[ tree-ssa] PRE problem

[Diego Novillo]

On Fri, 2004-02-20 at 14:56, law@redhat.com wrote:

>   p = x;
>   y = p;
>       *y;
> 
> "y" will have a tag, but by no means does that mean p or x will have a
> tag.
> 
We are talking past each other again.  When I say it's impossible for
them to have different tags, I am talking about *non-NULL* tags.  It's
perfectly OK for a pointer to *not* have a tag.  Only dereferenced
pointers need tags.

To summarize:

p = PHI <q, r>

If all three pointers 'p', 'q' and 'r' have been dereferenced, then they
must have the same tag.


Diego.