Examples with SwitchStrategy org.graalvm.compiler.lir.SwitchStrategy used on opensource projects

Example 1 with SwitchStrategy

use of org.graalvm.compiler.lir.SwitchStrategy in project graal by oracle.

the class LIRGenerator method emitStrategySwitch.

@Override
public void emitStrategySwitch(JavaConstant[] keyConstants, double[] keyProbabilities, LabelRef[] keyTargets, LabelRef defaultTarget, Variable value) {
    int keyCount = keyConstants.length;
    SwitchStrategy strategy = SwitchStrategy.getBestStrategy(keyProbabilities, keyConstants, keyTargets);
    long valueRange = keyConstants[keyCount - 1].asLong() - keyConstants[0].asLong() + 1;
    double tableSwitchDensity = keyCount / (double) valueRange;
    /*
         * This heuristic tries to find a compromise between the effort for the best switch strategy
         * and the density of a tableswitch. If the effort for the strategy is at least 4, then a
         * tableswitch is preferred if better than a certain value that starts at 0.5 and lowers
         * gradually with additional effort.
         */
    if (strategy.getAverageEffort() < 4 || tableSwitchDensity < (1 / Math.sqrt(strategy.getAverageEffort()))) {
        emitStrategySwitch(strategy, value, keyTargets, defaultTarget);
    } else {
        int minValue = keyConstants[0].asInt();
        assert valueRange < Integer.MAX_VALUE;
        LabelRef[] targets = new LabelRef[(int) valueRange];
        for (int i = 0; i < valueRange; i++) {
            targets[i] = defaultTarget;
        }
        for (int i = 0; i < keyCount; i++) {
            targets[keyConstants[i].asInt() - minValue] = keyTargets[i];
        }
        emitTableSwitch(minValue, defaultTarget, targets, value);
    }
}