编译器如何知道C中的指针地址是端口映射还是RAM？

I know that port mapped IO are accessed thorugh in/out CPU instructions and memory (& memory mapped registers) are accessed through load/store CPU instructions (similar to memory). But, with a pointer in C code, how compiler knows if a address is port mapped IO register or memory and then inserts the correct CPU instructions? I know that port mapped IO are accessed thorugh