Fixed floor-of-div optimization.

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 1424 matching lines @@
             val, representation(), false, false);
         result->InsertBefore(this);
         return result;
       }
       return val;
     }
   }
 
   if (op() == kMathFloor) {
     HValue* val = value();
-    if (val->IsChange()) val = HChange::cast(val)->value();
     if (val->IsDiv() && (val->UseCount() == 1)) {
       HDiv* hdiv = HDiv::cast(val);
       HValue* left = hdiv->left();
       HValue* right = hdiv->right();
       // Try to simplify left and right values of the division.
       HValue* new_left = SimplifiedDividendForMathFloorOfDiv(left);
       if (new_left == NULL &&
           hdiv->observed_input_representation(1).IsSmiOrInteger32()) {
         new_left = new(block()->zone()) HChange(
             left, Representation::Integer32(), false, false);
@@ skipping 18 matching lines @@
       if (new_left->IsInstruction() &&
           !HInstruction::cast(new_left)->IsLinked()) {
         HInstruction::cast(new_left)->InsertBefore(this);
       }
       if (new_right->IsInstruction() &&
           !HInstruction::cast(new_right)->IsLinked()) {
         HInstruction::cast(new_right)->InsertBefore(this);
       }
       HMathFloorOfDiv* instr =
           HMathFloorOfDiv::New(block()->zone(), context(), new_left, new_right);
-      // Replace this HMathFloor instruction by the new HMathFloorOfDiv.
       instr->InsertBefore(this);
-      ReplaceAllUsesWith(instr);
-      Kill();
-      // We know the division had no other uses than this HMathFloor. Delete it.
-      // Dead code elimination will deal with |left| and |right| if
-      // appropriate.
-      hdiv->DeleteAndReplaceWith(NULL);
-
-      // Return NULL to remove this instruction from the graph.
-      return NULL;
+      return instr;
     }
   }
   return this;
 }
 
 
 HValue* HCheckInstanceType::Canonicalize() {
   if (check_ == IS_STRING && value()->type().IsString()) {
     return value();
   }
@@ skipping 2942 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal