java.lang.Object
java.lang.invoke.CallSite
java.lang.invoke.MutableCallSite
jdk.dynalink.support.AbstractRelinkableCallSite
jdk.dynalink.support.ChainedCallSite
- All Implemented Interfaces:
RelinkableCallSite
A relinkable call site that implements a polymorphic inline caching strategy.
It remembers up to 8
GuardedInvocation
s 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.-
Constructor Summary
ConstructorDescriptionChainedCallSite
(CallSiteDescriptor descriptor) Creates a new chained call site. -
Method Summary
Modifier and TypeMethodDescriptionprotected int
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 seeRelinkableCallSite.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 fromRelinkableCallSite.relink(GuardedInvocation, MethodHandle)
).Methods declared in class jdk.dynalink.support.AbstractRelinkableCallSite
getDescriptor, initialize
Methods declared in class java.lang.invoke.MutableCallSite
dynamicInvoker, getTarget, setTarget, syncAll
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Constructor Details
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ChainedCallSite
Creates a new chained call site.- Parameters:
descriptor
- the descriptor for the call site.
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Method Details
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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.
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relink
Description copied from interface:RelinkableCallSite
This method will be called by the dynamic linker every time the call site is relinked (but seeRelinkableCallSite.resetAndRelink(GuardedInvocation, MethodHandle)
for an exception). It will be passed aGuardedInvocation
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 theDynamicLinker
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 targetGuardedInvocation
for the invocation, and subsequently invokeRelinkableCallSite.relink(GuardedInvocation, MethodHandle)
orRelinkableCallSite.resetAndRelink(GuardedInvocation, MethodHandle)
, and finally invoke the target.
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resetAndRelink
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 fromRelinkableCallSite.relink(GuardedInvocation, MethodHandle)
). It will be passed aGuardedInvocation
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 theDynamicLinker
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 targetGuardedInvocation
for the invocation, and subsequently invokeRelinkableCallSite.relink(GuardedInvocation, MethodHandle)
orRelinkableCallSite.resetAndRelink(GuardedInvocation, MethodHandle)
, and finally invoke the target.
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