/*
 * Copyright (C) 2014 Oracle.
 *
 * 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, see http://www.gnu.org/copyleft/gpl.txt
 */

#include "smatch.h"

static int my_id;

static void match_binop(struct expression *expr)
{
        struct symbol *type;
        sval_t bits;

        if (expr->op != SPECIAL_RIGHTSHIFT)
                return;

        if (!get_implied_value(expr->right, &bits))
                return;

        type = get_type(expr->left);
        if (!type)
                return;
        if (type_bits(type) == -1 || type_bits(type) > bits.value)
                return;
        if (is_ignored_expr(my_id, expr))
                return;
        sm_warning("right shifting more than type allows %d vs %lld", type_bits(type), bits.value);
}

static void match_binop2(struct expression *expr)
{
        struct expression *left;
        struct expression *tmp;
        sval_t mask, shift;

        if (expr->op != SPECIAL_RIGHTSHIFT)
                return;

        left = strip_expr(expr->left);
        tmp = get_assigned_expr(left);
        if (tmp)
                left = tmp;
        if (left->type != EXPR_BINOP || left->op != '&')
                return;

        if (!get_value(expr->right, &shift))
                return;
        if (!get_value(left->right, &mask))
                return;

        if (mask.uvalue >> shift.uvalue)
                return;

        sm_warning("mask and shift to zero");
}

static void match_assign(struct expression *expr)
{
        struct symbol *type;
        sval_t bits;

        if (expr->op != SPECIAL_SHR_ASSIGN)
                return;

        if (!get_implied_value(expr->right, &bits))
                return;
        type = get_type(expr->left);
        if (!type)
                return;
        if (type_bits(type) > bits.value)
                return;
        sm_warning("right shift assign to zero");
}

void check_shift_to_zero(int id)
{
        my_id = id;

        add_hook(&match_binop, BINOP_HOOK);
        add_hook(&match_binop2, BINOP_HOOK);

        add_hook(&match_assign, ASSIGNMENT_HOOK);

}