[test] Check object literal backing store size.

test/cctest/test-inobject-slack-tracking.cc

Index: test/cctest/test-inobject-slack-tracking.cc
diff --git a/test/cctest/test-inobject-slack-tracking.cc b/test/cctest/test-inobject-slack-tracking.cc
index 3c46fbee065cd08f1431aff7a9867c9aef9cc4a0..23e12e7249e513456827b516670fd4e44c8fbc75 100644
--- a/test/cctest/test-inobject-slack-tracking.cc
+++ b/test/cctest/test-inobject-slack-tracking.cc
@@ -724,6 +724,112 @@ TEST(InobjectPropetiesCountOverflowInSubclass) {
   TestClassHierarchy(hierarchy_desc, kNoOverflowCount);
 }
 
+static void CheckExpectedProperties(int expected, std::ostringstream& os) {
+  Handle<HeapObject> obj = Handle<HeapObject>::cast(
+      v8::Utils::OpenHandle(*CompileRun(os.str().c_str())));
+  CHECK_EQ(expected, obj->map()->GetInObjectProperties());
+}
+
+TEST(ObjectLiteralPropertyBackingStoreSize) {
+  v8::HandleScope scope(CcTest::isolate());
+  LocalContext env;
+
+  std::ostringstream os;
+
+  // An index key does not require space in the property backing store.
+  os << "(function() {\n"
+        "  function f() {\n"
+        "    var o = {\n"
+        "      '-1': 42,\n"  // Allocate for non-index key.
+        "      1: 42,\n"     // Do not allocate for index key.
+        "      '2': 42\n"    // Do not allocate for index key.
+        "    };\n"
+        "    return o;\n"
+        "  }\n"
+        "\n"
+        "  return f();\n"
+        "} )();";
+  CheckExpectedProperties(1, os);
+
+  // Avoid over-/under-allocation for computed property names.
+  os << "(function() {\n"
+        "  function f(x) {\n"
+        "    var o = {\n"
+        "      1: 42,\n"    // Do not allocate for index key.
+        "      '2': 42,\n"  // Do not allocate for index key.
+        "      [x]: 42,\n"  // Allocate for property with computed name.
+        "      3: 42\n"     // Allocate for index key because we have seen a
+        // computed property.
+        "    };\n"
+        "    return o;\n"
+        "  }\n"
+        "\n"
+        "  var x = 'hello'\n"
+        "\n"
+        "  return f(x);\n"
+        "} )();";
+  CheckExpectedProperties(2, os);
+
+  os << "(function() {\n"
+        "  function f() {\n"
+        "    var o = {};\n"
+        "    return o;\n"
+        "  }\n"
+        "\n"
+        "  return f();\n"
+        "} )();";
+  // Empty objects have slack for 4 properties.
+  CheckExpectedProperties(4, os);
+
+  os << "(function() {\n"
+        "  function f(x) {\n"
+        "    var o = {\n"
+        "      a: 42,\n"    // Allocate for constant property.
+        "      [x]: 42,\n"  // Allocate for property with computed name.
+        "      b: 42\n"     // Allocate for constant property.
+        "    };\n"
+        "    return o;\n"
+        "  }\n"
+        "\n"
+        "  var x = 'hello'\n"
+        "\n"
+        "  return f(x);\n"
+        "} )();";
+  CheckExpectedProperties(3, os);
+
+  os << "(function() {\n"
+        "  function f(x) {\n"
+        "    var o = {\n"
+        "      a: 42,\n"          // Allocate for constant property.
+        "      __proto__: 42,\n"  // Do not allocate for __proto__.
+        "      [x]: 42\n"         // Allocate for property with computed name.
+        "    };\n"
+        "    return o;\n"
+        "  }\n"
+        "\n"
+        "  var x = 'hello'\n"
+        "\n"
+        "  return f(x);\n"
+        "} )();";
+  // __proto__ is not allocated in the backing store.
+  CheckExpectedProperties(2, os);
+
+  os << "(function() {\n"
+        "  function f(x) {\n"
+        "    var o = {\n"
+        "      a: 42,\n"         // Allocate for constant property.
+        "      [x]: 42,\n"       // Allocate for property with computed name.
+        "      __proto__: 42\n"  // Do not allocate for __proto__.
+        "    };\n"
+        "    return o;\n"
+        "  }\n"
+        "\n"
+        "  var x = 'hello'\n"
+        "\n"
+        "  return f(x);\n"
+        "} )();";
+  CheckExpectedProperties(2, os);
+}
 
 TEST(SlowModeSubclass) {
   // Avoid eventual completion of in-object slack tracking.