LocalOpt - Scala Compiler 2.11.6 - scala.tools.nsc.backend.jvm.opt.LocalOpt
Keywords: LocalOpt Scala Compiler 2.11.6 scala.tools.nsc.backend.jvm.opt.LocalOpt

scala.tools.nsc.backend.jvm.opt

# LocalOpt

###
Related Doc: package opt

#### class LocalOpt extends AnyRef

Optimizations within a single method.

unreachable code

- removes instructions of basic blocks to which no branch instruction points + enables eliminating some exception handlers and local variable descriptors > eliminating them is required for correctness, as explained in `removeUnreachableCode`

empty exception handlers

- removes exception handlers whose try block is empty + eliminating a handler where the try block is empty and reachable will turn the catch block unreachable. in this case "unreachable code" is invoked recursively until reaching a fixpoint. > for try blocks that are unreachable, "unreachable code" removes also the instructions of the catch block, and the recursive invocation is not necessary.

simplify jumps

- various simplifications, see doc domments of individual optimizations + changing or eliminating jumps may render some code unreachable, therefore "simplify jumps" is executed in a loop with "unreachable code"

empty local variable descriptors

- removes entries from the local variable table where the variable is not actually used + enables eliminating labels that the entry points to (if they are not otherwise referenced)

empty line numbers

- eliminates line number nodes that describe no executable instructions + enables eliminating the label of the line number node (if it's not otherwise referenced)

stale labels

- eliminate labels that are not referenced, merge sequences of label definitions.

Source
  LocalOpt.scala

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1. LocalOpt
2. AnyRef
3. Any

Implicitly

1. by any2stringadd
2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

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### Instance Constructors

1. #### new LocalOpt(settings: ScalaSettings)

### Value Members

1. #### final def !=(arg0: Any): Boolean

   Test two objects for inequality.

   Test two objects for inequality.

   returns

     `true` if !(this == that), false otherwise.

   Definition Classes
     AnyRef → Any

2. #### final def ##(): Int

   Equivalent to `x.hashCode` except for boxed numeric types and `null`.

   Equivalent to `x.hashCode` except for boxed numeric types and `null`. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For `null` returns a hashcode where `null.hashCode` throws a `NullPointerException`.

   returns

     a hash value consistent with ==

   Definition Classes
     AnyRef → Any

3. #### def +(other: String): String

   Implicit information
     This member is added by an implicit conversion from LocalOpt to any2stringadd[LocalOpt] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd

4. #### def ->[B](y: B): (LocalOpt, B)

   Implicit information
     This member is added by an implicit conversion from LocalOpt to ArrowAssoc[LocalOpt] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()

5. #### final def ==(arg0: Any): Boolean

   The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   arg0

     the object to compare against this object for equality.

   returns

     `true` if the receiver object is equivalent to the argument; `false` otherwise.

   Definition Classes
     AnyRef → Any

6. #### final def asInstanceOf[T0]: T0

   Cast the receiver object to be of type `T0`.

   Cast the receiver object to be of type `T0`.

   Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression `1.asInstanceOf[String]` will throw a `ClassCastException` at runtime, while the expression `List(1).asInstanceOf[List[String]]` will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

   returns

     the receiver object.

   Definition Classes
     Any
   Exceptions thrown

     `ClassCastException` if the receiver object is not an instance of the erasure of type `T0`.

7. #### def clone(): AnyRef

   Create a copy of the receiver object.

   Create a copy of the receiver object.

   The default implementation of the `clone` method is platform dependent.

   returns

     a copy of the receiver object.

   Attributes
     protected[java.lang]
   Definition Classes
     AnyRef
   Annotations
     @throws( ... )
   Note

     not specified by SLS as a member of AnyRef

8. #### def compactLocalVariables(method: MethodNode): Boolean

   Compact the local variable slots used in the method's implementation.

   Compact the local variable slots used in the method's implementation. This prevents having unused slots for example after eliminating unreachable code.

   This transformation reduces the size of the frame for invoking the method. For example, if the method has an ISTORE instruction to the local variable 3, the maxLocals of the method is at least 4, even if some local variable slots below 3 are not used by any instruction.

   This could be improved by doing proper register allocation.

9. #### def ensuring(cond: (LocalOpt) ⇒ Boolean, msg: ⇒ Any): LocalOpt

   Implicit information
     This member is added by an implicit conversion from LocalOpt to Ensuring[LocalOpt] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

10. #### def ensuring(cond: (LocalOpt) ⇒ Boolean): LocalOpt

    Implicit information
      This member is added by an implicit conversion from LocalOpt to Ensuring[LocalOpt] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

11. #### def ensuring(cond: Boolean, msg: ⇒ Any): LocalOpt

    Implicit information
      This member is added by an implicit conversion from LocalOpt to Ensuring[LocalOpt] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

12. #### def ensuring(cond: Boolean): LocalOpt

    Implicit information
      This member is added by an implicit conversion from LocalOpt to Ensuring[LocalOpt] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

13. #### final def eq(arg0: AnyRef): Boolean

    Tests whether the argument (`arg0`) is a reference to the receiver object (`this`).

    Tests whether the argument (`arg0`) is a reference to the receiver object (`this`).

    The `eq` method implements an equivalence relation on non-null instances of `AnyRef`, and has three additional properties:

    - It is consistent: for any non-null instances `x` and `y` of type `AnyRef`, multiple invocations of `x.eq(y)` consistently returns `true` or consistently returns `false`.
    - For any non-null instance `x` of type `AnyRef`, `x.eq(null)` and `null.eq(x)` returns `false`.
    - `null.eq(null)` returns `true`.

    When overriding the `equals` or `hashCode` methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (`o1 eq o2`), they should be equal to each other (`o1 == o2`) and they should hash to the same value (`o1.hashCode == o2.hashCode`).

    returns

      `true` if the argument is a reference to the receiver object; `false` otherwise.

    Definition Classes
      AnyRef

14. #### def equals(arg0: Any): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to `eq`.

    See also `equals` in scala.Any.

    returns

      `true` if the receiver object is equivalent to the argument; `false` otherwise.

    Definition Classes
      AnyRef → Any

15. #### def finalize(): Unit

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the `finalize` method is invoked, as well as the interaction between `finalize` and non-local returns and exceptions, are all platform dependent.

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )
    Note

      not specified by SLS as a member of AnyRef

16. #### def formatted(fmtstr: String): String

    Implicit information
      This member is added by an implicit conversion from LocalOpt to StringFormat[LocalOpt] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()

17. #### final def getClass(): Class[_]

    A representation that corresponds to the dynamic class of the receiver object.

    A representation that corresponds to the dynamic class of the receiver object.

    The nature of the representation is platform dependent.

    returns

      a representation that corresponds to the dynamic class of the receiver object.

    Definition Classes
      AnyRef → Any
    Note

      not specified by SLS as a member of AnyRef

18. #### def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

      the hash code value for this object.

    Definition Classes
      AnyRef → Any

19. #### final def isInstanceOf[T0]: Boolean

    Test whether the dynamic type of the receiver object is `T0`.

    Test whether the dynamic type of the receiver object is `T0`.

    Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression `1.isInstanceOf[String]` will return `false`, while the expression `List(1).isInstanceOf[List[String]]` will return `true`. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

    returns

      `true` if the receiver object is an instance of erasure of type `T0`; `false` otherwise.

    Definition Classes
      Any

20. #### def methodOptimizations(clazz: ClassNode): Boolean

    Remove unreachable instructions from all (non-abstract) methods and apply various other cleanups to the bytecode.

    Remove unreachable instructions from all (non-abstract) methods and apply various other cleanups to the bytecode.

    clazz

      The class whose methods are optimized

    returns

      `true` if unreachable code was eliminated in some method, `false` otherwise.

21. #### final def ne(arg0: AnyRef): Boolean

    Equivalent to `!(this eq that)`.

    Equivalent to `!(this eq that)`.

    returns

      `true` if the argument is not a reference to the receiver object; `false` otherwise.

    Definition Classes
      AnyRef

22. #### final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
      AnyRef
    Note

      not specified by SLS as a member of AnyRef

23. #### final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
      AnyRef
    Note

      not specified by SLS as a member of AnyRef

24. #### def removeEmptyExceptionHandlers(method: MethodNode): Set[TryCatchBlockNode]

    Remove exception handlers that cover empty code blocks.

    Remove exception handlers that cover empty code blocks. A block is considered empty if it consist only of labels, frames, line numbers, nops and gotos.

    There are no executable instructions that we can assume don't throw (eg ILOAD). The JVM spec basically says that a VirtualMachineError may be thrown at any time: http://docs.oracle.com/javase/specs/jvms/se8/html/jvms-6.html#jvms-6.3

    Note that no instructions are eliminated.

    returns

      the set of removed handlers

25. #### def removeEmptyLabelNodes(method: MethodNode): Boolean

    Removes unreferenced label declarations, also squashes sequences of label definitions.

    Removes unreferenced label declarations, also squashes sequences of label definitions.

    [ops]; Label(a); Label(b); [ops];

    ### > subs([ops], b, a); Label(a); subs([ops], b, a);

26. #### def removeEmptyLineNumbers(method: MethodNode): Boolean

    Removes LineNumberNodes that don't describe any executable instructions.

    Removes LineNumberNodes that don't describe any executable instructions.

    This method expects (and asserts) that the `start` label of each LineNumberNode is the lexically preceding label declaration.

27. #### def removeUnreachableCodeImpl(method: MethodNode, ownerClassName: String): (Boolean, Set[LabelNode])

    Removes unreachable basic blocks.

    Removes unreachable basic blocks.

    TODO: rewrite, don't use computeMaxLocalsMaxStack (runs a ClassWriter) / Analyzer. Too slow.

28. #### def removeUnusedLocalVariableNodes(method: MethodNode)(fistLocalIndex: Int = parametersSize(method), renumber: (Int) ⇒ Int = identity): Boolean

    Remove all non-parameter entries from the local variable table which denote variables that are not actually read or written.

    Remove all non-parameter entries from the local variable table which denote variables that are not actually read or written.

    Note that each entry in the local variable table has a start, end and index. Two entries with the same index, but distinct start / end ranges are different variables, they may have not the same type or name.

29. #### def simplifyJumps(method: MethodNode): Boolean

    Apply various simplifications to branching instructions.

30. #### final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
      AnyRef

31. #### def toString(): String

    Creates a String representation of this object.

    Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

    returns

      a String representation of the object.

    Definition Classes
      AnyRef → Any

32. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

33. #### final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

34. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

35. #### def →[B](y: B): (LocalOpt, B)

    Implicit information
      This member is added by an implicit conversion from LocalOpt to ArrowAssoc[LocalOpt] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from LocalOpt to any2stringadd[LocalOpt]

### Inherited by implicit conversion StringFormat from LocalOpt to StringFormat[LocalOpt]

### Inherited by implicit conversion Ensuring from LocalOpt to Ensuring[LocalOpt]

### Inherited by implicit conversion ArrowAssoc from LocalOpt to ArrowAssoc[LocalOpt]

### Ungrouped