Faster filling of arrays of holes.

src/utils.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 554 matching lines @@
   while (lhs < limit) {
     int r = static_cast<int>(*lhs) - static_cast<int>(*rhs);
     if (r != 0) return r;
     ++lhs;
     ++rhs;
   }
   return 0;
 }
 
 
+template <typename T>
+static inline void MemsetPointer(T** dest, T* value, int counter) {
+#if defined(V8_HOST_ARCH_IA32)
+#define STOS "stosl"
+#elif defined(V8_HOST_ARCH_X64)
+#define STOS "stosq"
+#endif
+
+#if defined(__GNUC__) && defined(STOS)
+  asm("cld;"
+      "rep ; " STOS
+      : /* no output */
+      : "c" (counter), "a" (value), "D" (dest)
+      : /* no clobbered list as all inputs are considered clobbered */);
+#else
+  for (int i = 0; i < counter; i++) {
+    dest[i] = value;
+  }
+#endif
+
+#undef STOS
+}
+
+
 // Calculate 10^exponent.
 int TenToThe(int exponent);
 
 } }  // namespace v8::internal
 
 #endif  // V8_UTILS_H_