Re: [PATCH 6/6] Devirtualization in ipa-cp

[Martin Jambor <mjambor@suse.cz>]

Hi,

On Mon, Feb 22, 2010 at 05:08:05PM +0100, Jan Hubicka wrote:
> > @@ -531,6 +537,16 @@ ipcp_cloning_candidate_p (struct cgraph_
> >    return true;
> >  }
> >  
> comments ;) How this is different from BOTTOM in the lattice?

I have added the missing comment.  cannot_devirtualize is basically
BOTTOM for devirtualization.  However these two are distinct values.

For example, sometimes we cannot propagate a constant because an
ADDR_EXPR of a local variable is passed in an argument, so the IPA-CP
lattice is BOTTOM, but we still can propagate the type for
devirtualization.  Or there may be different constants passed to a
function, again resulting to IPA-CP BOTTOM lattice for the parameter,
but we still might build and use a list of their types.  Conversely,
even if we propagate an IPA constant in IPA-CP, its type might not
have any BINFO associated with it and therefore we cannot use the
parameter for devirtualization.

> 
> The patch overall seems to make sense.  Please add describing
> comment on the top of ipa-cp as we are now diverging from classical
> ipa-cp formulation somewhat (but I can't seem to justify separate
> devirtualization pass that would do precisely the same as ipa-cp
> does but at types only)

Thanks, I have added that comment too and will resubmit the patches
soon.

Martin