from zephyr.c:200
static const struct rtos_register_stacking arm_cpu_saved_nofp_stacking = {
.stack_registers_size = 32,
.stack_growth_direction = -1,
.num_output_registers = ARRAY_SIZE(arm_cpu_saved),
.calculate_process_stack = zephyr_cortex_m_stack_align,
.register_offsets = arm_cpu_saved,
};