Refactor word copying logic.

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 579 matching lines @@
 #else
   for (int i = 0; i < counter; i++) {
     dest[i] = value;
   }
 #endif
 
 #undef STOS
 }
 
 
+// Copies data from |src| to |dst|.  The data spans MUST not overlap.
+inline void CopyWords(Object** dst, Object** src, int num_words) {
+  ASSERT(Min(dst, src) + num_words <= Max(dst, src));
+  // Use block copying memcpy if the segment we're copying is
+  // enough to justify the extra call/setup overhead.
+  static const int kBlockCopyLimit = 16;
+
+  if (num_words >= kBlockCopyLimit) {
+    memcpy(dst, src, num_words * kPointerSize);
+  } else {
+    int remaining = num_words;
+    do {
+      remaining--;
+      *dst++ = *src++;
+    } while (remaining > 0);
+  }
+}
+
+
 // Calculate 10^exponent.
 int TenToThe(int exponent);
 
 
 // The type-based aliasing rule allows the compiler to assume that pointers of
 // different types (for some definition of different) never alias each other.
 // Thus the following code does not work:
 //
 // float f = foo();
 // int fbits = *(int*)(&f);
@@ skipping 23 matching lines @@
 
   Dest dest;
   memcpy(&dest, &source, sizeof(dest));
   return dest;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_UTILS_H_