re PR tree-optimization/20216 (Simple loop runs out of stack at -O1)

re PR tree-optimization/20216 (Simple loop runs out of stack at -O1)

	PR tree-optimization/20216
	* tree-chrec.c (tree_fold_factorial): Delete.
	(tree_fold_binomial): Change argument list to take a return type
	and change the type of K to unsigned int.  Rewrite to avoid explicit
	evaluation of factorials, and (recursively) calling fold to perform
	compile-time arithmetic.  Return NULL on (internal) overflow.
	(chrec_evaluate): Change type of K to an unsigned int.  Avoid
	calling tree_fold_binomial unnecessarily.  Return chrec_dont_know
	if any intermediate calculation overflows.
	(chrec_apply): Update call to chrec_evaluate.

From-SVN: r95722