* regrename.c (struct du_head): Make nregs signed.
	(closed_chains): Remove.
	(create_new_chain): Return the new chain.
	(chain_from_id): New static function.
	(dump_def_use_chain): Change argument to be an int, indicating
	the first ID to print.  All callers changed.
	(merge_overlapping_regs): Use chain_from_id.  Assert that
	chains don't conflict with themselves.
	(rename_chains): Take no argument.  Iterate over id_to_chain
	rather to find chains to rename.  Clear tick before the main
	loop.
	(struct incoming_reg_info): New struct.
	(struct bb_rename_info): New struct.
	(init_rename_info, set_incoming_from_chain, merge_chains): New
	static functions.
	(regrename_analyze): New static function, broken out of
	regrename_optimize.  Record and make use of open chain information
	at basic block boundaries, and merge chains where possible.
	(scan_rtx_reg): Make this_nregs signed.  Don't update
	closed_chains.
	(build_def_use): Return a bool to indicate success.  All callers
	changed.  Don't initialize global data here.
	(regrename_optimize): Move most code out of here into
	regrename_analyze.
	* regs.h (add_range_to_hard_reg_set, remove_range_from_hard_reg_set,
	range_overlaps_hard_reg_set_p, range_in_hard_reg_set_p): New
	static inline functions.
	* vec.h (FOR_EACH_VEC_ELT_FROM): New macro.

From-SVN: r178645