Dynamic array comparison optimization: check for equal pointers?

[Johan]

Hi all,
   I thought that we optimized dynamic array comparison with a 
check to see if the pointers are equal, but I don't see it in our 
array comparison implementation in druntime. Quick checking of 
glibc memcmp also showed that there is no short circuit for when 
the pointers of the slices are equal.

I was expecting something like:
```
   if ( sizes are not equal )
      return false;
   if ( pointers are equal  )
      return true;
   return memcmp;
```

I am surprised that memcmp itself does not implement the pointers 
are equal check. Is there a big impact of adding the shortcircuit 
check to prevent scanning memory?

cheers,
   Johan