7 运算符

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李延 LV6 2022-06-01

悬赏：20积分

# 1 四则运算

## 1.1 add 指令

```
addq A,B
```

将A 与 B 相加，并将结果保存再B 中

测试：

```asm
.LC0:
    .string    "add %lu\n"

.globl main
main:
   subq   $56, %rsp
   movq      $1, %rbx
   addq   $2, %rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果

```shell
[root@localhost operation]# ./a.out 
add 3

```

### 1.1.1 相加为寄存器

并且两个计算也可以是 寄存器

```asm
.LC0:
    .string    "add %lu\n"

.globl main
main:
   subq   $56, %rsp
   movq      $1, %rbx
   movq      $2, %rcx
   addq   %rcx, %rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

### 1.1.2 相加为内存

两个参数 其中任意一个可以是内存，如下：

```asm
.LC0:
    .string    "add %lu\n"

.globl main
main:
   subq   $24, %rsp
   movq   $3, (%rsp)
   movq      $2,  %rbx
   addq   (%rsp), %rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf
   movl   $0, %eax
   addq   $24, %rsp
   ret
```

```asm
.LC0:
    .string    "add %lu\n"

.globl main
main:
   subq   $24, %rsp
   movq   $3, (%rsp)
   movq      $2,  %rbx
   addq   %rbx,(%rsp)
   movl   $.LC0, %edi
   movq      (%rsp), %rsi
   call   printf
   movl   $0, %eax
   addq   $24, %rsp
   ret
```

结果：

```shell
[root@localhost operation]# ./a.out 
add 5

```

但不可以两个都为内存寻址

```asm
.LC0:
    .string    "add %lu\n"

.globl main
main:
   subq   $24, %rsp
   movq   $3, (%rsp)

addq   (%rsp),(%rsp)
   movl   $.LC0, %edi
   movq      (%rsp), %rsi
   call   printf
   movl   $0, %eax
   addq   $24, %rsp
   ret
```

会报异常：

```shell
root@localhost operation]# gcc add5.s 
add5.s: Assembler messages:
add5.s:10: 错误：too many memory references for `add'

```

## 1.2 减法

```asm
.LC0:
    .string    "imul %lld\n"

.globl main
main:
   subq   $56, %rsp
   movq      $1, %rbx
   subq   $2, %rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果

```shell
[root@localhost operation]# ./a.out 
imul -1

```

## 1.3 乘法

```asm
.LC0:
    .string    "imul %lld\n"

.globl main
main:
   subq   $56, %rsp
   movq      $2, %rbx
   imul   $5, %rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果

```sh
[root@localhost operation]# ./a.out 
imul 10

```

# 2 递增与递减

## 2.1 inc

加1

```asm
.LC0:
    .string    "add %lu\n"

.globl main
main:
   subq   $56, %rsp
   movq      $6, %rbx
   inc    %rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

jieg

```sh
[root@localhost operation]# ./a.out 
add 7

```

## 2.2 dec

减1

```asm
.LC0:
    .string    "add %lu\n"

.globl main
main:
   subq   $56, %rsp
   movq      $6, %rbx
   dec    %rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果：

```
[root@localhost operation]# ./a.out 
add 5

```

# 3 取负和取补

not 取补

```asm
.LC0:
    .string    "not %lld\n"

.globl main
main:
   subq   $56, %rsp
   movq      $6, %rbx
   not    %rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果： -7

neg 取负

```asm
.LC0:
    .string    "neg %lld\n"

.globl main
main:
   subq   $56, %rsp
   movq      $6, %rbx
   neg    %rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果 ： -6

# 4 或、与

or 或运算

示例：

```asm
.LC0:
    .string    "imul %llu\n"

.globl main
main:
   subq   $56, %rsp
   movq   $0B1101, %rbx
   movq   $0B1011, %rcx
   and    %rcx,%rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果：15. 转换为二进制 为 1111 。 刚好就是我们在编码中 使用的 | 计算

and 与运算

示例：

```asm
.LC0:
    .string    "imul %lld\n"

.globl main
main:
   subq   $56, %rsp
   movq      $0B1101, %rbx
   movq   $0B1011, %rcx
   andq    %rcx,%rbx
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果为9. 二进制 ： 1001

# 5 位运算

## 5.1 左移

sal 与shl 。 对应编码中的 '<<' 和 '<<<'

示例

```asm
.LC0:
    .string    "not %lld\n"

.globl main
main:
   subq   $56, %rsp
   movq      $0B10111111, %rbx
   sal    $1, %bxl
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果：126  二进制：01111110

## 5.2  算数右移

sar 对应编码中的 '>>'

```asm
.LC0:
    .string    "not %lld\n"

.globl main
main:
   subq   $56, %rsp
   movq      $0B10111111, %rbx
   sar    $1, %bxl
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果：223 二进制：11011111

## 5.3 逻辑右移

shr 对应编码中的 '>>>'

```asm
.LC0:
    .string    "not %lld\n"

.globl main
main:
   subq   $56, %rsp
   movq      $0B10111111, %rbx
   shr    $1, %bxl
   movl   $.LC0, %edi
   movq      %rbx, %rsi
   call   printf

movl   $0, %eax
   addq   $56, %rsp
   ret
```

结果：95 二进制：01011111

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