Give uses within a loop a greater weight when doing representation inference.

src/hydrogen.cc

 // Copyright 2011 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 1634 matching lines @@
 
 Representation HInferRepresentation::TryChange(HValue* value) {
   // Array of use counts for each representation.
   int use_count[Representation::kNumRepresentations] = { 0 };
 
   for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) {
     HValue* use = it.value();
     Representation rep = use->RequiredInputRepresentation(it.index());
     if (rep.IsNone()) continue;
     if (use->IsPhi()) HPhi::cast(use)->AddIndirectUsesTo(&use_count[0]);
-    ++use_count[rep.kind()];
+    use_count[rep.kind()] += use->LoopWeight();
   }
   int tagged_count = use_count[Representation::kTagged];
   int double_count = use_count[Representation::kDouble];
   int int32_count = use_count[Representation::kInteger32];
   int non_tagged_count = double_count + int32_count;
 
   // If a non-loop phi has tagged uses, don't convert it to untagged.
   if (value->IsPhi() && !value->block()->IsLoopHeader() && tagged_count > 0) {
     return Representation::None();
   }
@@ skipping 5321 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal