re PR debug/47106 (-fcompare-debug failure (length) with  -fpartial-inlining -flto -fconserve-stack)

PR debug/47106
* cfgexpand.c (account_used_vars_for_block): Only account vars
that are annotated as used.
(estimated_stack_frame_size): Don't set TREE_USED.
* tree-dfa.c (create_var_ann): Mark variable as used.

From-SVN: r169093