LLVM  13.0.0git
Use.h
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1 //===- llvm/Use.h - Definition of the Use class -----------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 /// \file
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 to a Use
15 /// without having to store a User pointer in every Use. A User is preceded in
16 /// memory by all the Uses corresponding to its operands, and the low bits of
17 /// one of the fields (Prev) of the Use class are used to encode offsets to be
18 /// able to find that User given a pointer to any Use. For details, see:
19 ///
20 /// http://www.llvm.org/docs/ProgrammersManual.html#UserLayout
21 ///
22 //===----------------------------------------------------------------------===//
23 
24 #ifndef LLVM_IR_USE_H
25 #define LLVM_IR_USE_H
26 
27 #include "llvm-c/Types.h"
30 #include "llvm/Support/Compiler.h"
31 
32 namespace llvm {
33 
34 template <typename> struct simplify_type;
35 class User;
36 class Value;
37 
38 /// A Use represents the edge between a Value definition and its users.
39 ///
40 /// This is notionally a two-dimensional linked list. It supports traversing
41 /// all of the uses for a particular value definition. It also supports jumping
42 /// directly to the used value when we arrive from the User's operands, and
43 /// jumping directly to the User when we arrive from the Value's uses.
44 class Use {
45 public:
46  Use(const Use &U) = delete;
47 
48  /// Provide a fast substitute to std::swap<Use>
49  /// that also works with less standard-compliant compilers
50  void swap(Use &RHS);
51 
52 private:
53  /// Destructor - Only for zap()
54  ~Use() {
55  if (Val)
56  removeFromList();
57  }
58 
59  /// Constructor
60  Use(User *Parent) : Parent(Parent) {}
61 
62 public:
63  friend class Value;
64  friend class User;
65 
66  operator Value *() const { return Val; }
67  Value *get() const { return Val; }
68 
69  /// Returns the User that contains this Use.
70  ///
71  /// For an instruction operand, for example, this will return the
72  /// instruction.
73  User *getUser() const { return Parent; };
74 
75  inline void set(Value *Val);
76 
77  inline Value *operator=(Value *RHS);
78  inline const Use &operator=(const Use &RHS);
79 
80  Value *operator->() { return Val; }
81  const Value *operator->() const { return Val; }
82 
83  Use *getNext() const { return Next; }
84 
85  /// Return the operand # of this use in its User.
86  unsigned getOperandNo() const;
87 
88  /// Destroys Use operands when the number of operands of
89  /// a User changes.
90  static void zap(Use *Start, const Use *Stop, bool del = false);
91 
92 private:
93 
94  Value *Val = nullptr;
95  Use *Next = nullptr;
96  Use **Prev = nullptr;
97  User *Parent = nullptr;
98 
99  void addToList(Use **List) {
100  Next = *List;
101  if (Next)
102  Next->Prev = &Next;
103  Prev = List;
104  *Prev = this;
105  }
106 
107  void removeFromList() {
108  *Prev = Next;
109  if (Next)
110  Next->Prev = Prev;
111  }
112 };
113 
114 /// Allow clients to treat uses just like values when using
115 /// casting operators.
116 template <> struct simplify_type<Use> {
117  using SimpleType = Value *;
118 
119  static SimpleType getSimplifiedValue(Use &Val) { return Val.get(); }
120 };
121 template <> struct simplify_type<const Use> {
122  using SimpleType = /*const*/ Value *;
123 
124  static SimpleType getSimplifiedValue(const Use &Val) { return Val.get(); }
125 };
126 
127 // Create wrappers for C Binding types (see CBindingWrapping.h).
129 
130 } // end namespace llvm
131 
132 #endif // LLVM_IR_USE_H
llvm::objcarc::ARCInstKind::User
@ User
could "use" a pointer
llvm
---------------------— PointerInfo ------------------------------------—
Definition: AllocatorList.h:23
llvm::Use::zap
static void zap(Use *Start, const Use *Stop, bool del=false)
Destroys Use operands when the number of operands of a User changes.
Definition: Use.cpp:37
Types.h
llvm::Use::get
Value * get() const
Definition: Use.h:67
llvm::Use::getOperandNo
unsigned getOperandNo() const
Return the operand # of this use in its User.
Definition: Use.cpp:33
CBindingWrapping.h
llvm::Use::operator=
Value * operator=(Value *RHS)
Definition: Value.h:866
DEFINE_SIMPLE_CONVERSION_FUNCTIONS
#define DEFINE_SIMPLE_CONVERSION_FUNCTIONS(ty, ref)
Definition: CBindingWrapping.h:19
LLVMUseRef
struct LLVMOpaqueUse * LLVMUseRef
Used to get the users and usees of a Value.
Definition: Types.h:136
PointerIntPair.h
llvm::Use::operator->
Value * operator->()
Definition: Use.h:80
llvm::simplify_type< const Use >::getSimplifiedValue
static SimpleType getSimplifiedValue(const Use &Val)
Definition: Use.h:124
llvm::User
Definition: User.h:44
llvm::simplify_type
Definition: ilist_iterator.h:178
llvm::Use::getUser
User * getUser() const
Returns the User that contains this Use.
Definition: Use.h:73
llvm::Use::Use
Use(const Use &U)=delete
llvm::Use::set
void set(Value *Val)
Definition: Value.h:860
const
aarch64 promote const
Definition: AArch64PromoteConstant.cpp:232
llvm::simplify_type< Use >::getSimplifiedValue
static SimpleType getSimplifiedValue(Use &Val)
Definition: Use.h:119
Compiler.h
llvm::TargetStackID::Value
Value
Definition: TargetFrameLowering.h:27
llvm::Use::swap
void swap(Use &RHS)
Provide a fast substitute to std::swap<Use> that also works with less standard-compliant compilers.
Definition: Use.cpp:16
llvm::Use::getNext
Use * getNext() const
Definition: Use.h:83
List
const NodeList & List
Definition: RDFGraph.cpp:201
llvm::Use::operator->
const Value * operator->() const
Definition: Use.h:81
llvm::Value
LLVM Value Representation.
Definition: Value.h:75
llvm::Use
A Use represents the edge between a Value definition and its users.
Definition: Use.h:44