[test] Check object literal backing store size.

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

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdlib.h>
 #include <sstream>
 #include <utility>
 
 #include "src/api.h"
 #include "src/objects-inl.h"
@@ skipping 706 matching lines @@
     CHECK(!IsObjectShrinkable(*obj));
 
     // No slack left.
     CHECK_EQ(kMaxInobjectProperties, obj->map()->GetInObjectProperties());
   }
 
   // The other classes in the hierarchy are not affected.
   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.
   FLAG_inline_construct = false;
   FLAG_always_opt = false;
   CcTest::InitializeVM();
   v8::HandleScope scope(CcTest::isolate());
 
   std::vector<int> hierarchy_desc;
   const int kNoOverflowCount = 5;
@@ skipping 365 matching lines @@
 
   TestSubclassBuiltin("A1", JS_PROMISE_TYPE, "Promise",
                       "function(resolve, reject) { resolve('ok'); }");
 }
 
 
 TEST(SubclassPromiseBuiltinNoInlineNew) {
   FLAG_inline_new = false;
   TestSubclassPromiseBuiltin();
 }