diff --git a/compiler/src/dotty/tools/dotc/config/Config.scala b/compiler/src/dotty/tools/dotc/config/Config.scala
index d7980b55f36a..2e778a9db81a 100644
--- a/compiler/src/dotty/tools/dotc/config/Config.scala
+++ b/compiler/src/dotty/tools/dotc/config/Config.scala
@@ -147,8 +147,10 @@ object Config {
   /** Initial size of superId table */
   final val InitialSuperIdsSize = 4096
 
-  /** Initial capacity of uniques HashMap */
-  final val initialUniquesCapacity = 40000
+  /** Initial capacity of uniques HashMap.
+   *  Note: This MUST BE a power of two to work with util.HashSet
+   */
+  final val initialUniquesCapacity = 65536
 
   /** How many recursive calls to NamedType#underlying are performed before logging starts. */
   final val LogPendingUnderlyingThreshold = 50
diff --git a/compiler/src/dotty/tools/dotc/core/TypeOps.scala b/compiler/src/dotty/tools/dotc/core/TypeOps.scala
index ba3b049d6f18..2b0be7e6e19e 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeOps.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeOps.scala
@@ -131,7 +131,7 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
 
     /** a faster version of cs1 intersect cs2 */
     def intersect(cs1: List[ClassSymbol], cs2: List[ClassSymbol]): List[ClassSymbol] = {
-      val cs2AsSet = new util.HashSet[ClassSymbol](100)
+      val cs2AsSet = new util.HashSet[ClassSymbol](128)
       cs2.foreach(cs2AsSet.addEntry)
       cs1.filter(cs2AsSet.contains)
     }
diff --git a/compiler/src/dotty/tools/dotc/transform/TreeTransform.scala b/compiler/src/dotty/tools/dotc/transform/TreeTransform.scala
index e1e3edb7380c..768a51cf4e47 100644
--- a/compiler/src/dotty/tools/dotc/transform/TreeTransform.scala
+++ b/compiler/src/dotty/tools/dotc/transform/TreeTransform.scala
@@ -210,9 +210,16 @@ object TreeTransforms {
    */
   class NXTransformations {
 
-    private def hasRedefinedMethod(cls: Class[_], name: String): Boolean =
-      if (cls.getDeclaredMethods.exists(_.getName == name)) cls != classOf[TreeTransform]
-      else hasRedefinedMethod(cls.getSuperclass, name)
+    private def hasRedefinedMethod(cls: Class[_], name: String): Boolean = {
+      val clsMethods = cls.getDeclaredMethods
+      var i = clsMethods.length - 1
+      while (i >= 0) {
+        if (clsMethods(i).getName == name)
+          return cls != classOf[TreeTransform]
+        i -= 1
+      }
+      hasRedefinedMethod(cls.getSuperclass, name)
+    }
 
     /** Create an index array `next` of size one larger than the size of `transforms` such that
      *  for each index i, `next(i)` is the smallest index j such that
diff --git a/compiler/src/dotty/tools/dotc/util/HashSet.scala b/compiler/src/dotty/tools/dotc/util/HashSet.scala
index ff470ef5dc26..c6fa4c9e84cc 100644
--- a/compiler/src/dotty/tools/dotc/util/HashSet.scala
+++ b/compiler/src/dotty/tools/dotc/util/HashSet.scala
@@ -2,7 +2,7 @@ package dotty.tools.dotc.util
 
 /** A hash set that allows some privileged protected access to its internals
  */
-class HashSet[T >: Null <: AnyRef](initialCapacity: Int, loadFactor: Float = 0.25f) extends Set[T] {
+class HashSet[T >: Null <: AnyRef](powerOfTwoInitialCapacity: Int, loadFactor: Float = 0.25f) extends Set[T] {
   private var used: Int = _
   private var limit: Int = _
   private var table: Array[AnyRef] = _
@@ -20,11 +20,11 @@ class HashSet[T >: Null <: AnyRef](initialCapacity: Int, loadFactor: Float = 0.2
   /** Remove all elements from this set and set back to initial configuration */
   def clear(): Unit = {
     used = 0
-    allocate(initialCapacity)
+    allocate(powerOfTwoInitialCapacity)
   }
 
-  /** Turn hashode `x` into a table index */
-  private def index(x: Int): Int = math.abs(x % table.length)
+  /** Turn hashcode `x` into a table index */
+  private def index(x: Int): Int = x & (table.length - 1)
 
   /** Hashcode, can be overridden */
   def hash(x: T): Int = x.hashCode
diff --git a/compiler/src/dotty/tools/dotc/util/Stats.scala b/compiler/src/dotty/tools/dotc/util/Stats.scala
index 970b44248d70..bb2f2dff8063 100644
--- a/compiler/src/dotty/tools/dotc/util/Stats.scala
+++ b/compiler/src/dotty/tools/dotc/util/Stats.scala
@@ -21,7 +21,7 @@ import collection.mutable
   }
 
   @inline
-  def record(fn: String, n: Int = 1) =
+  def record(fn: => String, n: => Int = 1) =
     if (enabled) doRecord(fn, n)
 
   private def doRecord(fn: String, n: Int) =