re PR tree-optimization/91351 (-fstrict-enums generates incorrect code)

re PR tree-optimization/91351 (-fstrict-enums generates incorrect code)

	PR tree-optimization/91351
	* tree-cfg.c (generate_range_test): Use range_check_type instead of
	unsigned_type_for.
	* tree-cfgcleanup.c (convert_single_case_switch): Punt if
	range_check_type returns NULL.
	* tree-switch-conversion.c (switch_conversion::build_one_array):
	Use range_check_type instead of unsigned_type_for, don't perform
	linear opt if it returns NULL.
	(bit_test_cluster::find_bit_tests): Formatting fix.
	(bit_test_cluster::emit): Use range_check_type instead of
	unsigned_type_for.
	(switch_decision_tree::try_switch_expansion): Punt if range_check_type
	returns NULL.

	* g++.dg/opt/pr91351.C: New test.

From-SVN: r275026