ldr r2, [reg_base, #CPU_MODE] @ r2 = cpu_mode
ldr r1, [r1, r2, lsl #2] @ r1 = spsr[cpu_mode] (new cpsr)
str r1, [reg_base, #REG_CPSR] @ update cpsr
ldr r2, [reg_base, #CPU_MODE] @ r2 = cpu_mode
ldr r1, [r1, r2, lsl #2] @ r1 = spsr[cpu_mode] (new cpsr)
str r1, [reg_base, #REG_CPSR] @ update cpsr