Implemented fast case for NumberToString where the result is a single charact...

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 2398 matching lines @@
   Handle<JSArray> result = Factory::NewJSArrayWithElements(elements);
   result->set_length(Smi::FromInt(matches));
   return *result;
 }
 
 
 static Object* Runtime_NumberToRadixString(Arguments args) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 2);
 
+  // Fast case where the result is a one char string.

[Kasper Lund, 2009/06/16 06:41:18]

char -> character

+  if (args[0]->IsSmi() && args[1]->IsSmi()) {
+    int value = Smi::cast(args[0])->value();
+    int radix = Smi::cast(args[1])->value();
+    if (value >= 0 && value < radix) {
+      RUNTIME_ASSERT(radix <= 36);
+      // Character array used for conversion.
+      static const char chars[] = "0123456789abcdefghijklmnopqrstuvwxyz";

[Kasper Lund, 2009/06/16 06:41:18]

Should be something like kChars or kCharsMap, right?

+      return Heap::LookupSingleCharacterStringFromCode(chars[value]);
+    }
+  }
+
+  // Slow case.
   CONVERT_DOUBLE_CHECKED(value, args[0]);
   if (isnan(value)) {
     return Heap::AllocateStringFromAscii(CStrVector("NaN"));
   }
   if (isinf(value)) {
     if (value < 0) {
       return Heap::AllocateStringFromAscii(CStrVector("-Infinity"));
     }
     return Heap::AllocateStringFromAscii(CStrVector("Infinity"));
   }
@@ skipping 5026 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();
   }
 }
 
 
 } }  // namespace v8::internal