1//===- llvm/User.h - User class definition ----------------------*- C++ -*-===//
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 class defines the interface that one who uses a Value must implement.
11// Each instance of the Value class keeps track of what User's have handles
12// to it.
13//
14// * Instructions are the largest class of Users.
15// * Constants may be users of other constants (think arrays and stuff)
16//
17//===----------------------------------------------------------------------===//
18
19#ifndef LLVM_IR_USER_H
20#define LLVM_IR_USER_H
21
22#include "llvm/ADT/iterator.h"
23#include "llvm/ADT/iterator_range.h"
24#include "llvm/IR/Use.h"
25#include "llvm/IR/Value.h"
26#include "llvm/Support/Casting.h"
27#include "llvm/Support/Compiler.h"
28#include "llvm/Support/ErrorHandling.h"
29#include <cassert>
30#include <cstddef>
31#include <cstdint>
32#include <iterator>
33
34namespace llvm {
35
36template <typename T> class ArrayRef;
37template <typename T> class MutableArrayRef;
38
39/// Compile-time customization of User operands.
40///
41/// Customizes operand-related allocators and accessors.
42template <class>
43struct OperandTraits;
44
45class User : public Value {
46 template <unsigned>
47 friend struct HungoffOperandTraits;
48
49 LLVM_ATTRIBUTE_ALWAYS_INLINE inline static void *
50 allocateFixedOperandUser(size_t, unsigned, unsigned);
51
52protected:
53 /// Allocate a User with an operand pointer co-allocated.
54 ///
55 /// This is used for subclasses which need to allocate a variable number
56 /// of operands, ie, 'hung off uses'.
57 void *operator new(size_t Size);
58
59 /// Allocate a User with the operands co-allocated.
60 ///
61 /// This is used for subclasses which have a fixed number of operands.
62 void *operator new(size_t Size, unsigned Us);
63
64 /// Allocate a User with the operands co-allocated. If DescBytes is non-zero
65 /// then allocate an additional DescBytes bytes before the operands. These
66 /// bytes can be accessed by calling getDescriptor.
67 ///
68 /// DescBytes needs to be divisible by sizeof(void *). The allocated
69 /// descriptor, if any, is aligned to sizeof(void *) bytes.
70 ///
71 /// This is used for subclasses which have a fixed number of operands.
72 void *operator new(size_t Size, unsigned Us, unsigned DescBytes);
73
74 User(Type *ty, unsigned vty, Use *, unsigned NumOps)
75 : Value(ty, vty) {
76 assert(NumOps < (1u << NumUserOperandsBits) && "Too many operands");
77 NumUserOperands = NumOps;
78 // If we have hung off uses, then the operand list should initially be
79 // null.
80 assert((!HasHungOffUses || !getOperandList()) &&
81 "Error in initializing hung off uses for User");
82 }
83
84 /// Allocate the array of Uses, followed by a pointer
85 /// (with bottom bit set) to the User.
86 /// \param IsPhi identifies callers which are phi nodes and which need
87 /// N BasicBlock* allocated along with N
88 void allocHungoffUses(unsigned N, bool IsPhi = false);
89
90 /// Grow the number of hung off uses. Note that allocHungoffUses
91 /// should be called if there are no uses.
92 void growHungoffUses(unsigned N, bool IsPhi = false);
93
94protected:
95 ~User() = default; // Use deleteValue() to delete a generic Instruction.
96
97public:
98 User(const User &) = delete;
99
100 /// Free memory allocated for User and Use objects.
101 void operator delete(void *Usr);
102 /// Placement delete - required by std, called if the ctor throws.
103 void operator delete(void *Usr, unsigned) {
104 // Note: If a subclass manipulates the information which is required to calculate the
105 // Usr memory pointer, e.g. NumUserOperands, the operator delete of that subclass has
106 // to restore the changed information to the original value, since the dtor of that class
107 // is not called if the ctor fails.
108 User::operator delete(Usr);
109
110#ifndef LLVM_ENABLE_EXCEPTIONS
111 llvm_unreachable("Constructor throws?");
112#endif
113 }
114 /// Placement delete - required by std, called if the ctor throws.
115 void operator delete(void *Usr, unsigned, bool) {
116 // Note: If a subclass manipulates the information which is required to calculate the
117 // Usr memory pointer, e.g. NumUserOperands, the operator delete of that subclass has
118 // to restore the changed information to the original value, since the dtor of that class
119 // is not called if the ctor fails.
120 User::operator delete(Usr);
121
122#ifndef LLVM_ENABLE_EXCEPTIONS
123 llvm_unreachable("Constructor throws?");
124#endif
125 }
126
127protected:
128 template <int Idx, typename U> static Use &OpFrom(const U *that) {
129 return Idx < 0
130 ? OperandTraits<U>::op_end(const_cast<U*>(that))[Idx]
131 : OperandTraits<U>::op_begin(const_cast<U*>(that))[Idx];
132 }
133
134 template <int Idx> Use &Op() {
135 return OpFrom<Idx>(this);
136 }
137 template <int Idx> const Use &Op() const {
138 return OpFrom<Idx>(this);
139 }
140
141private:
142 const Use *getHungOffOperands() const {
143 return *(reinterpret_cast<const Use *const *>(this) - 1);
144 }
145
146 Use *&getHungOffOperands() { return *(reinterpret_cast<Use **>(this) - 1); }
147
148 const Use *getIntrusiveOperands() const {
149 return reinterpret_cast<const Use *>(this) - NumUserOperands;
150 }
151
152 Use *getIntrusiveOperands() {
153 return reinterpret_cast<Use *>(this) - NumUserOperands;
154 }
155
156 void setOperandList(Use *NewList) {
157 assert(HasHungOffUses &&
158 "Setting operand list only required for hung off uses");
159 getHungOffOperands() = NewList;
160 }
161
162public:
163 const Use *getOperandList() const {
164 return HasHungOffUses ? getHungOffOperands() : getIntrusiveOperands();
165 }
166 Use *getOperandList() {
167 return const_cast<Use *>(static_cast<const User *>(this)->getOperandList());
168 }
169
170 Value *getOperand(unsigned i) const {
171 assert(i < NumUserOperands && "getOperand() out of range!");
172 return getOperandList()[i];
173 }
174
175 void setOperand(unsigned i, Value *Val) {
176 assert(i < NumUserOperands && "setOperand() out of range!");
177 assert((!isa<Constant>((const Value*)this) ||
178 isa<GlobalValue>((const Value*)this)) &&
179 "Cannot mutate a constant with setOperand!");
180 getOperandList()[i] = Val;
181 }
182
183 const Use &getOperandUse(unsigned i) const {
184 assert(i < NumUserOperands && "getOperandUse() out of range!");
185 return getOperandList()[i];
186 }
187 Use &getOperandUse(unsigned i) {
188 assert(i < NumUserOperands && "getOperandUse() out of range!");
189 return getOperandList()[i];
190 }
191
192 unsigned getNumOperands() const { return NumUserOperands; }
193
194 /// Returns the descriptor co-allocated with this User instance.
195 ArrayRef<const uint8_t> getDescriptor() const;
196
197 /// Returns the descriptor co-allocated with this User instance.
198 MutableArrayRef<uint8_t> getDescriptor();
199
200 /// Set the number of operands on a GlobalVariable.
201 ///
202 /// GlobalVariable always allocates space for a single operands, but
203 /// doesn't always use it.
204 ///
205 /// FIXME: As that the number of operands is used to find the start of
206 /// the allocated memory in operator delete, we need to always think we have
207 /// 1 operand before delete.
208 void setGlobalVariableNumOperands(unsigned NumOps) {
209 assert(NumOps <= 1 && "GlobalVariable can only have 0 or 1 operands");
210 NumUserOperands = NumOps;
211 }
212
213 /// Subclasses with hung off uses need to manage the operand count
214 /// themselves. In these instances, the operand count isn't used to find the
215 /// OperandList, so there's no issue in having the operand count change.
216 void setNumHungOffUseOperands(unsigned NumOps) {
217 assert(HasHungOffUses && "Must have hung off uses to use this method");
218 assert(NumOps < (1u << NumUserOperandsBits) && "Too many operands");
219 NumUserOperands = NumOps;
220 }
221
222 // ---------------------------------------------------------------------------
223 // Operand Iterator interface...
224 //
225 using op_iterator = Use*;
226 using const_op_iterator = const Use*;
227 using op_range = iterator_range<op_iterator>;
228 using const_op_range = iterator_range<const_op_iterator>;
229
230 op_iterator op_begin() { return getOperandList(); }
231 const_op_iterator op_begin() const { return getOperandList(); }
232 op_iterator op_end() {
233 return getOperandList() + NumUserOperands;
234 }
235 const_op_iterator op_end() const {
236 return getOperandList() + NumUserOperands;
237 }
238 op_range operands() {
239 return op_range(op_begin(), op_end());
240 }
241 const_op_range operands() const {
242 return const_op_range(op_begin(), op_end());
243 }
244
245 /// Iterator for directly iterating over the operand Values.
246 struct value_op_iterator
247 : iterator_adaptor_base<value_op_iterator, op_iterator,
248 std::random_access_iterator_tag, Value *,
249 ptrdiff_t, Value *, Value *> {
250 explicit value_op_iterator(Use *U = nullptr) : iterator_adaptor_base(U) {}
251
252 Value *operator*() const { return *I; }
253 Value *operator->() const { return operator*(); }
254 };
255
256 value_op_iterator value_op_begin() {
257 return value_op_iterator(op_begin());
258 }
259 value_op_iterator value_op_end() {
260 return value_op_iterator(op_end());
261 }
262 iterator_range<value_op_iterator> operand_values() {
263 return make_range(value_op_begin(), value_op_end());
264 }
265
266 struct const_value_op_iterator
267 : iterator_adaptor_base<const_value_op_iterator, const_op_iterator,
268 std::random_access_iterator_tag, const Value *,
269 ptrdiff_t, const Value *, const Value *> {
270 explicit const_value_op_iterator(const Use *U = nullptr) :
271 iterator_adaptor_base(U) {}
272
273 const Value *operator*() const { return *I; }
274 const Value *operator->() const { return operator*(); }
275 };
276
277 const_value_op_iterator value_op_begin() const {
278 return const_value_op_iterator(op_begin());
279 }
280 const_value_op_iterator value_op_end() const {
281 return const_value_op_iterator(op_end());
282 }
283 iterator_range<const_value_op_iterator> operand_values() const {
284 return make_range(value_op_begin(), value_op_end());
285 }
286
287 /// Drop all references to operands.
288 ///
289 /// This function is in charge of "letting go" of all objects that this User
290 /// refers to. This allows one to 'delete' a whole class at a time, even
291 /// though there may be circular references... First all references are
292 /// dropped, and all use counts go to zero. Then everything is deleted for
293 /// real. Note that no operations are valid on an object that has "dropped
294 /// all references", except operator delete.
295 void dropAllReferences() {
296 for (Use &U : operands())
297 U.set(nullptr);
298 }
299
300 /// Replace uses of one Value with another.
301 ///
302 /// Replaces all references to the "From" definition with references to the
303 /// "To" definition.
304 void replaceUsesOfWith(Value *From, Value *To);
305
306 // Methods for support type inquiry through isa, cast, and dyn_cast:
307 static bool classof(const Value *V) {
308 return isa<Instruction>(V) || isa<Constant>(V);
309 }
310};
311
312// Either Use objects, or a Use pointer can be prepended to User.
313static_assert(alignof(Use) >= alignof(User),
314 "Alignment is insufficient after objects prepended to User");
315static_assert(alignof(Use *) >= alignof(User),
316 "Alignment is insufficient after objects prepended to User");
317
318template<> struct simplify_type<User::op_iterator> {
319 using SimpleType = Value*;
320
321 static SimpleType getSimplifiedValue(User::op_iterator &Val) {
322 return Val->get();
323 }
324};
325template<> struct simplify_type<User::const_op_iterator> {
326 using SimpleType = /*const*/ Value*;
327
328 static SimpleType getSimplifiedValue(User::const_op_iterator &Val) {
329 return Val->get();
330 }
331};
332
333} // end namespace llvm
334
335#endif // LLVM_IR_USER_H
336