[Condy] Add support for ConstantDynamic constant pool entries

[tajila]

http://cr.openjdk.java.net/~dlsmith/constant-dynamic.html

The following have to be done in order

• 1. Classfile parsing ConstantDynamic: Classfile parsing #1270
• 2. Building ROM and RAM Classes ConstantDynamic: Building ROM and RAM Classes #1271
• 3. Resolving Constant_Dynamic entries ConstantDynamic: Resolving Constant_Dynamic entries #1272
• 4. Add support for optThruput policy ConstantDynamic: Add support for balanced GC policy #1273

The rest can be done simultaneously

• Add tests for ConstantDynamic ConstantDynamic: Add tests for ConstantDynamic #1274
• Add cycle detection for Constant dynamic args ConstantDynamic: Add cycle detection for Constant dynamic args #1275
• Adding sun_relfect_ConstantPool native ConstantDynamic: Adding sun_relfect_ConstantPool native #1276
• Adding jithelper to resolve Constant dynamic entries ConstantDynamic: Adding jithelper to resolve Constant dynamic entries #1277
• Verifier checks for Constant dynamic ConstantDynamic: Verifier checks for Constant dynamic #1278
• Add support for Gencon ConstantDynamic: Add support for Gencon (including optthruput + avgpause) #1279
• Add support for metronome ConstantDynamic: Add support for Metronome #1280
  Background

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New contant pool type ‘Constant_Dynamic’ used to describe a dynamically computed constant which can be a primitive of ref. This value is produced by calling a bootstrap method. The constant is only computed once. In multithreaded scenarios, as soon as a value is computed all other subsequent ones are discarded (there is only one winner). Similarly, for recursive scenarios the deepest nested call wins.

CONSTANT_Dynamic_info {
   u1 tag;
   u2 bootstrap_method_attr_index;
   u2 name_and_type_index;
}

The ‘tag’ is the type of ConstantPool entry (17). ‘bootstrap_method_attr_index’ is the index of the bootstrap method in the bootstrap method table in the class file. ‘name_and_type_index’ index into the constant pool that must be a ‘Constant_NameAndType_info’ structure.

Resolution for ConstantDynamic is:
• Bootsrap MethodHandle is resolved (specified by symbolic reference). Exception may be thrown if failure occurs when resolving methodHandle
• Array is created of size n + 3 where n are the static args (n >= 0). Array initialized to null.
o This stage can be optimized out so long as there are no behavior changes
• First arg of array is the lookup object
• Second arg is the Name (j.l.String) in name_and_type_index
• Third arg is a Class derived from the field descriptor in name_and_type_index
• The rest of the args are the static args listed at bootstrap_method_attr_index. Exception may be thrown
• If the symbolic reference being resolved is also a static arg or references itself via other static args then a StackOverflowError is thrown
• The bootstrapMethodHandle is invoked (mh.invokeWithArguments(argsArray)). Exception/Error may be thrown
• The result from the boostrapMethodHandle is validated. For condy this converts the result to the type specified by the field descriptor in name_and_type_index

Once resolution is performed the value is cached in the constant pool. If an error/exception occurs the same failure must be thrown every time the constant pool entry is referenced. A Constant_Dynamic entry may be loaded by ldc instruction.

J9 Implementation

Goal is to reuse as much of the invokeDynamic functionality as possible. As a result some of the invokeDynmaic functionality and layout will have to be changed

[tajila]

This is complete