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/ADT/iterator_range.h"
18 #include "llvm/IR/Use.h"
19 #include "llvm/Support/CBindingWrapping.h"
20 #include "llvm/Support/Casting.h"
21 #include "llvm/Support/Compiler.h"
27 class AssemblyAnnotationWriter;
40 class ModuleSlotTracker;
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
104 /// Note, this should *NOT* be used directly by any class other than User.
105 /// User uses this value to find the Use list.
106 enum : unsigned { NumUserOperandsBits = 28 };
107 unsigned NumUserOperands : NumUserOperandsBits;
111 bool HasHungOffUses : 1;
112 bool HasDescriptor : 1;
115 template <typename UseT> // UseT == 'Use' or 'const Use'
116 class use_iterator_impl
117 : public std::iterator<std::forward_iterator_tag, UseT *> {
119 explicit use_iterator_impl(UseT *u) : U(u) {}
123 use_iterator_impl() : U() {}
125 bool operator==(const use_iterator_impl &x) const { return U == x.U; }
126 bool operator!=(const use_iterator_impl &x) const { return !operator==(x); }
128 use_iterator_impl &operator++() { // Preincrement
129 assert(U && "Cannot increment end iterator!");
133 use_iterator_impl operator++(int) { // Postincrement
139 UseT &operator*() const {
140 assert(U && "Cannot dereference end iterator!");
144 UseT *operator->() const { return &operator*(); }
146 operator use_iterator_impl<const UseT>() const {
147 return use_iterator_impl<const UseT>(U);
151 template <typename UserTy> // UserTy == 'User' or 'const User'
152 class user_iterator_impl
153 : public std::iterator<std::forward_iterator_tag, UserTy *> {
154 use_iterator_impl<Use> UI;
155 explicit user_iterator_impl(Use *U) : UI(U) {}
159 user_iterator_impl() {}
161 bool operator==(const user_iterator_impl &x) const { return UI == x.UI; }
162 bool operator!=(const user_iterator_impl &x) const { return !operator==(x); }
164 /// \brief Returns true if this iterator is equal to user_end() on the value.
165 bool atEnd() const { return *this == user_iterator_impl(); }
167 user_iterator_impl &operator++() { // Preincrement
171 user_iterator_impl operator++(int) { // Postincrement
177 // Retrieve a pointer to the current User.
178 UserTy *operator*() const {
179 return UI->getUser();
182 UserTy *operator->() const { return operator*(); }
184 operator user_iterator_impl<const UserTy>() const {
185 return user_iterator_impl<const UserTy>(*UI);
188 Use &getUse() const { return *UI; }
191 void operator=(const Value &) = delete;
192 Value(const Value &) = delete;
195 Value(Type *Ty, unsigned scid);
199 /// \brief Support for debugging, callable in GDB: V->dump()
202 /// \brief Implement operator<< on Value.
204 void print(raw_ostream &O, bool IsForDebug = false) const;
205 void print(raw_ostream &O, ModuleSlotTracker &MST,
206 bool IsForDebug = false) const;
209 /// \brief Print the name of this Value out to the specified raw_ostream.
211 /// This is useful when you just want to print 'int %reg126', not the
212 /// instruction that generated it. If you specify a Module for context, then
213 /// even constanst get pretty-printed; for example, the type of a null
214 /// pointer is printed symbolically.
216 void printAsOperand(raw_ostream &O, bool PrintType = true,
217 const Module *M = nullptr) const;
218 void printAsOperand(raw_ostream &O, bool PrintType,
219 ModuleSlotTracker &MST) 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 HasName; }
230 ValueName *getValueName() const;
231 void setValueName(ValueName *VN);
234 void destroyValueName();
235 void setNameImpl(const Twine &Name);
238 /// \brief Return a constant reference to the value's name.
240 /// This is cheap and guaranteed to return the same reference as long as the
241 /// value is not modified.
242 StringRef getName() const;
244 /// \brief Change the name of the value.
246 /// Choose a new unique name if the provided name is taken.
248 /// \param Name The new name; or "" if the value's name should be removed.
249 void setName(const Twine &Name);
252 /// \brief Transfer the name from V to this value.
254 /// After taking V's name, sets V's name to empty.
256 /// \note It is an error to call V->takeName(V).
257 void takeName(Value *V);
259 /// \brief Change all uses of this to point to a new Value.
261 /// Go through the uses list for this definition and make each use point to
262 /// "V" instead of "this". After this completes, 'this's use list is
263 /// guaranteed to be empty.
264 void replaceAllUsesWith(Value *V);
266 /// replaceUsesOutsideBlock - Go through the uses list for this definition and
267 /// make each use point to "V" instead of "this" when the use is outside the
268 /// block. 'This's use list is expected to have at least one element.
269 /// Unlike replaceAllUsesWith this function does not support basic block
270 /// values or constant users.
271 void replaceUsesOutsideBlock(Value *V, BasicBlock *BB);
273 //----------------------------------------------------------------------
274 // Methods for handling the chain of uses of this Value.
276 bool use_empty() const { return UseList == nullptr; }
278 typedef use_iterator_impl<Use> use_iterator;
279 typedef use_iterator_impl<const Use> const_use_iterator;
280 use_iterator use_begin() { return use_iterator(UseList); }
281 const_use_iterator use_begin() const { return const_use_iterator(UseList); }
282 use_iterator use_end() { return use_iterator(); }
283 const_use_iterator use_end() const { return const_use_iterator(); }
284 iterator_range<use_iterator> uses() {
285 return make_range(use_begin(), use_end());
287 iterator_range<const_use_iterator> uses() const {
288 return make_range(use_begin(), use_end());
291 bool user_empty() const { return UseList == nullptr; }
293 typedef user_iterator_impl<User> user_iterator;
294 typedef user_iterator_impl<const User> const_user_iterator;
295 user_iterator user_begin() { return user_iterator(UseList); }
296 const_user_iterator user_begin() const {
297 return const_user_iterator(UseList);
299 user_iterator user_end() { return user_iterator(); }
300 const_user_iterator user_end() const { return const_user_iterator(); }
301 User *user_back() { return *user_begin(); }
302 const User *user_back() const { return *user_begin(); }
303 iterator_range<user_iterator> users() {
304 return make_range(user_begin(), user_end());
306 iterator_range<const_user_iterator> users() const {
307 return make_range(user_begin(), user_end());
310 /// \brief Return true if there is exactly one user of this value.
312 /// This is specialized because it is a common request and does not require
313 /// traversing the whole use list.
314 bool hasOneUse() const {
315 const_use_iterator I = use_begin(), E = use_end();
316 if (I == E) return false;
320 /// \brief Return true if this Value has exactly N users.
321 bool hasNUses(unsigned N) const;
323 /// \brief Return true if this value has N users or more.
325 /// This is logically equivalent to getNumUses() >= N.
326 bool hasNUsesOrMore(unsigned N) const;
328 /// \brief Check if this value is used in the specified basic block.
329 bool isUsedInBasicBlock(const BasicBlock *BB) const;
331 /// \brief This method computes the number of uses of this Value.
333 /// This is a linear time operation. Use hasOneUse, hasNUses, or
334 /// hasNUsesOrMore to check for specific values.
335 unsigned getNumUses() const;
337 /// \brief This method should only be used by the Use class.
338 void addUse(Use &U) { U.addToList(&UseList); }
340 /// \brief Concrete subclass of this.
342 /// An enumeration for keeping track of the concrete subclass of Value that
343 /// is actually instantiated. Values of this enumeration are kept in the
344 /// Value classes SubclassID field. They are used for concrete type
347 #define HANDLE_VALUE(Name) Name##Val,
348 #include "llvm/IR/Value.def"
351 #define HANDLE_CONSTANT_MARKER(Marker, Constant) Marker = Constant##Val,
352 #include "llvm/IR/Value.def"
355 /// \brief Return an ID for the concrete type of this object.
357 /// This is used to implement the classof checks. This should not be used
358 /// for any other purpose, as the values may change as LLVM evolves. Also,
359 /// note that for instructions, the Instruction's opcode is added to
360 /// InstructionVal. So this means three things:
361 /// # there is no value with code InstructionVal (no opcode==0).
362 /// # there are more possible values for the value type than in ValueTy enum.
363 /// # the InstructionVal enumerator must be the highest valued enumerator in
364 /// the ValueTy enum.
365 unsigned getValueID() const {
369 /// \brief Return the raw optional flags value contained in this value.
371 /// This should only be used when testing two Values for equivalence.
372 unsigned getRawSubclassOptionalData() const {
373 return SubclassOptionalData;
376 /// \brief Clear the optional flags contained in this value.
377 void clearSubclassOptionalData() {
378 SubclassOptionalData = 0;
381 /// \brief Check the optional flags for equality.
382 bool hasSameSubclassOptionalData(const Value *V) const {
383 return SubclassOptionalData == V->SubclassOptionalData;
386 /// \brief Clear any optional flags not set in the given Value.
387 void intersectOptionalDataWith(const Value *V) {
388 SubclassOptionalData &= V->SubclassOptionalData;
391 /// \brief Return true if there is a value handle associated with this value.
392 bool hasValueHandle() const { return HasValueHandle; }
394 /// \brief Return true if there is metadata referencing this value.
395 bool isUsedByMetadata() const { return IsUsedByMD; }
397 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
399 /// Returns the original uncasted value. If this is called on a non-pointer
400 /// value, it returns 'this'.
401 Value *stripPointerCasts();
402 const Value *stripPointerCasts() const {
403 return const_cast<Value*>(this)->stripPointerCasts();
406 /// \brief Strip off pointer casts and all-zero GEPs.
408 /// Returns the original uncasted value. If this is called on a non-pointer
409 /// value, it returns 'this'.
410 Value *stripPointerCastsNoFollowAliases();
411 const Value *stripPointerCastsNoFollowAliases() const {
412 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
415 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
417 /// Returns the original pointer value. If this is called on a non-pointer
418 /// value, it returns 'this'.
419 Value *stripInBoundsConstantOffsets();
420 const Value *stripInBoundsConstantOffsets() const {
421 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
424 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
426 /// Stores the resulting constant offset stripped into the APInt provided.
427 /// The provided APInt will be extended or truncated as needed to be the
428 /// correct bitwidth for an offset of this pointer type.
430 /// If this is called on a non-pointer value, it returns 'this'.
431 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
433 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
434 APInt &Offset) const {
435 return const_cast<Value *>(this)
436 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
439 /// \brief Strip off pointer casts and inbounds GEPs.
441 /// Returns the original pointer value. If this is called on a non-pointer
442 /// value, it returns 'this'.
443 Value *stripInBoundsOffsets();
444 const Value *stripInBoundsOffsets() const {
445 return const_cast<Value*>(this)->stripInBoundsOffsets();
448 /// \brief Translate PHI node to its predecessor from the given basic block.
450 /// If this value is a PHI node with CurBB as its parent, return the value in
451 /// the PHI node corresponding to PredBB. If not, return ourself. This is
452 /// useful if you want to know the value something has in a predecessor
454 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
456 const Value *DoPHITranslation(const BasicBlock *CurBB,
457 const BasicBlock *PredBB) const{
458 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
461 /// \brief The maximum alignment for instructions.
463 /// This is the greatest alignment value supported by load, store, and alloca
464 /// instructions, and global values.
465 static const unsigned MaxAlignmentExponent = 29;
466 static const unsigned MaximumAlignment = 1u << MaxAlignmentExponent;
468 /// \brief Mutate the type of this Value to be of the specified type.
470 /// Note that this is an extremely dangerous operation which can create
471 /// completely invalid IR very easily. It is strongly recommended that you
472 /// recreate IR objects with the right types instead of mutating them in
474 void mutateType(Type *Ty) {
478 /// \brief Sort the use-list.
480 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
481 /// expected to compare two \a Use references.
482 template <class Compare> void sortUseList(Compare Cmp);
484 /// \brief Reverse the use-list.
485 void reverseUseList();
488 /// \brief Merge two lists together.
490 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
491 /// "equal" items from L before items from R.
493 /// \return the first element in the list.
495 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
496 template <class Compare>
497 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
499 Use **Next = &Merged;
524 /// \brief Tail-recursive helper for \a mergeUseLists().
526 /// \param[out] Next the first element in the list.
527 template <class Compare>
528 static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
531 unsigned short getSubclassDataFromValue() const { return SubclassData; }
532 void setValueSubclassData(unsigned short D) { SubclassData = D; }
535 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
540 void Use::set(Value *V) {
541 if (Val) removeFromList();
543 if (V) V->addUse(*this);
546 template <class Compare> void Value::sortUseList(Compare Cmp) {
547 if (!UseList || !UseList->Next)
548 // No need to sort 0 or 1 uses.
551 // Note: this function completely ignores Prev pointers until the end when
552 // they're fixed en masse.
554 // Create a binomial vector of sorted lists, visiting uses one at a time and
555 // merging lists as necessary.
556 const unsigned MaxSlots = 32;
557 Use *Slots[MaxSlots];
559 // Collect the first use, turning it into a single-item list.
560 Use *Next = UseList->Next;
561 UseList->Next = nullptr;
562 unsigned NumSlots = 1;
565 // Collect all but the last use.
568 Next = Current->Next;
570 // Turn Current into a single-item list.
571 Current->Next = nullptr;
573 // Save Current in the first available slot, merging on collisions.
575 for (I = 0; I < NumSlots; ++I) {
579 // Merge two lists, doubling the size of Current and emptying slot I.
581 // Since the uses in Slots[I] originally preceded those in Current, send
582 // Slots[I] in as the left parameter to maintain a stable sort.
583 Current = mergeUseLists(Slots[I], Current, Cmp);
586 // Check if this is a new slot.
589 assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
592 // Found an open slot.
596 // Merge all the lists together.
597 assert(Next && "Expected one more Use");
598 assert(!Next->Next && "Expected only one Use");
600 for (unsigned I = 0; I < NumSlots; ++I)
602 // Since the uses in Slots[I] originally preceded those in UseList, send
603 // Slots[I] in as the left parameter to maintain a stable sort.
604 UseList = mergeUseLists(Slots[I], UseList, Cmp);
606 // Fix the Prev pointers.
607 for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
613 // isa - Provide some specializations of isa so that we don't have to include
614 // the subtype header files to test to see if the value is a subclass...
616 template <> struct isa_impl<Constant, Value> {
617 static inline bool doit(const Value &Val) {
618 return Val.getValueID() >= Value::ConstantFirstVal &&
619 Val.getValueID() <= Value::ConstantLastVal;
623 template <> struct isa_impl<Argument, Value> {
624 static inline bool doit (const Value &Val) {
625 return Val.getValueID() == Value::ArgumentVal;
629 template <> struct isa_impl<InlineAsm, Value> {
630 static inline bool doit(const Value &Val) {
631 return Val.getValueID() == Value::InlineAsmVal;
635 template <> struct isa_impl<Instruction, Value> {
636 static inline bool doit(const Value &Val) {
637 return Val.getValueID() >= Value::InstructionVal;
641 template <> struct isa_impl<BasicBlock, Value> {
642 static inline bool doit(const Value &Val) {
643 return Val.getValueID() == Value::BasicBlockVal;
647 template <> struct isa_impl<Function, Value> {
648 static inline bool doit(const Value &Val) {
649 return Val.getValueID() == Value::FunctionVal;
653 template <> struct isa_impl<GlobalVariable, Value> {
654 static inline bool doit(const Value &Val) {
655 return Val.getValueID() == Value::GlobalVariableVal;
659 template <> struct isa_impl<GlobalAlias, Value> {
660 static inline bool doit(const Value &Val) {
661 return Val.getValueID() == Value::GlobalAliasVal;
665 template <> struct isa_impl<GlobalValue, Value> {
666 static inline bool doit(const Value &Val) {
667 return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
671 template <> struct isa_impl<GlobalObject, Value> {
672 static inline bool doit(const Value &Val) {
673 return isa<GlobalVariable>(Val) || isa<Function>(Val);
677 // Value* is only 4-byte aligned.
679 class PointerLikeTypeTraits<Value*> {
682 static inline void *getAsVoidPointer(PT P) { return P; }
683 static inline PT getFromVoidPointer(void *P) {
684 return static_cast<PT>(P);
686 enum { NumLowBitsAvailable = 2 };
689 // Create wrappers for C Binding types (see CBindingWrapping.h).
690 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
692 /* Specialized opaque value conversions.
694 inline Value **unwrap(LLVMValueRef *Vals) {
695 return reinterpret_cast<Value**>(Vals);
699 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
701 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
705 return reinterpret_cast<T**>(Vals);
708 inline LLVMValueRef *wrap(const Value **Vals) {
709 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
712 } // End llvm namespace