armcode2.s

s3c44b0 arm指令实验2

#*********************************************************************************************
# NAME:		ARMcode2.s																		 *
# Author: 	Embest																			 *
# Desc:		ARM instruction examples														 *
#           Example for Condition Code														 *
# History:	shw.He 2005.02.22																 *
#*********************************************************************************************

/*------------------------------------------------------------------------------------------*/
/*	 								constant define						 				    */
/*------------------------------------------------------------------------------------------*/
.global _start

/*------------------------------------------------------------------------------------------*/
/*	 								code								 				    */
/*------------------------------------------------------------------------------------------*/
.text
.equ	num,	2							/*  Number of entries in jump table */

_start:
		mov		r0, #0						/*  set up the three parameters */
		mov		r1, #3
		mov		r2, #2
		bl		arithfunc					/*  call the function */

stop:
		b		stop


# ********************************************************************************************
# * According R0 valude to execute the code													 *
# ********************************************************************************************
arithfunc:									/*  label the function */
		cmp		r0, #num					/*  Treat function code as unsigned integer */
		bhs		DoAdd						/*  If code is >=2 then do operation 0. */

		adr		r3, JumpTable				/*  Load address of jump table */
		ldr		pc, [r3,r0,LSL#2]			/*  Jump to the appropriate routine */

JumpTable:
		.long		DoAdd
		.long		DoSub

DoAdd:
		add		r0, r1, r2					/*  Operation 0, >1 */
		mov		pc, lr 						/*  Return */

DoSub:
		sub		r0, r1, r2					/*  Operation 1 */
		mov     pc,lr						/*  Return */

.end										/*  mark the end of this file */