[turbofan] Add support for transitioning stores to double fields.

src/code-stubs-hydrogen.cc

 // Copyright 2012 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/code-stubs.h"
 
 #include "src/bailout-reason.h"
 #include "src/crankshaft/hydrogen.h"
 #include "src/crankshaft/lithium.h"
 #include "src/field-index.h"
@@ skipping 1123 matching lines @@
   return result;
 }
 
 
 Handle<Code> AllocateHeapNumberStub::GenerateCode() {
   return DoGenerateCode(this);
 }
 
 
 template <>
+HValue* CodeStubGraphBuilder<AllocateMutableHeapNumberStub>::BuildCodeStub() {
+  HValue* result =
+      Add<HAllocate>(Add<HConstant>(HeapNumber::kSize), HType::HeapObject(),
+                     NOT_TENURED, MUTABLE_HEAP_NUMBER_TYPE);
+  AddStoreMapConstant(result, isolate()->factory()->mutable_heap_number_map());
+  return result;
+}
+
+
+Handle<Code> AllocateMutableHeapNumberStub::GenerateCode() {
+  return DoGenerateCode(this);
+}
+
+
+template <>
 HValue* CodeStubGraphBuilder<AllocateInNewSpaceStub>::BuildCodeStub() {
   HValue* result = Add<HAllocate>(GetParameter(0), HType::Tagged(), NOT_TENURED,
                                   JS_OBJECT_TYPE);
   return result;
 }
 
 
 Handle<Code> AllocateInNewSpaceStub::GenerateCode() {
   return DoGenerateCode(this);
 }
@@ skipping 1210 matching lines @@
   return Pop();
 }
 
 
 Handle<Code> KeyedLoadGenericStub::GenerateCode() {
   return DoGenerateCode(this);
 }
 
 }  // namespace internal
 }  // namespace v8