tree-ssa.c (find_released_ssa_name): Handle NULL wi.

* tree-ssa.c (find_released_ssa_name): Handle NULL wi.
(insert_debug_temp_for_var_def): Handle degenerate PHI nodes.
(insert_debug_temps_for_defs): Handle PHI nodes.
* tree-ssa-dom.c (degenerate_phi_result): Don't crash on released
SSA names.

From-SVN: r154402