Fix keyed element access wrt string wrappers

src/ic/x64/ic-x64.cc

 // Copyright 2012 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/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/codegen.h"
 #include "src/ic/ic.h"
@@ skipping 523 matching lines @@
   // The generic stub does not perform map checks or handle observed objects.
   __ testb(FieldOperand(r9, Map::kBitFieldOffset),
            Immediate(1 << Map::kIsAccessCheckNeeded | 1 << Map::kIsObserved));
   __ j(not_zero, &slow_with_tagged_index);
   // Check that the key is a smi.
   __ JumpIfNotSmi(key, &maybe_name_key);
   __ SmiToInteger32(key, key);
 
   __ CmpInstanceType(r9, JS_ARRAY_TYPE);
   __ j(equal, &array);
-  // Check that the object is some kind of JSObject.
-  __ CmpInstanceType(r9, FIRST_JS_OBJECT_TYPE);
+  // Check that the object is some kind of JS object EXCEPT JS Value type. In
+  // the case that the object is a value-wrapper object, we enter the runtime
+  // system to make sure that indexing into string objects works as intended.
+  STATIC_ASSERT(JS_VALUE_TYPE < JS_OBJECT_TYPE);
+  __ CmpInstanceType(r9, JS_OBJECT_TYPE);
   __ j(below, &slow);
 
   // Object case: Check key against length in the elements array.
   __ movp(rbx, FieldOperand(receiver, JSObject::kElementsOffset));
   // Check array bounds.
   __ SmiCompareInteger32(FieldOperand(rbx, FixedArray::kLengthOffset), key);
   // rbx: FixedArray
   __ j(above, &fast_object);
 
   // Slow case: call runtime.
@@ skipping 318 matching lines @@
   Condition cc =
       (check == ENABLE_INLINED_SMI_CHECK)
           ? (*jmp_address == Assembler::kJncShortOpcode ? not_zero : zero)
           : (*jmp_address == Assembler::kJnzShortOpcode ? not_carry : carry);
   *jmp_address = static_cast<byte>(Assembler::kJccShortPrefix | cc);
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64