re PR tree-optimization/71691 (wrong code at -O3 in both 32-bit and 64-bit modes on x86_64-linux-gnu (Floating point exception))

	PR tree-optimization/71691
	* bitmap.h (class auto_bitmap): New.
	* tree-ssa-loop-unswitch.c (tree_may_unswitch_on): Call
	is_maybe_undefined instead of ssa_undefined_value_p.

From-SVN: r245057