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;
41 class ModuleSlotTracker;
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 ValueAsMetadata; // Allow access to IsUsedByMD.
74 friend class ValueHandleBase;
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
105 /// Note, this should *NOT* be used directly by any class other than User.
106 /// User uses this value to find the Use list.
107 static const unsigned NumUserOperandsBits = 29;
108 unsigned NumUserOperands : 29;
112 bool HasHungOffUses : 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.
203 void print(raw_ostream &O) const;
205 /// \brief Print the name of this Value out to the specified raw_ostream.
207 /// This is useful when you just want to print 'int %reg126', not the
208 /// instruction that generated it. If you specify a Module for context, then
209 /// even constanst get pretty-printed; for example, the type of a null
210 /// pointer is printed symbolically.
212 void printAsOperand(raw_ostream &O, bool PrintType = true,
213 const Module *M = nullptr) const;
214 void printAsOperand(raw_ostream &O, bool PrintType,
215 ModuleSlotTracker &MST) const;
218 /// \brief All values are typed, get the type of this value.
219 Type *getType() const { return VTy; }
221 /// \brief All values hold a context through their type.
222 LLVMContext &getContext() const;
224 // \brief All values can potentially be named.
225 bool hasName() const { return HasName; }
226 ValueName *getValueName() const;
227 void setValueName(ValueName *VN);
230 void destroyValueName();
231 void setNameImpl(const Twine &Name);
234 /// \brief Return a constant reference to the value's name.
236 /// This is cheap and guaranteed to return the same reference as long as the
237 /// value is not modified.
238 StringRef getName() const;
240 /// \brief Change the name of the value.
242 /// Choose a new unique name if the provided name is taken.
244 /// \param Name The new name; or "" if the value's name should be removed.
245 void setName(const Twine &Name);
248 /// \brief Transfer the name from V to this value.
250 /// After taking V's name, sets V's name to empty.
252 /// \note It is an error to call V->takeName(V).
253 void takeName(Value *V);
255 /// \brief Change all uses of this to point to a new Value.
257 /// Go through the uses list for this definition and make each use point to
258 /// "V" instead of "this". After this completes, 'this's use list is
259 /// guaranteed to be empty.
260 void replaceAllUsesWith(Value *V);
262 /// replaceUsesOutsideBlock - Go through the uses list for this definition and
263 /// make each use point to "V" instead of "this" when the use is outside the
264 /// block. 'This's use list is expected to have at least one element.
265 /// Unlike replaceAllUsesWith this function does not support basic block
266 /// values or constant users.
267 void replaceUsesOutsideBlock(Value *V, BasicBlock *BB);
269 //----------------------------------------------------------------------
270 // Methods for handling the chain of uses of this Value.
272 bool use_empty() const { return UseList == nullptr; }
274 typedef use_iterator_impl<Use> use_iterator;
275 typedef use_iterator_impl<const Use> const_use_iterator;
276 use_iterator use_begin() { return use_iterator(UseList); }
277 const_use_iterator use_begin() const { return const_use_iterator(UseList); }
278 use_iterator use_end() { return use_iterator(); }
279 const_use_iterator use_end() const { return const_use_iterator(); }
280 iterator_range<use_iterator> uses() {
281 return iterator_range<use_iterator>(use_begin(), use_end());
283 iterator_range<const_use_iterator> uses() const {
284 return iterator_range<const_use_iterator>(use_begin(), use_end());
287 bool user_empty() const { return UseList == nullptr; }
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 #define HANDLE_VALUE(Name) Name##Val,
342 #include "llvm/IR/Value.def"
345 #define HANDLE_CONSTANT_MARKER(Marker, Constant) Marker = Constant##Val,
346 #include "llvm/IR/Value.def"
349 /// \brief Return an ID for the concrete type of this object.
351 /// This is used to implement the classof checks. This should not be used
352 /// for any other purpose, as the values may change as LLVM evolves. Also,
353 /// note that for instructions, the Instruction's opcode is added to
354 /// InstructionVal. So this means three things:
355 /// # there is no value with code InstructionVal (no opcode==0).
356 /// # there are more possible values for the value type than in ValueTy enum.
357 /// # the InstructionVal enumerator must be the highest valued enumerator in
358 /// the ValueTy enum.
359 unsigned getValueID() const {
363 /// \brief Return the raw optional flags value contained in this value.
365 /// This should only be used when testing two Values for equivalence.
366 unsigned getRawSubclassOptionalData() const {
367 return SubclassOptionalData;
370 /// \brief Clear the optional flags contained in this value.
371 void clearSubclassOptionalData() {
372 SubclassOptionalData = 0;
375 /// \brief Check the optional flags for equality.
376 bool hasSameSubclassOptionalData(const Value *V) const {
377 return SubclassOptionalData == V->SubclassOptionalData;
380 /// \brief Clear any optional flags not set in the given Value.
381 void intersectOptionalDataWith(const Value *V) {
382 SubclassOptionalData &= V->SubclassOptionalData;
385 /// \brief Return true if there is a value handle associated with this value.
386 bool hasValueHandle() const { return HasValueHandle; }
388 /// \brief Return true if there is metadata referencing this value.
389 bool isUsedByMetadata() const { return IsUsedByMD; }
391 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
393 /// Returns the original uncasted value. If this is called on a non-pointer
394 /// value, it returns 'this'.
395 Value *stripPointerCasts();
396 const Value *stripPointerCasts() const {
397 return const_cast<Value*>(this)->stripPointerCasts();
400 /// \brief Strip off pointer casts and all-zero GEPs.
402 /// Returns the original uncasted value. If this is called on a non-pointer
403 /// value, it returns 'this'.
404 Value *stripPointerCastsNoFollowAliases();
405 const Value *stripPointerCastsNoFollowAliases() const {
406 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
409 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
411 /// Returns the original pointer value. If this is called on a non-pointer
412 /// value, it returns 'this'.
413 Value *stripInBoundsConstantOffsets();
414 const Value *stripInBoundsConstantOffsets() const {
415 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
418 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
420 /// Stores the resulting constant offset stripped into the APInt provided.
421 /// The provided APInt will be extended or truncated as needed to be the
422 /// correct bitwidth for an offset of this pointer type.
424 /// If this is called on a non-pointer value, it returns 'this'.
425 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
427 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
428 APInt &Offset) const {
429 return const_cast<Value *>(this)
430 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
433 /// \brief Strip off pointer casts and inbounds GEPs.
435 /// Returns the original pointer value. If this is called on a non-pointer
436 /// value, it returns 'this'.
437 Value *stripInBoundsOffsets();
438 const Value *stripInBoundsOffsets() const {
439 return const_cast<Value*>(this)->stripInBoundsOffsets();
442 /// \brief Translate PHI node to its predecessor from the given basic block.
444 /// If this value is a PHI node with CurBB as its parent, return the value in
445 /// the PHI node corresponding to PredBB. If not, return ourself. This is
446 /// useful if you want to know the value something has in a predecessor
448 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
450 const Value *DoPHITranslation(const BasicBlock *CurBB,
451 const BasicBlock *PredBB) const{
452 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
455 /// \brief The maximum alignment for instructions.
457 /// This is the greatest alignment value supported by load, store, and alloca
458 /// instructions, and global values.
459 static const unsigned MaxAlignmentExponent = 29;
460 static const unsigned MaximumAlignment = 1u << MaxAlignmentExponent;
462 /// \brief Mutate the type of this Value to be of the specified type.
464 /// Note that this is an extremely dangerous operation which can create
465 /// completely invalid IR very easily. It is strongly recommended that you
466 /// recreate IR objects with the right types instead of mutating them in
468 void mutateType(Type *Ty) {
472 /// \brief Sort the use-list.
474 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
475 /// expected to compare two \a Use references.
476 template <class Compare> void sortUseList(Compare Cmp);
478 /// \brief Reverse the use-list.
479 void reverseUseList();
482 /// \brief Merge two lists together.
484 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
485 /// "equal" items from L before items from R.
487 /// \return the first element in the list.
489 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
490 template <class Compare>
491 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
493 mergeUseListsImpl(L, R, &Merged, Cmp);
497 /// \brief Tail-recursive helper for \a mergeUseLists().
499 /// \param[out] Next the first element in the list.
500 template <class Compare>
501 static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
504 unsigned short getSubclassDataFromValue() const { return SubclassData; }
505 void setValueSubclassData(unsigned short D) { SubclassData = D; }
508 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
513 void Use::set(Value *V) {
514 if (Val) removeFromList();
516 if (V) V->addUse(*this);
519 template <class Compare> void Value::sortUseList(Compare Cmp) {
520 if (!UseList || !UseList->Next)
521 // No need to sort 0 or 1 uses.
524 // Note: this function completely ignores Prev pointers until the end when
525 // they're fixed en masse.
527 // Create a binomial vector of sorted lists, visiting uses one at a time and
528 // merging lists as necessary.
529 const unsigned MaxSlots = 32;
530 Use *Slots[MaxSlots];
532 // Collect the first use, turning it into a single-item list.
533 Use *Next = UseList->Next;
534 UseList->Next = nullptr;
535 unsigned NumSlots = 1;
538 // Collect all but the last use.
541 Next = Current->Next;
543 // Turn Current into a single-item list.
544 Current->Next = nullptr;
546 // Save Current in the first available slot, merging on collisions.
548 for (I = 0; I < NumSlots; ++I) {
552 // Merge two lists, doubling the size of Current and emptying slot I.
554 // Since the uses in Slots[I] originally preceded those in Current, send
555 // Slots[I] in as the left parameter to maintain a stable sort.
556 Current = mergeUseLists(Slots[I], Current, Cmp);
559 // Check if this is a new slot.
562 assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
565 // Found an open slot.
569 // Merge all the lists together.
570 assert(Next && "Expected one more Use");
571 assert(!Next->Next && "Expected only one Use");
573 for (unsigned I = 0; I < NumSlots; ++I)
575 // Since the uses in Slots[I] originally preceded those in UseList, send
576 // Slots[I] in as the left parameter to maintain a stable sort.
577 UseList = mergeUseLists(Slots[I], UseList, Cmp);
579 // Fix the Prev pointers.
580 for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
586 template <class Compare>
587 void Value::mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp) {
598 mergeUseListsImpl(L, R->Next, &R->Next, Cmp);
602 mergeUseListsImpl(L->Next, R, &L->Next, Cmp);
605 // isa - Provide some specializations of isa so that we don't have to include
606 // the subtype header files to test to see if the value is a subclass...
608 template <> struct isa_impl<Constant, Value> {
609 static inline bool doit(const Value &Val) {
610 return Val.getValueID() >= Value::ConstantFirstVal &&
611 Val.getValueID() <= Value::ConstantLastVal;
615 template <> struct isa_impl<Argument, Value> {
616 static inline bool doit (const Value &Val) {
617 return Val.getValueID() == Value::ArgumentVal;
621 template <> struct isa_impl<InlineAsm, Value> {
622 static inline bool doit(const Value &Val) {
623 return Val.getValueID() == Value::InlineAsmVal;
627 template <> struct isa_impl<Instruction, Value> {
628 static inline bool doit(const Value &Val) {
629 return Val.getValueID() >= Value::InstructionVal;
633 template <> struct isa_impl<BasicBlock, Value> {
634 static inline bool doit(const Value &Val) {
635 return Val.getValueID() == Value::BasicBlockVal;
639 template <> struct isa_impl<Function, Value> {
640 static inline bool doit(const Value &Val) {
641 return Val.getValueID() == Value::FunctionVal;
645 template <> struct isa_impl<GlobalVariable, Value> {
646 static inline bool doit(const Value &Val) {
647 return Val.getValueID() == Value::GlobalVariableVal;
651 template <> struct isa_impl<GlobalAlias, Value> {
652 static inline bool doit(const Value &Val) {
653 return Val.getValueID() == Value::GlobalAliasVal;
657 template <> struct isa_impl<GlobalValue, Value> {
658 static inline bool doit(const Value &Val) {
659 return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
663 template <> struct isa_impl<GlobalObject, Value> {
664 static inline bool doit(const Value &Val) {
665 return isa<GlobalVariable>(Val) || isa<Function>(Val);
669 // Value* is only 4-byte aligned.
671 class PointerLikeTypeTraits<Value*> {
674 static inline void *getAsVoidPointer(PT P) { return P; }
675 static inline PT getFromVoidPointer(void *P) {
676 return static_cast<PT>(P);
678 enum { NumLowBitsAvailable = 2 };
681 // Create wrappers for C Binding types (see CBindingWrapping.h).
682 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
684 /* Specialized opaque value conversions.
686 inline Value **unwrap(LLVMValueRef *Vals) {
687 return reinterpret_cast<Value**>(Vals);
691 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
693 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
697 return reinterpret_cast<T**>(Vals);
700 inline LLVMValueRef *wrap(const Value **Vals) {
701 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
704 } // End llvm namespace