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2 7u83 1 
/*
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 * Copyright (c) 2002-2005 The TenDRA Project <http://www.tendra.org/>.
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions are met:
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 *
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 * 1. Redistributions of source code must retain the above copyright notice,
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 *    this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright notice,
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 *    this list of conditions and the following disclaimer in the documentation
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 *    and/or other materials provided with the distribution.
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 * 3. Neither the name of The TenDRA Project nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific, prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS
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 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR
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 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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 * EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 *
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 * $Id$
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 */
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/*
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    		 Crown Copyright (c) 1997
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    This TenDRA(r) Computer Program is subject to Copyright
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    owned by the United Kingdom Secretary of State for Defence
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    acting through the Defence Evaluation and Research Agency
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    (DERA).  It is made available to Recipients with a
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    royalty-free licence for its use, reproduction, transfer
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    to other parties and amendment for any purpose not excluding
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    product development provided that any such use et cetera
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    shall be deemed to be acceptance of the following conditions:-
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        (1) Its Recipients shall ensure that this Notice is
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        reproduced upon any copies or amended versions of it;
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        (2) Any amended version of it shall be clearly marked to
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        show both the nature of and the organisation responsible
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        for the relevant amendment or amendments;
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        (3) Its onward transfer from a recipient to another
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        party shall be deemed to be that party's acceptance of
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        these conditions;
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        (4) DERA gives no warranty or assurance as to its
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        quality or suitability for any purpose and DERA accepts
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        no liability whatsoever in relation to any use to which
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        it may be put.
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*/
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/**********************************************************************
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$Author: release $
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$Date: 1998/01/17 15:55:47 $
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$Revision: 1.1.1.1 $
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$Log: label_ops.c,v $
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 * Revision 1.1.1.1  1998/01/17  15:55:47  release
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 * First version to be checked into rolling release.
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 *
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 * Revision 1.5  1997/08/06  10:58:32  currie
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 * Catch overflowed constants, PlumHall requirement
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 *
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 * Revision 1.4  1997/04/18  10:58:47  currie
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 * another pathelogical case
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 *
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 * Revision 1.3  1996/05/21  12:53:54  currie
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 * Pathological gotos
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 *
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 * Revision 1.2  1995/10/11  17:10:07  currie
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 * avs errors
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 *
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 * Revision 1.1  1995/04/06  10:44:05  currie
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 * Initial revision
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 *
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***********************************************************************/
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#include "config.h"
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#include "common_types.h"
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#include "expmacs.h"
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#include "tags.h"
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#include "label_ops.h"
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#include "check.h"
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#include "externs.h"
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#include "exp.h"
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#include "installglob.h"
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#include "shapemacs.h"
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/* label_is_next returns 1 if lab is a labst which immediately
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   follows e, otherwise 0. e will not be nilexp
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*/
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int
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label_is_next(exp lab, exp e)
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{
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	if (!indirect_jumps) {
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		return 0;
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	}
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	while (last(e)) {
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		e = bro(e);
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		if (e == nilexp || name(e) >= ass_tag || name(sh(e)) != bothd) {
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			return 0;
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		}
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	}
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	if (name(bro(e)) == labst_tag) {
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		return bro(e) == lab;
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	}
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	return 0;
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}
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static exp
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is_jumper(exp e)
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{
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	if (name(e) == test_tag || name(e) == goto_tag ||
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	    name(e) == testbit_tag || name(e) == res_tag) {
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		return e;
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	}
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	return nilexp;
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}
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static exp
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down(exp e)
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{
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	if (name(e) == seq_tag) {
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		return down(son(son(e)));
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	}
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	if (name(e) == cond_tag) {
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		return down(son(e));
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	}
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	return e;
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}
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/* next_jump delivers a goto, res, test or testbit exp if this
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   is certain to be the next thing obeyed after e. nilexp
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   otherwise.
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*/
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static exp
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next_jump(exp e)
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{
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	if (!indirect_jumps) {
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		return nilexp;
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	}
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	do {
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		while (last(e)) {
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			e = bro(e);
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			if (e == nilexp || name(e) >= goto_tag) {
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				return nilexp;
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			}
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		}
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		e = bro(e);
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	} while (name(e) == labst_tag && (e = father(e), name(e) !=rep_tag));
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	if (is_jumper(e)) {
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		return e;
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	}
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	if (name(e) == seq_tag || name(e) == cond_tag) {
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		return is_jumper(down(e));
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	}
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	if (name(e) == top_tag) {
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		return next_jump(e);
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	}
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	return nilexp;
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}
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/* next_jump delivers a goto, res, test or testbit exp if this
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   is certain to be the next thing obeyed after e and there is no
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   other route to the goto (etc.). nilexp otherwise.
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*/
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exp
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short_next_jump(exp e)
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{
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	if (!indirect_jumps) {
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		return nilexp;
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	}
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	while (last(e)) {
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		e = bro(e);
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		if (e == nilexp || name(e) >= cond_tag) {
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			return nilexp;
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		}
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	}
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	e = bro(e);
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	if (is_jumper(e)) {
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		return e;
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	}
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	if (name(e) == seq_tag || name(e) == cond_tag) {
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		return is_jumper(down(e));
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	}
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	if (name(e) == top_tag) {
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		return short_next_jump(e);
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	}
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	return nilexp;
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}
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exp
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jump_dest(exp lab)
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{
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	return next_jump(son(lab));
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}
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exp
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final_dest(exp lab)
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{
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	exp final = lab;
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	exp temp, ll;
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	while (name(final) == labst_tag) {
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		temp = jump_dest(final);
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		if (temp != nilexp && name(temp) == goto_tag &&
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		    pt(temp) != final) {
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			ll = lab;
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			while (ll != final) {
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				if (pt(temp) == ll) {
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					/* pathological loop */
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					return final;
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				}
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				ll = pt(jump_dest(ll));
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			}
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			final = pt(temp);
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		} else {
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			break;
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		}
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	}
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	return final;
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}
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/* delivers 1 iff when a jumps, b also jumps
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   a and b will be test or testbit */
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static int
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subsumes(exp a, exp b)
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{
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	if (name(a) == name(b) && test_number(a) == test_number(b) &&
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	    eq_exp(son(a), son(b)) && eq_exp(bro(son(a)), bro(son(b)))) {
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		return 1;
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	}
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	return 0;
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}
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exp
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final_dest_test(exp lab, exp e)
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{
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	exp final = lab;
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	exp temp, ll;
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	while (name(final) == labst_tag) {
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		temp = jump_dest(final);
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		if (temp == nilexp || final == pt(temp)) {
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			return final;
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		}
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		if (name(temp) == goto_tag ||
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		    (name(temp) == name(e) && subsumes(e, temp))) {
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			ll = lab;
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			while (ll != final) {
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				if (pt(temp) == ll) {
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					/* pathological loop */
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					return final;
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				}
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				ll = pt(jump_dest(ll));
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			}
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			final = pt(temp);
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		} else {
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			break;
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		}
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	}
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	return final;
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}