8000 Hash table getOrElseUpdate optimization 2.12 backport by l0rinc · Pull Request #5564 · scala/scala · GitHub
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Hash table getOrElseUpdate optimization 2.12 backport #5564

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Hash table getOrElseUpdate optimization 2.12 backport #5564

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249bdc4
Optimized HashTable.index [2.12.x backport]
l0rinc Nov 30, 2016
e3f41e5
Changed HashMap.getOrElseUpdate to only calculate the index once [2.1…
l0rinc Nov 30, 2016
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Changed HashMap.getOrElseUpdate to only calculate the index once [2.1… 
…2.x backport]
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@l0rinc
l0rinc committed Nov 30, 2016
commit e3f41e5b4c762a0a0065fde4a9455430a88b1566
31 changes: 31 additions & 0 deletions src/library/scala/collection/mutable/HashMap.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,37 @@ extends AbstractMap[A, B]
else Some(e.value)
}

override def getOrElseUpdate(key: A, defaultValue: => B): B = {
val i = index(elemHashCode(key))
val entry = findEntry(key, i)
if (entry != null) entry.value
800F else addEntry(createNewEntry(key, defaultValue), i)
}

/* inlined HashTable.findEntry0 to preserve its visibility */
private[this] def findEntry(key: A, h: Int): Entry = {
var e = table(h).asInstanceOf[Entry]
while (notFound(key, e))
e = e.next
e
}
private[this] def notFound(key: A, e: Entry): Boolean = (e != null) && !elemEquals(e.key, key)

/* inlined HashTable.addEntry0 to preserve its visibility */
private[this] def addEntry(e: Entry, h: Int): B = {
if (tableSize >= threshold) addEntry(e)
else addEntry0(e, h)
e.value
}

/* extracted to make addEntry inlinable */
private[this] def addEntry0(e: Entry, h: Int) {
e.next = table(h).asInstanceOf[Entry]
table(h) = e
tableSize += 1
nnSizeMapAdd(h)
}

override def put(key: A, value: B): Option[B] = {
val e = findOrAddEntry(key, value)
if (e eq null) None
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