Add some benchmarks in tupleCons

Author: Antoine Brunner

bench-run/src/main/scala/dotty/tools/benchmarks/tuples/Concat.scala

@@ -10,8 +10,6 @@ class Concat {
   var sizes: String = _
   var tuple1: Tuple = _
   var tuple2: Tuple = _
-  var array1: Array[Object] = _
-  var array2: Array[Object] = _
 
   def tupleOfSize(n: Int): Tuple = {
     var t: Tuple = ()

bench-run/src/main/scala/dotty/tools/benchmarks/tuples/Cons.scala

@@ -8,18 +8,33 @@ class Cons {
   @Param(Array("0"))
   var size: Int = _
   var tuple: Tuple = _
-  var array: Array[Object] = _
+  var array1: Array[Object] = _
+  var array2: Array[Object] = _
 
   @Setup
   def setup(): Unit = {
     tuple = ()
 
     for (i <- 1 to size)
       tuple = "elem" *: tuple
+
+    array1 = new Array[Object](size)
+    array2 = new Array[Object](size + 1)
   }
 
   @Benchmark
   def tupleCons(): Tuple = {
     DynamicTuple.dynamicCons("elem", tuple)
   }
+
+  @Benchmark
+  def createArray(): Array[Object] = {
+    new Array[Object](size + 1)
+  }
+
+  @Benchmark
+  def consArray(): Array[Object] = {
+    System.arraycopy(array1, 0, array2, 1, size)
+    array2
+  }
 }