Re: [Sablevm-developer] reflection classes for constant pool and bytecode data

[Etienne M. G. <eg...@j-...>]

Hi Andrew.

I have to give this a careful look.  I'll get back tomorrow about it.  

Anybody else has comments?  (I think we should CC John Leuner, which I
am doing now).  Maybe he'll be interested to being added as a developer,
too? (This last question is directed to John;-)
  
Etienne

Andrew Purtell wrote:
> 
> Hi, SableVM developers!
> 
> I've been looking over the SableVM sources and I think the first step
> toward creating a JIT should be the addition of a simple class hierarchy
> containing native methods for exposing SableVM's internal representations
> of the constant pool and (prepared) bytecodes to the Java environment.
> I've been working this week with some classes I've cobbled together for
> parsing class files directly from disk, but keeping the class data in
> memory solely for a JIT's use is wasteful.
> 
> How does this look?
> 
>   public abstract class org.sablevm.vm.Constant
>   {
>       public int size() { return 1; }
>   };
> 
>   public class org.sablevm.vm.Constant_UTF8
>       extends org.sablevm.vm.Constant
>   {
>       public String value;
>   };
> 
>   public class org.sablevm.vm.Constant_Unicode
>       extends org.sablevm.vm.Constant
>   {
>       public char[] value;
>   };
> 
>   public class org.sablevm.vm.Constant_Integer
>       extends org.sablevm.vm.Constant
>   {
>       public int value;
>   };
> 
>   public class org.sablevm.vm.Constant_Float
>       extends org.sablevm.vm.Constant
>   {
>       public float value;
>   };
> 
>   public class org.sablevm.vm.Constant_Long
>       extends org.sablevm.vm.Constant
>   {
>       public long value;
>       public int size() { return 2; }
>   };
> 
>   public class org.sablevm.vm.Constant_Double
>       extends org.sablevm.vm.Constant
>   {
>       public double value;
>       public int size() { return 2; }
>   };
> 
>   public class org.sablevm.vm.Constant_String
>       extends org.sablevm.vm.Constant
>   {
>       public String value;
>   };
> 
>   public class org.sablevm.vm.Constant_Class
>       extends org.sablevm.vm.Constant
>   {
>       public int class_index;
>   };
> 
>   public class org.sablevm.vm.Constant_Fieldref
>       extends org.sablevm.vm.Constant
>   {
>       public int class_index;
>       public int name_and_type_index;
>   };
> 
>   public class org.sablevm.vm.Constant_Methodref
>       extends org.sablevm.vm.Constant
>   {
>       public int class_index;
>       public int name_and_type_index;
>   };
> 
>   public class org.sablevm.vm.Constant_InterfaceMethodref
>       extends org.sablevm.vm.Constant
>   {
>       public int class_index;
>       public int name_and_type_index;
>   };
> 
>   public class org.sablevm.vm.Constant_NameAndType
>       extends org.sablevm.vm.Constant
>   {
>       public int name_index;
>       public int signature_index;
>   };
> 
>   public class org.sablevm.vm.Opcode  { ... };
> 
>   public class org.sablevm.vm.Code
>   {
>       public org.sablevm.vm.Class clazz;     // class containing this method
>       public int access_flags;
>       public int max_stack;
>       public int max_locals;
>       public int exception_table[][];
>       public org.sablevm.vm.Opcode code[];   // method opcodes
>       ...
>   }
> 
>   public class org.sablevm.vm.Field
>   {
>       public int access_flags;
>       public String name;
>       public String signature;
>       ...
>   }
> 
>   public class org.sablevm.vm.Class
>   {
>       public org.sablevm.vm.Class superclass;     // superclass, if any
>       public int access_flags;
>       public org.sablevm.vm.Field fields[];       // class fields
>       public org.sablevm.vm.Field methods[];      // class/interface methods
> 
>       // constructs a Class object from the internal representation of
>       // class or interface 'name'
>       public native org.sablevm.vm.Class (String name);
> 
>       // retrieve a Constant object for the constant located at index 'i'
>       // for Class 'name'
>       public static native org.sablevm.vm.Constant getConstant (String name,
>                                                                 int i);
> 
>       // returns a Code object encapsulating the given method's bytecodes,
>       // exception table, max stack size, and max locals
>       public static native org.sablevm.vm.Code getCode (String class,
>                                                         String name,
>                                                         String signature);
> 
>       // object method version of getConstant()
>       public native org.sablevm.vm.Constant getConstant (int i);
> 
>       // object method version of getCode()
>       public native org.sablevm.vm.Code getCode (String name,
>                                                  String signature);
>   }
> 
> I've only jotted down read-only methods so far. Eventually there will need
> to be an org.sablevm.vm.Class method for attaching prepared native code to
> a given method.
> 
> Note that these are NOT clases I plan to keep JIT state in during
> translation. There's an "org.sablevm.vm.jit.*" hierarchy I'm thinking over
> at the moment.
> 
> I was thinking the native methods implementing these classes could be added
> to libsablevm. The associated classes will need to be added to sablepath.
> Seeing how both are pulled in only if they are part of the transitive
> closure of referenced classes/functions/etc., they cost nothing if the "use
> JIT" configure option is not enabled.
> 
> Andrew Purtell
> from home -- apu...@ac...
> 
> _______________________________________________
> Sablevm-developer mailing list
> Sab...@li...
> http://lists.sourceforge.net/mailman/listinfo/sablevm-developer

-- 
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Etienne M. Gagnon, M.Sc.                     e-mail: eg...@j-...
Author of SableVM:                             http://www.sablevm.org/
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