Speed up Deduplication (bp #1602) (#1619)

* Remove expensive .distinct in Dedup

(cherry picked from commit 36227e9)

* Remove accidental hashing of all Modules in Dedup

(cherry picked from commit 71e922c)

Co-authored-by: Jack Koenig <koenig@sifive.com>

src/main/scala/firrtl/transforms/Dedup.scala

@@ -72,7 +72,11 @@ class DedupModules extends Transform {
     val dedupMap = DedupModules.deduplicate(c, noDedups.toSet, annos, renameMap)
 
     // Use old module list to preserve ordering
-    val dedupedModules = c.modules.map(m => dedupMap(m.name)).distinct
+    // Lookup what a module deduped to, if its a duplicate, remove it
+    val dedupedModules = c.modules.flatMap { m =>
+      val mx = dedupMap(m.name)
+      if (mx.name == m.name) Some(mx) else None
+    }
 
     val cname = CircuitName(c.main)
     val map = dedupMap.map { case (from, to) =>
@@ -421,7 +425,11 @@ object DedupModules {
     val dedupedName2module = tag2name.map({ case (tag, name) => name -> DedupModules.dedupInstances(top, name, moduleMap, name2name, renameMap) })
 
     // Build map from original name to corresponding deduped module
-    val name2module = tag2all.flatMap({ case (tag, names) => names.map(n => n -> dedupedName2module(tag2name(tag))) })
+    // It is important to flatMap before looking up the DefModules so that they aren't hashed
+    val name2module: Map[String, DefModule] =
+      tag2all.flatMap { case (tag, names) => names.map(_ -> tag) }
+             .mapValues(tag => dedupedName2module(tag2name(tag)))
+             .toMap
 
     // Build renameMap
     val indexedTargets = mutable.HashMap[String, IndexedSeq[ReferenceTarget]]()
@@ -433,7 +441,7 @@ object DedupModules {
       }
     }
 
-    name2module.toMap
+    name2module
   }
 
   def computeIndexedNames(main: String, m: DefModule): IndexedSeq[ReferenceTarget] = {