Improve keyed loads on strings by using a new stub

src/builtins.h

 // Copyright 2006-2008 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 56 matching lines @@
   V(LoadIC_PreMonomorphic,      LOAD_IC, PREMONOMORPHIC)                  \
   V(LoadIC_Normal,              LOAD_IC, MONOMORPHIC)                     \
   V(LoadIC_ArrayLength,         LOAD_IC, MONOMORPHIC)                     \
   V(LoadIC_StringLength,        LOAD_IC, MONOMORPHIC)                     \
   V(LoadIC_FunctionPrototype,   LOAD_IC, MONOMORPHIC)                     \
   V(LoadIC_Megamorphic,         LOAD_IC, MEGAMORPHIC)                     \
                                                                           \
   V(KeyedLoadIC_Initialize,     KEYED_LOAD_IC, UNINITIALIZED)             \
   V(KeyedLoadIC_PreMonomorphic, KEYED_LOAD_IC, PREMONOMORPHIC)            \
   V(KeyedLoadIC_Generic,        KEYED_LOAD_IC, MEGAMORPHIC)               \
+  V(KeyedLoadIC_String,         KEYED_LOAD_IC, MEGAMORPHIC)               \
   V(KeyedLoadIC_ExternalByteArray,          KEYED_LOAD_IC, MEGAMORPHIC)   \
   V(KeyedLoadIC_ExternalUnsignedByteArray,  KEYED_LOAD_IC, MEGAMORPHIC)   \
   V(KeyedLoadIC_ExternalShortArray,         KEYED_LOAD_IC, MEGAMORPHIC)   \
   V(KeyedLoadIC_ExternalUnsignedShortArray, KEYED_LOAD_IC, MEGAMORPHIC)   \
   V(KeyedLoadIC_ExternalIntArray,           KEYED_LOAD_IC, MEGAMORPHIC)   \
   V(KeyedLoadIC_ExternalUnsignedIntArray,   KEYED_LOAD_IC, MEGAMORPHIC)   \
   V(KeyedLoadIC_ExternalFloatArray,         KEYED_LOAD_IC, MEGAMORPHIC)   \
                                                                           \
   V(StoreIC_Initialize,         STORE_IC, UNINITIALIZED)                  \
   V(StoreIC_Megamorphic,        STORE_IC, MEGAMORPHIC)                    \
@@ skipping 53 matching lines @@
   V(GET_KEYS, 0)                         \
   V(FILTER_KEY, 1)                       \
   V(CALL_NON_FUNCTION, 0)                \
   V(CALL_NON_FUNCTION_AS_CONSTRUCTOR, 0) \
   V(TO_OBJECT, 0)                        \
   V(TO_NUMBER, 0)                        \
   V(TO_STRING, 0)                        \
   V(STRING_ADD_LEFT, 1)                  \
   V(STRING_ADD_RIGHT, 1)                 \
   V(APPLY_PREPARE, 1)                    \
-  V(APPLY_OVERFLOW, 1)
+  V(APPLY_OVERFLOW, 1)                   \
+  V(STRING_CHAR_AT, 1)
 
 
 class ObjectVisitor;
 
 
 class Builtins : public AllStatic {
  public:
   // Generate all builtin code objects. Should be called once during
   // VM initialization.
   static void Setup(bool create_heap_objects);
@@ skipping 73 matching lines @@
   static void Generate_FunctionCall(MacroAssembler* masm);
   static void Generate_FunctionApply(MacroAssembler* masm);
 
   static void Generate_ArrayCode(MacroAssembler* masm);
   static void Generate_ArrayConstructCode(MacroAssembler* masm);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_BUILTINS_H_