2006-01-11  Ian Lance Taylor <ian@airs.com>

	* combine.c (struct undo): Remove is_int.  Enumify types of undos.
	Allow undoing set of machine mode.
	(do_SUBST): Use enums instead of is_int.
	(do_SUBST_MODE): New function.
	(SUBST_MODE): New macro.
	(try_combine): Use SUBST_MODE/PUT_MODE instead of generating a new
	reg and trying to replace reg_regno_rtx with a new register.
	(undo_all): Use new enums, handle undoing a PUT_MODE change.
	(simplify_set): Use SUBST_MODE.
	(distribute_notes): Remove code that tried to update reg notes
	for regno_reg_rtx changes.

From-SVN: r109579