user: Converte this assembly snippet into its equivalent C code:

```asm
<idctcol>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %rdi,-0x38(%rbp)
  mov    -0x38(%rbp),%rax
  add    $0x40,%rax
  movzwl (%rax),%eax
  cwtl
  shl    $0x8,%eax
  mov    %eax,-0x24(%rbp)
  mov    -0x38(%rbp),%rax
  add    $0x60,%rax
  movzwl (%rax),%eax
  cwtl
  mov    %eax,-0x20(%rbp)
  mov    -0x24(%rbp),%eax
  or     -0x20(%rbp),%eax
  mov    -0x38(%rbp),%rdx
  add    $0x20,%rdx
  movzwl (%rdx),%edx
  movswl %dx,%edx
  mov    %edx,-0x1c(%rbp)
  or     -0x1c(%rbp),%eax
  mov    -0x38(%rbp),%rdx
  add    $0x10,%rdx
  movzwl (%rdx),%edx
  movswl %dx,%edx
  mov    %edx,-0x18(%rbp)
  or     -0x18(%rbp),%eax
  mov    -0x38(%rbp),%rdx
  add    $0x70,%rdx
  movzwl (%rdx),%edx
  movswl %dx,%edx
  mov    %edx,-0x14(%rbp)
  or     -0x14(%rbp),%eax
  mov    -0x38(%rbp),%rdx
  add    $0x50,%rdx
  movzwl (%rdx),%edx
  movswl %dx,%edx
  mov    %edx,-0x10(%rbp)
  or     -0x10(%rbp),%eax
  mov    -0x38(%rbp),%rdx
  add    $0x30,%rdx
  movzwl (%rdx),%edx
  movswl %dx,%edx
  mov    %edx,-0xc(%rbp)
  or     -0xc(%rbp),%eax
  test   %eax,%eax
  jne    L10
  mov    -0x38(%rbp),%rax
  movzwl (%rax),%eax
  cwtl
  add    $0x20,%eax
  sar    $0x6,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x70,%rax
  mov    %dx,(%rax)
  mov    -0x38(%rbp),%rdx
  add    $0x60,%rdx
  movzwl (%rax),%eax
  mov    %ax,(%rdx)
  mov    -0x38(%rbp),%rax
  add    $0x50,%rax
  movzwl (%rdx),%edx
  mov    %dx,(%rax)
  mov    -0x38(%rbp),%rdx
  add    $0x40,%rdx
  movzwl (%rax),%eax
  mov    %ax,(%rdx)
  mov    -0x38(%rbp),%rax
  add    $0x30,%rax
  movzwl (%rdx),%edx
  mov    %dx,(%rax)
  mov    -0x38(%rbp),%rdx
  add    $0x20,%rdx
  movzwl (%rax),%eax
  mov    %ax,(%rdx)
  mov    -0x38(%rbp),%rax
  add    $0x10,%rax
  movzwl (%rdx),%edx
  mov    %dx,(%rax)
  movzwl (%rax),%edx
  mov    -0x38(%rbp),%rax
  mov    %dx,(%rax)
  jmp    L18
L10:
  mov    -0x38(%rbp),%rax
  movzwl (%rax),%eax
  cwtl
  shl    $0x8,%eax
  add    $0x2000,%eax
  mov    %eax,-0x8(%rbp)
  mov    -0x18(%rbp),%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  imul   $0x235,%eax,%eax
  add    $0x4,%eax
  mov    %eax,-0x4(%rbp)
  mov    -0x18(%rbp),%eax
  imul   $0x8e4,%eax,%edx
  mov    -0x4(%rbp),%eax
  add    %edx,%eax
  sar    $0x3,%eax
  mov    %eax,-0x18(%rbp)
  mov    -0x14(%rbp),%eax
  imul   $0xfffff2b2,%eax,%edx
  mov    -0x4(%rbp),%eax
  add    %edx,%eax
  sar    $0x3,%eax
  mov    %eax,-0x14(%rbp)
  mov    -0x10(%rbp),%edx
  mov    -0xc(%rbp),%eax
  add    %edx,%eax
  imul   $0x968,%eax,%eax
  add    $0x4,%eax
  mov    %eax,-0x4(%rbp)
  mov    -0x10(%rbp),%eax
  imul   $0xfffffce1,%eax,%edx
  mov    -0x4(%rbp),%eax
  add    %edx,%eax
  sar    $0x3,%eax
  mov    %eax,-0x10(%rbp)
  mov    -0xc(%rbp),%eax
  imul   $0xfffff04f,%eax,%edx
  mov    -0x4(%rbp),%eax
  add    %edx,%eax
  sar    $0x3,%eax
  mov    %eax,-0xc(%rbp)
  mov    -0x8(%rbp),%edx
  mov    -0x24(%rbp),%eax
  add    %edx,%eax
  mov    %eax,-0x4(%rbp)
  mov    -0x24(%rbp),%eax
  sub    %eax,-0x8(%rbp)
  mov    -0x1c(%rbp),%edx
  mov    -0x20(%rbp),%eax
  add    %edx,%eax
  imul   $0x454,%eax,%eax
  add    $0x4,%eax
  mov    %eax,-0x24(%rbp)
  mov    -0x20(%rbp),%eax
  imul   $0xfffff138,%eax,%edx
  mov    -0x24(%rbp),%eax
  add    %edx,%eax
  sar    $0x3,%eax
  mov    %eax,-0x20(%rbp)
  mov    -0x1c(%rbp),%eax
  imul   $0x620,%eax,%edx
  mov    -0x24(%rbp),%eax
  add    %edx,%eax
  sar    $0x3,%eax
  mov    %eax,-0x1c(%rbp)
  mov    -0x18(%rbp),%edx
  mov    -0x10(%rbp),%eax
  add    %edx,%eax
  mov    %eax,-0x24(%rbp)
  mov    -0x10(%rbp),%eax
  sub    %eax,-0x18(%rbp)
  mov    -0x14(%rbp),%edx
  mov    -0xc(%rbp),%eax
  add    %edx,%eax
  mov    %eax,-0x10(%rbp)
  mov    -0xc(%rbp),%eax
  sub    %eax,-0x14(%rbp)
  mov    -0x4(%rbp),%edx
  mov    -0x1c(%rbp),%eax
  add    %edx,%eax
  mov    %eax,-0xc(%rbp)
  mov    -0x1c(%rbp),%eax
  sub    %eax,-0x4(%rbp)
  mov    -0x8(%rbp),%edx
  mov    -0x20(%rbp),%eax
  add    %edx,%eax
  mov    %eax,-0x1c(%rbp)
  mov    -0x20(%rbp),%eax
  sub    %eax,-0x8(%rbp)
  mov    -0x18(%rbp),%edx
  mov    -0x14(%rbp),%eax
  add    %edx,%eax
  imul   $0xb5,%eax,%eax
  sub    $0xffffff80,%eax
  sar    $0x8,%eax
  mov    %eax,-0x20(%rbp)
  mov    -0x18(%rbp),%eax
  sub    -0x14(%rbp),%eax
  imul   $0xb5,%eax,%eax
  sub    $0xffffff80,%eax
  sar    $0x8,%eax
  mov    %eax,-0x18(%rbp)
  mov    -0xc(%rbp),%edx
  mov    -0x24(%rbp),%eax
  add    %edx,%eax
  sar    $0xe,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  mov    %dx,(%rax)
  mov    -0x1c(%rbp),%edx
  mov    -0x20(%rbp),%eax
  add    %edx,%eax
  sar    $0xe,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x10,%rax
  mov    %dx,(%rax)
  mov    -0x8(%rbp),%edx
  mov    -0x18(%rbp),%eax
  add    %edx,%eax
  sar    $0xe,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x20,%rax
  mov    %dx,(%rax)
  mov    -0x4(%rbp),%edx
  mov    -0x10(%rbp),%eax
  add    %edx,%eax
  sar    $0xe,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x30,%rax
  mov    %dx,(%rax)
  mov    -0x4(%rbp),%eax
  sub    -0x10(%rbp),%eax
  sar    $0xe,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x40,%rax
  mov    %dx,(%rax)
  mov    -0x8(%rbp),%eax
  sub    -0x18(%rbp),%eax
  sar    $0xe,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x50,%rax
  mov    %dx,(%rax)
  mov    -0x1c(%rbp),%eax
  sub    -0x20(%rbp),%eax
  sar    $0xe,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x60,%rax
  mov    %dx,(%rax)
  mov    -0xc(%rbp),%eax
  sub    -0x24(%rbp),%eax
  sar    $0xe,%eax
  mov    %eax,%edx
  mov    -0x38(%rbp),%rax
  add    $0x70,%rax
  mov    %dx,(%rax)
L18:
  pop    %rbp
  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;
}
```