user: Converte this assembly snippet into its equivalent C code:

```asm
<longest_palindrome_try_all>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  mov    %rdi,%rbp
  push   %rbx
  sub    $0x18,%rsp
  call   <strlen@plt>
  movl   $0x0,0xc(%rsp)
  mov    %eax,%r15d
  test   %eax,%eax
  js     L37
L219:
  xor    %ebx,%ebx
  lea    -0x1(%r15),%r12d
  jmp    L168
  nopl   (%rax)
L6:
  add    $0x1,%ebx
  cmp    0xc(%rsp),%ebx
  jg     L18
L168:
  lea    (%r12,%rbx,1),%edx
  mov    %ebx,%esi
  mov    %rbp,%rdi
  mov    %r15d,%r14d
  lea    (%r15,%rbx,1),%r13d
  call   <is_palindrome@plt>
  test   %rax,%rax
  je     L6
  lea    0x1(%r15),%edi
  mov    $0x1,%esi
  call   <calloc@plt>
  mov    %rax,%rdx
  mov    %rax,%r8
  cmp    %r13d,%ebx
  jge    L208
  movslq %ebx,%rdi
  lea    0x1(%rbp,%rdi,1),%rsi
  sub    %rsi,%rax
  cmp    $0xe,%rax
  jbe    L23
  cmp    $0x6,%r12d
  jbe    L23
  cmp    $0xe,%r12d
  jbe    L198
  mov    %r15d,%esi
  mov    %rdi,%r9
  mov    %rdx,%rax
  shr    $0x4,%esi
  sub    %rdx,%r9
  shl    $0x4,%rsi
  add    %rbp,%r9
  add    %rdx,%rsi
  xchg   %ax,%ax
L102:
  movdqu (%rax,%r9,1),%xmm0
  add    $0x10,%rax
  movups %xmm0,-0x10(%rax)
  cmp    %rax,%rsi
  jne    L102
  mov    %r15d,%eax
  and    $0xfffffff0,%eax
  mov    %eax,%esi
  add    %eax,%ebx
  cmp    %r15d,%eax
  je     L208
  mov    %r15d,%r14d
  sub    %eax,%r14d
  lea    -0x1(%r14),%ecx
  cmp    $0x6,%ecx
  jbe    L91
L209:
  add    %rbp,%rdi
  mov    (%rdi,%rax,1),%rcx
  mov    %rcx,(%rdx,%rax,1)
  mov    %r14d,%eax
  and    $0xfffffff8,%eax
  add    %eax,%esi
  add    %eax,%ebx
  cmp    %eax,%r14d
  je     L208
L91:
  movslq %ebx,%rax
  lea    0x1(%rsi),%ecx
  movzbl 0x0(%rbp,%rax,1),%edi
  movslq %esi,%rax
  mov    %dil,(%rdx,%rax,1)
  lea    0x1(%rbx),%eax
  cmp    %r13d,%eax
  jge    L208
  cltq
  movslq %ecx,%rcx
  lea    0x2(%rsi),%edi
  movzbl 0x0(%rbp,%rax,1),%eax
  mov    %al,(%rdx,%rcx,1)
  lea    0x2(%rbx),%eax
  cmp    %r13d,%eax
  jge    L208
  cltq
  movslq %edi,%rdi
  lea    0x3(%rsi),%ecx
  movzbl 0x0(%rbp,%rax,1),%eax
  mov    %al,(%rdx,%rdi,1)
  lea    0x3(%rbx),%eax
  cmp    %r13d,%eax
  jge    L208
  cltq
  movslq %ecx,%rcx
  lea    0x4(%rsi),%edi
  movzbl 0x0(%rbp,%rax,1),%eax
  mov    %al,(%rdx,%rcx,1)
  lea    0x4(%rbx),%eax
  cmp    %r13d,%eax
  jge    L208
  cltq
  movslq %edi,%rdi
  lea    0x5(%rsi),%ecx
  movzbl 0x0(%rbp,%rax,1),%eax
  mov    %al,(%rdx,%rdi,1)
  lea    0x5(%rbx),%eax
  cmp    %eax,%r13d
  jle    L208
  cltq
  movslq %ecx,%rcx
  add    $0x6,%ebx
  add    $0x6,%esi
  movzbl 0x0(%rbp,%rax,1),%eax
  mov    %al,(%rdx,%rcx,1)
  cmp    %ebx,%r13d
  jle    L208
  movslq %ebx,%rbx
  movslq %esi,%rsi
  movzbl 0x0(%rbp,%rbx,1),%eax
  mov    %al,(%rdx,%rsi,1)
L208:
  add    $0x18,%rsp
  mov    %r8,%rax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L18:
  addl   $0x1,0xc(%rsp)
  mov    %r12d,%r15d
  cmp    $0xffffffff,%r12d
  jne    L219
L37:
  xor    %r8d,%r8d
  jmp    L208
L23:
  sub    %rdx,%rdi
  lea    0x1(%rdx,%r12,1),%rcx
  add    %rdi,%rbp
  nopw   0x0(%rax,%rax,1)
L35:
  movzbl 0x0(%rbp,%rdx,1),%eax
  add    $0x1,%rdx
  mov    %al,-0x1(%rdx)
  cmp    %rcx,%rdx
  jne    L35
  jmp    L208
L198:
  xor    %eax,%eax
  xor    %esi,%esi
  jmp    L209
```

assistant: ```c
char *longest_palindrome_try_all(char *s) {
  int len = strlen(s);
  for (int c = len; c >= 0; c--) {
    for (int sub = 0; sub <= (len - c); sub++) {
      if (is_palindrome(s, sub, sub + c - 1)) {
        char *out = (char *)calloc(c + 1, sizeof(char));
        int m = 0;
        for (int n = sub; n < sub + c; n++)
          out[m++] = s[n];
        return out;
      }
    }
  }
  return NULL;
}
```