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Safe to use r13-r15 as general register?

Yang Fang
Note: This was originally posted on 18th July 2011 at http://forums.arm.com

Hello, I am writting a function, which involves complicated algorithm, I want to have a lot of general purpose registers to keep the routine speed. I have read some article that r13-r15 are special registers, but can be used as general purpose registers.

Can I do it like this
   stmfd       sp!, {r4-r15,lr}
:
:
    ldmfd       sp!, {r4-r15,pc}

Thank you very much!
Parents
  • Note: This was originally posted on 18th July 2011 at http://forums.arm.com


    Hello, I am writting a function, which involves complicated algorithm, I want to have a lot of general purpose registers to keep the routine speed. I have read some article that r13-r15 are special registers, but can be used as general purpose registers.

    Can I do it like this
       stmfd       sp!, {r4-r15,lr}
    :
    :
        ldmfd       sp!, {r4-r15,pc}

    Thank you very much!


    Unfortunately, r13-r15 are special registers and can not be used like that way. Actually, r15 is pc, r14 is lr, and r13 is sp.
Reply
  • Note: This was originally posted on 18th July 2011 at http://forums.arm.com


    Hello, I am writting a function, which involves complicated algorithm, I want to have a lot of general purpose registers to keep the routine speed. I have read some article that r13-r15 are special registers, but can be used as general purpose registers.

    Can I do it like this
       stmfd       sp!, {r4-r15,lr}
    :
    :
        ldmfd       sp!, {r4-r15,pc}

    Thank you very much!


    Unfortunately, r13-r15 are special registers and can not be used like that way. Actually, r15 is pc, r14 is lr, and r13 is sp.
Children
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