Refactor word copying logic.

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index 8ff1f9b1c826d2e47c2978c9811257c8ec481f35..ba27f07290b8f23803581e82ab295629fc03f1fc 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -597,6 +597,25 @@ static inline void MemsetPointer(T** dest, T* value, int counter) {
 }
 
 
+// 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);