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

src/register-allocator.h

 // Copyright 2008 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 53 matching lines @@
   // Construct an invalid result.
   Result() { invalidate(); }
 
   // Construct a register Result.
   explicit Result(Register reg, NumberInfo info = NumberInfo::Unknown());
 
   // Construct a Result whose value is a compile-time constant.
   explicit Result(Handle<Object> value) {
     value_ = TypeField::encode(CONSTANT)
         | NumberInfoField::encode(NumberInfo::Uninitialized().ToInt())
+        | IsUntaggedInt32Field::encode(false)
         | DataField::encode(ConstantList()->length());
     ConstantList()->Add(value);
   }
 
   // The copy constructor and assignment operators could each create a new
   // register reference.
   inline Result(const Result& other);
 
   inline Result& operator=(const Result& other);
 
@@ skipping 21 matching lines @@
   inline void set_number_info(NumberInfo info);
   inline bool is_number() const;
   inline bool is_smi() const;
   inline bool is_integer32() const;
   inline bool is_heap_number() const;
 
   bool is_valid() const { return type() != INVALID; }
   bool is_register() const { return type() == REGISTER; }
   bool is_constant() const { return type() == CONSTANT; }
 
+  // An untagged int32 Result contains a signed int32 in a register
+  // or as a constant.  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.  Constants are
+  // not converted to int32 until they are loaded into a register.
+  bool is_untagged_int32() const {
+    return IsUntaggedInt32Field::decode(value_);
+  }
+  void set_untagged_int32(bool value) {
+    value_ &= ~IsUntaggedInt32Field::mask();
+    value_ |= IsUntaggedInt32Field::encode(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(type() == CONSTANT);
     return ConstantList()->at(DataField::decode(value_));
   }
 
   // Move this result to an arbitrary register.  The register is not
   // necessarily spilled from the frame or even singly-referenced outside
   // it.
   void ToRegister();
 
   // Move this result to a specified register.  The register is spilled from
   // the frame, and the register is singly-referenced (by this result)
   // outside the frame.
   void ToRegister(Register reg);
 
  private:
   uint32_t value_;
 
   class TypeField: public BitField<Type, 0, 2> {};
   class NumberInfoField : public BitField<int, 2, 4> {};
-  class DataField: public BitField<uint32_t, 6, 32 - 6> {};
+  class IsUntaggedInt32Field : public BitField<bool, 6, 1> {};
+  class DataField: public BitField<uint32_t, 7, 32 - 7> {};
 
   inline void CopyTo(Result* destination) const;
 
   friend class CodeGeneratorScope;
 };
 
 
 // -------------------------------------------------------------------------
 // Register file
 //
@@ skipping 136 matching lines @@
   }
 
  private:
   CodeGenerator* cgen_;
   RegisterFile registers_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_REGISTER_ALLOCATOR_H_