re PR middle-end/38474 (compile time explosion in dataflow_set_preserve_mem_locs...

re PR middle-end/38474 (compile time explosion in dataflow_set_preserve_mem_locs at -O3)

	PR middle-end/38474
	* cfgexpand.c (struct stack_var): Add conflicts member.
	(stack_vars_conflict, stack_vars_conflict_alloc,
	n_stack_vars_conflict): Remove.
	(add_stack_var): Initialize conflicts member.
	(triangular_index, resize_stack_vars_conflict): Remove.
	(add_stack_var_conflict, stack_var_conflict_p): Rewrite in
	terms of new member.
	(union_stack_vars): Only run over the conflicts.
	(partition_stack_vars): Remove special case.
	(expand_used_vars_for_block): Don't call resize_stack_vars_conflict,
	don't create self-conflicts.
	(account_used_vars_for_block): Don't create any conflicts.
	(fini_vars_expansion): Free bitmaps, don't free or clear removed
	globals.

From-SVN: r154945