Revert of [turbofan] Add support for copy-on-write element stores.

src/compiler/opcodes.h

 // 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.
 
 #ifndef V8_COMPILER_OPCODES_H_
 #define V8_COMPILER_OPCODES_H_
 
 #include <iosfwd>
 
 // Opcodes for control operators.
@@ skipping 286 matching lines @@
   V(StoreField)                     \
   V(StoreBuffer)                    \
   V(StoreElement)                   \
   V(StoreTypedElement)              \
   V(ObjectIsCallable)               \
   V(ObjectIsNumber)                 \
   V(ObjectIsReceiver)               \
   V(ObjectIsSmi)                    \
   V(ObjectIsString)                 \
   V(ObjectIsUndetectable)           \
-  V(EnsureWritableFastElements)     \
   V(TransitionElementsKind)
 
 #define SIMPLIFIED_OP_LIST(V)                 \
   SIMPLIFIED_CHANGE_OP_LIST(V)                \
   SIMPLIFIED_CHECKED_OP_LIST(V)               \
   SIMPLIFIED_COMPARE_BINOP_LIST(V)            \
   SIMPLIFIED_NUMBER_BINOP_LIST(V)             \
   SIMPLIFIED_SPECULATIVE_NUMBER_BINOP_LIST(V) \
   SIMPLIFIED_NUMBER_UNOP_LIST(V)              \
   SIMPLIFIED_OTHER_OP_LIST(V)
@@ skipping 439 matching lines @@
   }
 };
 
 std::ostream& operator<<(std::ostream&, IrOpcode::Value);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPCODES_H_