can't find a register in class creg while reloading asm

    今天看linux内核0.11版的内存管理代码，里面用位图定义了内存的布局，但是代码在ubuntu 12.04上面没能编译成功，报了can't find a register in class creg while reloading asm错误
   

__asm__("std;repne;scasbnt"
            "jne 1f\n\t"
            "movb $1,1(%%edi)\n\t"
            "sall $12,%%ecx\n\t"
            "addl %2,%%ecx\n\t"
            "movl %%ecx,%%edx\n\t"
            "movl $1024,%%ecx\n\t"
            "leal 4092(%%edx),%%edi\n\t"
            "rep;stosl\n\t"
            "movl %%edx,%%eax\n"
            "1:"
            :"=a"(__res)
            :""(0),"i"(LOW_MEM),"c"(PAGING_PAGES),
            "D"(mem_map + PAGING_PAGES - 1)
            :"cx","di","dx");

，我就上网上搜索了一下。原来gcc版本升级了，假设你告诉编译器你使用了一个寄存器，等你再次使用它的时候你直接告诉编译器这个寄存器的号码就行啦，不然编译器以为你需要用两个这样的寄存器就会报错，现在只需要把相同的寄存器改成编号就行啦。

__asm__("std;repne;scasbnt"
            "jne 1f\n\t"
            "movb $1,1(%%edi)\n\t"
            "sall $12,%%ecx\n\t"
            "addl %2,%%ecx\n\t"
            "movl %%ecx,%%edx\n\t"
            "movl $1024,%%ecx\n\t"
            "leal 4092(%%edx),%%edi\n\t"
            "rep;stosl\n\t"
            "movl %%edx,%%eax\n"
            "1:"
            :"=a"(__res)
            :"0"(0),"i"(LOW_MEM),"c"(PAGING_PAGES),
            "D"(mem_map + PAGING_PAGES - 1)
            :"3","4","dx");