Line data    Source code

       1             : // Copyright 2018 the V8 project authors. All rights reserved.
       2             : // Use of this source code is governed by a BSD-style license that can be
       3             : // found in the LICENSE file.
       4             : 
       5             : #ifndef V8_OBJECTS_SMI_H_
       6             : #define V8_OBJECTS_SMI_H_
       7             : 
       8             : #include "src/globals.h"
       9             : #include "src/objects/heap-object.h"
      10             : 
      11             : // Has to be the last include (doesn't have include guards):
      12             : #include "src/objects/object-macros.h"
      13             : 
      14             : namespace v8 {
      15             : namespace internal {
      16             : 
      17             : // Smi represents integer Numbers that can be stored in 31 bits.
      18             : // Smis are immediate which means they are NOT allocated in the heap.
      19             : // The ptr_ value has the following format: [31 bit signed int] 0
      20             : // For long smis it has the following format:
      21             : //     [32 bit signed int] [31 bits zero padding] 0
      22             : // Smi stands for small integer.
      23             : class Smi : public Object {
      24             :  public:
      25             :   // This replaces the OBJECT_CONSTRUCTORS macro, because Smis are special
      26             :   // in that we want them to be constexprs.
      27             :   constexpr Smi() : Object() {}
      28             :   explicit constexpr Smi(Address ptr) : Object(ptr) {
      29             : #if V8_CAN_HAVE_DCHECK_IN_CONSTEXPR
      30             :     DCHECK(HAS_SMI_TAG(ptr));
      31             : #endif
      32             :   }
      33             :   Smi* operator->() { return this; }
      34             :   const Smi* operator->() const { return this; }
      35             : 
      36             :   // Returns the integer value.
      37             :   inline int value() const { return Internals::SmiValue(ptr()); }
      38             :   inline Smi ToUint32Smi() {
      39      419940 :     if (value() <= 0) return Smi::FromInt(0);
      40             :     return Smi::FromInt(static_cast<uint32_t>(value()));
      41             :   }
      42             : 
      43             :   // Convert a Smi object to an int.
      44             :   static inline int ToInt(const Object object);
      45             : 
      46             :   // Convert a value to a Smi object.
      47             :   static inline constexpr Smi FromInt(int value) {
      48             : #if V8_CAN_HAVE_DCHECK_IN_CONSTEXPR
      49             :     DCHECK(Smi::IsValid(value));
      50             : #endif
      51             :     return Smi(Internals::IntToSmi(value));
      52             :   }
      53             : 
      54             :   static inline Smi FromIntptr(intptr_t value) {
      55             :     DCHECK(Smi::IsValid(value));
      56             :     int smi_shift_bits = kSmiTagSize + kSmiShiftSize;
      57       96826 :     return Smi((static_cast<Address>(value) << smi_shift_bits) | kSmiTag);
      58             :   }
      59             : 
      60             :   // Given {value} in [0, 2^31-1], force it into Smi range by changing at most
      61             :   // the MSB (leaving the lower 31 bit unchanged).
      62             :   static inline Smi From31BitPattern(int value) {
      63             :     return Smi::FromInt((value << (32 - kSmiValueSize)) >>
      64             :                         (32 - kSmiValueSize));
      65             :   }
      66             : 
      67             :   template <typename E,
      68             :             typename = typename std::enable_if<std::is_enum<E>::value>::type>
      69             :   static inline Smi FromEnum(E value) {
      70             :     STATIC_ASSERT(sizeof(E) <= sizeof(int));
      71      643074 :     return FromInt(static_cast<int>(value));
      72             :   }
      73             : 
      74             :   // Returns whether value can be represented in a Smi.
      75             :   static inline bool constexpr IsValid(intptr_t value) {
      76             : #if V8_CAN_HAVE_DCHECK_IN_CONSTEXPR
      77             :     DCHECK(Internals::IsValidSmi(value) ==
      78             :            (value >= kMinValue && value <= kMaxValue));
      79             : #endif
      80             :     return Internals::IsValidSmi(value);
      81             :   }
      82             : 
      83             :   // Compare two Smis x, y as if they were converted to strings and then
      84             :   // compared lexicographically. Returns:
      85             :   // -1 if x < y.
      86             :   //  0 if x == y.
      87             :   //  1 if x > y.
      88             :   // Returns the result (a tagged Smi) as a raw Address for ExternalReference
      89             :   // usage.
      90             :   V8_EXPORT_PRIVATE static Address LexicographicCompare(Isolate* isolate, Smi x,
      91             :                                                         Smi y);
      92             : 
      93             :   DECL_CAST(Smi)
      94             : 
      95             :   // Dispatched behavior.
      96             :   V8_EXPORT_PRIVATE void SmiPrint(std::ostream& os) const;  // NOLINT
      97             :   DECL_VERIFIER(Smi)
      98             : 
      99             :   // C++ does not allow us to have an object of type Smi within class Smi,
     100             :   // so the kZero value has type Object. Consider it deprecated; new code
     101             :   // should use zero() instead.
     102             :   V8_EXPORT_PRIVATE static constexpr Object kZero = Object(0);
     103             :   // If you need something with type Smi, call zero() instead. Since it is
     104             :   // a constexpr, "calling" it is just as efficient as reading kZero.
     105             :   static inline constexpr Smi zero() { return Smi::FromInt(0); }
     106             :   static constexpr int kMinValue = kSmiMinValue;
     107             :   static constexpr int kMaxValue = kSmiMaxValue;
     108             : };
     109             : 
     110             : }  // namespace internal
     111             : }  // namespace v8
     112             : 
     113             : #include "src/objects/object-macros-undef.h"
     114             : 
     115             : #endif  // V8_OBJECTS_SMI_H_