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nicolasstuckinicolasstucki
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Fix #502: Optimize Array.apply([...]) to [...] 
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‎compiler/src/dotty/tools/dotc/Compiler.scala

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@@ -92,6 +92,7 @@ class Compiler {
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List(new Erasure) :: // Rewrite types to JVM model, erasing all type parameters, abstract types and refinements.
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List(new ElimErasedValueType, // Expand erased value types to their underlying implmementation types
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new VCElideAllocations, // Peep-hole optimization to eliminate unnecessary value class allocations
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new ArrayApply, // Optimize `scala.Array.apply([....])` and `scala.Array.apply(..., [....])` into `[...]`
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new ElimPolyFunction, // Rewrite PolyFunction subclasses to FunctionN subclasses
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new TailRec, // Rewrite tail recursion to loops
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new Mixin, // Expand trait fields and trait initializers

‎compiler/src/dotty/tools/dotc/transform/ArrayApply.scala

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package dotty.tools.dotc
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package transform
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import core._
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import MegaPhase._
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import Contexts.Context
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import Symbols._
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import Types._
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import StdNames._
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import ast.Trees._
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import dotty.tools.dotc.ast.tpd
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/** This phase rewrites calls to `Array.apply` to primitive array instantion.
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*
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* Transforms `scala.Array.apply([....])` and `scala.Array.apply(..., [....])` into `[...]`
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*/
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class ArrayApply extends MiniPhase {
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import tpd._
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override def phaseName: String = "arrayApply"
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override def transformApply(tree: tpd.Apply)(implicit ctx: Context): tpd.Tree = {
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if (tree.symbol.name == nme.apply && tree.symbol.owner == defn.ArrayModule) { // Is `Array.apply`
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tree.args match {
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case CleanTree(Apply(wrapRefArrayMeth, (seqLit: tpd.JavaSeqLiteral) :: Nil)) :: ct :: Nil
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if defn.WrapArrayMethods().contains(wrapRefArrayMeth.symbol) && elideClassTag(ct) =>
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seqLit
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case elem0 :: CleanTree(Apply(wrapRefArrayMeth, (seqLit: tpd.JavaSeqLiteral) :: Nil)) :: Nil
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if defn.WrapArrayMethods().contains(wrapRefArrayMeth.symbol) =>
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tpd.JavaSeqLiteral(elem0 :: seqLit.elems, seqLit.elemtpt)
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case _ =>
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tree
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}
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} else tree
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}
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// Only optimize when classtag is `ClassTag.apply` or `ClassTag.{Byte, Boolean, ...}`
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private def elideClassTag(ct: Tree)(implicit ctx: Context): Boolean = {
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ct.symbol.maybeOwner.companionModule == defn.ClassTagModule
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}
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object CleanTree {
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def unapply(tree: Tree)(implicit ctx: Context): Some[Tree] = tree match {
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case Block(Nil, expr) => unapply(expr)
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case Typed(expr, _) => unapply(expr)
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case _ => Some(tree)
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}
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}
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}

‎compiler/test/dotty/tools/backend/jvm/ArrayApplyOptTest.scala

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package dotty.tools.backend.jvm
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import org.junit.Test
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import org.junit.Assert._
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import scala.tools.asm.Opcodes._
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class ArrayApplyOptTest extends DottyBytecodeTest {
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import ASMConverters._
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@Test def testArrayEmptyGenericApply= {
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test("Array[String]()", List(Op(ICONST_0), TypeOp(ANEWARRAY, "java/lang/String"), Op(POP), Op(RETURN)))
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test("Array[Unit]()", List(Op(ICONST_0), TypeOp(ANEWARRAY, "scala/runtime/BoxedUnit"), Op(POP), Op(RETURN)))
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test("Array[Object]()", List(Op(ICONST_0), TypeOp(ANEWARRAY, "java/lang/Object"), Op(POP), Op(RETURN)))
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test("Array[Boolean]()", List(Op(ICONST_0), IntOp(NEWARRAY, 4), Op(POP), Op(RETURN)))
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test("Array[Char]()", List(Op(ICONST_0), IntOp(NEWARRAY, 5), Op(POP), Op(RETURN)))
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test("Array[Float]()", List(Op(ICONST_0), IntOp(NEWARRAY, 6), Op(POP), Op(RETURN)))
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test("Array[Double]()", List(Op(ICONST_0), IntOp(NEWARRAY, 7), Op(POP), Op(RETURN)))
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test("Array[Byte]()", List(Op(ICONST_0), IntOp(NEWARRAY, 8), Op(POP), Op(RETURN)))
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test("Array[Short]()", List(Op(ICONST_0), IntOp(NEWARRAY, 9), Op(POP), Op(RETURN)))
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test("Array[Int]()", List(Op(ICONST_0), IntOp(NEWARRAY, 10), Op(POP), Op(RETURN)))
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test("Array[Long]()", List(Op(ICONST_0), IntOp(NEWARRAY, 11), Op(POP), Op(RETURN)))
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test("Array[T]()", List(Op(ICONST_0), IntOp(NEWARRAY, 10), Op(POP), Op(RETURN)))
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}
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@Test def testArrayGenericApply= {
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test("""Array("a", "b")""", List(Op(ICONST_2), TypeOp(ANEWARRAY, "java/lang/String"), Op(DUP), Op(ICONST_0), Ldc(LDC, "a"), Op(AASTORE), Op(DUP), Op(ICONST_1), Ldc(LDC, "b"), Op(AASTORE), Op(POP), Op(RETURN)))
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test("""Array[Object]("a", "b")""", List(Op(ICONST_2), TypeOp(ANEWARRAY, "java/lang/Object"), Op(DUP), Op(ICONST_0), Ldc(LDC, "a"), Op(AASTORE), Op(DUP), Op(ICONST_1), Ldc(LDC, "b"), Op(AASTORE), Op(POP), Op(RETURN)))
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}
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@Test def testArrayApplyBoolean =
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test("Array(true, false)", List(Op(ICONST_2), IntOp(NEWARRAY, 4), Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(BASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_0), Op(BASTORE), Op(POP), Op(RETURN)))
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@Test def testArrayApplyByte =
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test("Array[Byte](1, 2)", List(Op(ICONST_2), IntOp(NEWARRAY, 8), Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(BASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_2), Op(BASTORE), Op(POP), Op(RETURN)))
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@Test def testArrayApplyShort =
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test("Array[Short](1, 2)", List(Op(ICONST_2), IntOp(NEWARRAY, 9), Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(SASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_2), Op(SASTORE), Op(POP), Op(RETURN)))
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@Test def testArrayApplyInt = {
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test("Array(1, 2)", List(Op(ICONST_2), IntOp(NEWARRAY, 10), Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(IASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_2), Op(IASTORE), Op(POP), Op(RETURN)))
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test("""Array[T](t, t)""", List(Op(ICONST_2), IntOp(NEWARRAY, 10), Op(DUP), Op(ICONST_0), Field(GETSTATIC, "Foo$", "MODULE$", "LFoo$;"), Invoke(INVOKEVIRTUAL, "Foo$", "t", "()I", false), Op(IASTORE), Op(DUP), Op(ICONST_1), Field(GETSTATIC, "Foo$", "MODULE$", "LFoo$;"), Invoke(INVOKEVIRTUAL, "Foo$", "t", "()I", false), Op(IASTORE), Op(POP), Op(RETURN)))
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}
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@Test def testArrayApplyLong =
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test("Array(2L, 3L)", List(Op(ICONST_2), IntOp(NEWARRAY, 11), Op(DUP), Op(ICONST_0), Ldc(LDC, 2), Op(LASTORE), Op(DUP), Op(ICONST_1), Ldc(LDC, 3), Op(LASTORE), Op(POP), Op(RETURN)))
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@Test def testArrayApplyFloat =
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test("Array(2.1f, 3.1f)", List(Op(ICONST_2), IntOp(NEWARRAY, 6), Op(DUP), Op(ICONST_0), Ldc(LDC, 2.1f), Op(FASTORE), Op(DUP), Op(ICONST_1), Ldc(LDC, 3.1f), Op(FASTORE), Op(POP), Op(RETURN)))
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@Test def testArrayApplyDouble =
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test("Array(2.2d, 3.2d)", List(Op(ICONST_2), IntOp(NEWARRAY, 7), Op(DUP), Op(ICONST_0), Ldc(LDC, 2.2d), Op(DASTORE), Op(DUP), Op(ICONST_1), Ldc(LDC, 3.2d), Op(DASTORE), Op(POP), Op(RETURN)))
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@Test def testArrayApplyChar =
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test("Array('x', 'y')", List(Op(ICONST_2), IntOp(NEWARRAY, 5), Op(DUP), Op(ICONST_0), IntOp(BIPUSH, 120), Op(CASTORE), Op(DUP), Op(ICONST_1), IntOp(BIPUSH, 121), Op(CASTORE), Op(POP), Op(RETURN)))
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@Test def testArrayApplyUnit =
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test("Array[Unit]((), ())", List(Op(ICONST_2), TypeOp(ANEWARRAY, "scala/runtime/BoxedUnit"), Op(DUP),
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Op(ICONST_0), Field(GETSTATIC, "scala/runtime/BoxedUnit", "UNIT", "Lscala/runtime/BoxedUnit;"), Op(AASTORE), Op(DUP),
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Op(ICONST_1), Field(GETSTATIC, "scala/runtime/BoxedUnit", "UNIT", "Lscala/runtime/BoxedUnit;"), Op(AASTORE), Op(POP), Op(RETURN)))
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@Test def testArrayInlined = test(
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"""{
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| inline def array(xs: =>Int*): Array[Int] = Array(xs: _*)
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| array(1, 2)
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|}""".stripMargin,
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List(Op(ICONST_2), IntOp(NEWARRAY, 10), Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(IASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_2), Op(IASTORE), TypeOp(CHECKCAST, "[I"), Op(POP), Op(RETURN))
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)
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@Test def testArrayInlined2 = test(
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"""{
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| inline def array(x: =>Int, xs: =>Int*): Array[Int] = Array(x, xs: _*)
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| array(1, 2)
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|}""".stripMargin,
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List(Op(ICONST_2), IntOp(NEWARRAY, 10), Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(IASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_2), Op(IASTORE), Op(POP), Op(RETURN))
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)
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private def test(code: String, expectedInstructions: List[Any])= {
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val source =
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s"""class Foo {
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| import Foo._
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| def test: Unit = $code
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|}
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|object Foo {
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| opaque type T = Int
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| def t: T = 1
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|}
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""".stripMargin
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checkBCode(source) { dir =>
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val clsIn = dir.lookupName("Foo.class", directory = false).input
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val clsNode = loadClassNode(clsIn)
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val meth = getMethod(clsNode, "test")
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val instructions = instructionsFromMethod(meth)
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assertEquals(expectedInstructions, instructions)
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}
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}
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}

‎tests/run/i502.check

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Ok
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foo

‎tests/run/i502.scala

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import scala.reflect.ClassTag
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object Test extends App {
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Array[Int](1, 2)
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try {
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Array[Int](1, 2)(null)
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???
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} catch {
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case _: NullPointerException => println("Ok")
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}
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Array[Int](1, 2)({println("foo"); the[ClassTag[Int]]})
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}

‎tests/run/t6611b.scala

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object Test extends App {
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val a = Array("1")
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val a2 = Array(a: _*)
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a2(0) = "2"
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assert(a(0) == "1")
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}

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