From edd8ff602b0a961ff1e169bf202e454d28bb0372 Mon Sep 17 00:00:00 2001
From: Jack Koenig <koenig@sifive.com>
Date: Thu, 4 Jul 2024 15:15:03 -0700
Subject: [PATCH] Move circuitVar from HasId to BaseModule

---
 core/src/main/scala/chisel3/Module.scala       |  7 +++++++
 .../main/scala/chisel3/internal/Builder.scala  | 18 ++++++++----------
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/core/src/main/scala/chisel3/Module.scala b/core/src/main/scala/chisel3/Module.scala
index 4165bd5f4c8..aabbeb88d0d 100644
--- a/core/src/main/scala/chisel3/Module.scala
+++ b/core/src/main/scala/chisel3/Module.scala
@@ -426,6 +426,13 @@ package experimental {
   abstract class BaseModule extends HasId with IsInstantiable {
     _parent.foreach(_.addId(this))
 
+    // Set if the returned top-level module of a nested call to the Chisel Builder, see Definition.apply
+    private var _circuitVar:       BaseModule = null // using nullable var for better memory usage
+    private[chisel3] def _circuit: Option[BaseModule] = Option(_circuitVar)
+    private[chisel3] def _circuit_=(target: Option[BaseModule]): Unit = {
+      _circuitVar = target.getOrElse(null)
+    }
+
     // Protected so it can be overridden by the compiler plugin
     protected def _sourceInfo: SourceInfo = UnlocatableSourceInfo
 
diff --git a/core/src/main/scala/chisel3/internal/Builder.scala b/core/src/main/scala/chisel3/internal/Builder.scala
index 5f38b2ee632..53bcb974f91 100644
--- a/core/src/main/scala/chisel3/internal/Builder.scala
+++ b/core/src/main/scala/chisel3/internal/Builder.scala
@@ -122,13 +122,6 @@ private[chisel3] trait HasId extends chisel3.InstanceId {
     _parentVar = target.getOrElse(null)
   }
 
-  // Set if the returned top-level module of a nested call to the Chisel Builder, see Definition.apply
-  private var _circuitVar:       BaseModule = null // using nullable var for better memory usage
-  private[chisel3] def _circuit: Option[BaseModule] = Option(_circuitVar)
-  private[chisel3] def _circuit_=(target: Option[BaseModule]): Unit = {
-    _circuitVar = target.getOrElse(null)
-  }
-
   private[chisel3] val _id: Long = Builder.idGen.next
 
   // TODO: remove this, but its removal seems to cause a nasty Scala compiler crash.
@@ -351,9 +344,14 @@ private[chisel3] trait HasId extends chisel3.InstanceId {
   }
   def circuitName: String = _parent match {
     case None =>
-      _circuit match {
-        case None    => instanceName
-        case Some(o) => o.circuitName
+      // Only modules have circuits
+      this match {
+        case b: BaseModule =>
+          b._circuit match {
+            case Some(c) => c.circuitName
+            case None    => instanceName
+          }
+        case _ => instanceName
       }
     case Some(ViewParent) => reifyParent.circuitName
     case Some(p)          => p.circuitName