1 //===-- llvm/Value.h - Definition of the Value class ------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file declares the Value class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_IR_VALUE_H
15 #define LLVM_IR_VALUE_H
17 #include "llvm-c/Core.h"
18 #include "llvm/ADT/iterator_range.h"
19 #include "llvm/IR/Use.h"
20 #include "llvm/Support/CBindingWrapping.h"
21 #include "llvm/Support/Casting.h"
22 #include "llvm/Support/Compiler.h"
28 class AssemblyAnnotationWriter;
45 class ValueHandleBase;
46 class ValueSymbolTable;
49 template<typename ValueTy> class StringMapEntry;
50 typedef StringMapEntry<Value*> ValueName;
52 //===----------------------------------------------------------------------===//
54 //===----------------------------------------------------------------------===//
56 /// \brief LLVM Value Representation
58 /// This is a very important LLVM class. It is the base class of all values
59 /// computed by a program that may be used as operands to other values. Value is
60 /// the super class of other important classes such as Instruction and Function.
61 /// All Values have a Type. Type is not a subclass of Value. Some values can
62 /// have a name and they belong to some Module. Setting the name on the Value
63 /// automatically updates the module's symbol table.
65 /// Every value has a "use list" that keeps track of which other Values are
66 /// using this Value. A Value can also have an arbitrary number of ValueHandle
67 /// objects that watch it and listen to RAUW and Destroy events. See
68 /// llvm/IR/ValueHandle.h for details.
73 friend class ValueSymbolTable; // Allow ValueSymbolTable to directly mod Name.
74 friend class ValueHandleBase;
77 const unsigned char SubclassID; // Subclass identifier (for isa/dyn_cast)
78 unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this?
80 /// \brief Hold subclass data that can be dropped.
82 /// This member is similar to SubclassData, however it is for holding
83 /// information which may be used to aid optimization, but which may be
84 /// cleared to zero without affecting conservative interpretation.
85 unsigned char SubclassOptionalData : 7;
88 /// \brief Hold arbitrary subclass data.
90 /// This member is defined by this class, but is not used for anything.
91 /// Subclasses can use it to hold whatever state they find useful. This
92 /// field is initialized to zero by the ctor.
93 unsigned short SubclassData;
96 /// \brief The number of operands in the subclass.
98 /// This member is defined by this class, but not used for anything.
99 /// Subclasses can use it to store their number of operands, if they have
102 /// This is stored here to save space in User on 64-bit hosts. Since most
103 /// instances of Value have operands, 32-bit hosts aren't significantly
105 unsigned NumOperands;
108 template <typename UseT> // UseT == 'Use' or 'const Use'
109 class use_iterator_impl
110 : public std::iterator<std::forward_iterator_tag, UseT *, ptrdiff_t> {
111 typedef std::iterator<std::forward_iterator_tag, UseT *, ptrdiff_t> super;
114 explicit use_iterator_impl(UseT *u) : U(u) {}
118 typedef typename super::reference reference;
119 typedef typename super::pointer pointer;
121 use_iterator_impl() : U() {}
123 bool operator==(const use_iterator_impl &x) const { return U == x.U; }
124 bool operator!=(const use_iterator_impl &x) const { return !operator==(x); }
126 use_iterator_impl &operator++() { // Preincrement
127 assert(U && "Cannot increment end iterator!");
131 use_iterator_impl operator++(int) { // Postincrement
137 UseT &operator*() const {
138 assert(U && "Cannot dereference end iterator!");
142 UseT *operator->() const { return &operator*(); }
144 operator use_iterator_impl<const UseT>() const {
145 return use_iterator_impl<const UseT>(U);
149 template <typename UserTy> // UserTy == 'User' or 'const User'
150 class user_iterator_impl
151 : public std::iterator<std::forward_iterator_tag, UserTy *, ptrdiff_t> {
152 typedef std::iterator<std::forward_iterator_tag, UserTy *, ptrdiff_t> super;
154 use_iterator_impl<Use> UI;
155 explicit user_iterator_impl(Use *U) : UI(U) {}
159 typedef typename super::reference reference;
160 typedef typename super::pointer pointer;
162 user_iterator_impl() {}
164 bool operator==(const user_iterator_impl &x) const { return UI == x.UI; }
165 bool operator!=(const user_iterator_impl &x) const { return !operator==(x); }
167 /// \brief Returns true if this iterator is equal to user_end() on the value.
168 bool atEnd() const { return *this == user_iterator_impl(); }
170 user_iterator_impl &operator++() { // Preincrement
174 user_iterator_impl operator++(int) { // Postincrement
180 // Retrieve a pointer to the current User.
181 UserTy *operator*() const {
182 return UI->getUser();
185 UserTy *operator->() const { return operator*(); }
187 operator user_iterator_impl<const UserTy>() const {
188 return user_iterator_impl<const UserTy>(*UI);
191 Use &getUse() const { return *UI; }
193 /// \brief Return the operand # of this use in its User.
195 /// FIXME: Replace all callers with a direct call to Use::getOperandNo.
196 unsigned getOperandNo() const { return UI->getOperandNo(); }
199 void operator=(const Value &) LLVM_DELETED_FUNCTION;
200 Value(const Value &) LLVM_DELETED_FUNCTION;
203 Value(Type *Ty, unsigned scid);
207 /// \brief Support for debugging, callable in GDB: V->dump()
210 /// \brief Implement operator<< on Value.
211 void print(raw_ostream &O) const;
213 /// \brief Print the name of this Value out to the specified raw_ostream.
215 /// This is useful when you just want to print 'int %reg126', not the
216 /// instruction that generated it. If you specify a Module for context, then
217 /// even constanst get pretty-printed; for example, the type of a null
218 /// pointer is printed symbolically.
219 void printAsOperand(raw_ostream &O, bool PrintType = true,
220 const Module *M = nullptr) const;
222 /// \brief All values are typed, get the type of this value.
223 Type *getType() const { return VTy; }
225 /// \brief All values hold a context through their type.
226 LLVMContext &getContext() const;
228 // \brief All values can potentially be named.
229 bool hasName() const { return Name != nullptr; }
230 ValueName *getValueName() const { return Name; }
231 void setValueName(ValueName *VN) { Name = VN; }
233 /// \brief Return a constant reference to the value's name.
235 /// This is cheap and guaranteed to return the same reference as long as the
236 /// value is not modified.
237 StringRef getName() const;
239 /// \brief Change the name of the value.
241 /// Choose a new unique name if the provided name is taken.
243 /// \param Name The new name; or "" if the value's name should be removed.
244 void setName(const Twine &Name);
247 /// \brief Transfer the name from V to this value.
249 /// After taking V's name, sets V's name to empty.
251 /// \note It is an error to call V->takeName(V).
252 void takeName(Value *V);
254 /// \brief Change all uses of this to point to a new Value.
256 /// Go through the uses list for this definition and make each use point to
257 /// "V" instead of "this". After this completes, 'this's use list is
258 /// guaranteed to be empty.
259 void replaceAllUsesWith(Value *V);
261 //----------------------------------------------------------------------
262 // Methods for handling the chain of uses of this Value.
264 bool use_empty() const { return UseList == nullptr; }
266 typedef use_iterator_impl<Use> use_iterator;
267 typedef use_iterator_impl<const Use> const_use_iterator;
268 use_iterator use_begin() { return use_iterator(UseList); }
269 const_use_iterator use_begin() const { return const_use_iterator(UseList); }
270 use_iterator use_end() { return use_iterator(); }
271 const_use_iterator use_end() const { return const_use_iterator(); }
272 iterator_range<use_iterator> uses() {
273 return iterator_range<use_iterator>(use_begin(), use_end());
275 iterator_range<const_use_iterator> uses() const {
276 return iterator_range<const_use_iterator>(use_begin(), use_end());
279 typedef user_iterator_impl<User> user_iterator;
280 typedef user_iterator_impl<const User> const_user_iterator;
281 user_iterator user_begin() { return user_iterator(UseList); }
282 const_user_iterator user_begin() const { return const_user_iterator(UseList); }
283 user_iterator user_end() { return user_iterator(); }
284 const_user_iterator user_end() const { return const_user_iterator(); }
285 User *user_back() { return *user_begin(); }
286 const User *user_back() const { return *user_begin(); }
287 iterator_range<user_iterator> users() {
288 return iterator_range<user_iterator>(user_begin(), user_end());
290 iterator_range<const_user_iterator> users() const {
291 return iterator_range<const_user_iterator>(user_begin(), user_end());
294 /// \brief Return true if there is exactly one user of this value.
296 /// This is specialized because it is a common request and does not require
297 /// traversing the whole use list.
298 bool hasOneUse() const {
299 const_use_iterator I = use_begin(), E = use_end();
300 if (I == E) return false;
304 /// \brief Return true if this Value has exactly N users.
305 bool hasNUses(unsigned N) const;
307 /// \brief Return true if this value has N users or more.
309 /// This is logically equivalent to getNumUses() >= N.
310 bool hasNUsesOrMore(unsigned N) const;
312 /// \brief Check if this value is used in the specified basic block.
313 bool isUsedInBasicBlock(const BasicBlock *BB) const;
315 /// \brief This method computes the number of uses of this Value.
317 /// This is a linear time operation. Use hasOneUse, hasNUses, or
318 /// hasNUsesOrMore to check for specific values.
319 unsigned getNumUses() const;
321 /// \brief This method should only be used by the Use class.
322 void addUse(Use &U) { U.addToList(&UseList); }
324 /// \brief Concrete subclass of this.
326 /// An enumeration for keeping track of the concrete subclass of Value that
327 /// is actually instantiated. Values of this enumeration are kept in the
328 /// Value classes SubclassID field. They are used for concrete type
331 ArgumentVal, // This is an instance of Argument
332 BasicBlockVal, // This is an instance of BasicBlock
333 FunctionVal, // This is an instance of Function
334 GlobalAliasVal, // This is an instance of GlobalAlias
335 GlobalVariableVal, // This is an instance of GlobalVariable
336 UndefValueVal, // This is an instance of UndefValue
337 BlockAddressVal, // This is an instance of BlockAddress
338 ConstantExprVal, // This is an instance of ConstantExpr
339 ConstantAggregateZeroVal, // This is an instance of ConstantAggregateZero
340 ConstantDataArrayVal, // This is an instance of ConstantDataArray
341 ConstantDataVectorVal, // This is an instance of ConstantDataVector
342 ConstantIntVal, // This is an instance of ConstantInt
343 ConstantFPVal, // This is an instance of ConstantFP
344 ConstantArrayVal, // This is an instance of ConstantArray
345 ConstantStructVal, // This is an instance of ConstantStruct
346 ConstantVectorVal, // This is an instance of ConstantVector
347 ConstantPointerNullVal, // This is an instance of ConstantPointerNull
348 GenericMDNodeVal, // This is an instance of GenericMDNode
349 MDNodeFwdDeclVal, // This is an instance of MDNodeFwdDecl
350 MDStringVal, // This is an instance of MDString
351 InlineAsmVal, // This is an instance of InlineAsm
352 InstructionVal, // This is an instance of Instruction
353 // Enum values starting at InstructionVal are used for Instructions;
354 // don't add new values here!
357 ConstantFirstVal = FunctionVal,
358 ConstantLastVal = ConstantPointerNullVal
361 /// \brief Return an ID for the concrete type of this object.
363 /// This is used to implement the classof checks. This should not be used
364 /// for any other purpose, as the values may change as LLVM evolves. Also,
365 /// note that for instructions, the Instruction's opcode is added to
366 /// InstructionVal. So this means three things:
367 /// # there is no value with code InstructionVal (no opcode==0).
368 /// # there are more possible values for the value type than in ValueTy enum.
369 /// # the InstructionVal enumerator must be the highest valued enumerator in
370 /// the ValueTy enum.
371 unsigned getValueID() const {
375 /// \brief Return the raw optional flags value contained in this value.
377 /// This should only be used when testing two Values for equivalence.
378 unsigned getRawSubclassOptionalData() const {
379 return SubclassOptionalData;
382 /// \brief Clear the optional flags contained in this value.
383 void clearSubclassOptionalData() {
384 SubclassOptionalData = 0;
387 /// \brief Check the optional flags for equality.
388 bool hasSameSubclassOptionalData(const Value *V) const {
389 return SubclassOptionalData == V->SubclassOptionalData;
392 /// \brief Clear any optional flags not set in the given Value.
393 void intersectOptionalDataWith(const Value *V) {
394 SubclassOptionalData &= V->SubclassOptionalData;
397 /// \brief Return true if there is a value handle associated with this value.
398 bool hasValueHandle() const { return HasValueHandle; }
400 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
402 /// Returns the original uncasted value. If this is called on a non-pointer
403 /// value, it returns 'this'.
404 Value *stripPointerCasts();
405 const Value *stripPointerCasts() const {
406 return const_cast<Value*>(this)->stripPointerCasts();
409 /// \brief Strip off pointer casts and all-zero GEPs.
411 /// Returns the original uncasted value. If this is called on a non-pointer
412 /// value, it returns 'this'.
413 Value *stripPointerCastsNoFollowAliases();
414 const Value *stripPointerCastsNoFollowAliases() const {
415 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
418 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
420 /// Returns the original pointer value. If this is called on a non-pointer
421 /// value, it returns 'this'.
422 Value *stripInBoundsConstantOffsets();
423 const Value *stripInBoundsConstantOffsets() const {
424 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
427 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
429 /// Stores the resulting constant offset stripped into the APInt provided.
430 /// The provided APInt will be extended or truncated as needed to be the
431 /// correct bitwidth for an offset of this pointer type.
433 /// If this is called on a non-pointer value, it returns 'this'.
434 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
436 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
437 APInt &Offset) const {
438 return const_cast<Value *>(this)
439 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
442 /// \brief Strip off pointer casts and inbounds GEPs.
444 /// Returns the original pointer value. If this is called on a non-pointer
445 /// value, it returns 'this'.
446 Value *stripInBoundsOffsets();
447 const Value *stripInBoundsOffsets() const {
448 return const_cast<Value*>(this)->stripInBoundsOffsets();
451 /// \brief Check if this is always a dereferenceable pointer.
453 /// Test if this value is always a pointer to allocated and suitably aligned
454 /// memory for a simple load or store.
455 bool isDereferenceablePointer(const DataLayout *DL = nullptr) const;
457 /// \brief Translate PHI node to its predecessor from the given basic block.
459 /// If this value is a PHI node with CurBB as its parent, return the value in
460 /// the PHI node corresponding to PredBB. If not, return ourself. This is
461 /// useful if you want to know the value something has in a predecessor
463 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
465 const Value *DoPHITranslation(const BasicBlock *CurBB,
466 const BasicBlock *PredBB) const{
467 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
470 /// \brief The maximum alignment for instructions.
472 /// This is the greatest alignment value supported by load, store, and alloca
473 /// instructions, and global values.
474 static const unsigned MaximumAlignment = 1u << 29;
476 /// \brief Mutate the type of this Value to be of the specified type.
478 /// Note that this is an extremely dangerous operation which can create
479 /// completely invalid IR very easily. It is strongly recommended that you
480 /// recreate IR objects with the right types instead of mutating them in
482 void mutateType(Type *Ty) {
486 /// \brief Sort the use-list.
488 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
489 /// expected to compare two \a Use references.
490 template <class Compare> void sortUseList(Compare Cmp);
492 /// \brief Reverse the use-list.
493 void reverseUseList();
496 /// \brief Merge two lists together.
498 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
499 /// "equal" items from L before items from R.
501 /// \return the first element in the list.
503 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
504 template <class Compare>
505 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
507 mergeUseListsImpl(L, R, &Merged, Cmp);
511 /// \brief Tail-recursive helper for \a mergeUseLists().
513 /// \param[out] Next the first element in the list.
514 template <class Compare>
515 static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
518 unsigned short getSubclassDataFromValue() const { return SubclassData; }
519 void setValueSubclassData(unsigned short D) { SubclassData = D; }
522 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
527 void Use::set(Value *V) {
528 if (Val) removeFromList();
530 if (V) V->addUse(*this);
533 template <class Compare> void Value::sortUseList(Compare Cmp) {
534 if (!UseList || !UseList->Next)
535 // No need to sort 0 or 1 uses.
538 // Note: this function completely ignores Prev pointers until the end when
539 // they're fixed en masse.
541 // Create a binomial vector of sorted lists, visiting uses one at a time and
542 // merging lists as necessary.
543 const unsigned MaxSlots = 32;
544 Use *Slots[MaxSlots];
546 // Collect the first use, turning it into a single-item list.
547 Use *Next = UseList->Next;
548 UseList->Next = nullptr;
549 unsigned NumSlots = 1;
552 // Collect all but the last use.
555 Next = Current->Next;
557 // Turn Current into a single-item list.
558 Current->Next = nullptr;
560 // Save Current in the first available slot, merging on collisions.
562 for (I = 0; I < NumSlots; ++I) {
566 // Merge two lists, doubling the size of Current and emptying slot I.
568 // Since the uses in Slots[I] originally preceded those in Current, send
569 // Slots[I] in as the left parameter to maintain a stable sort.
570 Current = mergeUseLists(Slots[I], Current, Cmp);
573 // Check if this is a new slot.
576 assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
579 // Found an open slot.
583 // Merge all the lists together.
584 assert(Next && "Expected one more Use");
585 assert(!Next->Next && "Expected only one Use");
587 for (unsigned I = 0; I < NumSlots; ++I)
589 // Since the uses in Slots[I] originally preceded those in UseList, send
590 // Slots[I] in as the left parameter to maintain a stable sort.
591 UseList = mergeUseLists(Slots[I], UseList, Cmp);
593 // Fix the Prev pointers.
594 for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
600 template <class Compare>
601 void Value::mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp) {
612 mergeUseListsImpl(L, R->Next, &R->Next, Cmp);
616 mergeUseListsImpl(L->Next, R, &L->Next, Cmp);
619 // isa - Provide some specializations of isa so that we don't have to include
620 // the subtype header files to test to see if the value is a subclass...
622 template <> struct isa_impl<Constant, Value> {
623 static inline bool doit(const Value &Val) {
624 return Val.getValueID() >= Value::ConstantFirstVal &&
625 Val.getValueID() <= Value::ConstantLastVal;
629 template <> struct isa_impl<Argument, Value> {
630 static inline bool doit (const Value &Val) {
631 return Val.getValueID() == Value::ArgumentVal;
635 template <> struct isa_impl<InlineAsm, Value> {
636 static inline bool doit(const Value &Val) {
637 return Val.getValueID() == Value::InlineAsmVal;
641 template <> struct isa_impl<Instruction, Value> {
642 static inline bool doit(const Value &Val) {
643 return Val.getValueID() >= Value::InstructionVal;
647 template <> struct isa_impl<BasicBlock, Value> {
648 static inline bool doit(const Value &Val) {
649 return Val.getValueID() == Value::BasicBlockVal;
653 template <> struct isa_impl<Function, Value> {
654 static inline bool doit(const Value &Val) {
655 return Val.getValueID() == Value::FunctionVal;
659 template <> struct isa_impl<GlobalVariable, Value> {
660 static inline bool doit(const Value &Val) {
661 return Val.getValueID() == Value::GlobalVariableVal;
665 template <> struct isa_impl<GlobalAlias, Value> {
666 static inline bool doit(const Value &Val) {
667 return Val.getValueID() == Value::GlobalAliasVal;
671 template <> struct isa_impl<GlobalValue, Value> {
672 static inline bool doit(const Value &Val) {
673 return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
677 template <> struct isa_impl<GlobalObject, Value> {
678 static inline bool doit(const Value &Val) {
679 return isa<GlobalVariable>(Val) || isa<Function>(Val);
683 template <> struct isa_impl<MDNode, Value> {
684 static inline bool doit(const Value &Val) {
685 return Val.getValueID() == Value::GenericMDNodeVal ||
686 Val.getValueID() == Value::MDNodeFwdDeclVal;
690 // Value* is only 4-byte aligned.
692 class PointerLikeTypeTraits<Value*> {
695 static inline void *getAsVoidPointer(PT P) { return P; }
696 static inline PT getFromVoidPointer(void *P) {
697 return static_cast<PT>(P);
699 enum { NumLowBitsAvailable = 2 };
702 // Create wrappers for C Binding types (see CBindingWrapping.h).
703 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
705 /* Specialized opaque value conversions.
707 inline Value **unwrap(LLVMValueRef *Vals) {
708 return reinterpret_cast<Value**>(Vals);
712 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
714 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
718 return reinterpret_cast<T**>(Vals);
721 inline LLVMValueRef *wrap(const Value **Vals) {
722 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
725 } // End llvm namespace