1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
|
//===-- llvm/Use.h - Definition of the Use class ----------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This defines the Use class. The Use class represents the operand of an
/// instruction or some other User instance which refers to a Value. The Use
/// class keeps the "use list" of the referenced value up to date.
///
/// Pointer tagging is used to efficiently find the User corresponding to a Use
/// without having to store a User pointer in every Use. A User is preceded in
/// memory by all the Uses corresponding to its operands, and the low bits of
/// one of the fields (Prev) of the Use class are used to encode offsets to be
/// able to find that User given a pointer to any Use. For details, see:
///
/// http://www.llvm.org/docs/ProgrammersManual.html#UserLayout
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_IR_USE_H
#define LLVM_IR_USE_H
#include "llvm-c/Core.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/Support/CBindingWrapping.h"
#include "llvm/Support/Compiler.h"
#include <cstddef>
#include <iterator>
namespace llvm {
class Value;
class User;
class Use;
template <typename> struct simplify_type;
// Use** is only 4-byte aligned.
template <> class PointerLikeTypeTraits<Use **> {
public:
static inline void *getAsVoidPointer(Use **P) { return P; }
static inline Use **getFromVoidPointer(void *P) {
return static_cast<Use **>(P);
}
enum { NumLowBitsAvailable = 2 };
};
/// \brief A Use represents the edge between a Value definition and its users.
///
/// This is notionally a two-dimensional linked list. It supports traversing
/// all of the uses for a particular value definition. It also supports jumping
/// directly to the used value when we arrive from the User's operands, and
/// jumping directly to the User when we arrive from the Value's uses.
///
/// The pointer to the used Value is explicit, and the pointer to the User is
/// implicit. The implicit pointer is found via a waymarking algorithm
/// described in the programmer's manual:
///
/// http://www.llvm.org/docs/ProgrammersManual.html#the-waymarking-algorithm
///
/// This is essentially the single most memory intensive object in LLVM because
/// of the number of uses in the system. At the same time, the constant time
/// operations it allows are essential to many optimizations having reasonable
/// time complexity.
class Use {
public:
/// \brief Provide a fast substitute to std::swap<Use>
/// that also works with less standard-compliant compilers
void swap(Use &RHS);
// A type for the word following an array of hung-off Uses in memory, which is
// a pointer back to their User with the bottom bit set.
typedef PointerIntPair<User *, 1, unsigned> UserRef;
private:
Use(const Use &U) = delete;
/// Destructor - Only for zap()
~Use() {
if (Val)
removeFromList();
}
enum PrevPtrTag { zeroDigitTag, oneDigitTag, stopTag, fullStopTag };
/// Constructor
Use(PrevPtrTag tag) : Val(nullptr) { Prev.setInt(tag); }
public:
operator Value *() const { return Val; }
Value *get() const { return Val; }
/// \brief Returns the User that contains this Use.
///
/// For an instruction operand, for example, this will return the
/// instruction.
User *getUser() const;
inline void set(Value *Val);
Value *operator=(Value *RHS) {
set(RHS);
return RHS;
}
const Use &operator=(const Use &RHS) {
set(RHS.Val);
return *this;
}
Value *operator->() { return Val; }
const Value *operator->() const { return Val; }
Use *getNext() const { return Next; }
/// \brief Return the operand # of this use in its User.
unsigned getOperandNo() const;
/// \brief Initializes the waymarking tags on an array of Uses.
///
/// This sets up the array of Uses such that getUser() can find the User from
/// any of those Uses.
static Use *initTags(Use *Start, Use *Stop);
/// \brief Destroys Use operands when the number of operands of
/// a User changes.
static void zap(Use *Start, const Use *Stop, bool del = false);
private:
const Use *getImpliedUser() const;
Value *Val;
Use *Next;
PointerIntPair<Use **, 2, PrevPtrTag> Prev;
void setPrev(Use **NewPrev) { Prev.setPointer(NewPrev); }
void addToList(Use **List) {
Next = *List;
if (Next)
Next->setPrev(&Next);
setPrev(List);
*List = this;
}
void removeFromList() {
Use **StrippedPrev = Prev.getPointer();
*StrippedPrev = Next;
if (Next)
Next->setPrev(StrippedPrev);
}
friend class Value;
};
/// \brief Allow clients to treat uses just like values when using
/// casting operators.
template <> struct simplify_type<Use> {
typedef Value *SimpleType;
static SimpleType getSimplifiedValue(Use &Val) { return Val.get(); }
};
template <> struct simplify_type<const Use> {
typedef /*const*/ Value *SimpleType;
static SimpleType getSimplifiedValue(const Use &Val) { return Val.get(); }
};
// Create wrappers for C Binding types (see CBindingWrapping.h).
DEFINE_SIMPLE_CONVERSION_FUNCTIONS(Use, LLVMUseRef)
}
#endif
|
