1
//===-- llvm/Use.h - Definition of the Use class ----------------*- C++ -*-===//
3
// The LLVM Compiler Infrastructure
5
// This file is distributed under the University of Illinois Open Source
6
// License. See LICENSE.TXT for details.
8
//===----------------------------------------------------------------------===//
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.
14
// Pointer tagging is used to efficiently find the User corresponding
15
// to a Use without having to store a User pointer in every Use. A
16
// User is preceded in memory by all the Uses corresponding to its
17
// operands, and the low bits of one of the fields (Prev) of the Use
18
// class are used to encode offsets to be able to find that User given
19
// a pointer to any Use. For details, see:
21
// http://www.llvm.org/docs/ProgrammersManual.html#UserLayout
23
//===----------------------------------------------------------------------===//
28
#include "llvm/Support/Casting.h"
29
#include "llvm/ADT/PointerIntPair.h"
38
/// Tag - generic tag type for (at least 32 bit) pointers
39
enum Tag { noTag, tagOne, tagTwo, tagThree };
41
// Use** is only 4-byte aligned.
43
class PointerLikeTypeTraits<Use**> {
45
static inline void *getAsVoidPointer(Use** P) { return P; }
46
static inline Use **getFromVoidPointer(void *P) {
47
return static_cast<Use**>(P);
49
enum { NumLowBitsAvailable = 2 };
52
//===----------------------------------------------------------------------===//
54
//===----------------------------------------------------------------------===//
56
/// Use is here to make keeping the "use" list of a Value up-to-date really
60
/// swap - provide a fast substitute to std::swap<Use>
61
/// that also works with less standard-compliant compilers
65
/// Copy ctor - do not implement
68
/// Destructor - Only for zap()
70
if (Val) removeFromList();
73
/// Default ctor - This leaves the Use completely uninitialized. The only
74
/// thing that is valid to do with this use is to call the "init" method.
76
enum PrevPtrTag { zeroDigitTag = noTag
77
, oneDigitTag = tagOne
79
, fullStopTag = tagThree };
82
/// Normally Use will just implicitly convert to a Value* that it holds.
83
operator Value*() const { return Val; }
85
/// If implicit conversion to Value* doesn't work, the get() method returns
87
Value *get() const { return Val; }
89
/// getUser - This returns the User that contains this Use. For an
90
/// instruction operand, for example, this will return the instruction.
91
User *getUser() const;
93
inline void set(Value *Val);
95
Value *operator=(Value *RHS) {
99
const Use &operator=(const Use &RHS) {
104
Value *operator->() { return Val; }
105
const Value *operator->() const { return Val; }
107
Use *getNext() const { return Next; }
110
/// zap - This is used to destroy Use operands when the number of operands of
112
static void zap(Use *Start, const Use *Stop, bool del = false);
114
/// getPrefix - Return deletable pointer if appropriate
117
const Use* getImpliedUser() const;
118
static Use *initTags(Use *Start, Use *Stop, ptrdiff_t Done = 0);
122
PointerIntPair<Use**, 2, PrevPtrTag> Prev;
124
void setPrev(Use **NewPrev) {
125
Prev.setPointer(NewPrev);
127
void addToList(Use **List) {
129
if (Next) Next->setPrev(&Next);
133
void removeFromList() {
134
Use **StrippedPrev = Prev.getPointer();
135
*StrippedPrev = Next;
136
if (Next) Next->setPrev(StrippedPrev);
143
// simplify_type - Allow clients to treat uses just like values when using
144
// casting operators.
145
template<> struct simplify_type<Use> {
146
typedef Value* SimpleType;
147
static SimpleType getSimplifiedValue(const Use &Val) {
148
return static_cast<SimpleType>(Val.get());
151
template<> struct simplify_type<const Use> {
152
typedef Value* SimpleType;
153
static SimpleType getSimplifiedValue(const Use &Val) {
154
return static_cast<SimpleType>(Val.get());
160
template<typename UserTy> // UserTy == 'User' or 'const User'
161
class value_use_iterator : public std::iterator<std::forward_iterator_tag,
162
UserTy*, ptrdiff_t> {
163
typedef std::iterator<std::forward_iterator_tag, UserTy*, ptrdiff_t> super;
164
typedef value_use_iterator<UserTy> _Self;
167
explicit value_use_iterator(Use *u) : U(u) {}
170
typedef typename super::reference reference;
171
typedef typename super::pointer pointer;
173
value_use_iterator(const _Self &I) : U(I.U) {}
174
value_use_iterator() {}
176
bool operator==(const _Self &x) const {
179
bool operator!=(const _Self &x) const {
180
return !operator==(x);
183
/// atEnd - return true if this iterator is equal to use_end() on the value.
184
bool atEnd() const { return U == 0; }
186
// Iterator traversal: forward iteration only
187
_Self &operator++() { // Preincrement
188
assert(U && "Cannot increment end iterator!");
192
_Self operator++(int) { // Postincrement
193
_Self tmp = *this; ++*this; return tmp;
196
// Retrieve a pointer to the current User.
197
UserTy *operator*() const {
198
assert(U && "Cannot dereference end iterator!");
202
UserTy *operator->() const { return operator*(); }
204
Use &getUse() const { return *U; }
206
/// getOperandNo - Return the operand # of this use in its User. Defined in
209
unsigned getOperandNo() const;
213
template<> struct simplify_type<value_use_iterator<User> > {
214
typedef User* SimpleType;
216
static SimpleType getSimplifiedValue(const value_use_iterator<User> &Val) {
221
template<> struct simplify_type<const value_use_iterator<User> >
222
: public simplify_type<value_use_iterator<User> > {};
224
template<> struct simplify_type<value_use_iterator<const User> > {
225
typedef const User* SimpleType;
227
static SimpleType getSimplifiedValue(const
228
value_use_iterator<const User> &Val) {
233
template<> struct simplify_type<const value_use_iterator<const User> >
234
: public simplify_type<value_use_iterator<const User> > {};
236
} // End llvm namespace