Re: Minor CCP improvement and add comments to tree.h

[Daniel Berlin <dberlin at dberlin dot org>]

On Sep 22, 2004, at 9:52 AM, Jeffrey A Law wrote:

> On Wed, 2004-09-22 at 05:44, Diego Novillo wrote:
> > On Wed, 2004-09-22 at 00:05, Jeffrey A Law wrote:
> >
> > > This patch updates CCP to use any recorded equivalency information
> > > in SSA_NAME_EQUIV to seed the CCP values array and at the end of CCP,
> > > we transfer any equivalences discovered by CCP into the 
> > > SSA_NAME_EQUIV
> > > field as well.
> > Why not use SSA_NAME_VALUE?  PRE uses to store value handles, CCP and
> > copy-prop (will) use it for storing constant/copies.  Adding another
> > field to tree_ssa_name doesn't seem like a good idea.
> If we're using the field to communicate equivalency information across
> passes, then every pass needs to store the same kind of data in that
> field.  So the question I would have is does SSA_NAME_VALUE record
> an equivalency in PRE or is a "value handle" something different?

For constants, it's an equivalency.
For other equivalences, a value handle is different.
> Jeff