Unit test to document the pretenuring behavior of nested literals

Change-Id: I02710e807fa2cd36849b4ab9d76cde2e99f02911
Reviewed-on: https://chromium-review.googlesource.com/1107983
Commit-Queue: Chandan Reddy <chandanreddy@google.com>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53910}

test/cctest/heap/test-heap.cc

@@ -2374,6 +2374,49 @@ TEST(OptimizedPretenuringObjectArrayLiterals) {
   CHECK(CcTest::heap()->InOldSpace(*o));
 }
 
+TEST(OptimizedPretenuringNestedInObjectProperties) {
+  FLAG_allow_natives_syntax = true;
+  FLAG_expose_gc = true;
+  CcTest::InitializeVM();
+  if (!CcTest::i_isolate()->use_optimizer() || FLAG_always_opt) return;
+  if (FLAG_gc_global || FLAG_stress_compaction ||
+      FLAG_stress_incremental_marking) {
+    return;
+  }
+  v8::HandleScope scope(CcTest::isolate());
+
+  // Grow new space until maximum capacity reached.
+  while (!CcTest::heap()->new_space()->IsAtMaximumCapacity()) {
+    CcTest::heap()->new_space()->Grow();
+  }
+
+  // Keep the nested literal alive while its root is freed
+  i::ScopedVector<char> source(1024);
+  i::SNPrintF(source,
+              "let number_elements = %d;"
+              "let elements = new Array(number_elements);"
+              "function f() {"
+              "  for (let i = 0; i < number_elements; i++) {"
+              "     let l =  {a: {c: 2.2, d: {e: 3.3}}, b: 1.1}; "
+              "    elements[i] = l.a;"
+              "  }"
+              "  return elements[number_elements-1];"
+              "};"
+              "f(); gc(); gc();"
+              "f(); f();"
+              "%%OptimizeFunctionOnNextCall(f);"
+              "f();",
+              kPretenureCreationCount);
+
+  v8::Local<v8::Value> res = CompileRun(source.start());
+
+  i::Handle<JSObject> o = Handle<JSObject>::cast(
+      v8::Utils::OpenHandle(*v8::Local<v8::Object>::Cast(res)));
+
+  // Nested literal sites are only pretenured if the top level
+  // literal is pretenured
+  CHECK(CcTest::heap()->InNewSpace(*o));
+}
 
 TEST(OptimizedPretenuringMixedInObjectProperties) {
   FLAG_allow_natives_syntax = true;