在编译时将cpu:crotex-a7切换为crotex-m4时编译出错。如下：

Error： invalid immediate：-2147483648 is out of range
Error：value of -2147483648 too large for field of 2 bytes at 30
Error： invalid immediate：-2147483648 is out of range
Error：value of -2147483648 too large for field of 2 bytes at 42