C++中的内联汇编怎么用_C++代码中嵌入底层汇编指令进行极致优化

asm("汇编指令"
    : 输出操作数
    : 输入操作数
    : 被破坏的寄存器列表);

int a = 10, b = 20;<br>
asm("xchg %0, %1"<br>
    : "=r"(a), "=r"(b)  // 输出<br>
    : "0"(a), "1"(b)     // 输入<br>
    : "memory");          // 告诉编译器内存可能被修改

int a = 10, b = 20;<br>
__asm {<br>
    mov eax, a<br>
    mov ebx, b<br>
    xchg eax, ebx<br>
    mov a, eax<br>
    mov b, ebx<br>
}

int trailing_zero(unsigned int x) {<br>
    int result;<br>
    asm("bsf %1, %0"<br>
        : "=r"(result)<br>
        : "r"(x)<br>
        : "cc");<br>
    return result;<br>
}

float a[4] = {1.0f}, b[4] = {2.0f}, c[4];<br>
asm("movaps (%1), %%xmm0<br>
     movaps (%2), %%xmm1<br>
     addps %%xmm1, %%xmm0<br>
     movaps %%xmm0, (%0)"<br>
    :<br>
    : "r"(c), "r"(a), "r"(b)<br>
    : "xmm0", "xmm1", "memory");

#include <immintrin.h><br>
__m128 va = _mm_load_ps(a);<br>
__m128 vb = _mm_load_ps(b);<br>
__m128 vc = _mm_add_ps(va, vb);<br>
_mm_store_ps(c, vc);