8321974: Crash in ciKlass::is_subtype_of because TypeAryPtr::_klass is not initialized

Reviewed-by: roland, kvn

src/hotspot/share/opto/type.cpp

@@ -4664,7 +4664,7 @@ template <class T1, class T2>  bool TypePtr::is_meet_subtype_of_helper_for_array
   }
 
   if (other_elem == nullptr && this_elem == nullptr) {
-    return this_one->_klass->is_subtype_of(other->_klass);
+    return this_one->klass()->is_subtype_of(other->klass());
   }
 
   return false;
@@ -5993,7 +5993,7 @@ template <class T1, class T2> bool TypePtr::is_java_subtype_of_helper_for_instan
     return true;
   }
 
-  return this_one->_klass->is_subtype_of(other->_klass) && this_one->_interfaces->contains(other->_interfaces);
+  return this_one->klass()->is_subtype_of(other->klass()) && this_one->_interfaces->contains(other->_interfaces);
 }
 
 bool TypeInstKlassPtr::is_java_subtype_of_helper(const TypeKlassPtr* other, bool this_exact, bool other_exact) const {
@@ -6008,7 +6008,7 @@ template <class T1, class T2> bool TypePtr::is_same_java_type_as_helper_for_inst
   if (!this_one->is_instance_type(other)) {
     return false;
   }
-  return this_one->_klass->equals(other->_klass) && this_one->_interfaces->eq(other->_interfaces);
+  return this_one->klass()->equals(other->klass()) && this_one->_interfaces->eq(other->_interfaces);
 }
 
 bool TypeInstKlassPtr::is_same_java_type_as_helper(const TypeKlassPtr* other) const {
@@ -6022,7 +6022,7 @@ template <class T1, class T2> bool TypePtr::maybe_java_subtype_of_helper_for_ins
   }
 
   if (this_one->is_array_type(other)) {
-    return !this_exact && this_one->_klass->equals(ciEnv::current()->Object_klass())  && other->_interfaces->contains(this_one->_interfaces);
+    return !this_exact && this_one->klass()->equals(ciEnv::current()->Object_klass())  && other->_interfaces->contains(this_one->_interfaces);
   }
 
   assert(this_one->is_instance_type(other), "unsupported");
@@ -6031,12 +6031,12 @@ template <class T1, class T2> bool TypePtr::maybe_java_subtype_of_helper_for_ins
     return this_one->is_java_subtype_of(other);
   }
 
-  if (!this_one->_klass->is_subtype_of(other->_klass) && !other->_klass->is_subtype_of(this_one->_klass)) {
+  if (!this_one->klass()->is_subtype_of(other->klass()) && !other->klass()->is_subtype_of(this_one->klass())) {
     return false;
   }
 
   if (this_exact) {
-    return this_one->_klass->is_subtype_of(other->_klass) && this_one->_interfaces->contains(other->_interfaces);
+    return this_one->klass()->is_subtype_of(other->klass()) && this_one->_interfaces->contains(other->_interfaces);
   }
 
   return true;
@@ -6116,7 +6116,7 @@ uint TypeAryKlassPtr::hash(void) const {
 
 //----------------------compute_klass------------------------------------------
 // Compute the defining klass for this class
-ciKlass* TypeAryPtr::compute_klass(DEBUG_ONLY(bool verify)) const {
+ciKlass* TypeAryPtr::compute_klass() const {
   // Compute _klass based on element type.
   ciKlass* k_ary = nullptr;
   const TypeInstPtr *tinst;
@@ -6137,28 +6137,7 @@ ciKlass* TypeAryPtr::compute_klass(DEBUG_ONLY(bool verify)) const {
     // and object; Top occurs when doing join on Bottom.
     // Leave k_ary at null.
   } else {
-    // Cannot compute array klass directly from basic type,
+    assert(!el->isa_int(), "integral arrays must be pre-equipped with a class");
-    // since subtypes of TypeInt all have basic type T_INT.
-#ifdef ASSERT
-    if (verify && el->isa_int()) {
-      // Check simple cases when verifying klass.
-      BasicType bt = T_ILLEGAL;
-      if (el == TypeInt::BYTE) {
-        bt = T_BYTE;
-      } else if (el == TypeInt::SHORT) {
-        bt = T_SHORT;
-      } else if (el == TypeInt::CHAR) {
-        bt = T_CHAR;
-      } else if (el == TypeInt::INT) {
-        bt = T_INT;
-      } else {
-        return _klass; // just return specified klass
-      }
-      return ciTypeArrayKlass::make(bt);
-    }
-#endif
-    assert(!el->isa_int(),
-           "integral arrays must be pre-equipped with a class");
     // Compute array klass directly from basic type
     k_ary = ciTypeArrayKlass::make(el->basic_type());
   }
@@ -6434,7 +6413,7 @@ template <class T1, class T2> bool TypePtr::is_java_subtype_of_helper_for_array(
     return this_one->is_reference_type(this_elem)->is_java_subtype_of_helper(this_one->is_reference_type(other_elem), this_exact, other_exact);
   }
   if (this_elem == nullptr && other_elem == nullptr) {
-    return this_one->_klass->is_subtype_of(other->_klass);
+    return this_one->klass()->is_subtype_of(other->klass());
   }
   return false;
 }
@@ -6466,8 +6445,7 @@ template <class T1, class T2> bool TypePtr::is_same_java_type_as_helper_for_arra
     return this_one->is_reference_type(this_elem)->is_same_java_type_as(this_one->is_reference_type(other_elem));
   }
   if (other_elem == nullptr && this_elem == nullptr) {
-    assert(this_one->_klass != nullptr && other->_klass != nullptr, "");
+    return this_one->klass()->equals(other->klass());
-    return this_one->_klass->equals(other->_klass);
   }
   return false;
 }
@@ -6487,7 +6465,7 @@ template <class T1, class T2> bool TypePtr::maybe_java_subtype_of_helper_for_arr
     return true;
   }
   if (this_one->is_instance_type(other)) {
-    return other->_klass->equals(ciEnv::current()->Object_klass()) && other->_interfaces->intersection_with(this_one->_interfaces)->eq(other->_interfaces);
+    return other->klass()->equals(ciEnv::current()->Object_klass()) && other->_interfaces->intersection_with(this_one->_interfaces)->eq(other->_interfaces);
   }
   assert(this_one->is_array_type(other), "");
 
@@ -6506,7 +6484,7 @@ template <class T1, class T2> bool TypePtr::maybe_java_subtype_of_helper_for_arr
     return this_one->is_reference_type(this_elem)->maybe_java_subtype_of_helper(this_one->is_reference_type(other_elem), this_exact, other_exact);
   }
   if (other_elem == nullptr && this_elem == nullptr) {
-    return this_one->_klass->is_subtype_of(other->_klass);
+    return this_one->klass()->is_subtype_of(other->klass());
   }
   return false;
 }

src/hotspot/share/opto/type.hpp

@@ -1413,7 +1413,7 @@ class TypeAryPtr : public TypeOopPtr {
   const TypeAry *_ary;          // Array we point into
   const bool     _is_autobox_cache;
 
-  ciKlass* compute_klass(DEBUG_ONLY(bool verify = false)) const;
+  ciKlass* compute_klass() const;
 
   // A pointer to delay allocation to Type::Initialize_shared()
 

test/hotspot/jtreg/compiler/c2/TestUninitializedKlassField.java

@@ -0,0 +1,54 @@
+/*
+ * 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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 8321974
+ * @summary Test that the TypeAryPtr::_klass field is properly initialized on use.
+ * @comment This test only reproduces the issue with release builds of the JVM because
+ *          verification code in debug builds leads to eager initialization of the field.
+ * @run main/othervm -Xbatch -XX:CompileCommand=compileonly,TestUninitializedKlassField::test*
+ *                   -XX:-TieredCompilation TestUninitializedKlassField
+ */
+
+public class TestUninitializedKlassField {
+    static void test(long array2[]) {
+        long array1[] = new long[1];
+        // Loop is needed to create a backedge phi that is processed only during IGVN.
+        for (int i = 0; i < 1; i++) {
+            // CmpPNode::sub will check if classes of array1 and array2 are unrelated
+            // and the subtype checks will crash if the _klass field is not initialized.
+            if (array2 != array1) {
+                array1 = new long[2];
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        for (int i = 0; i < 50_000; ++i) {
+            test(null);
+        }
+    }
+}