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package com.oracle.truffle.api.nodes;

import com.oracle.truffle.api.CompilerDirectives;

/**
 * Represents a rough estimate for the cost of a {@link Node}. This estimate can be used by runtime
 * systems or guest languages to implement heuristics based on Truffle ASTs.
 *
 * @see Node#getCost()
 * @since 0.8 or earlier
 */
public enum NodeCost {

    /**
     * This node has literally no costs and should be ignored for heuristics. This is particularly
     * useful for wrapper and profiling nodes which should not influence the heuristics.
     * 
     * @since 0.8 or earlier
     */
    NONE,

    /**
     * This node has a {@link CompilerDirectives#transferToInterpreter()} or
     * {@link CompilerDirectives#transferToInterpreterAndInvalidate()} as its first unconditional
     * statement.
     * 
     * @since 0.8 or earlier
     */
    UNINITIALIZED,

    /**
     * This node represents a specialized monomorphic version of an operation.
     * 
     * @since 0.8 or earlier
     */
    MONOMORPHIC,

    /**
     * This node represents a polymorphic version of an operation. For multiple chained polymorphic
     * nodes the first may return {@link #MONOMORPHIC} and all additional nodes should return
     * {@link #POLYMORPHIC}.
     * 
     * @since 0.8 or earlier
     */
    POLYMORPHIC,

    /**
     * This node represents a megamorphic version of an operation. This value should only be used if
     * the operation implementation supports monomorphism and polymorphism otherwise
     * {@link #MONOMORPHIC} should be used instead.
     * 
     * @since 0.8 or earlier
     */
    MEGAMORPHIC;

    /** @since 0.8 or earlier */
    public boolean isTrivial() {
        return this == NONE || this == UNINITIALIZED;
    }
}