2013-10-17  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/58143
	* tree-ssa-loop-im.c (arith_code_with_undefined_signed_overflow):
	New function.
	(rewrite_to_defined_overflow): Likewise.
	(move_computations_dom_walker::before_dom): Rewrite stmts
	with undefined signed overflow that are not always executed
	into unsigned arithmetic.

	* gcc.dg/torture/pr58143-1.c: New testcase.
	* gcc.dg/torture/pr58143-2.c: Likewise.
	* gcc.dg/torture/pr58143-3.c: Likewise.

From-SVN: r203745