[Turbofan] Simplified lowering to be done concurrently.

src/compiler/simplified-lowering.cc

 // Copyright 2014 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/simplified-lowering.h"
 
 #include <limits>
 
 #include "src/address-map.h"
 #include "src/base/bits.h"
@@ skipping 1091 matching lines @@
         // Write barriers are only for stores of heap objects.
         return kNoWriteBarrier;
       }
       if (field_type->Is(Type::BooleanOrNullOrUndefined()) ||
           value_type->Is(Type::BooleanOrNullOrUndefined())) {
         // Write barriers are not necessary when storing true, false, null or
         // undefined, because these special oddballs are always in the root set.
         return kNoWriteBarrier;
       }
       if (value_type->IsHeapConstant()) {
-        Handle<HeapObject> value_object = value_type->AsHeapConstant()->Value();
-        RootIndexMap root_index_map(jsgraph_->isolate());
-        int root_index = root_index_map.Lookup(*value_object);
-        if (root_index != RootIndexMap::kInvalidRootIndex &&
-            jsgraph_->isolate()->heap()->RootIsImmortalImmovable(root_index)) {
-          // Write barriers are unnecessary for immortal immovable roots.
-          return kNoWriteBarrier;
-        }
-        if (value_object->IsMap()) {
-          // Write barriers for storing maps are cheaper.
-          return kMapWriteBarrier;
+        Heap::RootListIndex root_index;
+        Heap* heap = jsgraph_->isolate()->heap();
+        if (heap->IsRootHandle(value_type->AsHeapConstant()->Value(),
+                               &root_index)) {
+          if (heap->RootIsImmortalImmovable(root_index)) {
+            // Write barriers are unnecessary for immortal immovable roots.
+            return kNoWriteBarrier;
+          }
         }
       }
       if (field_representation == MachineRepresentation::kTaggedPointer ||
           value_representation == MachineRepresentation::kTaggedPointer) {
         // Write barriers for heap objects are cheaper.
         return kPointerWriteBarrier;
       }
       NumberMatcher m(value);
       if (m.HasValue()) {
         if (IsSmiDouble(m.Value())) {
@@ skipping 2325 matching lines @@
         isolate(), graph()->zone(), callable.descriptor(), 0, flags,
         Operator::kNoProperties);
     to_number_operator_.set(common()->Call(desc));
   }
   return to_number_operator_.get();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8