Re: Fully flow and context sensitive points-to analysis in GCC 4.6.0

["Uday P. Khedker" <uday at cse dot iitb dot ac dot in>]

Excellent! Thanks.

Uday.

Richard Biener wrote, On Friday 12 October 2012 03:20 PM:
> On Fri, Oct 12, 2012 at 11:46 AM, Uday P. Khedker <uday@cse.iitb.ac.in> wrote:
> > Richard Biener wrote, On Friday 12 October 2012 02:51 PM:
> >
> > > we _always_ see
> > >
> > >     ssa_name_1 = a;
> > >     use (ssa_name_1);
> > >
> > > so you have a place to associate your flow-sensitive and context-sensitive
> > > points-to-info with (the SSA name).  My point is that for _using_ the
> > > points-to info flow-sensitivity provided by SSA form is enough.  For
> > > computing
> > > it you of course need to flow-sensitively process assignments to 'a'.
> >
> >
> > This is VERY interesting! I had not thought about the difference between
> > computing
> > and using values. Now that you point it out, I think all we need to do is to
> > map
> > flow-sensitively computed values to ssa names.
> >
> > What about variables that do not have ssa names? Or are you saying that all
> > such
> > variables would be copied into an artificial variables that have ssa names?
> > I seem
> > to observe this in the dumps but I don't know if it holds in general.
>
> Yes, that's what I say.  Any pointer that is dereferenced is first copied to
> an SSA name.  Basically everything residing in memory first has to be
> loaded to an SSA name before it can be dereferenced.  That load is explicit
> in the IL so you should already compute points-to sets for the SSA name
> destination of the load.
>
> Richard.
>
>
> > Uday.