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 NameAndIsUsedByMD.
73 friend class ValueHandleBase;
74 PointerIntPair<ValueName *, 1> NameAndIsUsedByMD;
76 const unsigned char SubclassID; // Subclass identifier (for isa/dyn_cast)
77 unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this?
79 /// \brief Hold subclass data that can be dropped.
81 /// This member is similar to SubclassData, however it is for holding
82 /// information which may be used to aid optimization, but which may be
83 /// cleared to zero without affecting conservative interpretation.
84 unsigned char SubclassOptionalData : 7;
87 /// \brief Hold arbitrary subclass data.
89 /// This member is defined by this class, but is not used for anything.
90 /// Subclasses can use it to hold whatever state they find useful. This
91 /// field is initialized to zero by the ctor.
92 unsigned short SubclassData;
95 /// \brief The number of operands in the subclass.
97 /// This member is defined by this class, but not used for anything.
98 /// Subclasses can use it to store their number of operands, if they have
101 /// This is stored here to save space in User on 64-bit hosts. Since most
102 /// instances of Value have operands, 32-bit hosts aren't significantly
104 unsigned NumOperands;
107 template <typename UseT> // UseT == 'Use' or 'const Use'
108 class use_iterator_impl
109 : public std::iterator<std::forward_iterator_tag, UseT *, ptrdiff_t> {
110 typedef std::iterator<std::forward_iterator_tag, UseT *, ptrdiff_t> super;
113 explicit use_iterator_impl(UseT *u) : U(u) {}
117 typedef typename super::reference reference;
118 typedef typename super::pointer pointer;
120 use_iterator_impl() : U() {}
122 bool operator==(const use_iterator_impl &x) const { return U == x.U; }
123 bool operator!=(const use_iterator_impl &x) const { return !operator==(x); }
125 use_iterator_impl &operator++() { // Preincrement
126 assert(U && "Cannot increment end iterator!");
130 use_iterator_impl operator++(int) { // Postincrement
136 UseT &operator*() const {
137 assert(U && "Cannot dereference end iterator!");
141 UseT *operator->() const { return &operator*(); }
143 operator use_iterator_impl<const UseT>() const {
144 return use_iterator_impl<const UseT>(U);
148 template <typename UserTy> // UserTy == 'User' or 'const User'
149 class user_iterator_impl
150 : public std::iterator<std::forward_iterator_tag, UserTy *, ptrdiff_t> {
151 typedef std::iterator<std::forward_iterator_tag, UserTy *, ptrdiff_t> super;
153 use_iterator_impl<Use> UI;
154 explicit user_iterator_impl(Use *U) : UI(U) {}
158 typedef typename super::reference reference;
159 typedef typename super::pointer pointer;
161 user_iterator_impl() {}
163 bool operator==(const user_iterator_impl &x) const { return UI == x.UI; }
164 bool operator!=(const user_iterator_impl &x) const { return !operator==(x); }
166 /// \brief Returns true if this iterator is equal to user_end() on the value.
167 bool atEnd() const { return *this == user_iterator_impl(); }
169 user_iterator_impl &operator++() { // Preincrement
173 user_iterator_impl operator++(int) { // Postincrement
179 // Retrieve a pointer to the current User.
180 UserTy *operator*() const {
181 return UI->getUser();
184 UserTy *operator->() const { return operator*(); }
186 operator user_iterator_impl<const UserTy>() const {
187 return user_iterator_impl<const UserTy>(*UI);
190 Use &getUse() const { return *UI; }
192 /// \brief Return the operand # of this use in its User.
194 /// FIXME: Replace all callers with a direct call to Use::getOperandNo.
195 unsigned getOperandNo() const { return UI->getOperandNo(); }
198 void operator=(const Value &) LLVM_DELETED_FUNCTION;
199 Value(const Value &) LLVM_DELETED_FUNCTION;
202 Value(Type *Ty, unsigned scid);
206 /// \brief Support for debugging, callable in GDB: V->dump()
209 /// \brief Implement operator<< on Value.
210 void print(raw_ostream &O) const;
212 /// \brief Print the name of this Value out to the specified raw_ostream.
214 /// This is useful when you just want to print 'int %reg126', not the
215 /// instruction that generated it. If you specify a Module for context, then
216 /// even constanst get pretty-printed; for example, the type of a null
217 /// pointer is printed symbolically.
218 void printAsOperand(raw_ostream &O, bool PrintType = true,
219 const Module *M = nullptr) const;
221 /// \brief All values are typed, get the type of this value.
222 Type *getType() const { return VTy; }
224 /// \brief All values hold a context through their type.
225 LLVMContext &getContext() const;
227 // \brief All values can potentially be named.
228 bool hasName() const { return getValueName() != nullptr; }
229 ValueName *getValueName() const { return NameAndIsUsedByMD.getPointer(); }
230 void setValueName(ValueName *VN) { NameAndIsUsedByMD.setPointer(VN); }
233 void destroyValueName();
236 /// \brief Return a constant reference to the value's name.
238 /// This is cheap and guaranteed to return the same reference as long as the
239 /// value is not modified.
240 StringRef getName() const;
242 /// \brief Change the name of the value.
244 /// Choose a new unique name if the provided name is taken.
246 /// \param Name The new name; or "" if the value's name should be removed.
247 void setName(const Twine &Name);
250 /// \brief Transfer the name from V to this value.
252 /// After taking V's name, sets V's name to empty.
254 /// \note It is an error to call V->takeName(V).
255 void takeName(Value *V);
257 /// \brief Change all uses of this to point to a new Value.
259 /// Go through the uses list for this definition and make each use point to
260 /// "V" instead of "this". After this completes, 'this's use list is
261 /// guaranteed to be empty.
262 void replaceAllUsesWith(Value *V);
264 /// replaceUsesOutsideBlock - Go through the uses list for this definition and
265 /// make each use point to "V" instead of "this" when the use is outside the
266 /// block. 'This's use list is expected to have at least one element.
267 /// Unlike replaceAllUsesWith this function does not support basic block
268 /// values or constant users.
269 void replaceUsesOutsideBlock(Value *V, BasicBlock *BB);
271 //----------------------------------------------------------------------
272 // Methods for handling the chain of uses of this Value.
274 bool use_empty() const { return UseList == nullptr; }
276 typedef use_iterator_impl<Use> use_iterator;
277 typedef use_iterator_impl<const Use> const_use_iterator;
278 use_iterator use_begin() { return use_iterator(UseList); }
279 const_use_iterator use_begin() const { return const_use_iterator(UseList); }
280 use_iterator use_end() { return use_iterator(); }
281 const_use_iterator use_end() const { return const_use_iterator(); }
282 iterator_range<use_iterator> uses() {
283 return iterator_range<use_iterator>(use_begin(), use_end());
285 iterator_range<const_use_iterator> uses() const {
286 return iterator_range<const_use_iterator>(use_begin(), use_end());
289 typedef user_iterator_impl<User> user_iterator;
290 typedef user_iterator_impl<const User> const_user_iterator;
291 user_iterator user_begin() { return user_iterator(UseList); }
292 const_user_iterator user_begin() const { return const_user_iterator(UseList); }
293 user_iterator user_end() { return user_iterator(); }
294 const_user_iterator user_end() const { return const_user_iterator(); }
295 User *user_back() { return *user_begin(); }
296 const User *user_back() const { return *user_begin(); }
297 iterator_range<user_iterator> users() {
298 return iterator_range<user_iterator>(user_begin(), user_end());
300 iterator_range<const_user_iterator> users() const {
301 return iterator_range<const_user_iterator>(user_begin(), user_end());
304 /// \brief Return true if there is exactly one user of this value.
306 /// This is specialized because it is a common request and does not require
307 /// traversing the whole use list.
308 bool hasOneUse() const {
309 const_use_iterator I = use_begin(), E = use_end();
310 if (I == E) return false;
314 /// \brief Return true if this Value has exactly N users.
315 bool hasNUses(unsigned N) const;
317 /// \brief Return true if this value has N users or more.
319 /// This is logically equivalent to getNumUses() >= N.
320 bool hasNUsesOrMore(unsigned N) const;
322 /// \brief Check if this value is used in the specified basic block.
323 bool isUsedInBasicBlock(const BasicBlock *BB) const;
325 /// \brief This method computes the number of uses of this Value.
327 /// This is a linear time operation. Use hasOneUse, hasNUses, or
328 /// hasNUsesOrMore to check for specific values.
329 unsigned getNumUses() const;
331 /// \brief This method should only be used by the Use class.
332 void addUse(Use &U) { U.addToList(&UseList); }
334 /// \brief Concrete subclass of this.
336 /// An enumeration for keeping track of the concrete subclass of Value that
337 /// is actually instantiated. Values of this enumeration are kept in the
338 /// Value classes SubclassID field. They are used for concrete type
341 ArgumentVal, // This is an instance of Argument
342 BasicBlockVal, // This is an instance of BasicBlock
343 FunctionVal, // This is an instance of Function
344 GlobalAliasVal, // This is an instance of GlobalAlias
345 GlobalVariableVal, // This is an instance of GlobalVariable
346 UndefValueVal, // This is an instance of UndefValue
347 BlockAddressVal, // This is an instance of BlockAddress
348 ConstantExprVal, // This is an instance of ConstantExpr
349 ConstantAggregateZeroVal, // This is an instance of ConstantAggregateZero
350 ConstantDataArrayVal, // This is an instance of ConstantDataArray
351 ConstantDataVectorVal, // This is an instance of ConstantDataVector
352 ConstantIntVal, // This is an instance of ConstantInt
353 ConstantFPVal, // This is an instance of ConstantFP
354 ConstantArrayVal, // This is an instance of ConstantArray
355 ConstantStructVal, // This is an instance of ConstantStruct
356 ConstantVectorVal, // This is an instance of ConstantVector
357 ConstantPointerNullVal, // This is an instance of ConstantPointerNull
358 MetadataAsValueVal, // This is an instance of MetadataAsValue
359 InlineAsmVal, // This is an instance of InlineAsm
360 InstructionVal, // This is an instance of Instruction
361 // Enum values starting at InstructionVal are used for Instructions;
362 // don't add new values here!
365 ConstantFirstVal = FunctionVal,
366 ConstantLastVal = ConstantPointerNullVal
369 /// \brief Return an ID for the concrete type of this object.
371 /// This is used to implement the classof checks. This should not be used
372 /// for any other purpose, as the values may change as LLVM evolves. Also,
373 /// note that for instructions, the Instruction's opcode is added to
374 /// InstructionVal. So this means three things:
375 /// # there is no value with code InstructionVal (no opcode==0).
376 /// # there are more possible values for the value type than in ValueTy enum.
377 /// # the InstructionVal enumerator must be the highest valued enumerator in
378 /// the ValueTy enum.
379 unsigned getValueID() const {
383 /// \brief Return the raw optional flags value contained in this value.
385 /// This should only be used when testing two Values for equivalence.
386 unsigned getRawSubclassOptionalData() const {
387 return SubclassOptionalData;
390 /// \brief Clear the optional flags contained in this value.
391 void clearSubclassOptionalData() {
392 SubclassOptionalData = 0;
395 /// \brief Check the optional flags for equality.
396 bool hasSameSubclassOptionalData(const Value *V) const {
397 return SubclassOptionalData == V->SubclassOptionalData;
400 /// \brief Clear any optional flags not set in the given Value.
401 void intersectOptionalDataWith(const Value *V) {
402 SubclassOptionalData &= V->SubclassOptionalData;
405 /// \brief Return true if there is a value handle associated with this value.
406 bool hasValueHandle() const { return HasValueHandle; }
408 /// \brief Return true if there is metadata referencing this value.
409 bool isUsedByMetadata() const { return NameAndIsUsedByMD.getInt(); }
411 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
413 /// Returns the original uncasted value. If this is called on a non-pointer
414 /// value, it returns 'this'.
415 Value *stripPointerCasts();
416 const Value *stripPointerCasts() const {
417 return const_cast<Value*>(this)->stripPointerCasts();
420 /// \brief Strip off pointer casts and all-zero GEPs.
422 /// Returns the original uncasted value. If this is called on a non-pointer
423 /// value, it returns 'this'.
424 Value *stripPointerCastsNoFollowAliases();
425 const Value *stripPointerCastsNoFollowAliases() const {
426 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
429 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
431 /// Returns the original pointer value. If this is called on a non-pointer
432 /// value, it returns 'this'.
433 Value *stripInBoundsConstantOffsets();
434 const Value *stripInBoundsConstantOffsets() const {
435 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
438 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
440 /// Stores the resulting constant offset stripped into the APInt provided.
441 /// The provided APInt will be extended or truncated as needed to be the
442 /// correct bitwidth for an offset of this pointer type.
444 /// If this is called on a non-pointer value, it returns 'this'.
445 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
447 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
448 APInt &Offset) const {
449 return const_cast<Value *>(this)
450 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
453 /// \brief Strip off pointer casts and inbounds GEPs.
455 /// Returns the original pointer value. If this is called on a non-pointer
456 /// value, it returns 'this'.
457 Value *stripInBoundsOffsets();
458 const Value *stripInBoundsOffsets() const {
459 return const_cast<Value*>(this)->stripInBoundsOffsets();
462 /// \brief Check if this is always a dereferenceable pointer.
464 /// Test if this value is always a pointer to allocated and suitably aligned
465 /// memory for a simple load or store.
466 bool isDereferenceablePointer(const DataLayout *DL = nullptr) const;
468 /// \brief Translate PHI node to its predecessor from the given basic block.
470 /// If this value is a PHI node with CurBB as its parent, return the value in
471 /// the PHI node corresponding to PredBB. If not, return ourself. This is
472 /// useful if you want to know the value something has in a predecessor
474 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
476 const Value *DoPHITranslation(const BasicBlock *CurBB,
477 const BasicBlock *PredBB) const{
478 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
481 /// \brief The maximum alignment for instructions.
483 /// This is the greatest alignment value supported by load, store, and alloca
484 /// instructions, and global values.
485 static const unsigned MaximumAlignment = 1u << 29;
487 /// \brief Mutate the type of this Value to be of the specified type.
489 /// Note that this is an extremely dangerous operation which can create
490 /// completely invalid IR very easily. It is strongly recommended that you
491 /// recreate IR objects with the right types instead of mutating them in
493 void mutateType(Type *Ty) {
497 /// \brief Sort the use-list.
499 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
500 /// expected to compare two \a Use references.
501 template <class Compare> void sortUseList(Compare Cmp);
503 /// \brief Reverse the use-list.
504 void reverseUseList();
507 /// \brief Merge two lists together.
509 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
510 /// "equal" items from L before items from R.
512 /// \return the first element in the list.
514 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
515 template <class Compare>
516 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
518 mergeUseListsImpl(L, R, &Merged, Cmp);
522 /// \brief Tail-recursive helper for \a mergeUseLists().
524 /// \param[out] Next the first element in the list.
525 template <class Compare>
526 static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
529 unsigned short getSubclassDataFromValue() const { return SubclassData; }
530 void setValueSubclassData(unsigned short D) { SubclassData = D; }
533 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
538 void Use::set(Value *V) {
539 if (Val) removeFromList();
541 if (V) V->addUse(*this);
544 template <class Compare> void Value::sortUseList(Compare Cmp) {
545 if (!UseList || !UseList->Next)
546 // No need to sort 0 or 1 uses.
549 // Note: this function completely ignores Prev pointers until the end when
550 // they're fixed en masse.
552 // Create a binomial vector of sorted lists, visiting uses one at a time and
553 // merging lists as necessary.
554 const unsigned MaxSlots = 32;
555 Use *Slots[MaxSlots];
557 // Collect the first use, turning it into a single-item list.
558 Use *Next = UseList->Next;
559 UseList->Next = nullptr;
560 unsigned NumSlots = 1;
563 // Collect all but the last use.
566 Next = Current->Next;
568 // Turn Current into a single-item list.
569 Current->Next = nullptr;
571 // Save Current in the first available slot, merging on collisions.
573 for (I = 0; I < NumSlots; ++I) {
577 // Merge two lists, doubling the size of Current and emptying slot I.
579 // Since the uses in Slots[I] originally preceded those in Current, send
580 // Slots[I] in as the left parameter to maintain a stable sort.
581 Current = mergeUseLists(Slots[I], Current, Cmp);
584 // Check if this is a new slot.
587 assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
590 // Found an open slot.
594 // Merge all the lists together.
595 assert(Next && "Expected one more Use");
596 assert(!Next->Next && "Expected only one Use");
598 for (unsigned I = 0; I < NumSlots; ++I)
600 // Since the uses in Slots[I] originally preceded those in UseList, send
601 // Slots[I] in as the left parameter to maintain a stable sort.
602 UseList = mergeUseLists(Slots[I], UseList, Cmp);
604 // Fix the Prev pointers.
605 for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
611 template <class Compare>
612 void Value::mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp) {
623 mergeUseListsImpl(L, R->Next, &R->Next, Cmp);
627 mergeUseListsImpl(L->Next, R, &L->Next, Cmp);
630 // isa - Provide some specializations of isa so that we don't have to include
631 // the subtype header files to test to see if the value is a subclass...
633 template <> struct isa_impl<Constant, Value> {
634 static inline bool doit(const Value &Val) {
635 return Val.getValueID() >= Value::ConstantFirstVal &&
636 Val.getValueID() <= Value::ConstantLastVal;
640 template <> struct isa_impl<Argument, Value> {
641 static inline bool doit (const Value &Val) {
642 return Val.getValueID() == Value::ArgumentVal;
646 template <> struct isa_impl<InlineAsm, Value> {
647 static inline bool doit(const Value &Val) {
648 return Val.getValueID() == Value::InlineAsmVal;
652 template <> struct isa_impl<Instruction, Value> {
653 static inline bool doit(const Value &Val) {
654 return Val.getValueID() >= Value::InstructionVal;
658 template <> struct isa_impl<BasicBlock, Value> {
659 static inline bool doit(const Value &Val) {
660 return Val.getValueID() == Value::BasicBlockVal;
664 template <> struct isa_impl<Function, Value> {
665 static inline bool doit(const Value &Val) {
666 return Val.getValueID() == Value::FunctionVal;
670 template <> struct isa_impl<GlobalVariable, Value> {
671 static inline bool doit(const Value &Val) {
672 return Val.getValueID() == Value::GlobalVariableVal;
676 template <> struct isa_impl<GlobalAlias, Value> {
677 static inline bool doit(const Value &Val) {
678 return Val.getValueID() == Value::GlobalAliasVal;
682 template <> struct isa_impl<GlobalValue, Value> {
683 static inline bool doit(const Value &Val) {
684 return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
688 template <> struct isa_impl<GlobalObject, Value> {
689 static inline bool doit(const Value &Val) {
690 return isa<GlobalVariable>(Val) || isa<Function>(Val);
694 // Value* is only 4-byte aligned.
696 class PointerLikeTypeTraits<Value*> {
699 static inline void *getAsVoidPointer(PT P) { return P; }
700 static inline PT getFromVoidPointer(void *P) {
701 return static_cast<PT>(P);
703 enum { NumLowBitsAvailable = 2 };
706 // Create wrappers for C Binding types (see CBindingWrapping.h).
707 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
709 /* Specialized opaque value conversions.
711 inline Value **unwrap(LLVMValueRef *Vals) {
712 return reinterpret_cast<Value**>(Vals);
716 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
718 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
722 return reinterpret_cast<T**>(Vals);
725 inline LLVMValueRef *wrap(const Value **Vals) {
726 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
729 } // End llvm namespace