[turbofan] Add AllocateHeapNumberStub to avoid runtime call.

src/code-stubs-hydrogen.cc

Index: src/code-stubs-hydrogen.cc
diff --git a/src/code-stubs-hydrogen.cc b/src/code-stubs-hydrogen.cc
index e3cbe7d588cbb19791576f0cbdd73f2c8db22885..5579e054cdcdbe74b44e26efd8a9dc8b12ec3306 100644
--- a/src/code-stubs-hydrogen.cc
+++ b/src/code-stubs-hydrogen.cc
@@ -883,6 +883,22 @@ Handle<Code> TransitionElementsKindStub::GenerateCode() {
   return DoGenerateCode(this);
 }
 
+
+template <>
+HValue* CodeStubGraphBuilder<AllocateHeapNumberStub>::BuildCodeStub() {
+  HValue* result =
+      Add<HAllocate>(Add<HConstant>(HeapNumber::kSize), HType::HeapNumber(),
+                     NOT_TENURED, HEAP_NUMBER_TYPE);
+  AddStoreMapConstant(result, isolate()->factory()->heap_number_map());
+  return result;
+}
+
+
+Handle<Code> AllocateHeapNumberStub::GenerateCode() {
+  return DoGenerateCode(this);
+}
+
+
 HValue* CodeStubGraphBuilderBase::BuildArrayConstructor(
     ElementsKind kind,
     AllocationSiteOverrideMode override_mode,