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
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 static const unsigned NumUserOperandsBits = 29;
107 unsigned NumUserOperands : 29;
111 bool HasHungOffUses : 1;
114 template <typename UseT> // UseT == 'Use' or 'const Use'
115 class use_iterator_impl
116 : public std::iterator<std::forward_iterator_tag, UseT *> {
118 explicit use_iterator_impl(UseT *u) : U(u) {}
122 use_iterator_impl() : U() {}
124 bool operator==(const use_iterator_impl &x) const { return U == x.U; }
125 bool operator!=(const use_iterator_impl &x) const { return !operator==(x); }
127 use_iterator_impl &operator++() { // Preincrement
128 assert(U && "Cannot increment end iterator!");
132 use_iterator_impl operator++(int) { // Postincrement
138 UseT &operator*() const {
139 assert(U && "Cannot dereference end iterator!");
143 UseT *operator->() const { return &operator*(); }
145 operator use_iterator_impl<const UseT>() const {
146 return use_iterator_impl<const UseT>(U);
150 template <typename UserTy> // UserTy == 'User' or 'const User'
151 class user_iterator_impl
152 : public std::iterator<std::forward_iterator_tag, UserTy *> {
153 use_iterator_impl<Use> UI;
154 explicit user_iterator_impl(Use *U) : UI(U) {}
158 user_iterator_impl() {}
160 bool operator==(const user_iterator_impl &x) const { return UI == x.UI; }
161 bool operator!=(const user_iterator_impl &x) const { return !operator==(x); }
163 /// \brief Returns true if this iterator is equal to user_end() on the value.
164 bool atEnd() const { return *this == user_iterator_impl(); }
166 user_iterator_impl &operator++() { // Preincrement
170 user_iterator_impl operator++(int) { // Postincrement
176 // Retrieve a pointer to the current User.
177 UserTy *operator*() const {
178 return UI->getUser();
181 UserTy *operator->() const { return operator*(); }
183 operator user_iterator_impl<const UserTy>() const {
184 return user_iterator_impl<const UserTy>(*UI);
187 Use &getUse() const { return *UI; }
190 void operator=(const Value &) = delete;
191 Value(const Value &) = delete;
194 Value(Type *Ty, unsigned scid);
198 /// \brief Support for debugging, callable in GDB: V->dump()
201 /// \brief Implement operator<< on Value.
202 void print(raw_ostream &O) const;
204 /// \brief Print the name of this Value out to the specified raw_ostream.
206 /// This is useful when you just want to print 'int %reg126', not the
207 /// instruction that generated it. If you specify a Module for context, then
208 /// even constanst get pretty-printed; for example, the type of a null
209 /// pointer is printed symbolically.
210 void printAsOperand(raw_ostream &O, bool PrintType = true,
211 const Module *M = nullptr) const;
213 /// \brief All values are typed, get the type of this value.
214 Type *getType() const { return VTy; }
216 /// \brief All values hold a context through their type.
217 LLVMContext &getContext() const;
219 // \brief All values can potentially be named.
220 bool hasName() const { return HasName; }
221 ValueName *getValueName() const;
222 void setValueName(ValueName *VN);
225 void destroyValueName();
226 void setNameImpl(const Twine &Name);
229 /// \brief Return a constant reference to the value's name.
231 /// This is cheap and guaranteed to return the same reference as long as the
232 /// value is not modified.
233 StringRef getName() const;
235 /// \brief Change the name of the value.
237 /// Choose a new unique name if the provided name is taken.
239 /// \param Name The new name; or "" if the value's name should be removed.
240 void setName(const Twine &Name);
243 /// \brief Transfer the name from V to this value.
245 /// After taking V's name, sets V's name to empty.
247 /// \note It is an error to call V->takeName(V).
248 void takeName(Value *V);
250 /// \brief Change all uses of this to point to a new Value.
252 /// Go through the uses list for this definition and make each use point to
253 /// "V" instead of "this". After this completes, 'this's use list is
254 /// guaranteed to be empty.
255 void replaceAllUsesWith(Value *V);
257 /// replaceUsesOutsideBlock - Go through the uses list for this definition and
258 /// make each use point to "V" instead of "this" when the use is outside the
259 /// block. 'This's use list is expected to have at least one element.
260 /// Unlike replaceAllUsesWith this function does not support basic block
261 /// values or constant users.
262 void replaceUsesOutsideBlock(Value *V, BasicBlock *BB);
264 //----------------------------------------------------------------------
265 // Methods for handling the chain of uses of this Value.
267 bool use_empty() const { return UseList == nullptr; }
269 typedef use_iterator_impl<Use> use_iterator;
270 typedef use_iterator_impl<const Use> const_use_iterator;
271 use_iterator use_begin() { return use_iterator(UseList); }
272 const_use_iterator use_begin() const { return const_use_iterator(UseList); }
273 use_iterator use_end() { return use_iterator(); }
274 const_use_iterator use_end() const { return const_use_iterator(); }
275 iterator_range<use_iterator> uses() {
276 return iterator_range<use_iterator>(use_begin(), use_end());
278 iterator_range<const_use_iterator> uses() const {
279 return iterator_range<const_use_iterator>(use_begin(), use_end());
282 bool user_empty() const { return UseList == nullptr; }
284 typedef user_iterator_impl<User> user_iterator;
285 typedef user_iterator_impl<const User> const_user_iterator;
286 user_iterator user_begin() { return user_iterator(UseList); }
287 const_user_iterator user_begin() const { return const_user_iterator(UseList); }
288 user_iterator user_end() { return user_iterator(); }
289 const_user_iterator user_end() const { return const_user_iterator(); }
290 User *user_back() { return *user_begin(); }
291 const User *user_back() const { return *user_begin(); }
292 iterator_range<user_iterator> users() {
293 return iterator_range<user_iterator>(user_begin(), user_end());
295 iterator_range<const_user_iterator> users() const {
296 return iterator_range<const_user_iterator>(user_begin(), user_end());
299 /// \brief Return true if there is exactly one user of this value.
301 /// This is specialized because it is a common request and does not require
302 /// traversing the whole use list.
303 bool hasOneUse() const {
304 const_use_iterator I = use_begin(), E = use_end();
305 if (I == E) return false;
309 /// \brief Return true if this Value has exactly N users.
310 bool hasNUses(unsigned N) const;
312 /// \brief Return true if this value has N users or more.
314 /// This is logically equivalent to getNumUses() >= N.
315 bool hasNUsesOrMore(unsigned N) const;
317 /// \brief Check if this value is used in the specified basic block.
318 bool isUsedInBasicBlock(const BasicBlock *BB) const;
320 /// \brief This method computes the number of uses of this Value.
322 /// This is a linear time operation. Use hasOneUse, hasNUses, or
323 /// hasNUsesOrMore to check for specific values.
324 unsigned getNumUses() const;
326 /// \brief This method should only be used by the Use class.
327 void addUse(Use &U) { U.addToList(&UseList); }
329 /// \brief Concrete subclass of this.
331 /// An enumeration for keeping track of the concrete subclass of Value that
332 /// is actually instantiated. Values of this enumeration are kept in the
333 /// Value classes SubclassID field. They are used for concrete type
336 #define HANDLE_VALUE(Name) Name##Val,
337 #include "llvm/IR/Value.def"
340 #define HANDLE_CONSTANT_MARKER(Marker, Constant) Marker = Constant##Val,
341 #include "llvm/IR/Value.def"
344 /// \brief Return an ID for the concrete type of this object.
346 /// This is used to implement the classof checks. This should not be used
347 /// for any other purpose, as the values may change as LLVM evolves. Also,
348 /// note that for instructions, the Instruction's opcode is added to
349 /// InstructionVal. So this means three things:
350 /// # there is no value with code InstructionVal (no opcode==0).
351 /// # there are more possible values for the value type than in ValueTy enum.
352 /// # the InstructionVal enumerator must be the highest valued enumerator in
353 /// the ValueTy enum.
354 unsigned getValueID() const {
358 /// \brief Return the raw optional flags value contained in this value.
360 /// This should only be used when testing two Values for equivalence.
361 unsigned getRawSubclassOptionalData() const {
362 return SubclassOptionalData;
365 /// \brief Clear the optional flags contained in this value.
366 void clearSubclassOptionalData() {
367 SubclassOptionalData = 0;
370 /// \brief Check the optional flags for equality.
371 bool hasSameSubclassOptionalData(const Value *V) const {
372 return SubclassOptionalData == V->SubclassOptionalData;
375 /// \brief Clear any optional flags not set in the given Value.
376 void intersectOptionalDataWith(const Value *V) {
377 SubclassOptionalData &= V->SubclassOptionalData;
380 /// \brief Return true if there is a value handle associated with this value.
381 bool hasValueHandle() const { return HasValueHandle; }
383 /// \brief Return true if there is metadata referencing this value.
384 bool isUsedByMetadata() const { return IsUsedByMD; }
386 /// \brief Strip off pointer casts, all-zero GEPs, and aliases.
388 /// Returns the original uncasted value. If this is called on a non-pointer
389 /// value, it returns 'this'.
390 Value *stripPointerCasts();
391 const Value *stripPointerCasts() const {
392 return const_cast<Value*>(this)->stripPointerCasts();
395 /// \brief Strip off pointer casts and all-zero GEPs.
397 /// Returns the original uncasted value. If this is called on a non-pointer
398 /// value, it returns 'this'.
399 Value *stripPointerCastsNoFollowAliases();
400 const Value *stripPointerCastsNoFollowAliases() const {
401 return const_cast<Value*>(this)->stripPointerCastsNoFollowAliases();
404 /// \brief Strip off pointer casts and all-constant inbounds GEPs.
406 /// Returns the original pointer value. If this is called on a non-pointer
407 /// value, it returns 'this'.
408 Value *stripInBoundsConstantOffsets();
409 const Value *stripInBoundsConstantOffsets() const {
410 return const_cast<Value*>(this)->stripInBoundsConstantOffsets();
413 /// \brief Accumulate offsets from \a stripInBoundsConstantOffsets().
415 /// Stores the resulting constant offset stripped into the APInt provided.
416 /// The provided APInt will be extended or truncated as needed to be the
417 /// correct bitwidth for an offset of this pointer type.
419 /// If this is called on a non-pointer value, it returns 'this'.
420 Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
422 const Value *stripAndAccumulateInBoundsConstantOffsets(const DataLayout &DL,
423 APInt &Offset) const {
424 return const_cast<Value *>(this)
425 ->stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
428 /// \brief Strip off pointer casts and inbounds GEPs.
430 /// Returns the original pointer value. If this is called on a non-pointer
431 /// value, it returns 'this'.
432 Value *stripInBoundsOffsets();
433 const Value *stripInBoundsOffsets() const {
434 return const_cast<Value*>(this)->stripInBoundsOffsets();
437 /// \brief Translate PHI node to its predecessor from the given basic block.
439 /// If this value is a PHI node with CurBB as its parent, return the value in
440 /// the PHI node corresponding to PredBB. If not, return ourself. This is
441 /// useful if you want to know the value something has in a predecessor
443 Value *DoPHITranslation(const BasicBlock *CurBB, const BasicBlock *PredBB);
445 const Value *DoPHITranslation(const BasicBlock *CurBB,
446 const BasicBlock *PredBB) const{
447 return const_cast<Value*>(this)->DoPHITranslation(CurBB, PredBB);
450 /// \brief The maximum alignment for instructions.
452 /// This is the greatest alignment value supported by load, store, and alloca
453 /// instructions, and global values.
454 static const unsigned MaxAlignmentExponent = 29;
455 static const unsigned MaximumAlignment = 1u << MaxAlignmentExponent;
457 /// \brief Mutate the type of this Value to be of the specified type.
459 /// Note that this is an extremely dangerous operation which can create
460 /// completely invalid IR very easily. It is strongly recommended that you
461 /// recreate IR objects with the right types instead of mutating them in
463 void mutateType(Type *Ty) {
467 /// \brief Sort the use-list.
469 /// Sorts the Value's use-list by Cmp using a stable mergesort. Cmp is
470 /// expected to compare two \a Use references.
471 template <class Compare> void sortUseList(Compare Cmp);
473 /// \brief Reverse the use-list.
474 void reverseUseList();
477 /// \brief Merge two lists together.
479 /// Merges \c L and \c R using \c Cmp. To enable stable sorts, always pushes
480 /// "equal" items from L before items from R.
482 /// \return the first element in the list.
484 /// \note Completely ignores \a Use::Prev (doesn't read, doesn't update).
485 template <class Compare>
486 static Use *mergeUseLists(Use *L, Use *R, Compare Cmp) {
488 mergeUseListsImpl(L, R, &Merged, Cmp);
492 /// \brief Tail-recursive helper for \a mergeUseLists().
494 /// \param[out] Next the first element in the list.
495 template <class Compare>
496 static void mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp);
499 unsigned short getSubclassDataFromValue() const { return SubclassData; }
500 void setValueSubclassData(unsigned short D) { SubclassData = D; }
503 inline raw_ostream &operator<<(raw_ostream &OS, const Value &V) {
508 void Use::set(Value *V) {
509 if (Val) removeFromList();
511 if (V) V->addUse(*this);
514 template <class Compare> void Value::sortUseList(Compare Cmp) {
515 if (!UseList || !UseList->Next)
516 // No need to sort 0 or 1 uses.
519 // Note: this function completely ignores Prev pointers until the end when
520 // they're fixed en masse.
522 // Create a binomial vector of sorted lists, visiting uses one at a time and
523 // merging lists as necessary.
524 const unsigned MaxSlots = 32;
525 Use *Slots[MaxSlots];
527 // Collect the first use, turning it into a single-item list.
528 Use *Next = UseList->Next;
529 UseList->Next = nullptr;
530 unsigned NumSlots = 1;
533 // Collect all but the last use.
536 Next = Current->Next;
538 // Turn Current into a single-item list.
539 Current->Next = nullptr;
541 // Save Current in the first available slot, merging on collisions.
543 for (I = 0; I < NumSlots; ++I) {
547 // Merge two lists, doubling the size of Current and emptying slot I.
549 // Since the uses in Slots[I] originally preceded those in Current, send
550 // Slots[I] in as the left parameter to maintain a stable sort.
551 Current = mergeUseLists(Slots[I], Current, Cmp);
554 // Check if this is a new slot.
557 assert(NumSlots <= MaxSlots && "Use list bigger than 2^32");
560 // Found an open slot.
564 // Merge all the lists together.
565 assert(Next && "Expected one more Use");
566 assert(!Next->Next && "Expected only one Use");
568 for (unsigned I = 0; I < NumSlots; ++I)
570 // Since the uses in Slots[I] originally preceded those in UseList, send
571 // Slots[I] in as the left parameter to maintain a stable sort.
572 UseList = mergeUseLists(Slots[I], UseList, Cmp);
574 // Fix the Prev pointers.
575 for (Use *I = UseList, **Prev = &UseList; I; I = I->Next) {
581 template <class Compare>
582 void Value::mergeUseListsImpl(Use *L, Use *R, Use **Next, Compare Cmp) {
593 mergeUseListsImpl(L, R->Next, &R->Next, Cmp);
597 mergeUseListsImpl(L->Next, R, &L->Next, Cmp);
600 // isa - Provide some specializations of isa so that we don't have to include
601 // the subtype header files to test to see if the value is a subclass...
603 template <> struct isa_impl<Constant, Value> {
604 static inline bool doit(const Value &Val) {
605 return Val.getValueID() >= Value::ConstantFirstVal &&
606 Val.getValueID() <= Value::ConstantLastVal;
610 template <> struct isa_impl<Argument, Value> {
611 static inline bool doit (const Value &Val) {
612 return Val.getValueID() == Value::ArgumentVal;
616 template <> struct isa_impl<InlineAsm, Value> {
617 static inline bool doit(const Value &Val) {
618 return Val.getValueID() == Value::InlineAsmVal;
622 template <> struct isa_impl<Instruction, Value> {
623 static inline bool doit(const Value &Val) {
624 return Val.getValueID() >= Value::InstructionVal;
628 template <> struct isa_impl<BasicBlock, Value> {
629 static inline bool doit(const Value &Val) {
630 return Val.getValueID() == Value::BasicBlockVal;
634 template <> struct isa_impl<Function, Value> {
635 static inline bool doit(const Value &Val) {
636 return Val.getValueID() == Value::FunctionVal;
640 template <> struct isa_impl<GlobalVariable, Value> {
641 static inline bool doit(const Value &Val) {
642 return Val.getValueID() == Value::GlobalVariableVal;
646 template <> struct isa_impl<GlobalAlias, Value> {
647 static inline bool doit(const Value &Val) {
648 return Val.getValueID() == Value::GlobalAliasVal;
652 template <> struct isa_impl<GlobalValue, Value> {
653 static inline bool doit(const Value &Val) {
654 return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
658 template <> struct isa_impl<GlobalObject, Value> {
659 static inline bool doit(const Value &Val) {
660 return isa<GlobalVariable>(Val) || isa<Function>(Val);
664 // Value* is only 4-byte aligned.
666 class PointerLikeTypeTraits<Value*> {
669 static inline void *getAsVoidPointer(PT P) { return P; }
670 static inline PT getFromVoidPointer(void *P) {
671 return static_cast<PT>(P);
673 enum { NumLowBitsAvailable = 2 };
676 // Create wrappers for C Binding types (see CBindingWrapping.h).
677 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
679 /* Specialized opaque value conversions.
681 inline Value **unwrap(LLVMValueRef *Vals) {
682 return reinterpret_cast<Value**>(Vals);
686 inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
688 for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
692 return reinterpret_cast<T**>(Vals);
695 inline LLVMValueRef *wrap(const Value **Vals) {
696 return reinterpret_cast<LLVMValueRef*>(const_cast<Value**>(Vals));