* cgraph.h (symtab_node): Add nonzero_address.
	(decl_in_symtab_p): Break out from ...
	(symtab_get_node): ... here.
	* fold-const.c: Include cgraph.h
	(tree_single_nonzero_warnv_p): Use symtab to determine
	if symbol is non-zero.
	* symtab.c (symtab_node::nonzero_address): New method.

	* gcc.dg/pr36901.h: Simplify because non-zero symbol folding no
	longer happens during parsing.
	* gcc.dg/pr44024.c: Update template.
	* g++.dg/tree-ssa/nonzero-2.C: New testcase.
	* g++.dg/tree-ssa/nonzero-1.C: New testcase.
	* gcc.dg/tree-ssa/nonzero-1.c: New testcase.

From-SVN: r212499