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Use.h
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1 //===-- llvm/Use.h - Definition of the Use class ----------------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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.
13 //
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:
20 //
21 // http://www.llvm.org/docs/ProgrammersManual.html#UserLayout
22 //
23 //===----------------------------------------------------------------------===//
24 
25 #ifndef LLVM_IR_USE_H
26 #define LLVM_IR_USE_H
27 
30 #include "llvm/Support/Compiler.h"
31 #include "llvm-c/Core.h"
32 #include <cstddef>
33 #include <iterator>
34 
35 namespace llvm {
36 
37 class Value;
38 class User;
39 class Use;
40 template<typename>
41 struct simplify_type;
42 
43 // Use** is only 4-byte aligned.
44 template<>
46 public:
47  static inline void *getAsVoidPointer(Use** P) { return P; }
48  static inline Use **getFromVoidPointer(void *P) {
49  return static_cast<Use**>(P);
50  }
51  enum { NumLowBitsAvailable = 2 };
52 };
53 
54 //===----------------------------------------------------------------------===//
55 // Use Class
56 //===----------------------------------------------------------------------===//
57 
58 /// Use is here to make keeping the "use" list of a Value up-to-date really
59 /// easy.
60 class Use {
61 public:
62  /// swap - provide a fast substitute to std::swap<Use>
63  /// that also works with less standard-compliant compilers
64  void swap(Use &RHS);
65 
66  // A type for the word following an array of hung-off Uses in memory, which is
67  // a pointer back to their User with the bottom bit set.
69 
70 private:
71  Use(const Use &U) LLVM_DELETED_FUNCTION;
72 
73  /// Destructor - Only for zap()
74  ~Use() {
75  if (Val) removeFromList();
76  }
77 
78  enum PrevPtrTag { zeroDigitTag
79  , oneDigitTag
80  , stopTag
81  , fullStopTag };
82 
83  /// Constructor
84  Use(PrevPtrTag tag) : Val(0) {
85  Prev.setInt(tag);
86  }
87 
88 public:
89  /// Normally Use will just implicitly convert to a Value* that it holds.
90  operator Value*() const { return Val; }
91 
92  /// If implicit conversion to Value* doesn't work, the get() method returns
93  /// the Value*.
94  Value *get() const { return Val; }
95 
96  /// getUser - This returns the User that contains this Use. For an
97  /// instruction operand, for example, this will return the instruction.
98  User *getUser() const;
99 
100  inline void set(Value *Val);
101 
103  set(RHS);
104  return RHS;
105  }
106  const Use &operator=(const Use &RHS) {
107  set(RHS.Val);
108  return *this;
109  }
110 
111  Value *operator->() { return Val; }
112  const Value *operator->() const { return Val; }
113 
114  Use *getNext() const { return Next; }
115 
116 
117  /// initTags - initialize the waymarking tags on an array of Uses, so that
118  /// getUser() can find the User from any of those Uses.
119  static Use *initTags(Use *Start, Use *Stop);
120 
121  /// zap - This is used to destroy Use operands when the number of operands of
122  /// a User changes.
123  static void zap(Use *Start, const Use *Stop, bool del = false);
124 
125 private:
126  const Use* getImpliedUser() const;
127 
128  Value *Val;
129  Use *Next;
131 
132  void setPrev(Use **NewPrev) {
133  Prev.setPointer(NewPrev);
134  }
135  void addToList(Use **List) {
136  Next = *List;
137  if (Next) Next->setPrev(&Next);
138  setPrev(List);
139  *List = this;
140  }
141  void removeFromList() {
142  Use **StrippedPrev = Prev.getPointer();
143  *StrippedPrev = Next;
144  if (Next) Next->setPrev(StrippedPrev);
145  }
146 
147  friend class Value;
148 };
149 
150 // simplify_type - Allow clients to treat uses just like values when using
151 // casting operators.
152 template<> struct simplify_type<Use> {
153  typedef Value* SimpleType;
155  return Val.get();
156  }
157 };
158 template<> struct simplify_type<const Use> {
159  typedef /*const*/ Value* SimpleType;
160  static SimpleType getSimplifiedValue(const Use &Val) {
161  return Val.get();
162  }
163 };
164 
165 
166 
167 template<typename UserTy> // UserTy == 'User' or 'const User'
168 class value_use_iterator : public std::iterator<std::forward_iterator_tag,
169  UserTy*, ptrdiff_t> {
170  typedef std::iterator<std::forward_iterator_tag, UserTy*, ptrdiff_t> super;
172 
173  Use *U;
174  explicit value_use_iterator(Use *u) : U(u) {}
175  friend class Value;
176 public:
177  typedef typename super::reference reference;
178  typedef typename super::pointer pointer;
179 
181 
182  bool operator==(const _Self &x) const {
183  return U == x.U;
184  }
185  bool operator!=(const _Self &x) const {
186  return !operator==(x);
187  }
188 
189  /// atEnd - return true if this iterator is equal to use_end() on the value.
190  bool atEnd() const { return U == 0; }
191 
192  // Iterator traversal: forward iteration only
193  _Self &operator++() { // Preincrement
194  assert(U && "Cannot increment end iterator!");
195  U = U->getNext();
196  return *this;
197  }
198  _Self operator++(int) { // Postincrement
199  _Self tmp = *this; ++*this; return tmp;
200  }
201 
202  // Retrieve a pointer to the current User.
203  UserTy *operator*() const {
204  assert(U && "Cannot dereference end iterator!");
205  return U->getUser();
206  }
207 
208  UserTy *operator->() const { return operator*(); }
209 
210  Use &getUse() const { return *U; }
211 
212  /// getOperandNo - Return the operand # of this use in its User. Defined in
213  /// User.h
214  ///
215  unsigned getOperandNo() const;
216 };
217 
218 // Create wrappers for C Binding types (see CBindingWrapping.h).
220 
221 } // End llvm namespace
222 
223 #endif
const Value * operator->() const
Definition: Use.h:112
super::pointer pointer
Definition: Use.h:178
PointerIntPair< User *, 1, unsigned > UserRef
Definition: Use.h:68
UserTy * operator->() const
Definition: Use.h:208
super::reference reference
Definition: Use.h:177
UserTy * operator*() const
Definition: Use.h:203
#define DEFINE_SIMPLE_CONVERSION_FUNCTIONS(ty, ref)
Definition: Use.h:60
Use * getNext() const
Definition: Use.h:114
const Use & operator=(const Use &RHS)
Definition: Use.h:106
#define P(N)
void set(Value *Val)
Definition: Value.h:356
bool operator!=(const _Self &x) const
Definition: Use.h:185
static Use * initTags(Use *Start, Use *Stop)
Definition: Use.cpp:89
void swap(Use &RHS)
Definition: Use.cpp:23
Value * operator->()
Definition: Use.h:111
_Self operator++(int)
Definition: Use.h:198
Value * get() const
Definition: Use.h:94
User * getUser() const
Definition: Use.cpp:137
static void * getAsVoidPointer(Use **P)
Definition: Use.h:47
unsigned getOperandNo() const
Definition: User.h:199
bool atEnd() const
atEnd - return true if this iterator is equal to use_end() on the value.
Definition: Use.h:190
bool operator==(const _Self &x) const
Definition: Use.h:182
static SimpleType getSimplifiedValue(const Use &Val)
Definition: Use.h:160
#define LLVM_DELETED_FUNCTION
Definition: Compiler.h:137
Value * operator=(Value *RHS)
Definition: Use.h:102
_Self & operator++()
Definition: Use.h:193
Use & getUse() const
Definition: Use.h:210
struct LLVMOpaqueUse * LLVMUseRef
Definition: Core.h:134
LLVM Value Representation.
Definition: Value.h:66
static SimpleType getSimplifiedValue(Use &Val)
Definition: Use.h:154
static Use ** getFromVoidPointer(void *P)
Definition: Use.h:48
static void zap(Use *Start, const Use *Stop, bool del=false)
Definition: Use.cpp:126