PR rtl-optimization/84872
	* cfgloopmanip.c (create_preheader): Use make_forwarder_block even if
	nentry == 1 when CP_FALLTHRU_PREHEADERS and single_entry is
	EDGE_CROSSING edge.

	* gcc.dg/graphite/pr84872.c: New test.

From-SVN: r259182