* function.c (bb_active_p): Delete.
	(dup_block_and_redirect, active_insn_between): New functions.
	(convert_jumps_to_returns, emit_return_for_exit): New functions,
	split out from..
	(thread_prologue_and_epilogue_insns): ..here.  Delete
	shadowing variables.  Don't do prologue register clobber tests
	when shrink wrapping already failed.  Delete all last_bb_active
	code.  Instead compute tail block candidates for duplicating
	exit path.  Remove these from antic set.  Duplicate tails when
	reached from both blocks needing a prologue/epilogue and
	blocks not needing such.
	* ifcvt.c (dead_or_predicable): Test both flag_shrink_wrap and
	HAVE_simple_return.
	* bb-reorder.c (get_uncond_jump_length): Make global.
	* bb-reorder.h (get_uncond_jump_length): Declare.
	* cfgrtl.c (rtl_create_basic_block): Comment typo fix.
	(rtl_split_edge): Likewise.  Warning fix.
	(rtl_duplicate_bb): New function.
	(rtl_cfg_hooks): Enable can_duplicate_block_p and duplicate_block.
	* Makefile.in (function.o): Update dependencies.

From-SVN: r181188