optimise getOrElseUpdate

Author: bishabosha

compiler/src/dotty/tools/dotc/util/EqHashMap.scala

@@ -58,6 +58,22 @@ extends GenericHashMap[Key, Value](initialCapacity, capacityMultiple):
     used += 1
     if used > limit then growTable()
 
+  override def getOrElseUpdate(key: Key, value: => Value): Value =
+    // created by blending lookup and update, avoid having to recompute hash and probe
+    Stats.record(statsItem("lookup-or-update"))
+    var idx = firstIndex(key)
+    var k = keyAt(idx)
+    while k != null do
+      if isEqual(k, key) then return valueAt(idx)
+      idx = nextIndex(idx)
+      k = keyAt(idx)
+    val v = value
+    setKey(idx, key)
+    setValue(idx, v)
+    used += 1
+    if used > limit then growTable()
+    v
+
   private def addOld(key: Key, value: Value): Unit =
     Stats.record(statsItem("re-enter"))
     var idx = firstIndex(key)

compiler/src/dotty/tools/dotc/util/GenericHashMap.scala

@@ -129,12 +129,20 @@ abstract class GenericHashMap[Key, Value]
     null
 
   def getOrElseUpdate(key: Key, value: => Value): Value =
-    var v: Value | Null = lookup(key)
-    if v == null then
-      val v1 = value
-      v = v1
-      update(key, v1)
-    v.uncheckedNN
+    // created by blending lookup and update, avoid having to recompute hash and probe
+    Stats.record(statsItem("lookup-or-update"))
+    var idx = firstIndex(key)
+    var k = keyAt(idx)
+    while k != null do
+      if isEqual(k, key) then return valueAt(idx)
+      idx = nextIndex(idx)
+      k = keyAt(idx)
+    val v = value
+    setKey(idx, key)
+    setValue(idx, v)
+    used += 1
+    if used > limit then growTable()
+    v
 
   private def addOld(key: Key, value: Value): Unit =
     Stats.record(statsItem("re-enter"))

compiler/src/dotty/tools/dotc/util/HashMap.scala

@@ -63,6 +63,22 @@ extends GenericHashMap[Key, Value](initialCapacity, capacityMultiple):
     used += 1
     if used > limit then growTable()
 
+  override def getOrElseUpdate(key: Key, value: => Value): Value =
+    // created by blending lookup and update, avoid having to recompute hash and probe
+    Stats.record(statsItem("lookup-or-update"))
+    var idx = firstIndex(key)
+    var k = keyAt(idx)
+    while k != null do
+      if isEqual(k, key) then return valueAt(idx)
+      idx = nextIndex(idx)
+      k = keyAt(idx)
+    val v = value
+    setKey(idx, key)
+    setValue(idx, v)
+    used += 1
+    if used > limit then growTable()
+    v
+
   private def addOld(key: Key, value: Value): Unit =
     Stats.record(statsItem("re-enter"))
     var idx = firstIndex(key)