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package com.oracle.truffle.api.profiles;

import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.nodes.Node;

 BranchProfiles are profiles to speculate on branches that are unlikely to be visited. If the enter() method is invoked first the optimized code is invalidated and the branch where enter() is invoked is enabled for compilation. Otherwise if the enter() method was never invoked the branch will not get compiled. 

 Usage example:  BranchingNode.errorProfile {@inheritDoc} 
See Also:
enter()
Since:
0.10/**
 * <p>
 * BranchProfiles are profiles to speculate on branches that are unlikely to be visited. If the
 * {@link #enter()} method is invoked first the optimized code is invalidated and the branch where
 * {@link #enter()} is invoked is enabled for compilation. Otherwise if the {@link #enter()} method
 * was never invoked the branch will not get compiled.
 * </p>
 *
 * <p>
 * <b> Usage example: </b>
 * {@link com.oracle.truffle.api.profiles.BranchProfileSnippets.BranchingNode#errorProfile}
 *
 * {@inheritDoc}
 *
 * @see BranchProfile#enter()
 * @since 0.10
 */
public abstract class BranchProfile extends Profile {

    BranchProfile() {
    }

    
Call when an unlikely branch is entered.
Since:
0.10/**
     * Call when an unlikely branch is entered.
     *
     * @since 0.10
     */
    public abstract void enter();

    
Call to create a new instance of a branch profile.
Since:
0.10/**
     * Call to create a new instance of a branch profile.
     *
     * @since 0.10
     */
    public static BranchProfile create() {
        if (Profile.isProfilingEnabled()) {
            return Enabled.create0();
        } else {
            return Disabled.INSTANCE;
        }
    }

    
Returns the uncached version of the profile. The uncached version of a profile does nothing.
Since:
19.0/**
     * Returns the uncached version of the profile. The uncached version of a profile does nothing.
     *
     * @since 19.0
     */
    public static BranchProfile getUncached() {
        return Disabled.INSTANCE;
    }

    static final class Enabled extends BranchProfile {

        @CompilationFinal private boolean visited;

        @Override
        public void enter() {
            if (!visited) {
                CompilerDirectives.transferToInterpreterAndInvalidate();
                visited = true;
            }
        }

        @Override
        public String toString() {
            return toString(BranchProfile.class, !visited, false, "VISITED");
        }

        /* Needed for lazy class loading. */
        static BranchProfile create0() {
            return new Enabled();
        }
    }

    static final class Disabled extends BranchProfile {

        static final BranchProfile INSTANCE = new Disabled();

        @Override
        protected Object clone() {
            return INSTANCE;
        }

        @Override
        public void enter() {
        }

        @Override
        public String toString() {
            return toStringDisabled(BranchProfile.class);
        }

    }

}

class BranchProfileSnippets {
    // BEGIN: com.oracle.truffle.api.profiles.BranchProfileSnippets.BranchingNode#errorProfile
    class BranchingNode extends Node {
        final BranchProfile errorProfile = BranchProfile.create();

        int execute(int value) {
            if (value == Integer.MAX_VALUE) {
                errorProfile.enter();
                throw new Error("Invalid input value");
            }
            return value;
        }
    }
    // END: com.oracle.truffle.api.profiles.BranchProfileSnippets.BranchingNode#errorProfile
}