8240676: Meet not symmetric failure when running lucene on jdk8

Reviewed-by: kvn, thartmann

src/hotspot/share/opto/compile.cpp

@@ -1009,6 +1009,9 @@ void Compile::Init(int aliaslevel) {
   _range_check_casts = new(comp_arena()) GrowableArray<Node*>(comp_arena(), 8,  0, NULL);
   _opaque4_nodes = new(comp_arena()) GrowableArray<Node*>(comp_arena(), 8,  0, NULL);
   register_library_intrinsics();
+#ifdef ASSERT
+  _type_verify_symmetry = true;
+#endif
 }
 
 //---------------------------init_start----------------------------------------

src/hotspot/share/opto/compile.hpp

@@ -1179,6 +1179,9 @@ class Compile : public Phase {
   bool select_24_bit_instr() const { return _select_24_bit_instr; }
   bool in_24_bit_fp_mode() const   { return _in_24_bit_fp_mode; }
 #endif // IA32
+#ifdef ASSERT
+  bool _type_verify_symmetry;
+#endif
 };
 
 #endif // SHARE_OPTO_COMPILE_HPP

src/hotspot/share/opto/type.cpp

@@ -810,6 +810,35 @@ bool Type::interface_vs_oop(const Type *t) const {
 
 #endif
 
+void Type::check_symmetrical(const Type *t, const Type *mt) const {
+#ifdef ASSERT
+  assert(mt == t->xmeet(this), "meet not commutative");
+  const Type* dual_join = mt->_dual;
+  const Type *t2t    = dual_join->xmeet(t->_dual);
+  const Type *t2this = dual_join->xmeet(this->_dual);
+
+  // Interface meet Oop is Not Symmetric:
+  // Interface:AnyNull meet Oop:AnyNull == Interface:AnyNull
+  // Interface:NotNull meet Oop:NotNull == java/lang/Object:NotNull
+
+  if( !interface_vs_oop(t) && (t2t != t->_dual || t2this != this->_dual) ) {
+    tty->print_cr("=== Meet Not Symmetric ===");
+    tty->print("t   =                   ");              t->dump(); tty->cr();
+    tty->print("this=                   ");                 dump(); tty->cr();
+    tty->print("mt=(t meet this)=       ");             mt->dump(); tty->cr();
+
+    tty->print("t_dual=                 ");       t->_dual->dump(); tty->cr();
+    tty->print("this_dual=              ");          _dual->dump(); tty->cr();
+    tty->print("mt_dual=                ");      mt->_dual->dump(); tty->cr();
+
+    tty->print("mt_dual meet t_dual=    "); t2t           ->dump(); tty->cr();
+    tty->print("mt_dual meet this_dual= "); t2this        ->dump(); tty->cr();
+
+    fatal("meet not symmetric" );
+  }
+#endif
+}
+
 //------------------------------meet-------------------------------------------
 // Compute the MEET of two types.  NOT virtual.  It enforces that meet is
 // commutative and the lattice is symmetric.
@@ -827,33 +856,28 @@ const Type *Type::meet_helper(const Type *t, bool include_speculative) const {
   t = t->maybe_remove_speculative(include_speculative);
 
   const Type *mt = this_t->xmeet(t);
+#ifdef ASSERT
   if (isa_narrowoop() || t->isa_narrowoop()) return mt;
   if (isa_narrowklass() || t->isa_narrowklass()) return mt;
-#ifdef ASSERT
+  Compile* C = Compile::current();
-  assert(mt == t->xmeet(this_t), "meet not commutative");
+  if (!C->_type_verify_symmetry) {
-  const Type* dual_join = mt->_dual;
+    return mt;
-  const Type *t2t    = dual_join->xmeet(t->_dual);
-  const Type *t2this = dual_join->xmeet(this_t->_dual);
-
-  // Interface meet Oop is Not Symmetric:
-  // Interface:AnyNull meet Oop:AnyNull == Interface:AnyNull
-  // Interface:NotNull meet Oop:NotNull == java/lang/Object:NotNull
-
-  if( !interface_vs_oop(t) && (t2t != t->_dual || t2this != this_t->_dual) ) {
-    tty->print_cr("=== Meet Not Symmetric ===");
-    tty->print("t   =                   ");              t->dump(); tty->cr();
-    tty->print("this=                   ");         this_t->dump(); tty->cr();
-    tty->print("mt=(t meet this)=       ");             mt->dump(); tty->cr();
-
-    tty->print("t_dual=                 ");       t->_dual->dump(); tty->cr();
-    tty->print("this_dual=              ");  this_t->_dual->dump(); tty->cr();
-    tty->print("mt_dual=                ");      mt->_dual->dump(); tty->cr();
-
-    tty->print("mt_dual meet t_dual=    "); t2t           ->dump(); tty->cr();
-    tty->print("mt_dual meet this_dual= "); t2this        ->dump(); tty->cr();
-
-    fatal("meet not symmetric" );
   }
+  this_t->check_symmetrical(t, mt);
+  // In the case of an array, computing the meet above, caused the
+  // computation of the meet of the elements which at verification
+  // time caused the computation of the meet of the dual of the
+  // elements. Computing the meet of the dual of the arrays here
+  // causes the meet of the dual of the elements to be computed which
+  // would cause the meet of the dual of the dual of the elements,
+  // that is the meet of the elements already computed above to be
+  // computed. Avoid redundant computations by requesting no
+  // verification.
+  C->_type_verify_symmetry = false;
+  const Type *mt_dual = this_t->_dual->xmeet(t->_dual);
+  this_t->_dual->check_symmetrical(t->_dual, mt_dual);
+  assert(!C->_type_verify_symmetry, "shouldn't have changed");
+  C->_type_verify_symmetry = true;
 #endif
   return mt;
 }
@@ -4315,7 +4339,7 @@ const Type *TypeAryPtr::xmeet_helper(const Type *t) const {
            (tap->_klass_is_exact && !tap->klass()->is_subtype_of(klass())) ||
            // 'this' is exact and super or unrelated:
            (this->_klass_is_exact && !klass()->is_subtype_of(tap->klass())))) {
-      if (above_centerline(ptr)) {
+      if (above_centerline(ptr) || (tary->_elem->make_ptr() && above_centerline(tary->_elem->make_ptr()->_ptr))) {
         tary = TypeAry::make(Type::BOTTOM, tary->_size, tary->_stable);
       }
       return make(NotNull, NULL, tary, lazy_klass, false, off, InstanceBot, speculative, depth);

src/hotspot/share/opto/type.hpp

@@ -166,6 +166,7 @@ private:
 #endif
 
   const Type *meet_helper(const Type *t, bool include_speculative) const;
+  void check_symmetrical(const Type *t, const Type *mt) const;
 
 protected:
   // Each class of type is also identified by its base.

test/hotspot/jtreg/compiler/types/TestArrayMeetNotSymmetrical.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2020, 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 8240676
+ * @summary Meet not symmetric failure when running lucene on jdk8
+ *
+ * @run main/othervm -XX:-BackgroundCompilation TestArrayMeetNotSymmetrical
+ *
+ */
+
+public class TestArrayMeetNotSymmetrical {
+    private static final Object field = new Object[0];
+    private static final Object field2 = new A[0];
+
+    public static void main(String[] args) {
+        Object array = new A[10];
+        for (int i = 0; i < 20_000; i++) {
+            test1(true, 10);
+            test1(false, 10);
+            test2(true);
+            test2(false);
+        }
+    }
+
+    private static Object test1(boolean flag, int len) {
+        Object o;
+        if (flag) {
+            o = field;
+        } else {
+            o = new A[len];
+        }
+        return o;
+    }
+
+    private static Object test2(boolean flag) {
+        Object o;
+        if (flag) {
+            o = field;
+        } else {
+            o = field2;
+        }
+        return o;
+    }
+
+
+    private static class A {
+    }
+}