view lwasm/pass5.c @ 434:052c5f335a92

Fix bug in like terms collection in expression simplification Like term collection would lose the actual "variable" part of the term if the second term collected happened to have no coefficient. This would cause the expression to take the value of the calculated coefficient which is obviously wrong. Thanks to hider <stego@satx.rr.com> for reporting the bug and providing a proper test case. Observation: this bug has been present since the first pre-release of lwtools 3.0 when the algebraic expression system was introduced. Apparently people tend not to create expressions that trigger the like terms handler. The specific conditions require the symbol to be undefined and the second operand to the addition has to have no coefficient so it's likely a fairly rare scenario. Still, it is somewhat surprising that nobody tripped on it before now.
author William Astle <lost@l-w.ca>
date Mon, 23 Jan 2017 22:58:36 -0700
parents 58cafa61ab40
children
line wrap: on
line source

/*
pass5.c

Copyright © 2010 William Astle

This file is part of LWTOOLS.

LWTOOLS is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.

You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.
*/

#include <stdio.h>
#include <string.h>

#include <lw_alloc.h>
#include <lw_string.h>

#include "lwasm.h"
#include "instab.h"

/*
AssignAddresses Pass

Force resolution of all line addresses

*/

static int exprok_aux(lw_expr_t e, void *priv)
{
	asmstate_t *as = priv;
	
	if (lw_expr_istype(e, lw_expr_type_int))
		return 0;
	if (lw_expr_istype(e, lw_expr_type_oper))
		return 0;
	if (lw_expr_istype(e, lw_expr_type_special) && (as -> output_format == OUTPUT_OBJ || as -> output_format == OUTPUT_LWMOD))
	{
		int t;
		t = lw_expr_specint(e);
		if (t == lwasm_expr_secbase)
			return 0;
	}
	
	return 1;
}

static int exprok(asmstate_t *as, lw_expr_t e)
{
	if (lw_expr_testterms(e, exprok_aux, as))
		return 0;
	return 1;
}

void do_pass5(asmstate_t *as)
{
//	int rc;
	int cnt;
	int ocnt;
	line_t *cl, *sl;
//	struct line_expr_s *le;

	// first, count the number of non-constant addresses; do
	// a reduction first on each one
	for (cnt = 0, cl = as -> line_head; cl; cl = cl -> next)
	{
		as -> cl = cl;
		lwasm_reduce_expr(as, cl -> addr);
		if (!exprok(as, cl -> addr))
			cnt++;
		lwasm_reduce_expr(as, cl -> daddr);
		if (!exprok(as, cl -> daddr))
			cnt++;
	}

	sl = as -> line_head;
	while (cnt > 0)
	{
		ocnt = cnt;
		
		// find an unresolved address
		for ( ; sl && exprok(as, sl -> addr) && exprok(as, sl -> daddr); sl = sl -> next)
			/* do nothing */ ;

		// simplify address
		for (cl = sl; cl; cl = cl -> next)
		{
			as -> cl = sl;
			lwasm_reduce_expr(as, sl -> addr);
		
			if (exprok(as, cl -> addr))
			{
				if (0 == --cnt)
					return;
			}
			lwasm_reduce_expr(as, sl -> daddr);
			if (exprok(as, cl -> addr))
			{
				if (0 == --cnt)
					return;
			}
		}
		
		if (cnt == ocnt)
			break;
	}
	
	if (cnt)
	{
		// we have non-resolved line addresses here
		for (cl = sl; cl; cl = cl -> next)
		{
			if (!exprok(as, cl -> addr))
			{
				lwasm_register_error(as, cl, E_LINE_ADDRESS);
			}
			if (!exprok(as, cl -> daddr))
			{
				lwasm_register_error(as, cl, E_LINED_ADDRESS);
			}
		}
	}
}