1 //===-- llvm/Use.h - Definition of the Use 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 defines the Use class. The Use class represents the operand of an
11 // instruction or some other User instance which refers to a Value. The Use
12 // class keeps the "use list" of the referenced value up to date.
14 // Pointer tagging is used to efficiently find the User corresponding
15 // to a Use without having to store a User pointer in every Use. A
16 // User is preceded in memory by all the Uses corresponding to its
17 // operands, and the low bits of one of the fields (Prev) of the Use
18 // class are used to encode offsets to be able to find that User given
19 // a pointer to any Use. For details, see:
21 // http://www.llvm.org/docs/ProgrammersManual.html#UserLayout
23 //===----------------------------------------------------------------------===//
28 #include "llvm/ADT/PointerIntPair.h"
39 // Use** is only 4-byte aligned.
41 class PointerLikeTypeTraits<Use**> {
43 static inline void *getAsVoidPointer(Use** P) { return P; }
44 static inline Use **getFromVoidPointer(void *P) {
45 return static_cast<Use**>(P);
47 enum { NumLowBitsAvailable = 2 };
50 //===----------------------------------------------------------------------===//
52 //===----------------------------------------------------------------------===//
54 /// Use is here to make keeping the "use" list of a Value up-to-date really
58 /// swap - provide a fast substitute to std::swap<Use>
59 /// that also works with less standard-compliant compilers
63 /// Copy ctor - do not implement
66 /// Destructor - Only for zap()
68 if (Val) removeFromList();
71 enum PrevPtrTag { zeroDigitTag
77 Use(PrevPtrTag tag) : Val(0) {
82 /// Normally Use will just implicitly convert to a Value* that it holds.
83 operator Value*() const { return Val; }
85 /// If implicit conversion to Value* doesn't work, the get() method returns
87 Value *get() const { return Val; }
89 /// getUser - This returns the User that contains this Use. For an
90 /// instruction operand, for example, this will return the instruction.
91 User *getUser() const;
93 inline void set(Value *Val);
95 Value *operator=(Value *RHS) {
99 const Use &operator=(const Use &RHS) {
104 Value *operator->() { return Val; }
105 const Value *operator->() const { return Val; }
107 Use *getNext() const { return Next; }
110 /// zap - This is used to destroy Use operands when the number of operands of
112 static void zap(Use *Start, const Use *Stop, bool del = false);
115 const Use* getImpliedUser() const;
116 static Use *initTags(Use *Start, Use *Stop);
120 PointerIntPair<Use**, 2, PrevPtrTag> Prev;
122 void setPrev(Use **NewPrev) {
123 Prev.setPointer(NewPrev);
125 void addToList(Use **List) {
127 if (Next) Next->setPrev(&Next);
131 void removeFromList() {
132 Use **StrippedPrev = Prev.getPointer();
133 *StrippedPrev = Next;
134 if (Next) Next->setPrev(StrippedPrev);
141 // simplify_type - Allow clients to treat uses just like values when using
142 // casting operators.
143 template<> struct simplify_type<Use> {
144 typedef Value* SimpleType;
145 static SimpleType getSimplifiedValue(const Use &Val) {
146 return static_cast<SimpleType>(Val.get());
149 template<> struct simplify_type<const Use> {
150 typedef Value* SimpleType;
151 static SimpleType getSimplifiedValue(const Use &Val) {
152 return static_cast<SimpleType>(Val.get());
158 template<typename UserTy> // UserTy == 'User' or 'const User'
159 class value_use_iterator : public std::iterator<std::forward_iterator_tag,
160 UserTy*, ptrdiff_t> {
161 typedef std::iterator<std::forward_iterator_tag, UserTy*, ptrdiff_t> super;
162 typedef value_use_iterator<UserTy> _Self;
165 explicit value_use_iterator(Use *u) : U(u) {}
168 typedef typename super::reference reference;
169 typedef typename super::pointer pointer;
171 value_use_iterator(const _Self &I) : U(I.U) {}
172 value_use_iterator() {}
174 bool operator==(const _Self &x) const {
177 bool operator!=(const _Self &x) const {
178 return !operator==(x);
181 /// atEnd - return true if this iterator is equal to use_end() on the value.
182 bool atEnd() const { return U == 0; }
184 // Iterator traversal: forward iteration only
185 _Self &operator++() { // Preincrement
186 assert(U && "Cannot increment end iterator!");
190 _Self operator++(int) { // Postincrement
191 _Self tmp = *this; ++*this; return tmp;
194 // Retrieve a pointer to the current User.
195 UserTy *operator*() const {
196 assert(U && "Cannot dereference end iterator!");
200 UserTy *operator->() const { return operator*(); }
202 Use &getUse() const { return *U; }
204 /// getOperandNo - Return the operand # of this use in its User. Defined in
207 unsigned getOperandNo() const;
210 //===----------------------------------------------------------------------===//
211 // AugmentedUse layout struct
212 //===----------------------------------------------------------------------===//
214 struct AugmentedUse : public Use {
215 PointerIntPair<User*, 1, unsigned> ref;
216 AugmentedUse(); // not implemented
219 } // End llvm namespace