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-c/Types.h"
32 class ConstantAggregate;
37 class GlobalIndirectSymbol;
45 class ModuleSlotTracker;
51 template<typename ValueTy> class StringMapEntry;
52 typedef StringMapEntry<Value*> ValueName;
54 //===----------------------------------------------------------------------===//
56 //===----------------------------------------------------------------------===//
58 /// \brief LLVM Value Representation
60 /// This is a very important LLVM class. It is the base class of all values
61 /// computed by a program that may be used as operands to other values. Value is
62 /// the super class of other important classes such as Instruction and Function.
63 /// All Values have a Type. Type is not a subclass of Value. Some values can
64 /// have a name and they belong to some Module. Setting the name on the Value
65 /// automatically updates the module's symbol table.
67 /// Every value has a "use list" that keeps track of which other Values are
68 /// using this Value. A Value can also have an arbitrary number of ValueHandle
69 /// objects that watch it and listen to RAUW and Destroy events. See
70 /// llvm/IR/ValueHandle.h for details.
75 friend class ValueAsMetadata; // Allow access to IsUsedByMD.
76 friend class ValueHandleBase;
78 const unsigned char SubclassID; // Subclass identifier (for isa/dyn_cast)
79 unsigned char HasValueHandle : 1; // Has a ValueHandle pointing to this?
82 /// \brief Hold subclass data that can be dropped.
84 /// This member is similar to SubclassData, however it is for holding
85 /// information which may be used to aid optimization, but which may be
86 /// cleared to zero without affecting conservative interpretation.
87 unsigned char SubclassOptionalData : 7;
90 /// \brief Hold arbitrary subclass data.
92 /// This member is defined by this class, but is not used for anything.
93 /// Subclasses can use it to hold whatever state they find useful. This
94 /// field is initialized to zero by the ctor.
95 unsigned short SubclassData;
98 /// \brief The number of operands in the subclass.
100 /// This member is defined by this class, but not used for anything.
101 /// Subclasses can use it to store their number of operands, if they have
104 /// This is stored here to save space in User on 64-bit hosts. Since most
105 /// instances of Value have operands, 32-bit hosts aren't significantly
108 /// Note, this should *NOT* be used directly by any class other than User.
109 /// User uses this value to find the Use list.
110 enum : unsigned { NumUserOperandsBits = 28 };
111 unsigned NumUserOperands : NumUserOperandsBits;
113 // Use the same type as the bitfield above so that MSVC will pack them.
114 unsigned IsUsedByMD : 1;
115 unsigned HasName : 1;
116 unsigned HasHungOffUses : 1;
117 unsigned HasDescriptor : 1;
120 template <typename UseT> // UseT == 'Use' or 'const Use'
121 class use_iterator_impl
122 : public std::iterator<std::forward_iterator_tag, UseT *> {
124 explicit use_iterator_impl(UseT *u) : U(u) {}
128 use_iterator_impl() : U() {}
130 bool operator==(const use_iterator_impl &x) const { return U == x.U; }
131 bool operator!=(const use_iterator_impl &x) const { return !operator==(x); }
133 use_iterator_impl &operator++() { // Preincrement
134 assert(U && "Cannot increment end iterator!");
139 use_iterator_impl operator++(int) { // Postincrement
145 UseT &operator*() const {
146 assert(U && "Cannot dereference end iterator!");
150 UseT *operator->() const { return &operator*(); }
152 operator use_iterator_impl<const UseT>() const {
153 return use_iterator_impl<const UseT>(U);
157 template <typename UserTy> // UserTy == 'User' or 'const User'
158 class user_iterator_impl
159 : public std::iterator<std::forward_iterator_tag, UserTy *> {
160 use_iterator_impl<Use> UI;
161 explicit user_iterator_impl(Use *U) : UI(U) {}
165 user_iterator_impl() = default;
167 bool operator==(const user_iterator_impl &x) const { return UI == x.UI; }
168 bool operator!=(const user_iterator_impl &x) const { return !operator==(x); }
170 /// \brief Returns true if this iterator is equal to user_end() on the value.
171 bool atEnd() const { return *this == user_iterator_impl(); }
173 user_iterator_impl &operator++() { // Preincrement
178 user_iterator_impl operator++(int) { // Postincrement
184 // Retrieve a pointer to the current User.
185 UserTy *operator*() const {
186 return UI->getUser();
189 UserTy *operator->() const { return operator*(); }
191 operator user_iterator_impl<const UserTy>() const {
192 return user_iterator_impl<const UserTy>(*UI);
195 Use &getUse() const { return *UI; }
199 Value(Type *Ty, unsigned scid);
202 Value(const Value &) = delete;
203 void operator=(const Value &) = delete;
206 /// \brief Support for debugging, callable in GDB: V->dump()
209 /// \brief Implement operator<< on Value.
211 void print(raw_ostream &O, bool IsForDebug = false) const;
212 void print(raw_ostream &O, ModuleSlotTracker &MST,
213 bool IsForDebug = false) const;
216 /// \brief Print the name of this Value out to the specified raw_ostream.
218 /// This is useful when you just want to print 'int %reg126', not the
219 /// instruction that generated it. If you specify a Module for context, then
220 /// even constanst get pretty-printed; for example, the type of a null
221 /// pointer is printed symbolically.
223 void printAsOperand(raw_ostream &O, bool PrintType = true,
224 const Module *M = nullptr) const;
225 void printAsOperand(raw_ostream &O, bool PrintType,
226 ModuleSlotTracker &MST) const;
229 /// \brief All values are typed, get the type of this value.
230 Type *getType() const { return VTy; }
232 /// \brief All values hold a context through their type.
233 LLVMContext &getContext() const;
235 // \brief All values can potentially be named.
236 bool hasName() const { return HasName; }
237 ValueName *getValueName() const;
238 void setValueName(ValueName *VN);
241 void destroyValueName();
242 void doRAUW(Value *New, bool NoMetadata);
243 void setNameImpl(const Twine &Name);
246 /// \brief Return a constant reference to the value's name.
248 /// This guaranteed to return the same reference as long as the value is not
249 /// modified. If the value has a name, this does a hashtable lookup, so it's
251 StringRef getName() const;
253 /// \brief Change the name of the value.
255 /// Choose a new unique name if the provided name is taken.
257 /// \param Name The new name; or "" if the value's name should be removed.
258 void setName(const Twine &Name);
260 /// \brief Transfer the name from V to this value.
262 /// After taking V's name, sets V's name to empty.
264 /// \note It is an error to call V->takeName(V).
265 void takeName(Value *V);
267 /// \brief Change all uses of this to point to a new Value.
269 /// Go through the uses list for this definition and make each use point to
270 /// "V" instead of "this". After this completes, 'this's use list is
271 /// guaranteed to be empty.
272 void replaceAllUsesWith(Value *V);
274 /// \brief Change non-metadata uses of this to point to a new Value.
276 /// Go through the uses list for this definition and make each use point to
277 /// "V" instead of "this". This function skips metadata entries in the list.
278 void replaceNonMetadataUsesWith(Value *V);
280 /// replaceUsesOutsideBlock - Go through the uses list for this definition and
281 /// make each use point to "V" instead of "this" when the use is outside the
282 /// block. 'This's use list is expected to have at least one element.
283 /// Unlike replaceAllUsesWith this function does not support basic block
284 /// values or constant users.
285 void replaceUsesOutsideBlock(Value *V, BasicBlock *BB);
287 //----------------------------------------------------------------------
288 // Methods for handling the chain of uses of this Value.
290 // Materializing a function can introduce new uses, so these methods come in
292 // The methods that start with materialized_ check the uses that are
293 // currently known given which functions are materialized. Be very careful
294 // when using them since you might not get all uses.
295 // The methods that don't start with materialized_ assert that modules is
296 // fully materialized.
297 void assertModuleIsMaterialized() const;
299 bool use_empty() const {
300 assertModuleIsMaterialized();
301 return UseList == nullptr;
304 typedef use_iterator_impl<Use> use_iterator;
305 typedef use_iterator_impl<const Use> const_use_iterator;
306 use_iterator materialized_use_begin() { return use_iterator(UseList); }
307 const_use_iterator materialized_use_begin() const {
308 return const_use_iterator(UseList);
310 use_iterator use_begin() {
311 assertModuleIsMaterialized();
312 return materialized_use_begin();
314 const_use_iterator use_begin() const {
315 assertModuleIsMaterialized();
316 return materialized_use_begin();
318 use_iterator use_end() { return use_iterator(); }
319 const_use_iterator use_end() const { return const_use_iterator(); }
320 iterator_range<use_iterator> materialized_uses() {
321 return make_range(materialized_use_begin(), use_end());
323 iterator_range<const_use_iterator> materialized_uses() const {
324 return make_range(materialized_use_begin(), use_end());
326 iterator_range<use_iterator> uses() {
327 assertModuleIsMaterialized();
328 return materialized_uses();
330 iterator_range<const_use_iterator> uses() const {
331 assertModuleIsMaterialized();
332 return materialized_uses();
335 bool user_empty() const {
336 assertModuleIsMaterialized();
337 return UseList == nullptr;
340 typedef user_iterator_impl<User> user_iterator;
341 typedef user_iterator_impl<const User> const_user_iterator;
342 user_iterator materialized_user_begin() { return user_iterator(UseList); }
343 const_user_iterator materialized_user_begin() const {
344 return const_user_iterator(UseList);
346 user_iterator user_begin() {
347 assertModuleIsMaterialized();
348 return materialized_user_begin();
350 const_user_iterator user_begin() const {
351 assertModuleIsMaterialized();
352 return materialized_user_begin();
354 user_iterator user_end() { return user_iterator(); }
355 const_user_iterator user_end() const { return const_user_iterator(); }
357 assertModuleIsMaterialized();
358 return *materialized_user_begin();
360 const User *user_back() const {
361 assertModuleIsMaterialized();
362 return *materialized_user_begin();
364 iterator_range<user_iterator> materialized_users() {
365 return make_range(materialized_user_begin(), user_end());
367 iterator_range<const_user_iterator> materialized_users() const {
368 return make_range(materialized_user_begin(), user_end());
370 iterator_range<user_iterator> users() {
371 assertModuleIsMaterialized();
372 return materialized_users();
374 iterator_range<const_user_iterator> users() const {
375 assertModuleIsMaterialized();
376 return materialized_users();
379 /// \brief Return true if there is exactly one user of this value.
381 /// This is specialized because it is a common request and does not require
382 /// traversing the whole use list.
383 bool hasOneUse() const {
384 const_use_iterator I = use_begin(), E = use_end();
385 if (I == E) return false;
389 /// \brief Return true if this Value has exactly N users.
390 bool hasNUses(unsigned N) const;
392 /// \brief Return true if this value has N users or more.
394 /// This is logically equivalent to getNumUses() >= N.
395 bool hasNUsesOrMore(unsigned N) const;
397 /// \brief Check if this value is used in the specified basic block.
398 bool isUsedInBasicBlock(const BasicBlock *BB) const;
400 /// \brief This method computes the number of uses of this Value.
402 /// This is a linear time operation. Use hasOneUse, hasNUses, or
403 /// hasNUsesOrMore to check for specific values.
404 unsigned getNumUses() const;
406 /// \brief This method should only be used by the Use class.
407 void addUse(Use &U) { U.addToList(&UseList); }
409 /// \brief Concrete subclass of this.
411 /// An enumeration for keeping track of the concrete subclass of Value that
412 /// is actually instantiated. Values of this enumeration are kept in the
413 /// Value classes SubclassID field. They are used for concrete type
416 #define HANDLE_VALUE(Name) Name##Val,
417 #include "llvm/IR/Value.def"
420 #define HANDLE_CONSTANT_MARKER(Marker, Constant) Marker = Constant##Val,
421 #include "llvm/IR/Value.def"
424 /// \brief Return an ID for the concrete type of this object.
426 /// This is used to implement the classof checks. This should not be used
427 /// for any other purpose, as the values may change as LLVM evolves. Also,
428 /// note that for instructions, the Instruction's opcode is added to
429 /// InstructionVal. So this means three things:
430 /// # there is no value with code InstructionVal (no opcode==0).
431 /// # there are more possible values for the value type than in ValueTy enum.
432 /// # the InstructionVal enumerator must be the highest valued enumerator in
433 /// the ValueTy enum.
434 unsigned getValueID() const {
438 /// \brief Return the raw optional flags value contained in this value.
440 /// This should only be used when testing two Values for equivalence.
441 unsigned getRawSubclassOptionalData() const {
442 return SubclassOptionalData;
445 /// \brief Clear the optional flags contained in this value.
446 void clearSubclassOptionalData() {
447 SubclassOptionalData = 0;
450 /// \brief Check the optional flags for equality.
451 bool hasSameSubclassOptionalData(const Value *V) const {
452 return SubclassOptionalData == V->SubclassOptionalData;
455 /// \brief Return true if there is a value handle associated with this value.
456 bool hasValueHandle() const { return HasValueHandle; }
458 /// \brief Return true if there is metadata referencing this value.
459 bool isUsedByMetadata() const { return IsUsedByMD; }
461 /// \brief Return true if this value is a swifterror value.
463 /// swifterror values can be either a function argument or an alloca with a
464 /// swifterror attribute.
465 bool isSwiftError() const;
467 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
469 /// Returns the original uncasted value. If this is called on a non-pointer
470 /// value, it returns 'this'.
471 Value *stripPointerCasts();
472 const Value *stripPointerCasts() const {
473 return const_cast<Value*>(this)->stripPointerCasts();
476 /// \brief Strip off pointer casts and all-zero GEPs.
478 /// Returns the original uncasted value. If this is called on a non-pointer
479 /// value, it returns 'this'.
480 Value *stripPointerCastsNoFollowAliases();
481 const Value *stripPointerCastsNoFollowAliases() const {
482 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
485 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
487 /// Returns the original pointer value. If this is called on a non-pointer
488 /// value, it returns 'this'.
489 Value *stripInBoundsConstantOffsets();
490 const Value *stripInBoundsConstantOffsets() const {
491 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
494 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
496 /// Stores the resulting constant offset stripped into the APInt provided.
497 /// The provided APInt will be extended or truncated as needed to be the
498 /// correct bitwidth for an offset of this pointer type.
500 /// If this is called on a non-pointer value, it returns 'this'.
501 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
503 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
504 APInt &Offset) const {
505 return const_cast<Value *>(this)
506 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
509 /// \brief Strip off pointer casts and inbounds GEPs.
511 /// Returns the original pointer value. If this is called on a non-pointer
512 /// value, it returns 'this'.
513 Value *stripInBoundsOffsets();
514 const Value *stripInBoundsOffsets() const {
515 return const_cast<Value*>(this)->stripInBoundsOffsets();
518 /// \brief Returns the number of bytes known to be dereferenceable for the
521 /// If CanBeNull is set by this function the pointer can either be null or be
522 /// dereferenceable up to the returned number of bytes.
523 unsigned getPointerDereferenceableBytes(const DataLayout &DL,
524 bool &CanBeNull) const;
526 /// \brief Returns an alignment of the pointer value.
528 /// Returns an alignment which is either specified explicitly, e.g. via
529 /// align attribute of a function argument, or guaranteed by DataLayout.
530 unsigned getPointerAlignment(const DataLayout &DL) const;
532 /// \brief Translate PHI node to its predecessor from the given basic block.
534 /// If this value is a PHI node with CurBB as its parent, return the value in
535 /// the PHI node corresponding to PredBB. If not, return ourself. This is
536 /// useful if you want to know the value something has in a predecessor
538 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
540 const Value *DoPHITranslation(const BasicBlock *CurBB,
541 const BasicBlock *PredBB) const{
542 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
545 /// \brief The maximum alignment for instructions.
547 /// This is the greatest alignment value supported by load, store, and alloca
548 /// instructions, and global values.
549 static const unsigned MaxAlignmentExponent = 29;
550 static const unsigned MaximumAlignment = 1u << MaxAlignmentExponent;
552 /// \brief Mutate the type of this Value to be of the specified type.
554 /// Note that this is an extremely dangerous operation which can create
555 /// completely invalid IR very easily. It is strongly recommended that you
556 /// recreate IR objects with the right types instead of mutating them in
558 void mutateType(Type *Ty) {
562 /// \brief Sort the use-list.
564 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
565 /// expected to compare two \a Use references.
566 template <class Compare> void sortUseList(Compare Cmp);
568 /// \brief Reverse the use-list.
569 void reverseUseList();
572 /// \brief Merge two lists together.
574 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
575 /// "equal" items from L before items from R.
577 /// \return the first element in the list.
579 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
580 template <class Compare>
581 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
583 Use **Next = &Merged;
608 /// \brief Tail-recursive helper for \a mergeUseLists().
610 /// \param[out] Next the first element in the list.
611 template <class Compare>
612 static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
615 unsigned short getSubclassDataFromValue() const { return SubclassData; }
616 void setValueSubclassData(unsigned short D) { SubclassData = D; }
619 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
624 void Use::set(Value *V) {
625 if (Val) removeFromList();
627 if (V) V->addUse(*this);
630 Value *Use::operator=(Value *RHS) {
635 const Use &Use::operator=(const Use &RHS) {
640 template <class Compare> void Value::sortUseList(Compare Cmp) {
641 if (!UseList || !UseList->Next)
642 // No need to sort 0 or 1 uses.
645 // Note: this function completely ignores Prev pointers until the end when
646 // they're fixed en masse.
648 // Create a binomial vector of sorted lists, visiting uses one at a time and
649 // merging lists as necessary.
650 const unsigned MaxSlots = 32;
651 Use *Slots[MaxSlots];
653 // Collect the first use, turning it into a single-item list.
654 Use *Next = UseList->Next;
655 UseList->Next = nullptr;
656 unsigned NumSlots = 1;
659 // Collect all but the last use.
662 Next = Current->Next;
664 // Turn Current into a single-item list.
665 Current->Next = nullptr;
667 // Save Current in the first available slot, merging on collisions.
669 for (I = 0; I < NumSlots; ++I) {
673 // Merge two lists, doubling the size of Current and emptying slot I.
675 // Since the uses in Slots[I] originally preceded those in Current, send
676 // Slots[I] in as the left parameter to maintain a stable sort.
677 Current = mergeUseLists(Slots[I], Current, Cmp);
680 // Check if this is a new slot.
683 assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
686 // Found an open slot.
690 // Merge all the lists together.
691 assert(Next && "Expected one more Use");
692 assert(!Next->Next && "Expected only one Use");
694 for (unsigned I = 0; I < NumSlots; ++I)
696 // Since the uses in Slots[I] originally preceded those in UseList, send
697 // Slots[I] in as the left parameter to maintain a stable sort.
698 UseList = mergeUseLists(Slots[I], UseList, Cmp);
700 // Fix the Prev pointers.
701 for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
707 // isa - Provide some specializations of isa so that we don't have to include
708 // the subtype header files to test to see if the value is a subclass...
710 template <> struct isa_impl<Constant, Value> {
711 static inline bool doit(const Value &Val) {
712 return Val.getValueID() >= Value::ConstantFirstVal &&
713 Val.getValueID() <= Value::ConstantLastVal;
717 template <> struct isa_impl<ConstantData, Value> {
718 static inline bool doit(const Value &Val) {
719 return Val.getValueID() >= Value::ConstantDataFirstVal &&
720 Val.getValueID() <= Value::ConstantDataLastVal;
724 template <> struct isa_impl<ConstantAggregate, Value> {
725 static inline bool doit(const Value &Val) {
726 return Val.getValueID() >= Value::ConstantAggregateFirstVal &&
727 Val.getValueID() <= Value::ConstantAggregateLastVal;
731 template <> struct isa_impl<Argument, Value> {
732 static inline bool doit (const Value &Val) {
733 return Val.getValueID() == Value::ArgumentVal;
737 template <> struct isa_impl<InlineAsm, Value> {
738 static inline bool doit(const Value &Val) {
739 return Val.getValueID() == Value::InlineAsmVal;
743 template <> struct isa_impl<Instruction, Value> {
744 static inline bool doit(const Value &Val) {
745 return Val.getValueID() >= Value::InstructionVal;
749 template <> struct isa_impl<BasicBlock, Value> {
750 static inline bool doit(const Value &Val) {
751 return Val.getValueID() == Value::BasicBlockVal;
755 template <> struct isa_impl<Function, Value> {
756 static inline bool doit(const Value &Val) {
757 return Val.getValueID() == Value::FunctionVal;
761 template <> struct isa_impl<GlobalVariable, Value> {
762 static inline bool doit(const Value &Val) {
763 return Val.getValueID() == Value::GlobalVariableVal;
767 template <> struct isa_impl<GlobalAlias, Value> {
768 static inline bool doit(const Value &Val) {
769 return Val.getValueID() == Value::GlobalAliasVal;
773 template <> struct isa_impl<GlobalIFunc, Value> {
774 static inline bool doit(const Value &Val) {
775 return Val.getValueID() == Value::GlobalIFuncVal;
779 template <> struct isa_impl<GlobalIndirectSymbol, Value> {
780 static inline bool doit(const Value &Val) {
781 return isa<GlobalAlias>(Val) || isa<GlobalIFunc>(Val);
785 template <> struct isa_impl<GlobalValue, Value> {
786 static inline bool doit(const Value &Val) {
787 return isa<GlobalObject>(Val) || isa<GlobalIndirectSymbol>(Val);
791 template <> struct isa_impl<GlobalObject, Value> {
792 static inline bool doit(const Value &Val) {
793 return isa<GlobalVariable>(Val) || isa<Function>(Val);
797 // Create wrappers for C Binding types (see CBindingWrapping.h).
798 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
800 // Specialized opaque value conversions.
801 inline Value **unwrap(LLVMValueRef *Vals) {
802 return reinterpret_cast<Value**>(Vals);
806 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
808 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
809 unwrap<T>(*I); // For side effect of calling assert on invalid usage.
812 return reinterpret_cast<T**>(Vals);
815 inline LLVMValueRef *wrap(const Value **Vals) {
816 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));
819 } // end namespace llvm
821 #endif // LLVM_IR_VALUE_H