我如何使用 C++ 从寄存器中读取值

Question

我正在使用 C++ 为计算器编写代码，但它显示\\读取结果与汇编，我想将值存储在任何寄存器中，例如（Al）到 C++ 中的变量 int ......我搜索了但我总是找到它用C语言...

Answer 1

If you want to read value in al into an int :

GCC:

unsigned char out;
asm volatile("movb %%al, %[Var]" : [Var] "=r" (out));

Or

unsigned char out;
asm volatile("movb %%al, %0" : "=r" (out));

For MSVC:

unsigned char c;
__asm movb c, al

There's no official C++ way, it stems it from C.

EDIT

You might also want:

register unsigned char out asm("%al");

But that's GCC.

Answer 2

It is compiler dependent. For Intel with GCC:

//Read value from register
int x;

asm ("mov %0, AI;"
     :"=r"(x)
    );

Referencehere

Answer 3

You mean like:

int read_register_eax()
{
    int ret;
    asm { mov [ret],eax }
    return ret;
}