), name)
     field.bind(ObjectFieldBinding(_parent.get), SpecifiedDirection.Unspecified)
     field
   }