1 //===-- Use.cpp - Implement the Use class ---------------------------------===//
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
9 #include "llvm/IR/Use.h"
10 #include "llvm/IR/User.h"
11 #include "llvm/IR/Value.h"
12 #include <new>
13
14 namespace llvm {
15
swap(Use & RHS)16 void Use::swap(Use &RHS) {
17 if (Val == RHS.Val)
18 return;
19
20 if (Val)
21 removeFromList();
22
23 Value *OldVal = Val;
24 if (RHS.Val) {
25 RHS.removeFromList();
26 Val = RHS.Val;
27 Val->addUse(*this);
28 } else {
29 Val = nullptr;
30 }
31
32 if (OldVal) {
33 RHS.Val = OldVal;
34 RHS.Val->addUse(RHS);
35 } else {
36 RHS.Val = nullptr;
37 }
38 }
39
getUser() const40 User *Use::getUser() const {
41 const Use *End = getImpliedUser();
42 const UserRef *ref = reinterpret_cast<const UserRef *>(End);
43 return ref->getInt() ? ref->getPointer()
44 : reinterpret_cast<User *>(const_cast<Use *>(End));
45 }
46
getOperandNo() const47 unsigned Use::getOperandNo() const {
48 return this - getUser()->op_begin();
49 }
50
51 // Sets up the waymarking algorithm's tags for a series of Uses. See the
52 // algorithm details here:
53 //
54 // http://www.llvm.org/docs/ProgrammersManual.html#the-waymarking-algorithm
55 //
initTags(Use * const Start,Use * Stop)56 Use *Use::initTags(Use *const Start, Use *Stop) {
57 ptrdiff_t Done = 0;
58 while (Done < 20) {
59 if (Start == Stop--)
60 return Start;
61 static const PrevPtrTag tags[20] = {
62 fullStopTag, oneDigitTag, stopTag, oneDigitTag, oneDigitTag,
63 stopTag, zeroDigitTag, oneDigitTag, oneDigitTag, stopTag,
64 zeroDigitTag, oneDigitTag, zeroDigitTag, oneDigitTag, stopTag,
65 oneDigitTag, oneDigitTag, oneDigitTag, oneDigitTag, stopTag};
66 new (Stop) Use(tags[Done++]);
67 }
68
69 ptrdiff_t Count = Done;
70 while (Start != Stop) {
71 --Stop;
72 if (!Count) {
73 new (Stop) Use(stopTag);
74 ++Done;
75 Count = Done;
76 } else {
77 new (Stop) Use(PrevPtrTag(Count & 1));
78 Count >>= 1;
79 ++Done;
80 }
81 }
82
83 return Start;
84 }
85
zap(Use * Start,const Use * Stop,bool del)86 void Use::zap(Use *Start, const Use *Stop, bool del) {
87 while (Start != Stop)
88 (--Stop)->~Use();
89 if (del)
90 ::operator delete(Start);
91 }
92
getImpliedUser() const93 const Use *Use::getImpliedUser() const {
94 const Use *Current = this;
95
96 while (true) {
97 unsigned Tag = (Current++)->Prev.getInt();
98 switch (Tag) {
99 case zeroDigitTag:
100 case oneDigitTag:
101 continue;
102
103 case stopTag: {
104 ++Current;
105 ptrdiff_t Offset = 1;
106 while (true) {
107 unsigned Tag = Current->Prev.getInt();
108 switch (Tag) {
109 case zeroDigitTag:
110 case oneDigitTag:
111 ++Current;
112 Offset = (Offset << 1) + Tag;
113 continue;
114 default:
115 return Current + Offset;
116 }
117 }
118 }
119
120 case fullStopTag:
121 return Current;
122 }
123 }
124 }
125
126 } // End llvm namespace
127