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 * (a) the Software, and
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 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
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package com.oracle.truffle.js.nodes.arguments;

import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.instrumentation.Tag;
import com.oracle.truffle.api.nodes.ExplodeLoop;
import com.oracle.truffle.js.nodes.JavaScriptNode;
import com.oracle.truffle.js.runtime.JSArguments;

import java.util.Set;

public class AccessVarArgsNode extends AccessIndexedArgumentNode {
    private static final int MAX_UNROLL = 250;
    private static final int UNINITIALIZED = -2;
    
Unstable or too large argument count. /** Unstable or too large argument count. */
    private static final int UNSTABLE = -1;

    
Expected/profiled stable user argument count or UNSTABLE. /** Expected/profiled stable user argument count or {@link #UNSTABLE}. */
    @CompilationFinal private int userArgumentCount;

    AccessVarArgsNode(int paramIndex) {
        super(paramIndex);
        this.userArgumentCount = UNINITIALIZED;
    }

    public static AccessVarArgsNode create(int paramIndex) {
        return new AccessVarArgsNode(paramIndex);
    }

    @Override
    public final Object[] execute(VirtualFrame frame) {
        Object[] arguments = frame.getArguments();
        int currentUserArgumentCount = JSArguments.getUserArgumentCount(arguments);

        if (profile(index >= currentUserArgumentCount)) {
            return JSArguments.EMPTY_ARGUMENTS_ARRAY;
        } else {
            int constantUserArgumentCount = userArgumentCount;

            if (constantUserArgumentCount == UNINITIALIZED) {
                CompilerDirectives.transferToInterpreterAndInvalidate();
                if (currentUserArgumentCount <= MAX_UNROLL) {
                    constantUserArgumentCount = currentUserArgumentCount;
                } else {
                    constantUserArgumentCount = UNSTABLE;
                }
                userArgumentCount = constantUserArgumentCount;
            }

            if (constantUserArgumentCount == UNSTABLE) {
                return getArgumentsArrayWithoutExplosion(arguments, currentUserArgumentCount);
            }

            if (constantUserArgumentCount != currentUserArgumentCount) {
                CompilerDirectives.transferToInterpreterAndInvalidate();
                constantUserArgumentCount = currentUserArgumentCount;
                userArgumentCount = UNSTABLE;
            }

            return getArgumentsArray(arguments, constantUserArgumentCount);
        }
    }

    @ExplodeLoop
    private Object[] getArgumentsArray(Object[] arguments, int constantUserArgumentCount) {
        int length = constantUserArgumentCount - index;
        Object[] varArgs = new Object[length];
        for (int i = 0; i < length; i++) {
            varArgs[i] = JSArguments.getUserArgument(arguments, i + index);
        }
        return varArgs;
    }

    private Object[] getArgumentsArrayWithoutExplosion(Object[] arguments, int currentUserArgumentCount) {
        int length = currentUserArgumentCount - index;
        Object[] varArgs = new Object[length];
        for (int i = 0; i < length; i++) {
            varArgs[i] = JSArguments.getUserArgument(arguments, i + index);
        }
        return varArgs;
    }

    @Override
    protected JavaScriptNode copyUninitialized(Set<Class<? extends Tag>> materializedTags) {
        return new AccessVarArgsNode(index);
    }
}