test/hotspot/jtreg/compiler/loopopts/TestBaseCountedEndLoopUnswitchCandidate.java

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/*
 * @test
 * @bug 8325746
 * @summary Test Loop Unswitching with BaseCountedLoopEnd nodes as unswitch candidate.
 * @requires vm.compiler2.enabled
 * @run main/othervm -XX:CompileCommand=compileonly,compiler.loopopts.TestBaseCountedEndLoopUnswitchCandidate::test*
 *                   -Xcomp -XX:LoopMaxUnroll=0 -XX:-UseLoopPredicate -XX:-RangeCheckElimination
 *                   compiler.loopopts.TestBaseCountedEndLoopUnswitchCandidate
 * @run main compiler.loopopts.TestBaseCountedEndLoopUnswitchCandidate
 */

package compiler.loopopts;

public class TestBaseCountedEndLoopUnswitchCandidate {
    static int iFld;
    static long lFld;
    static A a = new A();
    static boolean flag;

    public static void main(String[] k) {
        for (int i = 0; i < 10000; i++) {
            testLongCountedLoopEnd();
            testCountedLoopEnd();
        }
    }

    public static void testLongCountedLoopEnd() {
        long limit = lFld;
        for (int i = 0; i < 100; i++) {

            // After peeling & IGNV:
            //      LongCountedEndLoop
            //           /      \
            //         True    False
            //        / \       /
            //  Store    Region
            //
            // LongCountedEndLoop has both paths inside loop and is therefore selected as unswitch candidate If in
            // Loop Unswitching.

            // Use stride > Integer.MAX_VALUE such that LongCountedLoopNode is not split further into loop nests.
            for (long j = 0; j < limit; j+=2147483648L) {
                a.i += 34; // NullCheck with trap on false path -> reason to peel
                if (j > 0) { // After peeling: j > 0 always true -> loop folded away
                    break;
                }
            }
        }
    }

    public static void testCountedLoopEnd() {
        int limit = iFld;
        for (int i = 0; i < 100; i++) {

            // After peeling & IGNV:
            //        CountedLoopEnd
            //           /      \
            //         True    False
            //        / \       /
            //  Store    Region
            //
            // CountedEndLoop has both paths inside loop and is therefore selected as unswitch candidate If in
            // Loop Unswitching.

            for (int j = 0; j < limit; j++) {
                a.i += 34; // NullCheck with trap on false path -> reason to peel
                if (j > 0) { // After peeling: j > 0 always true -> loop folded away
                    break;
                }
            }
        }
    }
}

class A {
    int i;
}