Closer look at the registers on an ARM cpu

In my dabbling with ARM assembly so far (my most recent achievement was completing my simple sorting algorithm – last update here), I had picked up that there’s 16 general purpose 32bit registers for holding either values or addresses, R0 through to R15, but paying a closer look I realized some of these have specific purposes, and or uses by convention.

R0: function argument or result

R1-R3: function args

R4-12: general purpose

R13: SP – this is the stack pointer

R14: LR – Link Register – it’s holds the address to branch back to when you call BR LR

R15: PC – the Program Counter – address pointing to the current instruction being processed

More info in the great summary on ARM Assembly here, and also in the ARM11 tech ref here.

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