* var-tracking.c (remove_cselib_value_chains): Define only for
ENABLE_CHECKING.
(dataflow_set_preserve_mem_locs, dataflow_set_remove_mem_locs,
delete_slot_part, emit_notes_for_differences_1): Don't call
remove_cselib_value_chains here.
(set_slot_part, emit_notes_for_differences_2): Don't call
add_cselib_value_chains here.
(preserved_values): New vector.
(preserve_value): New function.
(add_uses, add_stores, vt_add_function_parameters): Use it
instead of cselib_preserve_value.
(changed_values_stack): New vector.
(check_changed_vars_0): New function.
(check_changed_vars_1, check_changed_vars_2): Use it.
(emit_notes_for_changes): Call set_dv_changed (*, false) on all
changed_values_stack VALUEs.
(vt_emit_notes): For all preserved_values call
add_cselib_value_chains. If ENABLE_CHECKING call
remove_cselib_value_chains before verifying value_chains is empty.
Initialize and free changed_values_stack.
(vt_initialize): Initialize preserved_values.
(vt_finalize): Free preserved_values.
From-SVN: r157277
