1 //===-- Use.cpp - Implement the Use class ---------------------------------===//
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 file implements the algorithm for finding the User of a Use.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "llvm/Value.h"
15
16 namespace llvm {
17
18 //===----------------------------------------------------------------------===//
19 // Use swap Implementation
20 //===----------------------------------------------------------------------===//
21
swap(Use & RHS)22 void Use::swap(Use &RHS) {
23 Value *V1(Val);
24 Value *V2(RHS.Val);
25 if (V1 != V2) {
26 if (V1) {
27 removeFromList();
28 }
29
30 if (V2) {
31 RHS.removeFromList();
32 Val = V2;
33 V2->addUse(*this);
34 } else {
35 Val = 0;
36 }
37
38 if (V1) {
39 RHS.Val = V1;
40 V1->addUse(RHS);
41 } else {
42 RHS.Val = 0;
43 }
44 }
45 }
46
47 //===----------------------------------------------------------------------===//
48 // Use getImpliedUser Implementation
49 //===----------------------------------------------------------------------===//
50
getImpliedUser() const51 const Use *Use::getImpliedUser() const {
52 const Use *Current = this;
53
54 while (true) {
55 unsigned Tag = (Current++)->Prev.getInt();
56 switch (Tag) {
57 case zeroDigitTag:
58 case oneDigitTag:
59 continue;
60
61 case stopTag: {
62 ++Current;
63 ptrdiff_t Offset = 1;
64 while (true) {
65 unsigned Tag = Current->Prev.getInt();
66 switch (Tag) {
67 case zeroDigitTag:
68 case oneDigitTag:
69 ++Current;
70 Offset = (Offset << 1) + Tag;
71 continue;
72 default:
73 return Current + Offset;
74 }
75 }
76 }
77
78 case fullStopTag:
79 return Current;
80 }
81 }
82 }
83
84 //===----------------------------------------------------------------------===//
85 // Use initTags Implementation
86 //===----------------------------------------------------------------------===//
87
initTags(Use * const Start,Use * Stop)88 Use *Use::initTags(Use * const Start, Use *Stop) {
89 ptrdiff_t Done = 0;
90 while (Done < 20) {
91 if (Start == Stop--)
92 return Start;
93 static const PrevPtrTag tags[20] = { fullStopTag, oneDigitTag, stopTag,
94 oneDigitTag, oneDigitTag, stopTag,
95 zeroDigitTag, oneDigitTag, oneDigitTag,
96 stopTag, zeroDigitTag, oneDigitTag,
97 zeroDigitTag, oneDigitTag, stopTag,
98 oneDigitTag, oneDigitTag, oneDigitTag,
99 oneDigitTag, stopTag
100 };
101 new(Stop) Use(tags[Done++]);
102 }
103
104 ptrdiff_t Count = Done;
105 while (Start != Stop) {
106 --Stop;
107 if (!Count) {
108 new(Stop) Use(stopTag);
109 ++Done;
110 Count = Done;
111 } else {
112 new(Stop) Use(PrevPtrTag(Count & 1));
113 Count >>= 1;
114 ++Done;
115 }
116 }
117
118 return Start;
119 }
120
121 //===----------------------------------------------------------------------===//
122 // Use zap Implementation
123 //===----------------------------------------------------------------------===//
124
zap(Use * Start,const Use * Stop,bool del)125 void Use::zap(Use *Start, const Use *Stop, bool del) {
126 while (Start != Stop)
127 (--Stop)->~Use();
128 if (del)
129 ::operator delete(Start);
130 }
131
132 //===----------------------------------------------------------------------===//
133 // Use getUser Implementation
134 //===----------------------------------------------------------------------===//
135
getUser() const136 User *Use::getUser() const {
137 const Use *End = getImpliedUser();
138 const UserRef *ref = reinterpret_cast<const UserRef*>(End);
139 return ref->getInt()
140 ? ref->getPointer()
141 : (User*)End;
142 }
143
144 } // End llvm namespace
145