Improve keyed loads on strings by using a new stub

src/runtime.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1366 matching lines @@
   Object* flat = subject->TryFlatten();
   if (flat->IsFailure()) return flat;
   subject = String::cast(flat);
   if (i >= static_cast<uint32_t>(subject->length())) {
     return Heap::nan_value();
   }
   return Smi::FromInt(subject->Get(i));
 }
 
 
+static Object* CharFromCode(Object* char_code) {
+  uint32_t code;
+  if (Array::IndexFromObject(char_code, &code)) {
+    if (code <= 0xffff) {
+      return Heap::LookupSingleCharacterStringFromCode(code);
+    }
+  }
+  return Heap::empty_string();
+}
+
+
 static Object* Runtime_StringCharCodeAt(Arguments args) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 2);
 
   CONVERT_CHECKED(String, subject, args[0]);
   Object* index = args[1];
   return CharCodeAt(subject, index);
 }
 
 
+static Object* Runtime_StringCharAt(Arguments args) {
+  NoHandleAllocation ha;
+  ASSERT(args.length() == 2);
+  return CharFromCode(Runtime_StringCharCodeAt(args));
+}
+
+
 static Object* Runtime_CharFromCode(Arguments args) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 1);
-  uint32_t code;
-  if (Array::IndexFromObject(args[0], &code)) {
-    if (code <= 0xffff) {
-      return Heap::LookupSingleCharacterStringFromCode(code);
-    }
-  }
-  return Heap::empty_string();
+  return CharFromCode(args[0]);
 }
 
 // Forward declarations.
 static const int kStringBuilderConcatHelperLengthBits = 11;
 static const int kStringBuilderConcatHelperPositionBits = 19;
 
 template <typename schar>
 static inline void StringBuilderConcatHelper(String*,
                                              schar*,
                                              FixedArray*,
@@ skipping 6609 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal