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"
40 // Use** is only 4-byte aligned.
42 class PointerLikeTypeTraits<Use**> {
44 static inline void *getAsVoidPointer(Use** P) { return P; }
45 static inline Use **getFromVoidPointer(void *P) {
46 return static_cast<Use**>(P);
48 enum { NumLowBitsAvailable = 2 };
51 //===----------------------------------------------------------------------===//
53 //===----------------------------------------------------------------------===//
55 /// Use is here to make keeping the "use" list of a Value up-to-date really
59 /// swap - provide a fast substitute to std::swap<Use>
60 /// that also works with less standard-compliant compilers
64 /// Copy ctor - do not implement
67 /// Destructor - Only for zap()
69 if (Val) removeFromList();
72 enum PrevPtrTag { zeroDigitTag
78 Use(PrevPtrTag tag) : Val(0) {
83 /// Normally Use will just implicitly convert to a Value* that it holds.
84 operator Value*() const { return Val; }
86 /// If implicit conversion to Value* doesn't work, the get() method returns
88 Value *get() const { return Val; }
90 /// getUser - This returns the User that contains this Use. For an
91 /// instruction operand, for example, this will return the instruction.
92 User *getUser() const;
94 inline void set(Value *Val);
96 Value *operator=(Value *RHS) {
100 const Use &operator=(const Use &RHS) {
105 Value *operator->() { return Val; }
106 const Value *operator->() const { return Val; }
108 Use *getNext() const { return Next; }
111 /// zap - This is used to destroy Use operands when the number of operands of
113 static void zap(Use *Start, const Use *Stop, bool del = false);
116 const Use* getImpliedUser() const;
117 static Use *initTags(Use *Start, Use *Stop);
121 PointerIntPair<Use**, 2, PrevPtrTag> Prev;
123 void setPrev(Use **NewPrev) {
124 Prev.setPointer(NewPrev);
126 void addToList(Use **List) {
128 if (Next) Next->setPrev(&Next);
132 void removeFromList() {
133 Use **StrippedPrev = Prev.getPointer();
134 *StrippedPrev = Next;
135 if (Next) Next->setPrev(StrippedPrev);
142 // simplify_type - Allow clients to treat uses just like values when using
143 // casting operators.
144 template<> struct simplify_type<Use> {
145 typedef Value* SimpleType;
146 static SimpleType getSimplifiedValue(const Use &Val) {
147 return static_cast<SimpleType>(Val.get());
150 template<> struct simplify_type<const Use> {
151 typedef Value* SimpleType;
152 static SimpleType getSimplifiedValue(const Use &Val) {
153 return static_cast<SimpleType>(Val.get());
159 template<typename UserTy> // UserTy == 'User' or 'const User'
160 class value_use_iterator : public std::iterator<std::forward_iterator_tag,
161 UserTy*, ptrdiff_t> {
162 typedef std::iterator<std::forward_iterator_tag, UserTy*, ptrdiff_t> super;
163 typedef value_use_iterator<UserTy> _Self;
166 explicit value_use_iterator(Use *u) : U(u) {}
169 typedef typename super::reference reference;
170 typedef typename super::pointer pointer;
172 value_use_iterator(const _Self &I) : U(I.U) {}
173 value_use_iterator() {}
175 bool operator==(const _Self &x) const {
178 bool operator!=(const _Self &x) const {
179 return !operator==(x);
182 /// atEnd - return true if this iterator is equal to use_end() on the value.
183 bool atEnd() const { return U == 0; }
185 // Iterator traversal: forward iteration only
186 _Self &operator++() { // Preincrement
187 assert(U && "Cannot increment end iterator!");
191 _Self operator++(int) { // Postincrement
192 _Self tmp = *this; ++*this; return tmp;
195 // Retrieve a pointer to the current User.
196 UserTy *operator*() const {
197 assert(U && "Cannot dereference end iterator!");
201 UserTy *operator->() const { return operator*(); }
203 Use &getUse() const { return *U; }
205 /// getOperandNo - Return the operand # of this use in its User. Defined in
208 unsigned getOperandNo() const;
211 //===----------------------------------------------------------------------===//
212 // AugmentedUse layout struct
213 //===----------------------------------------------------------------------===//
215 struct AugmentedUse : public Use {
216 PointerIntPair<User*, 1, unsigned> ref;
217 AugmentedUse(); // not implemented
220 } // End llvm namespace