make use of CALL_FROM_NEW_OR_DELETE_P

make use of CALL_FROM_NEW_OR_DELETE_P

This fixes points-to analysis and DCE to only consider new/delete
operator calls from new or delete expressions and not direct calls.

2020-10-01  Richard Biener  <rguenther@suse.de>

	* gimple.h (GF_CALL_FROM_NEW_OR_DELETE): New call flag.
	(gimple_call_set_from_new_or_delete): New.
	(gimple_call_from_new_or_delete): Likewise.
	* gimple.c (gimple_build_call_from_tree): Set
	GF_CALL_FROM_NEW_OR_DELETE appropriately.
	* ipa-icf-gimple.c (func_checker::compare_gimple_call):
	Compare gimple_call_from_new_or_delete.
	* tree-ssa-dce.c (mark_all_reaching_defs_necessary_1): Make
	sure to only consider new/delete calls from new or delete
	expressions.
	(propagate_necessity): Likewise.
	(eliminate_unnecessary_stmts): Likewise.
	* tree-ssa-structalias.c (find_func_aliases_for_call):
	Likewise.

	* g++.dg/tree-ssa/pta-delete-1.C: New testcase.