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Merged
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Apr 14, 2020
Merged

Better cast elision, fix an issue with tailrec #8713

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672daa8
Better cast elision
smarter Apr 12, 2020
82e7d20
Improve ArrayApplyOptTest
smarter Apr 13, 2020
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4 changes: 2 additions & 2 deletions compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala
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Expand Up @@ -240,8 +240,8 @@ object TypeTestsCasts {

def transformAsInstanceOf(testType: Type): Tree = {
def testCls = testType.widen.classSymbol
if (expr.tpe <:< testType)
Typed(expr, tree.args.head)
if (erasure(expr.tpe) <:< testType)
Typed(expr, tree.args.head) // Replace cast by type ascription (which does not generate any bytecode)
else if (testCls eq defn.BoxedUnitClass)
// as a special case, casting to Unit always successfully returns Unit
Block(expr :: Nil, Literal(Constant(()))).withSpan(expr.span)
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26 changes: 13 additions & 13 deletions compiler/test/dotty/tools/backend/jvm/ArrayApplyOptTest.scala
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Expand Up @@ -51,53 +51,53 @@ class ArrayApplyOptTest extends DottyBytecodeTest {
@Test def testArrayApplyBoolean = {
val init = List(Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(BASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_0), Op(BASTORE))
test("Array(true, false)", newArray2Opcodes(T_BOOLEAN, init))
test("IArray(true, false)", newArray2Opcodes(T_BOOLEAN, init :+ TypeOp(CHECKCAST, "[Z")))
test("IArray(true, false)", newArray2Opcodes(T_BOOLEAN, init))
}

@Test def testArrayApplyByte = {
val init = List(Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(BASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_2), Op(BASTORE))
test("Array[Byte](1, 2)", newArray2Opcodes(T_BYTE, init))
test("IArray[Byte](1, 2)", newArray2Opcodes(T_BYTE, init :+ TypeOp(CHECKCAST, "[B")))
test("Array(1: Byte, 2: Byte)", newArray2Opcodes(T_BYTE, init))
test("IArray(1: Byte, 2: Byte)", newArray2Opcodes(T_BYTE, init))
}

@Test def testArrayApplyShort = {
val init = List(Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(SASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_2), Op(SASTORE))
test("Array[Short](1, 2)", newArray2Opcodes(T_SHORT, init))
test("IArray[Short](1, 2)", newArray2Opcodes(T_SHORT, init :+ TypeOp(CHECKCAST, "[S")))
test("Array(1: Short, 2: Short)", newArray2Opcodes(T_SHORT, init))
test("IArray(1: Short, 2: Short)", newArray2Opcodes(T_SHORT, init))
}

@Test def testArrayApplyInt = {
val init = List(Op(DUP), Op(ICONST_0), Op(ICONST_1), Op(IASTORE), Op(DUP), Op(ICONST_1), Op(ICONST_2), Op(IASTORE))
test("Array(1, 2)", newArray2Opcodes(T_INT, init))
test("IArray(1, 2)", newArray2Opcodes(T_INT, init :+ TypeOp(CHECKCAST, "[I")))
test("IArray(1, 2)", newArray2Opcodes(T_INT, init))

val init2 = List(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))
test("""Array[T](t, t)""", newArray2Opcodes(T_INT, init2))
test("""IArray[T](t, t)""", newArray2Opcodes(T_INT, init2 :+ TypeOp(CHECKCAST, "[I")))
val init2 = List(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), TypeOp(CHECKCAST, "[I"))
test("""Array[T](t, t): Array[T]""", newArray2Opcodes(T_INT, init2))
test("""IArray[T](t, t): IArray[T]""", newArray2Opcodes(T_INT, init2))
}

@Test def testArrayApplyLong = {
val init = List(Op(DUP), Op(ICONST_0), Ldc(LDC, 2), Op(LASTORE), Op(DUP), Op(ICONST_1), Ldc(LDC, 3), Op(LASTORE))
test("Array(2L, 3L)", newArray2Opcodes(T_LONG, init))
test("IArray(2L, 3L)", newArray2Opcodes(T_LONG, init :+ TypeOp(CHECKCAST, "[J")))
test("IArray(2L, 3L)", newArray2Opcodes(T_LONG, init))
}

@Test def testArrayApplyFloat = {
val init = List(Op(DUP), Op(ICONST_0), Ldc(LDC, 2.1f), Op(FASTORE), Op(DUP), Op(ICONST_1), Ldc(LDC, 3.1f), Op(FASTORE))
test("Array(2.1f, 3.1f)", newArray2Opcodes(T_FLOAT, init))
test("IArray(2.1f, 3.1f)", newArray2Opcodes(T_FLOAT, init :+ TypeOp(CHECKCAST, "[F")))
test("IArray(2.1f, 3.1f)", newArray2Opcodes(T_FLOAT, init))
}

@Test def testArrayApplyDouble = {
val init = List(Op(DUP), Op(ICONST_0), Ldc(LDC, 2.2d), Op(DASTORE), Op(DUP), Op(ICONST_1), Ldc(LDC, 3.2d), Op(DASTORE))
test("Array(2.2d, 3.2d)", newArray2Opcodes(T_DOUBLE, init))
test("IArray(2.2d, 3.2d)", newArray2Opcodes(T_DOUBLE, init :+ TypeOp(CHECKCAST, "[D")))
test("IArray(2.2d, 3.2d)", newArray2Opcodes(T_DOUBLE, init))
}

@Test def testArrayApplyChar = {
val init = List(Op(DUP), Op(ICONST_0), IntOp(BIPUSH, 120), Op(CASTORE), Op(DUP), Op(ICONST_1), IntOp(BIPUSH, 121), Op(CASTORE))
test("Array('x', 'y')", newArray2Opcodes(T_CHAR, init))
test("IArray('x', 'y')", newArray2Opcodes(T_CHAR, init :+ TypeOp(CHECKCAST, "[C")))
test("IArray('x', 'y')", newArray2Opcodes(T_CHAR, init))
}

@Test def testArrayApplyUnit = {
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13 changes: 13 additions & 0 deletions tests/pos/i8712.scala
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@@ -0,0 +1,13 @@
import scala.annotation.tailrec

sealed trait Foo[+A]
case class Bar[A](f: Foo[A]) extends Foo[A]
case class Done[A](a: A) extends Foo[A]

object Test {
@tailrec
def runT[A](c: Foo[A]): A = c match {
case Bar(f) => runT(f)
case Done(a) => a
}
}