re PR middle-end/54146 (Very slow compile with attribute((flatten)))

re PR middle-end/54146 (Very slow compile with attribute((flatten)))

	PR tree-optimization/54146
	* cfgexpand.c (add_scope_conflicts_1): Use bitmap_ior_into.
	(add_scope_conflicts): Iterate in RPO order.
	(add_stack_protection_conflicts): Iterate over the other triangle.
	(fini_vars_expansion): Clear stack_vars_sorted.

From-SVN: r190126