user: 请从给定的汇编指令推导出C源代码:

```asm
<foo>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  mov    %edx,-0xc(%rsp)
  movzwl %di,%r15d
  shr    $0x10,%rdi
  movzwl %di,%eax
  mov    %rax,-0x20(%rsp)
  test   %rsi,%rsi
  je     L65
  test   %edx,%edx
  je     L19
  mov    %rsi,%rdi
  jmp    L44
L0:
  movabs $0xf00e10d2fc5cd,%rax
  mul    %r15
  mov    %r15,%rax
  sub    %rdx,%rax
  shr    %rax
  add    %rax,%rdx
  shr    $0xf,%rdx
  imul   $0xfff1,%rdx,%rdx
  sub    %rdx,%r15
  movabs $0xf00e10d2fc5cd,%rax
  mov    -0x20(%rsp),%rcx
  mul    %rcx
  mov    %rcx,%rax
  sub    %rdx,%rax
  shr    %rax
  add    %rax,%rdx
  shr    $0xf,%rdx
  imul   $0xfff1,%rdx,%rdx
  sub    %rdx,%rcx
  mov    %rcx,-0x20(%rsp)
  cmpl   $0x0,-0xc(%rsp)
  je     L19
L44:
  mov    $0x15b0,%eax
  mov    -0xc(%rsp),%ebx
  cmp    %eax,%ebx
  cmovbe %ebx,%eax
  mov    %eax,-0x8(%rsp)
  mov    %eax,%ecx
  sub    %eax,%ebx
  mov    %ebx,-0xc(%rsp)
  cmp    $0xf,%eax
  jle    L95
  sub    $0x10,%eax
  shr    $0x4,%eax
  mov    %eax,-0x4(%rsp)
  add    $0x1,%eax
  mov    %eax,%eax
  shl    $0x4,%rax
  add    %rdi,%rax
  mov    %rax,-0x18(%rsp)
L93:
  movzbl (%rdi),%eax
  add    %r15,%rax
  movzbl 0x1(%rdi),%r14d
  add    %rax,%r14
  movzbl 0x2(%rdi),%r13d
  add    %r14,%r13
  movzbl 0x3(%rdi),%r12d
  add    %r13,%r12
  movzbl 0x4(%rdi),%ebp
  add    %r12,%rbp
  movzbl 0x5(%rdi),%ebx
  add    %rbp,%rbx
  movzbl 0x6(%rdi),%r11d
  add    %rbx,%r11
  movzbl 0x7(%rdi),%edx
  lea    (%rdx,%r11,1),%rsi
  movzbl 0x8(%rdi),%edx
  mov    %rsi,-0x30(%rsp)
  add    %rsi,%rdx
  movzbl 0x9(%rdi),%r10d
  mov    %rdx,-0x28(%rsp)
  add    %rdx,%r10
  movzbl 0xa(%rdi),%r9d
  add    %r10,%r9
  movzbl 0xb(%rdi),%r8d
  add    %r9,%r8
  movzbl 0xc(%rdi),%esi
  add    %r8,%rsi
  movzbl 0xd(%rdi),%ecx
  add    %rsi,%rcx
  movzbl 0xe(%rdi),%edx
  add    %rcx,%rdx
  add    $0x10,%rdi
  movzbl -0x1(%rdi),%r15d
  add    %rdx,%r15
  add    %r14,%rax
  add    %r13,%rax
  add    %r12,%rax
  add    %rbp,%rax
  add    %rbx,%rax
  add    %r11,%rax
  add    -0x30(%rsp),%rax
  add    -0x28(%rsp),%rax
  add    %r10,%rax
  add    %r9,%rax
  add    %r8,%rax
  add    %rsi,%rax
  add    %rcx,%rax
  add    %rdx,%rax
  add    %r15,%rax
  add    %rax,-0x20(%rsp)
  cmp    %rdi,-0x18(%rsp)
  jne    L93
  mov    -0x4(%rsp),%eax
  neg    %eax
  shl    $0x4,%eax
  mov    -0x8(%rsp),%ecx
  lea    -0x10(%rcx,%rax,1),%ecx
L95:
  test   %ecx,%ecx
  je     L0
  lea    -0x1(%rcx),%eax
  lea    0x1(%rdi,%rax,1),%rsi
  mov    %rdi,%rax
  mov    -0x20(%rsp),%rdx
L38:
  add    $0x1,%rax
  movzbl -0x1(%rax),%r8d
  add    %r8,%r15
  add    %r15,%rdx
  cmp    %rsi,%rax
  jne    L38
  mov    %rdx,-0x20(%rsp)
  lea    -0x1(%rcx),%eax
  lea    0x1(%rdi,%rax,1),%rdi
  jmp    L0
L19:
  mov    -0x20(%rsp),%rax
  shl    $0x10,%rax
  or     %r15,%rax
L46:
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L65:
  mov    $0x1,%eax
  jmp    L46
```

assistant: ```c
unsigned long foo(unsigned long x, unsigned char *y, unsigned int z) {
  unsigned long a = x & 0xffff;
  unsigned long b = (x >> 16) & 0xffff;
  int k;
  if (y == 0)
    return 1L;
  while (z > 0) {
    k = z < 5552 ? z : 5552;
    z -= k;
    while (k >= 16) {
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      a += *y++;
      b += a;
      k -= 16;
    }
    if (k != 0)
      do {
        a += *y++;
        b += a;
      } while (--k);
    a %= 65521L;
    b %= 65521L;
  }
  return (b << 16) | a;
}
```