re PR rtl-optimization/21254 (Incorrect code with -funroll-loops for multiple targets with same code)

	PR rtl-optimization/21254
	* loop-iv.c (iv_number_of_iterations): Simplify infiniteness
	assumptions for loops that otherwise do not roll.
	(find_simple_exit): Prefer # of iterations that is guaranteed
	not to be infinite.
	* loop-unroll.c (decide_peel_once_rolling,
	decide_peel_completely): Check whether the loop is infinite.

From-SVN: r99332