delete usages of toSet for determinism (#1686)

* delete usages of toSet for determinism

* add formatting suggestion from code review

2 files changed, 10 insertions, 5 deletions

diff --git a/src/main/scala/firrtl/options/DependencyManager.scala b/src/main/scala/firrtl/options/DependencyManager.scala
index 910d44bb..ee6a7404 100644
--- a/src/main/scala/firrtl/options/DependencyManager.scala
+++ b/src/main/scala/firrtl/options/DependencyManager.scala
@@ -167,8 +167,13 @@ trait DependencyManager[A, B <: TransformLike[A] with DependencyAPI[B]] extends
         blacklist = _currentState,
 
         /* Explore all invalidated transforms **EXCEPT** the current transform! */
-        extractor = (p: B) => v.filter(p.invalidates).map(oToD(_)).toSet - oToD(p)))
-      .reverse
+        extractor = (p: B) => {
+          val filtered = new LinkedHashSet[Dependency[B]]
+          filtered ++= v.filter(p.invalidates).map(oToD(_))
+          filtered -= oToD(p)
+          filtered
+        })
+    ).reverse
   }
 
   /** Wrap a possible [[CyclicException]] thrown by a thunk in a [[DependencyManagerException]] */
diff --git a/src/main/scala/firrtl/options/Phase.scala b/src/main/scala/firrtl/options/Phase.scala
index 6dd5d969..2d08318e 100644
--- a/src/main/scala/firrtl/options/Phase.scala
+++ b/src/main/scala/firrtl/options/Phase.scala
@@ -125,14 +125,14 @@ trait DependencyAPI[A <: DependencyAPI[A]] { this: TransformLike[_] =>
     * $seqNote
     */
   def prerequisites: Seq[Dependency[A]] = Seq.empty
-  private[options] lazy val _prerequisites: LinkedHashSet[Dependency[A]] = new LinkedHashSet() ++ prerequisites.toSet
+  private[options] lazy val _prerequisites: LinkedHashSet[Dependency[A]] = new LinkedHashSet() ++ prerequisites
 
   /** All transforms that, if a prerequisite of *another* transform, will run before this transform.
     * $seqNote
     */
   def optionalPrerequisites: Seq[Dependency[A]] = Seq.empty
   private[options] lazy val _optionalPrerequisites: LinkedHashSet[Dependency[A]] =
-    new LinkedHashSet() ++ optionalPrerequisites.toSet
+    new LinkedHashSet() ++ optionalPrerequisites
 
   /** All transforms that must run ''after'' this transform
     *
@@ -171,7 +171,7 @@ trait DependencyAPI[A <: DependencyAPI[A]] { this: TransformLike[_] =>
     */
   def optionalPrerequisiteOf: Seq[Dependency[A]] = dependents
   private[options] lazy val _optionalPrerequisiteOf: LinkedHashSet[Dependency[A]] =
-    new LinkedHashSet() ++ optionalPrerequisiteOf.toSet
+    new LinkedHashSet() ++ optionalPrerequisiteOf
 
   /** A function that, given *another* transform (parameter `a`) will return true if this transform invalidates/undos the
     * effects of the *other* transform (parameter `a`).