user: 下面的汇编指令对应的C源代码是什么:

```asm
<bitfill_unaligned_rev>:
  endbr64
  test   %r9d,%r9d
  jne    L35
  ret
  nopw   0x0(%rax,%rax,1)
L35:
  push   %r15
  mov    %r9d,%r15d
  push   %r14
  mov    %esi,%r14d
  push   %r13
  mov    %r8d,%r13d
  push   %r12
  mov    %ecx,%r12d
  push   %rbp
  mov    %rdi,%rbp
  mov    $0xffffffffffffffff,%rdi
  push   %rbx
  mov    %rdx,%rbx
  sub    $0x18,%rsp
  call   <FB_SHIFT_HIGH@plt>
  lea    (%r14,%r15,1),%ecx
  xor    %edx,%edx
  mov    $0xffffffffffffffff,%rdi
  mov    %rax,0x8(%rsp)
  mov    %ecx,%eax
  divl   0x50(%rsp)
  mov    %ecx,(%rsp)
  mov    %edx,%esi
  call   <FB_SHIFT_HIGH@plt>
  mov    (%rsp),%ecx
  cmp    0x50(%rsp),%ecx
  not    %rax
  mov    0x8(%rsp),%r8
  mov    %rax,%r9
  ja     L60
  mov    %r8,%rax
  mov    0x0(%rbp),%rsi
  and    %r9,%rax
  test   %r9,%r9
  cmovne %rax,%r8
  xor    %rsi,%rbx
  mov    %rbx,%rdi
  mov    %r8,%rdx
  call   <comp@plt>
  mov    %rax,0x0(%rbp)
L100:
  add    $0x18,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L60:
  test   %r8,%r8
  jne    L57
L99:
  mov    %r15d,%eax
  xor    %edx,%edx
  divl   0x50(%rsp)
  mov    %eax,%edx
  cmp    $0x3,%eax
  jbe    L65
  lea    -0x4(%rax),%r8d
  shr    $0x2,%r8d
  add    $0x1,%r8d
  shl    $0x5,%r8
  add    %rbp,%r8
  nopl   0x0(%rax,%rax,1)
L10:
  mov    %rbx,%rdi
  mov    %r12d,%ecx
  mov    %rbx,%rdx
  movdqu 0x0(%rbp),%xmm1
  shl    %cl,%rdi
  mov    %r13d,%ecx
  movq   %rbx,%xmm0
  add    $0x20,%rbp
  shr    %cl,%rdx
  mov    %r12d,%ecx
  movdqu -0x10(%rbp),%xmm4
  or     %rdx,%rdi
  mov    %rdi,%rsi
  mov    %rdi,%rdx
  movq   %rdi,%xmm2
  shl    %cl,%rsi
  mov    %r13d,%ecx
  punpcklqdq %xmm2,%xmm0
  shr    %cl,%rdx
  mov    %r12d,%ecx
  pxor   %xmm0,%xmm1
  or     %rdx,%rsi
  movups %xmm1,-0x20(%rbp)
  mov    %rsi,%rdx
  mov    %rsi,%r10
  movq   %rsi,%xmm0
  shl    %cl,%rdx
  mov    %r13d,%ecx
  shr    %cl,%r10
  mov    %r12d,%ecx
  or     %r10,%rdx
  movq   %rdx,%xmm3
  mov    %rdx,%rbx
  shl    %cl,%rbx
  punpcklqdq %xmm3,%xmm0
  mov    %r13d,%ecx
  pxor   %xmm4,%xmm0
  shr    %cl,%rdx
  movups %xmm0,-0x10(%rbp)
  or     %rdx,%rbx
  cmp    %rbp,%r8
  jne    L10
  and    $0x3,%eax
  mov    %eax,%edx
L65:
  test   %edx,%edx
  je     L85
  mov    %rbx,%rsi
  mov    %r12d,%ecx
  mov    0x0(%rbp),%rax
  shl    %cl,%rsi
  mov    %r13d,%ecx
  xor    %rbx,%rax
  shr    %cl,%rbx
  or     %rsi,%rbx
  cmp    $0x1,%edx
  je     L104
  mov    %rbx,%rsi
  mov    %r12d,%ecx
  xor    %rbx,%rax
  shl    %cl,%rsi
  mov    %r13d,%ecx
  shr    %cl,%rbx
  or     %rsi,%rbx
  cmp    $0x2,%edx
  je     L104
  mov    %rbx,%rdx
  mov    %r12d,%ecx
  xor    %rbx,%rax
  shl    %cl,%rdx
  mov    %r13d,%ecx
  shr    %cl,%rbx
  or     %rdx,%rbx
L104:
  mov    %rax,0x0(%rbp)
L85:
  test   %r9,%r9
  je     L100
  mov    0x0(%rbp),%rsi
  mov    %r9,%rdx
  xor    %rsi,%rbx
  mov    %rbx,%rdi
  call   <comp@plt>
  mov    %rax,0x0(%rbp)
  jmp    L100
  nopw   0x0(%rax,%rax,1)
L57:
  mov    0x0(%rbp),%rsi
  mov    %r8,%rdx
  mov    %rax,(%rsp)
  add    $0x8,%rbp
  mov    %rsi,%rdi
  xor    %rbx,%rdi
  call   <comp@plt>
  mov    %r12d,%ecx
  mov    (%rsp),%r9
  mov    %rax,-0x8(%rbp)
  mov    %rbx,%rax
  shl    %cl,%rax
  mov    %r13d,%ecx
  shr    %cl,%rbx
  or     %rax,%rbx
  mov    0x50(%rsp),%eax
  sub    %r14d,%eax
  sub    %eax,%r15d
  jmp    L99
```

assistant: ```c
void bitfill_unaligned_rev(unsigned long *dst, int dst_idx, unsigned long pat, int left, int right, unsigned n, int bits) {
  unsigned long first, last;
  if (!n)
    return;
  first = FB_SHIFT_HIGH(~0UL, dst_idx);
  last = ~(FB_SHIFT_HIGH(~0UL, (dst_idx + n) % bits));
  if (dst_idx + n <= bits) {
    if (last)
      first &= last;
    *dst = comp(*dst ^ pat, *dst, first);
  } else {
    if (first != 0UL) {
      *dst = comp(*dst ^ pat, *dst, first);
      dst++;
      pat = pat << left | pat >> right;
      n -= bits - dst_idx;
    }
    n /= bits;
    while (n >= 4) {
      *dst++ ^= pat;
      pat = pat << left | pat >> right;
      *dst++ ^= pat;
      pat = pat << left | pat >> right;
      *dst++ ^= pat;
      pat = pat << left | pat >> right;
      *dst++ ^= pat;
      pat = pat << left | pat >> right;
      n -= 4;
    }
    while (n--) {
      *dst ^= pat;
      pat = pat << left | pat >> right;
    }
    if (last)
      *dst = comp(*dst ^ pat, *dst, last);
  }
}
```