Assembly Code How can we use multiplication in assembly with

Assembly Code:

How can we use multiplication in assembly without using mul or imul instruction? For example how can we multiply a number by \"2017\" without using mul/imul instructions?

Solution

; INPUT CX,BX
; OUTPUT DX:AX - 32 bits
; CLOBBERS BX,CX,DI

   xor ax,ax ; zero a reg
   mov dx,ax ; 1 clock faster than xor
   mov di,cx
   or di,bx ; test for zero on both regs
   jz @done
   mov di,ax ; DI used for reg,reg adc
@loop:
   shr cx,1 ; divide by two, bottom bit moved to carry flag
   jnc @skipAddToResult
   add ax,bx
   adc dx,di ; reg,reg is faster than reg,imm16
@skipAddToResult:
   add bx,bx ; faster than shift or mul
   or cx,cx ; fast zero check
   jnz @loop
@done:
   ret