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;
44 class ValueHandleBase;
45 class ValueSymbolTable;
48 template<typename ValueTy> class StringMapEntry;
49 typedef StringMapEntry<Value*> ValueName;
51 //===----------------------------------------------------------------------===//
53 //===----------------------------------------------------------------------===//
55 /// \brief LLVM Value Representation
57 /// This is a very important LLVM class. It is the base class of all values
58 /// computed by a program that may be used as operands to other values. Value is
59 /// the super class of other important classes such as Instruction and Function.
60 /// All Values have a Type. Type is not a subclass of Value. Some values can
61 /// have a name and they belong to some Module. Setting the name on the Value
62 /// automatically updates the module's symbol table.
64 /// Every value has a "use list" that keeps track of which other Values are
65 /// using this Value. A Value can also have an arbitrary number of ValueHandle
66 /// objects that watch it and listen to RAUW and Destroy events. See
67 /// llvm/IR/ValueHandle.h for details.
72 friend class ValueAsMetadata; // Allow access to IsUsedByMD.
73 friend class ValueHandleBase;
75 const unsigned char SubclassID; // Subclass identifier (for isa/dyn_cast)
76 unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this?
78 /// \brief Hold subclass data that can be dropped.
80 /// This member is similar to SubclassData, however it is for holding
81 /// information which may be used to aid optimization, but which may be
82 /// cleared to zero without affecting conservative interpretation.
83 unsigned char SubclassOptionalData : 7;
86 /// \brief Hold arbitrary subclass data.
88 /// This member is defined by this class, but is not used for anything.
89 /// Subclasses can use it to hold whatever state they find useful. This
90 /// field is initialized to zero by the ctor.
91 unsigned short SubclassData;
94 /// \brief The number of operands in the subclass.
96 /// This member is defined by this class, but not used for anything.
97 /// Subclasses can use it to store their number of operands, if they have
100 /// This is stored here to save space in User on 64-bit hosts. Since most
101 /// instances of Value have operands, 32-bit hosts aren't significantly
103 unsigned NumOperands : 30;
109 template <typename UseT> // UseT == 'Use' or 'const Use'
110 class use_iterator_impl
111 : public std::iterator<std::forward_iterator_tag, UseT *> {
113 explicit use_iterator_impl(UseT *u) : U(u) {}
117 use_iterator_impl() : U() {}
119 bool operator==(const use_iterator_impl &x) const { return U == x.U; }
120 bool operator!=(const use_iterator_impl &x) const { return !operator==(x); }
122 use_iterator_impl &operator++() { // Preincrement
123 assert(U && "Cannot increment end iterator!");
127 use_iterator_impl operator++(int) { // Postincrement
133 UseT &operator*() const {
134 assert(U && "Cannot dereference end iterator!");
138 UseT *operator->() const { return &operator*(); }
140 operator use_iterator_impl<const UseT>() const {
141 return use_iterator_impl<const UseT>(U);
145 template <typename UserTy> // UserTy == 'User' or 'const User'
146 class user_iterator_impl
147 : public std::iterator<std::forward_iterator_tag, UserTy *> {
148 use_iterator_impl<Use> UI;
149 explicit user_iterator_impl(Use *U) : UI(U) {}
153 user_iterator_impl() {}
155 bool operator==(const user_iterator_impl &x) const { return UI == x.UI; }
156 bool operator!=(const user_iterator_impl &x) const { return !operator==(x); }
158 /// \brief Returns true if this iterator is equal to user_end() on the value.
159 bool atEnd() const { return *this == user_iterator_impl(); }
161 user_iterator_impl &operator++() { // Preincrement
165 user_iterator_impl operator++(int) { // Postincrement
171 // Retrieve a pointer to the current User.
172 UserTy *operator*() const {
173 return UI->getUser();
176 UserTy *operator->() const { return operator*(); }
178 operator user_iterator_impl<const UserTy>() const {
179 return user_iterator_impl<const UserTy>(*UI);
182 Use &getUse() const { return *UI; }
185 void operator=(const Value &) = delete;
186 Value(const Value &) = delete;
189 Value(Type *Ty, unsigned scid);
193 /// \brief Support for debugging, callable in GDB: V->dump()
196 /// \brief Implement operator<< on Value.
197 void print(raw_ostream &O) const;
199 /// \brief Print the name of this Value out to the specified raw_ostream.
201 /// This is useful when you just want to print 'int %reg126', not the
202 /// instruction that generated it. If you specify a Module for context, then
203 /// even constanst get pretty-printed; for example, the type of a null
204 /// pointer is printed symbolically.
205 void printAsOperand(raw_ostream &O, bool PrintType = true,
206 const Module *M = nullptr) const;
208 /// \brief All values are typed, get the type of this value.
209 Type *getType() const { return VTy; }
211 /// \brief All values hold a context through their type.
212 LLVMContext &getContext() const;
214 // \brief All values can potentially be named.
215 bool hasName() const { return HasName; }
216 ValueName *getValueName() const;
217 void setValueName(ValueName *VN);
220 void destroyValueName();
221 void setNameImpl(const Twine &Name);
224 /// \brief Return a constant reference to the value's name.
226 /// This is cheap and guaranteed to return the same reference as long as the
227 /// value is not modified.
228 StringRef getName() const;
230 /// \brief Change the name of the value.
232 /// Choose a new unique name if the provided name is taken.
234 /// \param Name The new name; or "" if the value's name should be removed.
235 void setName(const Twine &Name);
238 /// \brief Transfer the name from V to this value.
240 /// After taking V's name, sets V's name to empty.
242 /// \note It is an error to call V->takeName(V).
243 void takeName(Value *V);
245 /// \brief Change all uses of this to point to a new Value.
247 /// Go through the uses list for this definition and make each use point to
248 /// "V" instead of "this". After this completes, 'this's use list is
249 /// guaranteed to be empty.
250 void replaceAllUsesWith(Value *V);
252 /// replaceUsesOutsideBlock - Go through the uses list for this definition and
253 /// make each use point to "V" instead of "this" when the use is outside the
254 /// block. 'This's use list is expected to have at least one element.
255 /// Unlike replaceAllUsesWith this function does not support basic block
256 /// values or constant users.
257 void replaceUsesOutsideBlock(Value *V, BasicBlock *BB);
259 //----------------------------------------------------------------------
260 // Methods for handling the chain of uses of this Value.
262 bool use_empty() const { return UseList == nullptr; }
264 typedef use_iterator_impl<Use> use_iterator;
265 typedef use_iterator_impl<const Use> const_use_iterator;
266 use_iterator use_begin() { return use_iterator(UseList); }
267 const_use_iterator use_begin() const { return const_use_iterator(UseList); }
268 use_iterator use_end() { return use_iterator(); }
269 const_use_iterator use_end() const { return const_use_iterator(); }
270 iterator_range<use_iterator> uses() {
271 return iterator_range<use_iterator>(use_begin(), use_end());
273 iterator_range<const_use_iterator> uses() const {
274 return iterator_range<const_use_iterator>(use_begin(), use_end());
277 bool user_empty() const { return UseList == nullptr; }
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 MetadataAsValueVal, // This is an instance of MetadataAsValue
349 InlineAsmVal, // This is an instance of InlineAsm
350 InstructionVal, // This is an instance of Instruction
351 // Enum values starting at InstructionVal are used for Instructions;
352 // don't add new values here!
355 ConstantFirstVal = FunctionVal,
356 ConstantLastVal = ConstantPointerNullVal
359 /// \brief Return an ID for the concrete type of this object.
361 /// This is used to implement the classof checks. This should not be used
362 /// for any other purpose, as the values may change as LLVM evolves. Also,
363 /// note that for instructions, the Instruction's opcode is added to
364 /// InstructionVal. So this means three things:
365 /// # there is no value with code InstructionVal (no opcode==0).
366 /// # there are more possible values for the value type than in ValueTy enum.
367 /// # the InstructionVal enumerator must be the highest valued enumerator in
368 /// the ValueTy enum.
369 unsigned getValueID() const {
373 /// \brief Return the raw optional flags value contained in this value.
375 /// This should only be used when testing two Values for equivalence.
376 unsigned getRawSubclassOptionalData() const {
377 return SubclassOptionalData;
380 /// \brief Clear the optional flags contained in this value.
381 void clearSubclassOptionalData() {
382 SubclassOptionalData = 0;
385 /// \brief Check the optional flags for equality.
386 bool hasSameSubclassOptionalData(const Value *V) const {
387 return SubclassOptionalData == V->SubclassOptionalData;
390 /// \brief Clear any optional flags not set in the given Value.
391 void intersectOptionalDataWith(const Value *V) {
392 SubclassOptionalData &= V->SubclassOptionalData;
395 /// \brief Return true if there is a value handle associated with this value.
396 bool hasValueHandle() const { return HasValueHandle; }
398 /// \brief Return true if there is metadata referencing this value.
399 bool isUsedByMetadata() const { return IsUsedByMD; }
401 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
403 /// Returns the original uncasted value. If this is called on a non-pointer
404 /// value, it returns 'this'.
405 Value *stripPointerCasts();
406 const Value *stripPointerCasts() const {
407 return const_cast<Value*>(this)->stripPointerCasts();
410 /// \brief Strip off pointer casts and all-zero GEPs.
412 /// Returns the original uncasted value. If this is called on a non-pointer
413 /// value, it returns 'this'.
414 Value *stripPointerCastsNoFollowAliases();
415 const Value *stripPointerCastsNoFollowAliases() const {
416 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
419 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
421 /// Returns the original pointer value. If this is called on a non-pointer
422 /// value, it returns 'this'.
423 Value *stripInBoundsConstantOffsets();
424 const Value *stripInBoundsConstantOffsets() const {
425 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
428 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
430 /// Stores the resulting constant offset stripped into the APInt provided.
431 /// The provided APInt will be extended or truncated as needed to be the
432 /// correct bitwidth for an offset of this pointer type.
434 /// If this is called on a non-pointer value, it returns 'this'.
435 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
437 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
438 APInt &Offset) const {
439 return const_cast<Value *>(this)
440 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
443 /// \brief Strip off pointer casts and inbounds GEPs.
445 /// Returns the original pointer value. If this is called on a non-pointer
446 /// value, it returns 'this'.
447 Value *stripInBoundsOffsets();
448 const Value *stripInBoundsOffsets() const {
449 return const_cast<Value*>(this)->stripInBoundsOffsets();
452 /// \brief Translate PHI node to its predecessor from the given basic block.
454 /// If this value is a PHI node with CurBB as its parent, return the value in
455 /// the PHI node corresponding to PredBB. If not, return ourself. This is
456 /// useful if you want to know the value something has in a predecessor
458 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
460 const Value *DoPHITranslation(const BasicBlock *CurBB,
461 const BasicBlock *PredBB) const{
462 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
465 /// \brief The maximum alignment for instructions.
467 /// This is the greatest alignment value supported by load, store, and alloca
468 /// instructions, and global values.
469 static const unsigned MaxAlignmentExponent = 29;
470 static const unsigned MaximumAlignment = 1u << MaxAlignmentExponent;
472 /// \brief Mutate the type of this Value to be of the specified type.
474 /// Note that this is an extremely dangerous operation which can create
475 /// completely invalid IR very easily. It is strongly recommended that you
476 /// recreate IR objects with the right types instead of mutating them in
478 void mutateType(Type *Ty) {
482 /// \brief Sort the use-list.
484 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
485 /// expected to compare two \a Use references.
486 template <class Compare> void sortUseList(Compare Cmp);
488 /// \brief Reverse the use-list.
489 void reverseUseList();
492 /// \brief Merge two lists together.
494 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
495 /// "equal" items from L before items from R.
497 /// \return the first element in the list.
499 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
500 template <class Compare>
501 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
503 mergeUseListsImpl(L, R, &Merged, Cmp);
507 /// \brief Tail-recursive helper for \a mergeUseLists().
509 /// \param[out] Next the first element in the list.
510 template <class Compare>
511 static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
514 unsigned short getSubclassDataFromValue() const { return SubclassData; }
515 void setValueSubclassData(unsigned short D) { SubclassData = D; }
518 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
523 void Use::set(Value *V) {
524 if (Val) removeFromList();
526 if (V) V->addUse(*this);
529 template <class Compare> void Value::sortUseList(Compare Cmp) {
530 if (!UseList || !UseList->Next)
531 // No need to sort 0 or 1 uses.
534 // Note: this function completely ignores Prev pointers until the end when
535 // they're fixed en masse.
537 // Create a binomial vector of sorted lists, visiting uses one at a time and
538 // merging lists as necessary.
539 const unsigned MaxSlots = 32;
540 Use *Slots[MaxSlots];
542 // Collect the first use, turning it into a single-item list.
543 Use *Next = UseList->Next;
544 UseList->Next = nullptr;
545 unsigned NumSlots = 1;
548 // Collect all but the last use.
551 Next = Current->Next;
553 // Turn Current into a single-item list.
554 Current->Next = nullptr;
556 // Save Current in the first available slot, merging on collisions.
558 for (I = 0; I < NumSlots; ++I) {
562 // Merge two lists, doubling the size of Current and emptying slot I.
564 // Since the uses in Slots[I] originally preceded those in Current, send
565 // Slots[I] in as the left parameter to maintain a stable sort.
566 Current = mergeUseLists(Slots[I], Current, Cmp);
569 // Check if this is a new slot.
572 assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
575 // Found an open slot.
579 // Merge all the lists together.
580 assert(Next && "Expected one more Use");
581 assert(!Next->Next && "Expected only one Use");
583 for (unsigned I = 0; I < NumSlots; ++I)
585 // Since the uses in Slots[I] originally preceded those in UseList, send
586 // Slots[I] in as the left parameter to maintain a stable sort.
587 UseList = mergeUseLists(Slots[I], UseList, Cmp);
589 // Fix the Prev pointers.
590 for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
596 template <class Compare>
597 void Value::mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp) {
608 mergeUseListsImpl(L, R->Next, &R->Next, Cmp);
612 mergeUseListsImpl(L->Next, R, &L->Next, Cmp);
615 // isa - Provide some specializations of isa so that we don't have to include
616 // the subtype header files to test to see if the value is a subclass...
618 template <> struct isa_impl<Constant, Value> {
619 static inline bool doit(const Value &Val) {
620 return Val.getValueID() >= Value::ConstantFirstVal &&
621 Val.getValueID() <= Value::ConstantLastVal;
625 template <> struct isa_impl<Argument, Value> {
626 static inline bool doit (const Value &Val) {
627 return Val.getValueID() == Value::ArgumentVal;
631 template <> struct isa_impl<InlineAsm, Value> {
632 static inline bool doit(const Value &Val) {
633 return Val.getValueID() == Value::InlineAsmVal;
637 template <> struct isa_impl<Instruction, Value> {
638 static inline bool doit(const Value &Val) {
639 return Val.getValueID() >= Value::InstructionVal;
643 template <> struct isa_impl<BasicBlock, Value> {
644 static inline bool doit(const Value &Val) {
645 return Val.getValueID() == Value::BasicBlockVal;
649 template <> struct isa_impl<Function, Value> {
650 static inline bool doit(const Value &Val) {
651 return Val.getValueID() == Value::FunctionVal;
655 template <> struct isa_impl<GlobalVariable, Value> {
656 static inline bool doit(const Value &Val) {
657 return Val.getValueID() == Value::GlobalVariableVal;
661 template <> struct isa_impl<GlobalAlias, Value> {
662 static inline bool doit(const Value &Val) {
663 return Val.getValueID() == Value::GlobalAliasVal;
667 template <> struct isa_impl<GlobalValue, Value> {
668 static inline bool doit(const Value &Val) {
669 return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
673 template <> struct isa_impl<GlobalObject, Value> {
674 static inline bool doit(const Value &Val) {
675 return isa<GlobalVariable>(Val) || isa<Function>(Val);
679 // Value* is only 4-byte aligned.
681 class PointerLikeTypeTraits<Value*> {
684 static inline void *getAsVoidPointer(PT P) { return P; }
685 static inline PT getFromVoidPointer(void *P) {
686 return static_cast<PT>(P);
688 enum { NumLowBitsAvailable = 2 };
691 // Create wrappers for C Binding types (see CBindingWrapping.h).
692 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
694 /* Specialized opaque value conversions.
696 inline Value **unwrap(LLVMValueRef *Vals) {
697 return reinterpret_cast<Value**>(Vals);
701 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
703 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
707 return reinterpret_cast<T**>(Vals);
710 inline LLVMValueRef *wrap(const Value **Vals) {
711 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
714 } // End llvm namespace