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 && SubclassID != MDStringVal; }
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 MDNodeVal, // This is an instance of MDNode
349 MDStringVal, // This is an instance of MDString
350 InlineAsmVal, // This is an instance of InlineAsm
351 InstructionVal, // This is an instance of Instruction
352 // Enum values starting at InstructionVal are used for Instructions;
353 // don't add new values here!
356 ConstantFirstVal = FunctionVal,
357 ConstantLastVal = ConstantPointerNullVal
360 /// \brief Return an ID for the concrete type of this object.
362 /// This is used to implement the classof checks. This should not be used
363 /// for any other purpose, as the values may change as LLVM evolves. Also,
364 /// note that for instructions, the Instruction's opcode is added to
365 /// InstructionVal. So this means three things:
366 /// # there is no value with code InstructionVal (no opcode==0).
367 /// # there are more possible values for the value type than in ValueTy enum.
368 /// # the InstructionVal enumerator must be the highest valued enumerator in
369 /// the ValueTy enum.
370 unsigned getValueID() const {
374 /// \brief Return the raw optional flags value contained in this value.
376 /// This should only be used when testing two Values for equivalence.
377 unsigned getRawSubclassOptionalData() const {
378 return SubclassOptionalData;
381 /// \brief Clear the optional flags contained in this value.
382 void clearSubclassOptionalData() {
383 SubclassOptionalData = 0;
386 /// \brief Check the optional flags for equality.
387 bool hasSameSubclassOptionalData(const Value *V) const {
388 return SubclassOptionalData == V->SubclassOptionalData;
391 /// \brief Clear any optional flags not set in the given Value.
392 void intersectOptionalDataWith(const Value *V) {
393 SubclassOptionalData &= V->SubclassOptionalData;
396 /// \brief Return true if there is a value handle associated with this value.
397 bool hasValueHandle() const { return HasValueHandle; }
399 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
401 /// Returns the original uncasted value. If this is called on a non-pointer
402 /// value, it returns 'this'.
403 Value *stripPointerCasts();
404 const Value *stripPointerCasts() const {
405 return const_cast<Value*>(this)->stripPointerCasts();
408 /// \brief Strip off pointer casts and all-zero GEPs.
410 /// Returns the original uncasted value. If this is called on a non-pointer
411 /// value, it returns 'this'.
412 Value *stripPointerCastsNoFollowAliases();
413 const Value *stripPointerCastsNoFollowAliases() const {
414 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
417 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
419 /// Returns the original pointer value. If this is called on a non-pointer
420 /// value, it returns 'this'.
421 Value *stripInBoundsConstantOffsets();
422 const Value *stripInBoundsConstantOffsets() const {
423 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
426 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
428 /// Stores the resulting constant offset stripped into the APInt provided.
429 /// The provided APInt will be extended or truncated as needed to be the
430 /// correct bitwidth for an offset of this pointer type.
432 /// If this is called on a non-pointer value, it returns 'this'.
433 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
435 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
436 APInt &Offset) const {
437 return const_cast<Value *>(this)
438 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
441 /// \brief Strip off pointer casts and inbounds GEPs.
443 /// Returns the original pointer value. If this is called on a non-pointer
444 /// value, it returns 'this'.
445 Value *stripInBoundsOffsets();
446 const Value *stripInBoundsOffsets() const {
447 return const_cast<Value*>(this)->stripInBoundsOffsets();
450 /// \brief Check if this is always a dereferenceable pointer.
452 /// Test if this value is always a pointer to allocated and suitably aligned
453 /// memory for a simple load or store.
454 bool isDereferenceablePointer(const DataLayout *DL = nullptr) const;
456 /// \brief Translate PHI node to its predecessor from the given basic block.
458 /// If this value is a PHI node with CurBB as its parent, return the value in
459 /// the PHI node corresponding to PredBB. If not, return ourself. This is
460 /// useful if you want to know the value something has in a predecessor
462 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
464 const Value *DoPHITranslation(const BasicBlock *CurBB,
465 const BasicBlock *PredBB) const{
466 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
469 /// \brief The maximum alignment for instructions.
471 /// This is the greatest alignment value supported by load, store, and alloca
472 /// instructions, and global values.
473 static const unsigned MaximumAlignment = 1u << 29;
475 /// \brief Mutate the type of this Value to be of the specified type.
477 /// Note that this is an extremely dangerous operation which can create
478 /// completely invalid IR very easily. It is strongly recommended that you
479 /// recreate IR objects with the right types instead of mutating them in
481 void mutateType(Type *Ty) {
485 /// \brief Sort the use-list.
487 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
488 /// expected to compare two \a Use references.
489 template <class Compare> void sortUseList(Compare Cmp);
491 /// \brief Reverse the use-list.
492 void reverseUseList();
495 /// \brief Merge two lists together.
497 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
498 /// "equal" items from L before items from R.
500 /// \return the first element in the list.
502 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
503 template <class Compare>
504 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
506 mergeUseListsImpl(L, R, &Merged, Cmp);
510 /// \brief Tail-recursive helper for \a mergeUseLists().
512 /// \param[out] Next the first element in the list.
513 template <class Compare>
514 static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
517 unsigned short getSubclassDataFromValue() const { return SubclassData; }
518 void setValueSubclassData(unsigned short D) { SubclassData = D; }
521 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
526 void Use::set(Value *V) {
527 if (Val) removeFromList();
529 if (V) V->addUse(*this);
532 template <class Compare> void Value::sortUseList(Compare Cmp) {
533 if (!UseList || !UseList->Next)
534 // No need to sort 0 or 1 uses.
537 // Note: this function completely ignores Prev pointers until the end when
538 // they're fixed en masse.
540 // Create a binomial vector of sorted lists, visiting uses one at a time and
541 // merging lists as necessary.
542 const unsigned MaxSlots = 32;
543 Use *Slots[MaxSlots];
545 // Collect the first use, turning it into a single-item list.
546 Use *Next = UseList->Next;
547 UseList->Next = nullptr;
548 unsigned NumSlots = 1;
551 // Collect all but the last use.
554 Next = Current->Next;
556 // Turn Current into a single-item list.
557 Current->Next = nullptr;
559 // Save Current in the first available slot, merging on collisions.
561 for (I = 0; I < NumSlots; ++I) {
565 // Merge two lists, doubling the size of Current and emptying slot I.
567 // Since the uses in Slots[I] originally preceded those in Current, send
568 // Slots[I] in as the left parameter to maintain a stable sort.
569 Current = mergeUseLists(Slots[I], Current, Cmp);
572 // Check if this is a new slot.
575 assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
578 // Found an open slot.
582 // Merge all the lists together.
583 assert(Next && "Expected one more Use");
584 assert(!Next->Next && "Expected only one Use");
586 for (unsigned I = 0; I < NumSlots; ++I)
588 // Since the uses in Slots[I] originally preceded those in UseList, send
589 // Slots[I] in as the left parameter to maintain a stable sort.
590 UseList = mergeUseLists(Slots[I], UseList, Cmp);
592 // Fix the Prev pointers.
593 for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
599 template <class Compare>
600 void Value::mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp) {
611 mergeUseListsImpl(L, R->Next, &R->Next, Cmp);
615 mergeUseListsImpl(L->Next, R, &L->Next, Cmp);
618 // isa - Provide some specializations of isa so that we don't have to include
619 // the subtype header files to test to see if the value is a subclass...
621 template <> struct isa_impl<Constant, Value> {
622 static inline bool doit(const Value &Val) {
623 return Val.getValueID() >= Value::ConstantFirstVal &&
624 Val.getValueID() <= Value::ConstantLastVal;
628 template <> struct isa_impl<Argument, Value> {
629 static inline bool doit (const Value &Val) {
630 return Val.getValueID() == Value::ArgumentVal;
634 template <> struct isa_impl<InlineAsm, Value> {
635 static inline bool doit(const Value &Val) {
636 return Val.getValueID() == Value::InlineAsmVal;
640 template <> struct isa_impl<Instruction, Value> {
641 static inline bool doit(const Value &Val) {
642 return Val.getValueID() >= Value::InstructionVal;
646 template <> struct isa_impl<BasicBlock, Value> {
647 static inline bool doit(const Value &Val) {
648 return Val.getValueID() == Value::BasicBlockVal;
652 template <> struct isa_impl<Function, Value> {
653 static inline bool doit(const Value &Val) {
654 return Val.getValueID() == Value::FunctionVal;
658 template <> struct isa_impl<GlobalVariable, Value> {
659 static inline bool doit(const Value &Val) {
660 return Val.getValueID() == Value::GlobalVariableVal;
664 template <> struct isa_impl<GlobalAlias, Value> {
665 static inline bool doit(const Value &Val) {
666 return Val.getValueID() == Value::GlobalAliasVal;
670 template <> struct isa_impl<GlobalValue, Value> {
671 static inline bool doit(const Value &Val) {
672 return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
676 template <> struct isa_impl<GlobalObject, Value> {
677 static inline bool doit(const Value &Val) {
678 return isa<GlobalVariable>(Val) || isa<Function>(Val);
682 template <> struct isa_impl<MDNode, Value> {
683 static inline bool doit(const Value &Val) {
684 return Val.getValueID() == Value::MDNodeVal;
688 // Value* is only 4-byte aligned.
690 class PointerLikeTypeTraits<Value*> {
693 static inline void *getAsVoidPointer(PT P) { return P; }
694 static inline PT getFromVoidPointer(void *P) {
695 return static_cast<PT>(P);
697 enum { NumLowBitsAvailable = 2 };
700 // Create wrappers for C Binding types (see CBindingWrapping.h).
701 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
703 /* Specialized opaque value conversions.
705 inline Value **unwrap(LLVMValueRef *Vals) {
706 return reinterpret_cast<Value**>(Vals);
710 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
712 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
716 return reinterpret_cast<T**>(Vals);
719 inline LLVMValueRef *wrap(const Value **Vals) {
720 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
723 } // End llvm namespace