Coverage Report

Created: 2019-07-24 05:18

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/IR/Use.h
Line
Count
Source
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"
28
#include "llvm/ADT/PointerIntPair.h"
29
#include "llvm/Support/CBindingWrapping.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
///
45
/// The pointer to the used Value is explicit, and the pointer to the User is
46
/// implicit. The implicit pointer is found via a waymarking algorithm
47
/// described in the programmer's manual:
48
///
49
///   http://www.llvm.org/docs/ProgrammersManual.html#the-waymarking-algorithm
50
///
51
/// This is essentially the single most memory intensive object in LLVM because
52
/// of the number of uses in the system. At the same time, the constant time
53
/// operations it allows are essential to many optimizations having reasonable
54
/// time complexity.
55
class Use {
56
public:
57
  Use(const Use &U) = delete;
58
59
  /// Provide a fast substitute to std::swap<Use>
60
  /// that also works with less standard-compliant compilers
61
  void swap(Use &RHS);
62
63
  /// Pointer traits for the UserRef PointerIntPair. This ensures we always
64
  /// use the LSB regardless of pointer alignment on different targets.
65
  struct UserRefPointerTraits {
66
5.79M
    static inline void *getAsVoidPointer(User *P) { return P; }
67
68
71.9M
    static inline User *getFromVoidPointer(void *P) {
69
71.9M
      return (User *)P;
70
71.9M
    }
71
72
    enum { NumLowBitsAvailable = 1 };
73
  };
74
75
  // A type for the word following an array of hung-off Uses in memory, which is
76
  // a pointer back to their User with the bottom bit set.
77
  using UserRef = PointerIntPair<User *, 1, unsigned, UserRefPointerTraits>;
78
79
  /// Pointer traits for the Prev PointerIntPair. This ensures we always use
80
  /// the two LSBs regardless of pointer alignment on different targets.
81
  struct PrevPointerTraits {
82
361M
    static inline void *getAsVoidPointer(Use **P) { return P; }
83
84
137M
    static inline Use **getFromVoidPointer(void *P) {
85
137M
      return (Use **)P;
86
137M
    }
87
88
    enum { NumLowBitsAvailable = 2 };
89
  };
90
91
private:
92
  /// Destructor - Only for zap()
93
84.6M
  ~Use() {
94
84.6M
    if (Val)
95
42.7M
      removeFromList();
96
84.6M
  }
97
98
  enum PrevPtrTag { zeroDigitTag, oneDigitTag, stopTag, fullStopTag };
99
100
  /// Constructor
101
117M
  Use(PrevPtrTag tag) { Prev.setInt(tag); }
102
103
public:
104
  friend class Value;
105
106
5.91G
  operator Value *() const { return Val; }
107
6.40G
  Value *get() const { return Val; }
108
109
  /// Returns the User that contains this Use.
110
  ///
111
  /// For an instruction operand, for example, this will return the
112
  /// instruction.
113
  User *getUser() const LLVM_READONLY;
114
115
  inline void set(Value *Val);
116
117
  inline Value *operator=(Value *RHS);
118
  inline const Use &operator=(const Use &RHS);
119
120
78.3M
  Value *operator->() { return Val; }
121
4.61M
  const Value *operator->() const { return Val; }
122
123
1.73G
  Use *getNext() const { return Next; }
124
125
  /// Return the operand # of this use in its User.
126
  unsigned getOperandNo() const;
127
128
  /// Initializes the waymarking tags on an array of Uses.
129
  ///
130
  /// This sets up the array of Uses such that getUser() can find the User from
131
  /// any of those Uses.
132
  static Use *initTags(Use *Start, Use *Stop);
133
134
  /// Destroys Use operands when the number of operands of
135
  /// a User changes.
136
  static void zap(Use *Start, const Use *Stop, bool del = false);
137
138
private:
139
  const Use *getImpliedUser() const LLVM_READONLY;
140
141
  Value *Val = nullptr;
142
  Use *Next = nullptr;
143
  PointerIntPair<Use **, 2, PrevPtrTag, PrevPointerTraits> Prev;
144
145
361M
  void setPrev(Use **NewPrev) { Prev.setPointer(NewPrev); }
146
147
168M
  void addToList(Use **List) {
148
168M
    Next = *List;
149
168M
    if (Next)
150
115M
      Next->setPrev(&Next);
151
168M
    setPrev(List);
152
168M
    *List = this;
153
168M
  }
154
155
137M
  void removeFromList() {
156
137M
    Use **StrippedPrev = Prev.getPointer();
157
137M
    *StrippedPrev = Next;
158
137M
    if (Next)
159
77.3M
      Next->setPrev(StrippedPrev);
160
137M
  }
161
};
162
163
/// Allow clients to treat uses just like values when using
164
/// casting operators.
165
template <> struct simplify_type<Use> {
166
  using SimpleType = Value *;
167
168
59.1M
  static SimpleType getSimplifiedValue(Use &Val) { return Val.get(); }
169
};
170
template <> struct simplify_type<const Use> {
171
  using SimpleType = /*const*/ Value *;
172
173
1.03G
  static SimpleType getSimplifiedValue(const Use &Val) { return Val.get(); }
174
};
175
176
// Create wrappers for C Binding types (see CBindingWrapping.h).
177
DEFINE_SIMPLE_CONVERSION_FUNCTIONS(Use, LLVMUseRef)
178
179
} // end namespace llvm
180
181
#endif // LLVM_IR_USE_H