RFC: merging MEM_ATTRS

[Joern Rennecke]

>     I think completely prohibiting merging of MEMs because they have different
>     attributes goes a bit to far.  
> 
> I don't.  It seems peculiar to me that you'd have a valid cross-jump in 
> that case.
> 
> I don't see how it can happen.
> 
> Can you show an example?

int
f (int j)
{
  static int a, b;

  /* do some stuff with a and b  */

  return j ? a : b;
}

The MEM_EXPRs are different here, one referencing a, the other b.