Eliminate overflow check after integer add and sub if result is truncated to int32.

src/hydrogen.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 2049 matching lines @@
     if (phi->representation().IsInteger32()) {
       phi->SetFlag(HValue::kTruncatingToInt32);
     }
   }
   bool change = true;
   while (change) {
     change = false;
     for (int i = 0; i < phi_list()->length(); i++) {
       HPhi* phi = phi_list()->at(i);
       if (!phi->CheckFlag(HValue::kTruncatingToInt32)) continue;
-      for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
-        HValue* use = it.value();
-        if (!use->CheckFlag(HValue::kTruncatingToInt32)) {
-          phi->ClearFlag(HValue::kTruncatingToInt32);
-          change = true;
-          break;
-        }
+      if (!phi->CheckUsesForFlag(HValue::kTruncatingToInt32)) {
+        phi->ClearFlag(HValue::kTruncatingToInt32);
+        change = true;
       }
     }
   }
 
   for (int i = 0; i < blocks_.length(); ++i) {
     // Process phi instructions first.
     const ZoneList<HPhi*>* phis = blocks_[i]->phis();
     for (int j = 0; j < phis->length(); j++) {
       InsertRepresentationChangesForValue(phis->at(j));
     }
@@ skipping 5934 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal