Don't use ResolvedAnnotationPaths in ConstProp nor DCE (#1896)

Both use EliminateTargetPaths to duplicate modules based on annotations.
Currently, EliminateTargetPaths API is a little too limited so it
duplicates more than it should which effectively breaks Dedup whenever
DontTouchAnnotations are present.

Also, make ConstProp and DCE treat all HasDontTouches as local
annotations even if they are instance annotations. This is more
conservative but it is generally better to preserve deduplication than
to maximally optimize every instance.

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

2 files changed, 14 insertions, 17 deletions

diff --git a/src/main/scala/firrtl/transforms/ConstantPropagation.scala b/src/main/scala/firrtl/transforms/ConstantPropagation.scala
index dc9b2bbe..10e99beb 100644
--- a/src/main/scala/firrtl/transforms/ConstantPropagation.scala
+++ b/src/main/scala/firrtl/transforms/ConstantPropagation.scala
@@ -100,7 +100,7 @@ object ConstantPropagation {
 
 }
 
-class ConstantPropagation extends Transform with DependencyAPIMigration with ResolvedAnnotationPaths {
+class ConstantPropagation extends Transform with DependencyAPIMigration {
   import ConstantPropagation._
 
   override def prerequisites =
@@ -124,8 +124,6 @@ class ConstantPropagation extends Transform with DependencyAPIMigration with Res
     case _                      => false
   }
 
-  override val annotationClasses: Traversable[Class[_]] = Seq(classOf[DontTouchAnnotation])
-
   sealed trait SimplifyBinaryOp {
     def matchingArgsValue(e: DoPrim, arg: Expression): Expression
     def apply(e: DoPrim): Expression = {
@@ -841,13 +839,15 @@ class ConstantPropagation extends Transform with DependencyAPIMigration with Res
   }
 
   def execute(state: CircuitState): CircuitState = {
-    val dontTouchRTs = state.annotations.flatMap {
-      case anno: HasDontTouches => anno.dontTouches
+    val dontTouches: Seq[(OfModule, String)] = state.annotations.flatMap {
+      case anno: HasDontTouches =>
+        anno.dontTouches
+          // We treat all ReferenceTargets as if they were local because of limitations of
+          // EliminateTargetPaths
+          .map(rt => OfModule(rt.encapsulatingModule) -> rt.ref)
       case o => Nil
     }
-    val dontTouches: Seq[(OfModule, String)] = dontTouchRTs.map {
-      case Target(_, Some(m), Seq(Ref(c))) => m.OfModule -> c
-    }
+
     // Map from module name to component names
     val dontTouchMap: Map[OfModule, Set[String]] =
       dontTouches.groupBy(_._1).mapValues(_.map(_._2).toSet).toMap
diff --git a/src/main/scala/firrtl/transforms/DeadCodeElimination.scala b/src/main/scala/firrtl/transforms/DeadCodeElimination.scala
index fb1bd1f6..c9b42f8e 100644
--- a/src/main/scala/firrtl/transforms/DeadCodeElimination.scala
+++ b/src/main/scala/firrtl/transforms/DeadCodeElimination.scala
@@ -28,11 +28,7 @@ import collection.mutable
   * circumstances of their instantiation in their parent module, they will still not be removed. To
   * remove such modules, use the [[NoDedupAnnotation]] to prevent deduplication.
   */
-class DeadCodeElimination
-    extends Transform
-    with ResolvedAnnotationPaths
-    with RegisteredTransform
-    with DependencyAPIMigration {
+class DeadCodeElimination extends Transform with RegisteredTransform with DependencyAPIMigration {
 
   override def prerequisites = firrtl.stage.Forms.LowForm ++
     Seq(
@@ -368,12 +364,13 @@ class DeadCodeElimination
     state.copy(circuit = newCircuit, renames = Some(renames))
   }
 
-  override val annotationClasses: Traversable[Class[_]] =
-    Seq(classOf[DontTouchAnnotation], classOf[OptimizableExtModuleAnnotation])
-
   def execute(state: CircuitState): CircuitState = {
     val dontTouches: Seq[LogicNode] = state.annotations.flatMap {
-      case anno: HasDontTouches => anno.dontTouches.filter(_.isLocal).map(LogicNode(_))
+      case anno: HasDontTouches =>
+        anno.dontTouches
+          // We treat all ReferenceTargets as if they were local because of limitations of
+          // EliminateTargetPaths
+          .map(rt => LogicNode(rt.encapsulatingModule, rt.ref))
       case o => Nil
     }
     val doTouchExtMods: Seq[String] = state.annotations.collect {