2017-2018-1 20155312 《信息安全系统设计基础》第八周学习总结
题目要求
- 1 完成家庭作业4.47，4.48，4.49
- 2 相应代码反汇编成X86-64汇编
3 把上述X86-64汇编翻译成Y86汇编，并给出相应机器码
解答过程
4.47
void bubble_a(int *data, int count){ int i,next; for(next = 1; next < count; next++){ for(i = next - 1; i >= 0; i--) if(*(data + i + 1) < *(data + i)){ int t = *(data + i + 1); *(data + i + 1) = *(data + i); *(data + i) = t; } } } B
bubble_b:
.LFB22: .cfi_startproc pushl %edi .cfi_def_cfa_offset 8 .cfi_offset 7, -8 pushl %esi .cfi_def_cfa_offset 12 .cfi_offset 6, -12 pushl %ebx .cfi_def_cfa_offset 16 .cfi_offset 3, -16 movl 16(%esp), %edx movl 20(%esp), %edi cmpl $1, %edi jle .L1 subl $1, %edi movl $0, %esi .L6: movl %esi, %eax testl %esi, %esi js .L3 .L7: movl 4(%edx,%eax,4), %ecx movl (%edx,%eax,4), %ebx cmpl %ebx, %ecx jge .L4 movl %ebx, 4(%edx,%eax,4) movl %ecx, (%edx,%eax,4) .L4: subl $1, %eax cmpl $-1, %eax jne .L7 .L3: addl $1, %esi cmpl %edi, %esi jne .L6 .L1: popl %ebx .cfi_def_cfa_offset 12 .cfi_restore 3 popl %esi .cfi_def_cfa_offset 8 .cfi_restore 6 popl %edi .cfi_def_cfa_offset 4 .cfi_restore 7 ret .cfi_endproc .LFE22: .size bubble_b, .-bubble_b .section .rodata.str1.1,"aMS",@progbits,1 .LC0: .string "%d " .text .globl main .type main, @function
Y86
bubble_b:
.LFB22: .cfi_startproc pushl %edi .cfi_def_cfa_offset 8 .cfi_offset 7, -8 pushl %esi .cfi_def_cfa_offset 12 .cfi_offset 6, -12 pushl %ebx .cfi_def_cfa_offset 16 .cfi_offset 3, -16 mrmovl 16(%esp), %edx mrmovl 20(%esp), %edi irmovl $1, %eax subl %eax, %edi jle .L1 subl $1, %edi irmovl $0, %esi .L6: rrmovl %esi, %eax irmovl $0 , ebx subl %ebx, %esi jl .L3 .L7: rrmovl %eax, %ecx addl %ecx, %ecx addl %ecx, %ecx addl %edx, %ecx mrmovl 4(%ecx), %ecx rrmovl %eax, %ebx addl %ecx, %ebx addl %ecx, %ebx addl %edx, %ebx mrmovl (%ebx), %ebx subl %ebx, %ecx jge .L4 addl %eax, %eax addl %eax, %eax addl %edx, %eax rmmovl %ebx, 4(%eax) addl %eax, %eax addl %eax, %eax addl %edx, %eax rmmovl %ecx, 4(%eax) .L4: subl $1, %eax irmovl $-1, %edx subl %edx, %eax jne .L7 .L3: addl $1, %esi subl %edi, %esi jne .L6 .L1: popl %ebx .cfi_def_cfa_offset 12 .cfi_restore 3 popl %esi .cfi_def_cfa_offset 8 .cfi_restore 6 popl %edi .cfi_def_cfa_offset 4 .cfi_restore 7 ret .cfi_endproc .LFE22: .size bubble_b, .-bubble_b .section .rodata.str1.1,"aMS",@prog bits,1
4.48
修改4.47代码，实现冒泡排序函数的测试和交换，要求不使用跳转，且最多使用3次条件传送。
void bubble_c(int *data,int count) { int i , next; int pre_ele,next_ele; for(next = 1;next < count;next++) { for(i = next -1;i >= 0;i--) { pre_ele = *(data + i); next_ele = *(data + i + 1); *(data + i) = next_ele < pre_ele ? next_ele : pre_ele; *(data + i + 1) = next_ele < pre_ele ? pre_ele : next_ele; } } } Y86代码
.L6:
movl (%ebx,%eax,4), %edx movl 4(%ebx,%eax,4), %ecx cmpl %edx, %ecx movl %edx, %ebp cmovle %ecx, %ebp movl %ebp, (%ebx,%eax,4) cmovge %ecx, %edx movl %edx, 4(%ebx,%eax,4) subl $1, %eax cmpl $-1, %eax jne .L6
4.49
