Class ChainedCallSite

java.lang.Object
java.lang.invoke.CallSite
java.lang.invoke.MutableCallSite
jdk.dynalink.support.AbstractRelinkableCallSite
jdk.dynalink.support.ChainedCallSite
All Implemented Interfaces:
RelinkableCallSite
public class ChainedCallSite extends AbstractRelinkableCallSite
A relinkable call site that implements a polymorphic inline caching strategy. It remembers up to 8 GuardedInvocations it was linked with, and on each relink request builds a cascading chain of method handles of one invocation falling back to the next one. The number of remembered invocations can be customized by overriding getMaxChainLength() in a subclass. When this call site is relinked with a new invocation and the length of the chain is already at the maximum, it will throw away the oldest invocation. Invocations with invalidated switch points and ones for which their invalidating exception triggered are removed eagerly from the chain. The invocations are never reordered; the most recently linked method handle is always at the start of the chain and the least recently linked at its end. The call site can be safely relinked on more than one thread concurrently. Race conditions in linking are resolved by throwing away the GuardedInvocation produced on the losing thread without incorporating it into the chain, so it can lead to repeated linking for the same arguments.
Since:
9

  • Constructor Summary

    Constructors
    Constructor
    Description
    ChainedCallSite(CallSiteDescriptor descriptor)
    Creates a new chained call site.

  • Method Summary

    Modifier and Type
    Method
    Description
    protected int
    getMaxChainLength()
    The maximum number of method handles in the chain.
    void
    relink(GuardedInvocation guardedInvocation, MethodHandle relinkAndInvoke)
    This method will be called by the dynamic linker every time the call site is relinked (but see RelinkableCallSite.resetAndRelink(GuardedInvocation, MethodHandle) for an exception).
    void
    resetAndRelink(GuardedInvocation guardedInvocation, MethodHandle relinkAndInvoke)
    This method will be called by the dynamic linker every time the call site is relinked and the linker wishes the call site to throw away any prior linkage state (that is how it differs from RelinkableCallSite.relink(GuardedInvocation, MethodHandle)).

    Methods declared in class AbstractRelinkableCallSite

    getDescriptor, initialize
    Modifier and Type
    Method
    Description
    CallSiteDescriptor
    getDescriptor()
    Returns the descriptor for this call site.
    void
    initialize(MethodHandle relinkAndInvoke)
    Invoked by dynamic linker to initialize the relinkable call site by setting a relink-and-invoke method handle.

    Methods declared in class MutableCallSite

    dynamicInvoker, getTarget, setTarget, syncAll
    Modifier and Type
    Method
    Description
    final MethodHandle
    dynamicInvoker()
    Produces a method handle equivalent to an invokedynamic instruction which has been linked to this call site.
    final MethodHandle
    getTarget()
    Returns the target method of the call site, which behaves like a normal field of the MutableCallSite.
    void
    setTarget(MethodHandle newTarget)
    Updates the target method of this call site, as a normal variable.
    static void
    syncAll(MutableCallSite[] sites)
    Performs a synchronization operation on each call site in the given array, forcing all other threads to throw away any cached values previously loaded from the target of any of the call sites.

    Methods declared in class CallSite

    type
    Modifier and Type
    Method
    Description
    MethodType
    type()
    Returns the type of this call site's target.

    Methods declared in class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    Modifier and Type
    Method
    Description
    protected Object
    clone()
    Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
    boolean
    equals(Object o)
    Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
    protected void
    finalize()
    Deprecated, for removal: This API element is subject to removal in a future version.
    May cause performance issues, deadlocks and hangs.
    final Class<? extends Object>
    getClass()
    Answers the unique instance of java.lang.Class which represents the class of the receiver.
    int
    hashCode()
    Answers an integer hash code for the receiver.
    final void
    notify()
    Causes one thread which is waiting on the receiver to be made ready to run.
    final void
    notifyAll()
    Causes all threads which are waiting on the receiver to be made ready to run.
    String
    toString()
    Answers a string containing a concise, human-readable description of the receiver.
    final void
    wait()
    Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
    final void
    wait(long time)
    Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
    final void
    wait(long time, int frac)
    Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

  • Constructor Details

    • ChainedCallSite

      public ChainedCallSite(CallSiteDescriptor descriptor)
      Creates a new chained call site.
      Parameters:
      descriptor - the descriptor for the call site.

  • Method Details

    • getMaxChainLength

      protected int getMaxChainLength()
      The maximum number of method handles in the chain. Defaults to 8. You can override it in a subclass if you need to change the value.
      Returns:
      the maximum number of method handles in the chain. The return value is checked, and if your override returns a value less than 1, a RuntimeException will be thrown.

    • relink

      public void relink(GuardedInvocation guardedInvocation, MethodHandle relinkAndInvoke)
      Description copied from interface: RelinkableCallSite
      This method will be called by the dynamic linker every time the call site is relinked (but see RelinkableCallSite.resetAndRelink(GuardedInvocation, MethodHandle) for an exception). It will be passed a GuardedInvocation that the call site should incorporate into its target method handle. When this method is called, the call site is allowed to keep other non-invalidated invocations around for implementation of polymorphic inline caches and compose them with this invocation to form its final target.
      Parameters:
      guardedInvocation - the guarded invocation that the call site should incorporate into its target method handle.
      relinkAndInvoke - a relink-and-invoke method handle. This is a method handle matching the method type of the call site that is supplied by the DynamicLinker as a callback. It should be used by this call site as the ultimate fallback when it can't invoke its target with the passed arguments. The fallback method is such that when it's invoked, it'll try to obtain an adequate target GuardedInvocation for the invocation, and subsequently invoke RelinkableCallSite.relink(GuardedInvocation, MethodHandle) or RelinkableCallSite.resetAndRelink(GuardedInvocation, MethodHandle), and finally invoke the target.

    • resetAndRelink

      public void resetAndRelink(GuardedInvocation guardedInvocation, MethodHandle relinkAndInvoke)
      Description copied from interface: RelinkableCallSite
      This method will be called by the dynamic linker every time the call site is relinked and the linker wishes the call site to throw away any prior linkage state (that is how it differs from RelinkableCallSite.relink(GuardedInvocation, MethodHandle)). It will be passed a GuardedInvocation that the call site should use to build its new target method handle. When this method is called, the call site is discouraged from keeping any previous state, and is supposed to only link the current invocation.
      Parameters:
      guardedInvocation - the guarded invocation that the call site should use to build its target method handle.
      relinkAndInvoke - a relink-and-invoke method handle. This is a method handle matching the method type of the call site that is supplied by the DynamicLinker as a callback. It should be used by this call site as the ultimate fallback when it can't invoke its target with the passed arguments. The fallback method is such that when it's invoked, it'll try to obtain an adequate target GuardedInvocation for the invocation, and subsequently invoke RelinkableCallSite.relink(GuardedInvocation, MethodHandle) or RelinkableCallSite.resetAndRelink(GuardedInvocation, MethodHandle), and finally invoke the target.