re PR libstdc++/29286 (placement new does not change the dynamic type as it should)

re PR libstdc++/29286 (placement new does not change the dynamic type as it should)

./:	PR libstdc++/29286
	* tree.def: Add CHANGE_DYNAMIC_TYPE_EXPR.
	* tree.h (CHANGE_DYNAMIC_TYPE_NEW_TYPE): Define.
	(CHANGE_DYNAMIC_TYPE_LOCATION): Define.
	(DECL_NO_TBAA_P): Define.
	(struct tree_decl_common): Add no_tbaa_flag field.
	* tree-ssa-structalias.c (struct variable_info): Add
	no_tbaa_pruning field.
	(new_var_info): Initialize no_tbaa_pruning field.
	(unify_nodes): Copy no_tbaa_pruning field.
	(find_func_aliases): Handle CHANGE_DYNAMIC_TYPE_EXPR.
	(dump_solution_for_var): Print no_tbaa_pruning flag.
	(set_uids_in_ptset): Add no_tbaa_pruning parameter.  Change all
	callers.
	(compute_tbaa_pruning): New static function.
	(compute_points_to_sets): Remove CHANGE_DYNAMIC_TYPE_EXPR nodes.
	Call compute_tbaa_pruning.
	* tree-ssa-alias.c (may_alias_p): Test no_tbaa_flag for pointers.
	* gimplify.c (gimplify_expr): Handle CHANGE_DYNAMIC_TYPE_EXPR.
	* gimple-low.c (lower_stmt): Likewise.
	* tree-gimple.c (is_gimple_stmt): Likewise.
	* tree-ssa-operands.c (get_expr_operands): Likewise.
	* tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Likewise.
	* tree-inline.c (estimate_num_insns_1): Likewise.
	(copy_result_decl_to_var): Likewise.
	* expr.c (expand_expr_real_1): Likewise.
	* tree-pretty-print.c (dump_generic_node): Likewise.
	* tree-inline.c (copy_decl_to_var): Copy DECL_NO_TBAA_P flag.
	* omp-low.c (omp_copy_decl_2): Likewise.
	* print-tree.c (print_node): Print DECL_NO_TBAA_P flag.
	* doc/c-tree.texi (Expression trees): Document
	CHANGE_DYNAMIC_TYPE_EXPR.
cp/:
	PR libstdc++/29286
	* init.c (avoid_placement_new_aliasing): New static function.
	(build_new_1): Call it.
testsuite/:
	PR libstdc++/29286
	* g++.dg/init/new16.C: New test.
	* g++.dg/init/new17.C: New test.
	* g++.dg/init/new18.C: New test.
	* g++.dg/init/new19.C: New test.

Co-Authored-By: Daniel Berlin <dberlin@dberlin.org>
From-SVN: r125653