匯編語言學習系列 for循環實現

假如匯編語言要實現如下C語言的功能，編譯環境Ubuntu14.04（32位）。

#include<stdio.h>
int fact_for(int n)
{int i;int result = 1;for(i = 2; i <= n; i++)result *= i;return result;
}int main(){printf("%d\n", fact_for(3));return 0;
}

• 代碼for.s

.section .datan: .int 3format: .asciz "%d\n"
.section .text
.global _start
_start:pushl %ebpmovl %esp, %ebpsubl $8, %espmovl n, %ecx        movl %ecx, (%esp)call fact_forpushl %eaxpushl $formatcall printfmovl $0, (%esp)call exitfact_for:pushl %ebpmovl %esp, %ebppushl %ebxmovl 8(%ebp), %edx    #get nmovl $1, %eax        #init resultmovl $2, %ecx        #init icmp %ecx, %edxjl .done.loop:imul %ecx, %eaxinc %ecxcmp %ecx, %edxjge .loop.done:popl %ebxpopl %ebpret        

• 編譯

?as for.s -o for.o

• 鏈接

ld -lc -I /lib/ld-linux.so.2 for.o -o?for

• 執行

?./for