Goal

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Improve start-up time by storing pre-generated LambdaForm handlers in an application-specific CDS archive.

Background

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In JDK-8086045 Improve the java.lang.invoke first initialization costs, the JDK can reduce the number of dynamically generated LambdaForm  classes. Here's an example:

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Code Block
private static final String DIRECT_HOLDER = "java/lang/invoke/DirectMethodHandle$Holder"; ... byte[] bytes = JLIA.generateDirectMethodHandleHolderClassBytes( DIRECT_HOLDER, directMethodTypes, dmhTypes);

The input of generateDirectMethodHandleHolderClassBytes comes from the default_jli_trace.txt file that is generated in GenerateLinkOptData.gmk:

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$(FIXPATH) $(INTERIM_IMAGE_DIR)/bin/java -XX:DumpLoadedClassList=$@.raw.2 \ -XX:SharedClassListFile=$@.interim -XX:SharedArchiveFile=$@.jsa \ -Djava.lang.invoke.MethodHandle.TRACE_RESOLVE=true \ -Duser.language=en -Duser.country=US \ --module-path $(SUPPORT_OUTPUTDIR)/classlist.jar \ -cp $(SUPPORT_OUTPUTDIR)/classlist.jar \ build.tools.classlist.HelloClasslist \ 2> $(LINK_OPT_DIR)/stderr > $(JLI_TRACE_FILE)

Here's how roughly the contents of default_jli_trace.txt correspond to the generated methods in DirectMethodHandle$Holder

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$ grep invokeSpecialIFC ./support/link_opt/default_jli_trace.txt [LF_RESOLVE] java.lang.invoke.DirectMethodHandle$Holder invokeSpecialIFC L3I_I (fail) [LF_RESOLVE] java.lang.invoke.DirectMethodHandle$Holder invokeSpecialIFC LLI_I (fail) $ images/jdk/bin/javap 'java.lang.invoke.DirectMethodHandle$Holder' | grep invokeSpecialIFC static int invokeSpecialIFC(java.lang.Object, java.lang.Object, java.lang.Object, int); static int invokeSpecialIFC(java.lang.Object, java.lang.Object, int);

The methods in DirectMethodHandle$Holder are used in InvokerBytecodeGenerator.java when compiling for LambdaForms:

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private static MemberName lookupPregenerated(LambdaForm form, MethodType invokerType) { if (form.customized != null) { // No pre-generated version for customized LF return null; } String name = form.kind.methodName; switch (form.kind) { [......] case DIRECT_INVOKE_INTERFACE: // fall-through case DIRECT_INVOKE_SPECIAL: // fall-through case DIRECT_INVOKE_SPECIAL_IFC: // fall-through case DIRECT_INVOKE_STATIC: // fall-through case DIRECT_INVOKE_STATIC_INIT: // fall-through case DIRECT_INVOKE_VIRTUAL: return resolveFrom(name, invokerType, DirectMethodHandle.Holder.class); } return null;