Basic support for tracking smi-only arrays on ia32.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 3be92184c8fb58568afb7ed722a6d89df63b08ca..a7336d9143876afa8da092798f198e00e3f627a0 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -137,8 +137,13 @@ namespace v8 {
 namespace internal {
 
 enum ElementsKind {
-  // The "fast" kind for tagged values. Must be first to make it possible
-  // to efficiently check maps if they have fast elements.
+  // The "fast" kind for elements that only contain SMI values. Must be first
+  // to make it possible to efficiently check maps for this kind.
+  FAST_SMI_ONLY_ELEMENTS,
+
+  // The "fast" kind for tagged values. Must be second to make it possible to
+  // efficiently check maps for this and the FAST_SMI_ONLY_ELEMENTS kind
+  // together at once.
   FAST_ELEMENTS,
 
   // The "fast" kind for unwrapped, non-tagged double values.
@@ -161,7 +166,7 @@ enum ElementsKind {
   // Derived constants from ElementsKind
   FIRST_EXTERNAL_ARRAY_ELEMENTS_KIND = EXTERNAL_BYTE_ELEMENTS,
   LAST_EXTERNAL_ARRAY_ELEMENTS_KIND = EXTERNAL_PIXEL_ELEMENTS,
-  FIRST_ELEMENTS_KIND = FAST_ELEMENTS,
+  FIRST_ELEMENTS_KIND = FAST_SMI_ONLY_ELEMENTS,
   LAST_ELEMENTS_KIND = EXTERNAL_PIXEL_ELEMENTS
 };
 
@@ -1415,8 +1420,14 @@ class JSObject: public JSReceiver {
   MUST_USE_RESULT inline MaybeObject* ResetElements();
   inline ElementsKind GetElementsKind();
   inline ElementsAccessor* GetElementsAccessor();
+  inline bool HasFastSmiOnlyElements();
   inline bool HasFastElements();
+  // Returns if an object has either FAST_ELEMENT or FAST_SMI_ONLY_ELEMENT
+  // elements.  TODO(danno): Rename HasFastTypeElements to HasFastElements() and
+  // HasFastElements to HasFastObjectElements.
+  inline bool HasFastTypeElements();
   inline bool HasFastDoubleElements();
+  inline bool HasNonStrictArgumentsElements();
   inline bool HasDictionaryElements();
   inline bool HasExternalPixelElements();
   inline bool HasExternalArrayElements();
@@ -1587,6 +1598,19 @@ class JSObject: public JSReceiver {
   // Tests for the fast common case for property enumeration.
   bool IsSimpleEnum();
 
+  inline void ValidateSmiOnlyElements();
+
+  // Makes sure that this object can contain non-smi Object as elements.
+  inline MaybeObject* EnsureCanContainNonSmiElements();
+
+  // Makes sure that this object can contain the specified elements.
+  inline MaybeObject* EnsureCanContainElements(Object** elements,
+                                               uint32_t count);
+  inline MaybeObject* EnsureCanContainElements(FixedArray* elements);
+  MaybeObject* EnsureCanContainElements(Arguments* arguments,
+                                        uint32_t first_arg,
+                                        uint32_t arg_count);
+
   // Do we want to keep the elements in fast case when increasing the
   // capacity?
   bool ShouldConvertToSlowElements(int new_capacity);
@@ -1636,6 +1660,7 @@ class JSObject: public JSReceiver {
                                               Object* value,
                                               StrictModeFlag strict_mode,
                                               bool check_prototype);
+
   MUST_USE_RESULT MaybeObject* SetDictionaryElement(uint32_t index,
                                                     Object* value,
                                                     StrictModeFlag strict_mode,
@@ -1658,11 +1683,18 @@ class JSObject: public JSReceiver {
   // The undefined object if index is out of bounds.
   MaybeObject* GetElementWithInterceptor(Object* receiver, uint32_t index);
 
+  enum SetFastElementsCapacityMode {
+    kAllowSmiOnlyElements,
+    kDontAllowSmiOnlyElements
+  };
+
   // Replace the elements' backing store with fast elements of the given
   // capacity.  Update the length for JSArrays.  Returns the new backing
   // store.
-  MUST_USE_RESULT MaybeObject* SetFastElementsCapacityAndLength(int capacity,
-                                                                int length);
+  MUST_USE_RESULT MaybeObject* SetFastElementsCapacityAndLength(
+      int capacity,
+      int length,
+      SetFastElementsCapacityMode set_capacity_mode);
   MUST_USE_RESULT MaybeObject* SetFastDoubleElementsCapacityAndLength(
       int capacity,
       int length);
@@ -3960,8 +3992,12 @@ class Map: public HeapObject {
         (bit_field2() & kElementsKindMask) >> kElementsKindShift);
   }
 
+  // Tells whether the instance has fast elements that are only Smis.
+  inline bool has_fast_smi_only_elements() {
+    return elements_kind() == FAST_SMI_ONLY_ELEMENTS;
+  }
+
   // Tells whether the instance has fast elements.
-  // Equivalent to instance->GetElementsKind() == FAST_ELEMENTS.
   inline bool has_fast_elements() {
     return elements_kind() == FAST_ELEMENTS;
   }
@@ -3970,6 +4006,10 @@ class Map: public HeapObject {
     return elements_kind() == FAST_DOUBLE_ELEMENTS;
   }
 
+  inline bool has_non_strict_arguments_elements() {
+    return elements_kind() == NON_STRICT_ARGUMENTS_ELEMENTS;
+  }
+
   inline bool has_external_array_elements() {
     ElementsKind kind(elements_kind());
     return kind >= FIRST_EXTERNAL_ARRAY_ELEMENTS_KIND &&
@@ -4217,7 +4257,7 @@ class Map: public HeapObject {
   static const int kStringWrapperSafeForDefaultValueOf = 2;
   static const int kAttachedToSharedFunctionInfo = 3;
   // No bits can be used after kElementsKindFirstBit, they are all reserved for
-  // storing ElementKind.  for anything other than storing the ElementKind.
+  // storing ElementKind.
   static const int kElementsKindShift = 4;
   static const int kElementsKindBitCount = 4;
 
@@ -4226,6 +4266,9 @@ class Map: public HeapObject {
       ((1 << (kElementsKindShift + kElementsKindBitCount)) - 1);
   static const int8_t kMaximumBitField2FastElementValue = static_cast<int8_t>(
       (FAST_ELEMENTS + 1) << Map::kElementsKindShift) - 1;
+  static const int8_t kMaximumBitField2FastSmiOnlyElementValue =
+      static_cast<int8_t>((FAST_SMI_ONLY_ELEMENTS + 1) <<
+                          Map::kElementsKindShift) - 1;
 
   // Bit positions for bit field 3
   static const int kIsShared = 0;
@@ -6818,7 +6861,7 @@ class JSArray: public JSObject {
   MUST_USE_RESULT MaybeObject* Initialize(int capacity);
 
   // Set the content of the array to the content of storage.
-  inline void SetContent(FixedArray* storage);
+  inline MaybeObject* SetContent(FixedArray* storage);
 
   // Casting.
   static inline JSArray* cast(Object* obj);