Optimize ClearNonLiveReferences: do not compact prototype transitions in GC.

test/cctest/test-heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2602 matching lines @@
     v8::Local<v8::Function> g = v8::Local<v8::Function>::Cast(
         global->Get(ctx, v8_str("g")).ToLocalChecked());
     g->Call(ctx, global, 0, nullptr).ToLocalChecked();
   }
 
   CcTest::heap()->incremental_marking()->set_should_hurry(true);
   CcTest::heap()->CollectGarbage(OLD_SPACE);
 }
 
 
-static int NumberOfProtoTransitions(Map* map) {
-  return TransitionArray::NumberOfPrototypeTransitions(
-      TransitionArray::GetPrototypeTransitions(map));
-}
-
-
 TEST(PrototypeTransitionClearing) {
   if (FLAG_never_compact) return;
   CcTest::InitializeVM();
   Isolate* isolate = CcTest::i_isolate();
   Factory* factory = isolate->factory();
   v8::HandleScope scope(CcTest::isolate());
   v8::Local<v8::Context> ctx = CcTest::isolate()->GetCurrentContext();
 
   CompileRun("var base = {};");
   i::Handle<JSReceiver> baseObject =
       v8::Utils::OpenHandle(*v8::Local<v8::Object>::Cast(
           CcTest::global()->Get(ctx, v8_str("base")).ToLocalChecked()));
 
-  int initialTransitions = NumberOfProtoTransitions(baseObject->map());
+  int initialTransitions =
+      TransitionArray::NumberOfPrototypeTransitionsForTest(baseObject->map());
 
   CompileRun(
       "var live = [];"
       "for (var i = 0; i < 10; i++) {"
       "  var object = {};"
       "  var prototype = {};"
       "  object.__proto__ = prototype;"
       "  if (i >= 3) live.push(object, prototype);"
       "}");
 
   // Verify that only dead prototype transitions are cleared.
-  CHECK_EQ(initialTransitions + 10,
-           NumberOfProtoTransitions(baseObject->map()));
+  CHECK_EQ(
+      initialTransitions + 10,
+      TransitionArray::NumberOfPrototypeTransitionsForTest(baseObject->map()));
   CcTest::heap()->CollectAllGarbage();
   const int transitions = 10 - 3;
-  CHECK_EQ(initialTransitions + transitions,
-           NumberOfProtoTransitions(baseObject->map()));
+  CHECK_EQ(
+      initialTransitions + transitions,
+      TransitionArray::NumberOfPrototypeTransitionsForTest(baseObject->map()));
 
   // Verify that prototype transitions array was compacted.
   FixedArray* trans =
       TransitionArray::GetPrototypeTransitions(baseObject->map());
   for (int i = initialTransitions; i < initialTransitions + transitions; i++) {
     int j = TransitionArray::kProtoTransitionHeaderSize + i;
     CHECK(trans->get(j)->IsWeakCell());
     CHECK(WeakCell::cast(trans->get(j))->value()->IsMap());
   }
 
@@ skipping 3779 matching lines @@
   isolate->IncrementJsCallsFromApiCounter();
   isolate->IncrementJsCallsFromApiCounter();
   isolate->IncrementJsCallsFromApiCounter();
   calls_per_ms = memory_reducer->SampleAndGetJsCallsPerMs(4);
   CheckDoubleEquals(2, calls_per_ms);
 }
 
 
 }  // namespace internal
 }  // namespace v8