Improve performance of keyed loads/stores which have a HeapNumber index.

src/ic.cc

Index: src/ic.cc
===================================================================
--- src/ic.cc	(revision 11183)
+++ src/ic.cc	(working copy)
@@ -1053,18 +1053,33 @@
 }
 
 
+static Handle<Object> TryConvertKey(Handle<Object> key, Isolate* isolate) {
+  // This helper implements a few common fast cases for converting
+  // non-smi keys of keyed loads/stores to a smi or a string.
+  if (key->IsHeapNumber()) {
+    double value = Handle<HeapNumber>::cast(key)->value();
+    if (isnan(value)) {
+      key = isolate->factory()->nan_symbol();
+    } else {
+      int int_value = FastD2I(value);
+      if (value == int_value && Smi::IsValid(int_value)) {
+        key = Handle<Smi>(Smi::FromInt(int_value));
+      }
+    }
+  } else if (key->IsUndefined()) {
+    key = isolate->factory()->undefined_symbol();
+  }
+  return key;
+}
+
+
 MaybeObject* KeyedLoadIC::Load(State state,
                                Handle<Object> object,
                                Handle<Object> key,
                                bool force_generic_stub) {
-  // Check for values that can be converted into a symbol.
-  // TODO(1295): Remove this code.
-  if (key->IsHeapNumber() &&
-      isnan(Handle<HeapNumber>::cast(key)->value())) {
-    key = isolate()->factory()->nan_symbol();
-  } else if (key->IsUndefined()) {
-    key = isolate()->factory()->undefined_symbol();
-  }
+  // Check for values that can be converted into a symbol directly or
+  // is representable as a smi.
+  key = TryConvertKey(key, isolate());
 
   if (key->IsSymbol()) {
     Handle<String> name = Handle<String>::cast(key);
@@ -1761,6 +1776,10 @@
                                  Handle<Object> key,
                                  Handle<Object> value,
                                  bool force_generic) {
+  // Check for values that can be converted into a symbol directly or
+  // is representable as a smi.
+  key = TryConvertKey(key, isolate());
+
   if (key->IsSymbol()) {
     Handle<String> name = Handle<String>::cast(key);