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package org.graalvm.compiler.loop;

import static org.graalvm.compiler.loop.MathUtil.add;
import static org.graalvm.compiler.loop.MathUtil.sub;
import static org.graalvm.compiler.loop.MathUtil.unsignedDivBefore;

import org.graalvm.compiler.core.common.type.IntegerStamp;
import org.graalvm.compiler.core.common.type.Stamp;
import org.graalvm.compiler.core.common.util.UnsignedLong;
import org.graalvm.compiler.debug.DebugCloseable;
import org.graalvm.compiler.loop.InductionVariable.Direction;
import org.graalvm.compiler.nodes.AbstractBeginNode;
import org.graalvm.compiler.nodes.ConstantNode;
import org.graalvm.compiler.nodes.GuardNode;
import org.graalvm.compiler.nodes.IfNode;
import org.graalvm.compiler.nodes.NodeView;
import org.graalvm.compiler.nodes.StructuredGraph;
import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.calc.CompareNode;
import org.graalvm.compiler.nodes.calc.ConditionalNode;
import org.graalvm.compiler.nodes.calc.IntegerLessThanNode;
import org.graalvm.compiler.nodes.calc.NegateNode;
import org.graalvm.compiler.nodes.extended.GuardingNode;

import jdk.vm.ci.code.CodeUtil;
import jdk.vm.ci.meta.DeoptimizationAction;
import jdk.vm.ci.meta.DeoptimizationReason;
import jdk.vm.ci.meta.SpeculationLog;

public class CountedLoopInfo {

    private final LoopEx loop;
    private InductionVariable iv;
    private ValueNode end;
    private boolean oneOff;
    private AbstractBeginNode body;
    private IfNode ifNode;

    CountedLoopInfo(LoopEx loop, InductionVariable iv, IfNode ifNode, ValueNode end, boolean oneOff, AbstractBeginNode body) {
        assert iv.direction() != null;
        this.loop = loop;
        this.iv = iv;
        this.end = end;
        this.oneOff = oneOff;
        this.body = body;
        this.ifNode = ifNode;
    }

    
Returns a node that computes the maximum trip count of this loop. That is the trip count of this loop assuming it is not exited by an other exit than the 
count check. This count is exact if isExactTripCount() returns true. THIS VALUE SHOULD BE TREATED AS UNSIGNED. /**
     * Returns a node that computes the maximum trip count of this loop. That is the trip count of
     * this loop assuming it is not exited by an other exit than the {@linkplain #getLimitTest()
     * count check}.
     *
     * This count is exact if {@link #isExactTripCount()} returns true.
     *
     * THIS VALUE SHOULD BE TREATED AS UNSIGNED.
     */
    public ValueNode maxTripCountNode() {
        return maxTripCountNode(false);
    }

    
Returns a node that computes the maximum trip count of this loop. That is the trip count of this loop assuming it is not exited by an other exit than the 
count check. This count is exact if isExactTripCount() returns true. THIS VALUE SHOULD BE TREATED AS UNSIGNED. 
Params:
assumePositive – if true the check that the loop is entered at all will be omitted./**
     * Returns a node that computes the maximum trip count of this loop. That is the trip count of
     * this loop assuming it is not exited by an other exit than the {@linkplain #getLimitTest()
     * count check}.
     *
     * This count is exact if {@link #isExactTripCount()} returns true.
     *
     * THIS VALUE SHOULD BE TREATED AS UNSIGNED.
     *
     * @param assumePositive if true the check that the loop is entered at all will be omitted.
     */
    public ValueNode maxTripCountNode(boolean assumePositive) {
        StructuredGraph graph = iv.valueNode().graph();
        Stamp stamp = iv.valueNode().stamp(NodeView.DEFAULT);

        ValueNode max;
        ValueNode min;
        ValueNode range;
        ValueNode absStride;
        if (iv.direction() == Direction.Up) {
            absStride = iv.strideNode();
            range = sub(graph, end, iv.initNode());
            max = end;
            min = iv.initNode();
        } else {
            assert iv.direction() == Direction.Down;
            absStride = graph.maybeAddOrUnique(NegateNode.create(iv.strideNode(), NodeView.DEFAULT));
            range = sub(graph, iv.initNode(), end);
            max = iv.initNode();
            min = end;
        }

        ConstantNode one = ConstantNode.forIntegerStamp(stamp, 1, graph);
        if (oneOff) {
            range = add(graph, range, one);
        }
        // round-away-from-zero divison: (range + stride -/+ 1) / stride
        ValueNode denominator = add(graph, range, sub(graph, absStride, one));
        ValueNode div = unsignedDivBefore(graph, loop.entryPoint(), denominator, absStride, null);

        if (assumePositive) {
            return div;
        }
        ConstantNode zero = ConstantNode.forIntegerStamp(stamp, 0, graph);
        return graph.unique(new ConditionalNode(graph.unique(new IntegerLessThanNode(max, min)), zero, div));
    }

    
Returns:
true if the loop has constant bounds./**
     * @return true if the loop has constant bounds.
     */
    public boolean isConstantMaxTripCount() {
        return end instanceof ConstantNode && iv.isConstantInit() && iv.isConstantStride();
    }

    public UnsignedLong constantMaxTripCount() {
        assert isConstantMaxTripCount();
        return new UnsignedLong(rawConstantMaxTripCount());
    }

    
Compute the raw value of the trip count for this loop. THIS IS AN UNSIGNED VALUE;
/**
     * Compute the raw value of the trip count for this loop. THIS IS AN UNSIGNED VALUE;
     */
    private long rawConstantMaxTripCount() {
        assert iv.direction() != null;
        long endValue = end.asJavaConstant().asLong();
        long initValue = iv.constantInit();
        long range;
        long absStride;
        if (iv.direction() == Direction.Up) {
            if (endValue < initValue) {
                return 0;
            }
            range = endValue - iv.constantInit();
            absStride = iv.constantStride();
        } else {
            assert iv.direction() == Direction.Down;
            if (initValue < endValue) {
                return 0;
            }
            range = iv.constantInit() - endValue;
            absStride = -iv.constantStride();
        }
        if (oneOff) {
            range += 1;
        }
        long denominator = range + absStride - 1;
        return Long.divideUnsigned(denominator, absStride);
    }

    public boolean isExactTripCount() {
        return loop.loopBegin().loopExits().count() == 1;
    }

    public ValueNode exactTripCountNode() {
        assert isExactTripCount();
        return maxTripCountNode();
    }

    public boolean isConstantExactTripCount() {
        assert isExactTripCount();
        return isConstantMaxTripCount();
    }

    public UnsignedLong constantExactTripCount() {
        assert isExactTripCount();
        return constantMaxTripCount();
    }

    @Override
    public String toString() {
        return "iv=" + iv + " until " + end + (oneOff ? iv.direction() == Direction.Up ? "+1" : "-1" : "");
    }

    public ValueNode getLimit() {
        return end;
    }

    public IfNode getLimitTest() {
        return ifNode;
    }

    public ValueNode getStart() {
        return iv.initNode();
    }

    public boolean isLimitIncluded() {
        return oneOff;
    }

    public AbstractBeginNode getBody() {
        return body;
    }

    public Direction getDirection() {
        return iv.direction();
    }

    public InductionVariable getCounter() {
        return iv;
    }

    public GuardingNode getOverFlowGuard() {
        return loop.loopBegin().getOverflowGuard();
    }

    @SuppressWarnings("try")
    public GuardingNode createOverFlowGuard() {
        GuardingNode overflowGuard = getOverFlowGuard();
        if (overflowGuard != null) {
            return overflowGuard;
        }
        try (DebugCloseable position = loop.loopBegin().withNodeSourcePosition()) {
            IntegerStamp stamp = (IntegerStamp) iv.valueNode().stamp(NodeView.DEFAULT);
            StructuredGraph graph = iv.valueNode().graph();
            CompareNode cond; // we use a negated guard with a < condition to achieve a >=
            ConstantNode one = ConstantNode.forIntegerStamp(stamp, 1, graph);
            if (iv.direction() == Direction.Up) {
                ValueNode v1 = sub(graph, ConstantNode.forIntegerStamp(stamp, CodeUtil.maxValue(stamp.getBits()), graph), sub(graph, iv.strideNode(), one));
                if (oneOff) {
                    v1 = sub(graph, v1, one);
                }
                cond = graph.unique(new IntegerLessThanNode(v1, end));
            } else {
                assert iv.direction() == Direction.Down;
                ValueNode v1 = add(graph, ConstantNode.forIntegerStamp(stamp, CodeUtil.minValue(stamp.getBits()), graph), sub(graph, one, iv.strideNode()));
                if (oneOff) {
                    v1 = add(graph, v1, one);
                }
                cond = graph.unique(new IntegerLessThanNode(end, v1));
            }
            assert graph.getGuardsStage().allowsFloatingGuards();
            overflowGuard = graph.unique(new GuardNode(cond, AbstractBeginNode.prevBegin(loop.entryPoint()), DeoptimizationReason.LoopLimitCheck, DeoptimizationAction.InvalidateRecompile, true,
                            SpeculationLog.NO_SPECULATION, null)); // TODO gd: use speculation
            loop.loopBegin().setOverflowGuard(overflowGuard);
            return overflowGuard;
        }
    }

    public IntegerStamp getStamp() {
        return (IntegerStamp) iv.valueNode().stamp(NodeView.DEFAULT);
    }
}