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8373524: C2: no reachable node should have no use

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Reviewed-by: chagedorn, mhaessig
This commit is contained in:
Roland Westrelin 2025-12-19 08:31:04 +00:00
parent 360777c3ad
commit e72f205ae3
2 changed files with 94 additions and 3 deletions
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8
src/hotspot/share/opto/cfgnode.cpp
View File

@ -2642,7 +2642,7 @@ Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
}
Node* phi = mms.memory();
assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
phi->set_req(i, mms.memory2());
phi->set_req_X(i, mms.memory2(), phase);
}
}
}
@ -2651,7 +2651,9 @@ Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
for (MergeMemStream mms(result); mms.next_non_empty(); ) {
Node* phi = mms.memory();
for (uint i = 1; i < req(); ++i) {
if (phi->in(i) == this) phi->set_req(i, phi);
if (phi->in(i) == this) {
phi->set_req_X(i, phi, phase);
}
}
}
}
@ -2673,7 +2675,7 @@ Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
Node *ii = in(i);
Node *new_in = MemNode::optimize_memory_chain(ii, at, nullptr, phase);
if (ii != new_in ) {
set_req(i, new_in);
set_req_X(i, new_in, phase);
progress = this;
}
}

89
test/hotspot/jtreg/compiler/igvn/TestNodeWithNoUseAfterPhiIdeal.java Normal file
View File

@ -0,0 +1,89 @@
/*
* Copyright (c) 2025 IBM Corporation. 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 8373524
* @summary C2: no reachable node should have no use
* @run main/othervm -Xbatch ${test.main.class}
* @run main ${test.main.class}
*/
package compiler.igvn;
public class TestNodeWithNoUseAfterPhiIdeal {
volatile boolean _mutatorToggle;
boolean _mutatorFlip() {
synchronized (TestNodeWithNoUseAfterPhiIdeal.class) {
_mutatorToggle = new MyBoolean(!_mutatorToggle).v;
return _mutatorToggle;
}
}
class MyBoolean {
boolean v;
MyBoolean(boolean v) {
int N = 32;
for (int i = 0; i < N; i++) {
this.v = v;
}
}
}
int[] arr;
void test() {
int limit = 2;
boolean flag1 = _mutatorFlip();
for (; limit < 4; limit *= 2) {
if (flag1) {
break;
}
}
int zero = 34;
for (int peel = 2; peel < limit; peel++) {
synchronized (TestNodeWithNoUseAfterPhiIdeal.class) {
zero = 0;
}
}
if (zero == 0) {
arr = new int[8];
} else {
int M = 4;
for (int i = 0; i < M; i++) {
boolean flag2 = _mutatorFlip();
boolean flag3 = _mutatorFlip();
if (flag2) {
break;
}
}
}
}
public static void main(String[] args) {
TestNodeWithNoUseAfterPhiIdeal t = new TestNodeWithNoUseAfterPhiIdeal();
for (int i = 0; i < 10_000; i++) {
t.test();
}
}
}