Home | History | Annotate | Download | only in IR
      1 //===-- llvm/Constants.h - Constant class subclass definitions --*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 /// @file
     11 /// This file contains the declarations for the subclasses of Constant,
     12 /// which represent the different flavors of constant values that live in LLVM.
     13 /// Note that Constants are immutable (once created they never change) and are
     14 /// fully shared by structural equivalence.  This means that two structurally
     15 /// equivalent constants will always have the same address.  Constants are
     16 /// created on demand as needed and never deleted: thus clients don't have to
     17 /// worry about the lifetime of the objects.
     18 //
     19 //===----------------------------------------------------------------------===//
     20 
     21 #ifndef LLVM_IR_CONSTANTS_H
     22 #define LLVM_IR_CONSTANTS_H
     23 
     24 #include "llvm/ADT/APFloat.h"
     25 #include "llvm/ADT/APInt.h"
     26 #include "llvm/ADT/ArrayRef.h"
     27 #include "llvm/ADT/None.h"
     28 #include "llvm/ADT/Optional.h"
     29 #include "llvm/ADT/STLExtras.h"
     30 #include "llvm/ADT/StringRef.h"
     31 #include "llvm/IR/Constant.h"
     32 #include "llvm/IR/DerivedTypes.h"
     33 #include "llvm/IR/OperandTraits.h"
     34 #include "llvm/IR/User.h"
     35 #include "llvm/IR/Value.h"
     36 #include "llvm/Support/Casting.h"
     37 #include "llvm/Support/Compiler.h"
     38 #include "llvm/Support/ErrorHandling.h"
     39 #include <cassert>
     40 #include <cstddef>
     41 #include <cstdint>
     42 
     43 namespace llvm {
     44 
     45 class ArrayType;
     46 class IntegerType;
     47 class PointerType;
     48 class SequentialType;
     49 class StructType;
     50 class VectorType;
     51 template <class ConstantClass> struct ConstantAggrKeyType;
     52 
     53 /// Base class for constants with no operands.
     54 ///
     55 /// These constants have no operands; they represent their data directly.
     56 /// Since they can be in use by unrelated modules (and are never based on
     57 /// GlobalValues), it never makes sense to RAUW them.
     58 class ConstantData : public Constant {
     59   friend class Constant;
     60 
     61   Value *handleOperandChangeImpl(Value *From, Value *To) {
     62     llvm_unreachable("Constant data does not have operands!");
     63   }
     64 
     65 protected:
     66   explicit ConstantData(Type *Ty, ValueTy VT) : Constant(Ty, VT, nullptr, 0) {}
     67 
     68   void *operator new(size_t s) { return User::operator new(s, 0); }
     69 
     70 public:
     71   ConstantData(const ConstantData &) = delete;
     72 
     73   /// Methods to support type inquiry through isa, cast, and dyn_cast.
     74   static bool classof(const Value *V) {
     75     return V->getValueID() >= ConstantDataFirstVal &&
     76            V->getValueID() <= ConstantDataLastVal;
     77   }
     78 };
     79 
     80 //===----------------------------------------------------------------------===//
     81 /// This is the shared class of boolean and integer constants. This class
     82 /// represents both boolean and integral constants.
     83 /// @brief Class for constant integers.
     84 class ConstantInt final : public ConstantData {
     85   friend class Constant;
     86 
     87   APInt Val;
     88 
     89   ConstantInt(IntegerType *Ty, const APInt& V);
     90 
     91   void destroyConstantImpl();
     92 
     93 public:
     94   ConstantInt(const ConstantInt &) = delete;
     95 
     96   static ConstantInt *getTrue(LLVMContext &Context);
     97   static ConstantInt *getFalse(LLVMContext &Context);
     98   static Constant *getTrue(Type *Ty);
     99   static Constant *getFalse(Type *Ty);
    100 
    101   /// If Ty is a vector type, return a Constant with a splat of the given
    102   /// value. Otherwise return a ConstantInt for the given value.
    103   static Constant *get(Type *Ty, uint64_t V, bool isSigned = false);
    104 
    105   /// Return a ConstantInt with the specified integer value for the specified
    106   /// type. If the type is wider than 64 bits, the value will be zero-extended
    107   /// to fit the type, unless isSigned is true, in which case the value will
    108   /// be interpreted as a 64-bit signed integer and sign-extended to fit
    109   /// the type.
    110   /// @brief Get a ConstantInt for a specific value.
    111   static ConstantInt *get(IntegerType *Ty, uint64_t V,
    112                           bool isSigned = false);
    113 
    114   /// Return a ConstantInt with the specified value for the specified type. The
    115   /// value V will be canonicalized to a an unsigned APInt. Accessing it with
    116   /// either getSExtValue() or getZExtValue() will yield a correctly sized and
    117   /// signed value for the type Ty.
    118   /// @brief Get a ConstantInt for a specific signed value.
    119   static ConstantInt *getSigned(IntegerType *Ty, int64_t V);
    120   static Constant *getSigned(Type *Ty, int64_t V);
    121 
    122   /// Return a ConstantInt with the specified value and an implied Type. The
    123   /// type is the integer type that corresponds to the bit width of the value.
    124   static ConstantInt *get(LLVMContext &Context, const APInt &V);
    125 
    126   /// Return a ConstantInt constructed from the string strStart with the given
    127   /// radix.
    128   static ConstantInt *get(IntegerType *Ty, StringRef Str,
    129                           uint8_t radix);
    130 
    131   /// If Ty is a vector type, return a Constant with a splat of the given
    132   /// value. Otherwise return a ConstantInt for the given value.
    133   static Constant *get(Type* Ty, const APInt& V);
    134 
    135   /// Return the constant as an APInt value reference. This allows clients to
    136   /// obtain a full-precision copy of the value.
    137   /// @brief Return the constant's value.
    138   inline const APInt &getValue() const {
    139     return Val;
    140   }
    141 
    142   /// getBitWidth - Return the bitwidth of this constant.
    143   unsigned getBitWidth() const { return Val.getBitWidth(); }
    144 
    145   /// Return the constant as a 64-bit unsigned integer value after it
    146   /// has been zero extended as appropriate for the type of this constant. Note
    147   /// that this method can assert if the value does not fit in 64 bits.
    148   /// @brief Return the zero extended value.
    149   inline uint64_t getZExtValue() const {
    150     return Val.getZExtValue();
    151   }
    152 
    153   /// Return the constant as a 64-bit integer value after it has been sign
    154   /// extended as appropriate for the type of this constant. Note that
    155   /// this method can assert if the value does not fit in 64 bits.
    156   /// @brief Return the sign extended value.
    157   inline int64_t getSExtValue() const {
    158     return Val.getSExtValue();
    159   }
    160 
    161   /// A helper method that can be used to determine if the constant contained
    162   /// within is equal to a constant.  This only works for very small values,
    163   /// because this is all that can be represented with all types.
    164   /// @brief Determine if this constant's value is same as an unsigned char.
    165   bool equalsInt(uint64_t V) const {
    166     return Val == V;
    167   }
    168 
    169   /// getType - Specialize the getType() method to always return an IntegerType,
    170   /// which reduces the amount of casting needed in parts of the compiler.
    171   ///
    172   inline IntegerType *getType() const {
    173     return cast<IntegerType>(Value::getType());
    174   }
    175 
    176   /// This static method returns true if the type Ty is big enough to
    177   /// represent the value V. This can be used to avoid having the get method
    178   /// assert when V is larger than Ty can represent. Note that there are two
    179   /// versions of this method, one for unsigned and one for signed integers.
    180   /// Although ConstantInt canonicalizes everything to an unsigned integer,
    181   /// the signed version avoids callers having to convert a signed quantity
    182   /// to the appropriate unsigned type before calling the method.
    183   /// @returns true if V is a valid value for type Ty
    184   /// @brief Determine if the value is in range for the given type.
    185   static bool isValueValidForType(Type *Ty, uint64_t V);
    186   static bool isValueValidForType(Type *Ty, int64_t V);
    187 
    188   bool isNegative() const { return Val.isNegative(); }
    189 
    190   /// This is just a convenience method to make client code smaller for a
    191   /// common code. It also correctly performs the comparison without the
    192   /// potential for an assertion from getZExtValue().
    193   bool isZero() const {
    194     return Val.isNullValue();
    195   }
    196 
    197   /// This is just a convenience method to make client code smaller for a
    198   /// common case. It also correctly performs the comparison without the
    199   /// potential for an assertion from getZExtValue().
    200   /// @brief Determine if the value is one.
    201   bool isOne() const {
    202     return Val.isOneValue();
    203   }
    204 
    205   /// This function will return true iff every bit in this constant is set
    206   /// to true.
    207   /// @returns true iff this constant's bits are all set to true.
    208   /// @brief Determine if the value is all ones.
    209   bool isMinusOne() const {
    210     return Val.isAllOnesValue();
    211   }
    212 
    213   /// This function will return true iff this constant represents the largest
    214   /// value that may be represented by the constant's type.
    215   /// @returns true iff this is the largest value that may be represented
    216   /// by this type.
    217   /// @brief Determine if the value is maximal.
    218   bool isMaxValue(bool isSigned) const {
    219     if (isSigned)
    220       return Val.isMaxSignedValue();
    221     else
    222       return Val.isMaxValue();
    223   }
    224 
    225   /// This function will return true iff this constant represents the smallest
    226   /// value that may be represented by this constant's type.
    227   /// @returns true if this is the smallest value that may be represented by
    228   /// this type.
    229   /// @brief Determine if the value is minimal.
    230   bool isMinValue(bool isSigned) const {
    231     if (isSigned)
    232       return Val.isMinSignedValue();
    233     else
    234       return Val.isMinValue();
    235   }
    236 
    237   /// This function will return true iff this constant represents a value with
    238   /// active bits bigger than 64 bits or a value greater than the given uint64_t
    239   /// value.
    240   /// @returns true iff this constant is greater or equal to the given number.
    241   /// @brief Determine if the value is greater or equal to the given number.
    242   bool uge(uint64_t Num) const {
    243     return Val.uge(Num);
    244   }
    245 
    246   /// getLimitedValue - If the value is smaller than the specified limit,
    247   /// return it, otherwise return the limit value.  This causes the value
    248   /// to saturate to the limit.
    249   /// @returns the min of the value of the constant and the specified value
    250   /// @brief Get the constant's value with a saturation limit
    251   uint64_t getLimitedValue(uint64_t Limit = ~0ULL) const {
    252     return Val.getLimitedValue(Limit);
    253   }
    254 
    255   /// @brief Methods to support type inquiry through isa, cast, and dyn_cast.
    256   static bool classof(const Value *V) {
    257     return V->getValueID() == ConstantIntVal;
    258   }
    259 };
    260 
    261 //===----------------------------------------------------------------------===//
    262 /// ConstantFP - Floating Point Values [float, double]
    263 ///
    264 class ConstantFP final : public ConstantData {
    265   friend class Constant;
    266 
    267   APFloat Val;
    268 
    269   ConstantFP(Type *Ty, const APFloat& V);
    270 
    271   void destroyConstantImpl();
    272 
    273 public:
    274   ConstantFP(const ConstantFP &) = delete;
    275 
    276   /// Floating point negation must be implemented with f(x) = -0.0 - x. This
    277   /// method returns the negative zero constant for floating point or vector
    278   /// floating point types; for all other types, it returns the null value.
    279   static Constant *getZeroValueForNegation(Type *Ty);
    280 
    281   /// This returns a ConstantFP, or a vector containing a splat of a ConstantFP,
    282   /// for the specified value in the specified type. This should only be used
    283   /// for simple constant values like 2.0/1.0 etc, that are known-valid both as
    284   /// host double and as the target format.
    285   static Constant *get(Type* Ty, double V);
    286   static Constant *get(Type* Ty, StringRef Str);
    287   static ConstantFP *get(LLVMContext &Context, const APFloat &V);
    288   static Constant *getNaN(Type *Ty, bool Negative = false, unsigned type = 0);
    289   static Constant *getNegativeZero(Type *Ty);
    290   static Constant *getInfinity(Type *Ty, bool Negative = false);
    291 
    292   /// Return true if Ty is big enough to represent V.
    293   static bool isValueValidForType(Type *Ty, const APFloat &V);
    294   inline const APFloat &getValueAPF() const { return Val; }
    295 
    296   /// Return true if the value is positive or negative zero.
    297   bool isZero() const { return Val.isZero(); }
    298 
    299   /// Return true if the sign bit is set.
    300   bool isNegative() const { return Val.isNegative(); }
    301 
    302   /// Return true if the value is infinity
    303   bool isInfinity() const { return Val.isInfinity(); }
    304 
    305   /// Return true if the value is a NaN.
    306   bool isNaN() const { return Val.isNaN(); }
    307 
    308   /// We don't rely on operator== working on double values, as it returns true
    309   /// for things that are clearly not equal, like -0.0 and 0.0.
    310   /// As such, this method can be used to do an exact bit-for-bit comparison of
    311   /// two floating point values.  The version with a double operand is retained
    312   /// because it's so convenient to write isExactlyValue(2.0), but please use
    313   /// it only for simple constants.
    314   bool isExactlyValue(const APFloat &V) const;
    315 
    316   bool isExactlyValue(double V) const {
    317     bool ignored;
    318     APFloat FV(V);
    319     FV.convert(Val.getSemantics(), APFloat::rmNearestTiesToEven, &ignored);
    320     return isExactlyValue(FV);
    321   }
    322 
    323   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    324   static bool classof(const Value *V) {
    325     return V->getValueID() == ConstantFPVal;
    326   }
    327 };
    328 
    329 //===----------------------------------------------------------------------===//
    330 /// All zero aggregate value
    331 ///
    332 class ConstantAggregateZero final : public ConstantData {
    333   friend class Constant;
    334 
    335   explicit ConstantAggregateZero(Type *Ty)
    336       : ConstantData(Ty, ConstantAggregateZeroVal) {}
    337 
    338   void destroyConstantImpl();
    339 
    340 public:
    341   ConstantAggregateZero(const ConstantAggregateZero &) = delete;
    342 
    343   static ConstantAggregateZero *get(Type *Ty);
    344 
    345   /// If this CAZ has array or vector type, return a zero with the right element
    346   /// type.
    347   Constant *getSequentialElement() const;
    348 
    349   /// If this CAZ has struct type, return a zero with the right element type for
    350   /// the specified element.
    351   Constant *getStructElement(unsigned Elt) const;
    352 
    353   /// Return a zero of the right value for the specified GEP index if we can,
    354   /// otherwise return null (e.g. if C is a ConstantExpr).
    355   Constant *getElementValue(Constant *C) const;
    356 
    357   /// Return a zero of the right value for the specified GEP index.
    358   Constant *getElementValue(unsigned Idx) const;
    359 
    360   /// Return the number of elements in the array, vector, or struct.
    361   unsigned getNumElements() const;
    362 
    363   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    364   ///
    365   static bool classof(const Value *V) {
    366     return V->getValueID() == ConstantAggregateZeroVal;
    367   }
    368 };
    369 
    370 /// Base class for aggregate constants (with operands).
    371 ///
    372 /// These constants are aggregates of other constants, which are stored as
    373 /// operands.
    374 ///
    375 /// Subclasses are \a ConstantStruct, \a ConstantArray, and \a
    376 /// ConstantVector.
    377 ///
    378 /// \note Some subclasses of \a ConstantData are semantically aggregates --
    379 /// such as \a ConstantDataArray -- but are not subclasses of this because they
    380 /// use operands.
    381 class ConstantAggregate : public Constant {
    382 protected:
    383   ConstantAggregate(CompositeType *T, ValueTy VT, ArrayRef<Constant *> V);
    384 
    385 public:
    386   /// Transparently provide more efficient getOperand methods.
    387   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Constant);
    388 
    389   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    390   static bool classof(const Value *V) {
    391     return V->getValueID() >= ConstantAggregateFirstVal &&
    392            V->getValueID() <= ConstantAggregateLastVal;
    393   }
    394 };
    395 
    396 template <>
    397 struct OperandTraits<ConstantAggregate>
    398     : public VariadicOperandTraits<ConstantAggregate> {};
    399 
    400 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantAggregate, Constant)
    401 
    402 //===----------------------------------------------------------------------===//
    403 /// ConstantArray - Constant Array Declarations
    404 ///
    405 class ConstantArray final : public ConstantAggregate {
    406   friend struct ConstantAggrKeyType<ConstantArray>;
    407   friend class Constant;
    408 
    409   ConstantArray(ArrayType *T, ArrayRef<Constant *> Val);
    410 
    411   void destroyConstantImpl();
    412   Value *handleOperandChangeImpl(Value *From, Value *To);
    413 
    414 public:
    415   // ConstantArray accessors
    416   static Constant *get(ArrayType *T, ArrayRef<Constant*> V);
    417 
    418 private:
    419   static Constant *getImpl(ArrayType *T, ArrayRef<Constant *> V);
    420 
    421 public:
    422   /// Specialize the getType() method to always return an ArrayType,
    423   /// which reduces the amount of casting needed in parts of the compiler.
    424   inline ArrayType *getType() const {
    425     return cast<ArrayType>(Value::getType());
    426   }
    427 
    428   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    429   static bool classof(const Value *V) {
    430     return V->getValueID() == ConstantArrayVal;
    431   }
    432 };
    433 
    434 //===----------------------------------------------------------------------===//
    435 // Constant Struct Declarations
    436 //
    437 class ConstantStruct final : public ConstantAggregate {
    438   friend struct ConstantAggrKeyType<ConstantStruct>;
    439   friend class Constant;
    440 
    441   ConstantStruct(StructType *T, ArrayRef<Constant *> Val);
    442 
    443   void destroyConstantImpl();
    444   Value *handleOperandChangeImpl(Value *From, Value *To);
    445 
    446 public:
    447   // ConstantStruct accessors
    448   static Constant *get(StructType *T, ArrayRef<Constant*> V);
    449 
    450   template <typename... Csts>
    451   static typename std::enable_if<are_base_of<Constant, Csts...>::value,
    452                                  Constant *>::type
    453   get(StructType *T, Csts *... Vs) {
    454     SmallVector<Constant *, 8> Values({Vs...});
    455     return get(T, Values);
    456   }
    457 
    458   /// Return an anonymous struct that has the specified elements.
    459   /// If the struct is possibly empty, then you must specify a context.
    460   static Constant *getAnon(ArrayRef<Constant*> V, bool Packed = false) {
    461     return get(getTypeForElements(V, Packed), V);
    462   }
    463   static Constant *getAnon(LLVMContext &Ctx,
    464                            ArrayRef<Constant*> V, bool Packed = false) {
    465     return get(getTypeForElements(Ctx, V, Packed), V);
    466   }
    467 
    468   /// Return an anonymous struct type to use for a constant with the specified
    469   /// set of elements. The list must not be empty.
    470   static StructType *getTypeForElements(ArrayRef<Constant*> V,
    471                                         bool Packed = false);
    472   /// This version of the method allows an empty list.
    473   static StructType *getTypeForElements(LLVMContext &Ctx,
    474                                         ArrayRef<Constant*> V,
    475                                         bool Packed = false);
    476 
    477   /// Specialization - reduce amount of casting.
    478   inline StructType *getType() const {
    479     return cast<StructType>(Value::getType());
    480   }
    481 
    482   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    483   static bool classof(const Value *V) {
    484     return V->getValueID() == ConstantStructVal;
    485   }
    486 };
    487 
    488 //===----------------------------------------------------------------------===//
    489 /// Constant Vector Declarations
    490 ///
    491 class ConstantVector final : public ConstantAggregate {
    492   friend struct ConstantAggrKeyType<ConstantVector>;
    493   friend class Constant;
    494 
    495   ConstantVector(VectorType *T, ArrayRef<Constant *> Val);
    496 
    497   void destroyConstantImpl();
    498   Value *handleOperandChangeImpl(Value *From, Value *To);
    499 
    500 public:
    501   // ConstantVector accessors
    502   static Constant *get(ArrayRef<Constant*> V);
    503 
    504 private:
    505   static Constant *getImpl(ArrayRef<Constant *> V);
    506 
    507 public:
    508   /// Return a ConstantVector with the specified constant in each element.
    509   static Constant *getSplat(unsigned NumElts, Constant *Elt);
    510 
    511   /// Specialize the getType() method to always return a VectorType,
    512   /// which reduces the amount of casting needed in parts of the compiler.
    513   inline VectorType *getType() const {
    514     return cast<VectorType>(Value::getType());
    515   }
    516 
    517   /// If this is a splat constant, meaning that all of the elements have the
    518   /// same value, return that value. Otherwise return NULL.
    519   Constant *getSplatValue() const;
    520 
    521   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    522   static bool classof(const Value *V) {
    523     return V->getValueID() == ConstantVectorVal;
    524   }
    525 };
    526 
    527 //===----------------------------------------------------------------------===//
    528 /// A constant pointer value that points to null
    529 ///
    530 class ConstantPointerNull final : public ConstantData {
    531   friend class Constant;
    532 
    533   explicit ConstantPointerNull(PointerType *T)
    534       : ConstantData(T, Value::ConstantPointerNullVal) {}
    535 
    536   void destroyConstantImpl();
    537 
    538 public:
    539   ConstantPointerNull(const ConstantPointerNull &) = delete;
    540 
    541   /// Static factory methods - Return objects of the specified value
    542   static ConstantPointerNull *get(PointerType *T);
    543 
    544   /// Specialize the getType() method to always return an PointerType,
    545   /// which reduces the amount of casting needed in parts of the compiler.
    546   inline PointerType *getType() const {
    547     return cast<PointerType>(Value::getType());
    548   }
    549 
    550   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    551   static bool classof(const Value *V) {
    552     return V->getValueID() == ConstantPointerNullVal;
    553   }
    554 };
    555 
    556 //===----------------------------------------------------------------------===//
    557 /// ConstantDataSequential - A vector or array constant whose element type is a
    558 /// simple 1/2/4/8-byte integer or float/double, and whose elements are just
    559 /// simple data values (i.e. ConstantInt/ConstantFP).  This Constant node has no
    560 /// operands because it stores all of the elements of the constant as densely
    561 /// packed data, instead of as Value*'s.
    562 ///
    563 /// This is the common base class of ConstantDataArray and ConstantDataVector.
    564 ///
    565 class ConstantDataSequential : public ConstantData {
    566   friend class LLVMContextImpl;
    567   friend class Constant;
    568 
    569   /// A pointer to the bytes underlying this constant (which is owned by the
    570   /// uniquing StringMap).
    571   const char *DataElements;
    572 
    573   /// This forms a link list of ConstantDataSequential nodes that have
    574   /// the same value but different type.  For example, 0,0,0,1 could be a 4
    575   /// element array of i8, or a 1-element array of i32.  They'll both end up in
    576   /// the same StringMap bucket, linked up.
    577   ConstantDataSequential *Next;
    578 
    579   void destroyConstantImpl();
    580 
    581 protected:
    582   explicit ConstantDataSequential(Type *ty, ValueTy VT, const char *Data)
    583       : ConstantData(ty, VT), DataElements(Data), Next(nullptr) {}
    584   ~ConstantDataSequential() { delete Next; }
    585 
    586   static Constant *getImpl(StringRef Bytes, Type *Ty);
    587 
    588 public:
    589   ConstantDataSequential(const ConstantDataSequential &) = delete;
    590 
    591   /// Return true if a ConstantDataSequential can be formed with a vector or
    592   /// array of the specified element type.
    593   /// ConstantDataArray only works with normal float and int types that are
    594   /// stored densely in memory, not with things like i42 or x86_f80.
    595   static bool isElementTypeCompatible(Type *Ty);
    596 
    597   /// If this is a sequential container of integers (of any size), return the
    598   /// specified element in the low bits of a uint64_t.
    599   uint64_t getElementAsInteger(unsigned i) const;
    600 
    601   /// If this is a sequential container of integers (of any size), return the
    602   /// specified element as an APInt.
    603   APInt getElementAsAPInt(unsigned i) const;
    604 
    605   /// If this is a sequential container of floating point type, return the
    606   /// specified element as an APFloat.
    607   APFloat getElementAsAPFloat(unsigned i) const;
    608 
    609   /// If this is an sequential container of floats, return the specified element
    610   /// as a float.
    611   float getElementAsFloat(unsigned i) const;
    612 
    613   /// If this is an sequential container of doubles, return the specified
    614   /// element as a double.
    615   double getElementAsDouble(unsigned i) const;
    616 
    617   /// Return a Constant for a specified index's element.
    618   /// Note that this has to compute a new constant to return, so it isn't as
    619   /// efficient as getElementAsInteger/Float/Double.
    620   Constant *getElementAsConstant(unsigned i) const;
    621 
    622   /// Specialize the getType() method to always return a SequentialType, which
    623   /// reduces the amount of casting needed in parts of the compiler.
    624   inline SequentialType *getType() const {
    625     return cast<SequentialType>(Value::getType());
    626   }
    627 
    628   /// Return the element type of the array/vector.
    629   Type *getElementType() const;
    630 
    631   /// Return the number of elements in the array or vector.
    632   unsigned getNumElements() const;
    633 
    634   /// Return the size (in bytes) of each element in the array/vector.
    635   /// The size of the elements is known to be a multiple of one byte.
    636   uint64_t getElementByteSize() const;
    637 
    638   /// This method returns true if this is an array of \p CharSize integers.
    639   bool isString(unsigned CharSize = 8) const;
    640 
    641   /// This method returns true if the array "isString", ends with a null byte,
    642   /// and does not contains any other null bytes.
    643   bool isCString() const;
    644 
    645   /// If this array is isString(), then this method returns the array as a
    646   /// StringRef. Otherwise, it asserts out.
    647   StringRef getAsString() const {
    648     assert(isString() && "Not a string");
    649     return getRawDataValues();
    650   }
    651 
    652   /// If this array is isCString(), then this method returns the array (without
    653   /// the trailing null byte) as a StringRef. Otherwise, it asserts out.
    654   StringRef getAsCString() const {
    655     assert(isCString() && "Isn't a C string");
    656     StringRef Str = getAsString();
    657     return Str.substr(0, Str.size()-1);
    658   }
    659 
    660   /// Return the raw, underlying, bytes of this data. Note that this is an
    661   /// extremely tricky thing to work with, as it exposes the host endianness of
    662   /// the data elements.
    663   StringRef getRawDataValues() const;
    664 
    665   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    666   static bool classof(const Value *V) {
    667     return V->getValueID() == ConstantDataArrayVal ||
    668            V->getValueID() == ConstantDataVectorVal;
    669   }
    670 
    671 private:
    672   const char *getElementPointer(unsigned Elt) const;
    673 };
    674 
    675 //===----------------------------------------------------------------------===//
    676 /// An array constant whose element type is a simple 1/2/4/8-byte integer or
    677 /// float/double, and whose elements are just simple data values
    678 /// (i.e. ConstantInt/ConstantFP). This Constant node has no operands because it
    679 /// stores all of the elements of the constant as densely packed data, instead
    680 /// of as Value*'s.
    681 class ConstantDataArray final : public ConstantDataSequential {
    682   friend class ConstantDataSequential;
    683 
    684   explicit ConstantDataArray(Type *ty, const char *Data)
    685       : ConstantDataSequential(ty, ConstantDataArrayVal, Data) {}
    686 
    687 public:
    688   ConstantDataArray(const ConstantDataArray &) = delete;
    689 
    690   /// get() constructors - Return a constant with array type with an element
    691   /// count and element type matching the ArrayRef passed in.  Note that this
    692   /// can return a ConstantAggregateZero object.
    693   static Constant *get(LLVMContext &Context, ArrayRef<uint8_t> Elts);
    694   static Constant *get(LLVMContext &Context, ArrayRef<uint16_t> Elts);
    695   static Constant *get(LLVMContext &Context, ArrayRef<uint32_t> Elts);
    696   static Constant *get(LLVMContext &Context, ArrayRef<uint64_t> Elts);
    697   static Constant *get(LLVMContext &Context, ArrayRef<float> Elts);
    698   static Constant *get(LLVMContext &Context, ArrayRef<double> Elts);
    699 
    700   /// getFP() constructors - Return a constant with array type with an element
    701   /// count and element type of float with precision matching the number of
    702   /// bits in the ArrayRef passed in. (i.e. half for 16bits, float for 32bits,
    703   /// double for 64bits) Note that this can return a ConstantAggregateZero
    704   /// object.
    705   static Constant *getFP(LLVMContext &Context, ArrayRef<uint16_t> Elts);
    706   static Constant *getFP(LLVMContext &Context, ArrayRef<uint32_t> Elts);
    707   static Constant *getFP(LLVMContext &Context, ArrayRef<uint64_t> Elts);
    708 
    709   /// This method constructs a CDS and initializes it with a text string.
    710   /// The default behavior (AddNull==true) causes a null terminator to
    711   /// be placed at the end of the array (increasing the length of the string by
    712   /// one more than the StringRef would normally indicate.  Pass AddNull=false
    713   /// to disable this behavior.
    714   static Constant *getString(LLVMContext &Context, StringRef Initializer,
    715                              bool AddNull = true);
    716 
    717   /// Specialize the getType() method to always return an ArrayType,
    718   /// which reduces the amount of casting needed in parts of the compiler.
    719   inline ArrayType *getType() const {
    720     return cast<ArrayType>(Value::getType());
    721   }
    722 
    723   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    724   static bool classof(const Value *V) {
    725     return V->getValueID() == ConstantDataArrayVal;
    726   }
    727 };
    728 
    729 //===----------------------------------------------------------------------===//
    730 /// A vector constant whose element type is a simple 1/2/4/8-byte integer or
    731 /// float/double, and whose elements are just simple data values
    732 /// (i.e. ConstantInt/ConstantFP). This Constant node has no operands because it
    733 /// stores all of the elements of the constant as densely packed data, instead
    734 /// of as Value*'s.
    735 class ConstantDataVector final : public ConstantDataSequential {
    736   friend class ConstantDataSequential;
    737 
    738   explicit ConstantDataVector(Type *ty, const char *Data)
    739       : ConstantDataSequential(ty, ConstantDataVectorVal, Data) {}
    740 
    741 public:
    742   ConstantDataVector(const ConstantDataVector &) = delete;
    743 
    744   /// get() constructors - Return a constant with vector type with an element
    745   /// count and element type matching the ArrayRef passed in.  Note that this
    746   /// can return a ConstantAggregateZero object.
    747   static Constant *get(LLVMContext &Context, ArrayRef<uint8_t> Elts);
    748   static Constant *get(LLVMContext &Context, ArrayRef<uint16_t> Elts);
    749   static Constant *get(LLVMContext &Context, ArrayRef<uint32_t> Elts);
    750   static Constant *get(LLVMContext &Context, ArrayRef<uint64_t> Elts);
    751   static Constant *get(LLVMContext &Context, ArrayRef<float> Elts);
    752   static Constant *get(LLVMContext &Context, ArrayRef<double> Elts);
    753 
    754   /// getFP() constructors - Return a constant with vector type with an element
    755   /// count and element type of float with the precision matching the number of
    756   /// bits in the ArrayRef passed in.  (i.e. half for 16bits, float for 32bits,
    757   /// double for 64bits) Note that this can return a ConstantAggregateZero
    758   /// object.
    759   static Constant *getFP(LLVMContext &Context, ArrayRef<uint16_t> Elts);
    760   static Constant *getFP(LLVMContext &Context, ArrayRef<uint32_t> Elts);
    761   static Constant *getFP(LLVMContext &Context, ArrayRef<uint64_t> Elts);
    762 
    763   /// Return a ConstantVector with the specified constant in each element.
    764   /// The specified constant has to be a of a compatible type (i8/i16/
    765   /// i32/i64/float/double) and must be a ConstantFP or ConstantInt.
    766   static Constant *getSplat(unsigned NumElts, Constant *Elt);
    767 
    768   /// Returns true if this is a splat constant, meaning that all elements have
    769   /// the same value.
    770   bool isSplat() const;
    771 
    772   /// If this is a splat constant, meaning that all of the elements have the
    773   /// same value, return that value. Otherwise return NULL.
    774   Constant *getSplatValue() const;
    775 
    776   /// Specialize the getType() method to always return a VectorType,
    777   /// which reduces the amount of casting needed in parts of the compiler.
    778   inline VectorType *getType() const {
    779     return cast<VectorType>(Value::getType());
    780   }
    781 
    782   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    783   static bool classof(const Value *V) {
    784     return V->getValueID() == ConstantDataVectorVal;
    785   }
    786 };
    787 
    788 //===----------------------------------------------------------------------===//
    789 /// A constant token which is empty
    790 ///
    791 class ConstantTokenNone final : public ConstantData {
    792   friend class Constant;
    793 
    794   explicit ConstantTokenNone(LLVMContext &Context)
    795       : ConstantData(Type::getTokenTy(Context), ConstantTokenNoneVal) {}
    796 
    797   void destroyConstantImpl();
    798 
    799 public:
    800   ConstantTokenNone(const ConstantTokenNone &) = delete;
    801 
    802   /// Return the ConstantTokenNone.
    803   static ConstantTokenNone *get(LLVMContext &Context);
    804 
    805   /// @brief Methods to support type inquiry through isa, cast, and dyn_cast.
    806   static bool classof(const Value *V) {
    807     return V->getValueID() == ConstantTokenNoneVal;
    808   }
    809 };
    810 
    811 /// The address of a basic block.
    812 ///
    813 class BlockAddress final : public Constant {
    814   friend class Constant;
    815 
    816   BlockAddress(Function *F, BasicBlock *BB);
    817 
    818   void *operator new(size_t s) { return User::operator new(s, 2); }
    819 
    820   void destroyConstantImpl();
    821   Value *handleOperandChangeImpl(Value *From, Value *To);
    822 
    823 public:
    824   /// Return a BlockAddress for the specified function and basic block.
    825   static BlockAddress *get(Function *F, BasicBlock *BB);
    826 
    827   /// Return a BlockAddress for the specified basic block.  The basic
    828   /// block must be embedded into a function.
    829   static BlockAddress *get(BasicBlock *BB);
    830 
    831   /// Lookup an existing \c BlockAddress constant for the given BasicBlock.
    832   ///
    833   /// \returns 0 if \c !BB->hasAddressTaken(), otherwise the \c BlockAddress.
    834   static BlockAddress *lookup(const BasicBlock *BB);
    835 
    836   /// Transparently provide more efficient getOperand methods.
    837   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
    838 
    839   Function *getFunction() const { return (Function*)Op<0>().get(); }
    840   BasicBlock *getBasicBlock() const { return (BasicBlock*)Op<1>().get(); }
    841 
    842   /// Methods for support type inquiry through isa, cast, and dyn_cast:
    843   static bool classof(const Value *V) {
    844     return V->getValueID() == BlockAddressVal;
    845   }
    846 };
    847 
    848 template <>
    849 struct OperandTraits<BlockAddress> :
    850   public FixedNumOperandTraits<BlockAddress, 2> {
    851 };
    852 
    853 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(BlockAddress, Value)
    854 
    855 //===----------------------------------------------------------------------===//
    856 /// A constant value that is initialized with an expression using
    857 /// other constant values.
    858 ///
    859 /// This class uses the standard Instruction opcodes to define the various
    860 /// constant expressions.  The Opcode field for the ConstantExpr class is
    861 /// maintained in the Value::SubclassData field.
    862 class ConstantExpr : public Constant {
    863   friend struct ConstantExprKeyType;
    864   friend class Constant;
    865 
    866   void destroyConstantImpl();
    867   Value *handleOperandChangeImpl(Value *From, Value *To);
    868 
    869 protected:
    870   ConstantExpr(Type *ty, unsigned Opcode, Use *Ops, unsigned NumOps)
    871       : Constant(ty, ConstantExprVal, Ops, NumOps) {
    872     // Operation type (an Instruction opcode) is stored as the SubclassData.
    873     setValueSubclassData(Opcode);
    874   }
    875 
    876 public:
    877   // Static methods to construct a ConstantExpr of different kinds.  Note that
    878   // these methods may return a object that is not an instance of the
    879   // ConstantExpr class, because they will attempt to fold the constant
    880   // expression into something simpler if possible.
    881 
    882   /// getAlignOf constant expr - computes the alignment of a type in a target
    883   /// independent way (Note: the return type is an i64).
    884   static Constant *getAlignOf(Type *Ty);
    885 
    886   /// getSizeOf constant expr - computes the (alloc) size of a type (in
    887   /// address-units, not bits) in a target independent way (Note: the return
    888   /// type is an i64).
    889   ///
    890   static Constant *getSizeOf(Type *Ty);
    891 
    892   /// getOffsetOf constant expr - computes the offset of a struct field in a
    893   /// target independent way (Note: the return type is an i64).
    894   ///
    895   static Constant *getOffsetOf(StructType *STy, unsigned FieldNo);
    896 
    897   /// getOffsetOf constant expr - This is a generalized form of getOffsetOf,
    898   /// which supports any aggregate type, and any Constant index.
    899   ///
    900   static Constant *getOffsetOf(Type *Ty, Constant *FieldNo);
    901 
    902   static Constant *getNeg(Constant *C, bool HasNUW = false, bool HasNSW =false);
    903   static Constant *getFNeg(Constant *C);
    904   static Constant *getNot(Constant *C);
    905   static Constant *getAdd(Constant *C1, Constant *C2,
    906                           bool HasNUW = false, bool HasNSW = false);
    907   static Constant *getFAdd(Constant *C1, Constant *C2);
    908   static Constant *getSub(Constant *C1, Constant *C2,
    909                           bool HasNUW = false, bool HasNSW = false);
    910   static Constant *getFSub(Constant *C1, Constant *C2);
    911   static Constant *getMul(Constant *C1, Constant *C2,
    912                           bool HasNUW = false, bool HasNSW = false);
    913   static Constant *getFMul(Constant *C1, Constant *C2);
    914   static Constant *getUDiv(Constant *C1, Constant *C2, bool isExact = false);
    915   static Constant *getSDiv(Constant *C1, Constant *C2, bool isExact = false);
    916   static Constant *getFDiv(Constant *C1, Constant *C2);
    917   static Constant *getURem(Constant *C1, Constant *C2);
    918   static Constant *getSRem(Constant *C1, Constant *C2);
    919   static Constant *getFRem(Constant *C1, Constant *C2);
    920   static Constant *getAnd(Constant *C1, Constant *C2);
    921   static Constant *getOr(Constant *C1, Constant *C2);
    922   static Constant *getXor(Constant *C1, Constant *C2);
    923   static Constant *getShl(Constant *C1, Constant *C2,
    924                           bool HasNUW = false, bool HasNSW = false);
    925   static Constant *getLShr(Constant *C1, Constant *C2, bool isExact = false);
    926   static Constant *getAShr(Constant *C1, Constant *C2, bool isExact = false);
    927   static Constant *getTrunc(Constant *C, Type *Ty, bool OnlyIfReduced = false);
    928   static Constant *getSExt(Constant *C, Type *Ty, bool OnlyIfReduced = false);
    929   static Constant *getZExt(Constant *C, Type *Ty, bool OnlyIfReduced = false);
    930   static Constant *getFPTrunc(Constant *C, Type *Ty,
    931                               bool OnlyIfReduced = false);
    932   static Constant *getFPExtend(Constant *C, Type *Ty,
    933                                bool OnlyIfReduced = false);
    934   static Constant *getUIToFP(Constant *C, Type *Ty, bool OnlyIfReduced = false);
    935   static Constant *getSIToFP(Constant *C, Type *Ty, bool OnlyIfReduced = false);
    936   static Constant *getFPToUI(Constant *C, Type *Ty, bool OnlyIfReduced = false);
    937   static Constant *getFPToSI(Constant *C, Type *Ty, bool OnlyIfReduced = false);
    938   static Constant *getPtrToInt(Constant *C, Type *Ty,
    939                                bool OnlyIfReduced = false);
    940   static Constant *getIntToPtr(Constant *C, Type *Ty,
    941                                bool OnlyIfReduced = false);
    942   static Constant *getBitCast(Constant *C, Type *Ty,
    943                               bool OnlyIfReduced = false);
    944   static Constant *getAddrSpaceCast(Constant *C, Type *Ty,
    945                                     bool OnlyIfReduced = false);
    946 
    947   static Constant *getNSWNeg(Constant *C) { return getNeg(C, false, true); }
    948   static Constant *getNUWNeg(Constant *C) { return getNeg(C, true, false); }
    949 
    950   static Constant *getNSWAdd(Constant *C1, Constant *C2) {
    951     return getAdd(C1, C2, false, true);
    952   }
    953 
    954   static Constant *getNUWAdd(Constant *C1, Constant *C2) {
    955     return getAdd(C1, C2, true, false);
    956   }
    957 
    958   static Constant *getNSWSub(Constant *C1, Constant *C2) {
    959     return getSub(C1, C2, false, true);
    960   }
    961 
    962   static Constant *getNUWSub(Constant *C1, Constant *C2) {
    963     return getSub(C1, C2, true, false);
    964   }
    965 
    966   static Constant *getNSWMul(Constant *C1, Constant *C2) {
    967     return getMul(C1, C2, false, true);
    968   }
    969 
    970   static Constant *getNUWMul(Constant *C1, Constant *C2) {
    971     return getMul(C1, C2, true, false);
    972   }
    973 
    974   static Constant *getNSWShl(Constant *C1, Constant *C2) {
    975     return getShl(C1, C2, false, true);
    976   }
    977 
    978   static Constant *getNUWShl(Constant *C1, Constant *C2) {
    979     return getShl(C1, C2, true, false);
    980   }
    981 
    982   static Constant *getExactSDiv(Constant *C1, Constant *C2) {
    983     return getSDiv(C1, C2, true);
    984   }
    985 
    986   static Constant *getExactUDiv(Constant *C1, Constant *C2) {
    987     return getUDiv(C1, C2, true);
    988   }
    989 
    990   static Constant *getExactAShr(Constant *C1, Constant *C2) {
    991     return getAShr(C1, C2, true);
    992   }
    993 
    994   static Constant *getExactLShr(Constant *C1, Constant *C2) {
    995     return getLShr(C1, C2, true);
    996   }
    997 
    998   /// Return the identity for the given binary operation,
    999   /// i.e. a constant C such that X op C = X and C op X = X for every X.  It
   1000   /// returns null if the operator doesn't have an identity.
   1001   static Constant *getBinOpIdentity(unsigned Opcode, Type *Ty);
   1002 
   1003   /// Return the absorbing element for the given binary
   1004   /// operation, i.e. a constant C such that X op C = C and C op X = C for
   1005   /// every X.  For example, this returns zero for integer multiplication.
   1006   /// It returns null if the operator doesn't have an absorbing element.
   1007   static Constant *getBinOpAbsorber(unsigned Opcode, Type *Ty);
   1008 
   1009   /// Transparently provide more efficient getOperand methods.
   1010   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Constant);
   1011 
   1012   /// \brief Convenience function for getting a Cast operation.
   1013   ///
   1014   /// \param ops The opcode for the conversion
   1015   /// \param C  The constant to be converted
   1016   /// \param Ty The type to which the constant is converted
   1017   /// \param OnlyIfReduced see \a getWithOperands() docs.
   1018   static Constant *getCast(unsigned ops, Constant *C, Type *Ty,
   1019                            bool OnlyIfReduced = false);
   1020 
   1021   // @brief Create a ZExt or BitCast cast constant expression
   1022   static Constant *getZExtOrBitCast(
   1023     Constant *C,   ///< The constant to zext or bitcast
   1024     Type *Ty ///< The type to zext or bitcast C to
   1025   );
   1026 
   1027   // @brief Create a SExt or BitCast cast constant expression
   1028   static Constant *getSExtOrBitCast(
   1029     Constant *C,   ///< The constant to sext or bitcast
   1030     Type *Ty ///< The type to sext or bitcast C to
   1031   );
   1032 
   1033   // @brief Create a Trunc or BitCast cast constant expression
   1034   static Constant *getTruncOrBitCast(
   1035     Constant *C,   ///< The constant to trunc or bitcast
   1036     Type *Ty ///< The type to trunc or bitcast C to
   1037   );
   1038 
   1039   /// @brief Create a BitCast, AddrSpaceCast, or a PtrToInt cast constant
   1040   /// expression.
   1041   static Constant *getPointerCast(
   1042     Constant *C,   ///< The pointer value to be casted (operand 0)
   1043     Type *Ty ///< The type to which cast should be made
   1044   );
   1045 
   1046   /// @brief Create a BitCast or AddrSpaceCast for a pointer type depending on
   1047   /// the address space.
   1048   static Constant *getPointerBitCastOrAddrSpaceCast(
   1049     Constant *C,   ///< The constant to addrspacecast or bitcast
   1050     Type *Ty ///< The type to bitcast or addrspacecast C to
   1051   );
   1052 
   1053   /// @brief Create a ZExt, Bitcast or Trunc for integer -> integer casts
   1054   static Constant *getIntegerCast(
   1055     Constant *C,    ///< The integer constant to be casted
   1056     Type *Ty, ///< The integer type to cast to
   1057     bool isSigned   ///< Whether C should be treated as signed or not
   1058   );
   1059 
   1060   /// @brief Create a FPExt, Bitcast or FPTrunc for fp -> fp casts
   1061   static Constant *getFPCast(
   1062     Constant *C,    ///< The integer constant to be casted
   1063     Type *Ty ///< The integer type to cast to
   1064   );
   1065 
   1066   /// @brief Return true if this is a convert constant expression
   1067   bool isCast() const;
   1068 
   1069   /// @brief Return true if this is a compare constant expression
   1070   bool isCompare() const;
   1071 
   1072   /// @brief Return true if this is an insertvalue or extractvalue expression,
   1073   /// and the getIndices() method may be used.
   1074   bool hasIndices() const;
   1075 
   1076   /// @brief Return true if this is a getelementptr expression and all
   1077   /// the index operands are compile-time known integers within the
   1078   /// corresponding notional static array extents. Note that this is
   1079   /// not equivalant to, a subset of, or a superset of the "inbounds"
   1080   /// property.
   1081   bool isGEPWithNoNotionalOverIndexing() const;
   1082 
   1083   /// Select constant expr
   1084   ///
   1085   /// \param OnlyIfReducedTy see \a getWithOperands() docs.
   1086   static Constant *getSelect(Constant *C, Constant *V1, Constant *V2,
   1087                              Type *OnlyIfReducedTy = nullptr);
   1088 
   1089   /// get - Return a binary or shift operator constant expression,
   1090   /// folding if possible.
   1091   ///
   1092   /// \param OnlyIfReducedTy see \a getWithOperands() docs.
   1093   static Constant *get(unsigned Opcode, Constant *C1, Constant *C2,
   1094                        unsigned Flags = 0, Type *OnlyIfReducedTy = nullptr);
   1095 
   1096   /// \brief Return an ICmp or FCmp comparison operator constant expression.
   1097   ///
   1098   /// \param OnlyIfReduced see \a getWithOperands() docs.
   1099   static Constant *getCompare(unsigned short pred, Constant *C1, Constant *C2,
   1100                               bool OnlyIfReduced = false);
   1101 
   1102   /// get* - Return some common constants without having to
   1103   /// specify the full Instruction::OPCODE identifier.
   1104   ///
   1105   static Constant *getICmp(unsigned short pred, Constant *LHS, Constant *RHS,
   1106                            bool OnlyIfReduced = false);
   1107   static Constant *getFCmp(unsigned short pred, Constant *LHS, Constant *RHS,
   1108                            bool OnlyIfReduced = false);
   1109 
   1110   /// Getelementptr form.  Value* is only accepted for convenience;
   1111   /// all elements must be Constants.
   1112   ///
   1113   /// \param InRangeIndex the inrange index if present or None.
   1114   /// \param OnlyIfReducedTy see \a getWithOperands() docs.
   1115   static Constant *getGetElementPtr(Type *Ty, Constant *C,
   1116                                     ArrayRef<Constant *> IdxList,
   1117                                     bool InBounds = false,
   1118                                     Optional<unsigned> InRangeIndex = None,
   1119                                     Type *OnlyIfReducedTy = nullptr) {
   1120     return getGetElementPtr(
   1121         Ty, C, makeArrayRef((Value * const *)IdxList.data(), IdxList.size()),
   1122         InBounds, InRangeIndex, OnlyIfReducedTy);
   1123   }
   1124   static Constant *getGetElementPtr(Type *Ty, Constant *C, Constant *Idx,
   1125                                     bool InBounds = false,
   1126                                     Optional<unsigned> InRangeIndex = None,
   1127                                     Type *OnlyIfReducedTy = nullptr) {
   1128     // This form of the function only exists to avoid ambiguous overload
   1129     // warnings about whether to convert Idx to ArrayRef<Constant *> or
   1130     // ArrayRef<Value *>.
   1131     return getGetElementPtr(Ty, C, cast<Value>(Idx), InBounds, InRangeIndex,
   1132                             OnlyIfReducedTy);
   1133   }
   1134   static Constant *getGetElementPtr(Type *Ty, Constant *C,
   1135                                     ArrayRef<Value *> IdxList,
   1136                                     bool InBounds = false,
   1137                                     Optional<unsigned> InRangeIndex = None,
   1138                                     Type *OnlyIfReducedTy = nullptr);
   1139 
   1140   /// Create an "inbounds" getelementptr. See the documentation for the
   1141   /// "inbounds" flag in LangRef.html for details.
   1142   static Constant *getInBoundsGetElementPtr(Type *Ty, Constant *C,
   1143                                             ArrayRef<Constant *> IdxList) {
   1144     return getGetElementPtr(Ty, C, IdxList, true);
   1145   }
   1146   static Constant *getInBoundsGetElementPtr(Type *Ty, Constant *C,
   1147                                             Constant *Idx) {
   1148     // This form of the function only exists to avoid ambiguous overload
   1149     // warnings about whether to convert Idx to ArrayRef<Constant *> or
   1150     // ArrayRef<Value *>.
   1151     return getGetElementPtr(Ty, C, Idx, true);
   1152   }
   1153   static Constant *getInBoundsGetElementPtr(Type *Ty, Constant *C,
   1154                                             ArrayRef<Value *> IdxList) {
   1155     return getGetElementPtr(Ty, C, IdxList, true);
   1156   }
   1157 
   1158   static Constant *getExtractElement(Constant *Vec, Constant *Idx,
   1159                                      Type *OnlyIfReducedTy = nullptr);
   1160   static Constant *getInsertElement(Constant *Vec, Constant *Elt, Constant *Idx,
   1161                                     Type *OnlyIfReducedTy = nullptr);
   1162   static Constant *getShuffleVector(Constant *V1, Constant *V2, Constant *Mask,
   1163                                     Type *OnlyIfReducedTy = nullptr);
   1164   static Constant *getExtractValue(Constant *Agg, ArrayRef<unsigned> Idxs,
   1165                                    Type *OnlyIfReducedTy = nullptr);
   1166   static Constant *getInsertValue(Constant *Agg, Constant *Val,
   1167                                   ArrayRef<unsigned> Idxs,
   1168                                   Type *OnlyIfReducedTy = nullptr);
   1169 
   1170   /// Return the opcode at the root of this constant expression
   1171   unsigned getOpcode() const { return getSubclassDataFromValue(); }
   1172 
   1173   /// Return the ICMP or FCMP predicate value. Assert if this is not an ICMP or
   1174   /// FCMP constant expression.
   1175   unsigned getPredicate() const;
   1176 
   1177   /// Assert that this is an insertvalue or exactvalue
   1178   /// expression and return the list of indices.
   1179   ArrayRef<unsigned> getIndices() const;
   1180 
   1181   /// Return a string representation for an opcode.
   1182   const char *getOpcodeName() const;
   1183 
   1184   /// Return a constant expression identical to this one, but with the specified
   1185   /// operand set to the specified value.
   1186   Constant *getWithOperandReplaced(unsigned OpNo, Constant *Op) const;
   1187 
   1188   /// This returns the current constant expression with the operands replaced
   1189   /// with the specified values. The specified array must have the same number
   1190   /// of operands as our current one.
   1191   Constant *getWithOperands(ArrayRef<Constant*> Ops) const {
   1192     return getWithOperands(Ops, getType());
   1193   }
   1194 
   1195   /// Get the current expression with the operands replaced.
   1196   ///
   1197   /// Return the current constant expression with the operands replaced with \c
   1198   /// Ops and the type with \c Ty.  The new operands must have the same number
   1199   /// as the current ones.
   1200   ///
   1201   /// If \c OnlyIfReduced is \c true, nullptr will be returned unless something
   1202   /// gets constant-folded, the type changes, or the expression is otherwise
   1203   /// canonicalized.  This parameter should almost always be \c false.
   1204   Constant *getWithOperands(ArrayRef<Constant *> Ops, Type *Ty,
   1205                             bool OnlyIfReduced = false,
   1206                             Type *SrcTy = nullptr) const;
   1207 
   1208   /// Returns an Instruction which implements the same operation as this
   1209   /// ConstantExpr. The instruction is not linked to any basic block.
   1210   ///
   1211   /// A better approach to this could be to have a constructor for Instruction
   1212   /// which would take a ConstantExpr parameter, but that would have spread
   1213   /// implementation details of ConstantExpr outside of Constants.cpp, which
   1214   /// would make it harder to remove ConstantExprs altogether.
   1215   Instruction *getAsInstruction();
   1216 
   1217   /// Methods for support type inquiry through isa, cast, and dyn_cast:
   1218   static bool classof(const Value *V) {
   1219     return V->getValueID() == ConstantExprVal;
   1220   }
   1221 
   1222 private:
   1223   // Shadow Value::setValueSubclassData with a private forwarding method so that
   1224   // subclasses cannot accidentally use it.
   1225   void setValueSubclassData(unsigned short D) {
   1226     Value::setValueSubclassData(D);
   1227   }
   1228 };
   1229 
   1230 template <>
   1231 struct OperandTraits<ConstantExpr> :
   1232   public VariadicOperandTraits<ConstantExpr, 1> {
   1233 };
   1234 
   1235 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantExpr, Constant)
   1236 
   1237 //===----------------------------------------------------------------------===//
   1238 /// 'undef' values are things that do not have specified contents.
   1239 /// These are used for a variety of purposes, including global variable
   1240 /// initializers and operands to instructions.  'undef' values can occur with
   1241 /// any first-class type.
   1242 ///
   1243 /// Undef values aren't exactly constants; if they have multiple uses, they
   1244 /// can appear to have different bit patterns at each use. See
   1245 /// LangRef.html#undefvalues for details.
   1246 ///
   1247 class UndefValue final : public ConstantData {
   1248   friend class Constant;
   1249 
   1250   explicit UndefValue(Type *T) : ConstantData(T, UndefValueVal) {}
   1251 
   1252   void destroyConstantImpl();
   1253 
   1254 public:
   1255   UndefValue(const UndefValue &) = delete;
   1256 
   1257   /// Static factory methods - Return an 'undef' object of the specified type.
   1258   static UndefValue *get(Type *T);
   1259 
   1260   /// If this Undef has array or vector type, return a undef with the right
   1261   /// element type.
   1262   UndefValue *getSequentialElement() const;
   1263 
   1264   /// If this undef has struct type, return a undef with the right element type
   1265   /// for the specified element.
   1266   UndefValue *getStructElement(unsigned Elt) const;
   1267 
   1268   /// Return an undef of the right value for the specified GEP index if we can,
   1269   /// otherwise return null (e.g. if C is a ConstantExpr).
   1270   UndefValue *getElementValue(Constant *C) const;
   1271 
   1272   /// Return an undef of the right value for the specified GEP index.
   1273   UndefValue *getElementValue(unsigned Idx) const;
   1274 
   1275   /// Return the number of elements in the array, vector, or struct.
   1276   unsigned getNumElements() const;
   1277 
   1278   /// Methods for support type inquiry through isa, cast, and dyn_cast:
   1279   static bool classof(const Value *V) {
   1280     return V->getValueID() == UndefValueVal;
   1281   }
   1282 };
   1283 
   1284 } // end namespace llvm
   1285 
   1286 #endif // LLVM_IR_CONSTANTS_H
   1287