[tuples] fix thinkos in forwprop

[Andrew Pinski]

On Mon, Jun 30, 2008 at 3:12 PM, Aldy Hernandez <aldyh@redhat.com> wrote:
> fold_binary was returning NULL because it couldn't do anything with a
> testcase I found while boostrapping.  I guess I could check the return
> value from fold_binary-- and use build2 if fold_binary returns NULL.

Or better just use fold_build2 which does that already :).

-- Pinski