user: 请将这段汇编代码片段转换成等效的C代码：

```asm
<bn_mul_low_recursive>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x40,%rsp
  mov    %rdi,-0x18(%rbp)
  mov    %rsi,-0x20(%rbp)
  mov    %rdx,-0x28(%rbp)
  mov    %ecx,-0x2c(%rbp)
  mov    %r8,-0x38(%rbp)
  mov    -0x2c(%rbp),%eax
  mov    %eax,%edx
  shr    $0x1f,%edx
  add    %edx,%eax
  sar    %eax
  mov    %eax,-0x4(%rbp)
  mov    -0x38(%rbp),%rdi
  mov    -0x4(%rbp),%ecx
  mov    -0x28(%rbp),%rdx
  mov    -0x20(%rbp),%rsi
  mov    -0x18(%rbp),%rax
  mov    %rdi,%r8
  mov    %rax,%rdi
  call   <bn_mul_recursive@plt>
  cmpl   $0x1f,-0x4(%rbp)
  jle    L1
  mov    -0x2c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  lea    (%rdx,%rax,1),%rcx
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x28(%rbp),%rax
  lea    (%rdx,%rax,1),%rdi
  mov    -0x4(%rbp),%edx
  mov    -0x20(%rbp),%rsi
  mov    -0x38(%rbp),%rax
  mov    %rcx,%r8
  mov    %edx,%ecx
  mov    %rdi,%rdx
  mov    %rax,%rdi
  call   <bn_mul_low_recursive>
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x18(%rbp),%rax
  lea    (%rdx,%rax,1),%rsi
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x18(%rbp),%rax
  lea    (%rdx,%rax,1),%rdi
  mov    -0x4(%rbp),%edx
  mov    -0x38(%rbp),%rax
  mov    %edx,%ecx
  mov    %rax,%rdx
  call   <bn_add_words@plt>
  mov    -0x2c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  lea    (%rdx,%rax,1),%rdi
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x20(%rbp),%rax
  lea    (%rdx,%rax,1),%rsi
  mov    -0x4(%rbp),%ecx
  mov    -0x28(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  mov    %rdi,%r8
  mov    %rax,%rdi
  call   <bn_mul_low_recursive>
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x18(%rbp),%rax
  lea    (%rdx,%rax,1),%rsi
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x18(%rbp),%rax
  lea    (%rdx,%rax,1),%rdi
  mov    -0x4(%rbp),%edx
  mov    -0x38(%rbp),%rax
  mov    %edx,%ecx
  mov    %rax,%rdx
  call   <bn_add_words@plt>
  jmp    L5
L1:
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x28(%rbp),%rax
  lea    (%rdx,%rax,1),%rdi
  mov    -0x4(%rbp),%edx
  mov    -0x20(%rbp),%rsi
  mov    -0x38(%rbp),%rax
  mov    %edx,%ecx
  mov    %rdi,%rdx
  mov    %rax,%rdi
  call   <bn_mul_low_normal@plt>
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x20(%rbp),%rax
  lea    (%rdx,%rax,1),%rsi
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  lea    (%rdx,%rax,1),%rdi
  mov    -0x4(%rbp),%edx
  mov    -0x28(%rbp),%rax
  mov    %edx,%ecx
  mov    %rax,%rdx
  call   <bn_mul_low_normal@plt>
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x18(%rbp),%rax
  lea    (%rdx,%rax,1),%rsi
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x18(%rbp),%rax
  lea    (%rdx,%rax,1),%rdi
  mov    -0x4(%rbp),%edx
  mov    -0x38(%rbp),%rax
  mov    %edx,%ecx
  mov    %rax,%rdx
  call   <bn_add_words@plt>
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x38(%rbp),%rax
  add    %rax,%rdx
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rcx
  mov    -0x18(%rbp),%rax
  lea    (%rcx,%rax,1),%rsi
  mov    -0x4(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rcx
  mov    -0x18(%rbp),%rax
  lea    (%rcx,%rax,1),%rdi
  mov    -0x4(%rbp),%eax
  mov    %eax,%ecx
  call   <bn_add_words@plt>
L5:
  nop
  leave
  ret
```

assistant: ```c
void bn_mul_low_recursive(unsigned long long *r, unsigned long long *a, unsigned long long *b, int n2, unsigned long long *t) {
  int n = n2 / 2;
  bn_mul_recursive(r, a, b, n, &(t[0]));
  if (n >= (32)) {
    bn_mul_low_recursive(&(t[0]), &(a[0]), &(b[n]), n, &(t[n2]));
    bn_add_words(&(r[n]), &(r[n]), &(t[0]), n);
    bn_mul_low_recursive(&(t[0]), &(a[n]), &(b[0]), n, &(t[n2]));
    bn_add_words(&(r[n]), &(r[n]), &(t[0]), n);
  } else {
    bn_mul_low_normal(&(t[0]), &(a[0]), &(b[n]), n);
    bn_mul_low_normal(&(t[n]), &(a[n]), &(b[0]), n);
    bn_add_words(&(r[n]), &(r[n]), &(t[0]), n);
    bn_add_words(&(r[n]), &(r[n]), &(t[n]), n);
  }
}
```