re PR middle-end/53676 (empty loop is not always removed now)

re PR middle-end/53676 (empty loop is not always removed now)

2012-06-27  Richard Guenther  <rguenther@suse.de>

	PR middle-end/53676
	* tree-chrec.c (chrec_convert_1): Represent truncation to
	a type with undefined overflow as truncation to an unsigned
	type converted to the type with undefined overflow.
	* tree-scalar-evolution.c (interpret_rhs_expr): For computing
	the scalar evolution of a truncated widened operation avoid
	looking at the non-existing evolution of the widened operation
	result.

	* gcc.dg/tree-ssa/scev-6.c: New testcase.

From-SVN: r189013