[turbofan] Propagate tenuring decisions to child object allocations.

src/compiler/memory-optimizer.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/compiler/memory-optimizer.h"
 
 #include "src/compiler/js-graph.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
@@ skipping 91 matching lines @@
 }
 
 void MemoryOptimizer::VisitAllocate(Node* node, AllocationState const* state) {
   DCHECK_EQ(IrOpcode::kAllocate, node->opcode());
   Node* value;
   Node* size = node->InputAt(0);
   Node* effect = node->InputAt(1);
   Node* control = node->InputAt(2);
   PretenureFlag pretenure = OpParameter<PretenureFlag>(node->op());
 
+  // Propagate tenuring from outer allocations to inner allocations, i.e.
+  // when we allocate an object in old space and store a newly allocated
+  // child object into the pretenured object, then the newly allocated
+  // child object also should get pretenured to old space.
+  if (pretenure == TENURED) {
+    for (Edge const edge : node->use_edges()) {
+      Node* const user = edge.from();
+      if (user->opcode() == IrOpcode::kStoreField && edge.index() == 0) {
+        Node* const child = user->InputAt(1);
+        if (child->opcode() == IrOpcode::kAllocate &&
+            OpParameter<PretenureFlag>(child) == NOT_TENURED) {

[Jarin, 2016/09/20 09:40:28]

Can we have PretenureFlagOf, please?

[Benedikt Meurer, 2016/09/20 09:42:55]

Follow-up CL.

+          NodeProperties::ChangeOp(child, node->op());
+          break;
+        }
+      }
+    }
+  } else {
+    DCHECK_EQ(NOT_TENURED, pretenure);
+    for (Edge const edge : node->use_edges()) {
+      Node* const user = edge.from();
+      if (user->opcode() == IrOpcode::kStoreField && edge.index() == 1) {
+        Node* const parent = user->InputAt(0);
+        if (parent->opcode() == IrOpcode::kAllocate &&
+            OpParameter<PretenureFlag>(parent) == TENURED) {
+          pretenure = TENURED;
+          break;
+        }
+      }
+    }
+  }
+
   // Determine the top/limit addresses.
   Node* top_address = jsgraph()->ExternalConstant(
       pretenure == NOT_TENURED
           ? ExternalReference::new_space_allocation_top_address(isolate())
           : ExternalReference::old_space_allocation_top_address(isolate()));
   Node* limit_address = jsgraph()->ExternalConstant(
       pretenure == NOT_TENURED
           ? ExternalReference::new_space_allocation_limit_address(isolate())
           : ExternalReference::old_space_allocation_limit_address(isolate()));
 
@@ skipping 373 matching lines @@
   return jsgraph()->common();
 }
 
 MachineOperatorBuilder* MemoryOptimizer::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8