Support pre-generated MethodHandle LambdaForms in CDS (JDK-8247536)

Goal:

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

Background:

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:

# 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

Here's the difference between the exploded build and the final image:

$ jdk/bin/javap 'java.lang.invoke.DirectMethodHandle$Holder'
Compiled from "DirectMethodHandle.java"
final class java.lang.invoke.DirectMethodHandle$Holder {
  final java.lang.invoke.DirectMethodHandle this$0;
  java.lang.invoke.DirectMethodHandle$Holder(java.lang.invoke.DirectMethodHandle);
}


$ images/jdk/bin/javap 'java.lang.invoke.DirectMethodHandle$Holder'
Compiled from "DirectMethodHandle$Holder"
final class java.lang.invoke.DirectMethodHandle$Holder {
  static int invokeInterface(java.lang.Object, java.lang.Object, java.lang.Object);
  static java.lang.Object invokeSpecial(java.lang.Object, java.lang.Object, java.lang.Object, int);
  static java.lang.Object invokeSpecial(java.lang.Object, java.lang.Object, java.lang.Object, long);
  [~150 more lines ...]
}

The JDK image's version of the java.lang.invoke.DirectMethodHandle$Holder class is generated here in GenerateJLIClassesPlugin.java. This plugin is executed when we generate the file images/jdk/lib/modules.

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

Child pages

Support pre-generated MethodHandle LambdaForms in CDS (JDK-8247536)