user: 下面的汇编指令对应的C源代码是什么：

```asm
<fmt_s16_dfp>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x50,%rsp
  mov    %rdi,-0x48(%rbp)
  mov    %esi,-0x4c(%rbp)
  mov    %edx,-0x50(%rbp)
  mov    %fs:0x28,%rax
  mov    %rax,-0x8(%rbp)
  xor    %eax,%eax
  movq   $0x0,-0x30(%rbp)
  cmpl   $0x4,-0x50(%rbp)
  jbe    L97
  mov    $0x0,%eax
  jmp    L10
L97:
  cmpl   $0x0,-0x50(%rbp)
  jne    L86
  mov    -0x4c(%rbp),%edx
  mov    -0x48(%rbp),%rax
  mov    %edx,%esi
  mov    %rax,%rdi
  call   <fmt_s16_dec@plt>
  jmp    L10
L86:
  cmpl   $0x0,-0x4c(%rbp)
  jns    L23
  cmpq   $0x0,-0x48(%rbp)
  je     L18
  mov    -0x30(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x30(%rbp)
  mov    -0x48(%rbp),%rdx
  add    %rdx,%rax
  movb   $0x2d,(%rax)
L18:
  negl   -0x4c(%rbp)
L23:
  mov    -0x50(%rbp),%eax
  mov    %eax,%esi
  mov    $0xa,%edi
  call   <pwr@plt>
  mov    %eax,-0x3c(%rbp)
  mov    -0x3c(%rbp),%ecx
  mov    -0x4c(%rbp),%eax
  cltd
  idiv   %ecx
  mov    %eax,-0x38(%rbp)
  mov    -0x4c(%rbp),%edx
  mov    -0x38(%rbp),%eax
  imul   -0x3c(%rbp),%eax
  mov    %eax,%ecx
  mov    %edx,%eax
  sub    %ecx,%eax
  mov    %eax,-0x34(%rbp)
  mov    -0x48(%rbp),%rdx
  mov    -0x30(%rbp),%rax
  add    %rax,%rdx
  mov    -0x38(%rbp),%eax
  mov    %eax,%esi
  mov    %rdx,%rdi
  call   <fmt_s16_dec@plt>
  add    %rax,-0x30(%rbp)
  cmpq   $0x0,-0x48(%rbp)
  jne    L21
  mov    -0x50(%rbp),%edx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  add    $0x1,%rax
  jmp    L10
L21:
  mov    -0x30(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x30(%rbp)
  mov    -0x48(%rbp),%rdx
  add    %rdx,%rax
  movb   $0x2e,(%rax)
  mov    -0x50(%rbp),%edx
  mov    -0x30(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x20(%rbp)
  mov    -0x34(%rbp),%edx
  lea    -0xc(%rbp),%rax
  mov    %edx,%esi
  mov    %rax,%rdi
  call   <fmt_s16_dec@plt>
  mov    %rax,-0x18(%rbp)
  jmp    L78
L60:
  mov    -0x30(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x30(%rbp)
  mov    -0x48(%rbp),%rdx
  add    %rdx,%rax
  movb   $0x30,(%rax)
L78:
  mov    -0x20(%rbp),%rax
  sub    -0x18(%rbp),%rax
  cmp    %rax,-0x30(%rbp)
  jb     L60
  movq   $0x0,-0x28(%rbp)
  jmp    L44
L83:
  mov    -0x30(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x30(%rbp)
  mov    -0x48(%rbp),%rdx
  add    %rax,%rdx
  lea    -0xc(%rbp),%rcx
  mov    -0x28(%rbp),%rax
  add    %rcx,%rax
  movzbl (%rax),%eax
  mov    %al,(%rdx)
  addq   $0x1,-0x28(%rbp)
L44:
  mov    -0x28(%rbp),%rax
  cmp    -0x18(%rbp),%rax
  jb     L83
  mov    -0x30(%rbp),%rax
L10:
  mov    -0x8(%rbp),%rdx
  sub    %fs:0x28,%rdx
  je     L35
  call   <__stack_chk_fail@plt>
L35:
  leave
  ret
```

assistant: ```c
size_t fmt_s16_dfp(char *out, int16_t val, unsigned fp_digits) {
  int16_t absolute, divider;
  size_t pos = 0;
  size_t div_len, len;
  unsigned e;
  char tmp[4];
  if (fp_digits > 4) {
    return 0;
  }
  if (fp_digits == 0) {
    return fmt_s16_dec(out, val);
  }
  if (val < 0) {
    if (out) {
      out[pos++] = '-';
    }
    val *= -1;
  }
  e = pwr(10, fp_digits);
  absolute = (val / (int)e);
  divider = val - (absolute * e);
  pos += fmt_s16_dec(&out[pos], absolute);
  if (!out) {
    return pos + 1 + fp_digits;
  }
  out[pos++] = '.';
  len = pos + fp_digits;
  div_len = fmt_s16_dec(tmp, divider);
  while (pos < (len - div_len)) {
    out[pos++] = '0';
  }
  for (size_t i = 0; i < div_len; i++) {
    out[pos++] = tmp[i];
  }
  return pos;
}
```