r10 sl Stack limit

r11 fp Argument pointer

r12 ip Temporary workspace. Register r12 (IP) may be used by a linker as a scratch register between a routine and any subroutine it calls (for details, see §5.3.1.1, Use of IP by the linker). It can also be used within a routine to hold intermediate values between subroutine calls.

r13 sp Stack pointer

r14 lr Link register Workspace