Use mutable heapnumbers to store doubles in fields.

src/stub-cache.h

Index: src/stub-cache.h
diff --git a/src/stub-cache.h b/src/stub-cache.h
index 84f7f932b46a824235ab2ded8882f7f23dfe4ff5..00f0b48fd3e87d46539a5c36f55cd2f8320bc8ac 100644
--- a/src/stub-cache.h
+++ b/src/stub-cache.h
@@ -112,7 +112,8 @@ class StubCache {
   Handle<Code> ComputeLoadField(Handle<Name> name,
                                 Handle<JSObject> object,
                                 Handle<JSObject> holder,
-                                PropertyIndex field_index);
+                                PropertyIndex field_index,
+                                Representation representation);
 
   Handle<Code> ComputeLoadCallback(Handle<Name> name,
                                    Handle<JSObject> object,
@@ -147,7 +148,8 @@ class StubCache {
   Handle<Code> ComputeKeyedLoadField(Handle<Name> name,
                                      Handle<JSObject> object,
                                      Handle<JSObject> holder,
-                                     PropertyIndex field_index);
+                                     PropertyIndex field_index,
+                                     Representation representation);
 
   Handle<Code> ComputeKeyedLoadCallback(
       Handle<Name> name,
@@ -506,13 +508,9 @@ class StubCompiler BASE_EMBEDDED {
   static void GenerateFastPropertyLoad(MacroAssembler* masm,
                                        Register dst,
                                        Register src,
-                                       Handle<JSObject> holder,
-                                       PropertyIndex index);
-  static void DoGenerateFastPropertyLoad(MacroAssembler* masm,
-                                         Register dst,
-                                         Register src,
-                                         bool inobject,
-                                         int index);
+                                       bool inobject,
+                                       int index,
+                                       Representation representation);
 
   static void GenerateLoadArrayLength(MacroAssembler* masm,
                                       Register receiver,
@@ -543,7 +541,8 @@ class StubCompiler BASE_EMBEDDED {
                                Register scratch1,
                                Register scratch2,
                                Label* miss_label,
-                               Label* miss_restore_name);
+                               Label* miss_restore_name,
+                               Label* slow);
 
   void GenerateStoreField(MacroAssembler* masm,
                           Handle<JSObject> object,
@@ -565,6 +564,14 @@ class StubCompiler BASE_EMBEDDED {
     }
     return Builtins::kLoadIC_Miss;
   }
+  static Builtins::Name SlowBuiltin(Code::Kind kind) {
+    switch (kind) {
+      case Code::STORE_IC: return Builtins::kStoreIC_Slow;
+      case Code::KEYED_STORE_IC: return Builtins::kKeyedStoreIC_Slow;
+      default: UNREACHABLE();
+    }
+    return Builtins::kStoreIC_Slow;
+  }
   static void TailCallBuiltin(MacroAssembler* masm, Builtins::Name name);
 
   // Generates code that verifies that the property holder has not changed
@@ -643,7 +650,8 @@ class BaseLoadStubCompiler: public StubCompiler {
   Handle<Code> CompileLoadField(Handle<JSObject> object,
                                 Handle<JSObject> holder,
                                 Handle<Name> name,
-                                PropertyIndex index);
+                                PropertyIndex index,
+                                Representation representation);
 
   Handle<Code> CompileLoadCallback(Handle<JSObject> object,
                                    Handle<JSObject> holder,
@@ -695,7 +703,8 @@ class BaseLoadStubCompiler: public StubCompiler {
 
   void GenerateLoadField(Register reg,
                          Handle<JSObject> holder,
-                         PropertyIndex index);
+                         PropertyIndex field,
+                         Representation representation);
   void GenerateLoadConstant(Handle<JSFunction> value);
   void GenerateLoadCallback(Register reg,
                             Handle<ExecutableAccessorInfo> callback);