user: What would the C source look like for the assembly code provided here:

```asm
<strstr_GNU_C_Library>:
  endbr64
  mov    %rdi,%rax
  movzbl (%rsi),%edi
  test   %dil,%dil
  je     L9
  sub    $0x1,%rax
L2:
  mov    %rax,%rcx
  add    $0x1,%rax
  movzbl (%rax),%edx
  test   %dl,%dl
  je     L287
  cmp    %dl,%dil
  jne    L2
  movzbl 0x1(%rsi),%r8d
  test   %r8b,%r8b
  je     L9
  lea    0x2(%rcx),%rdx
  movzbl 0x1(%rax),%eax
  cmp    %al,%r8b
  jne    L99
L27:
  push   %rbx
L58:
  lea    -0x1(%rdx),%rax
  movzbl 0x2(%rsi),%ecx
  movzbl 0x1(%rdx),%r10d
  movsbl %cl,%r9d
  cmp    %r9d,%r10d
  je     L142
L285:
  test   %cl,%cl
  jne    L31
L117:
  pop    %rbx
  ret
L31:
  movzbl (%rdx),%eax
  jmp    L40
L179:
  lea    0x1(%rdx),%rax
  jmp    L75
L97:
  mov    %rdx,%rax
L75:
  lea    0x1(%rax),%rdx
  movzbl 0x1(%rax),%eax
  cmp    %al,%r8b
  je     L58
L40:
  cmp    %dil,%al
  je     L97
  test   %al,%al
  je     L124
  movzbl 0x1(%rdx),%eax
  cmp    %al,%dil
  je     L179
  test   %al,%al
  je     L151
  movzbl 0x2(%rdx),%eax
  lea    0x2(%rdx),%rdx
  jmp    L40
L142:
  lea    0x2(%rsi),%r10
  lea    0x1(%rdx),%r9
L50:
  test   %cl,%cl
  je     L117
  movzbl 0x1(%r10),%ecx
  movzbl 0x1(%r9),%ebx
  movsbl %cl,%r11d
  cmp    %r11d,%ebx
  jne    L285
  test   %cl,%cl
  je     L117
  add    $0x2,%r9
  add    $0x2,%r10
  movzbl (%r10),%ecx
  movzbl (%r9),%ebx
  movsbl %cl,%r11d
  cmp    %r11d,%ebx
  je     L50
  jmp    L285
L287:
  mov    $0x0,%eax
  ret
L124:
  mov    $0x0,%eax
  jmp    L117
L151:
  mov    $0x0,%eax
  jmp    L117
L270:
  lea    0x1(%rdx),%rax
  jmp    L87
L77:
  mov    %rdx,%rax
L87:
  lea    0x1(%rax),%rdx
  movzbl 0x1(%rax),%eax
  cmp    %al,%r8b
  je     L27
L99:
  cmp    %dil,%al
  je     L77
  test   %al,%al
  je     L53
  movzbl 0x1(%rdx),%eax
  cmp    %al,%dil
  je     L270
  test   %al,%al
  je     L0
  movzbl 0x2(%rdx),%eax
  lea    0x2(%rdx),%rdx
  jmp    L99
L53:
  mov    $0x0,%eax
  ret
L0:
  mov    $0x0,%eax
  ret
L9:
  ret
```

assistant: ```c
char *strstr_GNU_C_Library(phaystack, pneedle) const char *phaystack;
const char *pneedle;
{
  const unsigned char *haystack, *needle;
  char b;
  const unsigned char *rneedle;
  haystack = (const unsigned char *)phaystack;
  if ((b = *(needle = (const unsigned char *)pneedle))) {
    char c;
    haystack--;
    {
      char a;
      do
        if (!(a = *++haystack))
          goto ret0;
      while (a != b);
    }
    if (!(c = *++needle))
      goto foundneedle;
    ++needle;
    goto jin;
    for (;;) {
      {
        char a;
        if (0)
        jin : {
          if ((a = *++haystack) == c)
            goto crest;
        }
          else a = *++haystack;
        do {
          for (; a != b; a = *++haystack) {
            if (!a)
              goto ret0;
            if ((a = *++haystack) == b)
              break;
            if (!a)
              goto ret0;
          }
        } while ((a = *++haystack) != c);
      }
    crest : {
      char a;
      {
        const unsigned char *rhaystack;
        if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
          do {
            if (!a)
              goto foundneedle;
            if (*++rhaystack != (a = *++needle))
              break;
            if (!a)
              goto foundneedle;
          } while (*++rhaystack == (a = *++needle));
        needle = rneedle;
      }
      if (!a)
        break;
    }
    }
  }
foundneedle:
  return (char *)haystack;
ret0:
  return 0;
}
```