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Re: Minor CCP improvement and add comments to tree.h
On Wed, 2004-09-22 at 08:11, Daniel Berlin wrote:
> 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.
OK.
> For other equivalences, a value handle is different.
Can you give me an example or two?
jeff