Re: Moving statements from one BB to other BB.

["Sandeep Maram" <sandeep244 at gmail dot com>]

On Tue, Apr 15, 2008 at 11:40 PM, Diego Novillo <dnovillo@google.com> wrote:
>
> On 4/15/08 1:34 PM, Zdenek Dvorak wrote:
>
> > Hi,
> >
> >
> > >
> > > >  > To clarify what Richard means, your assertion that "you have
> updated
> > > >  > SSA information" is false.
> > > >  > If you had updated the SSA information, the error would not occur
> :).
> > > >  >
> > > >  > How exactly are you updating the ssa information?
> > > >  >
> > > >  > The general way to update SSA for this case would be:
> > > >  >
> > > >  > For each statement you have moved:
> > > >  >   Call update_stmt (t);
> > > >  >
> > > >  > Then call update_ssa (TODO_update_ssa) (or instead use
> > > >  > rewrite_into_loop_closed_ssa if this is a loop pass).
> > > >  >
> > > >  > If you do not call update_stmt in this case, update_ssa won't
> actually
> > > >  > do anything.
> > > >
> > > >  actually, it will not do anything even if he calls update_stmt, as
> the
> > > >  statements that he is moving are already in ssa form, so update_stmt
> > > >  will not mark anything for renaming.
> > > >
> > > >
> > > You are partially right (and right where it matters, that it won't fix
> > > the problem)
> > > That said, update_stmt on ssa form statements will at least reset the
> > > vuse/vdef back to original variables for renaming.
> > >
> >
> > I don't think so; as long as you do not introduce new vops (which you
> > should not by just moving the statements), update_stmt is a no-op on
> > vops too (unless something has changed since the last time I needed
> > this),
> >
>
>  Right.  Moving statements in SSA form needs to introduce name->name
> mappings (eg, as is done during loop unrolling).
>

Yes, calling update_stmt for evry transfer and then calling update_ssa
later, didn't work. From the discussions, I understood that I have to
change the SSA names in the statements to be transfered, to the
corresponding SSA names in the destination block. Can you please tell
me , whether there are any functions that manipulate the SSA names ?

Thanks,
Sandeep.

>
>  Diego.
>