/*      $NetBSD: gsp_eval.c,v 1.5 2025/11/24 08:04:28 nia Exp $ */
/*
 * GSP assembler - expression evaluation
 *
 * Copyright (c) 1993 Paul Mackerras.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: gsp_eval.c,v 1.5 2025/11/24 08:04:28 nia Exp $");
#endif

#include <stdlib.h>
#include "gsp_ass.h"
#include "gsp_gram.h"

int32_t eval_op(int, int32_t, int32_t);
int32_t eval_subtree(expr, unsigned *);

expr
fold(expr x)
{
        int32_t l;
        expr lp, rp;

        switch( x->e_op ){
        case SYM:
        case CONST:
        case '.':
                return x;
        }
        x->e_left = lp = fold(x->e_left);
        if( x->e_right != NULL )
                x->e_right = rp = fold(x->e_right);
        else
                rp = NULL;
        if( lp->e_op == CONST && (rp == NULL || rp->e_op == CONST) ){
                /* operator with constant subtree(s) */
                if( rp != NULL ){
                        l = eval_op(x->e_op, lp->e_val, rp->e_val);
                        free(rp);
                } else
                        l = eval_op(x->e_op, lp->e_val, 0);
                free(lp);
                x->e_op = CONST;
                x->e_val = l;
        }
        return x;
}

int32_t
eval_op(int op, int32_t l, int32_t r)
{
        switch( op ){
        case NEG:       l = -l;         break;
        case '~':       l = ~l;         break;
        case '+':       l += r;         break;
        case '-':       l -= r;         break;
        case '*':       l *= r;         break;
        case '&':       l &= r;         break;
        case '|':       l |= r;         break;
        case '^':       l ^= r;         break;
        case '/':
                if( r == 0 )
                        perr("Divide by zero");
                else
                        l /= r;
                break;
        case ':':
                l = (l << 16) | (r & 0xFFFF);
                break;
        case LEFT_SHIFT:
                l <<= r;
                break;
        case RIGHT_SHIFT:
                l >>= r;
                break;
        }
        return l;
}

int
eval_expr(expr e, int32_t *vp, unsigned *lp)
{
        e = fold(e);
        *vp = eval_subtree(e, lp);
        return (*lp < NOT_YET);
}

int32_t
eval_subtree(expr e, unsigned *lp)
{
        symbol s;
        int32_t v1, v2;
        unsigned l2;

        switch( e->e_op ){
        case SYM:
                s = e->e_sym;
                *lp = s->lineno;
                if( (s->flags & DEFINED) != 0 )
                        return s->value;
                perr("Undefined symbol %s", s->name);
                return 0;
        case CONST:
                *lp = 0;
                return e->e_val;
        case '.':
                *lp = lineno;
                return pc;
        default:
                v1 = eval_subtree(e->e_left, lp);
                if( e->e_right == NULL )
                        return eval_op(e->e_op, v1, 0);
                v2 = eval_subtree(e->e_right, &l2);
                if( l2 > *lp )
                        *lp = l2;
                return eval_op(e->e_op, v1, v2);
        }
}