LOOPNZ and LOOPNE Instructions

The LOOPNZ (loop if not zero) and LOOPNE (loop if not equal) instructions are the counterpart of LOOPZ or LOOPE. The loop destination must be within –128 to +127 bytes of the current location counter.

LOOPNZ/LOOPNE — LOOP If Not Equal (Zero)
Usage: LOOPNZ label or LOOPNE label

Flag O D I S Z A P C
Result                

Decrements ECX by 1 (without modifying the flags) and transfers control to “label” if ECX != 0 and the Zero Flag is clear.
Clocks
Operands 286 386 486 Size Bytes
label: jump 8+m 11+m 9 2
no jump 4 ? 6 2

The loop continues while the unsigned value of ECX is greater than zero and zero flag is clear. The following code is the execution logic of them: 

 
  ECX = ECX - 1

 
  if (ECX > 0 and ZF = 0)

 
    jump to destination
The code on the right shows an array whose integer elements are sorted ascendingly. It scans each number in an array until a nonnegative number is found. It then applies addition to the remaining nonnegative numbers.
 Adding up the Nonnegative Integers  

 
 INCLUDE Irvine32.inc

 
 .data

 
 array     SWORD  -10, -6, -3, -1,

 
                    4, 10, 30, 40

 
 .code

 
 main PROC

 
       mov    esi, OFFSET array

 
       mov    ecx, LENGTHOF array

 
       ; Skip negative values.

 
 next: test   WORD PTR [esi], 8000h

 
       pushfd

 
       add    esi, TYPE array

 
       popfd

 
       loopnz next

 
       jnz    quit
       

 
       ; Add up the rest values.

 
       sub    esi, TYPE array

 
       mov    eax, 0

    

     

 
         
     
     

 

    
    
     

     
    

   

 
 calc: add    ax, [esi]

 
       add    esi, TYPE array

 
       loop   calc

 
       call   WriteInt

 
 quit: exit

 
 main ENDP

 
 END main


      “I’m not arguing, I’m just explaining why I’m right.”    
      ― Unknown