Re: [PATCH] Make alias_sets_conflict_p less conservative

[Michael Matz <matz at suse dot de>]

Hi,

On Wed, 5 Mar 2008, Richard Guenther wrote:

> But - Joseph, do you have any idea if it in theory could be made to work 
> with char not being alias set zero?  The FE would need to mark every 
> lvalue of type char with a special flag.

If that should be possible, it's no different to making 'char' have alias 
set zero.  Given:

struct S {char c; int i;};
struct T {double d;};

f () {
  struct S s;
  s.c = 0;
}

Here the lvalue s.c would then have the "special flag" (i suppose the 
semantic you had in mind for that flag would be "alias everything"), so it 
would conflict with everything which of course it can't.  It won't 
conflict with T.d for instance, so we're back to square one.


Ciao,
Michael.