tree-vrp.c (vrp_expr_computes_nonnegative): Remove.

2011-08-04  Richard Guenther  <rguenther@suse.de>

	* tree-vrp.c (vrp_expr_computes_nonnegative): Remove.
	(value_range_nonnegative_p): New function.
	(ssa_name_nonnegative_p): Use it.
	(value_range_constant_singleton): New function.
	(op_with_constant_singleton_value_range): Use it.
	(extract_range_from_binary_expr_1): New function, split out from ...
	(extract_range_from_binary_expr): ... this.  Remove fallback
	constant folding done here.

From-SVN: r177393