Use a special EnumLength field to indicate number of valid enum cache values.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index c2cb271277afc0e4ccdfb9fd15f3f374aab96cb3..dee547f2f117b93a0651696473b982d928d371fa 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -106,6 +106,7 @@ class LChunkBuilder;
   V(EnterInlined)                              \
   V(FastLiteral)                               \
   V(FixedArrayBaseLength)                      \
+  V(MapEnumLength)                             \

[Michael Starzinger, 2012/08/06 15:06:22]

Alpha-sort!

[Toon Verwaest, 2012/08/07 10:49:47]

Done.

   V(ForceRepresentation)                       \
   V(FunctionLiteral)                           \
   V(GetCachedArrayIndex)                       \
@@ -1905,6 +1906,26 @@ class HFixedArrayBaseLength: public HUnaryOperation {
 };
 
 
+class HMapEnumLength: public HUnaryOperation {
+ public:
+  explicit HMapEnumLength(HValue* value) : HUnaryOperation(value) {
+    set_type(HType::Smi());
+    set_representation(Representation::Tagged());
+    SetFlag(kUseGVN);
+    SetGVNFlag(kDependsOnMaps);
+  }
+
+  virtual Representation RequiredInputRepresentation(int index) {
+    return Representation::Tagged();
+  }
+
+  DECLARE_CONCRETE_INSTRUCTION(MapEnumLength)
+
+ protected:
+  virtual bool DataEquals(HValue* other) { return true; }
+};
+
+
 class HElementsKind: public HUnaryOperation {
  public:
   explicit HElementsKind(HValue* value) : HUnaryOperation(value) {