Use circuit name hashCode for circuit anno hashCode (#2504)

It is unclear if having more than one circuit annotation even works. If
it does, it is implausible that they would have the same circuit name
since that would correspond to a namespace collision.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/main/scala/firrtl/stage/FirrtlAnnotations.scala b/src/main/scala/firrtl/stage/FirrtlAnnotations.scala
index 515c8af9..7f4266fd 100644
--- a/src/main/scala/firrtl/stage/FirrtlAnnotations.scala
+++ b/src/main/scala/firrtl/stage/FirrtlAnnotations.scala
@@ -283,8 +283,12 @@ case class FirrtlCircuitAnnotation(circuit: Circuit) extends NoTargetAnnotation
   /* Caching the hashCode for a large circuit is necessary due to repeated queries, e.g., in
    * [[Compiler.propagateAnnotations]]. Not caching the hashCode will cause severe performance degredations for large
    * [[Annotations]].
+   * @note Uses the hashCode of the name of the circuit. Creating a HashMap with different Circuits
+   *       that nevertheless have the same name is extremely uncommon so collisions are not a concern.
+   *       Include productPrefix so that this doesn't collide with other types that use a similar
+   *       strategy and hash the same String.
    */
-  override lazy val hashCode: Int = circuit.hashCode
+  override lazy val hashCode: Int = (this.productPrefix + circuit.main).hashCode
 
 }