user: 请将这段汇编代码片段转换成等效的C代码:

```asm
<salsa20_wordtobyte>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x98,%rsp
  mov    %rdi,0x30(%rsp)
  mov    %rsi,%r15
  mov    %fs:0x28,%rax
  mov    %rax,0x88(%rsp)
  xor    %eax,%eax
L0:
  mov    (%r15,%rax,1),%edx
  mov    %edx,0x40(%rsp,%rax,1)
  add    $0x4,%rax
  cmp    $0x40,%rax
  jne    L0
  movl   $0xa,0x2c(%rsp)
  mov    %r15,0x38(%rsp)
L35:
  mov    0x50(%rsp),%ebx
  mov    %ebx,%r13d
  add    0x40(%rsp),%r13d
  mov    %r13d,%edi
  xor    0x70(%rsp),%edi
  mov    $0x10,%esi
  call   <rotl@plt>
  mov    %eax,%r12d
  mov    %eax,%ebp
  add    0x60(%rsp),%ebp
  xor    %ebp,%ebx
  mov    %ebx,%edi
  mov    $0xc,%esi
  call   <rotl@plt>
  mov    %eax,%ebx
  add    %eax,%r13d
  mov    %r12d,%edi
  xor    %r13d,%edi
  mov    $0x8,%esi
  call   <rotl@plt>
  mov    %eax,(%rsp)
  add    %eax,%ebp
  mov    %ebp,0x4(%rsp)
  xor    %ebp,%ebx
  mov    %ebx,%edi
  mov    $0x7,%esi
  call   <rotl@plt>
  mov    %eax,0x24(%rsp)
  mov    0x54(%rsp),%ebx
  mov    %ebx,%r14d
  add    0x44(%rsp),%r14d
  mov    %r14d,%edx
  xor    0x74(%rsp),%edx
  mov    %edx,%edi
  mov    $0x10,%esi
  call   <rotl@plt>
  mov    %eax,%ebp
  mov    %eax,%r12d
  add    0x64(%rsp),%r12d
  xor    %r12d,%ebx
  mov    %ebx,%edi
  mov    $0xc,%esi
  call   <rotl@plt>
  mov    %eax,%ebx
  lea    (%r14,%rax,1),%edx
  mov    %ebp,%esi
  mov    %edx,0x8(%rsp)
  xor    %edx,%esi
  mov    %esi,%edi
  mov    $0x8,%esi
  call   <rotl@plt>
  mov    %eax,0xc(%rsp)
  add    %eax,%r12d
  mov    %r12d,0x10(%rsp)
  xor    %r12d,%ebx
  mov    %ebx,%edi
  mov    $0x7,%esi
  call   <rotl@plt>
  mov    %eax,0x14(%rsp)
  mov    0x58(%rsp),%ebx
  mov    %ebx,%r14d
  add    0x48(%rsp),%r14d
  mov    %r14d,%r9d
  xor    0x78(%rsp),%r9d
  mov    %r9d,%edi
  mov    $0x10,%esi
  call   <rotl@plt>
  mov    %eax,%ebp
  mov    %eax,%r10d
  add    0x68(%rsp),%r10d
  mov    %r10d,%r12d
  xor    %r10d,%ebx
  mov    %ebx,%edi
  mov    $0xc,%esi
  call   <rotl@plt>
  mov    %eax,%ebx
  lea    (%r14,%rax,1),%r11d
  mov    %ebp,%r8d
  mov    %r11d,0x18(%rsp)
  xor    %r11d,%r8d
  mov    %r8d,%edi
  mov    $0x8,%esi
  call   <rotl@plt>
  mov    %eax,0x1c(%rsp)
  add    %eax,%r12d
  xor    %r12d,%ebx
  mov    %ebx,%edi
  mov    $0x7,%esi
  call   <rotl@plt>
  mov    %eax,0x28(%rsp)
  mov    0x5c(%rsp),%r15d
  mov    %r15d,%ebx
  add    0x4c(%rsp),%ebx
  mov    %ebx,%r9d
  xor    0x7c(%rsp),%r9d
  mov    %r9d,%edi
  mov    $0x10,%esi
  call   <rotl@plt>
  mov    %eax,%r14d
  mov    %eax,%r10d
  add    0x6c(%rsp),%r10d
  mov    %r10d,%ebp
  mov    %r15d,%r9d
  xor    %r10d,%r9d
  mov    %r9d,%edi
  mov    $0xc,%esi
  call   <rotl@plt>
  mov    %eax,%r15d
  add    %eax,%ebx
  mov    %r14d,%r10d
  xor    %ebx,%r10d
  mov    %r10d,%edi
  mov    $0x8,%esi
  call   <rotl@plt>
  mov    %eax,%r14d
  add    %eax,%ebp
  mov    %r15d,%r9d
  xor    %ebp,%r9d
  mov    %r9d,%edi
  mov    $0x7,%esi
  call   <rotl@plt>
  mov    %eax,%r15d
  add    0x14(%rsp),%r13d
  mov    %r14d,%r10d
  xor    %r13d,%r10d
  mov    %r10d,%edi
  mov    $0x10,%esi
  call   <rotl@plt>
  mov    %eax,0x20(%rsp)
  add    %eax,%r12d
  mov    0x14(%rsp),%edi
  xor    %r12d,%edi
  mov    $0xc,%esi
  call   <rotl@plt>
  mov    %eax,%r14d
  add    %eax,%r13d
  mov    %r13d,0x40(%rsp)
  mov    0x20(%rsp),%edi
  xor    %r13d,%edi
  mov    $0x8,%esi
  call   <rotl@plt>
  mov    %eax,0x7c(%rsp)
  add    %eax,%r12d
  mov    %r12d,0x68(%rsp)
  mov    %r14d,%r9d
  xor    %r12d,%r9d
  mov    %r9d,%edi
  mov    $0x7,%esi
  call   <rotl@plt>
  mov    %eax,0x54(%rsp)
  mov    0x8(%rsp),%r13d
  mov    0x28(%rsp),%r14d
  add    %r14d,%r13d
  mov    (%rsp),%edi
  xor    %r13d,%edi
  mov    $0x10,%esi
  call   <rotl@plt>
  mov    %eax,%r12d
  add    %eax,%ebp
  mov    %r14d,%edi
  xor    %ebp,%edi
  mov    $0xc,%esi
  call   <rotl@plt>
  mov    %eax,%r14d
  add    %eax,%r13d
  mov    %r13d,0x44(%rsp)
  mov    %r12d,%edx
  xor    %r13d,%edx
  mov    %edx,%edi
  mov    $0x8,%esi
  call   <rotl@plt>
  mov    %eax,0x70(%rsp)
  add    %eax,%ebp
  mov    %ebp,0x6c(%rsp)
  xor    %ebp,%r14d
  mov    %r14d,%edi
  mov    $0x7,%esi
  call   <rotl@plt>
  mov    %eax,0x58(%rsp)
  mov    0x18(%rsp),%r11d
  lea    (%r11,%r15,1),%r12d
  mov    0xc(%rsp),%edi
  xor    %r12d,%edi
  mov    $0x10,%esi
  call   <rotl@plt>
  mov    %eax,%ebp
  mov    0x4(%rsp),%ecx
  lea    (%rcx,%rax,1),%r13d
  mov    %r15d,%ecx
  xor    %r13d,%ecx
  mov    %ecx,%edi
  mov    $0xc,%esi
  call   <rotl@plt>
  mov    %eax,%r14d
  add    %eax,%r12d
  mov    %r12d,0x48(%rsp)
  xor    %r12d,%ebp
  mov    %ebp,%edi
  mov    $0x8,%esi
  call   <rotl@plt>
  mov    %eax,0x74(%rsp)
  add    %eax,%r13d
  mov    %r13d,0x60(%rsp)
  xor    %r13d,%r14d
  mov    %r14d,%edi
  mov    $0x7,%esi
  call   <rotl@plt>
  mov    %eax,0x5c(%rsp)
  mov    0x24(%rsp),%r15d
  add    %r15d,%ebx
  mov    0x1c(%rsp),%edi
  xor    %ebx,%edi
  mov    $0x10,%esi
  call   <rotl@plt>
  mov    %eax,%ebp
  mov    0x10(%rsp),%r12d
  add    %eax,%r12d
  mov    %r15d,%edi
  xor    %r12d,%edi
  mov    $0xc,%esi
  call   <rotl@plt>
  mov    %eax,%r13d
  add    %eax,%ebx
  mov    %ebx,0x4c(%rsp)
  mov    %ebp,%edi
  xor    %ebx,%edi
  mov    $0x8,%esi
  call   <rotl@plt>
  mov    %eax,0x78(%rsp)
  add    %eax,%r12d
  mov    %r12d,0x64(%rsp)
  mov    %r13d,%edi
  xor    %r12d,%edi
  mov    $0x7,%esi
  call   <rotl@plt>
  mov    %eax,0x50(%rsp)
  subl   $0x1,0x2c(%rsp)
  jne    L35
  mov    0x38(%rsp),%r15
  lea    0x40(%rsp),%rbx
  mov    %r15,%rdx
  lea    0x80(%rsp),%r12
  mov    %rbx,%rax
L32:
  mov    (%rdx),%ecx
  add    %ecx,(%rax)
  add    $0x4,%rax
  add    $0x4,%rdx
  cmp    %r12,%rax
  jne    L32
  mov    0x30(%rsp),%rbp
L20:
  mov    (%rbx),%esi
  mov    %rbp,%rdi
  call   <write32le@plt>
  add    $0x4,%rbx
  add    $0x4,%rbp
  cmp    %r12,%rbx
  jne    L20
  mov    0x88(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L18
  add    $0x98,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L18:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
void salsa20_wordtobyte(unsigned char output[64], const uint32_t input[16]) {
  uint32_t i, x[16];
  for (i = 0; i < 16; ++i)
    x[i] = input[i];
  for (i = 20; i != 0; i -= 2) {
    x[0] += x[4];
    x[12] = rotl(x[12] ^ x[0], 16);
    x[8] += x[12];
    x[4] = rotl(x[4] ^ x[8], 12);
    x[0] += x[4];
    x[12] = rotl(x[12] ^ x[0], 8);
    x[8] += x[12];
    x[4] = rotl(x[4] ^ x[8], 7);
    x[1] += x[5];
    x[13] = rotl(x[13] ^ x[1], 16);
    x[9] += x[13];
    x[5] = rotl(x[5] ^ x[9], 12);
    x[1] += x[5];
    x[13] = rotl(x[13] ^ x[1], 8);
    x[9] += x[13];
    x[5] = rotl(x[5] ^ x[9], 7);
    x[2] += x[6];
    x[14] = rotl(x[14] ^ x[2], 16);
    x[10] += x[14];
    x[6] = rotl(x[6] ^ x[10], 12);
    x[2] += x[6];
    x[14] = rotl(x[14] ^ x[2], 8);
    x[10] += x[14];
    x[6] = rotl(x[6] ^ x[10], 7);
    x[3] += x[7];
    x[15] = rotl(x[15] ^ x[3], 16);
    x[11] += x[15];
    x[7] = rotl(x[7] ^ x[11], 12);
    x[3] += x[7];
    x[15] = rotl(x[15] ^ x[3], 8);
    x[11] += x[15];
    x[7] = rotl(x[7] ^ x[11], 7);
    x[0] += x[5];
    x[15] = rotl(x[15] ^ x[0], 16);
    x[10] += x[15];
    x[5] = rotl(x[5] ^ x[10], 12);
    x[0] += x[5];
    x[15] = rotl(x[15] ^ x[0], 8);
    x[10] += x[15];
    x[5] = rotl(x[5] ^ x[10], 7);
    x[1] += x[6];
    x[12] = rotl(x[12] ^ x[1], 16);
    x[11] += x[12];
    x[6] = rotl(x[6] ^ x[11], 12);
    x[1] += x[6];
    x[12] = rotl(x[12] ^ x[1], 8);
    x[11] += x[12];
    x[6] = rotl(x[6] ^ x[11], 7);
    x[2] += x[7];
    x[13] = rotl(x[13] ^ x[2], 16);
    x[8] += x[13];
    x[7] = rotl(x[7] ^ x[8], 12);
    x[2] += x[7];
    x[13] = rotl(x[13] ^ x[2], 8);
    x[8] += x[13];
    x[7] = rotl(x[7] ^ x[8], 7);
    x[3] += x[4];
    x[14] = rotl(x[14] ^ x[3], 16);
    x[9] += x[14];
    x[4] = rotl(x[4] ^ x[9], 12);
    x[3] += x[4];
    x[14] = rotl(x[14] ^ x[3], 8);
    x[9] += x[14];
    x[4] = rotl(x[4] ^ x[9], 7);
  }
  for (i = 0; i < 16; ++i)
    x[i] += input[i];
  for (i = 0; i < 16; ++i)
    write32le((uint32_t *)(output + 4 * i), x[i]);
}
```