[web snapshot] Support oddballs

This CL adds support for oddballs false, true, null and undefined.

Bug: v8:11525, v8:11706
Change-Id: I0dc870f05578c0eb9ff06bf2ccd2474e18464566
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2856843
Commit-Queue: Vicky Kontoura <vkont@google.com>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74304}

src/web-snapshot/web-snapshot.cc

@@ -398,8 +398,22 @@ void WebSnapshotSerializer::WriteValue(Handle<Object> object,
   DCHECK(object->IsHeapObject());
   switch (HeapObject::cast(*object).map().instance_type()) {
     case ODDBALL_TYPE:
-      // TODO(v8:11525): Implement.
-      UNREACHABLE();
+      switch (Oddball::cast(*object).kind()) {
+        case Oddball::kFalse:
+          serializer.WriteUint32(ValueType::FALSE_CONSTANT);
+          return;
+        case Oddball::kTrue:
+          serializer.WriteUint32(ValueType::TRUE_CONSTANT);
+          return;
+        case Oddball::kNull:
+          serializer.WriteUint32(ValueType::NULL_CONSTANT);
+          return;
+        case Oddball::kUndefined:
+          serializer.WriteUint32(ValueType::UNDEFINED_CONSTANT);
+          return;
+        default:
+          UNREACHABLE();
+      }
     case HEAP_NUMBER_TYPE:
       // TODO(v8:11525): Handle possible endianness mismatch.
       serializer.WriteUint32(ValueType::DOUBLE);
@@ -846,6 +860,26 @@ void WebSnapshotDeserializer::ReadValue(Handle<Object>& value,
     return;
   }
   switch (value_type) {
+    case ValueType::FALSE_CONSTANT: {
+      value = handle(ReadOnlyRoots(isolate_).false_value(), isolate_);
+      representation = Representation::Tagged();
+      break;
+    }
+    case ValueType::TRUE_CONSTANT: {
+      value = handle(ReadOnlyRoots(isolate_).true_value(), isolate_);
+      representation = Representation::Tagged();
+      break;
+    }
+    case ValueType::NULL_CONSTANT: {
+      value = handle(ReadOnlyRoots(isolate_).null_value(), isolate_);
+      representation = Representation::Tagged();
+      break;
+    }
+    case ValueType::UNDEFINED_CONSTANT: {
+      value = handle(ReadOnlyRoots(isolate_).undefined_value(), isolate_);
+      representation = Representation::Tagged();
+      break;
+    }
     case ValueType::INTEGER: {
       Maybe<int32_t> number = deserializer_->ReadZigZag<int32_t>();
       if (number.IsNothing()) {

src/web-snapshot/web-snapshot.h

@@ -39,6 +39,10 @@ class WebSnapshotSerializerDeserializer {
   const char* error_message() const { return error_message_; }
 
   enum ValueType : uint8_t {
+    FALSE_CONSTANT,
+    TRUE_CONSTANT,
+    NULL_CONSTANT,
+    UNDEFINED_CONSTANT,
     INTEGER,
     DOUBLE,
     STRING_ID,

test/cctest/test-web-snapshots.cc

@@ -140,6 +140,36 @@ TEST(Numbers) {
                            kObjectCount);
 }
 
+TEST(Oddballs) {
+  const char* snapshot_source =
+      "var foo = {'a': false,\n"
+      "           'b': true,\n"
+      "           'c': null,\n"
+      "           'd': undefined,\n"
+      "}";
+  const char* test_source = "foo";
+  uint32_t kStringCount = 5;  // 'foo', 'a', ..., 'd'
+  uint32_t kMapCount = 1;
+  uint32_t kContextCount = 0;
+  uint32_t kFunctionCount = 0;
+  uint32_t kObjectCount = 1;
+  std::function<void(v8::Isolate*, v8::Local<v8::Context>)> tester =
+      [test_source](v8::Isolate* isolate, v8::Local<v8::Context> new_context) {
+        v8::Local<v8::Object> result = CompileRun(test_source).As<v8::Object>();
+        Local<Value> a = result->Get(new_context, v8_str("a")).ToLocalChecked();
+        CHECK(a->IsFalse());
+        Local<Value> b = result->Get(new_context, v8_str("b")).ToLocalChecked();
+        CHECK(b->IsTrue());
+        Local<Value> c = result->Get(new_context, v8_str("c")).ToLocalChecked();
+        CHECK(c->IsNull());
+        Local<Value> d = result->Get(new_context, v8_str("d")).ToLocalChecked();
+        CHECK(d->IsUndefined());
+      };
+  TestWebSnapshotExtensive(snapshot_source, test_source, tester, kStringCount,
+                           kMapCount, kContextCount, kFunctionCount,
+                           kObjectCount);
+}
+
 TEST(Function) {
   const char* snapshot_source =
       "var foo = {'key': function() { return '11525'; }};";