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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package org.graalvm.compiler.hotspot.replacements;

import static org.graalvm.compiler.hotspot.GraalHotSpotVMConfig.INJECTED_VMCONFIG;
import static org.graalvm.compiler.hotspot.meta.HotSpotForeignCallsProviderImpl.IDENTITY_HASHCODE;
import static org.graalvm.compiler.hotspot.replacements.HotSpotReplacementsUtil.biasedLockMaskInPlace;
import static org.graalvm.compiler.hotspot.replacements.HotSpotReplacementsUtil.identityHashCode;
import static org.graalvm.compiler.hotspot.replacements.HotSpotReplacementsUtil.identityHashCodeShift;
import static org.graalvm.compiler.hotspot.replacements.HotSpotReplacementsUtil.loadWordFromObject;
import static org.graalvm.compiler.hotspot.replacements.HotSpotReplacementsUtil.markOffset;
import static org.graalvm.compiler.hotspot.replacements.HotSpotReplacementsUtil.uninitializedIdentityHashCodeValue;
import static org.graalvm.compiler.hotspot.replacements.HotSpotReplacementsUtil.unlockedMask;
import static org.graalvm.compiler.nodes.extended.BranchProbabilityNode.FAST_PATH_PROBABILITY;
import static org.graalvm.compiler.nodes.extended.BranchProbabilityNode.probability;

import org.graalvm.compiler.replacements.IdentityHashCodeSnippets;
import org.graalvm.compiler.word.Word;
import org.graalvm.word.WordFactory;

public class HotSpotHashCodeSnippets extends IdentityHashCodeSnippets {

    @Override
    protected int computeIdentityHashCode(final Object x) {
        Word mark = loadWordFromObject(x, markOffset(INJECTED_VMCONFIG));

        // this code is independent from biased locking (although it does not look that way)
        final Word biasedLock = mark.and(biasedLockMaskInPlace(INJECTED_VMCONFIG));
        if (probability(FAST_PATH_PROBABILITY, biasedLock.equal(WordFactory.unsigned(unlockedMask(INJECTED_VMCONFIG))))) {
            int hash = (int) mark.unsignedShiftRight(identityHashCodeShift(INJECTED_VMCONFIG)).rawValue();
            if (probability(FAST_PATH_PROBABILITY, hash != uninitializedIdentityHashCodeValue(INJECTED_VMCONFIG))) {
                return hash;
            }
        }
        return identityHashCode(IDENTITY_HASHCODE, x);
    }
}