1 //===-- llvm/Constants.h - Constant class subclass definitions --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 /// @file This file contains the declarations for the subclasses of Constant,
11 /// which represent the different flavors of constant values that live in LLVM.
12 /// Note that Constants are immutable (once created they never change) and are
13 /// fully shared by structural equivalence. This means that two structurally
14 /// equivalent constants will always have the same address. Constant's are
15 /// created on demand as needed and never deleted: thus clients don't have to
16 /// worry about the lifetime of the objects.
18 //===----------------------------------------------------------------------===//
20 #ifndef LLVM_CONSTANTS_H
21 #define LLVM_CONSTANTS_H
23 #include "llvm/Constant.h"
24 #include "llvm/Type.h"
25 #include "llvm/ADT/APInt.h"
34 template<class ConstantClass, class TypeClass, class ValType>
35 struct ConstantCreator;
36 template<class ConstantClass, class TypeClass>
37 struct ConvertConstantType;
39 //===----------------------------------------------------------------------===//
40 /// This is the shared class of boolean and integer constants. This class
41 /// represents both boolean and integral constants.
42 /// @brief Class for constant integers.
43 class ConstantInt : public Constant {
44 static ConstantInt *TheTrueVal, *TheFalseVal;
45 ConstantInt(const ConstantInt &); // DO NOT IMPLEMENT
46 ConstantInt(const IntegerType *Ty, const APInt& V);
49 /// Return the constant as an APInt value reference. This allows clients to
50 /// obtain a copy of the value, with all its precision in tact.
51 /// @brief Return the constant's value.
52 inline const APInt& getValue() const {
56 /// Return the constant as a 64-bit unsigned integer value after it
57 /// has been zero extended as appropriate for the type of this constant. Note
58 /// that this method can assert if the value does not fit in 64 bits.
60 /// @brief Return the zero extended value.
61 inline uint64_t getZExtValue() const {
62 return Val.getZExtValue();
65 /// Return the constant as a 64-bit integer value after it has been sign
66 /// sign extended as appropriate for the type of this constant. Note that
67 /// this method can assert if the value does not fit in 64 bits.
69 /// @brief Return the sign extended value.
70 inline int64_t getSExtValue() const {
71 return Val.getSExtValue();
74 /// A helper method that can be used to determine if the constant contained
75 /// within is equal to a constant. This only works for very small values,
76 /// because this is all that can be represented with all types.
77 /// @brief Determine if this constant's value is same as an unsigned char.
78 bool equalsInt(uint64_t V) const {
82 /// getTrue/getFalse - Return the singleton true/false values.
83 static inline ConstantInt *getTrue() {
84 if (TheTrueVal) return TheTrueVal;
85 return CreateTrueFalseVals(true);
87 static inline ConstantInt *getFalse() {
88 if (TheFalseVal) return TheFalseVal;
89 return CreateTrueFalseVals(false);
92 /// Return a ConstantInt with the specified value for the specified type. The
93 /// value V will be canonicalized to a uint64_t but accessing it with either
94 /// getSExtValue() or getZExtValue() (ConstantInt) will yield the correct
95 /// sized/signed value for the type Ty.
96 /// @brief Get a ConstantInt for a specific value.
97 static ConstantInt *get(const Type *Ty, int64_t V);
98 static ConstantInt *get(const Type *Ty, const APInt& V);
100 /// Return a ConstantInt with the specified value and an implied Type. The
101 /// type is the integer type that corresponds to the bit width of the value.
102 static ConstantInt *get(const APInt &V);
104 /// getType - Specialize the getType() method to always return an IntegerType,
105 /// which reduces the amount of casting needed in parts of the compiler.
107 inline const IntegerType *getType() const {
108 return reinterpret_cast<const IntegerType*>(Value::getType());
111 /// This static method returns true if the type Ty is big enough to
112 /// represent the value V. This can be used to avoid having the get method
113 /// assert when V is larger than Ty can represent. Note that there are two
114 /// versions of this method, one for unsigned and one for signed integers.
115 /// Although ConstantInt canonicalizes everything to an unsigned integer,
116 /// the signed version avoids callers having to convert a signed quantity
117 /// to the appropriate unsigned type before calling the method.
118 /// @returns true if V is a valid value for type Ty
119 /// @brief Determine if the value is in range for the given type.
120 static bool isValueValidForType(const Type *Ty, uint64_t V);
121 static bool isValueValidForType(const Type *Ty, int64_t V);
123 /// This function will return true iff this constant represents the "null"
124 /// value that would be returned by the getNullValue method.
125 /// @returns true if this is the null integer value.
126 /// @brief Determine if the value is null.
127 virtual bool isNullValue() const {
131 /// This function will return true iff every bit in this constant is set
133 /// @returns true iff this constant's bits are all set to true.
134 /// @brief Determine if the value is all ones.
135 bool isAllOnesValue() const {
136 return Val.isAllOnesValue();
139 /// This function will return true iff this constant represents the largest
140 /// value that may be represented by the constant's type.
141 /// @returns true iff this is the largest value that may be represented
143 /// @brief Determine if the value is maximal.
144 bool isMaxValue(bool isSigned) const {
146 return Val.isMaxSignedValue();
148 return Val.isMaxValue();
151 /// This function will return true iff this constant represents the smallest
152 /// value that may be represented by this constant's type.
153 /// @returns true if this is the smallest value that may be represented by
155 /// @brief Determine if the value is minimal.
156 bool isMinValue(bool isSigned) const {
158 return Val.isMinSignedValue();
160 return Val.isMinValue();
163 /// @returns the value for an integer constant of the given type that has all
164 /// its bits set to true.
165 /// @brief Get the all ones value
166 static ConstantInt *getAllOnesValue(const Type *Ty);
168 /// @brief Methods to support type inquiry through isa, cast, and dyn_cast.
169 static inline bool classof(const ConstantInt *) { return true; }
170 static bool classof(const Value *V) {
171 return V->getValueType() == ConstantIntVal;
173 static void ResetTrueFalse() { TheTrueVal = TheFalseVal = 0; }
175 static ConstantInt *CreateTrueFalseVals(bool WhichOne);
179 //===----------------------------------------------------------------------===//
180 /// ConstantFP - Floating Point Values [float, double]
182 class ConstantFP : public Constant {
184 ConstantFP(const ConstantFP &); // DO NOT IMPLEMENT
186 ConstantFP(const Type *Ty, double V);
188 /// get() - Static factory methods - Return objects of the specified value
189 static ConstantFP *get(const Type *Ty, double V);
191 /// isValueValidForType - return true if Ty is big enough to represent V.
192 static bool isValueValidForType(const Type *Ty, double V);
193 inline double getValue() const { return Val; }
195 /// isNullValue - Return true if this is the value that would be returned by
196 /// getNullValue. Don't depend on == for doubles to tell us it's zero, it
197 /// considers -0.0 to be null as well as 0.0. :(
198 virtual bool isNullValue() const;
200 /// isExactlyValue - We don't rely on operator== working on double values, as
201 /// it returns true for things that are clearly not equal, like -0.0 and 0.0.
202 /// As such, this method can be used to do an exact bit-for-bit comparison of
203 /// two floating point values.
204 bool isExactlyValue(double V) const;
206 /// Methods for support type inquiry through isa, cast, and dyn_cast:
207 static inline bool classof(const ConstantFP *) { return true; }
208 static bool classof(const Value *V) {
209 return V->getValueType() == ConstantFPVal;
213 //===----------------------------------------------------------------------===//
214 /// ConstantAggregateZero - All zero aggregate value
216 class ConstantAggregateZero : public Constant {
217 friend struct ConstantCreator<ConstantAggregateZero, Type, char>;
218 ConstantAggregateZero(const ConstantAggregateZero &); // DO NOT IMPLEMENT
220 ConstantAggregateZero(const Type *Ty)
221 : Constant(Ty, ConstantAggregateZeroVal, 0, 0) {}
223 /// get() - static factory method for creating a null aggregate. It is
224 /// illegal to call this method with a non-aggregate type.
225 static Constant *get(const Type *Ty);
227 /// isNullValue - Return true if this is the value that would be returned by
229 virtual bool isNullValue() const { return true; }
231 virtual void destroyConstant();
233 /// Methods for support type inquiry through isa, cast, and dyn_cast:
235 static bool classof(const ConstantAggregateZero *) { return true; }
236 static bool classof(const Value *V) {
237 return V->getValueType() == ConstantAggregateZeroVal;
242 //===----------------------------------------------------------------------===//
243 /// ConstantArray - Constant Array Declarations
245 class ConstantArray : public Constant {
246 friend struct ConstantCreator<ConstantArray, ArrayType,
247 std::vector<Constant*> >;
248 ConstantArray(const ConstantArray &); // DO NOT IMPLEMENT
250 ConstantArray(const ArrayType *T, const std::vector<Constant*> &Val);
253 /// get() - Static factory methods - Return objects of the specified value
254 static Constant *get(const ArrayType *T, const std::vector<Constant*> &);
255 static Constant *get(const ArrayType *T,
256 Constant*const*Vals, unsigned NumVals) {
257 // FIXME: make this the primary ctor method.
258 return get(T, std::vector<Constant*>(Vals, Vals+NumVals));
261 /// This method constructs a ConstantArray and initializes it with a text
262 /// string. The default behavior (AddNull==true) causes a null terminator to
263 /// be placed at the end of the array. This effectively increases the length
264 /// of the array by one (you've been warned). However, in some situations
265 /// this is not desired so if AddNull==false then the string is copied without
266 /// null termination.
267 static Constant *get(const std::string &Initializer, bool AddNull = true);
269 /// getType - Specialize the getType() method to always return an ArrayType,
270 /// which reduces the amount of casting needed in parts of the compiler.
272 inline const ArrayType *getType() const {
273 return reinterpret_cast<const ArrayType*>(Value::getType());
276 /// isString - This method returns true if the array is an array of sbyte or
277 /// ubyte, and if the elements of the array are all ConstantInt's.
278 bool isString() const;
280 /// isCString - This method returns true if the array is a string (see
281 /// isString) and it ends in a null byte \0 and does not contains any other
282 /// null bytes except its terminator.
283 bool isCString() const;
285 /// getAsString - If this array is isString(), then this method converts the
286 /// array to an std::string and returns it. Otherwise, it asserts out.
288 std::string getAsString() const;
290 /// isNullValue - Return true if this is the value that would be returned by
291 /// getNullValue. This always returns false because zero arrays are always
292 /// created as ConstantAggregateZero objects.
293 virtual bool isNullValue() const { return false; }
295 virtual void destroyConstant();
296 virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U);
298 /// Methods for support type inquiry through isa, cast, and dyn_cast:
299 static inline bool classof(const ConstantArray *) { return true; }
300 static bool classof(const Value *V) {
301 return V->getValueType() == ConstantArrayVal;
306 //===----------------------------------------------------------------------===//
307 // ConstantStruct - Constant Struct Declarations
309 class ConstantStruct : public Constant {
310 friend struct ConstantCreator<ConstantStruct, StructType,
311 std::vector<Constant*> >;
312 ConstantStruct(const ConstantStruct &); // DO NOT IMPLEMENT
314 ConstantStruct(const StructType *T, const std::vector<Constant*> &Val);
317 /// get() - Static factory methods - Return objects of the specified value
319 static Constant *get(const StructType *T, const std::vector<Constant*> &V);
320 static Constant *get(const std::vector<Constant*> &V, bool Packed = false);
321 static Constant *get(Constant*const* Vals, unsigned NumVals,
322 bool Packed = false) {
323 // FIXME: make this the primary ctor method.
324 return get(std::vector<Constant*>(Vals, Vals+NumVals), Packed);
327 /// getType() specialization - Reduce amount of casting...
329 inline const StructType *getType() const {
330 return reinterpret_cast<const StructType*>(Value::getType());
333 /// isNullValue - Return true if this is the value that would be returned by
334 /// getNullValue. This always returns false because zero structs are always
335 /// created as ConstantAggregateZero objects.
336 virtual bool isNullValue() const {
340 virtual void destroyConstant();
341 virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U);
343 /// Methods for support type inquiry through isa, cast, and dyn_cast:
344 static inline bool classof(const ConstantStruct *) { return true; }
345 static bool classof(const Value *V) {
346 return V->getValueType() == ConstantStructVal;
350 //===----------------------------------------------------------------------===//
351 /// ConstantVector - Constant Vector Declarations
353 class ConstantVector : public Constant {
354 friend struct ConstantCreator<ConstantVector, VectorType,
355 std::vector<Constant*> >;
356 ConstantVector(const ConstantVector &); // DO NOT IMPLEMENT
358 ConstantVector(const VectorType *T, const std::vector<Constant*> &Val);
361 /// get() - Static factory methods - Return objects of the specified value
362 static Constant *get(const VectorType *T, const std::vector<Constant*> &);
363 static Constant *get(const std::vector<Constant*> &V);
364 static Constant *get(Constant*const* Vals, unsigned NumVals) {
365 // FIXME: make this the primary ctor method.
366 return get(std::vector<Constant*>(Vals, Vals+NumVals));
369 /// getType - Specialize the getType() method to always return an VectorType,
370 /// which reduces the amount of casting needed in parts of the compiler.
372 inline const VectorType *getType() const {
373 return reinterpret_cast<const VectorType*>(Value::getType());
376 /// @returns the value for an packed integer constant of the given type that
377 /// has all its bits set to true.
378 /// @brief Get the all ones value
379 static ConstantVector *getAllOnesValue(const VectorType *Ty);
381 /// isNullValue - Return true if this is the value that would be returned by
382 /// getNullValue. This always returns false because zero arrays are always
383 /// created as ConstantAggregateZero objects.
384 virtual bool isNullValue() const { return false; }
386 /// This function will return true iff every element in this packed constant
387 /// is set to all ones.
388 /// @returns true iff this constant's emements are all set to all ones.
389 /// @brief Determine if the value is all ones.
390 bool isAllOnesValue() const;
392 virtual void destroyConstant();
393 virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U);
395 /// Methods for support type inquiry through isa, cast, and dyn_cast:
396 static inline bool classof(const ConstantVector *) { return true; }
397 static bool classof(const Value *V) {
398 return V->getValueType() == ConstantVectorVal;
402 //===----------------------------------------------------------------------===//
403 /// ConstantPointerNull - a constant pointer value that points to null
405 class ConstantPointerNull : public Constant {
406 friend struct ConstantCreator<ConstantPointerNull, PointerType, char>;
407 ConstantPointerNull(const ConstantPointerNull &); // DO NOT IMPLEMENT
409 ConstantPointerNull(const PointerType *T)
410 : Constant(reinterpret_cast<const Type*>(T),
411 Value::ConstantPointerNullVal, 0, 0) {}
415 /// get() - Static factory methods - Return objects of the specified value
416 static ConstantPointerNull *get(const PointerType *T);
418 /// isNullValue - Return true if this is the value that would be returned by
420 virtual bool isNullValue() const { return true; }
422 virtual void destroyConstant();
424 /// getType - Specialize the getType() method to always return an PointerType,
425 /// which reduces the amount of casting needed in parts of the compiler.
427 inline const PointerType *getType() const {
428 return reinterpret_cast<const PointerType*>(Value::getType());
431 /// Methods for support type inquiry through isa, cast, and dyn_cast:
432 static inline bool classof(const ConstantPointerNull *) { return true; }
433 static bool classof(const Value *V) {
434 return V->getValueType() == ConstantPointerNullVal;
439 /// ConstantExpr - a constant value that is initialized with an expression using
440 /// other constant values.
442 /// This class uses the standard Instruction opcodes to define the various
443 /// constant expressions. The Opcode field for the ConstantExpr class is
444 /// maintained in the Value::SubclassData field.
445 class ConstantExpr : public Constant {
446 friend struct ConstantCreator<ConstantExpr,Type,
447 std::pair<unsigned, std::vector<Constant*> > >;
448 friend struct ConvertConstantType<ConstantExpr, Type>;
451 ConstantExpr(const Type *Ty, unsigned Opcode, Use *Ops, unsigned NumOps)
452 : Constant(Ty, ConstantExprVal, Ops, NumOps) {
453 // Operation type (an Instruction opcode) is stored as the SubclassData.
454 SubclassData = Opcode;
457 // These private methods are used by the type resolution code to create
458 // ConstantExprs in intermediate forms.
459 static Constant *getTy(const Type *Ty, unsigned Opcode,
460 Constant *C1, Constant *C2);
461 static Constant *getCompareTy(unsigned short pred, Constant *C1,
463 static Constant *getSelectTy(const Type *Ty,
464 Constant *C1, Constant *C2, Constant *C3);
465 static Constant *getGetElementPtrTy(const Type *Ty, Constant *C,
466 Value* const *Idxs, unsigned NumIdxs);
467 static Constant *getExtractElementTy(const Type *Ty, Constant *Val,
469 static Constant *getInsertElementTy(const Type *Ty, Constant *Val,
470 Constant *Elt, Constant *Idx);
471 static Constant *getShuffleVectorTy(const Type *Ty, Constant *V1,
472 Constant *V2, Constant *Mask);
475 // Static methods to construct a ConstantExpr of different kinds. Note that
476 // these methods may return a object that is not an instance of the
477 // ConstantExpr class, because they will attempt to fold the constant
478 // expression into something simpler if possible.
480 /// Cast constant expr
482 static Constant *getTrunc (Constant *C, const Type *Ty);
483 static Constant *getSExt (Constant *C, const Type *Ty);
484 static Constant *getZExt (Constant *C, const Type *Ty);
485 static Constant *getFPTrunc (Constant *C, const Type *Ty);
486 static Constant *getFPExtend(Constant *C, const Type *Ty);
487 static Constant *getUIToFP (Constant *C, const Type *Ty);
488 static Constant *getSIToFP (Constant *C, const Type *Ty);
489 static Constant *getFPToUI (Constant *C, const Type *Ty);
490 static Constant *getFPToSI (Constant *C, const Type *Ty);
491 static Constant *getPtrToInt(Constant *C, const Type *Ty);
492 static Constant *getIntToPtr(Constant *C, const Type *Ty);
493 static Constant *getBitCast (Constant *C, const Type *Ty);
495 // @brief Convenience function for getting one of the casting operations
496 // using a CastOps opcode.
497 static Constant *getCast(
498 unsigned ops, ///< The opcode for the conversion
499 Constant *C, ///< The constant to be converted
500 const Type *Ty ///< The type to which the constant is converted
503 // @brief Create a ZExt or BitCast cast constant expression
504 static Constant *getZExtOrBitCast(
505 Constant *C, ///< The constant to zext or bitcast
506 const Type *Ty ///< The type to zext or bitcast C to
509 // @brief Create a SExt or BitCast cast constant expression
510 static Constant *getSExtOrBitCast(
511 Constant *C, ///< The constant to sext or bitcast
512 const Type *Ty ///< The type to sext or bitcast C to
515 // @brief Create a Trunc or BitCast cast constant expression
516 static Constant *getTruncOrBitCast(
517 Constant *C, ///< The constant to trunc or bitcast
518 const Type *Ty ///< The type to trunc or bitcast C to
521 /// @brief Create a BitCast or a PtrToInt cast constant expression
522 static Constant *getPointerCast(
523 Constant *C, ///< The pointer value to be casted (operand 0)
524 const Type *Ty ///< The type to which cast should be made
527 /// @brief Create a ZExt, Bitcast or Trunc for integer -> integer casts
528 static Constant *getIntegerCast(
529 Constant *C, ///< The integer constant to be casted
530 const Type *Ty, ///< The integer type to cast to
531 bool isSigned ///< Whether C should be treated as signed or not
534 /// @brief Create a FPExt, Bitcast or FPTrunc for fp -> fp casts
535 static Constant *getFPCast(
536 Constant *C, ///< The integer constant to be casted
537 const Type *Ty ///< The integer type to cast to
540 /// @brief Return true if this is a convert constant expression
543 /// @brief Return true if this is a compare constant expression
544 bool isCompare() const;
546 /// Select constant expr
548 static Constant *getSelect(Constant *C, Constant *V1, Constant *V2) {
549 return getSelectTy(V1->getType(), C, V1, V2);
552 /// getSizeOf constant expr - computes the size of a type in a target
553 /// independent way (Note: the return type is a ULong).
555 static Constant *getSizeOf(const Type *Ty);
557 /// ConstantExpr::get - Return a binary or shift operator constant expression,
558 /// folding if possible.
560 static Constant *get(unsigned Opcode, Constant *C1, Constant *C2);
562 /// @brief Return an ICmp or FCmp comparison operator constant expression.
563 static Constant *getCompare(unsigned short pred, Constant *C1, Constant *C2);
565 /// ConstantExpr::get* - Return some common constants without having to
566 /// specify the full Instruction::OPCODE identifier.
568 static Constant *getNeg(Constant *C);
569 static Constant *getNot(Constant *C);
570 static Constant *getAdd(Constant *C1, Constant *C2);
571 static Constant *getSub(Constant *C1, Constant *C2);
572 static Constant *getMul(Constant *C1, Constant *C2);
573 static Constant *getUDiv(Constant *C1, Constant *C2);
574 static Constant *getSDiv(Constant *C1, Constant *C2);
575 static Constant *getFDiv(Constant *C1, Constant *C2);
576 static Constant *getURem(Constant *C1, Constant *C2); // unsigned rem
577 static Constant *getSRem(Constant *C1, Constant *C2); // signed rem
578 static Constant *getFRem(Constant *C1, Constant *C2);
579 static Constant *getAnd(Constant *C1, Constant *C2);
580 static Constant *getOr(Constant *C1, Constant *C2);
581 static Constant *getXor(Constant *C1, Constant *C2);
582 static Constant* getICmp(unsigned short pred, Constant* LHS, Constant* RHS);
583 static Constant* getFCmp(unsigned short pred, Constant* LHS, Constant* RHS);
584 static Constant *getShl(Constant *C1, Constant *C2);
585 static Constant *getLShr(Constant *C1, Constant *C2);
586 static Constant *getAShr(Constant *C1, Constant *C2);
588 /// Getelementptr form. std::vector<Value*> is only accepted for convenience:
589 /// all elements must be Constant's.
591 static Constant *getGetElementPtr(Constant *C,
592 Constant* const *IdxList, unsigned NumIdx);
593 static Constant *getGetElementPtr(Constant *C,
594 Value* const *IdxList, unsigned NumIdx);
596 static Constant *getExtractElement(Constant *Vec, Constant *Idx);
597 static Constant *getInsertElement(Constant *Vec, Constant *Elt,Constant *Idx);
598 static Constant *getShuffleVector(Constant *V1, Constant *V2, Constant *Mask);
600 /// Floating point negation must be implemented with f(x) = -0.0 - x. This
601 /// method returns the negative zero constant for floating point or packed
602 /// floating point types; for all other types, it returns the null value.
603 static Constant *getZeroValueForNegationExpr(const Type *Ty);
605 /// isNullValue - Return true if this is the value that would be returned by
607 virtual bool isNullValue() const { return false; }
609 /// getOpcode - Return the opcode at the root of this constant expression
610 unsigned getOpcode() const { return SubclassData; }
612 /// getPredicate - Return the ICMP or FCMP predicate value. Assert if this is
613 /// not an ICMP or FCMP constant expression.
614 unsigned getPredicate() const;
616 /// getOpcodeName - Return a string representation for an opcode.
617 const char *getOpcodeName() const;
619 /// getWithOperandReplaced - Return a constant expression identical to this
620 /// one, but with the specified operand set to the specified value.
621 Constant *getWithOperandReplaced(unsigned OpNo, Constant *Op) const;
623 /// getWithOperands - This returns the current constant expression with the
624 /// operands replaced with the specified values. The specified operands must
625 /// match count and type with the existing ones.
626 Constant *getWithOperands(const std::vector<Constant*> &Ops) const;
628 virtual void destroyConstant();
629 virtual void replaceUsesOfWithOnConstant(Value *From, Value *To, Use *U);
631 /// Override methods to provide more type information...
632 inline Constant *getOperand(unsigned i) {
633 return cast<Constant>(User::getOperand(i));
635 inline Constant *getOperand(unsigned i) const {
636 return const_cast<Constant*>(cast<Constant>(User::getOperand(i)));
640 /// Methods for support type inquiry through isa, cast, and dyn_cast:
641 static inline bool classof(const ConstantExpr *) { return true; }
642 static inline bool classof(const Value *V) {
643 return V->getValueType() == ConstantExprVal;
648 //===----------------------------------------------------------------------===//
649 /// UndefValue - 'undef' values are things that do not have specified contents.
650 /// These are used for a variety of purposes, including global variable
651 /// initializers and operands to instructions. 'undef' values can occur with
654 class UndefValue : public Constant {
655 friend struct ConstantCreator<UndefValue, Type, char>;
656 UndefValue(const UndefValue &); // DO NOT IMPLEMENT
658 UndefValue(const Type *T) : Constant(T, UndefValueVal, 0, 0) {}
660 /// get() - Static factory methods - Return an 'undef' object of the specified
663 static UndefValue *get(const Type *T);
665 /// isNullValue - Return true if this is the value that would be returned by
667 virtual bool isNullValue() const { return false; }
669 virtual void destroyConstant();
671 /// Methods for support type inquiry through isa, cast, and dyn_cast:
672 static inline bool classof(const UndefValue *) { return true; }
673 static bool classof(const Value *V) {
674 return V->getValueType() == UndefValueVal;
678 } // End llvm namespace