/*
 * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.max.graal.nodes.loop;

import com.oracle.max.graal.graph.*;
import com.oracle.max.graal.nodes.*;
import com.sun.cri.ci.*;

/**
 * Counts loop iterations from 0 to Niter.
 * If used directly (and not just by BasicInductionVariables) computed with Phi(0, this + 1)
 */
public final class LoopCounterNode extends InductionVariableNode {
    @Input private LoopBeginNode loopBegin;

    @Override
    public LoopBeginNode loopBegin() {
        return loopBegin;
    }

    public LoopCounterNode(CiKind kind, LoopBeginNode loopBegin) {
        super(kind);
        this.loopBegin = loopBegin;
    }

    @Override
    public void peelOneIteration() {
        BasicInductionVariableNode biv = null;
        for (Node usage : usages()) {
            if (!(usage instanceof InductionVariableNode && ((InductionVariableNode) usage).loopBegin() == this.loopBegin())) {
                if (biv == null) {
                    biv = createBasicInductionVariable();
                    biv.peelOneIteration();
                }
                usage.inputs().replace(this, biv);
            }
        }
    }

    @Override
    public ValueNode stride() {
        return ConstantNode.forIntegerKind(kind(), 1, graph());
    }

    @Override
    public ValueNode lowerInductionVariable() {
        return BasicInductionVariableNode.ivToPhi(loopBegin(), minValue(null), stride(), kind());
    }

    @Override
    public boolean isNextIteration(InductionVariableNode other) {
        if (other instanceof LinearInductionVariableNode) {
            LinearInductionVariableNode liv = (LinearInductionVariableNode) other;
            if ((liv instanceof BasicInductionVariableNode && ((BasicInductionVariableNode) liv).loopCounter() == this) || (liv instanceof DerivedInductionVariableNode && ((DerivedInductionVariableNode) liv).base() == this)) {
                if (liv.a().isConstant() && liv.a().asConstant().asLong() == 1 && liv.b().isConstant() && liv.b().asConstant().asLong() == 1) {
                    return true;
                }
            }
        }
        return false;
    }

    @Override
    public ValueNode minValue(FixedNode point) {
        return ConstantNode.forIntegerKind(kind(), 0, graph());
    }

    @Override
    public ValueNode maxValue(FixedNode point) {
        return searchExtremum(point, StrideDirection.Up);
    }

    @Override
    public StrideDirection strideDirection() {
        return StrideDirection.Up;
    }

    private BasicInductionVariableNode createBasicInductionVariable() {
        return graph().add(new BasicInductionVariableNode(kind(), minValue(null), stride(), this));
    }
}