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Safe to use r13-r15 as general register?

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!

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Zova Chou over 12 years ago

Note: This was originally posted on 25th July 2011 at http://forums.arm.com

If you don't need stack operation during a period of time, will this save one more register?

str sp, [pc, #?]
...
//use sp as gp reg
...
ldr sp, [pc, #??] // you should know the offset from where you put sp value
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Zova Chou over 12 years ago

Note: This was originally posted on 25th July 2011 at http://forums.arm.com

If you don't need stack operation during a period of time, will this save one more register?

str sp, [pc, #?]
...
//use sp as gp reg
...
ldr sp, [pc, #??] // you should know the offset from where you put sp value
Cancel
Vote up 0 Vote down

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