Using array index hash code for string-to-number conversion.

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 4836 matching lines @@
       if (data[start_pos] != 'I') {
         return Heap::nan_value();
       }
     } else if (len - start_pos < 10 && AreDigits(data, start_pos, len)) {
       // The maximal/minimal smi has 10 digits. If the string has less digits we
       // know it will fit into the smi-data type.
       int d = ParseDecimalInteger(data, start_pos, len);
       if (minus) {
         if (d == 0) return Heap::minus_zero_value();
         d = -d;
+      } else if (!subject->HasHashCode() &&
+                 len <= String::kMaxArrayIndexSize &&
+                 (len == 1 || data[0] != '0')) {
+        // String hash is not calculated yet but all the data are present.
+        // Update the hash field to speed up sequential convertions.
+        uint32_t hash = StringHasher::MakeCachedArrayIndex(d, len);
+#ifdef DEBUG
+        ASSERT((hash & String::kContainsCachedArrayIndexMask) == 0);
+        subject->Hash();  // Force hash calculation.
+        ASSERT_EQ(static_cast<int>(subject->hash_field()),
+                  static_cast<int>(hash));
+#endif
+        subject->set_hash_field(hash);
       }
       return Smi::FromInt(d);
     }
   }
 
   // Slower case.
   return Heap::NumberFromDouble(StringToDouble(subject, ALLOW_HEX));
 }
 
 
@@ skipping 5859 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