RTEMS CPU Architecture Supplement
The ARM architecture supports a simple yet effective call and
return mechanism. A subroutine is invoked via the branch and link
(bl) instruction. This instruction saves the return address
in the lr register. Returning from a subroutine only requires
that the return address be moved into the program counter (pc),
possibly with an offset. It is is important to note that the bl
instruction does not automatically save or restore any registers.
It is the responsibility of the high-level language compiler to define
the register preservation and usage convention.
RTEMS CPU Architecture Supplement
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