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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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).
 *
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package com.oracle.truffle.api.instrument;

/**
 * Instrument listener for a tool that works by providing an AST to be <em>spliced</em> directly
 * into the AST.
 */
public interface SpliceInstrumentListener {

    /**
     * Receive notification that a probed AST node to which the {@link Instrument} is attached is
     * about to be executed for the first time. This is a lazy opportunity for the tool to
     * optionally add the root of a newly created AST fragment that will be <em>spliced</em>
     * directly into the executing AST. The new AST fragment will immediately begin receiving
     * {@link InstrumentationNode.TruffleEvents}, beginning with the current execution event.
     * <p>
     * AST fragments must be written to Truffle conventions. Some of these conventions are
     * especially important if the fragment is to be fully optimized along with it's new parent AST.
     * <p>
     * If this method returns {@code null} then it will be called again the next time the probed
     * node is about to be executed.
     * <p>
     * In some situations, this method will be called more than once for a particular Probe, and a
     * new instance must be supplied each time. Each instance will be attached at the equivalent
     * location in clones of the AST, and so should be behave as if equivalent for most purposes.
     * <p>
     * In some situations the AST fragment supplied by this method maybe cloned for attachment to
     * equivalent locations in cloned AST, so care should be taken about any state local to each
     * instance of the AST fragment.
     *
     * @see Instrument
     */
    SplicedNode getSpliceNode(Probe probe);

}