Use untagged int32 values in evaluation of side-effect free expressions.

src/frame-element.h

 // Copyright 2009 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 127 matching lines @@
   bool is_valid() const { return type() != INVALID; }
   bool is_memory() const { return type() == MEMORY; }
   bool is_register() const { return type() == REGISTER; }
   bool is_constant() const { return type() == CONSTANT; }
   bool is_copy() const { return type() == COPY; }
 
   bool is_copied() const { return CopiedField::decode(value_); }
   void set_copied() { value_ = value_ | CopiedField::encode(true); }
   void clear_copied() { value_ = value_ & ~CopiedField::mask(); }
 
+  // An untagged int32 FrameElement represents a signed int32
+  // on the stack.  These are only allowed in a side-effect-free
+  // int32 calculation, and if a non-int32 input shows up or an overflow
+  // occurs, we bail out and drop all the int32 values.
+  void set_untagged_int32(bool value) {
+    value_ &= ~UntaggedInt32Field::mask();
+    value_ |= UntaggedInt32Field::encode(value);
+  }
+  bool is_untagged_int32() const { return UntaggedInt32Field::decode(value_); }
+
   Register reg() const {
     ASSERT(is_register());
     uint32_t reg = DataField::decode(value_);
     Register result;
     result.code_ = reg;
     return result;
   }
 
   Handle<Object> handle() const {
     ASSERT(is_constant());
@@ skipping 90 matching lines @@
     value_ = value_ & ~DataField::mask();
     value_ = value_ | DataField::encode(new_reg.code_);
   }
 
   // Encode type, copied, synced and data in one 32 bit integer.
   uint32_t value_;
 
   class TypeField: public BitField<Type, 0, 3> {};
   class CopiedField: public BitField<bool, 3, 1> {};
   class SyncedField: public BitField<bool, 4, 1> {};
-  class NumberInfoField: public BitField<int, 5, 4> {};
-  class DataField: public BitField<uint32_t, 9, 32 - 9> {};
+  class UntaggedInt32Field: public BitField<bool, 5, 1> {};
+  class NumberInfoField: public BitField<int, 6, 4> {};
+  class DataField: public BitField<uint32_t, 10, 32 - 10> {};
 
   friend class VirtualFrame;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_FRAME_ELEMENT_H_