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编 写 ARM 和 Thumb 汇 编 语 言
示 例 2-7 ARM 代 码 跳 转 表
AREA Jump, CODE, READONLY ; Name this block of code
CODE32
; Following code is ARM code
num EQU 2 ; Number of entries in jump table
ENTRY
; Mark first instruction to execute
start
; First instruction to call
MOV r0, #0 ; Set up the three parameters
MOV r1, #3
MOV r2, #2
BL arithfunc ; Call the function
stop MOV r0, #0x18 ; angel_SWIreason_ReportException
LDR r1, =0x20026 ; ADP_Stopped_ApplicationExit
SWI 0x123456 ; ARM semihosting SWI
arithfunc
; Label the function
CMP r0, #num ; Treat function code as unsigned integer
MOVHS pc, lr ; If code is >= num then simply return
ADR r3, JumpTable ; Load address of jump table
LDR pc, [r3,r0,LSL#2] ; Jump to the appropriate routine
JumpTable
DCD DoAdd
DCD DoSub
DoAdd ADD r0, r1, r2 ; Operation 0
MOV pc, lr ; Return
DoSub SUB r0, r1, r2 ; Operation 1
MOV pc, lr ; Return
END
; Mark the end of this file
ARM DUI 0204BSC © 2002、 2003 ARM Limited 版 权 所 有 。 保 留 所 有 权 利 。 2-35