汇编语言学习系列 递归实现

假如汇编语言要实现如下C语言的功能，编译环境Ubuntu14.04（32位）。

#include<stdio.h>int refact(int n){    if(n == 1)        return 1;    else        return n * refact(n - 1);}int main(){    int a = 4;    printf("%d\n", refact(a));    return 0;}

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无论对于递归实现还是循环实现，汇编都是将转换为跳转语句实现。可以把上面的代码转换为

refact:    if((n-1) <= 0)    goto done;    body-statement        done:

• 汇编代码refact.s

.section .data        a: .int 4        format: .asciz "%d\n".section .text.global _start_start:        pushl %ebp        movl %esp, %ebp        subl $8, %esp #allocate storage space                movl a, %edx    #get a        movl %edx, (%esp)    #save value of a on stack                call refact                pushl %eax        pushl $format        call printf        movl $0, (%esp)        call exit                            refact:        pushl %ebp        movl %esp, %ebp        pushl %ebx        subl $4, %esp    #allocate storage space                movl 8(%ebp), %ebx    #get n        cmpl $1, %ebx            jle done    #test (n-1) >= 0                leal -1(%ebx), %eax    #(n-1)        movl %eax, (%esp)　　#save (n-1) on the stack        call refact        imul %ebx, %eax　　#use %eax to save result         done:            addl $4, %esp    #release space        popl %ebx        popl %ebp        ret        

• 编译

 as refact.s -o refact.o

• 链接

ld -lc -I /lib/ld-linux.so.2 refact.o -o refact

• 执行

 ./refact