Refactor word copying logic.

Review URL: http://codereview.chromium.org/1530005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4310 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/builtins.cc

@@ -268,9 +268,9 @@ static void CopyElements(AssertNoAllocation* no_gc,
                          int src_index,
                          int len) {
   ASSERT(dst != src);  // Use MoveElements instead.
-  memcpy(dst->data_start() + dst_index,
-         src->data_start() + src_index,
-         len * kPointerSize);
+  CopyWords(dst->data_start() + dst_index,
+            src->data_start() + src_index,
+            len);
   WriteBarrierMode mode = dst->GetWriteBarrierMode(*no_gc);
   if (mode == UPDATE_WRITE_BARRIER) {
     Heap::RecordWrites(dst->address(), dst->OffsetOfElementAt(dst_index), len);

src/heap-inl.h

@@ -236,20 +236,7 @@ AllocationSpace Heap::TargetSpaceId(InstanceType type) {
 
 void Heap::CopyBlock(Object** dst, Object** src, int byte_size) {
   ASSERT(IsAligned(byte_size, kPointerSize));
-
-  // Use block copying memcpy if the segment we're copying is
-  // enough to justify the extra call/setup overhead.
-  static const int kBlockCopyLimit = 16 * kPointerSize;
-
-  if (byte_size >= kBlockCopyLimit) {
-    memcpy(dst, src, byte_size);
-  } else {
-    int remaining = byte_size / kPointerSize;
-    do {
-      remaining--;
-      *dst++ = *src++;
-    } while (remaining > 0);
-  }
+  CopyWords(dst, src, byte_size / kPointerSize);
 }
 
 

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);