Hi all - with Andy's cool trick I'm down to 10 cycles typical with return
in Z. Any other ideas? - Rich

; given address of 32 bit little-endian counter in W,
; decrement the counter and return Z set if zero
; 99.2% of the time, this takes 10 cycles w/call
dec32           movwf FSR       ; FSR -> v
                decfsz INDF,f   ; v[0]--
                goto dec32nz

                ; here, v[0] just became 0, check the others
                incf FSR,f      ; get v[1]
                movf INDF,w
                incf FSR,f      ; OR v[2]
                iorwf INDF,w
                incf FSR,f      ; OR v[3]
                iorwf INDF,w
                return          ; return Z set if so

                ; here, v[0] is non-zero, make sure we return with Z=0
dec32nz         clrz            ; in case Z was set on entry...
                incfsz INDF,w   ; now, did v[0] underflow?
                return          ; no (this is 99.2% path)
                incf FSR,f      ; yes, advance to v[1]
                decfsz INDF,f   ; dec v[1]
                incfsz INDF,w   ; underflow?
                return          ;
                incf FSR,f      ; yes, advance to v[2]
                decfsz INDF,f   ; dec v[2]
                incfsz INDF,w   ; underflow?
                return          ;
                incf FSR,f      ; yes, advance to v[3]
                decfsz INDF,f   ; dec v[3]
                return          ; return
                return          ; in either case