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# Do this in your JDK build directory.
# The exploded JDK build:
$ jdk/bin/javac -J-verbose ~/tmp/HelloWorld.java | grep LambdaForm | grep __JVM_LookupDefineClass__ 
[0.142s][info][class,load] java.lang.invoke.LambdaForm$MH/0x0000000800066c40 source: __JVM_LookupDefineClass__
[0.143s][info][class,load] java.lang.invoke.LambdaForm$DMH/0x0000000800066040 source: __JVM_LookupDefineClass__
[0.143s][info][class,load] java.lang.invoke.LambdaForm$MH/0x0000000800066440 source: __JVM_LookupDefineClass__
[snip]

$ jdk/bin/javac -J-verbose ~/tmp/HelloWorld.java | grep LambdaForm | grep __JVM_LookupDefineClass__ | wc
    102     408   11400


# The final JDK image: 
$ images/jdk/bin/javac -J-verbose ~/tmp/HelloWorld.java | grep LambdaForm | grep __JVM_LookupDefineClass__ |  wc
     34     136    3800

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We regenerate the XXX$Holder classes to contain all necessary methods used by the application.

Static Dump

This is being has been implemented in JDK-8247536 (Support for pre-generated java.lang.invoke classes in CDS static archive - integrated into JDK 16).

During the trial run (with -XX:DumpLoadedClassList=classlist), we can save the list of LambdaForm handlers using a special syntax like:

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• http://cr.openjdk.java.net/~minqi/2020/8247536/webrev-01/
• The generation of the customized DirectMethodHandle$Holder is done in MetaspaceShared::regenerate_holder_classes().

Dynamic Dump

• (This will be done in a follow-up RFE JDK-XXXXXXX/TBDSee JDK-8255493 (Support for pre-generated java.lang.invoke classes in CDS dynamic archive)
• Collect a @lambda-form-invoker list (in memory) when -XX:ArchiveClassesAtExit is specified.
• When the dynamic archive is dumped, use this list to create customized Holder classes.
• TBD

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