8322743: C2: prevent lock region elimination in OSR compilation

Reviewed-by: epeter, dlong, vlivanov

Author: Vladimir Kozlov

src/hotspot/share/opto/compile.cpp

@@ -4879,6 +4879,7 @@ void Compile::add_coarsened_locks(GrowableArray<AbstractLockNode*>& locks) {
         // Locking regions (BoxLock) could be Unbalanced here:
         //  - its coarsened locks were eliminated in earlier
         //    macro nodes elimination followed by loop unroll
+        //  - it is OSR locking region (no Lock node)
         // Preserve Unbalanced status in such cases.
         if (!this_box->is_unbalanced()) {
           this_box->set_coarsened();

src/hotspot/share/opto/parse1.cpp

@@ -224,11 +224,20 @@ void Parse::load_interpreter_state(Node* osr_buf) {
   Node *monitors_addr = basic_plus_adr(osr_buf, osr_buf, (max_locals+mcnt*2-1)*wordSize);
   for (index = 0; index < mcnt; index++) {
     // Make a BoxLockNode for the monitor.
-    Node *box = new BoxLockNode(next_monitor());
+    BoxLockNode* osr_box = new BoxLockNode(next_monitor());
     // Check for bailout after new BoxLockNode
     if (failing()) { return; }
-    box = _gvn.transform(box);
 
+    // This OSR locking region is unbalanced because it does not have Lock node:
+    // locking was done in Interpreter.
+    // This is similar to Coarsened case when Lock node is eliminated
+    // and as result the region is marked as Unbalanced.
+
+    // Emulate Coarsened state transition from Regular to Unbalanced.
+    osr_box->set_coarsened();
+    osr_box->set_unbalanced();
+
+    Node* box = _gvn.transform(osr_box);
 
     // Displaced headers and locked objects are interleaved in the
     // temp OSR buffer.  We only copy the locked objects out here.
@@ -1805,11 +1814,24 @@ void Parse::merge_common(Parse::Block* target, int pnum) {
             const JVMState* jvms = map()->jvms();
             if (EliminateNestedLocks &&
                 jvms->is_mon(j) && jvms->is_monitor_box(j)) {
-              // BoxLock nodes are not commoning.
+              // BoxLock nodes are not commoning when EliminateNestedLocks is on.
               // Use old BoxLock node as merged box.
               assert(newin->jvms()->is_monitor_box(j), "sanity");
               // This assert also tests that nodes are BoxLock.
               assert(BoxLockNode::same_slot(n, m), "sanity");
+              BoxLockNode* old_box = m->as_BoxLock();
+              if (n->as_BoxLock()->is_unbalanced() && !old_box->is_unbalanced()) {
+                // Preserve Unbalanced status.
+                //
+                // `old_box` can have only Regular or Coarsened status
+                // because this code is executed only during Parse phase and
+                // Incremental Inlining before EA and Macro nodes elimination.
+                //
+                // Incremental Inlining is executed after IGVN optimizations
+                // during which BoxLock can be marked as Coarsened.
+                old_box->set_coarsened(); // Verifies state
+                old_box->set_unbalanced();
+              }
               C->gvn_replace_by(n, m);
             } else if (!check_elide_phi || !target->can_elide_SEL_phi(j)) {
               phi = ensure_phi(j, nophi);

test/hotspot/jtreg/compiler/locks/TestLocksInOSR.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2024, 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 8322743
+ * @summary EA incorrectly marks locks for elimination for escaped object which comes from Interpreter in OSR compilation.
+ * @run main/othervm -XX:-TieredCompilation -Xcomp -XX:CompileCommand=compileonly,TestLocksInOSR*::* -XX:CompileCommand=quiet TestLocksInOSR
+ * @run main TestLocksInOSR
+ */
+
+public class TestLocksInOSR {
+
+    public static void main(String[] args) throws Exception {
+        // Triggers assert(this->held_monitor_count() == this->jni_monitor_count()) failed: held monitor count should be equal to jni: 1 != 0
+        test1();
+
+        // Triggers assert(current->held_monitor_count() == 0) failed: Should not be possible
+        test2();
+    }
+
+    static void test1() throws Exception {
+        Thread writeThread = new Thread(new Runnable() {
+            @Override
+            public void run() {
+                for (int i = 0; i < 2; ++i) {
+                    synchronized (new Object()) {
+                        // Trigger OSR compilation
+                        for (int j = 0; j < 100_000; ++j) {
+                          // We still have safepoint left in code
+                        }
+                    }
+                }
+            }
+        });
+        writeThread.start();
+        writeThread.join();
+    }
+
+    static void test2() {
+        for (int i = 0; i < 2; ++i) {
+            synchronized (new Object()) {
+                // Trigger OSR compilation
+                for (int j = 0; j < 100_000; ++j) {
+                  // We still have safepoint left in code
+                }
+            }
+        }
+    }
+}