[stubs] Fix CodeStubAssembler::TrapAllocationMemento

src/code-stub-assembler.cc

 // Copyright 2016 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 "src/code-stub-assembler.h"
 #include "src/code-factory.h"
 #include "src/frames-inl.h"
 #include "src/frames.h"
 #include "src/ic/handler-configuration.h"
 #include "src/ic/stub-cache.h"
 
@@ skipping 6869 matching lines @@
 }
 
 void CodeStubAssembler::TrapAllocationMemento(Node* object,
                                               Label* memento_found) {
   Comment("[ TrapAllocationMemento");
   Label no_memento_found(this);
   Label top_check(this), map_check(this);
 
   Node* new_space_top_address = ExternalConstant(
       ExternalReference::new_space_allocation_top_address(isolate()));
-  const int kMementoMapOffset = JSArray::kSize - kHeapObjectTag;
+  const int kMementoMapOffset = JSArray::kSize;
   const int kMementoLastWordOffset =
       kMementoMapOffset + AllocationMemento::kSize - kPointerSize;
 
   // Bail out if the object is not in new space.
   Node* object_page = PageFromAddress(object);
   {
-    const int mask =
-        (1 << MemoryChunk::IN_FROM_SPACE) | (1 << MemoryChunk::IN_TO_SPACE);
-    Node* page_flags = Load(MachineType::IntPtr(), object_page);
-    GotoIf(
-        WordEqual(WordAnd(page_flags, IntPtrConstant(mask)), IntPtrConstant(0)),
-        &no_memento_found);
+    Node* page_flags = Load(MachineType::IntPtr(), object_page,
+                            IntPtrConstant(Page::kFlagsOffset));
+    GotoIf(WordEqual(WordAnd(page_flags,
+                             IntPtrConstant(MemoryChunk::kIsInNewSpaceMask)),
+                     IntPtrConstant(0)),
+           &no_memento_found);
   }
 
-  Node* memento_last_word =
-      IntPtrAdd(object, IntPtrConstant(kMementoLastWordOffset));
+  Node* memento_last_word = IntPtrAdd(
+      object, IntPtrConstant(kMementoLastWordOffset - kHeapObjectTag));
   Node* memento_last_word_page = PageFromAddress(memento_last_word);
 
   Node* new_space_top = Load(MachineType::Pointer(), new_space_top_address);
   Node* new_space_top_page = PageFromAddress(new_space_top);
 
   // If the object is in new space, we need to check whether respective
   // potential memento object is on the same page as the current top.
   GotoIf(WordEqual(memento_last_word_page, new_space_top_page), &top_check);
 
   // The object is on a different page than allocation top. Bail out if the
@@ skipping 1996 matching lines @@
 }
 
 void CodeStubArguments::PopAndReturn(compiler::Node* value) {
   assembler_->PopAndReturn(
       assembler_->IntPtrAddFoldConstants(argc_, assembler_->IntPtrConstant(1)),
       value);
 }
 
 }  // namespace internal
 }  // namespace v8