[tree-ssa] must-alias analysis

[law@redhat.com]

In message <1058188446.21784.4.camel@p4>, Andrew MacLeod writes:
 >On Mon, 2003-07-14 at 09:03, Diego Novillo wrote:
 >
 >> There are a few things that I'd like to fix in the current
 >> implementation.
 >> 
 >> We now do a full DCE pass right after SSA construction just to get the
 >> 'PTR = &VAR' statements removed.  We could probably get by with a very
 >> simplistic pass that just looked for these assignments.  It would be
 >> less powerful, but it would catch most of the cases we are interested
 >> in.
 >
 >Im not sure I'd worry about this one just yet. If we do end up doing any
 >scalarization of component refs or 'localization' of global variables, I
 >suspect we'll be exposing some other dead code which would be beneficial
 >to remove at this time too.   We'll see :-)
 >
 >DCE ought not be very expensive anyway...
You might be surprised how expensive our DCE pass is....  While it's
relatively fast, it's not one I'd want to be running several times.


Jeff