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 { return const_user_iterator(UseList); }
297 user_iterator user_end() { return user_iterator(); }
298 const_user_iterator user_end() const { return const_user_iterator(); }
299 User *user_back() { return *user_begin(); }
300 const User *user_back() const { return *user_begin(); }
301 iterator_range<user_iterator> users() {
302 return make_range(user_begin(), user_end());
304 iterator_range<const_user_iterator> users() const {
305 return make_range(user_begin(), user_end());
308 /// \brief Return true if there is exactly one user of this value.
310 /// This is specialized because it is a common request and does not require
311 /// traversing the whole use list.
312 bool hasOneUse() const {
313 const_use_iterator I = use_begin(), E = use_end();
314 if (I == E) return false;
318 /// \brief Return true if this Value has exactly N users.
319 bool hasNUses(unsigned N) const;
321 /// \brief Return true if this value has N users or more.
323 /// This is logically equivalent to getNumUses() >= N.
324 bool hasNUsesOrMore(unsigned N) const;
326 /// \brief Check if this value is used in the specified basic block.
327 bool isUsedInBasicBlock(const BasicBlock *BB) const;
329 /// \brief This method computes the number of uses of this Value.
331 /// This is a linear time operation. Use hasOneUse, hasNUses, or
332 /// hasNUsesOrMore to check for specific values.
333 unsigned getNumUses() const;
335 /// \brief This method should only be used by the Use class.
336 void addUse(Use &U) { U.addToList(&UseList); }
338 /// \brief Concrete subclass of this.
340 /// An enumeration for keeping track of the concrete subclass of Value that
341 /// is actually instantiated. Values of this enumeration are kept in the
342 /// Value classes SubclassID field. They are used for concrete type
345 #define HANDLE_VALUE(Name) Name##Val,
346 #include "llvm/IR/Value.def"
349 #define HANDLE_CONSTANT_MARKER(Marker, Constant) Marker = Constant##Val,
350 #include "llvm/IR/Value.def"
353 /// \brief Return an ID for the concrete type of this object.
355 /// This is used to implement the classof checks. This should not be used
356 /// for any other purpose, as the values may change as LLVM evolves. Also,
357 /// note that for instructions, the Instruction's opcode is added to
358 /// InstructionVal. So this means three things:
359 /// # there is no value with code InstructionVal (no opcode==0).
360 /// # there are more possible values for the value type than in ValueTy enum.
361 /// # the InstructionVal enumerator must be the highest valued enumerator in
362 /// the ValueTy enum.
363 unsigned getValueID() const {
367 /// \brief Return the raw optional flags value contained in this value.
369 /// This should only be used when testing two Values for equivalence.
370 unsigned getRawSubclassOptionalData() const {
371 return SubclassOptionalData;
374 /// \brief Clear the optional flags contained in this value.
375 void clearSubclassOptionalData() {
376 SubclassOptionalData = 0;
379 /// \brief Check the optional flags for equality.
380 bool hasSameSubclassOptionalData(const Value *V) const {
381 return SubclassOptionalData == V->SubclassOptionalData;
384 /// \brief Clear any optional flags not set in the given Value.
385 void intersectOptionalDataWith(const Value *V) {
386 SubclassOptionalData &= V->SubclassOptionalData;
389 /// \brief Return true if there is a value handle associated with this value.
390 bool hasValueHandle() const { return HasValueHandle; }
392 /// \brief Return true if there is metadata referencing this value.
393 bool isUsedByMetadata() const { return IsUsedByMD; }
395 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
397 /// Returns the original uncasted value. If this is called on a non-pointer
398 /// value, it returns 'this'.
399 Value *stripPointerCasts();
400 const Value *stripPointerCasts() const {
401 return const_cast<Value*>(this)->stripPointerCasts();
404 /// \brief Strip off pointer casts and all-zero GEPs.
406 /// Returns the original uncasted value. If this is called on a non-pointer
407 /// value, it returns 'this'.
408 Value *stripPointerCastsNoFollowAliases();
409 const Value *stripPointerCastsNoFollowAliases() const {
410 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
413 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
415 /// Returns the original pointer value. If this is called on a non-pointer
416 /// value, it returns 'this'.
417 Value *stripInBoundsConstantOffsets();
418 const Value *stripInBoundsConstantOffsets() const {
419 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
422 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
424 /// Stores the resulting constant offset stripped into the APInt provided.
425 /// The provided APInt will be extended or truncated as needed to be the
426 /// correct bitwidth for an offset of this pointer type.
428 /// If this is called on a non-pointer value, it returns 'this'.
429 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
431 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
432 APInt &Offset) const {
433 return const_cast<Value *>(this)
434 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
437 /// \brief Strip off pointer casts and inbounds GEPs.
439 /// Returns the original pointer value. If this is called on a non-pointer
440 /// value, it returns 'this'.
441 Value *stripInBoundsOffsets();
442 const Value *stripInBoundsOffsets() const {
443 return const_cast<Value*>(this)->stripInBoundsOffsets();
446 /// \brief Translate PHI node to its predecessor from the given basic block.
448 /// If this value is a PHI node with CurBB as its parent, return the value in
449 /// the PHI node corresponding to PredBB. If not, return ourself. This is
450 /// useful if you want to know the value something has in a predecessor
452 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
454 const Value *DoPHITranslation(const BasicBlock *CurBB,
455 const BasicBlock *PredBB) const{
456 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
459 /// \brief The maximum alignment for instructions.
461 /// This is the greatest alignment value supported by load, store, and alloca
462 /// instructions, and global values.
463 static const unsigned MaxAlignmentExponent = 29;
464 static const unsigned MaximumAlignment = 1u << MaxAlignmentExponent;
466 /// \brief Mutate the type of this Value to be of the specified type.
468 /// Note that this is an extremely dangerous operation which can create
469 /// completely invalid IR very easily. It is strongly recommended that you
470 /// recreate IR objects with the right types instead of mutating them in
472 void mutateType(Type *Ty) {
476 /// \brief Sort the use-list.
478 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
479 /// expected to compare two \a Use references.
480 template <class Compare> void sortUseList(Compare Cmp);
482 /// \brief Reverse the use-list.
483 void reverseUseList();
486 /// \brief Merge two lists together.
488 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
489 /// "equal" items from L before items from R.
491 /// \return the first element in the list.
493 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
494 template <class Compare>
495 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
497 Use **Next = &Merged;
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 // isa - Provide some specializations of isa so that we don't have to include
612 // the subtype header files to test to see if the value is a subclass...
614 template <> struct isa_impl<Constant, Value> {
615 static inline bool doit(const Value &Val) {
616 return Val.getValueID() >= Value::ConstantFirstVal &&
617 Val.getValueID() <= Value::ConstantLastVal;
621 template <> struct isa_impl<Argument, Value> {
622 static inline bool doit (const Value &Val) {
623 return Val.getValueID() == Value::ArgumentVal;
627 template <> struct isa_impl<InlineAsm, Value> {
628 static inline bool doit(const Value &Val) {
629 return Val.getValueID() == Value::InlineAsmVal;
633 template <> struct isa_impl<Instruction, Value> {
634 static inline bool doit(const Value &Val) {
635 return Val.getValueID() >= Value::InstructionVal;
639 template <> struct isa_impl<BasicBlock, Value> {
640 static inline bool doit(const Value &Val) {
641 return Val.getValueID() == Value::BasicBlockVal;
645 template <> struct isa_impl<Function, Value> {
646 static inline bool doit(const Value &Val) {
647 return Val.getValueID() == Value::FunctionVal;
651 template <> struct isa_impl<GlobalVariable, Value> {
652 static inline bool doit(const Value &Val) {
653 return Val.getValueID() == Value::GlobalVariableVal;
657 template <> struct isa_impl<GlobalAlias, Value> {
658 static inline bool doit(const Value &Val) {
659 return Val.getValueID() == Value::GlobalAliasVal;
663 template <> struct isa_impl<GlobalValue, Value> {
664 static inline bool doit(const Value &Val) {
665 return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
669 template <> struct isa_impl<GlobalObject, Value> {
670 static inline bool doit(const Value &Val) {
671 return isa<GlobalVariable>(Val) || isa<Function>(Val);
675 // Value* is only 4-byte aligned.
677 class PointerLikeTypeTraits<Value*> {
680 static inline void *getAsVoidPointer(PT P) { return P; }
681 static inline PT getFromVoidPointer(void *P) {
682 return static_cast<PT>(P);
684 enum { NumLowBitsAvailable = 2 };
687 // Create wrappers for C Binding types (see CBindingWrapping.h).
688 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
690 /* Specialized opaque value conversions.
692 inline Value **unwrap(LLVMValueRef *Vals) {
693 return reinterpret_cast<Value**>(Vals);
697 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
699 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
703 return reinterpret_cast<T**>(Vals);
706 inline LLVMValueRef *wrap(const Value **Vals) {
707 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
710 } // End llvm namespace