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Asked: 2026-06-13T08:05:00+00:00

I have a simple program here which is set to produce the output, The

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I have a simple program here which is set to produce the output,

The value of a is 2005

The value of b is 1959

The value of c is 1

The value of d is 0

The value of (a - b) * (c + d) is 46

I’m looking for the best ways to optimize my code, I’m repeating code ALOT! is it possible to print straight from other registers? e.g SWI 0 but for a integer not in R0?

    B   main
aval    DEFW    2005
bval    DEFW    1959
cval    DEFW    1
dval    DEFW    0
valOf   DEFB    'The value of \0'
isStr   DEFB    ' is \0'
lstStr  DEFB    'The value of (a - b) * (c + d) is \0'

    ALIGN

main    ADR R0, valOf   ;Value a
    SWI 3       
    MOV R0, #97     
    SWI 0       
    ADR R0, isStr   
    SWI 3
    LDR R0, aval    
    SWI 4
    MOV R0, #10     ;print new line
    SWI 0

    ADR R0, valOf   ;Value b
    SWI 3
    MOV R0, #98
    SWI 0
    ADR R0, isStr   
    SWI 3
    LDR R0, bval    
    SWI 4
    MOV R0, #10     ;print new line
    SWI 0

    ADR R0, valOf   ;Value c
    SWI 3
    MOV R0, #99
    SWI 0
    ADR R0, isStr   
    SWI 3
    LDR R0, cval    
    SWI 4
    MOV R0, #10     ;print new line
    SWI 0

    ADR R0, valOf   ;print 'value of '
    SWI 3
    MOV R0, #100
    SWI 0
    ADR R0, isStr   ;
    SWI 3
    LDR R0, dval    
    SWI 4   
    MOV R0, #10     ;print new line
    SWI 0

    ADR     R0, lstStr
    SWI 3
    LDR R3, aval
    LDR R4, bval
    LDR R5, cval
    LDR R6, dval
    SUB R1, R3, R4
    SUB R2, R5, R6
    MUL R0, R1, R2
    SWI 4

    SWI 2       ;exit

Any thoughts much appreciated 🙂

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1 Answer

  1. Editorial Team

    I was about to ask if you have to write in assembly but since you are using SWI (nowadays it is called SVC) obviously you are sitting on top of an OS, high chance Linux.

    Why you are not writing in C? That should be much easier for you except if this is solely for learning purposes which in that case why you would try to learn such a usage?

    About optimization, when your are sitting on top of a non-real-time OS and make system calls any performance expectation will be just lost. From the point of software interrupt kernel can delay your code variably and un-guaranteed fashion.

    So in this case if you are thinking about making your application fast, try to reduce number of system calls by preparing / caching print buffers in userspace where you can apply some plain and easy C idioms.

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