Labels resolving to zero

[Brian Mokrzycki <brian-mokrzycki@uiowa.edu>]

I'm currently trying to port binutils to a custom digital signal  
processing architecture.  I've run into a couple issues but I can't  
seem to figure this one out.  I am trying to implement a branching  
instruction such as in the example below.

_START:
		LD		R4, 8
		NOP
LOOP: 	ADD 	R1,R2,R3
		SUB 	R4,R4,1
		BNEZ	LOOP

The LOOP label argument for BNEZ is a 24-bit absolute address (well  
actually 26-bit but I wanted to make sure byte boundaries weren't  
causing more hidden problems).  When I assemble this, the LOOP label  
always resolves to 0 <_start>.  Furthermore when I go and actually  
link the object file, the disassembly of BNEZ becomes this very very  
long sequence of bytes and is an *unknown* instruction.

Here's what I think are the relevant lines in my .cpu file to describe  
the branch instruction.  Please note that I haven't implemented the  
flags yet so the PC is updated unconditionally for now.

; Field Definition

(df f-abs24     "Absolute 24-bit Jump Address"  ((ISA wvfe-cop) ABS- 
ADDR)   44 24 INT
         ((value pc) (sra WI pc    (const 2)))
         ((value pc) (sll WI value (const 2))))

....


; Enumeration of branch codes and tests

; Branch Codes :  bits 50-47
(define-normal-insn-enum insn-cnd-code "Control Unit Condition Code  
Enums" () CND_ f-50-4
   ("UNC" "POS" "NEG" "ZER" "OVF" "BLI" "BCE" "7" "8" "9" "10" "11"  
"12" "13" "14" "15")
)

(define-normal-insn-enum insn-cnd-test "Control Unit Condition Test  
Enums" () TST_ f-51-1
   ("EQ" "NE")
)
....

(dnop uimm24    "Absolute 24-bit Address"       ()      h-iaddr f-abs24)

....

(dni bneza "branch if not equal zero (absolute address)"
         ()
         "bnez ${uimm24}"
         (+ COP_BRCH (f-58-6 0) (f-52-1 0) TST_NE CND_ZER (f-46-2 0)  
uimm24 (f-20-21 0))
         (set pc uimm24)
         ()
)

 From looking at other ports I'm fairly confident that this is what's  
required in the .opc file.  So this makes me believe that there is  
another file that I need to modify/implement to get the address of the  
label.  Any ideas?

-Brian