diff --git a/src/hotspot/share/opto/loopUnswitch.cpp b/src/hotspot/share/opto/loopUnswitch.cpp index 8730663239..658729af6c 100644 --- a/src/hotspot/share/opto/loopUnswitch.cpp +++ b/src/hotspot/share/opto/loopUnswitch.cpp @@ -221,11 +221,11 @@ void PhaseIdealLoop::do_unswitching(IdealLoopTree *loop, Node_List &old_new) { // Hardwire the control paths in the loops into if(true) and if(false) _igvn.rehash_node_delayed(unswitch_iff); - short_circuit_if(unswitch_iff, proj_true); + dominated_by(proj_true, unswitch_iff, false, false); IfNode* unswitch_iff_clone = old_new[unswitch_iff->_idx]->as_If(); _igvn.rehash_node_delayed(unswitch_iff_clone); - short_circuit_if(unswitch_iff_clone, proj_false); + dominated_by(proj_false, unswitch_iff_clone, false, false); // Reoptimize loops loop->record_for_igvn(); diff --git a/test/hotspot/jtreg/compiler/loopopts/TestLoopUnswitchingLostCastDependency.java b/test/hotspot/jtreg/compiler/loopopts/TestLoopUnswitchingLostCastDependency.java new file mode 100644 index 0000000000..f660614ccb --- /dev/null +++ b/test/hotspot/jtreg/compiler/loopopts/TestLoopUnswitchingLostCastDependency.java @@ -0,0 +1,83 @@ +/* + * Copyright (c) 2020, Red Hat, Inc. 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 8241900 + * @summary Loop unswitching may cause dependence on null check to be lost + * + * @run main/othervm -XX:-TieredCompilation -XX:-BackgroundCompilation -XX:+StressGCM -XX:+StressLCM TestLoopUnswitchingLostCastDependency + */ + +import java.util.Arrays; + +public class TestLoopUnswitchingLostCastDependency { + private static Object objectField; + + public static void main(String[] args) { + Object[] array = new Object[100]; + Arrays.fill(array, new Object()); + for (int i = 0; i < 20_000; i++) { + array[1] = null; + test(array); + array[1] = new Object(); + objectField = null; + test(array); + array[1] = new Object(); + objectField = new Object(); + test(array); + } + } + + private static void test(Object[] array) { + Object o = objectField; + Object o3 = array[1]; + int j = 0; + for (int i = 1; i < 100; i *= 2) { + Object o2 = array[i]; + // Both branches taken: loop is unswitched. + if (o3 != null) { + if (o2 == null) { + } + // Both branches taken: loop is unswitched next. + if (o != null) { + // CastPP here becomes control dependent on o2 == + // null check above. + if (o.getClass() == Object.class) { + } + // This causes partial peeling. When that happens, + // the o2 == null check becomes redundant with the + // o3 != null check in the peeled iteration. The + // CastPP with o as input that was control + // dependent on the o2 == null check becomes + // control dependent on the o3 != null check, + // above the o != null check. + if (j > 7) { + + } + j++; + } + } + } + } +}