jdk-24/test/hotspot/jtreg/compiler/codegen/TestGCMStorePlacement.java

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package compiler.codegen;

import jdk.test.lib.Asserts;

/**
 * @test
 * @bug 8255763
 * @summary Tests GCM's store placement for reducible and irreducible CFGs.
 * @library /test/lib /
 * @run main/othervm -Xbatch compiler.codegen.TestGCMStorePlacement reducible
 * @run main/othervm -Xbatch compiler.codegen.TestGCMStorePlacement irreducible
 */

public class TestGCMStorePlacement {

    static int counter;

    // Reducible case: counter++ should not be placed into the loop.
    static void testReducible() {
        counter++;
        int acc = 0;
        for (int i = 0; i < 50; i++) {
            if (i % 2 == 0) {
                acc += 1;
            }
        }
        return;
    }

    // Irreducible case (due to OSR compilation): counter++ should not be placed
    // outside its switch case block.
    static void testIrreducible() {
        for (int i = 0; i < 30; i++) {
            switch (i % 3) {
            case 0:
                for (int j = 0; j < 50; j++) {
                    // OSR enters here.
                    for (int k = 0; k < 7000; k++) {}
                    if (i % 2 == 0) {
                        break;
                    }
                }
                counter++;
                break;
            case 1:
                break;
            case 2:
                break;
            }
        }
        return;
    }

    public static void main(String[] args) {
        switch (args[0]) {
        case "reducible":
            // Cause a regular C2 compilation of testReducible.
            for (int i = 0; i < 100_000; i++) {
                counter = 0;
                testReducible();
                Asserts.assertEQ(counter, 1);
            }
            break;
        case "irreducible":
            // Cause an OSR C2 compilation of testIrreducible.
            counter = 0;
            testIrreducible();
            Asserts.assertEQ(counter, 10);
            break;
        default:
            System.out.println("invalid mode");
        }
    }
}