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8357105: C2: compilation fails with "assert(false) failed: empty program detected during loop optimization"

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Reviewed-by: syan, rcastanedalo
This commit is contained in:
Daniel Skantz 2025-05-26 14:22:12 +00:00
parent bd095896dd
commit a300c35655
2 changed files with 66 additions and 2 deletions
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13
src/hotspot/share/opto/stringopts.cpp
View File

@ -987,12 +987,21 @@ bool StringConcat::validate_control_flow() {
continue;
}
// A test which leads to an uncommon trap which should be safe.
// Later this trap will be converted into a trap that restarts
// A test which leads to an uncommon trap. It is safe to convert the trap
// into a trap that restarts at the beginning as long as its test does not
// depend on intermediate results of the candidate chain.
// at the beginning.
if (otherproj->outcnt() == 1) {
CallStaticJavaNode* call = otherproj->unique_out()->isa_CallStaticJava();
if (call != nullptr && call->_name != nullptr && strcmp(call->_name, "uncommon_trap") == 0) {
// First check for dependency on a toString that is going away during stacked concats.
if (_multiple &&
((v1->is_Proj() && is_SB_toString(v1->in(0)) && ctrl_path.member(v1->in(0))) ||
(v2->is_Proj() && is_SB_toString(v2->in(0)) && ctrl_path.member(v2->in(0))))) {
// iftrue -> if -> bool -> cmpp -> resproj -> tostring
fail = true;
break;
}
// control flow leads to uct so should be ok
_uncommon_traps.push(call);
ctrl_path.push(call);

55
test/hotspot/jtreg/compiler/stringopts/TestStackedConcatsAppendUncommonTrap.java Normal file
View File

@ -0,0 +1,55 @@
/*
* 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 8357105
* @summary Test stacked string concatenations where the toString result
* of the first StringBuilder chain is wired into an uncommon trap
* located in the second one.
* @run main/othervm compiler.stringopts.TestStackedConcatsAppendUncommonTrap
* @run main/othervm -XX:-TieredCompilation -Xbatch
* -XX:CompileOnly=compiler.stringopts.TestStackedConcatsAppendUncommonTrap::*
* compiler.stringopts.TestStackedConcatsAppendUncommonTrap
*/
package compiler.stringopts;
public class TestStackedConcatsAppendUncommonTrap {
public static void main (String... args) {
for (int i = 0; i < 10000; i++) {
String s = f(" ");
if (!s.equals(" ")) {
throw new RuntimeException("wrong result.");
}
}
}
static String f(String c) {
String s = " ";
s = new StringBuilder().append(s).append(s).toString();
s = new StringBuilder().append(s).append(s == c ? s : " ").toString();
return s;
}
}