re PR target/82158 (_Noreturn functions that do return clobber caller's registers on ARM32 (but not other arches))

	PR target/82158
	* tree-cfg.c (pass_warn_function_return::execute): In noreturn
	functions when optimizing replace GIMPLE_RETURN stmts with
	calls to __builtin_unreachable ().

	* gcc.dg/tree-ssa/noreturn-1.c: New test.

From-SVN: r253926