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8316361: C2: assert(!failure) failed: Missed optimization opportunity…
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… in PhaseIterGVN with -XX:VerifyIterativeGVN=10

Backport-of: eeb63cd0fad9de1f7182ab97d0f25ac67745aa9e
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MBaesken committed Jul 5, 2024
1 parent b48b8e1 commit 3e638bf
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2 changes: 2 additions & 0 deletions src/hotspot/share/opto/loopTransform.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -2332,6 +2332,8 @@ void PhaseIdealLoop::do_unroll(IdealLoopTree *loop, Node_List &old_new, bool adj
// can edit it's inputs directly. Hammer in the new limit for the
// minimum-trip guard.
assert(opaq->outcnt() == 1, "");
// Notify limit -> opaq -> CmpI, it may constant fold.
_igvn.add_users_to_worklist(opaq->in(1));
_igvn.replace_input_of(opaq, 1, new_limit);
}

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@@ -0,0 +1,48 @@
/*
* Copyright (c) 2023, 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 8316361
* @summary Test that if input to OpaqueZeroTripGuard changes, we notify down to CmpI.
* @run main/othervm -Xcomp -XX:+IgnoreUnrecognizedVMOptions -XX:VerifyIterativeGVN=10
* -XX:CompileCommand=compileonly,compiler.loopopts.TestNotifyOpaqueZeroTripGuardToCmpI::test
* compiler.loopopts.TestNotifyOpaqueZeroTripGuardToCmpI
*/
package compiler.loopopts;

public class TestNotifyOpaqueZeroTripGuardToCmpI {
static int x, y;

public static void main(String[] strArr) {
test();
}

static void test() {
for (int i = 6; i < 43; i++) {
for (int j = i; j < 11; j++) {
x = y;
}
}
}
}

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