* tree-dfa.c (collect_dfa_stats): Simplify.
* tree-ssa-structalias.c (compute_may_aliases): Do not dump
referenced vars.
* cfgexpand.c (estimated_stack_frame_size): Walk over local
decls instead of referenced vars.
* tree-ssa.c (delete_tree_ssa): Simplify.
* tree-tailcall.c (find_tail_calls): Walk over local decls
instead of referenced vars.
(add_virtual_phis): Remove.
(tree_optimize_tail_calls_1): Instead mark the virtual operand
for renaming.