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

```asm
<internal_fiat_p448_sub>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x68,%rsp
  mov    %rdi,%r15
  mov    %rsi,%r13
  mov    %rdx,%r12
  mov    $0x8,%esi
  mov    %r13d,%edi
  call   <_br2_load@plt>
  mov    %rax,0x8(%rsp)
  lea    0x8(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%r14
  lea    0x10(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%rbp
  lea    0x18(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%rbx
  lea    0x20(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x10(%rsp)
  lea    0x28(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x18(%rsp)
  lea    0x30(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x20(%rsp)
  lea    0x38(%r13),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x28(%rsp)
  mov    $0x8,%esi
  mov    %r12d,%edi
  call   <_br2_load@plt>
  mov    %rax,0x30(%rsp)
  lea    0x8(%r12),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x38(%rsp)
  lea    0x10(%r12),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x40(%rsp)
  lea    0x18(%r12),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x48(%rsp)
  lea    0x20(%r12),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x50(%rsp)
  lea    0x28(%r12),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%r13
  lea    0x30(%r12),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x58(%rsp)
  lea    0x38(%r12),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  movabs $0x1fffffffffffffe,%rsi
  add    %rsi,%r14
  sub    0x38(%rsp),%r14
  mov    %r14,0x38(%rsp)
  add    %rsi,%rbp
  sub    0x40(%rsp),%rbp
  add    %rsi,%rbx
  sub    0x48(%rsp),%rbx
  movabs $0x1fffffffffffffc,%rdx
  add    0x10(%rsp),%rdx
  sub    0x50(%rsp),%rdx
  mov    %rdx,0x10(%rsp)
  mov    0x18(%rsp),%rcx
  add    %rsi,%rcx
  mov    %rcx,%r14
  sub    %r13,%r14
  mov    0x20(%rsp),%r13
  add    %rsi,%r13
  sub    0x58(%rsp),%r13
  mov    0x28(%rsp),%r12
  add    %rsi,%r12
  sub    %rax,%r12
  add    0x8(%rsp),%rsi
  sub    0x30(%rsp),%rsi
  mov    $0x8,%edx
  mov    %r15d,%edi
  call   <_br2_store@plt>
  lea    0x8(%r15),%edi
  mov    $0x8,%edx
  mov    0x38(%rsp),%rsi
  call   <_br2_store@plt>
  lea    0x10(%r15),%edi
  mov    $0x8,%edx
  mov    %rbp,%rsi
  call   <_br2_store@plt>
  lea    0x18(%r15),%edi
  mov    $0x8,%edx
  mov    %rbx,%rsi
  call   <_br2_store@plt>
  lea    0x20(%r15),%edi
  mov    $0x8,%edx
  mov    0x10(%rsp),%rsi
  call   <_br2_store@plt>
  lea    0x28(%r15),%edi
  mov    $0x8,%edx
  mov    %r14,%rsi
  call   <_br2_store@plt>
  lea    0x30(%r15),%edi
  mov    $0x8,%edx
  mov    %r13,%rsi
  call   <_br2_store@plt>
  lea    0x38(%r15),%edi
  mov    $0x8,%edx
  mov    %r12,%rsi
  call   <_br2_store@plt>
  add    $0x68,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void internal_fiat_p448_sub(uintptr_t out0, uintptr_t in0, uintptr_t in1) {
  uintptr_t x0, x8, x1, x9, x2, x10, x3, x11, x4, x12, x5, x13, x6, x14, x7, x15, x16, x17, x18, x19, x20, x21, x22, x23, x24, x25, x26, x27, x28, x29, x30, x31;
  x0 = _br2_load((in0) + ((uintptr_t)0ULL), sizeof(uintptr_t));
  x1 = _br2_load((in0) + ((uintptr_t)8ULL), sizeof(uintptr_t));
  x2 = _br2_load((in0) + ((uintptr_t)16ULL), sizeof(uintptr_t));
  x3 = _br2_load((in0) + ((uintptr_t)24ULL), sizeof(uintptr_t));
  x4 = _br2_load((in0) + ((uintptr_t)32ULL), sizeof(uintptr_t));
  x5 = _br2_load((in0) + ((uintptr_t)40ULL), sizeof(uintptr_t));
  x6 = _br2_load((in0) + ((uintptr_t)48ULL), sizeof(uintptr_t));
  x7 = _br2_load((in0) + ((uintptr_t)56ULL), sizeof(uintptr_t));
  x8 = _br2_load((in1) + ((uintptr_t)0ULL), sizeof(uintptr_t));
  x9 = _br2_load((in1) + ((uintptr_t)8ULL), sizeof(uintptr_t));
  x10 = _br2_load((in1) + ((uintptr_t)16ULL), sizeof(uintptr_t));
  x11 = _br2_load((in1) + ((uintptr_t)24ULL), sizeof(uintptr_t));
  x12 = _br2_load((in1) + ((uintptr_t)32ULL), sizeof(uintptr_t));
  x13 = _br2_load((in1) + ((uintptr_t)40ULL), sizeof(uintptr_t));
  x14 = _br2_load((in1) + ((uintptr_t)48ULL), sizeof(uintptr_t));
  x15 = _br2_load((in1) + ((uintptr_t)56ULL), sizeof(uintptr_t));
  x16 = (((uintptr_t)144115188075855870ULL) + (x0)) - (x8);
  x17 = (((uintptr_t)144115188075855870ULL) + (x1)) - (x9);
  x18 = (((uintptr_t)144115188075855870ULL) + (x2)) - (x10);
  x19 = (((uintptr_t)144115188075855870ULL) + (x3)) - (x11);
  x20 = (((uintptr_t)144115188075855868ULL) + (x4)) - (x12);
  x21 = (((uintptr_t)144115188075855870ULL) + (x5)) - (x13);
  x22 = (((uintptr_t)144115188075855870ULL) + (x6)) - (x14);
  x23 = (((uintptr_t)144115188075855870ULL) + (x7)) - (x15);
  x24 = x16;
  x25 = x17;
  x26 = x18;
  x27 = x19;
  x28 = x20;
  x29 = x21;
  x30 = x22;
  x31 = x23;
  _br2_store((out0) + ((uintptr_t)0ULL), x24, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)8ULL), x25, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)16ULL), x26, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)24ULL), x27, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)32ULL), x28, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)40ULL), x29, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)48ULL), x30, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)56ULL), x31, sizeof(uintptr_t));
  return;
}
```