user: Demonstrate the C code that generates the assembly output below:

```asm
<internal_fiat_p521_carry>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x28,%rsp
  mov    %rdi,%rbx
  mov    %rsi,%rbp
  mov    $0x8,%esi
  mov    %ebp,%edi
  call   <_br2_load@plt>
  mov    %rax,%r15
  lea    0x8(%rbp),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%r14
  lea    0x10(%rbp),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%r13
  lea    0x18(%rbp),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%r12
  lea    0x20(%rbp),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,(%rsp)
  lea    0x28(%rbp),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x8(%rsp)
  lea    0x30(%rbp),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x10(%rsp)
  lea    0x38(%rbp),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,0x18(%rsp)
  lea    0x40(%rbp),%edi
  mov    $0x8,%esi
  call   <_br2_load@plt>
  mov    %rax,%rcx
  mov    %r15,%rdx
  shr    $0x3a,%rdx
  add    %r14,%rdx
  mov    %rdx,%rsi
  shr    $0x3a,%rsi
  mov    %rsi,%rax
  add    %r13,%rax
  mov    %rax,%r14
  shr    $0x3a,%r14
  add    %r12,%r14
  mov    %r14,%r13
  shr    $0x3a,%r13
  add    (%rsp),%r13
  mov    %r13,%r12
  shr    $0x3a,%r12
  add    0x8(%rsp),%r12
  mov    %r12,%rsi
  shr    $0x3a,%rsi
  add    0x10(%rsp),%rsi
  mov    %rsi,(%rsp)
  shr    $0x3a,%rsi
  mov    %rsi,%rdi
  add    0x18(%rsp),%rdi
  mov    %rdi,0x8(%rsp)
  mov    %rdi,%r8
  shr    $0x3a,%r8
  add    %r8,%rcx
  movabs $0x3ffffffffffffff,%rbp
  and    %rbp,%r15
  mov    %rcx,0x10(%rsp)
  shr    $0x39,%rcx
  lea    (%r15,%rcx,1),%rsi
  mov    %rsi,%r15
  shr    $0x3a,%r15
  and    %rbp,%rdx
  add    %rdx,%r15
  mov    %r15,%rdx
  shr    $0x3a,%rdx
  and    %rbp,%rax
  add    %rdx,%rax
  mov    %rax,0x18(%rsp)
  and    %rbp,%rsi
  mov    $0x8,%edx
  mov    %ebx,%edi
  call   <_br2_store@plt>
  and    %rbp,%r15
  mov    %r15,%rsi
  lea    0x8(%rbx),%edi
  mov    $0x8,%edx
  call   <_br2_store@plt>
  lea    0x10(%rbx),%edi
  mov    $0x8,%edx
  mov    0x18(%rsp),%rsi
  call   <_br2_store@plt>
  and    %rbp,%r14
  mov    %r14,%rsi
  lea    0x18(%rbx),%edi
  mov    $0x8,%edx
  call   <_br2_store@plt>
  and    %rbp,%r13
  mov    %r13,%rsi
  lea    0x20(%rbx),%edi
  mov    $0x8,%edx
  call   <_br2_store@plt>
  and    %rbp,%r12
  mov    %r12,%rsi
  lea    0x28(%rbx),%edi
  mov    $0x8,%edx
  call   <_br2_store@plt>
  mov    (%rsp),%rsi
  and    %rbp,%rsi
  lea    0x30(%rbx),%edi
  mov    $0x8,%edx
  call   <_br2_store@plt>
  mov    0x8(%rsp),%rsi
  and    %rbp,%rsi
  lea    0x38(%rbx),%edi
  mov    $0x8,%edx
  call   <_br2_store@plt>
  movabs $0x1ffffffffffffff,%rax
  mov    0x10(%rsp),%rcx
  and    %rax,%rcx
  mov    %rcx,%rsi
  lea    0x40(%rbx),%edi
  mov    $0x8,%edx
  call   <_br2_store@plt>
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void internal_fiat_p521_carry(uintptr_t out0, uintptr_t in0) {
  uintptr_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x18, x19, x11, x12, x13, x14, x15, x16, x17, x20, x21, x22, x23, x24, x25, x26, x27, x28, x29, x30, x31, x32, x33, x34, x35, x36, x37;
  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((in0) + ((uintptr_t)64ULL), sizeof(uintptr_t));
  x9 = x0;
  x10 = ((x9) >> ((uintptr_t)58ULL)) + (x1);
  x11 = ((x10) >> ((uintptr_t)58ULL)) + (x2);
  x12 = ((x11) >> ((uintptr_t)58ULL)) + (x3);
  x13 = ((x12) >> ((uintptr_t)58ULL)) + (x4);
  x14 = ((x13) >> ((uintptr_t)58ULL)) + (x5);
  x15 = ((x14) >> ((uintptr_t)58ULL)) + (x6);
  x16 = ((x15) >> ((uintptr_t)58ULL)) + (x7);
  x17 = ((x16) >> ((uintptr_t)58ULL)) + (x8);
  x18 = ((x9) & ((uintptr_t)288230376151711743ULL)) + ((x17) >> ((uintptr_t)57ULL));
  x19 = ((x18) >> ((uintptr_t)58ULL)) + ((x10) & ((uintptr_t)288230376151711743ULL));
  x20 = (x18) & ((uintptr_t)288230376151711743ULL);
  x21 = (x19) & ((uintptr_t)288230376151711743ULL);
  x22 = ((x19) >> ((uintptr_t)58ULL)) + ((x11) & ((uintptr_t)288230376151711743ULL));
  x23 = (x12) & ((uintptr_t)288230376151711743ULL);
  x24 = (x13) & ((uintptr_t)288230376151711743ULL);
  x25 = (x14) & ((uintptr_t)288230376151711743ULL);
  x26 = (x15) & ((uintptr_t)288230376151711743ULL);
  x27 = (x16) & ((uintptr_t)288230376151711743ULL);
  x28 = (x17) & ((uintptr_t)144115188075855871ULL);
  x29 = x20;
  x30 = x21;
  x31 = x22;
  x32 = x23;
  x33 = x24;
  x34 = x25;
  x35 = x26;
  x36 = x27;
  x37 = x28;
  _br2_store((out0) + ((uintptr_t)0ULL), x29, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)8ULL), x30, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)16ULL), x31, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)24ULL), x32, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)32ULL), x33, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)40ULL), x34, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)48ULL), x35, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)56ULL), x36, sizeof(uintptr_t));
  _br2_store((out0) + ((uintptr_t)64ULL), x37, sizeof(uintptr_t));
  return;
}
```