Pretenuring decision of outermost literal is propagated to inner literals.

src/hydrogen.cc

 // Copyright 2013 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/hydrogen.h"
 
 #include <sstream>
 
 #include "src/v8.h"
 
@@ skipping 11411 matching lines @@
   NoObservableSideEffectsScope no_effects(this);
   Handle<Map> initial_map(boilerplate_object->map());
   InstanceType instance_type = initial_map->instance_type();
   DCHECK(instance_type == JS_ARRAY_TYPE || instance_type == JS_OBJECT_TYPE);
 
   HType type = instance_type == JS_ARRAY_TYPE
       ? HType::JSArray() : HType::JSObject();
   HValue* object_size_constant = Add<HConstant>(initial_map->instance_size());
 
   PretenureFlag pretenure_flag = NOT_TENURED;
-  Handle<AllocationSite> current_site(*site_context->current(), isolate());
+  Handle<AllocationSite> top_site(*site_context->top(), isolate());
   if (FLAG_allocation_site_pretenuring) {
-    pretenure_flag = current_site->GetPretenureMode();
-    top_info()->dependencies()->AssumeTenuringDecision(current_site);
+    pretenure_flag = top_site->GetPretenureMode();
   }
 
+  Handle<AllocationSite> current_site(*site_context->current(), isolate());
+  if (*top_site == *current_site) {
+    // We install a dependency for pretenuring only on the outermost literal.
+    top_info()->dependencies()->AssumeTenuringDecision(top_site);
+  }
   top_info()->dependencies()->AssumeTransitionStable(current_site);
 
   HInstruction* object = Add<HAllocate>(
-      object_size_constant, type, pretenure_flag, instance_type, current_site);
+      object_size_constant, type, pretenure_flag, instance_type, top_site);
 
   // If allocation folding reaches Page::kMaxRegularHeapObjectSize the
   // elements array may not get folded into the object. Hence, we set the
   // elements pointer to empty fixed array and let store elimination remove
   // this store in the folding case.
   HConstant* empty_fixed_array = Add<HConstant>(
       isolate()->factory()->empty_fixed_array());
   Add<HStoreNamedField>(object, HObjectAccess::ForElementsPointer(),
       empty_fixed_array);
 
@@ skipping 19 matching lines @@
         isolate()->factory()->CopyAndTenureFixedCOWArray(
             Handle<FixedArray>::cast(elements)));
     boilerplate_object->set_elements(*elements);
   }
 
   HInstruction* object_elements = NULL;
   if (elements_size > 0) {
     HValue* object_elements_size = Add<HConstant>(elements_size);
     InstanceType instance_type = boilerplate_object->HasFastDoubleElements()
         ? FIXED_DOUBLE_ARRAY_TYPE : FIXED_ARRAY_TYPE;
-    object_elements =
-        Add<HAllocate>(object_elements_size, HType::HeapObject(),
-                       pretenure_flag, instance_type, current_site);
+    object_elements = Add<HAllocate>(object_elements_size, HType::HeapObject(),
+                                     pretenure_flag, instance_type, top_site);
     BuildEmitElements(boilerplate_object, elements, object_elements,
                       site_context);
     Add<HStoreNamedField>(object, HObjectAccess::ForElementsPointer(),
                           object_elements);
   } else {
     Handle<Object> elements_field =
         Handle<Object>(boilerplate_object->elements(), isolate());
     HInstruction* object_elements_cow = Add<HConstant>(elements_field);
     Add<HStoreNamedField>(object, HObjectAccess::ForElementsPointer(),
                           object_elements_cow);
@@ skipping 80 matching lines @@
           BuildFastLiteral(value_object, site_context);
       site_context->ExitScope(current_site, value_object);
       Add<HStoreNamedField>(object, access, result);
     } else {
       Representation representation = details.representation();
       HInstruction* value_instruction;
 
       if (representation.IsDouble()) {
         // Allocate a HeapNumber box and store the value into it.
         HValue* heap_number_constant = Add<HConstant>(HeapNumber::kSize);
-        // This heap number alloc does not have a corresponding
-        // AllocationSite. That is okay because
-        // 1) it's a child object of another object with a valid allocation site
-        // 2) we can just use the mode of the parent object for pretenuring
         HInstruction* double_box =
             Add<HAllocate>(heap_number_constant, HType::HeapObject(),
                 pretenure_flag, MUTABLE_HEAP_NUMBER_TYPE);
         AddStoreMapConstant(double_box,
             isolate()->factory()->mutable_heap_number_map());
         // Unwrap the mutable heap number from the boilerplate.
         HValue* double_value =
             Add<HConstant>(Handle<HeapNumber>::cast(value)->value());
         Add<HStoreNamedField>(
             double_box, HObjectAccess::ForHeapNumberValue(), double_value);
@@ skipping 1723 matching lines @@
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 }  // namespace internal
 }  // namespace v8