Allocation space decisions are precisely made in hydrogen.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index d98ce2ff3c8ca0f0322464e1387bbae1d6848653..3158ca86c8f679be4f1e58ec339faaf12a18211a 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -1329,11 +1329,11 @@ HValue* HGraphBuilder::BuildAllocateElements(HValue* context,
     // TODO(hpayer): When pretenuring can be internalized, flags can become
     // private to HAllocate.
     if (IsFastDoubleElementsKind(kind)) {
-      flags = static_cast<HAllocate::Flags>(
-          flags | HAllocate::CAN_ALLOCATE_IN_OLD_DATA_SPACE);
+      flags = HAllocate::SetAllocationFlag(flags,
+          HAllocate::ALLOCATE_IN_OLD_DATA_SPACE);
     } else {
-      flags = static_cast<HAllocate::Flags>(
-          flags | HAllocate::CAN_ALLOCATE_IN_OLD_POINTER_SPACE);
+      flags = HAllocate::SetAllocationFlag(flags,
+          HAllocate::ALLOCATE_IN_OLD_POINTER_SPACE);
     }
   }
 
@@ -4604,7 +4604,7 @@ HInstruction* HOptimizedGraphBuilder::BuildStoreNamedField(
       HInstruction* heap_number_size = Add<HConstant>(HeapNumber::kSize);
       HInstruction* heap_number = Add<HAllocate>(
           environment()->LookupContext(), heap_number_size,
-          HType::HeapNumber(), HAllocate::CAN_ALLOCATE_IN_NEW_SPACE);
+          HType::HeapNumber(), HAllocate::DefaultFlags());
       AddStoreMapConstant(heap_number, isolate()->factory()->heap_number_map());
       AddStore(heap_number, HObjectAccess::ForHeapNumberValue(), value);
       instr = new(zone()) HStoreNamedField(
@@ -7243,8 +7243,8 @@ void HOptimizedGraphBuilder::VisitCallNew(CallNew* expr) {
     HAllocate::Flags flags = HAllocate::DefaultFlags();
     if (FLAG_pretenuring_call_new &&
         isolate()->heap()->ShouldGloballyPretenure()) {
-      flags = static_cast<HAllocate::Flags>(
-          flags | HAllocate::CAN_ALLOCATE_IN_OLD_POINTER_SPACE);
+      flags = HAllocate::SetAllocationFlag(flags,
+          HAllocate::ALLOCATE_IN_OLD_POINTER_SPACE);
     }
     HAllocate* receiver =
         Add<HAllocate>(context, size_in_bytes, HType::JSObject(), flags);
@@ -8329,9 +8329,9 @@ HInstruction* HOptimizedGraphBuilder::BuildFastLiteral(
 
   if (isolate()->heap()->ShouldGloballyPretenure()) {
     if (data_size != 0) {
-      HAllocate::Flags data_flags =
-          static_cast<HAllocate::Flags>(HAllocate::DefaultFlags(kind) |
-              HAllocate::CAN_ALLOCATE_IN_OLD_DATA_SPACE);
+      HAllocate::Flags data_flags = HAllocate::DefaultFlags(kind);
+      data_flags = HAllocate::SetAllocationFlag(data_flags,
+          HAllocate::ALLOCATE_IN_OLD_DATA_SPACE);
       HValue* size_in_bytes = Add<HConstant>(data_size);
       data_target = Add<HAllocate>(context, size_in_bytes, HType::JSObject(),
           data_flags);
@@ -8342,9 +8342,9 @@ HInstruction* HOptimizedGraphBuilder::BuildFastLiteral(
       AddStore(data_target, access, size_in_bytes);
     }
     if (pointer_size != 0) {
-      HAllocate::Flags pointer_flags =
-          static_cast<HAllocate::Flags>(HAllocate::DefaultFlags() |
-              HAllocate::CAN_ALLOCATE_IN_OLD_POINTER_SPACE);
+      HAllocate::Flags pointer_flags = HAllocate::DefaultFlags();
+      pointer_flags =  HAllocate::SetAllocationFlag(pointer_flags,
+          HAllocate::ALLOCATE_IN_OLD_POINTER_SPACE);
       HValue* size_in_bytes = Add<HConstant>(pointer_size);
       target = Add<HAllocate>(context, size_in_bytes, HType::JSObject(),
           pointer_flags);