/*
insn_rel.c
Copyright © 2009 William Astle

This file is part of LWASM.

LWASM 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/>.
*/

/*
for handling relative mode instructions
*/

#define __insn_rel_c_seen__
#include <config.h>
#include <stdlib.h>

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

OPFUNC(insn_rel8)
{
	int v;
	lwasm_expr_term_t *t;
	int r;
	
	lwasm_emitop(as, l, instab[opnum].ops[0]);

	if (**p == '#')
		(*p)++;

	if ((r = lwasm_expr_result2(as, l, p, EXPR_SECTCONST, &v, 0)) < 0)
		v = 0;
	else
	{
		if (as -> passnum == 1)
		{
			// need to adjust the expression
			if (l -> exprs[0])
			{
				t = lwasm_expr_term_create_int(as -> addr + 1);
				lwasm_expr_stack_push(l -> exprs[0], t);
				lwasm_expr_term_free(t);
				t = lwasm_expr_term_create_oper(LWASM_OPER_MINUS);
				lwasm_expr_stack_push(l -> exprs[0], t);
				lwasm_expr_term_free(t);
			}
			else
			{
				l -> exprvals[0] -= as -> addr + 1;
			}
		}
	}
	if (r == 1 && as -> passnum == 2)
	{
		register_error(as, l, 2, "Illegal external or intersegment reference");
	}
	if (v < -128 || v > 127)
		register_error(as, l, 2, "Byte overflow");
	lwasm_emit(as, l, v & 0xff);
}

/*
External and intersegment references are adjusted for the relative addressing mode
by adjusting the expression on pass 1 and then treated as absolute references later
*/
OPFUNC(insn_rel16)
{
	int v;
	int r;
	lwasm_expr_term_t *t;
	
	lwasm_emitop(as, l, instab[opnum].ops[0]);
	
	if (**p == '#')
		(*p)++;

	r = lwasm_expr_result2(as, l, p, EXPR_SECTCONST, &v, 0);
	if (r < 0)
		v = 0;
	else
	{
		if (as -> passnum == 1)
		{
			// need to adjust the expression
			if (l -> exprs[0])
			{
				t = lwasm_expr_term_create_int(as -> addr + 2);
				lwasm_expr_stack_push(l -> exprs[0], t);
				lwasm_expr_term_free(t);
				t = lwasm_expr_term_create_oper(LWASM_OPER_MINUS);
				lwasm_expr_stack_push(l -> exprs[0], t);
				lwasm_expr_term_free(t);
			}
			else
			{
				l -> exprvals[0] -= as -> addr + 2;
			}
		}
	}
	if (as -> passnum == 2 && r == 1)
	{
		// since we have a reference outside this section, add
		// a subtract of the section base to get the right value
		// upon linking
		t = lwasm_expr_term_create_secbase();
		lwasm_expr_stack_push(l -> exprs[0], t);
		lwasm_expr_term_free(t);
		t = lwasm_expr_term_create_oper(LWASM_OPER_MINUS);
		lwasm_expr_stack_push(l -> exprs[0], t);
		lwasm_expr_term_free(t);

		l -> relocoff = as -> addr - l -> codeaddr;
	}
	lwasm_emit(as, l, (v >> 8) & 0xff);
	lwasm_emit(as, l, v & 0xff);
}