asm：operand number missing after %-letter

error: invalid 'asm': operand number missing after %-letter

代码如下：

int get_max(int *a, int len)
{
    assert(l % 4 == 0);
    int ret, tmp[4];

    __asm__ __volatile__(
        "xorps %%xmm0, %%xmm0\n"
        "LP3:\n\t"
        "movdqa %%xmm0, %%xmm1\n\t"
        "pcmpgtd (%1), %%xmm1\n\t"
        "andps %%xmm1, %%xmm0\n\t"
        "andnps (%1), %%xmm1\n\t"
        "orps %%xmm1, %xmm0\n\t"        // %xmm0 -> %%xmm0
        "addl $16, %1\n\t"
        "subl $4, %2\n\t"
        "jnz LP3\n\t"
        "movdqu %%xmm0, (%3)\n\t"
        "movl (%3), %%eax\n\t"
        "cmpl 4(%3), %%eax\n\t"
        "cmovll 4(%3), %%eax\n\t"
        "cmpl 8(%3), %%eax\n\t"
        "cmovll 8(%3), %%eax\n\t"
        "cmpl 12(%3), %%eax\n\t"
        "cmovll 12(%3), %%eax\n\t"
        "movl %%eax, %0\n"
        :"=m"(ret)
        :"r"(a),"r"(len),"r"(tmp)
        :"%eax"
    );

    return ret;
}

修改成

int get_max(int *a, int len)
{
    assert(l % 4 == 0);
    int ret, tmp[4];

    __asm__ __volatile__(
        "xorps %%xmm0, %%xmm0\n"
        "LP3:\n\t"
        "movdqa %%xmm0, %%xmm1\n\t"
        "pcmpgtd (%1), %%xmm1\n\t"
        "andps %%xmm1, %%xmm0\n\t"
        "andnps (%1), %%xmm1\n\t"
        "orps %%xmm1, %%xmm0\n\t"        // %xmm0 -> %%xmm0
        "addl $16, %1\n\t"
        "subl $4, %2\n\t"
        "jnz LP3\n\t"
        "movdqu %%xmm0, (%3)\n\t"
        "movl (%3), %%eax\n\t"
        "cmpl 4(%3), %%eax\n\t"
        "cmovll 4(%3), %%eax\n\t"
        "cmpl 8(%3), %%eax\n\t"
        "cmovll 8(%3), %%eax\n\t"
        "cmpl 12(%3), %%eax\n\t"
        "cmovll 12(%3), %%eax\n\t"
        "movl %%eax, %0\n"
        :"=m"(ret)
        :"r"(a),"r"(len),"r"(tmp)
        :"%eax"
    );

    return ret;
}

编译通过。