user: Converte this assembly snippet into its equivalent C code:

```asm
<mp_mul>:
  endbr64
  push   %r15
  mov    %rcx,%rax
  mov    %r8,%r10
  push   %r14
  mov    %esi,%r14d
  push   %r13
  push   %r12
  push   %rbp
  mov    %edi,%ebp
  push   %rbx
  mov    %rdx,%rbx
  sub    $0x58,%rsp
  mov    0x90(%rsp),%r13d
  mov    0xa0(%rsp),%rdi
  mov    %r9,0x28(%rsp)
  mov    0xa8(%rsp),%rsi
  mov    0x98(%rsp),%r15
  mov    %r13d,%r12d
  mov    %rdi,0x18(%rsp)
  mov    0xb0(%rsp),%rdi
  mov    %rsi,(%rsp)
  sar    %r12d
  mov    0xb8(%rsp),%rsi
  add    $0x1,%r12d
  mov    %rdi,0x8(%rsp)
  mov    %rsi,0x10(%rsp)
  cmp    %ebp,%r12d
  jge    L36
  movslq %r12d,%rdx
  jmp    L31
  nopl   0x0(%rax)
L30:
  lea    0x1(%rdx),%r12d
  add    $0x1,%rdx
  cmp    %edx,%ebp
  jle    L36
L31:
  mov    0x8(%rax,%rdx,4),%ecx
  add    0x8(%rbx,%rdx,4),%ecx
  mov    %edx,%r12d
  je     L30
L36:
  mov    %ebp,%edx
  mov    %ebp,%ecx
  mov    %r15,%r9
  mov    %rbx,%r8
  shr    $0x1f,%edx
  sub    %r12d,%ecx
  mov    %r14d,%esi
  mov    %ebp,%edi
  add    %ebp,%edx
  mov    %r10,0x48(%rsp)
  sar    %edx
  mov    %rax,0x38(%rsp)
  add    $0x1,%edx
  cmp    %ecx,%edx
  cmovge %edx,%ecx
  mov    %r13d,%edx
  mov    %ecx,0x34(%rsp)
  xor    %ecx,%ecx
  call   <mp_mul_i2d@plt>
  lea    0x8(%r15),%rax
  mov    0x10(%rsp),%r8
  mov    %r13d,%edi
  mov    0x8(%rsp),%rcx
  mov    %rax,%rdx
  mov    $0x1,%esi
  mov    %rax,0x20(%rsp)
  call   <rdft@plt>
  mov    0x38(%rsp),%rax
  mov    (%rsp),%r9
  mov    %ebp,%edi
  mov    %r12d,%ecx
  mov    %r13d,%edx
  mov    %r14d,%esi
  mov    %rax,%r8
  mov    %rax,0x40(%rsp)
  call   <mp_mul_i2d@plt>
  mov    (%rsp),%rax
  mov    0x10(%rsp),%r8
  mov    %r13d,%edi
  mov    0x8(%rsp),%rcx
  mov    $0x1,%esi
  lea    0x8(%rax),%r11
  mov    %r11,%rdx
  mov    %r11,0x38(%rsp)
  call   <rdft@plt>
  mov    (%rsp),%rdx
  mov    %r15,%rsi
  mov    %r13d,%edi
  call   <mp_mul_cmul@plt>
  mov    0x18(%rsp),%r9
  mov    %r13d,%edx
  mov    %r14d,%esi
  mov    0x40(%rsp),%r8
  mov    %ebp,%edi
  xor    %ecx,%ecx
  call   <mp_mul_i2d@plt>
  mov    0x18(%rsp),%rsi
  mov    0x10(%rsp),%r8
  mov    %r13d,%edi
  mov    0x8(%rsp),%rcx
  lea    0x8(%rsi),%rdx
  mov    $0x1,%esi
  call   <rdft@plt>
  mov    0x18(%rsp),%rsi
  mov    %r15,%rdx
  mov    %r13d,%edi
  call   <mp_mul_cmul@plt>
  mov    0x10(%rsp),%r8
  mov    0x8(%rsp),%rcx
  mov    %r13d,%edi
  mov    0x20(%rsp),%rdx
  mov    $0xffffffff,%esi
  call   <rdft@plt>
  mov    0x28(%rsp),%r8
  mov    %r15,%rcx
  mov    %r13d,%edx
  mov    %r14d,%esi
  mov    %ebp,%edi
  call   <mp_mul_d2i@plt>
  mov    %r15,%r9
  mov    %rbx,%r8
  mov    %r12d,%ecx
  mov    %r13d,%edx
  mov    %r14d,%esi
  mov    %ebp,%edi
  call   <mp_mul_i2d@plt>
  mov    0x10(%rsp),%r12
  mov    0x8(%rsp),%rbx
  mov    %r13d,%edi
  mov    0x20(%rsp),%rdx
  mov    $0x1,%esi
  mov    %r12,%r8
  mov    %rbx,%rcx
  call   <rdft@plt>
  mov    (%rsp),%rcx
  mov    %r15,%rsi
  mov    %r13d,%edi
  mov    0x18(%rsp),%rdx
  call   <mp_mul_cmuladd@plt>
  mov    0x38(%rsp),%rdx
  mov    %r12,%r8
  mov    %rbx,%rcx
  mov    %r13d,%edi
  mov    $0xffffffff,%esi
  call   <rdft@plt>
  mov    0x48(%rsp),%r10
  mov    %r13d,%edx
  mov    %r14d,%esi
  mov    (%rsp),%rcx
  mov    0x34(%rsp),%edi
  mov    %r10,%r8
  mov    %r10,0x8(%rsp)
  call   <mp_mul_d2i@plt>
  mov    0x8(%rsp),%r10
  mov    %r14d,%esi
  mov    %ebp,%edi
  mov    0x28(%rsp),%rcx
  add    $0x58,%rsp
  pop    %rbx
  mov    %r10,%r8
  pop    %rbp
  mov    %r10,%rdx
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  jmp    10d0 <mp_add@plt>
```

assistant: ```c
void mp_mul(int n, int radix, int in1[], int in2[], int out[], int tmp[], int nfft, double tmp1fft[], double tmp2fft[], double tmp3fft[], int ip[], double w[]) {
  void mp_add(int n, int radix, int in1[], int in2[], int out[]);
  void rdft(int n, int isgn, double *a, int *ip, double *w);
  void mp_mul_i2d(int n, int radix, int nfft, int shift, int in[], double dout[]);
  void mp_mul_cmul(int nfft, double din[], double dinout[]);
  void mp_mul_cmuladd(int nfft, double din1[], double din2[], double dinout[]);
  void mp_mul_d2i(int n, int radix, int nfft, double din[], int out[]);
  int n_h, shift;
  shift = (nfft >> 1) + 1;
  while (n > shift) {
    if (in1[shift + 2] + in2[shift + 2] != 0) {
      break;
    }
    shift++;
  }
  n_h = n / 2 + 1;
  if (n_h < n - shift) {
    n_h = n - shift;
  }
  mp_mul_i2d(n, radix, nfft, 0, in1, tmp1fft);
  rdft(nfft, 1, &tmp1fft[1], ip, w);
  mp_mul_i2d(n, radix, nfft, shift, in2, tmp3fft);
  rdft(nfft, 1, &tmp3fft[1], ip, w);
  mp_mul_cmul(nfft, tmp1fft, tmp3fft);
  mp_mul_i2d(n, radix, nfft, 0, in2, tmp2fft);
  rdft(nfft, 1, &tmp2fft[1], ip, w);
  mp_mul_cmul(nfft, tmp2fft, tmp1fft);
  rdft(nfft, -1, &tmp1fft[1], ip, w);
  mp_mul_d2i(n, radix, nfft, tmp1fft, tmp);
  mp_mul_i2d(n, radix, nfft, shift, in1, tmp1fft);
  rdft(nfft, 1, &tmp1fft[1], ip, w);
  mp_mul_cmuladd(nfft, tmp1fft, tmp2fft, tmp3fft);
  rdft(nfft, -1, &tmp3fft[1], ip, w);
  mp_mul_d2i(n_h, radix, nfft, tmp3fft, out);
  mp_add(n, radix, out, tmp, out);
}
```