You can use the Program Counter explicitly, for example in some ARM data processing instructions, and implicitly, for example in branch instructions.
The Program Counter (PC) is accessed as PC (or R15). It is incremented by the size of the instruction executed (which is always four bytes in ARM state). Branch instructions load the destination address into PC. You can also load the PC directly using data processing instructions. For example, to branch to the address in a general purpose register, use:
During execution, PC does not contain the address of the currently executing instruction. The address of the currently executing instruction is typically PC–8 for ARM, or PC–4 for Thumb.
ARM recommends you use the
BX instruction to jump to an address or to return
from a function, rather than writing to the PC directly.