Add global benchmark on tuples

Author: Antoine Brunner

bench-run/src/main/scala/tuples/TupleOps.scala

@@ -0,0 +1,46 @@
+package dotty.tools.benchmarks.tuples
+
+import org.openjdk.jmh.annotations._
+
+@State(Scope.Thread)
+class TupleOps {
+  var tuple1: Tuple = _
+  var tuple2: Tuple = _
+
+  @Setup
+  def setup(): Unit = {
+    tuple1 = ()
+    for (i <- 1 until 15)
+      tuple1 = s"elem$i" *: tuple1
+
+    tuple2 = ()
+    for (i <- 1 until 10)
+      tuple2 = s"elem$i" *: tuple2
+  }
+
+  def tupleFlatMap(tuple: Tuple, f: [A] => A => Tuple): Tuple = {
+    def tailRecFlatMap(t: Tuple, acc: Tuple): Tuple = t match {
+      case () => acc
+      case x *: rest => tailRecFlatMap(rest, acc ++ f(x))
+    }
+    tailRecFlatMap(tuple, ())
+  }
+
+  def tupleReverse(tuple: Tuple): Tuple = {
+    def tailRecReverse(t: Tuple, acc: Tuple): Tuple = t match {
+      case () => acc
+      case x *: rest => tailRecReverse(rest, x *: acc)
+    }
+    tailRecReverse(tuple, ())
+  }
+
+  @Benchmark
+  def reverse(): Tuple = {
+    tupleReverse(tuple1)
+  }
+
+  @Benchmark
+  def flatMap(): Tuple = {
+    tupleFlatMap(tuple2, [A] => (x: A) => (x, x))
+  }
+}