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

```asm
<my_strcat>:
  endbr64
  push   %r13
  mov    %rcx,%r13
  push   %r12
  mov    %rsi,%r12
  mov    $0x1,%esi
  push   %rbp
  mov    %edx,%ebp
  push   %rbx
  mov    %edi,%ebx
  lea    0x1(%rdi,%rdx,1),%edi
  sub    $0x8,%rsp
  call   <calloc@plt>
  mov    %rax,%r8
  test   %ebx,%ebx
  jle    L88
  lea    0x1(%r12),%rsi
  mov    %r8,%rdx
  lea    -0x1(%rbx),%eax
  mov    %ebx,%ecx
  sub    %rsi,%rdx
  cmp    $0xe,%rdx
  jbe    L240
  cmp    $0x6,%eax
  jbe    L240
  cmp    $0xe,%eax
  jbe    L65
  mov    %ebx,%edx
  xor    %eax,%eax
  shr    $0x4,%edx
  shl    $0x4,%rdx
  nopl   0x0(%rax,%rax,1)
L131:
  movdqu (%r12,%rax,1),%xmm0
  movups %xmm0,(%r8,%rax,1)
  add    $0x10,%rax
  cmp    %rdx,%rax
  jne    L131
  mov    %ebx,%edx
  and    $0xfffffff0,%edx
  mov    %edx,%eax
  cmp    %edx,%ebx
  je     L108
  mov    %ebx,%ecx
  sub    %edx,%ecx
  lea    -0x1(%rcx),%esi
  cmp    $0x6,%esi
  jbe    L268
L51:
  mov    (%r12,%rdx,1),%rsi
  mov    %rsi,(%r8,%rdx,1)
  mov    %ecx,%edx
  and    $0xfffffff8,%edx
  add    %edx,%eax
  cmp    %edx,%ecx
  je     L108
L268:
  movslq %eax,%rdx
  movzbl (%r12,%rdx,1),%ecx
  mov    %cl,(%r8,%rdx,1)
  lea    0x1(%rax),%edx
  cmp    %edx,%ebx
  jle    L108
  movslq %edx,%rdx
  movzbl (%r12,%rdx,1),%ecx
  mov    %cl,(%r8,%rdx,1)
  lea    0x2(%rax),%edx
  cmp    %edx,%ebx
  jle    L108
  movslq %edx,%rdx
  movzbl (%r12,%rdx,1),%ecx
  mov    %cl,(%r8,%rdx,1)
  lea    0x3(%rax),%edx
  cmp    %edx,%ebx
  jle    L108
  movslq %edx,%rdx
  movzbl (%r12,%rdx,1),%ecx
  mov    %cl,(%r8,%rdx,1)
  lea    0x4(%rax),%edx
  cmp    %edx,%ebx
  jle    L108
  movslq %edx,%rdx
  movzbl (%r12,%rdx,1),%ecx
  mov    %cl,(%r8,%rdx,1)
  lea    0x5(%rax),%edx
  cmp    %edx,%ebx
  jle    L108
  movslq %edx,%rdx
  add    $0x6,%eax
  movzbl (%r12,%rdx,1),%ecx
  mov    %cl,(%r8,%rdx,1)
  cmp    %eax,%ebx
  jle    L108
  cltq
  movzbl (%r12,%rax,1),%edx
  mov    %dl,(%r8,%rax,1)
L108:
  test   %ebp,%ebp
  jle    L100
  movslq %ebx,%rdx
  lea    0x1(%r13),%rdi
  lea    -0x1(%rbp),%eax
  mov    %ebp,%esi
  add    %r8,%rdx
  mov    %rdx,%rcx
  sub    %rdi,%rcx
  cmp    $0xe,%rcx
  jbe    L327
  cmp    $0x6,%eax
  jbe    L327
  cmp    $0xe,%eax
  jbe    L260
  mov    %ebp,%ecx
  xor    %eax,%eax
  shr    $0x4,%ecx
  shl    $0x4,%rcx
  nopl   0x0(%rax,%rax,1)
L204:
  movdqu 0x0(%r13,%rax,1),%xmm1
  movups %xmm1,(%rdx,%rax,1)
  add    $0x10,%rax
  cmp    %rcx,%rax
  jne    L204
  mov    %ebp,%ecx
  and    $0xfffffff0,%ecx
  mov    %ecx,%eax
  cmp    %ecx,%ebp
  je     L100
  mov    %ebp,%esi
  sub    %ecx,%esi
  lea    -0x1(%rsi),%edi
  cmp    $0x6,%edi
  jbe    L43
L31:
  mov    0x0(%r13,%rcx,1),%rdi
  mov    %rdi,(%rdx,%rcx,1)
  mov    %esi,%edx
  and    $0xfffffff8,%edx
  add    %edx,%eax
  cmp    %edx,%esi
  je     L100
L43:
  movslq %eax,%rdx
  movzbl 0x0(%r13,%rdx,1),%ecx
  lea    (%rbx,%rax,1),%edx
  movslq %edx,%rdx
  mov    %cl,(%r8,%rdx,1)
  lea    0x1(%rax),%edx
  cmp    %edx,%ebp
  jle    L100
  movslq %edx,%rcx
  add    %ebx,%edx
  movzbl 0x0(%r13,%rcx,1),%ecx
  movslq %edx,%rdx
  mov    %cl,(%r8,%rdx,1)
  lea    0x2(%rax),%edx
  cmp    %ebp,%edx
  jge    L100
  movslq %edx,%rcx
  add    %ebx,%edx
  movzbl 0x0(%r13,%rcx,1),%ecx
  movslq %edx,%rdx
  mov    %cl,(%r8,%rdx,1)
  lea    0x3(%rax),%edx
  cmp    %edx,%ebp
  jle    L100
  movslq %edx,%rcx
  add    %ebx,%edx
  movzbl 0x0(%r13,%rcx,1),%ecx
  movslq %edx,%rdx
  mov    %cl,(%r8,%rdx,1)
  lea    0x4(%rax),%edx
  cmp    %edx,%ebp
  jle    L100
  movslq %edx,%rcx
  add    %ebx,%edx
  movzbl 0x0(%r13,%rcx,1),%ecx
  movslq %edx,%rdx
  mov    %cl,(%r8,%rdx,1)
  lea    0x5(%rax),%edx
  cmp    %edx,%ebp
  jle    L100
  movslq %edx,%rcx
  add    %ebx,%edx
  add    $0x6,%eax
  movzbl 0x0(%r13,%rcx,1),%ecx
  movslq %edx,%rdx
  mov    %cl,(%r8,%rdx,1)
  cmp    %eax,%ebp
  jle    L100
  movslq %eax,%rdx
  add    %eax,%ebx
  movzbl 0x0(%r13,%rdx,1),%edx
  movslq %ebx,%rbx
  mov    %dl,(%r8,%rbx,1)
L100:
  add    $0x8,%rsp
  mov    %r8,%rax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
  nopw   0x0(%rax,%rax,1)
L327:
  mov    %ebp,%ebp
  xor    %eax,%eax
  nopl   0x0(%rax)
L243:
  movzbl 0x0(%r13,%rax,1),%ecx
  mov    %cl,(%rdx,%rax,1)
  add    $0x1,%rax
  cmp    %rbp,%rax
  jne    L243
  add    $0x8,%rsp
  mov    %r8,%rax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  ret
  nopl   0x0(%rax,%rax,1)
L240:
  mov    %ebx,%ecx
  xor    %eax,%eax
  nopl   0x0(%rax)
L263:
  movzbl (%r12,%rax,1),%edx
  mov    %dl,(%r8,%rax,1)
  add    $0x1,%rax
  cmp    %rax,%rcx
  jne    L263
  jmp    L108
  nop
L88:
  xor    %ebx,%ebx
  jmp    L108
L260:
  xor    %ecx,%ecx
  xor    %eax,%eax
  jmp    L31
L65:
  xor    %edx,%edx
  xor    %eax,%eax
  jmp    L51
```

assistant: ```c
char *my_strcat(int la, char *a, int lb, char *b) {
  char *s = calloc(la + lb + 1, sizeof(char));
  int i, j;
  for (i = 0; i < la; i++) {
    s[i] = a[i];
  }
  for (j = 0; j < lb; j++) {
    s[i + j] = b[j];
  }
  return s;
}
```