Fix performance of setRange by avoiding going to Lists.copy

runtime/vm/object.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 6058 matching lines @@
   }
 
   static RawTypedData* New(intptr_t class_id,
                            intptr_t len,
                            Heap::Space space = Heap::kNew);
 
   template <typename DstType, typename SrcType>
   static void Copy(const DstType& dst, intptr_t dst_offset_in_bytes,
                    const SrcType& src, intptr_t src_offset_in_bytes,
                    intptr_t length_in_bytes) {
-    ASSERT(dst.ElementType() == src.ElementType());
     ASSERT(Utils::RangeCheck(src_offset_in_bytes,
                              length_in_bytes,
                              src.LengthInBytes()));
     ASSERT(Utils::RangeCheck(dst_offset_in_bytes,
                              length_in_bytes,
                              dst.LengthInBytes()));
     {
       NoGCScope no_gc;
       if (length_in_bytes > 0) {
         memmove(dst.DataAddr(dst_offset_in_bytes),
                 src.DataAddr(src_offset_in_bytes),
                 length_in_bytes);
       }
     }
   }
 
+
+  template <typename DstType, typename SrcType>
+  static void ClampedCopy(const DstType& dst, intptr_t dst_offset_in_bytes,
+                          const SrcType& src, intptr_t src_offset_in_bytes,
+                          intptr_t length_in_bytes) {
+    ASSERT(Utils::RangeCheck(src_offset_in_bytes,
+                             length_in_bytes,
+                             src.LengthInBytes()));
+    ASSERT(Utils::RangeCheck(dst_offset_in_bytes,
+                             length_in_bytes,
+                             dst.LengthInBytes()));
+    {
+      NoGCScope no_gc;
+      if (length_in_bytes > 0) {
+        uint8_t* dst_data =
+            reinterpret_cast<uint8_t*>(dst.DataAddr(dst_offset_in_bytes));
+        int8_t* src_data =
+            reinterpret_cast<int8_t*>(src.DataAddr(src_offset_in_bytes));
+        for (intptr_t ix = 0; ix < length_in_bytes; ix++) {
+          int8_t v = *src_data;
+          if (v < 0) v = 0;
+          *dst_data = v;
+          src_data++;
+          dst_data++;
+        }
+      }
+    }
+  }
+
   static bool IsTypedData(const Instance& obj) {
     ASSERT(!obj.IsNull());
     intptr_t cid = obj.raw()->GetClassId();
     return RawObject::IsTypedDataClassId(cid);
   }
 
  protected:
   void SetLength(intptr_t value) const {
     raw_ptr()->length_ = Smi::New(value);
   }
@@ skipping 586 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_