2012-04-12  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/52943
	* tree-chrec.h (chrec_is_positive): Remove.
	* tree-scalar-evolution.c (chrec_is_positive): Move ...
	* tree-data-ref.c (chrec_is_positive): ... here.  Make static.
	Return false for a constant zero instead of negative.
	(analyze_siv_subscript_cst_affine): Handle zero difference
	in the initial condition explicitely.

	* gcc.dg/torture/pr52943.c: New testcase.

From-SVN: r186374