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AREA ArithGate, CODE ; name this block of code
ENTRY ; mark the first instruction to call
main
MOV r0, #2 ; set up three parameters
MOV r1, #5
MOV r2, #15
BL arithfunc ; call the function
SWI 0x11 ; terminate
arithfunc ; label the function
CMP r0, #4 ; Treat code as unsigned integer
BHI ReturnA1 ; If code > 4 then return first
; argument
ADR r3, JumpTable ; Load address of the jump table
LDR pc,[r3,r0,LSL #2] ; Jump to appropriate routine
JumpTable
DCD ReturnA1
DCD ReturnA2
DCD DoAdd
DCD DoSub
DCD DoRsb
ReturnA1
MOV r0, r1 ; Operation 0, >4
MOV pc,lr
ReturnA2
MOV r0, r2 ; Operation 1
MOV pc,lr
DoAdd
ADD r0, r1, r2 ; Operation 2
MOV pc,lr
DoSub
SUB r0, r1, r2 ; Operation 3
MOV pc,lr
DoRsb
RSB r0, r1, r2 ; Operation 4
MOV pc,lr
END ; mark the end of this file
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