user: 请从给定的汇编指令推导出C源代码：

```asm
<addStrings>:
  endbr64
  push   %r14
  push   %r13
  push   %r12
  mov    %rdi,%r12
  push   %rbp
  mov    %rsi,%rbp
  push   %rbx
  call   <strlen@plt>
  mov    %rbp,%rdi
  mov    %eax,%ebx
  call   <strlen@plt>
  lea    (%rbx,%rax,1),%r13d
  mov    %eax,%r14d
  lea    0x1(%r13),%edi
  call   <malloc@plt>
  test   %ebx,%ebx
  jle    L336
  lea    0x1(%r12),%rdi
  mov    %rax,%rcx
  lea    -0x1(%rbx),%edx
  mov    %ebx,%esi
  sub    %rdi,%rcx
  cmp    $0xe,%rcx
  jbe    L13
  cmp    $0x6,%edx
  jbe    L13
  cmp    $0xe,%edx
  jbe    L158
  mov    %ebx,%ecx
  xor    %edx,%edx
  shr    $0x4,%ecx
  shl    $0x4,%rcx
L127:
  movdqu (%r12,%rdx,1),%xmm0
  movups %xmm0,(%rax,%rdx,1)
  add    $0x10,%rdx
  cmp    %rcx,%rdx
  jne    L127
  mov    %ebx,%ecx
  and    $0xfffffff0,%ecx
  mov    %ecx,%edx
  cmp    %ecx,%ebx
  je     L336
  mov    %ebx,%esi
  sub    %ecx,%esi
  lea    -0x1(%rsi),%edi
  cmp    $0x6,%edi
  jbe    L307
L198:
  mov    (%r12,%rcx,1),%rdi
  mov    %rdi,(%rax,%rcx,1)
  mov    %esi,%ecx
  and    $0xfffffff8,%ecx
  add    %ecx,%edx
  cmp    %ecx,%esi
  je     L336
L307:
  movslq %edx,%rcx
  movzbl (%r12,%rcx,1),%esi
  mov    %sil,(%rax,%rcx,1)
  lea    0x1(%rdx),%ecx
  cmp    %ecx,%ebx
  jle    L336
  movslq %ecx,%rcx
  movzbl (%r12,%rcx,1),%esi
  mov    %sil,(%rax,%rcx,1)
  lea    0x2(%rdx),%ecx
  cmp    %ecx,%ebx
  jle    L336
  movslq %ecx,%rcx
  movzbl (%r12,%rcx,1),%esi
  mov    %sil,(%rax,%rcx,1)
  lea    0x3(%rdx),%ecx
  cmp    %ecx,%ebx
  jle    L336
  movslq %ecx,%rcx
  movzbl (%r12,%rcx,1),%esi
  mov    %sil,(%rax,%rcx,1)
  lea    0x4(%rdx),%ecx
  cmp    %ecx,%ebx
  jle    L336
  movslq %ecx,%rcx
  movzbl (%r12,%rcx,1),%esi
  mov    %sil,(%rax,%rcx,1)
  lea    0x5(%rdx),%ecx
  cmp    %ecx,%ebx
  jle    L336
  movslq %ecx,%rcx
  add    $0x6,%edx
  movzbl (%r12,%rcx,1),%esi
  mov    %sil,(%rax,%rcx,1)
  cmp    %edx,%ebx
  jle    L336
  movslq %edx,%rdx
  movzbl (%r12,%rdx,1),%ecx
  mov    %cl,(%rax,%rdx,1)
L336:
  cmp    %ebx,%r13d
  jle    L260
  movslq %ebx,%rdx
  lea    0x1(%rbp),%r9
  lea    -0x1(%r14),%ecx
  mov    %r14d,%edi
  lea    (%rax,%rdx,1),%rsi
  mov    %rsi,%r8
  sub    %r9,%r8
  cmp    $0xe,%r8
  jbe    L93
  cmp    $0x6,%ecx
  jbe    L93
  cmp    $0xe,%ecx
  jbe    L304
  mov    %r14d,%ecx
  xor    %edx,%edx
  shr    $0x4,%ecx
  shl    $0x4,%rcx
  nopw   0x0(%rax,%rax,1)
L8:
  movdqu 0x0(%rbp,%rdx,1),%xmm1
  movups %xmm1,(%rsi,%rdx,1)
  add    $0x10,%rdx
  cmp    %rcx,%rdx
  jne    L8
  mov    %r14d,%ecx
  and    $0xfffffff0,%ecx
  lea    (%rcx,%rbx,1),%edx
  cmp    %ecx,%r14d
  je     L260
  mov    %r14d,%edi
  sub    %ecx,%edi
  lea    -0x1(%rdi),%r8d
  cmp    $0x6,%r8d
  jbe    L177
L31:
  mov    0x0(%rbp,%rcx,1),%r8
  mov    %r8,(%rsi,%rcx,1)
  mov    %edi,%ecx
  and    $0xfffffff8,%ecx
  add    %ecx,%edx
  cmp    %ecx,%edi
  je     L260
L177:
  mov    %edx,%ecx
  sub    %ebx,%ecx
  movslq %ecx,%rcx
  movzbl 0x0(%rbp,%rcx,1),%esi
  movslq %edx,%rcx
  mov    %sil,(%rax,%rcx,1)
  lea    0x1(%rdx),%ecx
  cmp    %ecx,%r13d
  jle    L260
  mov    %ecx,%esi
  movslq %ecx,%rcx
  sub    %ebx,%esi
  movslq %esi,%rsi
  movzbl 0x0(%rbp,%rsi,1),%esi
  mov    %sil,(%rax,%rcx,1)
  lea    0x2(%rdx),%ecx
  cmp    %ecx,%r13d
  jle    L260
  mov    %ecx,%esi
  movslq %ecx,%rcx
  sub    %ebx,%esi
  movslq %esi,%rsi
  movzbl 0x0(%rbp,%rsi,1),%esi
  mov    %sil,(%rax,%rcx,1)
  lea    0x3(%rdx),%ecx
  cmp    %ecx,%r13d
  jle    L260
  mov    %ecx,%esi
  movslq %ecx,%rcx
  sub    %ebx,%esi
  movslq %esi,%rsi
  movzbl 0x0(%rbp,%rsi,1),%esi
  mov    %sil,(%rax,%rcx,1)
  lea    0x4(%rdx),%ecx
  cmp    %ecx,%r13d
  jle    L260
  mov    %ecx,%esi
  movslq %ecx,%rcx
  sub    %ebx,%esi
  movslq %esi,%rsi
  movzbl 0x0(%rbp,%rsi,1),%esi
  mov    %sil,(%rax,%rcx,1)
  lea    0x5(%rdx),%ecx
  cmp    %ecx,%r13d
  jle    L260
  mov    %ecx,%esi
  add    $0x6,%edx
  movslq %ecx,%rcx
  sub    %ebx,%esi
  movslq %esi,%rsi
  movzbl 0x0(%rbp,%rsi,1),%esi
  mov    %sil,(%rax,%rcx,1)
  cmp    %edx,%r13d
  jle    L260
  mov    %edx,%ecx
  movslq %edx,%rdx
  sub    %ebx,%ecx
  movslq %ecx,%rcx
  movzbl 0x0(%rbp,%rcx,1),%ecx
  mov    %cl,(%rax,%rdx,1)
L260:
  movslq %r13d,%r13
  movb   $0x0,(%rax,%r13,1)
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  ret
  nopl   (%rax)
L93:
  sub    %rdx,%rbp
  nopl   0x0(%rax,%rax,1)
L136:
  movzbl 0x0(%rbp,%rdx,1),%ecx
  mov    %cl,(%rax,%rdx,1)
  add    $0x1,%rdx
  cmp    %edx,%r13d
  jg     L136
  jmp    L260
  nopl   0x0(%rax,%rax,1)
L13:
  mov    %ebx,%esi
  xor    %edx,%edx
  nopl   0x0(%rax)
L204:
  movzbl (%r12,%rdx,1),%ecx
  mov    %cl,(%rax,%rdx,1)
  add    $0x1,%rdx
  cmp    %rdx,%rsi
  jne    L204
  jmp    L336
L158:
  xor    %ecx,%ecx
  xor    %edx,%edx
  jmp    L198
L304:
  mov    %ebx,%edx
  xor    %ecx,%ecx
  jmp    L31
```

assistant: ```c
char *addStrings(char *a, char *b) {
  int alen = strlen(a);
  int blen = strlen(b);
  char *sum = malloc(alen + blen + 1);
  int i;
  for (i = 0; i < alen; i++)
    sum[i] = a[i];
  for (i = alen; i < alen + blen; i++)
    sum[i] = b[i - alen];
  sum[alen + blen] = 0;
  return sum;
}
```