[string] Add tests for uncached strings with cacheable resources

Add tests for internal external uncached strings with cacheable
resources, for the cached_data functionality added in
https://chromium-review.googlesource.com/c/v8/v8/+/2710440.

Bug: v8:7790, v8:11463
Change-Id: I679c50995d315cc4289452a00838b3cafa4c93e4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2715187Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73103}

test/cctest/test-strings.cc

@@ -2096,6 +2096,84 @@ TEST(InternalizeExternalStringUncachedWithCopyTwoByte) {
   CHECK(internal->IsInternalizedString());
 }
 
+// Show that we cache the data pointer for internal, external and uncached
+// strings with cacheable resources through MakeExternal. One byte version.
+TEST(CheckCachedDataInternalExternalUncachedString) {
+  CcTest::InitializeVM();
+  Factory* factory = CcTest::i_isolate()->factory();
+  v8::HandleScope scope(CcTest::isolate());
+
+  // Due to different size restrictions the string needs to be small but not too
+  // small. One of these restrictions is whether pointer compression is enabled.
+#ifdef V8_COMPRESS_POINTERS
+  const char* raw_small = "small string";
+#elif V8_TARGET_ARCH_32_BIT
+  const char* raw_small = "smol";
+#else
+  const char* raw_small = "smalls";
+#endif  // V8_COMPRESS_POINTERS
+
+  Handle<String> string =
+      factory->InternalizeString(factory->NewStringFromAsciiChecked(raw_small));
+  OneByteResource* resource =
+      new OneByteResource(i::StrDup(raw_small), strlen(raw_small));
+
+  // Check it is external, internalized, and uncached with a cacheable resource.
+  string->MakeExternal(resource);
+  CHECK(string->IsOneByteRepresentation());
+  CHECK(string->IsExternalString());
+  CHECK(string->IsInternalizedString());
+
+  // Check that the external string is uncached, its resource is cacheable, and
+  // that we indeed cached it.
+  Handle<ExternalOneByteString> external_string =
+      Handle<ExternalOneByteString>::cast(string);
+  CHECK(external_string->is_uncached());
+  CHECK(external_string->resource()->IsCacheable());
+  CHECK_NOT_NULL(external_string->resource()->cached_data());
+  CHECK_EQ(external_string->resource()->cached_data(),
+           external_string->resource()->data());
+}
+
+// Show that we cache the data pointer for internal, external and uncached
+// strings with cacheable resources through MakeExternal. One byte version.
+TEST(CheckCachedDataInternalExternalUncachedStringTwoByte) {
+  CcTest::InitializeVM();
+  Factory* factory = CcTest::i_isolate()->factory();
+  v8::HandleScope scope(CcTest::isolate());
+
+  // Due to different size restrictions the string needs to be small but not too
+  // small. One of these restrictions is whether pointer compression is enabled.
+#ifdef V8_COMPRESS_POINTERS
+  const char* raw_small = "small string";
+#elif V8_TARGET_ARCH_32_BIT
+  const char* raw_small = "smol";
+#else
+  const char* raw_small = "smalls";
+#endif  // V8_COMPRESS_POINTERS
+
+  Handle<String> string =
+      factory->InternalizeString(factory->NewStringFromAsciiChecked(raw_small));
+  Resource* resource =
+      new Resource(AsciiToTwoByteString(raw_small), strlen(raw_small));
+
+  // Check it is external, internalized, and uncached with a cacheable resource.
+  string->MakeExternal(resource);
+  CHECK(string->IsTwoByteRepresentation());
+  CHECK(string->IsExternalString());
+  CHECK(string->IsInternalizedString());
+
+  // Check that the external string is uncached, its resource is cacheable, and
+  // that we indeed cached it.
+  Handle<ExternalTwoByteString> external_string =
+      Handle<ExternalTwoByteString>::cast(string);
+  CHECK(external_string->is_uncached());
+  CHECK(external_string->resource()->IsCacheable());
+  CHECK_NOT_NULL(external_string->resource()->cached_data());
+  CHECK_EQ(external_string->resource()->cached_data(),
+           external_string->resource()->data());
+}
+
 }  // namespace test_strings
 }  // namespace internal
 }  // namespace v8