Eliminate intentional conversion from Smi to Int32 in HMul

src/hydrogen-representation-changes.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
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@@ skipping 94 matching lines @@
   // conversion.
   ZoneList<HPhi*> worklist(8, zone());
 
   const ZoneList<HPhi*>* phi_list(graph()->phi_list());
   for (int i = 0; i < phi_list->length(); i++) {
     HPhi* phi = phi_list->at(i);
     if (phi->representation().IsInteger32()) {
       phi->SetFlag(HValue::kTruncatingToInt32);
     } else if (phi->representation().IsSmi()) {
       phi->SetFlag(HValue::kTruncatingToSmi);
+      phi->SetFlag(HValue::kTruncatingToInt32);
     }
   }
 
   for (int i = 0; i < phi_list->length(); i++) {
     HPhi* phi = phi_list->at(i);
     for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
       // If a Phi is used as a non-truncating int32 or as a double,
       // clear its "truncating" flag.
       HValue* use = it.value();
       Representation input_representation =
           use->RequiredInputRepresentation(it.index());
       if ((phi->representation().IsInteger32() &&
            !(input_representation.IsInteger32() &&
              use->CheckFlag(HValue::kTruncatingToInt32))) ||
           (phi->representation().IsSmi() &&
            !(input_representation.IsSmi() ||

[Toon Verwaest, 2013/08/10 14:13:19]

What about just cleaning up the code (and making the algorithm accurate) by
splitting it into separate worklists for smi and int32?

if (phi->representation().IsSmiOrInteger32() &&
    !phi->CheckUsesForFlag(HValue::kTruncatingToInt32)) {
  int_worklist.Add(phi, zone());
  phi->ClearFlag(HValue::kTruncatingToInt32);
}

if (phi->representation().IsSmi() &&
    !phi->CheckUsesForFlag(HValue::kTruncatingToSmi)) {
  smi_worklist.Add(phi, zone());
  phi->ClearFlag(HValue::kTruncatingToSmi);
}

And then processing the two worklists individually.

[weiliang.lin2, 2013/08/10 16:43:26]

Done. And to keep trace_representation, add another CheckUsesForFlag function to
return the Instruction without the flag. 

              use->CheckFlag(HValue::kTruncatingToSmi)))) {
         if (FLAG_trace_representation) {
           PrintF("#%d Phi is not truncating because of #%d %s\n",
                  phi->id(), it.value()->id(), it.value()->Mnemonic());
         }
         phi->ClearFlag(HValue::kTruncatingToInt32);
         phi->ClearFlag(HValue::kTruncatingToSmi);
         worklist.Add(phi, zone());
         break;
       }
@@ skipping 32 matching lines @@
     // Process normal instructions.
     for (HInstruction* current = block->first(); current != NULL; ) {
       HInstruction* next = current->next();
       InsertRepresentationChangesForValue(current);
       current = next;
     }
   }
 }
 
 } }  // namespace v8::internal