* basic-block.h (could_fall_through): Declare.
	* cfganal.c (can_fallthru): Succeed if the target is EXIT_BLOCK_PTR.
	Fail if the source already has a fallthrough edge to the exit
	block pointer.
	(could_fall_through): New function.
	* cfgbuild.c (make_edges): Check if we already have a fallthrough
	edge to the exit block pointer.
	* cfglayout.c (fixup_fallthru_exit_predecessor): Check that it is
	not called before reload has completed.
	Handle special case of first block having a fall-through exit edge.
	(cfg_layout_finalize): Don't call it before reload or if we have
	rtl epilogues.
	(fixup_reorder_chain): A fall through to the exit block does not
	require the block to come last.  Add sanity checks.
	* cfgrtl.c (rtl_split_edge): Add special handling of fall through
	edges to the exit block.
	* function.c (cfglayout.h): #include.
	(thread_prologue_and_epilogue_insns): If we have neither return nor
	epilogue, but a fall through to the exit block from mid-function,
	force a non-fall-through exit.
	* Makefile.in (function.o): Depend on CFGLAYOUT_H.

From-SVN: r83089