Merge pull request #1586 from retronym/ticket/6247

Optimize primitive Array(e1, ..., en)

3 files changed, 23 insertions, 10 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/CleanUp.scala b/src/compiler/scala/tools/nsc/transform/CleanUp.scala
index 16f6c80101..847ca574a9 100644
--- a/src/compiler/scala/tools/nsc/transform/CleanUp.scala
+++ b/src/compiler/scala/tools/nsc/transform/CleanUp.scala
@@ -624,11 +624,11 @@ abstract class CleanUp extends Transform with ast.TreeDSL {
       //
       // See SI-6611; we must *only* do this for literal vararg arrays.
       case Apply(appMeth, List(Apply(wrapRefArrayMeth, List(arg @ StripCast(ArrayValue(_, _)))), _))
-      if (wrapRefArrayMeth.symbol == Predef_wrapRefArray &&
-          appMeth.symbol == ArrayModule_overloadedApply.suchThat {
-            _.tpe.resultType.dealias.typeSymbol == ObjectClass  // [T: ClassTag](xs: T*): Array[T] post erasure
-          }) =>
+      if wrapRefArrayMeth.symbol == Predef_wrapRefArray && appMeth.symbol == ArrayModule_genericApply =>
         super.transform(arg)
+      case Apply(appMeth, List(elem0, Apply(wrapArrayMeth, List(rest @ ArrayValue(elemtpt, _)))))
+      if wrapArrayMeth.symbol == Predef_wrapArray(elemtpt.tpe) && appMeth.symbol == ArrayModule_apply(elemtpt.tpe) =>
+        super.transform(treeCopy.ArrayValue(rest, rest.elemtpt, elem0 :: rest.elems))
 
       case _ =>
         super.transform(tree)
diff --git a/src/library/scala/Array.scala b/src/library/scala/Array.scala
index 90684b5fdd..b9f51803ec 100644
--- a/src/library/scala/Array.scala
+++ b/src/library/scala/Array.scala
@@ -115,6 +115,8 @@ object Array extends FallbackArrayBuilding {
    *  @param xs the elements to put in the array
    *  @return an array containing all elements from xs.
    */
+  // Subject to a compiler optimization in Cleanup.
+  // Array(e0, ..., en) is translated to { val a = new Array(3); a(i) = ei; a }
   def apply[T: ClassTag](xs: T*): Array[T] = {
     val array = new Array[T](xs.length)
     var i = 0
@@ -123,6 +125,7 @@ object Array extends FallbackArrayBuilding {
   }
 
   /** Creates an array of `Boolean` objects */
+  // Subject to a compiler optimization in Cleanup, see above.
   def apply(x: Boolean, xs: Boolean*): Array[Boolean] = {
     val array = new Array[Boolean](xs.length + 1)
     array(0) = x
@@ -132,6 +135,7 @@ object Array extends FallbackArrayBuilding {
   }
 
   /** Creates an array of `Byte` objects */
+  // Subject to a compiler optimization in Cleanup, see above.
   def apply(x: Byte, xs: Byte*): Array[Byte] = {
     val array = new Array[Byte](xs.length + 1)
     array(0) = x
@@ -141,6 +145,7 @@ object Array extends FallbackArrayBuilding {
   }
 
   /** Creates an array of `Short` objects */
+  // Subject to a compiler optimization in Cleanup, see above.
   def apply(x: Short, xs: Short*): Array[Short] = {
     val array = new Array[Short](xs.length + 1)
     array(0) = x
@@ -150,6 +155,7 @@ object Array extends FallbackArrayBuilding {
   }
 
   /** Creates an array of `Char` objects */
+  // Subject to a compiler optimization in Cleanup, see above.
   def apply(x: Char, xs: Char*): Array[Char] = {
     val array = new Array[Char](xs.length + 1)
     array(0) = x
@@ -159,6 +165,7 @@ object Array extends FallbackArrayBuilding {
   }
 
   /** Creates an array of `Int` objects */
+  // Subject to a compiler optimization in Cleanup, see above.
   def apply(x: Int, xs: Int*): Array[Int] = {
     val array = new Array[Int](xs.length + 1)
     array(0) = x
@@ -168,6 +175,7 @@ object Array extends FallbackArrayBuilding {
   }
 
   /** Creates an array of `Long` objects */
+  // Subject to a compiler optimization in Cleanup, see above.
   def apply(x: Long, xs: Long*): Array[Long] = {
     val array = new Array[Long](xs.length + 1)
     array(0) = x
@@ -177,6 +185,7 @@ object Array extends FallbackArrayBuilding {
   }
 
   /** Creates an array of `Float` objects */
+  // Subject to a compiler optimization in Cleanup, see above.
   def apply(x: Float, xs: Float*): Array[Float] = {
     val array = new Array[Float](xs.length + 1)
     array(0) = x
@@ -186,6 +195,7 @@ object Array extends FallbackArrayBuilding {
   }
 
   /** Creates an array of `Double` objects */
+  // Subject to a compiler optimization in Cleanup, see above.
   def apply(x: Double, xs: Double*): Array[Double] = {
     val array = new Array[Double](xs.length + 1)
     array(0) = x
diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index 8e406b6f62..9a358cec46 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -360,12 +360,13 @@ trait Definitions extends api.StandardDefinitions {
     lazy val PredefModule      = requiredModule[scala.Predef.type]
     lazy val PredefModuleClass = PredefModule.moduleClass
 
-      def Predef_classOf      = getMemberMethod(PredefModule, nme.classOf)
-      def Predef_identity     = getMemberMethod(PredefModule, nme.identity)
-      def Predef_conforms     = getMemberMethod(PredefModule, nme.conforms)
-      def Predef_wrapRefArray = getMemberMethod(PredefModule, nme.wrapRefArray)
-      def Predef_???          = getMemberMethod(PredefModule, nme.???)
-      def Predef_implicitly   = getMemberMethod(PredefModule, nme.implicitly)
+      def Predef_classOf             = getMemberMethod(PredefModule, nme.classOf)
+      def Predef_identity            = getMemberMethod(PredefModule, nme.identity)
+      def Predef_conforms            = getMemberMethod(PredefModule, nme.conforms)
+    def Predef_wrapRefArray        = getMemberMethod(PredefModule, nme.wrapRefArray)
+    def Predef_wrapArray(tp: Type) = getMemberMethod(PredefModule, wrapArrayMethodName(tp))
+    def Predef_???                 = getMemberMethod(PredefModule, nme.???)
+    def Predef_implicitly          = getMemberMethod(PredefModule, nme.implicitly)
 
     /** Is `sym` a member of Predef with the given name?
      *  Note: DON't replace this by sym == Predef_conforms/etc, as Predef_conforms is a `def`
@@ -490,6 +491,8 @@ trait Definitions extends api.StandardDefinitions {
     // arrays and their members
     lazy val ArrayModule                   = requiredModule[scala.Array.type]
       lazy val ArrayModule_overloadedApply = getMemberMethod(ArrayModule, nme.apply)
+           def ArrayModule_genericApply    = ArrayModule_overloadedApply.suchThat(_.paramss.flatten.last.tpe.typeSymbol == ClassTagClass) // [T: ClassTag](xs: T*): Array[T]
+           def ArrayModule_apply(tp: Type) = ArrayModule_overloadedApply.suchThat(_.tpe.resultType =:= arrayType(tp)) // (p1: AnyVal1, ps: AnyVal1*): Array[AnyVal1]
     lazy val ArrayClass                    = getRequiredClass("scala.Array") // requiredClass[scala.Array[_]]
       lazy val Array_apply                 = getMemberMethod(ArrayClass, nme.apply)
       lazy val Array_update                = getMemberMethod(ArrayClass, nme.update)