jdk-24/test/hotspot/jtreg/compiler/loopopts/PartialPeelingUnswitch.java

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/*
 * @test
 * @bug 8233033
 * @summary Tests if partially peeled statements are not executed before the loop predicates of the unswitched fast loop.
 *
 * @run main/othervm -Xbatch -XX:-TieredCompilation
 *      -XX:CompileCommand=compileonly,compiler.loopopts.PartialPeelingUnswitch::test*
 *      compiler.loopopts.PartialPeelingUnswitch
 */

package compiler.loopopts;

public class PartialPeelingUnswitch {

    public static int iFld;
    public static int x = 42;
    public static int y = 31;
    public static int[] iArr = new int[10];

    public int test() {
        /*
         * The inner loop of this test is first partially peeled and then unswitched. An uncommon trap is hit in one
         * of the cloned loop predicates for the fast loop (set up at unswitching stage). The only partially peeled
         * statement "iFld += 7" was wrongly executed before the predicates (and before the loop itself).
         * When hitting the uncommon trap, "iFld >>= 1" was not yet executed. As a result, the interpreter directly
         * reexecuted "iFld += 7" again. This resulted in a wrong result for "iFld". The fix makes peeled statements
         * control dependant on the cloned loop predicates such that they are executed after them.
         */
        iFld = 13;
        for (int i = 0; i < 8; i++) {
            int j = 10;
            while (--j > 0) {
                iFld += -7;
                switch ((i * 5) + 102) {
                case 120:
                    break;
                case 103:
                    break;
                case 116:
                    break;
                default:
                    iFld >>= 1;
                }
            }
        }
        return iFld;
    }

    public int test2() {
        /*
         * Same nested loop structure as in test() but with more statements that are partially peeled from the inner loop.
         * Afterwards the inner loop is unswitched.
         */
        iFld = 13;
        int k = 0;
        for (int i = 0; i < 8; i++) {
            int j = 10;
            while (--j > 0) {
                // All statements before the switch expression are partially peeled
                iFld += -7;
                x = y + iFld;
                y = iArr[5];
                k = 6;
                iArr[5] = 5;
                iArr[6] += 23;
                iArr[7] = iArr[8] + iArr[6];
                iArr[j] = 34;
                switch ((i * 5) + 102) {
                case 120:
                    break;
                case 103:
                    break;
                case 116:
                    break;
                default:
                    iFld >>= 1;
                }
            }
        }
        return iFld + k;
    }

    public static void main(String[] strArr) {
        PartialPeelingUnswitch _instance = new PartialPeelingUnswitch();
        for (int i = 0; i < 200; i++) {
            int result = _instance.test();
            if (result != -7) {
                throw new RuntimeException("Result should always be -7 but was " + result);
            }
        }

        for (int i = 0; i < 200; i++) {
            int result = _instance.test2();
            check(-1, result);
            check(-7, iFld);
            check(-9, x);
            check(5, y);
            check(5, iArr[5]);
            check(149, iArr[6]);
            check(183, iArr[7]);

            // Reset fields
            for (int j = 0; j < 10; j++) {
                iArr[j] = 0;
            }
            x = 42;
            y = 31;
        }
    }

    public static void check(int expected, int actual) {
        if (expected != actual) {
            throw new RuntimeException("Wrong result, expected: " + expected + ", actual: " + actual);
        }
    }
}