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8316396: Endless loop in C2 compilation triggered by AddNode::IdealIL

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Reviewed-by: thartmann, kvn
This commit is contained in:
Roland Westrelin 2023-10-04 12:06:31 +00:00
parent a8549b6367
commit b0d6c8472f
2 changed files with 70 additions and 2 deletions
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22
src/hotspot/share/opto/addnode.cpp
View File

@ -280,8 +280,26 @@ Node* AddNode::IdealIL(PhaseGVN* phase, bool can_reshape, BasicType bt) {
assert( in1->in(2) != this && in2->in(2) != this,
"dead loop in AddINode::Ideal" );
Node* sub = SubNode::make(nullptr, nullptr, bt);
sub->init_req(1, phase->transform(AddNode::make(in1->in(1), in2->in(1), bt)));
sub->init_req(2, phase->transform(AddNode::make(in1->in(2), in2->in(2), bt)));
Node* sub_in1;
PhaseIterGVN* igvn = phase->is_IterGVN();
// During IGVN, if both inputs of the new AddNode are a tree of SubNodes, this same transformation will be applied
// to every node of the tree. Calling transform() causes the transformation to be applied recursively, once per
// tree node whether some subtrees are identical or not. Pushing to the IGVN worklist instead, causes the transform
// to be applied once per unique subtrees (because all uses of a subtree are updated with the result of the
// transformation). In case of a large tree, this can make a difference in compilation time.
if (igvn != nullptr) {
sub_in1 = igvn->register_new_node_with_optimizer(AddNode::make(in1->in(1), in2->in(1), bt));
} else {
sub_in1 = phase->transform(AddNode::make(in1->in(1), in2->in(1), bt));
}
Node* sub_in2;
if (igvn != nullptr) {
sub_in2 = igvn->register_new_node_with_optimizer(AddNode::make(in1->in(2), in2->in(2), bt));
} else {
sub_in2 = phase->transform(AddNode::make(in1->in(2), in2->in(2), bt));
}
sub->init_req(1, sub_in1);
sub->init_req(2, sub_in2);
return sub;
}
// Convert "(a-b)+(b+c)" into "(a+c)"

50
test/hotspot/jtreg/compiler/c2/TestLargeTreeOfSubNodes.java Normal file
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@ -0,0 +1,50 @@
/*
* Copyright (c) 2023, 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 8316396
* @summary Endless loop in C2 compilation triggered by AddNode::IdealIL
* @run main/othervm -XX:CompileCommand=compileonly,*TestLargeTreeOfSubNodes*::test -XX:-TieredCompilation -Xcomp TestLargeTreeOfSubNodes
*/
public class TestLargeTreeOfSubNodes {
public static long res = 0;
public static void test() {
int a = -1, b = 0;
for (int i = 0; i < 100; ++i) {
for (int j = 0; j < 10; ++j) {
for (int k = 0; k < 1; ++k) {
}
b -= a;
a += b;
}
}
res = a;
}
public static void main(String[] args) {
test();
}
}