Revert of [compiler] Properly validate stable map assumption for globals.

src/crankshaft/hydrogen.cc

 // Copyright 2013 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/crankshaft/hydrogen.h"
 
 #include <memory>
 #include <sstream>
 
 #include "src/allocation-site-scopes.h"
@@ skipping 6504 matching lines @@
       }
     }
     HConstant* cell_constant = Add<HConstant>(cell);
     auto access = HObjectAccess::ForPropertyCellValue();
     if (cell_type == PropertyCellType::kConstantType) {
       switch (cell->GetConstantType()) {
         case PropertyCellConstantType::kSmi:
           access = access.WithRepresentation(Representation::Smi());
           break;
         case PropertyCellConstantType::kStableMap: {
-          // First check that the previous value of the {cell} still has the
-          // map that we are about to check the new {value} for. If not, then
-          // the stable map assumption was invalidated and we cannot continue
-          // with the optimized code.
-          Handle<HeapObject> cell_value(HeapObject::cast(cell->value()));
-          Handle<Map> cell_value_map(cell_value->map());
-          HCheckMaps* cell_value_check = Add<HCheckMaps>(
-              Add<HConstant>(cell_value, Representation::HeapObject()),
-              cell_value_map);
-          cell_value_check->ClearDependsOnFlag(kElementsKind);
-          // Now check that the new {value} is a HeapObject with the same map.
+          // The map may no longer be stable, deopt if it's ever different from
+          // what is currently there, which will allow for restablization.
+          Handle<Map> map(HeapObject::cast(cell->value())->map());
           Add<HCheckHeapObject>(value);
-          value = Add<HCheckMaps>(value, cell_value_map);
+          value = Add<HCheckMaps>(value, map);
           access = access.WithRepresentation(Representation::HeapObject());
           break;
         }
       }
     }
     HInstruction* instr = Add<HStoreNamedField>(cell_constant, access, value);
     instr->ClearChangesFlag(kInobjectFields);
     instr->SetChangesFlag(kGlobalVars);
     if (instr->HasObservableSideEffects()) {
       Add<HSimulate>(ast_id, REMOVABLE_SIMULATE);
@@ skipping 6447 matching lines @@
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 }  // namespace internal
 }  // namespace v8