hotspot/src/share/vm/opto/parseHelper.cpp

rev 6883 : 8057622: java/util/stream/test/org/openjdk/tests/java/util/stream/InfiniteStreamWithLimitOpTest: SEGV inside compiled code (sparc)
Summary: In Parse::array_store_check(), add control edge FROM IfTrue branch of runtime type check of the destination array TO loading _element_klass from destination array.
Reviewed-by: kvn, roland, anoll
Contributed-by: Zoltan Majo <zoltan.majo@oracle.com>

@@ -154,26 +154,47 @@
 
   // Extract the array klass type
   int klass_offset = oopDesc::klass_offset_in_bytes();
   Node* p = basic_plus_adr( ary, ary, klass_offset );
   // p's type is array-of-OOPS plus klass_offset
-  Node* array_klass = _gvn.transform( LoadKlassNode::make(_gvn, immutable_memory(), p, TypeInstPtr::KLASS) );
+  Node* array_klass = _gvn.transform(LoadKlassNode::make(_gvn, NULL, immutable_memory(), p, TypeInstPtr::KLASS));
   // Get the array klass
   const TypeKlassPtr *tak = _gvn.type(array_klass)->is_klassptr();
 
-  // array_klass's type is generally INexact array-of-oop.  Heroically
-  // cast the array klass to EXACT array and uncommon-trap if the cast
-  // fails.
+  // The type of array_klass is usually INexact array-of-oop.  Heroically
+  // cast array_klass to EXACT array and uncommon-trap if the cast fails.
+  // Make constant out of the inexact array klass, but use it only if the cast
+  // succeeds.
   bool always_see_exact_class = false;
   if (MonomorphicArrayCheck
-      && !too_many_traps(Deoptimization::Reason_array_check)) {
+      && !too_many_traps(Deoptimization::Reason_array_check)
+      && !tak->klass_is_exact()
+      && tak != TypeKlassPtr::OBJECT) {
+      // Regarding the fourth condition in the if-statement from above:
+      //
+      // If the compiler has determined that the type of array 'ary' (represented
+      // by 'array_klass') is java/lang/Object, the compiler must not assume that
+      // the array 'ary' is monomorphic.
+      //
+      // If 'ary' were of type java/lang/Object, this arraystore would have to fail,
+      // because it is not possible to perform a arraystore into an object that is not
+      // a "proper" array.
+      //
+      // Therefore, let's obtain at runtime the type of 'ary' and check if we can still
+      // successfully perform the store.
+      //
+      // The implementation reasons for the condition are the following:
+      //
+      // java/lang/Object is the superclass of all arrays, but it is represented by the VM
+      // as an InstanceKlass. The checks generated by gen_checkcast() (see below) expect
+      // 'array_klass' to be ObjArrayKlass, which can result in invalid memory accesses.
+      //
+      // See issue JDK-8057622 for details.
+
     always_see_exact_class = true;
     // (If no MDO at all, hope for the best, until a trap actually occurs.)
-  }
 
-  // Is the array klass is exactly its defined type?
-  if (always_see_exact_class && !tak->klass_is_exact()) {
     // Make a constant out of the inexact array klass
     const TypeKlassPtr *extak = tak->cast_to_exactness(true)->is_klassptr();
     Node* con = makecon(extak);
     Node* cmp = _gvn.transform(new (C) CmpPNode( array_klass, con ));
     Node* bol = _gvn.transform(new (C) BoolNode( cmp, BoolTest::eq ));

@@ -200,15 +221,19 @@
   // Come here for polymorphic array klasses
 
   // Extract the array element class
   int element_klass_offset = in_bytes(ObjArrayKlass::element_klass_offset());
   Node *p2 = basic_plus_adr(array_klass, array_klass, element_klass_offset);
-  Node *a_e_klass = _gvn.transform( LoadKlassNode::make(_gvn, immutable_memory(), p2, tak) );
+  // We are allowed to use the constant type only if cast succeeded. If always_see_exact_class is true,
+  // we must set a control edge from the IfTrue node created by the uncommon_trap above to the
+  // LoadKlassNode.
+  Node* a_e_klass = _gvn.transform(LoadKlassNode::make(_gvn, always_see_exact_class ? control() : NULL,
+                                                       immutable_memory(), p2, tak));
 
   // Check (the hard way) and throw if not a subklass.
   // Result is ignored, we just need the CFG effects.
-  gen_checkcast( obj, a_e_klass );
+  gen_checkcast(obj, a_e_klass);
 }
 
 
 void Parse::emit_guard_for_new(ciInstanceKlass* klass) {
   // Emit guarded new