class TailCallElimination extends Global.Transformer
A Tail Call Transformer
- Source
- TailCalls.scala
- Version
1.1 What it does: Finds method calls in tail-position and replaces them with jumps. A call is in a tail-position if it is the last instruction to be executed in the body of a method. This is done by recursing over the trees that may contain calls in tail-position (trees that can't contain such calls are not transformed). However, they are not that many. Self-recursive calls in tail-position are replaced by jumps to a label at the beginning of the method. As the JVM provides no way to jump from a method to another one, non-recursive calls in tail-position are not optimized. A method call is self-recursive if it calls the current method and the method is final (otherwise, it could be a call to an overridden method in a subclass). Furthermore, If the method has type parameters, the call must contain these parameters as type arguments. Recursive calls on a different instance are optimized. Since 'this' is not a local variable, a dummy local val is added and used as a label parameter. The backend knows to load the corresponding argument in the 'this' (local at index 0). This dummy local is never used and should be cleaned up by dead code elimination (when enabled). This phase has been moved before pattern matching to catch more of the common cases of tail recursive functions. This means that more cases should be taken into account (like nested function, and pattern cases). If a method contains self-recursive calls, a label is added to at the beginning of its body and the calls are replaced by jumps to that label. Assumes:
Uncurry
has been run already, and no multiple parameter lists exit.
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- By Inheritance
- TailCallElimination
- Transformer
- Transformer
- AnyRef
- Any
- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
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- Public
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Instance Constructors
- new TailCallElimination(unit: Global.CompilationUnit)
Type Members
- class ClonedTailContext extends TailContext
- class DefDefTailContext extends TailContext
- sealed trait TailContext extends AnyRef
Value Members
-
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
-
final
def
##(): Int
Equivalent to
x.hashCode
except for boxed numeric types andnull
.Equivalent to
x.hashCode
except for boxed numeric types andnull
. 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. Fornull
returns a hashcode wherenull.hashCode
throws aNullPointerException
.- returns
a hash value consistent with ==
- Definition Classes
- AnyRef → Any
-
def
+(other: String): String
- Implicit
- This member is added by an implicit conversion from TailCallElimination to any2stringadd[TailCallElimination] performed by method any2stringadd in scala.Predef.
- Definition Classes
- any2stringadd
-
def
->[B](y: B): (TailCallElimination, B)
- Implicit
- This member is added by an implicit conversion from TailCallElimination to ArrowAssoc[TailCallElimination] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @inline()
-
final
def
==(arg0: Any): Boolean
The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- AnyRef → Any
-
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 aClassCastException
at runtime, while the expressionList(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 typeT0
.
-
def
atOwner[A](owner: Global.Symbol)(trans: ⇒ A): A
- Definition Classes
- Transformer
-
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
-
def
currentClass: Global.Symbol
- Attributes
- protected
- Definition Classes
- Transformer
-
def
currentMethod: Global.Symbol
- Attributes
- protected
- Definition Classes
- Transformer
-
var
currentOwner: Global.Symbol
- Attributes
- protected[scala]
- Definition Classes
- Transformer
-
def
ensuring(cond: (TailCallElimination) ⇒ Boolean, msg: ⇒ Any): TailCallElimination
- Implicit
- This member is added by an implicit conversion from TailCallElimination to Ensuring[TailCallElimination] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: (TailCallElimination) ⇒ Boolean): TailCallElimination
- Implicit
- This member is added by an implicit conversion from TailCallElimination to Ensuring[TailCallElimination] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: Boolean, msg: ⇒ Any): TailCallElimination
- Implicit
- This member is added by an implicit conversion from TailCallElimination to Ensuring[TailCallElimination] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
def
ensuring(cond: Boolean): TailCallElimination
- Implicit
- This member is added by an implicit conversion from TailCallElimination to Ensuring[TailCallElimination] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
-
final
def
eq(arg0: AnyRef): Boolean
Tests whether the argument (
that
) is a reference to the receiver object (this
).Tests whether the argument (
that
) is a reference to the receiver object (this
).The
eq
method implements an equivalence relation on non-null instances ofAnyRef
, and has three additional properties:- It is consistent: for any non-null instances
x
andy
of typeAnyRef
, multiple invocations ofx.eq(y)
consistently returnstrue
or consistently returnsfalse
. - For any non-null instance
x
of typeAnyRef
,x.eq(null)
andnull.eq(x)
returnsfalse
. null.eq(null)
returnstrue
.
When overriding the
equals
orhashCode
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
- It is consistent: for any non-null instances
-
def
equals(arg0: Any): Boolean
The equality method for reference types.
-
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 betweenfinalize
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
-
def
formatted(fmtstr: String): String
- Implicit
- This member is added by an implicit conversion from TailCallElimination to StringFormat[TailCallElimination] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @inline()
-
final
def
getClass(): Class[_]
Returns the runtime class representation of the object.
Returns the runtime class representation of the object.
- returns
a class object corresponding to the runtime type of the receiver.
- Definition Classes
- AnyRef → Any
-
def
hashCode(): Int
The hashCode method for reference types.
-
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 returnfalse
, while the expressionList(1).isInstanceOf[List[String]]
will returntrue
. 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 typeT0
;false
otherwise.
- Definition Classes
- Any
-
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
- def noTailTransform(tree: Global.Tree): Global.Tree
- def noTailTransforms(trees: List[Global.Tree]): collection.immutable.List[Global.Tree]
-
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
-
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
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
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
-
def
transform(tree: Global.Tree): Global.Tree
- Definition Classes
- TailCallElimination → Transformer
-
def
transform(tree: Global.Tree, nctx: TailContext): Global.Tree
Rewrite this tree to contain no tail recursive calls
-
def
transformCaseDefs(trees: List[Global.CaseDef]): List[Global.CaseDef]
- Definition Classes
- Transformer
-
def
transformIdents(trees: List[Global.Ident]): List[Global.Ident]
- Definition Classes
- Transformer
-
def
transformMemberDefs(trees: List[Global.MemberDef]): List[Global.MemberDef]
- Definition Classes
- Transformer
-
def
transformModifiers(mods: Global.Modifiers): Global.Modifiers
- Definition Classes
- Transformer
-
def
transformStats(stats: List[Global.Tree], exprOwner: Global.Symbol): List[Global.Tree]
- Definition Classes
- Transformer
-
def
transformTemplate(tree: Global.Template): Global.Template
- Definition Classes
- Transformer
-
def
transformTrees(trees: List[Global.Tree]): List[Global.Tree]
- Definition Classes
- Transformer
-
def
transformTypeDefs(trees: List[Global.TypeDef]): List[Global.TypeDef]
- Definition Classes
- Transformer
-
def
transformUnit(unit: Global.CompilationUnit): Unit
- Definition Classes
- TailCallElimination → Transformer
-
def
transformValDef(tree: Global.ValDef): Global.ValDef
- Definition Classes
- Transformer
-
def
transformValDefs(trees: List[Global.ValDef]): List[Global.ValDef]
- Definition Classes
- Transformer
-
def
transformValDefss(treess: List[List[Global.ValDef]]): List[List[Global.ValDef]]
- Definition Classes
- Transformer
-
val
treeCopy: Global.TreeCopier
- Definition Classes
- Transformer
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
- def yesTailTransform(tree: Global.Tree): Global.Tree
-
def
→[B](y: B): (TailCallElimination, B)
- Implicit
- This member is added by an implicit conversion from TailCallElimination to ArrowAssoc[TailCallElimination] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- object EmptyTailContext extends TailContext
The Scala compiler API.
The following resources are useful for Scala plugin/compiler development: