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 38104b89f4935eb20a5c61b630806d5a96df9d5b..ec3b54c7dd13459d8456f2308adcfb9233736e81 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -136,6 +136,9 @@ namespace v8 {
 namespace internal {
 
 enum ElementsKind {
+  // The "fast" kind for elements that only contain SMI values.
+  FAST_SMI_ONLY_ELEMENTS,
+
   // The "fast" kind for tagged values. Must be first to make it possible
   // to efficiently check maps if they have fast elements.

[Yang, 2011/09/19 14:00:15]

Outdated comment. (Any consequences since the assumption in the comment is now
wrong?)

[danno, 2011/09/21 14:32:04]

Done.

   FAST_ELEMENTS,
@@ -160,7 +163,7 @@ 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
 };
 
@@ -1525,8 +1528,10 @@ class JSObject: public JSReceiver {
   MUST_USE_RESULT inline MaybeObject* ResetElements();
   inline ElementsKind GetElementsKind();
   inline ElementsAccessor* GetElementsAccessor();
+  inline bool HasFastSmiOnlyElements();

[Rico, 2011/09/16 09:40:10]

Do we want to include something like HasFastTypeElements that return true if we
have any fast element case? Could make some asserts and predicates easier to
read

   inline bool HasFastElements();
   inline bool HasFastDoubleElements();
+  inline bool HasNonStrictArgumentsElements();
   inline bool HasDictionaryElements();
   inline bool HasExternalPixelElements();
   inline bool HasExternalArrayElements();
@@ -1698,6 +1703,17 @@ class JSObject: public JSReceiver {
   // Tests for the fast common case for property enumeration.
   bool IsSimpleEnum();
 
+  // Makes sure the elements can contain non-smi Object.
+  inline MaybeObject* EnsureCanContainNonSmiElements();
+
+  // Make sure that elements can contain the specified elements.

[Jakob Kummerow, 2011/09/16 16:30:34]

The comments for both these methods deserve better wording. Proposal:
// Makes sure that this object can contain non-Smi objects as elements.

// Makes sure that this object can contain the specified elements.

[danno, 2011/09/21 14:32:04]

Done.

+  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);
@@ -1747,6 +1763,7 @@ 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,
@@ -1769,11 +1786,18 @@ 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);
@@ -4043,8 +4067,12 @@ 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;
   }
@@ -4053,6 +4081,10 @@ 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 &&
@@ -4312,6 +4344,9 @@ 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;
@@ -6872,7 +6907,7 @@ 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);