user: 请从给定的汇编指令推导出C源代码:

```asm
<mult_expr>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x40,%rsp
  mov    %rdi,-0x38(%rbp)
  mov    -0x38(%rbp),%rax
  mov    %rax,%rdi
  call   <cast_expr@plt>
  mov    %rax,-0x20(%rbp)
L57:
  movl   $0x0,-0x30(%rbp)
  mov    -0x38(%rbp),%rax
  mov    %rax,%rdi
  call   <peek@plt>
  mov    %eax,-0x28(%rbp)
  cmpl   $0xc,-0x28(%rbp)
  je     L158
  cmpl   $0xc,-0x28(%rbp)
  jl     L155
  mov    -0x28(%rbp),%eax
  sub    $0x28,%eax
  cmp    $0x1,%eax
  ja     L155
L158:
  mov    -0x20(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <read_expr@plt>
  mov    %rax,-0x18(%rbp)
  mov    -0x18(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <arithmetic@plt>
  mov    -0x28(%rbp),%edx
  mov    -0x38(%rbp),%rax
  mov    %edx,%esi
  mov    %rax,%rdi
  call   <eat@plt>
  mov    -0x38(%rbp),%rax
  mov    %rax,%rdi
  call   <cast_expr@plt>
  mov    %rax,%rdx
  mov    -0x38(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <read_expr@plt>
  mov    %rax,-0x10(%rbp)
  mov    -0x10(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <arithmetic@plt>
  mov    -0x10(%rbp),%rdx
  mov    -0x18(%rbp),%rcx
  mov    -0x38(%rbp),%rax
  mov    %rcx,%rsi
  mov    %rax,%rdi
  call   <arithmetic_result@plt>
  mov    %rax,-0x8(%rbp)
  mov    -0x8(%rbp),%rax
  mov    %rax,%rdi
  call   <is_signed@plt>
  mov    %eax,-0x24(%rbp)
  movl   $0xffffffff,-0x2c(%rbp)
  cmpl   $0x29,-0x28(%rbp)
  je     L70
  cmpl   $0x29,-0x28(%rbp)
  jg     L100
  cmpl   $0xc,-0x28(%rbp)
  je     L97
  cmpl   $0x28,-0x28(%rbp)
  je     L111
  jmp    L100
L97:
  cmpl   $0x0,-0x24(%rbp)
  je     L138
  mov    $0x2,%eax
  jmp    L16
L138:
  mov    $0x3,%eax
L16:
  mov    %eax,-0x2c(%rbp)
  jmp    L100
L111:
  cmpl   $0x0,-0x24(%rbp)
  je     L173
  mov    $0x4,%eax
  jmp    L68
L173:
  mov    $0x5,%eax
L68:
  mov    %eax,-0x2c(%rbp)
  jmp    L100
L70:
  cmpl   $0x0,-0x24(%rbp)
  je     L127
  mov    $0x6,%eax
  jmp    L110
L127:
  mov    $0x7,%eax
L110:
  mov    %eax,-0x2c(%rbp)
  nop
L100:
  mov    -0x10(%rbp),%rdi
  mov    -0x18(%rbp),%rcx
  mov    -0x8(%rbp),%rdx
  mov    -0x2c(%rbp),%esi
  mov    -0x38(%rbp),%rax
  mov    %rdi,%r8
  mov    %rax,%rdi
  call   <triple@plt>
  mov    %rax,-0x20(%rbp)
  jmp    L105
L155:
  movl   $0x1,-0x30(%rbp)
  nop
L105:
  cmpl   $0x0,-0x30(%rbp)
  je     L57
  mov    -0x20(%rbp),%rax
  leave
  ret
```

assistant: ```c
struct triple *mult_expr(struct compile_state *state) {
  struct triple *def;
  int done;
  def = cast_expr(state);
  do {
    struct triple *left, *right;
    struct type *result_type;
    int tok, op, sign;
    done = 0;
    tok = peek(state);
    switch (tok) {
    case 12:
    case 40:
    case 41:
      left = read_expr(state, def);
      arithmetic(state, left);
      eat(state, tok);
      right = read_expr(state, cast_expr(state));
      arithmetic(state, right);
      result_type = arithmetic_result(state, left, right);
      sign = is_signed(result_type);
      op = -1;
      switch (tok) {
      case 12:
        op = sign ? 2 : 3;
        break;
      case 40:
        op = sign ? 4 : 5;
        break;
      case 41:
        op = sign ? 6 : 7;
        break;
      }
      def = triple(state, op, result_type, left, right);
      break;
    default:
      done = 1;
      break;
    }
  } while (!done);
  return def;
}
```