[literals] Reuse InitializeAllocationMemento in FastCloneShallowObject

- Update InitializeAllocationMemento to use newer CSA helper
- Fix AllocateJSArray to create AllocationMementos for empty arrays as well

Bug: v8:6211
Change-Id: I8731b04cdd500b877a54dee67f00f2899d91d86d
Reviewed-on: https://chromium-review.googlesource.com/566810
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46594}

src/builtins/builtins-constructor-gen.cc

@@ -619,7 +619,8 @@ Node* ConstructorBuiltinsAssembler::EmitFastCloneShallowObject(
   STATIC_ASSERT(JSObject::kMaxInstanceSize < kMaxRegularHeapObjectSize);
   Node* instance_size = TimesPointerSize(LoadMapInstanceSize(boilerplate_map));
   Node* allocation_size = instance_size;
-  if (FLAG_allocation_site_pretenuring) {
+  bool needs_allocation_memento = FLAG_allocation_site_pretenuring;
+  if (needs_allocation_memento) {
     // Prepare for inner-allocating the AllocationMemento.
     allocation_size =
         IntPtrAdd(instance_size, IntPtrConstant(AllocationMemento::kSize));
@@ -638,18 +639,8 @@ Node* ConstructorBuiltinsAssembler::EmitFastCloneShallowObject(
 
   // Initialize the AllocationMemento before potential GCs due to heap number
   // allocation when copying the in-object properties.
-  if (FLAG_allocation_site_pretenuring) {
-    Comment("Initialize AllocationMemento");
-    Node* memento = InnerAllocate(copy, instance_size);
-    StoreMapNoWriteBarrier(memento, Heap::kAllocationMementoMapRootIndex);
-    StoreObjectFieldNoWriteBarrier(
-        memento, AllocationMemento::kAllocationSiteOffset, allocation_site);
-    Node* memento_create_count = LoadObjectField(
-        allocation_site, AllocationSite::kPretenureCreateCountOffset);
-    memento_create_count = SmiAdd(memento_create_count, SmiConstant(1));
-    StoreObjectFieldNoWriteBarrier(allocation_site,
-                                   AllocationSite::kPretenureCreateCountOffset,
-                                   memento_create_count);
+  if (needs_allocation_memento) {
+    InitializeAllocationMemento(copy, instance_size, allocation_site);
   }
 
   {

src/code-stub-assembler.cc

@@ -2284,7 +2284,8 @@ Node* CodeStubAssembler::AllocateUninitializedJSArray(ElementsKind kind,
                        Heap::kEmptyFixedArrayRootIndex);
 
   if (allocation_site != nullptr) {
-    InitializeAllocationMemento(array, JSArray::kSize, allocation_site);
+    InitializeAllocationMemento(array, IntPtrConstant(JSArray::kSize),
+                                allocation_site);
   }
   return array;
 }
@@ -2302,7 +2303,7 @@ Node* CodeStubAssembler::AllocateJSArray(ElementsKind kind, Node* array_map,
     // Array is empty. Use the shared empty fixed array instead of allocating a
     // new one.
     array = AllocateUninitializedJSArrayWithoutElements(kind, array_map, length,
-                                                        nullptr);
+                                                        allocation_site);
     StoreObjectFieldRoot(array, JSArray::kElementsOffset,
                          Heap::kEmptyFixedArrayRootIndex);
   } else {
@@ -2769,16 +2770,14 @@ Node* CodeStubAssembler::GrowElementsCapacity(
   return new_elements;
 }
 
-void CodeStubAssembler::InitializeAllocationMemento(Node* base_allocation,
-                                                    int base_allocation_size,
+void CodeStubAssembler::InitializeAllocationMemento(Node* base,
+                                                    Node* base_allocation_size,
                                                     Node* allocation_site) {
+  Comment("[Initialize AllocationMemento");
+  Node* memento = InnerAllocate(base, base_allocation_size);
+  StoreMapNoWriteBarrier(memento, Heap::kAllocationMementoMapRootIndex);
   StoreObjectFieldNoWriteBarrier(
-      base_allocation, AllocationMemento::kMapOffset + base_allocation_size,
-      HeapConstant(Handle<Map>(isolate()->heap()->allocation_memento_map())));
-  StoreObjectFieldNoWriteBarrier(
-      base_allocation,
-      AllocationMemento::kAllocationSiteOffset + base_allocation_size,
-      allocation_site);
+      memento, AllocationMemento::kAllocationSiteOffset, allocation_site);
   if (FLAG_allocation_site_pretenuring) {
     Node* count = LoadObjectField(allocation_site,
                                   AllocationSite::kPretenureCreateCountOffset);
@@ -2787,6 +2786,7 @@ void CodeStubAssembler::InitializeAllocationMemento(Node* base_allocation,
                                    AllocationSite::kPretenureCreateCountOffset,
                                    incremented_count);
   }
+  Comment("]");
 }
 
 Node* CodeStubAssembler::TryTaggedToFloat64(Node* value,

src/code-stub-assembler.h

@@ -742,7 +742,7 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
 
   // Allocation site manipulation
   void InitializeAllocationMemento(Node* base_allocation,
-                                   int base_allocation_size,
+                                   Node* base_allocation_size,
                                    Node* allocation_site);
 
   Node* TryTaggedToFloat64(Node* value, Label* if_valueisnotnumber);