[compiler] Properly validate stable map assumption for globals.

src/compiler/js-global-object-specialization.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/js-global-object-specialization.h"
 
 #include "src/compilation-dependencies.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/js-graph.h"
@@ skipping 178 matching lines @@
           graph()->NewNode(simplified()->CheckIf(), check, effect, control);
       break;
     }
     case PropertyCellType::kConstantType: {
       // Record a code dependency on the cell, and just deoptimize if the new
       // values' type doesn't match the type of the previous value in the cell.
       dependencies()->AssumePropertyCell(property_cell);
       Type* property_cell_value_type;
       MachineRepresentation representation = MachineRepresentation::kTagged;
       if (property_cell_value->IsHeapObject()) {
+        // We cannot do anything if the {property_cell_value}s map is no
+        // longer stable.
+        Handle<Map> property_cell_value_map(
+            Handle<HeapObject>::cast(property_cell_value)->map(), isolate());
+        if (!property_cell_value_map->is_stable()) return NoChange();
+        dependencies()->AssumeMapStable(property_cell_value_map);
+
         // Check that the {value} is a HeapObject.
         value = effect = graph()->NewNode(simplified()->CheckHeapObject(),
                                           value, effect, control);
 
         // Check {value} map agains the {property_cell} map.
-        Handle<Map> property_cell_value_map(
-            Handle<HeapObject>::cast(property_cell_value)->map(), isolate());
         effect = graph()->NewNode(
             simplified()->CheckMaps(1), value,
             jsgraph()->HeapConstant(property_cell_value_map), effect, control);
         property_cell_value_type = Type::OtherInternal();
         representation = MachineRepresentation::kTaggedPointer;
       } else {
         // Check that the {value} is a Smi.
         value = effect =
             graph()->NewNode(simplified()->CheckSmi(), value, effect, control);
         property_cell_value_type = Type::SignedSmall();
@@ skipping 59 matching lines @@
   return jsgraph()->javascript();
 }
 
 SimplifiedOperatorBuilder* JSGlobalObjectSpecialization::simplified() const {
   return jsgraph()->simplified();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8