* tree-vrp.h (value_range_base::nonzero_p): New.
	(value_range_base::set_nonnull): Rename to...
	(value_range_base::set_nonzero): ...this.
	(value_range_base::set_null): Rename to...
	(value_range_base::set_zero): ...this.
	(value_range::set_nonnull): Remove.
	(value_range::set_null): Remove.
	* tree-vrp.c (range_is_null): Remove.
	(range_is_nonnull): Remove.
	(extract_range_from_binary_expr): Use value_range_base::*zero_p
	instead of range_is_*null.
	(extract_range_from_unary_expr): Same.
	(value_range_base::set_nonnull): Rename to...
	(value_range_base::set_nonzero): ...this.
	(value_range::set_nonnull): Remove.
	(value_range_base::set_null): Rename to...
	(value_range_base::set_zero): ...this.
	(value_range::set_null): Remove.
	(extract_range_from_binary_expr): Rename set_*null uses to
	set_*zero.
	(extract_range_from_unary_expr): Same.
	(union_helper): Same.
	* vr-values.c (get_value_range): Use set_*zero instead of
	set_*null.
	(vr_values::extract_range_from_binary_expr): Same.
	(vr_values::extract_range_basic): Same.

From-SVN: r271865