Value Members

1.  final def !=(arg0: Any): Boolean

   Definition Classes

   AnyRef → Any

2.  final def ##(): Int

   Definition Classes

   AnyRef → Any

3.  def +(other: String): String

   Implicit

   This member is added by an implicit conversion from BoxUnbox[BT] to any2stringadd[BoxUnbox[BT]] performed by method any2stringadd in scala.Predef.

   Definition Classes

   any2stringadd

4.  def ->[B](y: B): (BoxUnbox[BT], B)

   Implicit

   This member is added by an implicit conversion from BoxUnbox[BT] to ArrowAssoc[BoxUnbox[BT]] performed by method ArrowAssoc in scala.Predef.

   Definition Classes

   ArrowAssoc

   Annotations

   @inline()

5.  final def ==(arg0: Any): Boolean

   Definition Classes

   AnyRef → Any

6.  def allCreationsConsumers(initialCreation: BoxCreation, boxKind: BoxKind, prodCons: ProdConsAnalyzer): Option[(Set[BoxCreation], Set[BoxConsumer])]

   Given a box creations operation

   Given a box creations operation

   • find all ultimate consumers for the produced value. then:
     • for all consumed values, find all producer operations. check that all are box creations
       • recurse until reaching a fixpoint

   Returns a set of box creations and a set of box consumers. Note that the box consumers may contain EscapingConsumers, even if there are multiple box creation operations. The callee will handle this case (and not attempt to eliminate the box).

7.  final def asInstanceOf[T0]: T0

   Definition Classes

   Any

8.  def boxUnboxElimination(method: MethodNode, owner: InternalName): Boolean

   Eliminate box-unbox pairs within method.

   Eliminate box-unbox pairs within method. Such appear commonly after closure elimination:

   def t2 = { val f = (b: Byte, i: Int) => i + b // no specialized variant for this function type f(1, 2) // invokes the generic apply }

   The closure optimizer re-writes the apply call to anonfun$adapted method, which takes boxed arguments. After inlining this method, we get

   def t2 = { val a = boxByte(1) val b = boxInteger(2) val r = boxInteger(anonfun$(unboxByte(a), unboxInt(b))) unboxInt(r) }

   All these box/unbox operations are eliminated here.

   Implementation: for every box operation, find all consumers of the boxed value, then all producers of these consumers, repeat until reaching a fixpoint. If this results in a set of boxing and unboxing operations, the box can be eliminated.

   There are two methods for eliminating boxes: M1: If there is a single boxing operation, the boxed value(s) are stored into new local variable(s) at the allocation site. Accesses to the boxed value are re-written to reads / writes of these locals. Advantages:

   • supports mutable boxes (IntRef and friends)
   • supports eliminating unbox operations even if the box object needs to be created because it escapes (see E4)
     • works by keeping the unboxed value(s) in locals AND the box in its original form
     • only for immutable boxes: modifications to the escaped box cannot be applied to the local variable(s) holding the boxed value(s). Restriction:
   • does not work if there are multiple boxing operations (see E1)

   M2: If there are multiple boxing operations, the boxing operations are simply eliminated, leaving the unboxed value(s) on the stack. Store / load operations that previously acted on the box are adapted to handle the boxed type(s). If the box contains multiple values (or a size-2 value, which doesn't fit into locals that were used for the box), new local slots are used for store / load operations. Restrictions:

   • does not support re-writing writes to (mutable) boxes (see E2)
   • does not support re-writing reads of boxes that also escape (see E3)

   E1: M1 only works if there's a single boxing operation. def e1(b: Boolean) = { val i: Integer = box(10) // 10 is stored into a new local, box operation and i removed val j: Integer = box(20) // 20 is stored into a new local, box operation and j removed val r = if (b) i else j // loads and stores of the box are eliminated, r no longer exists unbox(r) // cannot rewrite: we don't know which local to load } Note: the example has no write and the box does not escape, so M2 works here.

   E2: mutable boxes with multiple boxing operations cannot be eliminated. M1: see E1 M2: cannot replace an IntRef on the stack by an Int value on the stack, an Int on the stack cannot be modified.

   def e2(b: Boolean) = { val r1 = new IntRef(0) val r2 = new IntRef(1) val modRef = if (b) r1 else r2 modRef.elem += 10 // M1: cannot rewrite: which local to write? same as E1. (if (b) r1 else r2).elem += 10 // M2: cannot change an Int on the stack (r1.elem, r2.elem) }

   E3: escaping boxes with multiple boxing operations cannot be rewritten. M1: see E1. M2: at *, instead of an Integer, an Int is on the stack, but the escape method expects an Integer. We cannot just create a box at this point: if there are multiple escapes (or an escape is executed more than once), the difference could be observed (reference equality).

   def e3(b: Boolean) = { val i: Integer = box(1) val j: Integer = box(2) escape(if (b) i else j) // * unbox(if (b) i else j) }

   E4: M1 supports rewriting unbox operations of immutable boxes that escape def e4 = { val i: Integer = box(10) // 10 is stored into a new local, loaded as argument for the box call escape(i) // not changed, still loads the local i holding the box unbox(i) // rewritten to a pop (of the box) and a load of the local variable }

   E4 seems to be a bit of a corner case, but it's necessary to unblock box eliminations with mutual dependencies. Example:

   val ((a, b), c) = ((1, 2), 3) a + b + c

   generates (after a few cleanups) the following (pseudo-bytecode, ignoring primitive boxing, specialization):

   load 1, load 2, new Tuple2 // stack: Tuple2 load 3 // stack: Tuple2; Int val local1 = new Tuple2 val local2 = local1._1.asInstanceOf[Tuple2] val c = local1._2.asInstanceOf[Int] if (local2 == null) throw new MatchError(local1) val a = local2._1 val b = local2._2 a + b + c

   In order to eliminate the tuples, we first need to eliminate the outer tuple (stored in local1)

   • single box operation, so we use M1
   • there are three consumers of the outer tuple: local1._1, local1._2 and new MatchError(local1). in the last one, the tuple escapes.
   • note that the MatchError creation is dead code: local2 is never null. However, our nullness analysis cannot identify this: it does not track nullness through tuple stores and loads.
   • if we re-write the non-escaping consumers of the outer tuple, but keep the tuple allocation and the escaping consumer, we get the following:

   load 1, load 2 val newLocal1 = new Tuple2; load newLocal1 // stack: Tuple2 val newLocal2 = 3; load newLocal2 // stack: Tuple2; Int val local1 = new Tuple2 val local2 = newLocal1 val c = newLocal2 if (local2 == null) throw new MatchError(local1) val a = local2._1 val b = local2._2 a + b + c

   At this point, the nullness analysis sees that local2 == null is false, dead code elimination removes the throw new MatchError(local1). After eliminating the allocation of the outer tuple, the inner tuple (stored in newLocal1) can also be eliminated.

   Special case for tuples wrt specialization: a tuple getter may box or unbox the value stored in the tuple: calling _1 on a Tuple2$mcII$sp boxes the primitive Int stored in the tuple. Similarly, calling _1$mcI$sp on a non-specialized Tuple2 unboxes the Integer in the tuple. When eliminating such getters, we have to introduce appropriate box / unbox calls.

   TODO: add new calls (box / unbox) to the call graph (not urgent) TODO: update the call graph because stack heights change (not urgent). this may also affect other optimizations, we ignored the issue so far. check how stack heights stored in the call graph are used. Note: these tasks are not urgent because the call graph is not currently used during / after method-local optimizations, only before to perform inlining and closure rewriting.

9.  val btypes: BT
10.  def checkCopyOpReplacements(initialProds: Set[BoxCreation], finalCons: Set[BoxConsumer], valueTypes: List[Type], nextLocal: Int, prodCons: ProdConsAnalyzer): Option[(Map[AbstractInsnNode, List[AbstractInsnNode]], Int, Map[Int, Type])]

    Takes two sets initialProds and finalCons such that all boxes produced by the first set are only consumed by an operation in the second set.

    Takes two sets initialProds and finalCons such that all boxes produced by the first set are only consumed by an operation in the second set.

    Returns a map that replaces copy operations (ALOAD / ASTORE) between the producers and consumers with corresponding copy operations for the values stored in the box. The returned Int value returns the next free local variable slot.

    Examples:

    • for an Integer box, an ASTORE x is simply replaced by ISTORE x
    • for a pair of two references, an ASTORE x is replaced by ASTORE x1; ASTORE x2 where x1 and x2 are fresh locals

    Not all copy operations can be supported: DUP only works for single-value boxes, the more exotic copy operations (DUP2_X2) are not supported (note that Scalac never emits them). If a copy operation cannot be replaced, this method returns None.

11.  def clone(): AnyRef

    Attributes

    protected[java.lang]

    Definition Classes

    AnyRef

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    @throws( ... )

12.  def ensuring(cond: (BoxUnbox[BT]) ⇒ Boolean, msg: ⇒ Any): BoxUnbox[BT]

    Implicit

    This member is added by an implicit conversion from BoxUnbox[BT] to Ensuring[BoxUnbox[BT]] performed by method Ensuring in scala.Predef.

    Definition Classes

    Ensuring

13.  def ensuring(cond: (BoxUnbox[BT]) ⇒ Boolean): BoxUnbox[BT]

    Implicit

    This member is added by an implicit conversion from BoxUnbox[BT] to Ensuring[BoxUnbox[BT]] performed by method Ensuring in scala.Predef.

    Definition Classes

    Ensuring

14.  def ensuring(cond: Boolean, msg: ⇒ Any): BoxUnbox[BT]

    Implicit

    This member is added by an implicit conversion from BoxUnbox[BT] to Ensuring[BoxUnbox[BT]] performed by method Ensuring in scala.Predef.

    Definition Classes

    Ensuring

15.  def ensuring(cond: Boolean): BoxUnbox[BT]

    Implicit

    This member is added by an implicit conversion from BoxUnbox[BT] to Ensuring[BoxUnbox[BT]] performed by method Ensuring in scala.Predef.

    Definition Classes

    Ensuring

16.  final def eq(arg0: AnyRef): Boolean

    Definition Classes

    AnyRef

17.  def equals(arg0: Any): Boolean

    Definition Classes

    AnyRef → Any

18.  def finalize(): Unit

    Attributes

    protected[java.lang]

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    AnyRef

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    @throws( classOf[java.lang.Throwable] )

19.  def formatted(fmtstr: String): String

    Implicit

    This member is added by an implicit conversion from BoxUnbox[BT] to StringFormat[BoxUnbox[BT]] performed by method StringFormat in scala.Predef.

    Definition Classes

    StringFormat

    Annotations

    @inline()

20.  final def getClass(): Class[_]

    Definition Classes

    AnyRef → Any

21.  def hashCode(): Int

    Definition Classes

    AnyRef → Any

22.  final def isInstanceOf[T0]: Boolean

    Definition Classes

    Any

23.  final def ne(arg0: AnyRef): Boolean

    Definition Classes

    AnyRef

24.  final def notify(): Unit

    Definition Classes

    AnyRef

25.  final def notifyAll(): Unit

    Definition Classes

    AnyRef

26.  final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes

    AnyRef

27.  def toString(): String

    Definition Classes

    AnyRef → Any

28.  final def wait(): Unit

    Definition Classes

    AnyRef

    Annotations

    @throws( ... )

29.  final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes

    AnyRef

    Annotations

    @throws( ... )

30.  final def wait(arg0: Long): Unit

    Definition Classes

    AnyRef

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    @throws( ... )

31.  def →[B](y: B): (BoxUnbox[BT], B)

    Implicit

    This member is added by an implicit conversion from BoxUnbox[BT] to ArrowAssoc[BoxUnbox[BT]] performed by method ArrowAssoc in scala.Predef.

    Definition Classes

    ArrowAssoc

32.  object BoxKind
33.  object PrimitiveBox extends Serializable
34.  object Ref extends Serializable
35.  object Tuple extends Serializable