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/*
* Copyright (c) 2025, 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.
*/
/*
* @test
* @bug 8348572
* @summary Tests where new irreducible loop is introduced by split_if.
*
* @run driver compiler.loopopts.TestSplitIfNewIrreducibleLoop
*
* @run main/othervm -Xcomp -XX:PerMethodTrapLimit=0
* -XX:CompileCommand=compileonly,compiler.loopopts.TestSplitIfNewIrreducibleLoop::test
* compiler.loopopts.TestSplitIfNewIrreducibleLoop
*/
package compiler.loopopts;
public class TestSplitIfNewIrreducibleLoop {
static class A {
public A parent;
}
static class B extends A {}
public static void main(String[] args) {
// Instantiate one each: classes are loaded.
A a = new A();
B b = new B();
test(b);
}
static int test(A parent) {
do {
if (parent instanceof B b) { return 1; }
if (parent != null) { parent = parent.parent; }
if (parent == null) { return 0; }
} while (true);
}
// Before split_if it looks like this (the instanceof check has already been partial peeled):
//
// if (parent instanceof B b) { return 1; }
// do {
// if (parent != null) { parent = parent.parent; }
// if (parent == null) { return 0; }
// if (parent instanceof B b) { return 1; }
// } while (true);
//
//
// Now, we want to split_if the first if in the loop body, like this:
//
// if (parent instanceof B b) { return 1; }
// if (parent != null) { goto LOOP2; } else { goto LOOP1; }
// do {
// :LOOP1
// parent = parent.parent;
// :LOOP2
// if (parent == null) { return 0; }
// if (parent instanceof B b) { return 1; }
// if (parent != null) { goto LOOP2; } else { goto LOOP1; }
// } while (true);
//
// As the comment in ifnode.cpp / split_if says: we know that on the backedge
// "parent" cannot be null, and so we would be able to split the if through
// the region, and on the backedge it would constant fold away, and we would
// only have to check the split if in the loop entry.
//
// Problem: we have introduced an irreducible loop!
}
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