[Jikesrvm-researchers] How to get a value out of OPT_RegisterOperand

[Shane B. <br...@cs...>]

I'm looking to retrive a value out of an OPT_RegisterOperand object.  
Here's the corresponding source code....

---------------------------------------------------------------------------------
//Create a Register to hold the tib
OPT_RegisterOperand THE_TIB = ir.regpool.makeTemp(VM_TypeReference.Address);

//Create a Register to hold the type which will be fetched from the tib
OPT_RegisterOperand THE_TYPE = ir.regpool.makeTemp(VM_TypeReference.VM_Type);

// Create instruction to get the tib
OPT_Instruction getTibInstruction = Unary.create(GET_OBJ_TIB, THE_TIB, THIS_POINTER);

// Create instruction to get type from tib
OPT_Instruction getTypeInstruction = Unary.create(GET_TYPE_FROM_TIB, THE_TYPE, THE_TIB);
          
// Create a counter instruction and insert it before the call site
// NOTE: THE_TYPE.toString() currently doesn't give the type of the object
OPT_Instruction counterInst = 
  data.getCounterInstructionForEvent(callSiteTriple.toString() + " " + THE_TYPE.toString());
            
// Now insert the instructions before the call site to obtain the needed data
instr.insertBefore(getTibInstruction);
instr.insertBefore(getTypeInstruction);
instr.insertBefore(counterInst);
---------------------------------------------------------------------------------

Basically I'm writing an optimization phase that attempts to grab the 
runtime type of the reciever object at a 
call site.  The first 2 instructions should get the TIB and the object 
type and store it in the corresponding OPT_RegisterOperand objects.  
However I'm not sure how to get the value (the runtime type) out of the OPT_RegisterOperand 
object and then cast it to a string.  I know I can create an instruction 
that can call my own function which can take the OPT_RegisterOperand as a 
parameter, but I've read there can be an overhead with this and I figure 
there must be an easier way to do this.

Anybody have an idea of how to do this?

-- 
Shane A. Brewer
M.Sc. Student of Computing Science
University Of Alberta
Edmonton, Alberta, Canada
Email - br...@cs...
Website - http://www.cs.ualberta.ca/~brewer