[tuples] convert forwprop

[Aldy Hernandez]

> > +  /* FIXME tuples: I'm not sure why this is needed, but mainline had it. */
> > +  if (TREE_CODE_LENGTH (gimple_subcode (def_stmt)) == 0)
> > +    return false;
> 
> Definitely not needed.  The trunk should have gotten sth like this:

Removed, thanks.

> > -    default:
> > +  /* We cannot propagate ssa names that occur in abnormal phi nodes.  */
> > +  FOR_EACH_SSA_USE_OPERAND (use_p, def_stmt, iter, SSA_OP_USE)
> > +    if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (use_p)))
> >       return false;
> > -    }
> 
> as well.

Are you saying we should remove this as well?

> Well - the propagation into GIMPLE_CONDs (that's the ones ending BBs, right?)
> are definitely very important.  But yes, folding is getting ugly with
> tuples -- you'll
> notice when you are converting SCCVN as well.

Definitely ugly.  We need two versions because of GIMPLE_COND's
(statements), and COND_EXPRs (as expressions) in a GIMPLE_ASSIGN.  Right
now we never generate COND_EXPRs as an operand to a GIMPLE_ASSIGN, but
only because we haven't converted the if-conversion pass yet.

Thank you so much for reviewing this.
Aldy