user: What is the c source code of the assembly code below?

```asm
<internal_fiat_p434_selectznz>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x58,%rsp
  mov    %rdi,(%rsp)
  mov    %rsi,%r14
  mov    %rdx,%rbx
  mov    %rcx,%r13
  mov    $0x8,%esi
  mov    %edx,%edi
  call   <_br2_load@plt>
  mov    %rax,0x8(%rsp)
  lea    0x8(%rbx),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x10(%rsp)
  lea    0x10(%rbx),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x18(%rsp)
  lea    0x18(%rbx),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x20(%rsp)
  lea    0x20(%rbx),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x28(%rsp)
  lea    0x28(%rbx),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x30(%rsp)
  lea    0x30(%rbx),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x38(%rsp)
  mov    $0x8,%esi
  mov    %r13d,%edi
  call   <_br2_load@plt>
  mov    %rax,0x40(%rsp)
  lea    0x8(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%r12
  lea    0x10(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%r15
  lea    0x18(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x48(%rsp)
  lea    0x20(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%rbp
  lea    0x28(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%rbx
  lea    0x30(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%r13
  neg    %r14
  sbb    %rax,%rax
  mov    0x10(%rsp),%rcx
  xor    %rcx,%r12
  and    %rax,%r12
  xor    %rcx,%r12
  mov    0x18(%rsp),%r11
  xor    %r11,%r15
  and    %rax,%r15
  xor    %r11,%r15
  mov    0x48(%rsp),%r14
  mov    0x20(%rsp),%r10
  xor    %r10,%r14
  and    %rax,%r14
  xor    %r10,%r14
  mov    0x28(%rsp),%r9
  xor    %r9,%rbp
  and    %rax,%rbp
  xor    %r9,%rbp
  mov    0x30(%rsp),%r8
  xor    %r8,%rbx
  and    %rax,%rbx
  xor    %r8,%rbx
  mov    0x38(%rsp),%rdx
  xor    %rdx,%r13
  and    %rax,%r13
  xor    %rdx,%r13
  mov    0x40(%rsp),%rsi
  mov    0x8(%rsp),%rcx
  xor    %rcx,%rsi
  and    %rax,%rsi
  xor    %rcx,%rsi
  mov    $0x8,%edx
  mov    (%rsp),%edi
  call   <_br2_store@plt>
  mov    (%rsp),%eax
  lea    0x8(%rax),%edi
  mov    $0x8,%edx
  mov    %r12,%rsi
  call   <_br2_store@plt>
  mov    (%rsp),%r12
  lea    0x10(%r12),%edi
  mov    $0x8,%edx
  mov    %r15,%rsi
  call   <_br2_store@plt>
  lea    0x18(%r12),%edi
  mov    $0x8,%edx
  mov    %r14,%rsi
  call   <_br2_store@plt>
  lea    0x20(%r12),%edi
  mov    $0x8,%edx
  mov    %rbp,%rsi
  call   <_br2_store@plt>
  lea    0x28(%r12),%edi
  mov    $0x8,%edx
  mov    %rbx,%rsi
  call   <_br2_store@plt>
  mov    %r12d,%edi
  add    $0x30,%edi
  mov    $0x8,%edx
  mov    %r13,%rsi
  call   <_br2_store@plt>
  add    $0x58,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void internal_fiat_p434_selectznz(uintptr_t out0, uintptr_t in0, uintptr_t in1, uintptr_t in2) {
  uintptr_t x7, x14, x0, x15, x8, x17, x1, x18, x9, x20, x2, x21, x10, x23, x3, x24, x11, x26, x4, x27, x12, x29, x5, x30, x13, x32, x6, x33, x16, x19, x22, x25, x28, x31, x34, x35, x36, x37, x38, x39, x40, x41;
  x0 = _br2_load((in1) + ((uintptr_t)0ULL), sizeof(uintptr_t));
  x1 = _br2_load((in1) + ((uintptr_t)8ULL), sizeof(uintptr_t));
  x2 = _br2_load((in1) + ((uintptr_t)16ULL), sizeof(uintptr_t));
  x3 = _br2_load((in1) + ((uintptr_t)24ULL), sizeof(uintptr_t));
  x4 = _br2_load((in1) + ((uintptr_t)32ULL), sizeof(uintptr_t));
  x5 = _br2_load((in1) + ((uintptr_t)40ULL), sizeof(uintptr_t));
  x6 = _br2_load((in1) + ((uintptr_t)48ULL), sizeof(uintptr_t));
  x7 = _br2_load((in2) + ((uintptr_t)0ULL), sizeof(uintptr_t));
  x8 = _br2_load((in2) + ((uintptr_t)8ULL), sizeof(uintptr_t));
  x9 = _br2_load((in2) + ((uintptr_t)16ULL), sizeof(uintptr_t));
  x10 = _br2_load((in2) + ((uintptr_t)24ULL), sizeof(uintptr_t));
  x11 = _br2_load((in2) + ((uintptr_t)32ULL), sizeof(uintptr_t));
  x12 = _br2_load((in2) + ((uintptr_t)40ULL), sizeof(uintptr_t));
  x13 = _br2_load((in2) + ((uintptr_t)48ULL), sizeof(uintptr_t));
  x14 = ((uintptr_t)-1ULL) + ((in0) == ((uintptr_t)0ULL));
  x15 = (x14) ^ ((uintptr_t)18446744073709551615ULL);
  x16 = ((x7) & (x14)) | ((x0) & (x15));
  x17 = ((uintptr_t)-1ULL) + ((in0) == ((uintptr_t)0ULL));
  x18 = (x17) ^ ((uintptr_t)18446744073709551615ULL);
  x19 = ((x8) & (x17)) | ((x1) & (x18));
  x20 = ((uintptr_t)-1ULL) + ((in0) == ((uintptr_t)0ULL));
  x21 = (x20) ^ ((uintptr_t)18446744073709551615ULL);
  x22 = ((x9) & (x20)) | ((x2) & (x21));
  x23 = ((uintptr_t)-1ULL) + ((in0) == ((uintptr_t)0ULL));
  x24 = (x23) ^ ((uintptr_t)18446744073709551615ULL);
  x25 = ((x10) & (x23)) | ((x3) & (x24));
  x26 = ((uintptr_t)-1ULL) + ((in0) == ((uintptr_t)0ULL));
  x27 = (x26) ^ ((uintptr_t)18446744073709551615ULL);
  x28 = ((x11) & (x26)) | ((x4) & (x27));
  x29 = ((uintptr_t)-1ULL) + ((in0) == ((uintptr_t)0ULL));
  x30 = (x29) ^ ((uintptr_t)18446744073709551615ULL);
  x31 = ((x12) & (x29)) | ((x5) & (x30));
  x32 = ((uintptr_t)-1ULL) + ((in0) == ((uintptr_t)0ULL));
  x33 = (x32) ^ ((uintptr_t)18446744073709551615ULL);
  x34 = ((x13) & (x32)) | ((x6) & (x33));
  x35 = x16;
  x36 = x19;
  x37 = x22;
  x38 = x25;
  x39 = x28;
  x40 = x31;
  x41 = x34;
  _br2_store((out0) + ((uintptr_t)0ULL), x35, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)8ULL), x36, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)16ULL), x37, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)24ULL), x38, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)32ULL), x39, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)40ULL), x40, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)48ULL), x41, sizeof(uintptr_t));
  return;
}
```