/*
	dags.c

	DAG representation of basic blocks

	Copyright (C) 2012 Bill Currie <bill@taniwha.org>

	Author: Bill Currie <bill@taniwha.org>
	Date: 2012/05/08

	This program 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 2
	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, write to:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#ifdef HAVE_STRING_H
# include <string.h>
#endif
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif
#include <stdlib.h>

#include "QF/dstring.h"

#include "dags.h"
#include "diagnostic.h"
#include "qfcc.h"
#include "statements.h"
#include "strpool.h"
#include "symtab.h"

static daglabel_t *free_labels;
static dagnode_t *free_nodes;

static daglabel_t *daglabel_chain;

static void
flush_daglabels (void)
{
	while (daglabel_chain) {
		operand_t  *op;

		if ((op = daglabel_chain->op)) {
			while (op->op_type == op_alias)
				op = op->o.alias;
			if (op->op_type == op_symbol)
				op->o.symbol->daglabel = 0;
			else if (op->op_type == op_temp)
				op->o.tempop.daglabel = 0;
			else if (op->op_type == op_value || op->op_type == op_pointer)
				op->o.value->daglabel = 0;
			else
				internal_error (0, "unexpected operand type");
		}
		daglabel_chain = daglabel_chain->daglabel_chain;
	}
}

static daglabel_t *
new_label (void)
{
	daglabel_t *label;
	ALLOC (256, daglabel_t, labels, label);
	label->daglabel_chain = daglabel_chain;
	daglabel_chain = label;
	return label;
}

static dagnode_t *
new_node (void)
{
	dagnode_t *node;
	ALLOC (256, dagnode_t, nodes, node);
	return node;
}

const char *
daglabel_string (daglabel_t *label)
{
	static dstring_t *str;
	if ((label->opcode && label->op) || (!label->opcode && !label->op))
		return "bad label";
	if (label->opcode)
		return label->opcode;
	if (!str)
		str = dstring_new ();
	// operand_string might use quote_string, which returns a pointer to
	// a static variable.
	dstring_copystr (str, operand_string (label->op));
	return quote_string (str->str);
}

static daglabel_t *
opcode_label (const char *opcode)
{
	daglabel_t *label;

	label = new_label ();
	label->opcode = opcode;
	return label;
}

static daglabel_t *
operand_label (operand_t *op)
{
	operand_t  *o;
	symbol_t   *sym = 0;
	ex_value_t *val = 0;
	daglabel_t *label;

	if (!op)
		return 0;
	o = op;
	while (o->op_type == op_alias)
		o = o->o.alias;

	if (o->op_type == op_temp) {
		label = new_label ();
		label->op = op;
		o->o.tempop.daglabel = label;
	} else if (o->op_type == op_symbol) {
		sym = o->o.symbol;
		if (sym->daglabel)
			return sym->daglabel;
		label = new_label ();
		label->op = op;
		sym->daglabel = label;
	} else if (o->op_type == op_value || o->op_type == op_pointer) {
		val = o->o.value;
		if (val->daglabel)
			return val->daglabel;
		label = new_label ();
		label->op = op;
		val->daglabel = label;
	} else {
		internal_error (0, "unexpected operand type: %d", o->op_type);
	}
	return label;
}

static dagnode_t *
leaf_node (operand_t *op)
{
	daglabel_t *label;
	dagnode_t  *node;

	if (!op)
		return 0;
	label = operand_label (op);
	node = new_node ();
	node->label = label;
	label->dagnode = node;
	return node;
}

static dagnode_t *
node (operand_t *op)
{
	operand_t  *o;
	symbol_t   *sym;

	if (!op)
		return 0;
	o = op;
	while (o->op_type == op_alias)
		o = o->o.alias;
	if (o->op_type == op_symbol) {
		sym = o->o.symbol;
		if (sym->sy_type == sy_const)
			return 0;
		if (sym->daglabel)
			return sym->daglabel->dagnode;
	} else if (o->op_type == op_temp) {
		if (o->o.tempop.daglabel)
			return o->o.tempop.daglabel->dagnode;
	}
	return 0;
}

static int
find_operands (statement_t *s, operand_t **x, operand_t **y, operand_t **z,
			   operand_t **w)
{
	int         simp = 0;

	if (s->opc) {
		*y = s->opa;
		if (s->opb) {
			// except for move, indexed pointer store, rcall2+, and state,
			// all are of the form c = a op b
			*z = s->opb;
			if (!strncmp (s->opcode, "<MOVE", 5)
				|| !strncmp (s->opcode, "<RCALL", 6)
				|| !strcmp (s->opcode, "<STATE>")
				|| !strcmp (s->opcode, ".=")) {
				*w = s->opc;
			} else {
				*x = s->opc;
			}
		} else {
			// these are all c = op a
			*x = s->opc;
		}
	} else if (s->opb) {
		*y = s->opa;
		if (s->opcode[1] == 'I') {
			// conditional
		} else if (s->opcode[0] == '<' || s->opcode[0] == '.') {
			// pointer store or branch
			*z = s->opb;
		} else {
			// b = a
			*x = s->opb;
			simp = 1;
		}
	} else if (s->opa) {
		if (s->opcode[1] == 'G') {
		} else {
			*y = s->opa;
			if (s->opcode[1] == 'R')
				simp = 1;
		}
	}
	return simp;
}

static int
dagnode_match (const dagnode_t *n, const daglabel_t *op,
			   const dagnode_t *y, const dagnode_t *z, const dagnode_t *w)
{
	if (n->label->opcode != op->opcode)
		return 0;
	if (n->a && y && n->a->label->op != y->label->op)
		return 0;
	if (n->b && z && n->b->label->op != z->label->op)
		return 0;
	if (n->c && w && n->c->label->op != w->label->op)
		return 0;
	if ((!n->a) ^ (!y))
		return 0;
	if ((!n->c) ^ (!z))
		return 0;
	if ((!n->b) ^ (!w))
		return 0;
	return 1;
}

static int
op_is_identifer (operand_t *op)
{
	while (op->op_type == op_alias)
		op = op->o.alias;
	if (op->op_type == op_pointer)
		return 1;
	if (op->op_type == op_temp)
		return 1;
	if (op->op_type != op_symbol)
		return 0;
	if (op->o.symbol->sy_type != sy_var)
		return 0;
	return 1;
}

static void
dagnode_attach_label (dagnode_t *n, daglabel_t *l)
{
	if (!l->op)
		internal_error (0, "attempt to attach operator label to dagnode "
						"identifers");
	if (!op_is_identifer (l->op))
		internal_error (0, "attempt to attach non-identifer label to dagnode "
						"identifers");
	if (n->identifiers)
		n->identifiers->prev = &l->next;
	l->next = n->identifiers;
	l->prev = &n->identifiers;
	l->dagnode = n;
	n->identifiers = l;
}

static void
daglabel_detatch (daglabel_t *l)
{
	if (l->next)
		l->next->prev = l->prev;
	*l->prev = l->next;
	l->dagnode = 0;
}

dagnode_t *
make_dag (const sblock_t *block)
{
	statement_t *s;
	dagnode_t   *dagnodes = 0;
	dagnode_t   *d;

	flush_daglabels ();

	for (s = block->statements; s; s = s->next) {
		operand_t  *x = 0, *y = 0, *z = 0, *w = 0;
		dagnode_t  *n = 0, *ny, *nz, *nw;
		daglabel_t *op, *lx;
		int         simp;

		simp = find_operands (s, &x, &y, &z, &w);
		if (!(ny = node (y))) {
			ny = leaf_node (y);
			if (simp) {
				ny->next = dagnodes;
				dagnodes = ny;
			}
		}
		if (!(nz = node (z)))
			nz = leaf_node (z);
		if (!(nw = node (w)))
			nw = leaf_node (w);
		op = opcode_label (s->opcode);
		if (simp) {
			n = ny;
		} else {
			for (n = dagnodes; n; n = n->next)
				if (dagnode_match (n, op, ny, nz, nw))
					break;
		}
		if (!n) {
			n = new_node ();
			n->label = op;
			n->a = ny;
			n->b = nz;
			n->c = nw;
			if (ny)
				ny->is_child = 1;
			if (nz)
				nz->is_child = 1;
			if (nw)
				nw->is_child = 1;
			n->next = dagnodes;
			dagnodes = n;
		}
		lx = operand_label (x);
		if (lx) {
			if (lx->prev)
				daglabel_detatch (lx);
			dagnode_attach_label (n, lx);
		}
		// c = a * b
		// c = ~a
		// c = a / b
		// c = a + b
		// c = a - b
		// c = a {==,!=,<=,>=,<,>} b
		// c = a.b
		// c = &a.b
		// c = a (convert)
		// b = a
		// b .= a
		// b.c = a
		// c = !a
		// cond a goto b
		// callN a
		// rcallN a, [b, [c]]
		// state a, b
		// state a, b, c
		// goto a
		// jump a
		// jumpb a, b
		// c = a &&/|| b
		// c = a <</>> b
		// c = a & b
		// c = a | b
		// c = a % b
		// c = a ^ b
		// c = a (move) b (count)
	}
	while (dagnodes->is_child) {
		dagnode_t  *n = dagnodes->next;
		dagnodes->next = 0;
		dagnodes = n;
	}
	for (d = dagnodes; d && d->next; d = d->next) {
		while (d->next && d->next->is_child) {
			dagnode_t  *n = d->next->next;
			d->next->next = 0;
			d->next = n;
		}
	}
	return dagnodes;
}