关于汇编示例

#include <QCoreApplication>

int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);
#if 0//汇编右位移指令shr,左位移指令shl
    int a = 40;
    int b;
    asm ("movl %1, %%eax; \
    shl  %%eax; \
    shl  %%eax;\
    movl %%eax, %0;"
    : "=r" (b)
            : "r" (a)
            : "%eax");
    printf ("a = %d\nb = %d\n", a, b);
    system("pause");
#endif

#if 0//异或运算xor
    int a = 40;
    int b;
    asm ("movl %1, %%eax; \
    xor  %%eax,%%eax; \
    movl %%eax, %0;"
    : "=r" (b)
            : "r" (a)
            : "%eax");
    printf ("a = %d\nb = %d\n", a, b);
    system("pause");
#endif

#if 0//取反运算not
    int a = 40;
    int b;
    asm ("movl %1, %%eax; \
    not  %%eax; \
    movl %%eax, %0;"
    : "=r" (b)
            : "r" (a)
            : "%eax");
    printf ("a = %d\nb = %d\n", a, b);
    system("pause");
#endif

#if 0//或运算or
    int a = 40;
    int b;
    asm ("movl %1, %%eax; \
    or  %%eax,%%eax; \
    movl %%eax, %0;"
    : "=r" (b)
            : "r" (a)
            : "%eax");
    printf ("a = %d\nb = %d\n", a, b);
    system("pause");
#endif

#if 0//循环左移ROL,右移ROR
    int a = 6;
    int b = 0;
    asm ("movl %1, %%eax; \
    rol  %%eax; \
    movl %%eax, %0;"
    : "=r" (b)
            : "r" (a)
            : "%eax");
    printf ("a = %d\nb = %d\n", a, b);
    system("pause");
#endif

#if 0//循环左移ROL,右移ROR
    int s1 = 6;
    int s2 = 1;
    asm ("movl $0x01 , %%eax ; \n\t"
    "xorl %%edx , %%edx ;\n\t"
    "cpuid ;\n\t"
    "movl %%edx ,%0 ;\n\t"
    "movl %%eax ,%1 ; \n\t"
    :"=m"(s1),"=m"(s2));
    printf ("a = %d\nb = %d\n", s1, s);
    system("pause");

#endif
#if 1
    int a = 6;
    int b = 2;
    //asm volatile("movl %0,%1" : "=r" (b) : "m" (a));
    asm volatile("addl %2,%0":"=r"(a): "r"(a),"r"(b));
    printf ("a = %d\nb = %d\n", a, b);
    system("pause");

#endif

    return app.exec();
}