user: 请从给定的汇编指令推导出C源代码：

```asm
<idctcol>:
  endbr64
  push   %rbx
  movswl 0x60(%rdi),%r8d
  mov    %rdi,%rax
  movswl 0x20(%rdi),%r9d
  movswl 0x10(%rdi),%edx
  mov    %r8d,%esi
  movswl 0x40(%rdi),%ebx
  movswl 0x70(%rdi),%edi
  or     %r9d,%esi
  movswl 0x50(%rax),%r11d
  movswl 0x30(%rax),%r10d
  or     %edx,%esi
  shl    $0x8,%ebx
  movswl (%rax),%ecx
  or     %edi,%esi
  or     %r11d,%esi
  or     %r10d,%esi
  movswl %si,%esi
  or     %ebx,%esi
  je     L9
  lea    (%rdx,%rdi,1),%esi
  shl    $0x8,%ecx
  imul   $0x235,%esi,%esi
  add    $0x2000,%ecx
  imul   $0x8e4,%edx,%edx
  imul   $0xfffff2b2,%edi,%edi
  add    $0x4,%esi
  add    %esi,%edx
  add    %esi,%edi
  lea    (%r11,%r10,1),%esi
  sar    $0x3,%edx
  imul   $0x968,%esi,%esi
  sar    $0x3,%edi
  imul   $0xfffffce1,%r11d,%r11d
  imul   $0xfffff04f,%r10d,%r10d
  add    $0x4,%esi
  add    %esi,%r11d
  add    %esi,%r10d
  lea    (%rbx,%rcx,1),%esi
  sub    %ebx,%ecx
  sar    $0x3,%r11d
  lea    (%r8,%r9,1),%ebx
  sar    $0x3,%r10d
  imul   $0x454,%ebx,%ebx
  imul   $0xfffff138,%r8d,%r8d
  imul   $0x620,%r9d,%r9d
  add    $0x4,%ebx
  add    %ebx,%r8d
  add    %ebx,%r9d
  sar    $0x3,%r8d
  lea    (%rdx,%r11,1),%ebx
  sub    %r11d,%edx
  sar    $0x3,%r9d
  lea    (%rdi,%r10,1),%r11d
  sub    %r10d,%edi
  lea    (%rsi,%r9,1),%r10d
  sub    %r9d,%esi
  lea    (%rcx,%r8,1),%r9d
  sub    %r8d,%ecx
  lea    (%rdx,%rdi,1),%r8d
  imul   $0xb5,%r8d,%r8d
  sub    $0xffffff80,%r8d
  sub    %edi,%edx
  lea    (%rbx,%r10,1),%edi
  sub    %ebx,%r10d
  imul   $0xb5,%edx,%edx
  sar    $0x8,%r8d
  sar    $0xe,%edi
  pop    %rbx
  mov    %di,(%rax)
  lea    (%r9,%r8,1),%edi
  sub    %r8d,%r9d
  sar    $0xe,%r10d
  sar    $0xe,%edi
  sar    $0xe,%r9d
  mov    %r10w,0x70(%rax)
  sub    $0xffffff80,%edx
  mov    %di,0x10(%rax)
  sar    $0x8,%edx
  mov    %r9w,0x60(%rax)
  lea    (%rcx,%rdx,1),%edi
  sub    %edx,%ecx
  sar    $0xe,%edi
  sar    $0xe,%ecx
  mov    %di,0x20(%rax)
  lea    (%r11,%rsi,1),%edi
  sub    %r11d,%esi
  sar    $0xe,%edi
  sar    $0xe,%esi
  mov    %cx,0x50(%rax)
  mov    %di,0x30(%rax)
  mov    %si,0x40(%rax)
  ret
  nop
L9:
  add    $0x20,%ecx
  pop    %rbx
  sar    $0x6,%ecx
  mov    %cx,0x70(%rax)
  mov    %cx,0x60(%rax)
  mov    %cx,0x50(%rax)
  mov    %cx,0x40(%rax)
  mov    %cx,0x30(%rax)
  mov    %cx,0x20(%rax)
  mov    %cx,0x10(%rax)
  mov    %cx,(%rax)
  ret
```

assistant: ```c
void idctcol(blk) short *blk;
{
  int x0, x1, x2, x3, x4, x5, x6, x7, x8;
  if (!((x1 = (blk[8 * 4] << 8)) | (x2 = blk[8 * 6]) | (x3 = blk[8 * 2]) | (x4 = blk[8 * 1]) | (x5 = blk[8 * 7]) | (x6 = blk[8 * 5]) | (x7 = blk[8 * 3]))) {
    blk[8 * 0] = blk[8 * 1] = blk[8 * 2] = blk[8 * 3] = blk[8 * 4] = blk[8 * 5] = blk[8 * 6] = blk[8 * 7] = (blk[8 * 0] + 32) >> 6;
    return;
  }
  x0 = (blk[8 * 0] << 8) + 8192;
  x8 = 565 * (x4 + x5) + 4;
  x4 = (x8 + (2841 - 565) * x4) >> 3;
  x5 = (x8 - (2841 + 565) * x5) >> 3;
  x8 = 2408 * (x6 + x7) + 4;
  x6 = (x8 - (2408 - 1609) * x6) >> 3;
  x7 = (x8 - (2408 + 1609) * x7) >> 3;
  x8 = x0 + x1;
  x0 -= x1;
  x1 = 1108 * (x3 + x2) + 4;
  x2 = (x1 - (2676 + 1108) * x2) >> 3;
  x3 = (x1 + (2676 - 1108) * x3) >> 3;
  x1 = x4 + x6;
  x4 -= x6;
  x6 = x5 + x7;
  x5 -= x7;
  x7 = x8 + x3;
  x8 -= x3;
  x3 = x0 + x2;
  x0 -= x2;
  x2 = (181 * (x4 + x5) + 128) >> 8;
  x4 = (181 * (x4 - x5) + 128) >> 8;
  blk[8 * 0] = (x7 + x1) >> 14;
  blk[8 * 1] = (x3 + x2) >> 14;
  blk[8 * 2] = (x0 + x4) >> 14;
  blk[8 * 3] = (x8 + x6) >> 14;
  blk[8 * 4] = (x8 - x6) >> 14;
  blk[8 * 5] = (x0 - x4) >> 14;
  blk[8 * 6] = (x3 - x2) >> 14;
  blk[8 * 7] = (x7 - x1) >> 14;
}
```