Implement basic array prefetching hints in Hydrogen.

src/hydrogen-instructions.cc

 // Copyright 2012 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 2030 matching lines @@
     stream->Add(" + %d]", index_offset());
   } else {
     stream->Add("]");
   }
 
   if (HasDependency()) {
     stream->Add(" ");
     dependency()->PrintNameTo(stream);
   }
 
+  stream->Add(" ");
+  prefetch_distance()->PrintNameTo(stream);
   if (RequiresHoleCheck()) {
     stream->Add(" check_hole");
   }
 }
 
 
 bool HLoadKeyed::RequiresHoleCheck() const {
   if (IsFastPackedElementsKind(elements_kind())) {
     return false;
   }
@@ skipping 33 matching lines @@
 
       if (names_cache->enumerable() == object()) {
         HForInCacheArray* index_cache =
             names_cache->index_cache();
         HCheckMapValue* map_check =
             new(block()->zone()) HCheckMapValue(object(), names_cache->map());
         HInstruction* index = new(block()->zone()) HLoadKeyed(
             index_cache,
             key_load->key(),
             key_load->key(),
+            key_load->prefetch_distance(),
             key_load->elements_kind());
         map_check->InsertBefore(this);
         index->InsertBefore(this);
         HLoadFieldByIndex* load = new(block()->zone()) HLoadFieldByIndex(
             object(), index);
         load->InsertBefore(this);
         return load;
       }
     }
   }
@@ skipping 678 matching lines @@
 
 
 void HCheckFunction::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal