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 : 29;
107 bool HasHungOffUses : 1;
110 template <typename UseT> // UseT == 'Use' or 'const Use'
111 class use_iterator_impl
112 : public std::iterator<std::forward_iterator_tag, UseT *> {
114 explicit use_iterator_impl(UseT *u) : U(u) {}
118 use_iterator_impl() : U() {}
120 bool operator==(const use_iterator_impl &x) const { return U == x.U; }
121 bool operator!=(const use_iterator_impl &x) const { return !operator==(x); }
123 use_iterator_impl &operator++() { // Preincrement
124 assert(U && "Cannot increment end iterator!");
128 use_iterator_impl operator++(int) { // Postincrement
134 UseT &operator*() const {
135 assert(U && "Cannot dereference end iterator!");
139 UseT *operator->() const { return &operator*(); }
141 operator use_iterator_impl<const UseT>() const {
142 return use_iterator_impl<const UseT>(U);
146 template <typename UserTy> // UserTy == 'User' or 'const User'
147 class user_iterator_impl
148 : public std::iterator<std::forward_iterator_tag, UserTy *> {
149 use_iterator_impl<Use> UI;
150 explicit user_iterator_impl(Use *U) : UI(U) {}
154 user_iterator_impl() {}
156 bool operator==(const user_iterator_impl &x) const { return UI == x.UI; }
157 bool operator!=(const user_iterator_impl &x) const { return !operator==(x); }
159 /// \brief Returns true if this iterator is equal to user_end() on the value.
160 bool atEnd() const { return *this == user_iterator_impl(); }
162 user_iterator_impl &operator++() { // Preincrement
166 user_iterator_impl operator++(int) { // Postincrement
172 // Retrieve a pointer to the current User.
173 UserTy *operator*() const {
174 return UI->getUser();
177 UserTy *operator->() const { return operator*(); }
179 operator user_iterator_impl<const UserTy>() const {
180 return user_iterator_impl<const UserTy>(*UI);
183 Use &getUse() const { return *UI; }
186 void operator=(const Value &) = delete;
187 Value(const Value &) = delete;
190 Value(Type *Ty, unsigned scid);
194 /// \brief Support for debugging, callable in GDB: V->dump()
197 /// \brief Implement operator<< on Value.
198 void print(raw_ostream &O) const;
200 /// \brief Print the name of this Value out to the specified raw_ostream.
202 /// This is useful when you just want to print 'int %reg126', not the
203 /// instruction that generated it. If you specify a Module for context, then
204 /// even constanst get pretty-printed; for example, the type of a null
205 /// pointer is printed symbolically.
206 void printAsOperand(raw_ostream &O, bool PrintType = true,
207 const Module *M = nullptr) const;
209 /// \brief All values are typed, get the type of this value.
210 Type *getType() const { return VTy; }
212 /// \brief All values hold a context through their type.
213 LLVMContext &getContext() const;
215 // \brief All values can potentially be named.
216 bool hasName() const { return HasName; }
217 ValueName *getValueName() const;
218 void setValueName(ValueName *VN);
221 void destroyValueName();
222 void setNameImpl(const Twine &Name);
225 /// \brief Return a constant reference to the value's name.
227 /// This is cheap and guaranteed to return the same reference as long as the
228 /// value is not modified.
229 StringRef getName() const;
231 /// \brief Change the name of the value.
233 /// Choose a new unique name if the provided name is taken.
235 /// \param Name The new name; or "" if the value's name should be removed.
236 void setName(const Twine &Name);
239 /// \brief Transfer the name from V to this value.
241 /// After taking V's name, sets V's name to empty.
243 /// \note It is an error to call V->takeName(V).
244 void takeName(Value *V);
246 /// \brief Change all uses of this to point to a new Value.
248 /// Go through the uses list for this definition and make each use point to
249 /// "V" instead of "this". After this completes, 'this's use list is
250 /// guaranteed to be empty.
251 void replaceAllUsesWith(Value *V);
253 /// replaceUsesOutsideBlock - Go through the uses list for this definition and
254 /// make each use point to "V" instead of "this" when the use is outside the
255 /// block. 'This's use list is expected to have at least one element.
256 /// Unlike replaceAllUsesWith this function does not support basic block
257 /// values or constant users.
258 void replaceUsesOutsideBlock(Value *V, BasicBlock *BB);
260 //----------------------------------------------------------------------
261 // Methods for handling the chain of uses of this Value.
263 bool use_empty() const { return UseList == nullptr; }
265 typedef use_iterator_impl<Use> use_iterator;
266 typedef use_iterator_impl<const Use> const_use_iterator;
267 use_iterator use_begin() { return use_iterator(UseList); }
268 const_use_iterator use_begin() const { return const_use_iterator(UseList); }
269 use_iterator use_end() { return use_iterator(); }
270 const_use_iterator use_end() const { return const_use_iterator(); }
271 iterator_range<use_iterator> uses() {
272 return iterator_range<use_iterator>(use_begin(), use_end());
274 iterator_range<const_use_iterator> uses() const {
275 return iterator_range<const_use_iterator>(use_begin(), use_end());
278 bool user_empty() const { return UseList == nullptr; }
280 typedef user_iterator_impl<User> user_iterator;
281 typedef user_iterator_impl<const User> const_user_iterator;
282 user_iterator user_begin() { return user_iterator(UseList); }
283 const_user_iterator user_begin() const { return const_user_iterator(UseList); }
284 user_iterator user_end() { return user_iterator(); }
285 const_user_iterator user_end() const { return const_user_iterator(); }
286 User *user_back() { return *user_begin(); }
287 const User *user_back() const { return *user_begin(); }
288 iterator_range<user_iterator> users() {
289 return iterator_range<user_iterator>(user_begin(), user_end());
291 iterator_range<const_user_iterator> users() const {
292 return iterator_range<const_user_iterator>(user_begin(), user_end());
295 /// \brief Return true if there is exactly one user of this value.
297 /// This is specialized because it is a common request and does not require
298 /// traversing the whole use list.
299 bool hasOneUse() const {
300 const_use_iterator I = use_begin(), E = use_end();
301 if (I == E) return false;
305 /// \brief Return true if this Value has exactly N users.
306 bool hasNUses(unsigned N) const;
308 /// \brief Return true if this value has N users or more.
310 /// This is logically equivalent to getNumUses() >= N.
311 bool hasNUsesOrMore(unsigned N) const;
313 /// \brief Check if this value is used in the specified basic block.
314 bool isUsedInBasicBlock(const BasicBlock *BB) const;
316 /// \brief This method computes the number of uses of this Value.
318 /// This is a linear time operation. Use hasOneUse, hasNUses, or
319 /// hasNUsesOrMore to check for specific values.
320 unsigned getNumUses() const;
322 /// \brief This method should only be used by the Use class.
323 void addUse(Use &U) { U.addToList(&UseList); }
325 /// \brief Concrete subclass of this.
327 /// An enumeration for keeping track of the concrete subclass of Value that
328 /// is actually instantiated. Values of this enumeration are kept in the
329 /// Value classes SubclassID field. They are used for concrete type
332 ArgumentVal, // This is an instance of Argument
333 BasicBlockVal, // This is an instance of BasicBlock
334 FunctionVal, // This is an instance of Function
335 GlobalAliasVal, // This is an instance of GlobalAlias
336 GlobalVariableVal, // This is an instance of GlobalVariable
337 UndefValueVal, // This is an instance of UndefValue
338 BlockAddressVal, // This is an instance of BlockAddress
339 ConstantExprVal, // This is an instance of ConstantExpr
340 ConstantAggregateZeroVal, // This is an instance of ConstantAggregateZero
341 ConstantDataArrayVal, // This is an instance of ConstantDataArray
342 ConstantDataVectorVal, // This is an instance of ConstantDataVector
343 ConstantIntVal, // This is an instance of ConstantInt
344 ConstantFPVal, // This is an instance of ConstantFP
345 ConstantArrayVal, // This is an instance of ConstantArray
346 ConstantStructVal, // This is an instance of ConstantStruct
347 ConstantVectorVal, // This is an instance of ConstantVector
348 ConstantPointerNullVal, // This is an instance of ConstantPointerNull
349 MetadataAsValueVal, // This is an instance of MetadataAsValue
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 Return true if there is metadata referencing this value.
400 bool isUsedByMetadata() const { return IsUsedByMD; }
402 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
404 /// Returns the original uncasted value. If this is called on a non-pointer
405 /// value, it returns 'this'.
406 Value *stripPointerCasts();
407 const Value *stripPointerCasts() const {
408 return const_cast<Value*>(this)->stripPointerCasts();
411 /// \brief Strip off pointer casts and all-zero GEPs.
413 /// Returns the original uncasted value. If this is called on a non-pointer
414 /// value, it returns 'this'.
415 Value *stripPointerCastsNoFollowAliases();
416 const Value *stripPointerCastsNoFollowAliases() const {
417 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
420 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
422 /// Returns the original pointer value. If this is called on a non-pointer
423 /// value, it returns 'this'.
424 Value *stripInBoundsConstantOffsets();
425 const Value *stripInBoundsConstantOffsets() const {
426 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
429 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
431 /// Stores the resulting constant offset stripped into the APInt provided.
432 /// The provided APInt will be extended or truncated as needed to be the
433 /// correct bitwidth for an offset of this pointer type.
435 /// If this is called on a non-pointer value, it returns 'this'.
436 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
438 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
439 APInt &Offset) const {
440 return const_cast<Value *>(this)
441 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
444 /// \brief Strip off pointer casts and inbounds GEPs.
446 /// Returns the original pointer value. If this is called on a non-pointer
447 /// value, it returns 'this'.
448 Value *stripInBoundsOffsets();
449 const Value *stripInBoundsOffsets() const {
450 return const_cast<Value*>(this)->stripInBoundsOffsets();
453 /// \brief Translate PHI node to its predecessor from the given basic block.
455 /// If this value is a PHI node with CurBB as its parent, return the value in
456 /// the PHI node corresponding to PredBB. If not, return ourself. This is
457 /// useful if you want to know the value something has in a predecessor
459 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
461 const Value *DoPHITranslation(const BasicBlock *CurBB,
462 const BasicBlock *PredBB) const{
463 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
466 /// \brief The maximum alignment for instructions.
468 /// This is the greatest alignment value supported by load, store, and alloca
469 /// instructions, and global values.
470 static const unsigned MaxAlignmentExponent = 29;
471 static const unsigned MaximumAlignment = 1u << MaxAlignmentExponent;
473 /// \brief Mutate the type of this Value to be of the specified type.
475 /// Note that this is an extremely dangerous operation which can create
476 /// completely invalid IR very easily. It is strongly recommended that you
477 /// recreate IR objects with the right types instead of mutating them in
479 void mutateType(Type *Ty) {
483 /// \brief Sort the use-list.
485 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
486 /// expected to compare two \a Use references.
487 template <class Compare> void sortUseList(Compare Cmp);
489 /// \brief Reverse the use-list.
490 void reverseUseList();
493 /// \brief Merge two lists together.
495 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
496 /// "equal" items from L before items from R.
498 /// \return the first element in the list.
500 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
501 template <class Compare>
502 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
504 mergeUseListsImpl(L, R, &Merged, Cmp);
508 /// \brief Tail-recursive helper for \a mergeUseLists().
510 /// \param[out] Next the first element in the list.
511 template <class Compare>
512 static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
515 unsigned short getSubclassDataFromValue() const { return SubclassData; }
516 void setValueSubclassData(unsigned short D) { SubclassData = D; }
519 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
524 void Use::set(Value *V) {
525 if (Val) removeFromList();
527 if (V) V->addUse(*this);
530 template <class Compare> void Value::sortUseList(Compare Cmp) {
531 if (!UseList || !UseList->Next)
532 // No need to sort 0 or 1 uses.
535 // Note: this function completely ignores Prev pointers until the end when
536 // they're fixed en masse.
538 // Create a binomial vector of sorted lists, visiting uses one at a time and
539 // merging lists as necessary.
540 const unsigned MaxSlots = 32;
541 Use *Slots[MaxSlots];
543 // Collect the first use, turning it into a single-item list.
544 Use *Next = UseList->Next;
545 UseList->Next = nullptr;
546 unsigned NumSlots = 1;
549 // Collect all but the last use.
552 Next = Current->Next;
554 // Turn Current into a single-item list.
555 Current->Next = nullptr;
557 // Save Current in the first available slot, merging on collisions.
559 for (I = 0; I < NumSlots; ++I) {
563 // Merge two lists, doubling the size of Current and emptying slot I.
565 // Since the uses in Slots[I] originally preceded those in Current, send
566 // Slots[I] in as the left parameter to maintain a stable sort.
567 Current = mergeUseLists(Slots[I], Current, Cmp);
570 // Check if this is a new slot.
573 assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
576 // Found an open slot.
580 // Merge all the lists together.
581 assert(Next && "Expected one more Use");
582 assert(!Next->Next && "Expected only one Use");
584 for (unsigned I = 0; I < NumSlots; ++I)
586 // Since the uses in Slots[I] originally preceded those in UseList, send
587 // Slots[I] in as the left parameter to maintain a stable sort.
588 UseList = mergeUseLists(Slots[I], UseList, Cmp);
590 // Fix the Prev pointers.
591 for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
597 template <class Compare>
598 void Value::mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp) {
609 mergeUseListsImpl(L, R->Next, &R->Next, Cmp);
613 mergeUseListsImpl(L->Next, R, &L->Next, Cmp);
616 // isa - Provide some specializations of isa so that we don't have to include
617 // the subtype header files to test to see if the value is a subclass...
619 template <> struct isa_impl<Constant, Value> {
620 static inline bool doit(const Value &Val) {
621 return Val.getValueID() >= Value::ConstantFirstVal &&
622 Val.getValueID() <= Value::ConstantLastVal;
626 template <> struct isa_impl<Argument, Value> {
627 static inline bool doit (const Value &Val) {
628 return Val.getValueID() == Value::ArgumentVal;
632 template <> struct isa_impl<InlineAsm, Value> {
633 static inline bool doit(const Value &Val) {
634 return Val.getValueID() == Value::InlineAsmVal;
638 template <> struct isa_impl<Instruction, Value> {
639 static inline bool doit(const Value &Val) {
640 return Val.getValueID() >= Value::InstructionVal;
644 template <> struct isa_impl<BasicBlock, Value> {
645 static inline bool doit(const Value &Val) {
646 return Val.getValueID() == Value::BasicBlockVal;
650 template <> struct isa_impl<Function, Value> {
651 static inline bool doit(const Value &Val) {
652 return Val.getValueID() == Value::FunctionVal;
656 template <> struct isa_impl<GlobalVariable, Value> {
657 static inline bool doit(const Value &Val) {
658 return Val.getValueID() == Value::GlobalVariableVal;
662 template <> struct isa_impl<GlobalAlias, Value> {
663 static inline bool doit(const Value &Val) {
664 return Val.getValueID() == Value::GlobalAliasVal;
668 template <> struct isa_impl<GlobalValue, Value> {
669 static inline bool doit(const Value &Val) {
670 return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
674 template <> struct isa_impl<GlobalObject, Value> {
675 static inline bool doit(const Value &Val) {
676 return isa<GlobalVariable>(Val) || isa<Function>(Val);
680 // Value* is only 4-byte aligned.
682 class PointerLikeTypeTraits<Value*> {
685 static inline void *getAsVoidPointer(PT P) { return P; }
686 static inline PT getFromVoidPointer(void *P) {
687 return static_cast<PT>(P);
689 enum { NumLowBitsAvailable = 2 };
692 // Create wrappers for C Binding types (see CBindingWrapping.h).
693 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
695 /* Specialized opaque value conversions.
697 inline Value **unwrap(LLVMValueRef *Vals) {
698 return reinterpret_cast<Value**>(Vals);
702 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
704 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
708 return reinterpret_cast<T**>(Vals);
711 inline LLVMValueRef *wrap(const Value **Vals) {
712 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
715 } // End llvm namespace