Tweak minus zero detect of HChange

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 1571 matching lines @@
       (to().IsSmi() ||
        (to().IsTagged() &&
         input_range != NULL &&
         input_range->IsInSmiRange()))) {
     set_type(HType::Smi());
     ClearGVNFlag(kChangesNewSpacePromotion);
   }
   Range* result = (input_range != NULL)
       ? input_range->Copy(zone)
       : HValue::InferRange(zone);
-  result->set_can_be_minus_zero(!to().IsSmiOrInteger32() ||
-                                !(CheckFlag(kAllUsesTruncatingToInt32) ||
-                                  CheckFlag(kAllUsesTruncatingToSmi)));
+
+  if (from().IsSmiOrInteger32() ||
+      (from().IsTagged() && to().IsSmi())) {
+    // Smi/Integer32 can not be minus zero. TaggedToSmi will deopt for non-SMI.
+    result->set_can_be_minus_zero(false);
+  } else {
+    result->set_can_be_minus_zero(!to().IsSmiOrInteger32() ||
+                                  !(CheckFlag(kAllUsesTruncatingToInt32) ||
+                                    CheckFlag(kAllUsesTruncatingToSmi)));
+  }
   if (to().IsSmi()) result->ClampToSmi();
   return result;
 }
 
 
 Range* HConstant::InferRange(Zone* zone) {
   if (has_int32_value_) {
     Range* result = new(zone) Range(int32_value_, int32_value_);
     result->set_can_be_minus_zero(false);
     return result;
@@ skipping 2739 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal