test/hotspot/jtreg/compiler/loopopts/TestOnlyInfiniteLoops.jasm

/*
 * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */


super public class TestOnlyInfiniteLoops
{
    public Method "<init>":"()V"
    stack 2 locals 1
    {
        aload_0;
        invokespecial  Method java/lang/Object."<init>":"()V";
        return;
    }

    static Method test_simple:"(III)I"
    stack 200 locals 10
    {
    // Nested infinite loop, where inner loop eventually
    // looses exit to outer loop. Then, the inner loop
    // floats outside the inner loop. The entry from
    // outer to inner loop now becomes an exit for the
    // outer loop, where it now enters the next loop, that
    // used to be the inner loop.
        iconst_0;
        istore     9;

        iload      0;
        ifeq LEND; // skip

    LOOP1:
        iload      1;
        ifeq LOOP1; // dominates
    LOOP2:
        // SKIP: prevent loop-exit from becoming zero-trip guard
        iload      2;
        ifeq SKIP;
        iinc       9, 1;
    SKIP:
        iload      1;
        ifeq LOOP1; // is dominated
        goto LOOP2;

    LEND:
        iload      9;
        ireturn;
    }
    static Method test_irreducible:"(IIII)V"
    stack 200 locals 200
    {
        iload_0;
        ifeq LEND; // skip

    L1:
        iload      1;
        ifgt MERGE;
    L2:
        iload      2;
        ifge MERGE;
        goto L1;

    MERGE:
        nop;
    LOOP:
        iload      3;
        ifle L2;
        iconst_0; // always true
        ifeq LOOP;
        iconst_0; // always true
        ifeq LOOP;
    INFTY:
        goto INFTY; // infinite loop

    LEND:
        return;
    }
}