Add an IC for CompareNil operations

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 6bda25d14cc37c310eccee3f0e971bd73d5fbc92..098ca9e3232f6b6d93cdfdbdb65a3a09f361fae2 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -407,6 +407,52 @@ void ICCompareStub::Generate(MacroAssembler* masm) {
 }
 
 
+CompareNilICStub::Types CompareNilICStub::GetPatchedICFlags(
+    Code* ic,
+    EqualityKind kind,
+    NilValue nil,
+    Handle<Object> object,
+    bool* already_monomorphic) {
+  Code::ExtraICState extra_state = ic->extra_ic_state();
+  CompareNilICStub::Types types =
+      CompareNilICStub::TypesFromExtraICState(extra_state);
+  ASSERT(types != CompareNilICStub::kFullCompare);
+  *already_monomorphic =
+      (types & CompareNilICStub::kCompareAgainstMonomorphicMap) != 0;
+  if (kind == kStrictEquality) {
+    if (nil == kNullValue) {
+      return CompareNilICStub::kCompareAgainstNull;
+    } else {
+      return CompareNilICStub::kCompareAgainstUndefined;
+    }
+  } else {
+    if (object->IsNull()) {
+      types = static_cast<CompareNilICStub::Types>(
+          types | CompareNilICStub::kCompareAgainstNull);
+    } else if (object->IsUndefined()) {
+      types = static_cast<CompareNilICStub::Types>(
+          types | CompareNilICStub::kCompareAgainstUndefined);
+    } else {
+      if (object->IsUndetectableObject() || !object->IsHeapObject()) {
+        types = CompareNilICStub::kFullCompare;
+      } else {
+        if ((types & CompareNilICStub::kCompareAgainstMonomorphicMap) != 0) {
+          ASSERT_EQ(Code::COMPARE_NIL_IC, ic->kind());
+          Map* monomorphic_map = ic->FindFirstMap();
+          if (monomorphic_map != Handle<HeapObject>::cast(object)->map()) {
+            types = CompareNilICStub::kFullCompare;
+          }
+        } else {
+          types = static_cast<CompareNilICStub::Types>(
+            types | CompareNilICStub::kCompareAgainstMonomorphicMap);
+        }
+      }
+    }
+  }
+  return types;
+}
+
+
 void InstanceofStub::PrintName(StringStream* stream) {
   const char* args = "";
   if (HasArgsInRegisters()) {