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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.
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 * 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.
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package org.graalvm.compiler.replacements;

import static org.graalvm.compiler.nodes.calc.CompareNode.createCompareNode;

import java.util.List;

import org.graalvm.compiler.api.replacements.SnippetReflectionProvider;
import org.graalvm.compiler.core.common.calc.Condition;
import org.graalvm.compiler.graph.Node;
import org.graalvm.compiler.nodes.ConditionAnchorNode;
import org.graalvm.compiler.nodes.ConstantNode;
import org.graalvm.compiler.nodes.FixedGuardNode;
import org.graalvm.compiler.nodes.IfNode;
import org.graalvm.compiler.nodes.LogicConstantNode;
import org.graalvm.compiler.nodes.LogicNode;
import org.graalvm.compiler.nodes.PhiNode;
import org.graalvm.compiler.nodes.ShortCircuitOrNode;
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.FloatingNode;
import org.graalvm.compiler.nodes.java.ClassIsAssignableFromNode;
import org.graalvm.compiler.nodes.java.InstanceOfDynamicNode;
import org.graalvm.compiler.nodes.java.InstanceOfNode;
import org.graalvm.compiler.nodes.spi.LoweringTool;
import org.graalvm.compiler.nodes.util.GraphUtil;
import org.graalvm.compiler.phases.util.Providers;
import org.graalvm.compiler.replacements.SnippetTemplate.AbstractTemplates;
import org.graalvm.compiler.replacements.SnippetTemplate.Arguments;
import org.graalvm.compiler.replacements.SnippetTemplate.UsageReplacer;

import jdk.vm.ci.code.TargetDescription;

Helper class for lowering InstanceOfNodes with snippets. The majority of the complexity in such a lowering derives from the fact that InstanceOfNode is a floating node. A snippet used to lower an InstanceOfNode will almost always incorporate control flow and replacing a floating node with control flow is not trivial. 
 The mechanism implemented in this class ensures that the graph for an instanceof snippet is instantiated once per InstanceOfNode being lowered. The result produced is then re-used by all usages of the node. Additionally, if there is a single usage that is an IfNode, the control flow in the snippet is connected directly to the true and false successors of the IfNode. This avoids materializing the instanceof test as a boolean which is then retested by the IfNode. /**
 * Helper class for lowering {@link InstanceOfNode}s with snippets. The majority of the complexity
 * in such a lowering derives from the fact that {@link InstanceOfNode} is a floating node. A
 * snippet used to lower an {@link InstanceOfNode} will almost always incorporate control flow and
 * replacing a floating node with control flow is not trivial.
 * <p>
 * The mechanism implemented in this class ensures that the graph for an instanceof snippet is
 * instantiated once per {@link InstanceOfNode} being lowered. The result produced is then re-used
 * by all usages of the node. Additionally, if there is a single usage that is an {@link IfNode},
 * the control flow in the snippet is connected directly to the true and false successors of the
 * {@link IfNode}. This avoids materializing the instanceof test as a boolean which is then retested
 * by the {@link IfNode}.
 */
public abstract class InstanceOfSnippetsTemplates extends AbstractTemplates {

    public InstanceOfSnippetsTemplates(Providers providers, SnippetReflectionProvider snippetReflection, TargetDescription target) {
        super(providers, snippetReflection, target);
    }

    
Gets the arguments used to retrieve and instantiate an instanceof snippet template.
/**
     * Gets the arguments used to retrieve and instantiate an instanceof snippet template.
     */
    protected abstract Arguments makeArguments(InstanceOfUsageReplacer replacer, LoweringTool tool);

    public void lower(FloatingNode instanceOf, LoweringTool tool) {
        assert instanceOf instanceof InstanceOfNode || instanceOf instanceof InstanceOfDynamicNode || instanceOf instanceof ClassIsAssignableFromNode;
        List<Node> usages = instanceOf.usages().snapshot();

        Instantiation instantiation = new Instantiation();
        for (Node usage : usages) {
            final StructuredGraph graph = (StructuredGraph) usage.graph();

            InstanceOfUsageReplacer replacer = createReplacer(instanceOf, instantiation, usage, graph);

            if (instantiation.isInitialized()) {
                // No need to re-instantiate the snippet - just re-use its result
                replacer.replaceUsingInstantiation();
            } else {
                Arguments args = makeArguments(replacer, tool);
                template(args).instantiate(providers.getMetaAccess(), instanceOf, replacer, tool, args);
            }
        }

        assert instanceOf.hasNoUsages();
        if (!instanceOf.isDeleted()) {
            GraphUtil.killWithUnusedFloatingInputs(instanceOf);
        }
    }

    
Gets the specific replacer object used to replace the usage of an instanceof node with the
result of an instantiated instanceof snippet.
/**
     * Gets the specific replacer object used to replace the usage of an instanceof node with the
     * result of an instantiated instanceof snippet.
     */
    protected InstanceOfUsageReplacer createReplacer(FloatingNode instanceOf, Instantiation instantiation, Node usage, final StructuredGraph graph) {
        InstanceOfUsageReplacer replacer;
        if (!canMaterialize(usage)) {
            ValueNode trueValue = ConstantNode.forInt(1, graph);
            ValueNode falseValue = ConstantNode.forInt(0, graph);
            if (instantiation.isInitialized() && (trueValue != instantiation.trueValue || falseValue != instantiation.falseValue)) {
                /*
                 * This code doesn't really care what values are used so adopt the values from the
                 * previous instantiation.
                 */
                trueValue = instantiation.trueValue;
                falseValue = instantiation.falseValue;
            }
            replacer = new NonMaterializationUsageReplacer(instantiation, trueValue, falseValue, instanceOf, usage);
        } else {
            assert usage instanceof ConditionalNode : "unexpected usage of " + instanceOf + ": " + usage;
            ConditionalNode c = (ConditionalNode) usage;
            replacer = new MaterializationUsageReplacer(instantiation, c.trueValue(), c.falseValue(), instanceOf, c);
        }
        return replacer;
    }

    
Determines if an instanceof usage can be materialized. /**
     * Determines if an {@code instanceof} usage can be materialized.
     */
    protected boolean canMaterialize(Node usage) {
        if (usage instanceof ConditionalNode) {
            ConditionalNode cn = (ConditionalNode) usage;
            return cn.trueValue().isConstant() && cn.falseValue().isConstant();
        }
        if (usage instanceof IfNode || usage instanceof FixedGuardNode || usage instanceof ShortCircuitOrNode || usage instanceof ConditionAnchorNode) {
            return false;
        }
        return true;
    }

    
The result of instantiating an instanceof snippet. This enables a snippet instantiation to be
re-used which reduces compile time and produces better code.
/**
     * The result of instantiating an instanceof snippet. This enables a snippet instantiation to be
     * re-used which reduces compile time and produces better code.
     */
    public static final class Instantiation {

        private ValueNode result;
        private LogicNode condition;
        private ValueNode trueValue;
        private ValueNode falseValue;

        
Determines if the instantiation has occurred.
/**
         * Determines if the instantiation has occurred.
         */
        boolean isInitialized() {
            return result != null;
        }

        void initialize(ValueNode r, ValueNode t, ValueNode f) {
            assert !isInitialized();
            this.result = r;
            this.trueValue = t;
            this.falseValue = f;
        }

        
Gets the result of this instantiation as a condition.
Params:
testValue – the returned condition is true if the result is equal to this value/**
         * Gets the result of this instantiation as a condition.
         *
         * @param testValue the returned condition is true if the result is equal to this value
         */
        LogicNode asCondition(ValueNode testValue) {
            assert isInitialized();
            if (result.isConstant()) {
                assert testValue.isConstant();
                return LogicConstantNode.forBoolean(result.asConstant().equals(testValue.asConstant()), result.graph());
            }
            if (condition == null || (!(condition instanceof CompareNode)) || ((CompareNode) condition).getY() != testValue) {
                // Re-use previously generated condition if the trueValue for the test is the same
                condition = createCompareNode(result.graph(), Condition.EQ, result, testValue, null);
            }
            return condition;
        }

        
Gets the result of the instantiation as a materialized value.
Params:
t – the true value for the materialization
f – the false value for the materialization/**
         * Gets the result of the instantiation as a materialized value.
         *
         * @param t the true value for the materialization
         * @param f the false value for the materialization
         */
        ValueNode asMaterialization(StructuredGraph graph, ValueNode t, ValueNode f) {
            assert isInitialized();
            if (t == this.trueValue && f == this.falseValue) {
                // Can simply use the phi result if the same materialized values are expected.
                return result;
            } else {
                return graph.unique(new ConditionalNode(asCondition(trueValue), t, f));
            }
        }
    }

    
Replaces a usage of an InstanceOfNode or InstanceOfDynamicNode. /**
     * Replaces a usage of an {@link InstanceOfNode} or {@link InstanceOfDynamicNode}.
     */
    public abstract static class InstanceOfUsageReplacer implements UsageReplacer {

        public final Instantiation instantiation;
        public final FloatingNode instanceOf;
        public final ValueNode trueValue;
        public final ValueNode falseValue;

        public InstanceOfUsageReplacer(Instantiation instantiation, FloatingNode instanceOf, ValueNode trueValue, ValueNode falseValue) {
            assert instanceOf instanceof InstanceOfNode || instanceOf instanceof InstanceOfDynamicNode || instanceOf instanceof ClassIsAssignableFromNode;
            this.instantiation = instantiation;
            this.instanceOf = instanceOf;
            this.trueValue = trueValue;
            this.falseValue = falseValue;
        }

        
Does the replacement based on a previously snippet instantiation.
/**
         * Does the replacement based on a previously snippet instantiation.
         */
        public abstract void replaceUsingInstantiation();
    }

    
Replaces the usage of an InstanceOfNode or InstanceOfDynamicNode that does not materialize the result of the type test. /**
     * Replaces the usage of an {@link InstanceOfNode} or {@link InstanceOfDynamicNode} that does
     * not materialize the result of the type test.
     */
    public static class NonMaterializationUsageReplacer extends InstanceOfUsageReplacer {

        private final Node usage;

        public NonMaterializationUsageReplacer(Instantiation instantiation, ValueNode trueValue, ValueNode falseValue, FloatingNode instanceOf, Node usage) {
            super(instantiation, instanceOf, trueValue, falseValue);
            this.usage = usage;
        }

        @Override
        public void replaceUsingInstantiation() {
            usage.replaceFirstInput(instanceOf, instantiation.asCondition(trueValue));
        }

        @Override
        public void replace(ValueNode oldNode, ValueNode newNode) {
            assert newNode instanceof PhiNode;
            assert oldNode == instanceOf;
            newNode.inferStamp();
            instantiation.initialize(newNode, trueValue, falseValue);
            usage.replaceFirstInput(oldNode, instantiation.asCondition(trueValue));
        }
    }

    
Replaces the usage of an InstanceOfNode or InstanceOfDynamicNode that does materializes the result of the type test. /**
     * Replaces the usage of an {@link InstanceOfNode} or {@link InstanceOfDynamicNode} that does
     * materializes the result of the type test.
     */
    public static class MaterializationUsageReplacer extends InstanceOfUsageReplacer {

        public final ConditionalNode usage;

        public MaterializationUsageReplacer(Instantiation instantiation, ValueNode trueValue, ValueNode falseValue, FloatingNode instanceOf, ConditionalNode usage) {
            super(instantiation, instanceOf, trueValue, falseValue);
            this.usage = usage;
        }

        @Override
        public void replaceUsingInstantiation() {
            ValueNode newValue = instantiation.asMaterialization(usage.graph(), trueValue, falseValue);
            usage.replaceAtUsages(newValue);
            assert usage.hasNoUsages();
            GraphUtil.killWithUnusedFloatingInputs(usage);
        }

        @Override
        public void replace(ValueNode oldNode, ValueNode newNode) {
            assert newNode instanceof PhiNode;
            assert oldNode == instanceOf;
            newNode.inferStamp();
            instantiation.initialize(newNode, trueValue, falseValue);
            usage.replaceAtUsages(newNode);
            assert usage.hasNoUsages();
            GraphUtil.killWithUnusedFloatingInputs(usage);
        }
    }
}