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

```asm
<fiat_p256_to_bytes>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  mov    %rdi,%rbx
  mov    $0xff,%edi
  sub    $0x88,%rsp
  mov    0x8(%rsi),%r12d
  mov    0x4(%rsi),%r13d
  mov    0xc(%rsi),%ebp
  mov    (%rsi),%esi
  mov    %esi,0x14(%rsp)
  mov    %ebp,%r15d
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  sar    $0x1f,%r15d
  mov    %eax,%r14d
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x8(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0xc(%rsp)
  call   <UINT8_C@plt>
  mov    0x14(%rsp),%esi
  mov    $0xff,%edi
  mov    %eax,0x10(%rsp)
  mov    %esi,%r11d
  mov    %esi,0x7c(%rsp)
  sar    $0x1f,%r11d
  mov    %r11d,0x78(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x14(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x18(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x1c(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x20(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x24(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x28(%rsp)
  call   <UINT8_C@plt>
  mov    %r13d,%r10d
  mov    $0xff,%edi
  sar    $0x1f,%r10d
  mov    %eax,0x2c(%rsp)
  mov    %r10d,0x74(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x30(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x34(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x38(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x3c(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x40(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x44(%rsp)
  call   <UINT8_C@plt>
  mov    %r12d,%r9d
  mov    $0xff,%edi
  sar    $0x1f,%r9d
  mov    %eax,0x48(%rsp)
  mov    %r9d,0x70(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x4c(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x50(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x54(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x58(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x5c(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x60(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x64(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x68(%rsp)
  call   <UINT8_C@plt>
  mov    $0xff,%edi
  mov    %eax,0x6c(%rsp)
  call   <UINT8_C@plt>
  mov    0x7c(%rsp),%esi
  mov    %r13d,%ecx
  mov    %r12d,%edx
  movslq 0x78(%rsp),%r11
  sar    $0x18,%ecx
  and    0x2c(%rsp),%ecx
  sar    $0x18,%edx
  mov    %esi,%edi
  and    %esi,%r14d
  movslq %ecx,%rcx
  movslq 0x74(%rsp),%r10
  sar    $0x8,%edi
  and    0x8(%rsp),%edi
  mov    %rcx,0x58(%rbx)
  movslq %r14d,%r14
  movslq %edi,%rdi
  mov    0x30(%rsp),%ecx
  mov    %r14,(%rbx)
  movslq %r15d,%r8
  mov    %rdi,0x8(%rbx)
  mov    %esi,%edi
  sar    $0x18,%esi
  and    0x10(%rsp),%esi
  movslq %esi,%rsi
  and    %r10d,%ecx
  sar    $0x10,%edi
  and    0xc(%rsp),%edi
  mov    %rsi,0x18(%rbx)
  mov    0x14(%rsp),%esi
  movslq %ecx,%rcx
  movslq %edi,%rdi
  mov    %rcx,0x60(%rbx)
  mov    0x34(%rsp),%ecx
  and    %r11d,%esi
  mov    %rdi,0x10(%rbx)
  movslq %esi,%rsi
  and    %r10d,%ecx
  mov    %r11,0x38(%rbx)
  mov    %rsi,0x20(%rbx)
  mov    0x18(%rsp),%esi
  movslq %ecx,%rcx
  mov    %rcx,0x68(%rbx)
  mov    0x38(%rsp),%ecx
  and    %r11d,%esi
  mov    %r10,0x78(%rbx)
  movslq %esi,%rsi
  and    %r10d,%ecx
  mov    %rsi,0x28(%rbx)
  mov    0x1c(%rsp),%esi
  movslq %ecx,%rcx
  mov    %rcx,0x70(%rbx)
  and    %r11d,%esi
  movslq %esi,%rsi
  mov    %rsi,0x30(%rbx)
  mov    0x20(%rsp),%esi
  and    %r13d,%esi
  movslq %esi,%rsi
  mov    %rsi,0x40(%rbx)
  mov    %r13d,%esi
  sar    $0x8,%esi
  and    0x24(%rsp),%esi
  movslq %esi,%rsi
  mov    %rsi,0x48(%rbx)
  mov    %r13d,%esi
  sar    $0x10,%esi
  and    0x28(%rsp),%esi
  movslq %esi,%rsi
  mov    %rsi,0x50(%rbx)
  mov    0x3c(%rsp),%ecx
  and    0x48(%rsp),%edx
  movslq 0x70(%rsp),%r9
  mov    %r8,0xf8(%rbx)
  movslq %edx,%rdx
  and    %r12d,%ecx
  mov    0x68(%rsp),%r13d
  mov    %rdx,0x98(%rbx)
  mov    0x4c(%rsp),%edx
  movslq %ecx,%rcx
  mov    %rcx,0x80(%rbx)
  mov    %r12d,%ecx
  and    %r9d,%edx
  sar    $0x8,%ecx
  and    0x40(%rsp),%ecx
  mov    %r9,0xb8(%rbx)
  movslq %edx,%rdx
  movslq %ecx,%rcx
  mov    %rdx,0xa0(%rbx)
  mov    0x50(%rsp),%edx
  mov    %rcx,0x88(%rbx)
  mov    %r12d,%ecx
  mov    0x6c(%rsp),%r12d
  and    %r9d,%edx
  sar    $0x10,%ecx
  and    0x44(%rsp),%ecx
  movslq %edx,%rdx
  movslq %ecx,%rcx
  mov    %rdx,0xa8(%rbx)
  mov    0x54(%rsp),%edx
  mov    %rcx,0x90(%rbx)
  and    %r9d,%edx
  movslq %edx,%rdx
  mov    %rdx,0xb0(%rbx)
  mov    0x58(%rsp),%edx
  and    %ebp,%edx
  movslq %edx,%rdx
  mov    %rdx,0xc0(%rbx)
  mov    %ebp,%edx
  sar    $0x8,%edx
  and    0x5c(%rsp),%edx
  and    %r15d,%r13d
  and    %r15d,%r12d
  movslq %edx,%rdx
  and    %r15d,%eax
  movslq %r13d,%r13
  movslq %r12d,%r12
  mov    %rdx,0xc8(%rbx)
  mov    %ebp,%edx
  sar    $0x18,%ebp
  and    0x64(%rsp),%ebp
  sar    $0x10,%edx
  and    0x60(%rsp),%edx
  movslq %ebp,%rbp
  cltq
  movslq %edx,%rdx
  mov    %r13,0xe0(%rbx)
  mov    %r12,0xe8(%rbx)
  mov    %rdx,0xd0(%rbx)
  mov    %rbp,0xd8(%rbx)
  mov    %rax,0xf0(%rbx)
  add    $0x88,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void fiat_p256_to_bytes(uint8_t out1[32], const uint64_t arg1[4]) {
  uint64_t x1;
  uint64_t x2;
  uint64_t x3;
  uint64_t x4;
  uint8_t x5;
  uint64_t x6;
  uint8_t x7;
  uint64_t x8;
  uint8_t x9;
  uint64_t x10;
  uint8_t x11;
  uint64_t x12;
  uint8_t x13;
  uint64_t x14;
  uint8_t x15;
  uint64_t x16;
  uint8_t x17;
  uint8_t x18;
  uint8_t x19;
  uint64_t x20;
  uint8_t x21;
  uint64_t x22;
  uint8_t x23;
  uint64_t x24;
  uint8_t x25;
  uint64_t x26;
  uint8_t x27;
  uint64_t x28;
  uint8_t x29;
  uint64_t x30;
  uint8_t x31;
  uint8_t x32;
  uint8_t x33;
  uint64_t x34;
  uint8_t x35;
  uint64_t x36;
  uint8_t x37;
  uint64_t x38;
  uint8_t x39;
  uint64_t x40;
  uint8_t x41;
  uint64_t x42;
  uint8_t x43;
  uint64_t x44;
  uint8_t x45;
  uint8_t x46;
  uint8_t x47;
  uint64_t x48;
  uint8_t x49;
  uint64_t x50;
  uint8_t x51;
  uint64_t x52;
  uint8_t x53;
  uint64_t x54;
  uint8_t x55;
  uint64_t x56;
  uint8_t x57;
  uint64_t x58;
  uint8_t x59;
  uint8_t x60;
  x1 = (arg1[3]);
  x2 = (arg1[2]);
  x3 = (arg1[1]);
  x4 = (arg1[0]);
  x5 = (uint8_t)(x4 & UINT8_C(0xff));
  x6 = (x4 >> 8);
  x7 = (uint8_t)(x6 & UINT8_C(0xff));
  x8 = (x6 >> 8);
  x9 = (uint8_t)(x8 & UINT8_C(0xff));
  x10 = (x8 >> 8);
  x11 = (uint8_t)(x10 & UINT8_C(0xff));
  x12 = (x10 >> 8);
  x13 = (uint8_t)(x12 & UINT8_C(0xff));
  x14 = (x12 >> 8);
  x15 = (uint8_t)(x14 & UINT8_C(0xff));
  x16 = (x14 >> 8);
  x17 = (uint8_t)(x16 & UINT8_C(0xff));
  x18 = (uint8_t)(x16 >> 8);
  x19 = (uint8_t)(x3 & UINT8_C(0xff));
  x20 = (x3 >> 8);
  x21 = (uint8_t)(x20 & UINT8_C(0xff));
  x22 = (x20 >> 8);
  x23 = (uint8_t)(x22 & UINT8_C(0xff));
  x24 = (x22 >> 8);
  x25 = (uint8_t)(x24 & UINT8_C(0xff));
  x26 = (x24 >> 8);
  x27 = (uint8_t)(x26 & UINT8_C(0xff));
  x28 = (x26 >> 8);
  x29 = (uint8_t)(x28 & UINT8_C(0xff));
  x30 = (x28 >> 8);
  x31 = (uint8_t)(x30 & UINT8_C(0xff));
  x32 = (uint8_t)(x30 >> 8);
  x33 = (uint8_t)(x2 & UINT8_C(0xff));
  x34 = (x2 >> 8);
  x35 = (uint8_t)(x34 & UINT8_C(0xff));
  x36 = (x34 >> 8);
  x37 = (uint8_t)(x36 & UINT8_C(0xff));
  x38 = (x36 >> 8);
  x39 = (uint8_t)(x38 & UINT8_C(0xff));
  x40 = (x38 >> 8);
  x41 = (uint8_t)(x40 & UINT8_C(0xff));
  x42 = (x40 >> 8);
  x43 = (uint8_t)(x42 & UINT8_C(0xff));
  x44 = (x42 >> 8);
  x45 = (uint8_t)(x44 & UINT8_C(0xff));
  x46 = (uint8_t)(x44 >> 8);
  x47 = (uint8_t)(x1 & UINT8_C(0xff));
  x48 = (x1 >> 8);
  x49 = (uint8_t)(x48 & UINT8_C(0xff));
  x50 = (x48 >> 8);
  x51 = (uint8_t)(x50 & UINT8_C(0xff));
  x52 = (x50 >> 8);
  x53 = (uint8_t)(x52 & UINT8_C(0xff));
  x54 = (x52 >> 8);
  x55 = (uint8_t)(x54 & UINT8_C(0xff));
  x56 = (x54 >> 8);
  x57 = (uint8_t)(x56 & UINT8_C(0xff));
  x58 = (x56 >> 8);
  x59 = (uint8_t)(x58 & UINT8_C(0xff));
  x60 = (uint8_t)(x58 >> 8);
  out1[0] = x5;
  out1[1] = x7;
  out1[2] = x9;
  out1[3] = x11;
  out1[4] = x13;
  out1[5] = x15;
  out1[6] = x17;
  out1[7] = x18;
  out1[8] = x19;
  out1[9] = x21;
  out1[10] = x23;
  out1[11] = x25;
  out1[12] = x27;
  out1[13] = x29;
  out1[14] = x31;
  out1[15] = x32;
  out1[16] = x33;
  out1[17] = x35;
  out1[18] = x37;
  out1[19] = x39;
  out1[20] = x41;
  out1[21] = x43;
  out1[22] = x45;
  out1[23] = x46;
  out1[24] = x47;
  out1[25] = x49;
  out1[26] = x51;
  out1[27] = x53;
  out1[28] = x55;
  out1[29] = x57;
  out1[30] = x59;
  out1[31] = x60;
}
```