/*
insn_tfm.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 inherent mode instructions
*/

#define __insn_tfm_c_seen__

#include <ctype.h>
#include <string.h>

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

OPFUNC(insn_tfm)
{
	static const char *reglist = "DXYUS   AB  00EF";
	int r0, r1;
	char *c;
	int tfm = 0;
			
	c = strchr(reglist, toupper(*(*p)++));
	if (!c)
	{
		register_error(as, l, 1, "Unknown operation");
		return;
	}
	r0 = c - reglist;
	if (**p == '+')
	{
		(*p)++;
		tfm = 1;
	}
	else if (**p == '-')
	{
		(*p)++;
		tfm = 2;
	}
	if (*(*p)++ != ',')
	{
		register_error(as, l, 1, "Unknown operation");
		return;
	}
	c = strchr(reglist, toupper(*(*p)++));
	if (!c)
	{
		register_error(as, l, 1, "Unknown operation");
		return;
	}
	r1 = c - reglist;

	if (**p == '+')
	{
		(*p)++;
		tfm |= 4;
	}
	else if (**p == '-')
	{
		(*p)++;
		tfm |= 8;
	}
	
	if (**p && !isspace(**p))
	{
		register_error(as, l, 1, "Bad operand");
		return;
	}
			
	// valid values of tfm here are:
	// 1: r0+,r1 (2)
	// 4: r0,r1+ (3)
	// 5: r0+,r1+ (0)
	// 10: r0-,r1- (1)
	switch (tfm)
	{
	case 5: //r0+,r1+
		lwasm_emitop(as, l, instab[opnum].ops[0]);
		break;
	case 10: //r0-,r1-
		lwasm_emitop(as, l, instab[opnum].ops[1]);
		break;
	case 1: // r0+,r1
		lwasm_emitop(as, l, instab[opnum].ops[2]);
		break;
	case 4: // r0,r1+
		lwasm_emitop(as, l, instab[opnum].ops[3]);
		break;
	default:
		register_error(as, l, 1, "Unknown operation");
		return;
	}
	lwasm_emit(as, l, (r0 << 4) | r1);
}