计算机系统课程作业

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# include "stdio.h"# define H ? //定义常数H# define J ? //定义常数Jint array1[H][J]; int array2[J][H]; void f(int x, int y) {array1[x][y] = x+2*y;array2[y][x]=y-x*x;}int main( ){return 0;}

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一、H=37,J=16pushl %ebp 前两行压程序栈movl %esp,%ebppush %ebx 压 f 函数栈movl 8(%ebp), %ecx 赋值 xmovl 12(%ebp), %edx 赋值 ymovl 12(%ebp), %eax 赋值 yaddl %eax, %eax eax 自增为 2 倍(2y)addl 8(%ebp), %eax eax=eax+ecx x+2*ysall $4, %ecx ecx 的值左移 4 位 x*16leal (%ecx,%edx), %edx 把 ecx+edx 的地址给 edx x*16+y 即 x 的系数 J=16movl %eax, array1(,%edx,4) 把 eax 的值给 array1 的 edx* 4 位的地方 4*(x* 16+y)的地方=x+2* y，即 array1[x][y]=x+2*ymovl 12(%ebp), %edx 赋值 ymovl 8(%ebp), %ebx 赋值 xmovl 8(%ebp), %eax 赋值 ximull 8(%ebp), %eax eax=eax* eax x*xmovl 12(%ebp), %ecx ecx=edx ecx 处=ysubl %eax, %ecx ecx=ecx-eax y-x*xmovl %edx, %eax eax=edx eax 处=ysall $3, %eax eax < < 3 相当于y < < 3 3 即是 J 的值addl %edx, %eax eax=eax+edx y< <3+ysall $2, %eax eax< <2 (y< <3+y)< <2addl %edx, %eax eax=edx+eax (y< <3+y)< <2+yaddl %ebx, %eax eax=eax+ebx (y< <3+y)< <2+y+x 即 y 的系数 H=(8+1)*4+1=37movl %ecx, array2(,%eax,4) 把 array2 的 4* eax 的地方赋值为 ecx 即 array2 的 4*eax 的地方=y-x *x 即 array2[x][y]=y-x*xpopl %ebx 出函数栈popl %ebp 出栈ret 结束程序

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二、int aprod(int a[], int n) {int i, x, y, z;int r = 1;for (i = 0; （ i< n-2 ）; （ i+=3 ）) {（ x=a[i] ）;（ y=a[i+1] ）;（ z=a[i+2] ）;（ r=r*x*y*z* ）; } for (; i < n; i++) （ r=a[i]*r ）; return r;}

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汇编分析：aprod:pushl %ebp //前两行压栈movl %esp, %ebp //栈帧subl $32, %esp //esp-32movl $1, -20(%ebp) //ebp小20的位置放1 r=1movl $0, -4(%ebp) //ebp小4的位置放0 i=0jmp.L2 //无条件跳转到.L2.L3:movl -4(%ebp), %eax //eax=0=isall $2, %eax //eax=0*4=0addl 8(%ebp), %eax //eax加上ebp大8的位置,即eax+=a[]movl (%eax), %eax //eax=a[i]movl %eax, -8(%ebp) //ebp小8的地方赋值为eax x=a[i] movl -4(%ebp), %eax //eax=i=0addl $1, %eax //eax=i+1=1,sall $2, %eax //eax=4addl 8(%ebp), %eax //eax加上ebp大8的位置 eax=4+a[]movl (%eax), %eax //eax=a[i+1]movl %eax, -12(%ebp) //ebp小12的位置变为eax y=a[i+1]movl -4(%ebp), %eax //eax=ebp小4的位置 eax=i=0addl $2, %eax //eax+=2 eax=2sall $2, %eax //eax*=4 eax=8addl 8(%ebp), %eax //eax+ebp大8的位置 eax=8+a[]movl (%eax), %eax //eax=a[i+2]movl %eax, -16(%ebp) //ebp小16的位置放eax z=eax=a[i+2]movl -20(%ebp), %eax //eax=1=rimull -8(%ebp), %eax //eax*ebp小8处的位置的值 eax=r *ximull -12(%ebp), %eax //eax*ebp小12处的位置的值 eax=r *x *yimull -16(%ebp), %eax //eax*ebp小16处的位置的值 eax=r *x *y *zmovl %eax, -20(%ebp) //ebp小20处的位置的值变为eax r=eaxaddl $3, -4(%ebp) ebp小4处的位置的值加三 i=i+3.L2:movl 12(%ebp), %eax //eax被赋值为ebp大12的位置的值 eax=n,subl $2, %eax //eax-2 eax=n-2cmpl -4(%ebp), %eax //比较eax和ebp小4处的值谁大，小于跳到L3,大于等于跳到L4 即比较i和n-2的大小，i>n-2跳转到L3jg.L3 jmp.L4.L5:movl -4(%ebp), %eax //eax=0=isall $2, %eax //eax*4addl 8(%ebp), %eax //eax+大于ebp8的位置的值 即eax=0+a[]movl (%eax), %eax //eax=a[i]movl -20(%ebp), %edx //edx=1=r imull %edx, %eax //eax*=edx 即eax=a[i]*rmovl %eax, -20(%ebp) //ebp小20处的位置的值等于eax r=eaxaddl $1, -4(%ebp) //ebp小4处的位置的值+=1 i+=1.L4:movl -4(%ebp), %eax //eax=0cmpl 12(%ebp), %eax //比较eax和比ebp大12处的位置的值，小于则跳转到L5jl.L5movl -20(%ebp), %eax //eax=ebp小20处的位置的值leave //退出ret

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三、#include <stdio.h>int frac(int a){if(a<2) return a*a;return frac(a-2)+a;}int sum(int a,int b){int c=frac(a+b);return 2*c+b;}int main(){int i=10,j=6;int k=sum(j-i,i++);return 0;}

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汇编代码：frac:pushl %ebp //压栈movl %esp, %ebp //栈帧subl $24, %esp //esp-24，开辟空间cmpl $1, 8(%ebp) //比较1和a的大小，a>1则跳到L2jg .L2movl 8(%ebp), %eax //eax=aimull 8(%ebp), %eax //eax*=eax,eax=a*ajmp .L3 //无条件跳转到L3.L2:movl 8(%ebp), %eax //eax=asubl $2, %eax //eax-=2 eax=a-2movl %eax, (%esp) //esp的位置=eax=a-2call frac //调用frac,此时由于esp的位置是a-2,因此相当于frac(a-2)addl 8(%ebp), %eax //eax+=a,即eax=frac(a-2)+a.L3:leave //退出 retsum:pushl %ebp //压栈movl %esp, %ebp //栈帧subl $40, %esp //esp-40开辟空间movl 12(%ebp), %eax //eax=bmovl 8(%ebp), %edx //edx=aaddl %edx, %eax //eax+=edx,eax=b+amovl %eax, (%esp) //eax给到espcall frac //调用frac函数,同上面的那个frac,相当于frac(a+b)movl %eax, -12(%ebp) //c=frac(a+b)movl -12(%ebp), %eax //eax=caddl %eax, %eax //eax+=eax,eax=2*caddl 12(%ebp), %eax //eax+=b,eax=2*c+bleaveretmain:pushl %ebp //压栈movl %esp, %ebp //栈帧andl $-16, %esp //esp和-16与运算subl $32, %esp //esp-32开辟空间movl $10, 20(%esp) //i=10movl $6, 24(%esp) //j=6movl 20(%esp), %eax //eax=10=imovl 24(%esp), %edx //edx=6=jsubl %eax, %edx //edx=-4movl 20(%esp), %eax //eax=10addl $1, 20(%esp) //i=11movl %edx, 4(%esp) //esp大于4处=-4movl %eax, (%esp) //eax给到esp=10call sum //调用sum,sum函数需要两个参数，这两个参数在上面，也就是sum(j-i,i++)movl %eax, 28(%esp) //esp大于28处=10,即k=eax=sum(j-i,i++)movl $0, %eax //eax=0leave //退出ret