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

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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/**
 * @test
 * @bug 8231988 8293996
 * @summary Unexpected test result caused by C2 IdealLoopTree::do_remove_empty_loop
 *
 * @run main/othervm -XX:-TieredCompilation -XX:-BackgroundCompilation
 *      -XX:+IgnoreUnrecognizedVMOptions -XX:StressLongCountedLoop=0
 *      compiler.loopopts.TestRemoveEmptyLoop
 */

package compiler.loopopts;

public class TestRemoveEmptyLoop {

    public void test_cmp_helper() {
        int i = 34;
        // The empty loop that collapses
        for (; i > 0; i -= 11);
        // If uses same Cmp node as the loop condition
        if (i < 0) {
            // do nothing
        } else {
            throw new RuntimeException("Test failed.");
        }
    }

    public void test_cmp() {
        // Loop is OSR compiled, and test_cmp_helper inlined
        for (int i = 0; i < 50000; i++) {
            test_cmp_helper();
        }
    }

    void test_collapse_helper() {
        int o = 11;
        int e = 43542;
        for (int i = 524; i < 19325; i += 1) {
            // The empty loop that is supposed to collapse
            for (int j = 0; j < 32767; j++) {
                o++;
            }
            for (int k = 0; k < o; k++) {
                e++;
            }
        }
    }

    public void test_collapse() {
        // Loop is OSR compiled, and test_collapse_helper inlined
        for (int i = 0; i < 50000; i++) {
            test_collapse_helper();
        }
    }

    public static void main(String[] args) {
        TestRemoveEmptyLoop _instance = new TestRemoveEmptyLoop();
        _instance.test_cmp();
        _instance.test_collapse();
        System.out.println("Test passed.");
    }
}