diff --git a/src/builtins/builtins-api.cc b/src/builtins/builtins-api.cc
index 0d0066dfb3..d77bc79238 100644
--- a/src/builtins/builtins-api.cc
+++ b/src/builtins/builtins-api.cc
@@ -223,7 +223,8 @@ MaybeHandle<Object> Builtins::InvokeApiFunction(Isolate* isolate,
     argv[cursor--] = *args[i];
   }
   DCHECK_EQ(cursor, BuiltinArguments::kPaddingOffset);
-  argv[BuiltinArguments::kPaddingOffset] = isolate->heap()->the_hole_value();
+  argv[BuiltinArguments::kPaddingOffset] =
+      ReadOnlyRoots(isolate).the_hole_value();
   argv[BuiltinArguments::kArgcOffset] = Smi::FromInt(frame_argc);
   argv[BuiltinArguments::kTargetOffset] = *function;
   argv[BuiltinArguments::kNewTargetOffset] = *new_target;
@@ -261,7 +262,7 @@ V8_WARN_UNUSED_RESULT static Object* HandleApiCallAsFunctionOrConstructor(
     // right answer.
     new_target = obj;
   } else {
-    new_target = isolate->heap()->undefined_value();
+    new_target = ReadOnlyRoots(isolate).undefined_value();
   }
 
   // Get the invocation callback from the function descriptor that was
@@ -285,7 +286,7 @@ V8_WARN_UNUSED_RESULT static Object* HandleApiCallAsFunctionOrConstructor(
                                      args.length() - 1);
     Handle<Object> result_handle = custom.Call(call_data);
     if (result_handle.is_null()) {
-      result = isolate->heap()->undefined_value();
+      result = ReadOnlyRoots(isolate).undefined_value();
     } else {
       result = *result_handle;
     }
diff --git a/src/builtins/builtins-array.cc b/src/builtins/builtins-array.cc
index a109fa62e7..7dcba4262b 100644
--- a/src/builtins/builtins-array.cc
+++ b/src/builtins/builtins-array.cc
@@ -177,7 +177,7 @@ BUILTIN(ArrayPop) {
   Handle<JSArray> array = Handle<JSArray>::cast(receiver);
 
   uint32_t len = static_cast<uint32_t>(Smi::ToInt(array->length()));
-  if (len == 0) return isolate->heap()->undefined_value();
+  if (len == 0) return ReadOnlyRoots(isolate).undefined_value();
 
   if (JSArray::HasReadOnlyLength(array)) {
     return CallJsIntrinsic(isolate, isolate->array_pop(), args);
@@ -208,7 +208,7 @@ BUILTIN(ArrayShift) {
   Handle<JSArray> array = Handle<JSArray>::cast(receiver);
 
   int len = Smi::ToInt(array->length());
-  if (len == 0) return heap->undefined_value();
+  if (len == 0) return ReadOnlyRoots(heap).undefined_value();
 
   if (JSArray::HasReadOnlyLength(array)) {
     return CallJsIntrinsic(isolate, isolate->array_shift(), args);
@@ -962,7 +962,7 @@ Object* Slow_ArrayConcat(BuiltinArguments* args, Handle<Object> species,
             }
             case HOLEY_SMI_ELEMENTS:
             case PACKED_SMI_ELEMENTS: {
-              Object* the_hole = isolate->heap()->the_hole_value();
+              Object* the_hole = ReadOnlyRoots(isolate).the_hole_value();
               FixedArray* elements(FixedArray::cast(array->elements()));
               for (uint32_t i = 0; i < length; i++) {
                 Object* element = elements->get(i);
@@ -1018,14 +1018,14 @@ Object* Slow_ArrayConcat(BuiltinArguments* args, Handle<Object> species,
   for (int i = 0; i < argument_count; i++) {
     Handle<Object> obj((*args)[i], isolate);
     Maybe<bool> spreadable = IsConcatSpreadable(isolate, obj);
-    MAYBE_RETURN(spreadable, isolate->heap()->exception());
+    MAYBE_RETURN(spreadable, ReadOnlyRoots(isolate).exception());
     if (spreadable.FromJust()) {
       Handle<JSReceiver> object = Handle<JSReceiver>::cast(obj);
       if (!IterateElements(isolate, object, &visitor)) {
-        return isolate->heap()->exception();
+        return ReadOnlyRoots(isolate).exception();
       }
     } else {
-      if (!visitor.visit(0, obj)) return isolate->heap()->exception();
+      if (!visitor.visit(0, obj)) return ReadOnlyRoots(isolate).exception();
       visitor.increase_index_offset(1);
     }
   }
@@ -1125,7 +1125,8 @@ BUILTIN(ArrayConcat) {
     if (Fast_ArrayConcat(isolate, &args).ToHandle(&result_array)) {
       return *result_array;
     }
-    if (isolate->has_pending_exception()) return isolate->heap()->exception();
+    if (isolate->has_pending_exception())
+      return ReadOnlyRoots(isolate).exception();
   }
   // Reading @@species happens before anything else with a side effect, so
   // we can do it here to determine whether to take the fast path.
@@ -1136,7 +1137,8 @@ BUILTIN(ArrayConcat) {
     if (Fast_ArrayConcat(isolate, &args).ToHandle(&result_array)) {
       return *result_array;
     }
-    if (isolate->has_pending_exception()) return isolate->heap()->exception();
+    if (isolate->has_pending_exception())
+      return ReadOnlyRoots(isolate).exception();
   }
   return Slow_ArrayConcat(&args, species, isolate);
 }
diff --git a/src/builtins/builtins-callsite.cc b/src/builtins/builtins-callsite.cc
index 5ce0aa0155..ff04fa2dbe 100644
--- a/src/builtins/builtins-callsite.cc
+++ b/src/builtins/builtins-callsite.cc
@@ -28,7 +28,7 @@ namespace {
 
 Object* PositiveNumberOrNull(int value, Isolate* isolate) {
   if (value >= 0) return *isolate->factory()->NewNumberFromInt(value);
-  return isolate->heap()->null_value();
+  return ReadOnlyRoots(isolate).null_value();
 }
 
 Handle<FrameArray> GetFrameArray(Isolate* isolate, Handle<JSObject> object) {
@@ -76,7 +76,7 @@ BUILTIN(CallSitePrototypeGetFunction) {
                         GetFrameIndex(isolate, recv));
 
   StackFrameBase* frame = it.Frame();
-  if (frame->IsStrict()) return isolate->heap()->undefined_value();
+  if (frame->IsStrict()) return ReadOnlyRoots(isolate).undefined_value();
   return *frame->GetFunction();
 }
 
@@ -127,7 +127,7 @@ BUILTIN(CallSitePrototypeGetThis) {
                         GetFrameIndex(isolate, recv));
 
   StackFrameBase* frame = it.Frame();
-  if (frame->IsStrict()) return isolate->heap()->undefined_value();
+  if (frame->IsStrict()) return ReadOnlyRoots(isolate).undefined_value();
   return *frame->GetReceiver();
 }
 
diff --git a/src/builtins/builtins-collections.cc b/src/builtins/builtins-collections.cc
index d8c306b593..9a642e7d3b 100644
--- a/src/builtins/builtins-collections.cc
+++ b/src/builtins/builtins-collections.cc
@@ -15,7 +15,7 @@ BUILTIN(MapPrototypeClear) {
   const char* const kMethodName = "Map.prototype.clear";
   CHECK_RECEIVER(JSMap, map, kMethodName);
   JSMap::Clear(isolate, map);
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 BUILTIN(SetPrototypeClear) {
@@ -23,7 +23,7 @@ BUILTIN(SetPrototypeClear) {
   const char* const kMethodName = "Set.prototype.clear";
   CHECK_RECEIVER(JSSet, set, kMethodName);
   JSSet::Clear(isolate, set);
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 }  // namespace internal
diff --git a/src/builtins/builtins-console.cc b/src/builtins/builtins-console.cc
index 5e459024c0..e19aefd273 100644
--- a/src/builtins/builtins-console.cc
+++ b/src/builtins/builtins-console.cc
@@ -78,7 +78,7 @@ void LogTimerEvent(Isolate* isolate, BuiltinArguments args,
   BUILTIN(Console##call) {                                     \
     ConsoleCall(isolate, args, &debug::ConsoleDelegate::call); \
     RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);            \
-    return isolate->heap()->undefined_value();                 \
+    return ReadOnlyRoots(isolate).undefined_value();           \
   }
 CONSOLE_METHOD_LIST(CONSOLE_BUILTIN_IMPLEMENTATION)
 #undef CONSOLE_BUILTIN_IMPLEMENTATION
@@ -87,21 +87,21 @@ BUILTIN(ConsoleTime) {
   LogTimerEvent(isolate, args, Logger::START);
   ConsoleCall(isolate, args, &debug::ConsoleDelegate::Time);
   RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 BUILTIN(ConsoleTimeEnd) {
   LogTimerEvent(isolate, args, Logger::END);
   ConsoleCall(isolate, args, &debug::ConsoleDelegate::TimeEnd);
   RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 BUILTIN(ConsoleTimeStamp) {
   LogTimerEvent(isolate, args, Logger::STAMP);
   ConsoleCall(isolate, args, &debug::ConsoleDelegate::TimeStamp);
   RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 namespace {
diff --git a/src/builtins/builtins-date.cc b/src/builtins/builtins-date.cc
index 47e8a917c7..e6d5846cc7 100644
--- a/src/builtins/builtins-date.cc
+++ b/src/builtins/builtins-date.cc
@@ -872,7 +872,7 @@ BUILTIN(DatePrototypeToJson) {
       isolate, primitive,
       Object::ToPrimitive(receiver_obj, ToPrimitiveHint::kNumber));
   if (primitive->IsNumber() && !std::isfinite(primitive->Number())) {
-    return isolate->heap()->null_value();
+    return ReadOnlyRoots(isolate).null_value();
   } else {
     Handle<String> name =
         isolate->factory()->NewStringFromAsciiChecked("toISOString");
diff --git a/src/builtins/builtins-error.cc b/src/builtins/builtins-error.cc
index 4e5276484f..0043c42810 100644
--- a/src/builtins/builtins-error.cc
+++ b/src/builtins/builtins-error.cc
@@ -75,7 +75,7 @@ BUILTIN(ErrorCaptureStackTrace) {
 
   RETURN_FAILURE_ON_EXCEPTION(
       isolate, JSObject::SetAccessor(object, name, error_stack, DONT_ENUM));
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 // ES6 section 19.5.3.4 Error.prototype.toString ( )
diff --git a/src/builtins/builtins-function.cc b/src/builtins/builtins-function.cc
index 0e2d82a45d..d0e96847c9 100644
--- a/src/builtins/builtins-function.cc
+++ b/src/builtins/builtins-function.cc
@@ -237,7 +237,7 @@ Object* DoFunctionBind(Isolate* isolate, BuiltinArguments args) {
     Handle<Object> length(Smi::kZero, isolate);
     Maybe<PropertyAttributes> attributes =
         JSReceiver::GetPropertyAttributes(&length_lookup);
-    if (attributes.IsNothing()) return isolate->heap()->exception();
+    if (attributes.IsNothing()) return ReadOnlyRoots(isolate).exception();
     if (attributes.FromJust() != ABSENT) {
       Handle<Object> target_length;
       ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, target_length,
@@ -305,7 +305,7 @@ BUILTIN(FunctionPrototypeToString) {
   // receivers for this method.
   if (FLAG_harmony_function_tostring && receiver->IsJSReceiver() &&
       JSReceiver::cast(*receiver)->map()->is_callable()) {
-    return isolate->heap()->function_native_code_string();
+    return ReadOnlyRoots(isolate).function_native_code_string();
   }
   THROW_NEW_ERROR_RETURN_FAILURE(
       isolate, NewTypeError(MessageTemplate::kNotGeneric,
diff --git a/src/builtins/builtins-global.cc b/src/builtins/builtins-global.cc
index 4d3337f213..3c71a322f9 100644
--- a/src/builtins/builtins-global.cc
+++ b/src/builtins/builtins-global.cc
@@ -89,7 +89,7 @@ BUILTIN(GlobalEval) {
   if (!x->IsString()) return *x;
   if (!Builtins::AllowDynamicFunction(isolate, target, target_global_proxy)) {
     isolate->CountUsage(v8::Isolate::kFunctionConstructorReturnedUndefined);
-    return isolate->heap()->undefined_value();
+    return ReadOnlyRoots(isolate).undefined_value();
   }
   Handle<JSFunction> function;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
diff --git a/src/builtins/builtins-internal.cc b/src/builtins/builtins-internal.cc
index 810d6e930d..3a1eb078d0 100644
--- a/src/builtins/builtins-internal.cc
+++ b/src/builtins/builtins-internal.cc
@@ -15,7 +15,7 @@ BUILTIN(Illegal) {
   UNREACHABLE();
 }
 
-BUILTIN(EmptyFunction) { return isolate->heap()->undefined_value(); }
+BUILTIN(EmptyFunction) { return ReadOnlyRoots(isolate).undefined_value(); }
 
 BUILTIN(UnsupportedThrower) {
   HandleScope scope(isolate);
diff --git a/src/builtins/builtins-intl.cc b/src/builtins/builtins-intl.cc
index 6227c94a14..2a62dcb8b8 100644
--- a/src/builtins/builtins-intl.cc
+++ b/src/builtins/builtins-intl.cc
@@ -105,7 +105,7 @@ BUILTIN(StringPrototypeNormalizeIntl) {
   }
 
   if (U_FAILURE(status)) {
-    return isolate->heap()->undefined_value();
+    return ReadOnlyRoots(isolate).undefined_value();
   }
 
   RETURN_RESULT_OR_FAILURE(
@@ -259,7 +259,7 @@ Object* FormatNumberToParts(Isolate* isolate, icu::NumberFormat* fmt,
   icu::FieldPositionIterator fp_iter;
   UErrorCode status = U_ZERO_ERROR;
   fmt->format(number, formatted, &fp_iter, status);
-  if (U_FAILURE(status)) return isolate->heap()->undefined_value();
+  if (U_FAILURE(status)) return ReadOnlyRoots(isolate).undefined_value();
 
   Handle<JSArray> result = factory->NewJSArray(0);
   int32_t length = formatted.length();
@@ -291,7 +291,7 @@ Object* FormatNumberToParts(Isolate* isolate, icu::NumberFormat* fmt,
             : IcuNumberFieldIdToNumberType(part.field_id, number, isolate);
     if (!AddElement(result, index, field_type_string, formatted, part.begin_pos,
                     part.end_pos, isolate)) {
-      return isolate->heap()->undefined_value();
+      return ReadOnlyRoots(isolate).undefined_value();
     }
     ++index;
   }
@@ -309,7 +309,7 @@ Object* FormatDateToParts(Isolate* isolate, icu::DateFormat* format,
   icu::FieldPosition fp;
   UErrorCode status = U_ZERO_ERROR;
   format->format(date_value, formatted, &fp_iter, status);
-  if (U_FAILURE(status)) return isolate->heap()->undefined_value();
+  if (U_FAILURE(status)) return ReadOnlyRoots(isolate).undefined_value();
 
   Handle<JSArray> result = factory->NewJSArray(0);
   int32_t length = formatted.length();
@@ -324,14 +324,14 @@ Object* FormatDateToParts(Isolate* isolate, icu::DateFormat* format,
     if (previous_end_pos < begin_pos) {
       if (!AddElement(result, index, IcuDateFieldIdToDateType(-1, isolate),
                       formatted, previous_end_pos, begin_pos, isolate)) {
-        return isolate->heap()->undefined_value();
+        return ReadOnlyRoots(isolate).undefined_value();
       }
       ++index;
     }
     if (!AddElement(result, index,
                     IcuDateFieldIdToDateType(fp.getField(), isolate), formatted,
                     begin_pos, end_pos, isolate)) {
-      return isolate->heap()->undefined_value();
+      return ReadOnlyRoots(isolate).undefined_value();
     }
     previous_end_pos = end_pos;
     ++index;
@@ -339,7 +339,7 @@ Object* FormatDateToParts(Isolate* isolate, icu::DateFormat* format,
   if (previous_end_pos < length) {
     if (!AddElement(result, index, IcuDateFieldIdToDateType(-1, isolate),
                     formatted, previous_end_pos, length, isolate)) {
-      return isolate->heap()->undefined_value();
+      return ReadOnlyRoots(isolate).undefined_value();
     }
   }
   JSObject::ValidateElements(*result);
diff --git a/src/builtins/builtins-math.cc b/src/builtins/builtins-math.cc
index d390b5db31..df310bdfa1 100644
--- a/src/builtins/builtins-math.cc
+++ b/src/builtins/builtins-math.cc
@@ -43,7 +43,7 @@ BUILTIN(MathHypot) {
   }
 
   if (one_arg_is_nan) {
-    return isolate->heap()->nan_value();
+    return ReadOnlyRoots(isolate).nan_value();
   }
 
   if (max == 0) {
diff --git a/src/builtins/builtins-number.cc b/src/builtins/builtins-number.cc
index 46aa051484..7e701c1546 100644
--- a/src/builtins/builtins-number.cc
+++ b/src/builtins/builtins-number.cc
@@ -39,10 +39,10 @@ BUILTIN(NumberPrototypeToExponential) {
       isolate, fraction_digits, Object::ToInteger(isolate, fraction_digits));
   double const fraction_digits_number = fraction_digits->Number();
 
-  if (std::isnan(value_number)) return isolate->heap()->NaN_string();
+  if (std::isnan(value_number)) return ReadOnlyRoots(isolate).NaN_string();
   if (std::isinf(value_number)) {
-    return (value_number < 0.0) ? isolate->heap()->minus_Infinity_string()
-                                : isolate->heap()->Infinity_string();
+    return (value_number < 0.0) ? ReadOnlyRoots(isolate).minus_Infinity_string()
+                                : ReadOnlyRoots(isolate).Infinity_string();
   }
   if (fraction_digits_number < 0.0 ||
       fraction_digits_number > kMaxFractionDigits) {
@@ -93,10 +93,10 @@ BUILTIN(NumberPrototypeToFixed) {
                                    "toFixed() digits")));
   }
 
-  if (std::isnan(value_number)) return isolate->heap()->NaN_string();
+  if (std::isnan(value_number)) return ReadOnlyRoots(isolate).NaN_string();
   if (std::isinf(value_number)) {
-    return (value_number < 0.0) ? isolate->heap()->minus_Infinity_string()
-                                : isolate->heap()->Infinity_string();
+    return (value_number < 0.0) ? ReadOnlyRoots(isolate).minus_Infinity_string()
+                                : ReadOnlyRoots(isolate).Infinity_string();
   }
   char* const str = DoubleToFixedCString(
       value_number, static_cast<int>(fraction_digits_number));
@@ -155,10 +155,10 @@ BUILTIN(NumberPrototypeToPrecision) {
                                      Object::ToInteger(isolate, precision));
   double const precision_number = precision->Number();
 
-  if (std::isnan(value_number)) return isolate->heap()->NaN_string();
+  if (std::isnan(value_number)) return ReadOnlyRoots(isolate).NaN_string();
   if (std::isinf(value_number)) {
-    return (value_number < 0.0) ? isolate->heap()->minus_Infinity_string()
-                                : isolate->heap()->Infinity_string();
+    return (value_number < 0.0) ? ReadOnlyRoots(isolate).minus_Infinity_string()
+                                : ReadOnlyRoots(isolate).Infinity_string();
   }
   if (precision_number < 1.0 || precision_number > kMaxFractionDigits) {
     THROW_NEW_ERROR_RETURN_FAILURE(
@@ -219,10 +219,10 @@ BUILTIN(NumberPrototypeToString) {
   }
 
   // Slow case.
-  if (std::isnan(value_number)) return isolate->heap()->NaN_string();
+  if (std::isnan(value_number)) return ReadOnlyRoots(isolate).NaN_string();
   if (std::isinf(value_number)) {
-    return (value_number < 0.0) ? isolate->heap()->minus_Infinity_string()
-                                : isolate->heap()->Infinity_string();
+    return (value_number < 0.0) ? ReadOnlyRoots(isolate).minus_Infinity_string()
+                                : ReadOnlyRoots(isolate).Infinity_string();
   }
   char* const str =
       DoubleToRadixCString(value_number, static_cast<int>(radix_number));
diff --git a/src/builtins/builtins-object.cc b/src/builtins/builtins-object.cc
index 83447860e3..927161d45f 100644
--- a/src/builtins/builtins-object.cc
+++ b/src/builtins/builtins-object.cc
@@ -29,8 +29,8 @@ BUILTIN(ObjectPrototypePropertyIsEnumerable) {
       isolate, object, JSReceiver::ToObject(isolate, args.receiver()));
   Maybe<PropertyAttributes> maybe =
       JSReceiver::GetOwnPropertyAttributes(object, name);
-  if (maybe.IsNothing()) return isolate->heap()->exception();
-  if (maybe.FromJust() == ABSENT) return isolate->heap()->false_value();
+  if (maybe.IsNothing()) return ReadOnlyRoots(isolate).exception();
+  if (maybe.FromJust() == ABSENT) return ReadOnlyRoots(isolate).false_value();
   return isolate->heap()->ToBoolean((maybe.FromJust() & DONT_ENUM) == 0);
 }
 
@@ -92,12 +92,12 @@ Object* ObjectDefineAccessor(Isolate* isolate, Handle<Object> object,
   // throwing an exception.
   Maybe<bool> success = JSReceiver::DefineOwnProperty(isolate, receiver, name,
                                                       &desc, kThrowOnError);
-  MAYBE_RETURN(success, isolate->heap()->exception());
+  MAYBE_RETURN(success, ReadOnlyRoots(isolate).exception());
   if (!success.FromJust()) {
     isolate->CountUsage(v8::Isolate::kDefineGetterOrSetterWouldThrow);
   }
   // 6. Return undefined.
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 Object* ObjectLookupAccessor(Isolate* isolate, Handle<Object> object,
@@ -123,13 +123,13 @@ Object* ObjectLookupAccessor(Isolate* isolate, Handle<Object> object,
         if (it.HasAccess()) continue;
         isolate->ReportFailedAccessCheck(it.GetHolder<JSObject>());
         RETURN_FAILURE_IF_SCHEDULED_EXCEPTION(isolate);
-        return isolate->heap()->undefined_value();
+        return ReadOnlyRoots(isolate).undefined_value();
 
       case LookupIterator::JSPROXY: {
         PropertyDescriptor desc;
         Maybe<bool> found = JSProxy::GetOwnPropertyDescriptor(
             isolate, it.GetHolder<JSProxy>(), it.GetName(), &desc);
-        MAYBE_RETURN(found, isolate->heap()->exception());
+        MAYBE_RETURN(found, ReadOnlyRoots(isolate).exception());
         if (found.FromJust()) {
           if (component == ACCESSOR_GETTER && desc.has_get()) {
             return *desc.get();
@@ -137,20 +137,20 @@ Object* ObjectLookupAccessor(Isolate* isolate, Handle<Object> object,
           if (component == ACCESSOR_SETTER && desc.has_set()) {
             return *desc.set();
           }
-          return isolate->heap()->undefined_value();
+          return ReadOnlyRoots(isolate).undefined_value();
         }
         Handle<Object> prototype;
         ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
             isolate, prototype, JSProxy::GetPrototype(it.GetHolder<JSProxy>()));
         if (prototype->IsNull(isolate)) {
-          return isolate->heap()->undefined_value();
+          return ReadOnlyRoots(isolate).undefined_value();
         }
         return ObjectLookupAccessor(isolate, prototype, key, component);
       }
 
       case LookupIterator::INTEGER_INDEXED_EXOTIC:
       case LookupIterator::DATA:
-        return isolate->heap()->undefined_value();
+        return ReadOnlyRoots(isolate).undefined_value();
 
       case LookupIterator::ACCESSOR: {
         Handle<Object> maybe_pair = it.GetAccessors();
@@ -162,7 +162,7 @@ Object* ObjectLookupAccessor(Isolate* isolate, Handle<Object> object,
     }
   }
 
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 }  // namespace
@@ -212,7 +212,7 @@ BUILTIN(ObjectFreeze) {
   if (object->IsJSReceiver()) {
     MAYBE_RETURN(JSReceiver::SetIntegrityLevel(Handle<JSReceiver>::cast(object),
                                                FROZEN, kThrowOnError),
-                 isolate->heap()->exception());
+                 ReadOnlyRoots(isolate).exception());
   }
   return *object;
 }
@@ -257,7 +257,7 @@ BUILTIN(ObjectSetPrototypeOf) {
   // 4. Let status be ? O.[[SetPrototypeOf]](proto).
   // 5. If status is false, throw a TypeError exception.
   MAYBE_RETURN(JSReceiver::SetPrototype(receiver, proto, true, kThrowOnError),
-               isolate->heap()->exception());
+               ReadOnlyRoots(isolate).exception());
 
   // 6. Return O.
   return *receiver;
@@ -291,20 +291,20 @@ BUILTIN(ObjectPrototypeSetProto) {
   // 2. If Type(proto) is neither Object nor Null, return undefined.
   Handle<Object> proto = args.at(1);
   if (!proto->IsNull(isolate) && !proto->IsJSReceiver()) {
-    return isolate->heap()->undefined_value();
+    return ReadOnlyRoots(isolate).undefined_value();
   }
 
   // 3. If Type(O) is not Object, return undefined.
-  if (!object->IsJSReceiver()) return isolate->heap()->undefined_value();
+  if (!object->IsJSReceiver()) return ReadOnlyRoots(isolate).undefined_value();
   Handle<JSReceiver> receiver = Handle<JSReceiver>::cast(object);
 
   // 4. Let status be ? O.[[SetPrototypeOf]](proto).
   // 5. If status is false, throw a TypeError exception.
   MAYBE_RETURN(JSReceiver::SetPrototype(receiver, proto, true, kThrowOnError),
-               isolate->heap()->exception());
+               ReadOnlyRoots(isolate).exception());
 
   // Return undefined.
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 namespace {
@@ -339,7 +339,7 @@ BUILTIN(ObjectIsExtensible) {
       object->IsJSReceiver()
           ? JSReceiver::IsExtensible(Handle<JSReceiver>::cast(object))
           : Just(false);
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return isolate->heap()->ToBoolean(result.FromJust());
 }
 
@@ -351,7 +351,7 @@ BUILTIN(ObjectIsFrozen) {
                            ? JSReceiver::TestIntegrityLevel(
                                  Handle<JSReceiver>::cast(object), FROZEN)
                            : Just(true);
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return isolate->heap()->ToBoolean(result.FromJust());
 }
 
@@ -363,7 +363,7 @@ BUILTIN(ObjectIsSealed) {
                            ? JSReceiver::TestIntegrityLevel(
                                  Handle<JSReceiver>::cast(object), SEALED)
                            : Just(true);
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return isolate->heap()->ToBoolean(result.FromJust());
 }
 
@@ -389,7 +389,7 @@ BUILTIN(ObjectGetOwnPropertyDescriptors) {
     PropertyDescriptor descriptor;
     Maybe<bool> did_get_descriptor = JSReceiver::GetOwnPropertyDescriptor(
         isolate, receiver, key, &descriptor);
-    MAYBE_RETURN(did_get_descriptor, isolate->heap()->exception());
+    MAYBE_RETURN(did_get_descriptor, ReadOnlyRoots(isolate).exception());
 
     if (!did_get_descriptor.FromJust()) continue;
     Handle<Object> from_descriptor = descriptor.ToObject(isolate);
@@ -411,7 +411,7 @@ BUILTIN(ObjectPreventExtensions) {
   if (object->IsJSReceiver()) {
     MAYBE_RETURN(JSReceiver::PreventExtensions(Handle<JSReceiver>::cast(object),
                                                kThrowOnError),
-                 isolate->heap()->exception());
+                 ReadOnlyRoots(isolate).exception());
   }
   return *object;
 }
@@ -423,7 +423,7 @@ BUILTIN(ObjectSeal) {
   if (object->IsJSReceiver()) {
     MAYBE_RETURN(JSReceiver::SetIntegrityLevel(Handle<JSReceiver>::cast(object),
                                                SEALED, kThrowOnError),
-                 isolate->heap()->exception());
+                 ReadOnlyRoots(isolate).exception());
   }
   return *object;
 }
diff --git a/src/builtins/builtins-reflect.cc b/src/builtins/builtins-reflect.cc
index bc596e0ccb..cc97caf6a9 100644
--- a/src/builtins/builtins-reflect.cc
+++ b/src/builtins/builtins-reflect.cc
@@ -38,12 +38,12 @@ BUILTIN(ReflectDefineProperty) {
 
   PropertyDescriptor desc;
   if (!PropertyDescriptor::ToPropertyDescriptor(isolate, attributes, &desc)) {
-    return isolate->heap()->exception();
+    return ReadOnlyRoots(isolate).exception();
   }
 
   Maybe<bool> result = JSReceiver::DefineOwnProperty(
       isolate, Handle<JSReceiver>::cast(target), name, &desc, kDontThrow);
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return *isolate->factory()->ToBoolean(result.FromJust());
 }
 
@@ -67,7 +67,7 @@ BUILTIN(ReflectDeleteProperty) {
 
   Maybe<bool> result = JSReceiver::DeletePropertyOrElement(
       Handle<JSReceiver>::cast(target), name, LanguageMode::kSloppy);
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return *isolate->factory()->ToBoolean(result.FromJust());
 }
 
@@ -115,8 +115,8 @@ BUILTIN(ReflectGetOwnPropertyDescriptor) {
   PropertyDescriptor desc;
   Maybe<bool> found = JSReceiver::GetOwnPropertyDescriptor(
       isolate, Handle<JSReceiver>::cast(target), name, &desc);
-  MAYBE_RETURN(found, isolate->heap()->exception());
-  if (!found.FromJust()) return isolate->heap()->undefined_value();
+  MAYBE_RETURN(found, ReadOnlyRoots(isolate).exception());
+  if (!found.FromJust()) return ReadOnlyRoots(isolate).undefined_value();
   return *desc.ToObject(isolate);
 }
 
@@ -152,7 +152,7 @@ BUILTIN(ReflectIsExtensible) {
 
   Maybe<bool> result =
       JSReceiver::IsExtensible(Handle<JSReceiver>::cast(target));
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return *isolate->factory()->ToBoolean(result.FromJust());
 }
 
@@ -193,7 +193,7 @@ BUILTIN(ReflectPreventExtensions) {
 
   Maybe<bool> result = JSReceiver::PreventExtensions(
       Handle<JSReceiver>::cast(target), kDontThrow);
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return *isolate->factory()->ToBoolean(result.FromJust());
 }
 
@@ -220,7 +220,7 @@ BUILTIN(ReflectSet) {
       isolate, receiver, name, Handle<JSReceiver>::cast(target));
   Maybe<bool> result = Object::SetSuperProperty(
       &it, value, LanguageMode::kSloppy, Object::MAY_BE_STORE_FROM_KEYED);
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return *isolate->factory()->ToBoolean(result.FromJust());
 }
 
@@ -245,7 +245,7 @@ BUILTIN(ReflectSetPrototypeOf) {
 
   Maybe<bool> result = JSReceiver::SetPrototype(
       Handle<JSReceiver>::cast(target), proto, true, kDontThrow);
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return *isolate->factory()->ToBoolean(result.FromJust());
 }
 
diff --git a/src/builtins/builtins-regexp.cc b/src/builtins/builtins-regexp.cc
index 3c24f30abc..86bf06b658 100644
--- a/src/builtins/builtins-regexp.cc
+++ b/src/builtins/builtins-regexp.cc
@@ -82,7 +82,7 @@ DEFINE_CAPTURE_GETTER(9)
 BUILTIN(RegExpInputGetter) {
   HandleScope scope(isolate);
   Handle<Object> obj(isolate->regexp_last_match_info()->LastInput(), isolate);
-  return obj->IsUndefined(isolate) ? isolate->heap()->empty_string()
+  return obj->IsUndefined(isolate) ? ReadOnlyRoots(isolate).empty_string()
                                    : String::cast(*obj);
 }
 
@@ -93,7 +93,7 @@ BUILTIN(RegExpInputSetter) {
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, str,
                                      Object::ToString(isolate, value));
   isolate->regexp_last_match_info()->SetLastInput(*str);
-  return isolate->heap()->undefined_value();
+  return ReadOnlyRoots(isolate).undefined_value();
 }
 
 // Getters for the static properties lastMatch, lastParen, leftContext, and
@@ -110,7 +110,9 @@ BUILTIN(RegExpLastParenGetter) {
   HandleScope scope(isolate);
   Handle<RegExpMatchInfo> match_info = isolate->regexp_last_match_info();
   const int length = match_info->NumberOfCaptureRegisters();
-  if (length <= 2) return isolate->heap()->empty_string();  // No captures.
+  if (length <= 2) {
+    return ReadOnlyRoots(isolate).empty_string();  // No captures.
+  }
 
   DCHECK_EQ(0, length % 2);
   const int last_capture = (length / 2) - 1;
diff --git a/src/builtins/builtins-sharedarraybuffer.cc b/src/builtins/builtins-sharedarraybuffer.cc
index a847a5d892..a1b36c5fb6 100644
--- a/src/builtins/builtins-sharedarraybuffer.cc
+++ b/src/builtins/builtins-sharedarraybuffer.cc
@@ -93,7 +93,7 @@ BUILTIN(AtomicsWake) {
       isolate, sta, ValidateSharedIntegerTypedArray(isolate, array, true));
 
   Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
-  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  if (maybe_index.IsNothing()) return ReadOnlyRoots(isolate).exception();
   size_t i = maybe_index.FromJust();
 
   uint32_t c;
@@ -130,7 +130,7 @@ BUILTIN(AtomicsWait) {
       isolate, sta, ValidateSharedIntegerTypedArray(isolate, array, true));
 
   Maybe<size_t> maybe_index = ValidateAtomicAccess(isolate, sta, index);
-  if (maybe_index.IsNothing()) return isolate->heap()->exception();
+  if (maybe_index.IsNothing()) return ReadOnlyRoots(isolate).exception();
   size_t i = maybe_index.FromJust();
 
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, value,
@@ -139,13 +139,13 @@ BUILTIN(AtomicsWait) {
 
   double timeout_number;
   if (timeout->IsUndefined(isolate)) {
-    timeout_number = isolate->heap()->infinity_value()->Number();
+    timeout_number = ReadOnlyRoots(isolate).infinity_value()->Number();
   } else {
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, timeout,
                                        Object::ToNumber(timeout));
     timeout_number = timeout->Number();
     if (std::isnan(timeout_number))
-      timeout_number = isolate->heap()->infinity_value()->Number();
+      timeout_number = ReadOnlyRoots(isolate).infinity_value()->Number();
     else if (timeout_number < 0)
       timeout_number = 0;
   }
diff --git a/src/builtins/builtins-string.cc b/src/builtins/builtins-string.cc
index af5f786175..b9f802e3f1 100644
--- a/src/builtins/builtins-string.cc
+++ b/src/builtins/builtins-string.cc
@@ -52,7 +52,7 @@ uc32 NextCodePoint(Isolate* isolate, BuiltinArguments args, int index) {
 BUILTIN(StringFromCodePoint) {
   HandleScope scope(isolate);
   int const length = args.length() - 1;
-  if (length == 0) return isolate->heap()->empty_string();
+  if (length == 0) return ReadOnlyRoots(isolate).empty_string();
   DCHECK_LT(0, length);
 
   // Optimistically assume that the resulting String contains only one byte
@@ -64,7 +64,7 @@ BUILTIN(StringFromCodePoint) {
   for (index = 0; index < length; index++) {
     code = NextCodePoint(isolate, args, index);
     if (code < 0) {
-      return isolate->heap()->exception();
+      return ReadOnlyRoots(isolate).exception();
     }
     if (code > String::kMaxOneByteCharCode) {
       break;
@@ -94,7 +94,7 @@ BUILTIN(StringFromCodePoint) {
     }
     code = NextCodePoint(isolate, args, index);
     if (code < 0) {
-      return isolate->heap()->exception();
+      return ReadOnlyRoots(isolate).exception();
     }
   }
 
@@ -122,7 +122,7 @@ BUILTIN(StringPrototypeEndsWith) {
   Maybe<bool> is_reg_exp = RegExpUtils::IsRegExp(isolate, search);
   if (is_reg_exp.IsNothing()) {
     DCHECK(isolate->has_pending_exception());
-    return isolate->heap()->exception();
+    return ReadOnlyRoots(isolate).exception();
   }
   if (is_reg_exp.FromJust()) {
     THROW_NEW_ERROR_RETURN_FAILURE(
@@ -146,7 +146,7 @@ BUILTIN(StringPrototypeEndsWith) {
   }
 
   int start = end - search_string->length();
-  if (start < 0) return isolate->heap()->false_value();
+  if (start < 0) return ReadOnlyRoots(isolate).false_value();
 
   str = String::Flatten(isolate, str);
   search_string = String::Flatten(isolate, search_string);
@@ -169,10 +169,10 @@ BUILTIN(StringPrototypeEndsWith) {
 
   for (int i = 0; i < search_string->length(); i++) {
     if (str_reader.Get(start + i) != search_reader.Get(i)) {
-      return isolate->heap()->false_value();
+      return ReadOnlyRoots(isolate).false_value();
     }
   }
-  return isolate->heap()->true_value();
+  return ReadOnlyRoots(isolate).true_value();
 }
 
 // ES6 section 21.1.3.9
@@ -280,7 +280,7 @@ BUILTIN(StringPrototypeStartsWith) {
   Maybe<bool> is_reg_exp = RegExpUtils::IsRegExp(isolate, search);
   if (is_reg_exp.IsNothing()) {
     DCHECK(isolate->has_pending_exception());
-    return isolate->heap()->exception();
+    return ReadOnlyRoots(isolate).exception();
   }
   if (is_reg_exp.FromJust()) {
     THROW_NEW_ERROR_RETURN_FAILURE(
@@ -304,7 +304,7 @@ BUILTIN(StringPrototypeStartsWith) {
   }
 
   if (start + search_string->length() > str->length()) {
-    return isolate->heap()->false_value();
+    return ReadOnlyRoots(isolate).false_value();
   }
 
   FlatStringReader str_reader(isolate, String::Flatten(isolate, str));
@@ -313,10 +313,10 @@ BUILTIN(StringPrototypeStartsWith) {
 
   for (int i = 0; i < search_string->length(); i++) {
     if (str_reader.Get(start + i) != search_reader.Get(i)) {
-      return isolate->heap()->false_value();
+      return ReadOnlyRoots(isolate).false_value();
     }
   }
-  return isolate->heap()->true_value();
+  return ReadOnlyRoots(isolate).true_value();
 }
 
 #ifndef V8_INTL_SUPPORT
diff --git a/src/builtins/builtins-symbol.cc b/src/builtins/builtins-symbol.cc
index 1343a293bd..9ebb8c499d 100644
--- a/src/builtins/builtins-symbol.cc
+++ b/src/builtins/builtins-symbol.cc
@@ -57,7 +57,7 @@ BUILTIN(SymbolKeyFor) {
     result = symbol->name();
     DCHECK(result->IsString());
   } else {
-    result = isolate->heap()->undefined_value();
+    result = ReadOnlyRoots(isolate).undefined_value();
   }
   DCHECK_EQ(isolate->heap()->public_symbol_table()->SlowReverseLookup(*symbol),
             result);
diff --git a/src/builtins/builtins-typed-array.cc b/src/builtins/builtins-typed-array.cc
index 13404aa4c1..4ca09988fc 100644
--- a/src/builtins/builtins-typed-array.cc
+++ b/src/builtins/builtins-typed-array.cc
@@ -170,10 +170,10 @@ BUILTIN(TypedArrayPrototypeIncludes) {
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, array, JSTypedArray::Validate(isolate, args.receiver(), method));
 
-  if (args.length() < 2) return isolate->heap()->false_value();
+  if (args.length() < 2) return ReadOnlyRoots(isolate).false_value();
 
   int64_t len = array->length_value();
-  if (len == 0) return isolate->heap()->false_value();
+  if (len == 0) return ReadOnlyRoots(isolate).false_value();
 
   int64_t index = 0;
   if (args.length() > 2) {
@@ -184,14 +184,15 @@ BUILTIN(TypedArrayPrototypeIncludes) {
   }
 
   // TODO(cwhan.tunz): throw. See the above comment in CopyWithin.
-  if (V8_UNLIKELY(array->WasNeutered())) return isolate->heap()->false_value();
+  if (V8_UNLIKELY(array->WasNeutered()))
+    return ReadOnlyRoots(isolate).false_value();
 
   Handle<Object> search_element = args.atOrUndefined(isolate, 1);
   ElementsAccessor* elements = array->GetElementsAccessor();
   Maybe<bool> result = elements->IncludesValue(isolate, array, search_element,
                                                static_cast<uint32_t>(index),
                                                static_cast<uint32_t>(len));
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return *isolate->factory()->ToBoolean(result.FromJust());
 }
 
@@ -222,7 +223,7 @@ BUILTIN(TypedArrayPrototypeIndexOf) {
   Maybe<int64_t> result = elements->IndexOfValue(isolate, array, search_element,
                                                  static_cast<uint32_t>(index),
                                                  static_cast<uint32_t>(len));
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return *isolate->factory()->NewNumberFromInt64(result.FromJust());
 }
 
@@ -256,7 +257,7 @@ BUILTIN(TypedArrayPrototypeLastIndexOf) {
   ElementsAccessor* elements = array->GetElementsAccessor();
   Maybe<int64_t> result = elements->LastIndexOfValue(
       isolate, array, search_element, static_cast<uint32_t>(index));
-  MAYBE_RETURN(result, isolate->heap()->exception());
+  MAYBE_RETURN(result, ReadOnlyRoots(isolate).exception());
   return *isolate->factory()->NewNumberFromInt64(result.FromJust());
 }
 
diff --git a/src/builtins/constants-table-builder.cc b/src/builtins/constants-table-builder.cc
index 492fdc94ed..6dd390c795 100644
--- a/src/builtins/constants-table-builder.cc
+++ b/src/builtins/constants-table-builder.cc
@@ -12,7 +12,7 @@ namespace internal {
 BuiltinsConstantsTableBuilder::BuiltinsConstantsTableBuilder(Isolate* isolate)
     : isolate_(isolate), map_(isolate->heap()) {
   // Ensure this is only called once per Isolate.
-  DCHECK_EQ(isolate_->heap()->empty_fixed_array(),
+  DCHECK_EQ(ReadOnlyRoots(isolate_).empty_fixed_array(),
             isolate_->heap()->builtins_constants_table());
 
   // And that the initial value of the builtins constants table can be treated
@@ -30,7 +30,7 @@ uint32_t BuiltinsConstantsTableBuilder::AddObject(Handle<Object> object) {
   DCHECK(!isolate_->heap()->IsRootHandle(object, &root_list_index));
 
   // Not yet finalized.
-  DCHECK_EQ(isolate_->heap()->empty_fixed_array(),
+  DCHECK_EQ(ReadOnlyRoots(isolate_).empty_fixed_array(),
             isolate_->heap()->builtins_constants_table());
 
   // Must be on the main thread.
@@ -60,7 +60,7 @@ void BuiltinsConstantsTableBuilder::PatchSelfReference(
   DCHECK(!isolate_->heap()->IsRootHandle(code_object, &root_list_index));
 
   // Not yet finalized.
-  DCHECK_EQ(isolate_->heap()->empty_fixed_array(),
+  DCHECK_EQ(ReadOnlyRoots(isolate_).empty_fixed_array(),
             isolate_->heap()->builtins_constants_table());
 
   DCHECK(isolate_->serializer_enabled());
@@ -72,7 +72,7 @@ void BuiltinsConstantsTableBuilder::PatchSelfReference(
   // During indirection generation, we always create a distinct marker for each
   // macro assembler. The canonical marker is only used when not generating a
   // snapshot.
-  DCHECK(*self_reference != isolate_->heap()->self_reference_marker());
+  DCHECK(*self_reference != ReadOnlyRoots(isolate_).self_reference_marker());
 #endif
 
   uint32_t key;
@@ -85,7 +85,7 @@ void BuiltinsConstantsTableBuilder::PatchSelfReference(
 void BuiltinsConstantsTableBuilder::Finalize() {
   HandleScope handle_scope(isolate_);
 
-  DCHECK_EQ(isolate_->heap()->empty_fixed_array(),
+  DCHECK_EQ(ReadOnlyRoots(isolate_).empty_fixed_array(),
             isolate_->heap()->builtins_constants_table());
   DCHECK(isolate_->serializer_enabled());
 
@@ -112,8 +112,8 @@ void BuiltinsConstantsTableBuilder::Finalize() {
 #ifdef DEBUG
   for (int i = 0; i < map_.size(); i++) {
     DCHECK(table->get(i)->IsHeapObject());
-    DCHECK_NE(isolate_->heap()->undefined_value(), table->get(i));
-    DCHECK_NE(isolate_->heap()->self_reference_marker(), table->get(i));
+    DCHECK_NE(ReadOnlyRoots(isolate_).undefined_value(), table->get(i));
+    DCHECK_NE(ReadOnlyRoots(isolate_).self_reference_marker(), table->get(i));
   }
 #endif