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/// \brief 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  /// \brief 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  /// \brief 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  /// \brief Free memory allocated for User and Use objects.
101  void operator delete(void *Usr);
102  /// \brief Placement delete - required by std, but never called.
103  void operator delete(void*, unsigned) {
104    llvm_unreachable("Constructor throws?");
105  }
106  /// \brief Placement delete - required by std, but never called.
107  void operator delete(void*, unsigned, bool) {
108    llvm_unreachable("Constructor throws?");
109  }
110
111protected:
112  template <int Idx, typename U> static Use &OpFrom(const U *that) {
113    return Idx < 0
114      ? OperandTraits<U>::op_end(const_cast<U*>(that))[Idx]
115      : OperandTraits<U>::op_begin(const_cast<U*>(that))[Idx];
116  }
117
118  template <int Idx> Use &Op() {
119    return OpFrom<Idx>(this);
120  }
121  template <int Idx> const Use &Op() const {
122    return OpFrom<Idx>(this);
123  }
124
125private:
126  const Use *getHungOffOperands() const {
127    return *(reinterpret_cast<const Use *const *>(this) - 1);
128  }
129
130  Use *&getHungOffOperands() { return *(reinterpret_cast<Use **>(this) - 1); }
131
132  const Use *getIntrusiveOperands() const {
133    return reinterpret_cast<const Use *>(this) - NumUserOperands;
134  }
135
136  Use *getIntrusiveOperands() {
137    return reinterpret_cast<Use *>(this) - NumUserOperands;
138  }
139
140  void setOperandList(Use *NewList) {
141    assert(HasHungOffUses &&
142           "Setting operand list only required for hung off uses");
143    getHungOffOperands() = NewList;
144  }
145
146public:
147  const Use *getOperandList() const {
148    return HasHungOffUses ? getHungOffOperands() : getIntrusiveOperands();
149  }
150  Use *getOperandList() {
151    return const_cast<Use *>(static_cast<const User *>(this)->getOperandList());
152  }
153
154  Value *getOperand(unsigned i) const {
155    assert(i < NumUserOperands && "getOperand() out of range!");
156    return getOperandList()[i];
157  }
158
159  void setOperand(unsigned i, Value *Val) {
160    assert(i < NumUserOperands && "setOperand() out of range!");
161    assert((!isa<Constant>((const Value*)this) ||
162            isa<GlobalValue>((const Value*)this)) &&
163           "Cannot mutate a constant with setOperand!");
164    getOperandList()[i] = Val;
165  }
166
167  const Use &getOperandUse(unsigned i) const {
168    assert(i < NumUserOperands && "getOperandUse() out of range!");
169    return getOperandList()[i];
170  }
171  Use &getOperandUse(unsigned i) {
172    assert(i < NumUserOperands && "getOperandUse() out of range!");
173    return getOperandList()[i];
174  }
175
176  unsigned getNumOperands() const { return NumUserOperands; }
177
178  /// Returns the descriptor co-allocated with this User instance.
179  ArrayRef<const uint8_t> getDescriptor() const;
180
181  /// Returns the descriptor co-allocated with this User instance.
182  MutableArrayRef<uint8_t> getDescriptor();
183
184  /// Set the number of operands on a GlobalVariable.
185  ///
186  /// GlobalVariable always allocates space for a single operands, but
187  /// doesn't always use it.
188  ///
189  /// FIXME: As that the number of operands is used to find the start of
190  /// the allocated memory in operator delete, we need to always think we have
191  /// 1 operand before delete.
192  void setGlobalVariableNumOperands(unsigned NumOps) {
193    assert(NumOps <= 1 && "GlobalVariable can only have 0 or 1 operands");
194    NumUserOperands = NumOps;
195  }
196
197  /// \brief Subclasses with hung off uses need to manage the operand count
198  /// themselves.  In these instances, the operand count isn't used to find the
199  /// OperandList, so there's no issue in having the operand count change.
200  void setNumHungOffUseOperands(unsigned NumOps) {
201    assert(HasHungOffUses && "Must have hung off uses to use this method");
202    assert(NumOps < (1u << NumUserOperandsBits) && "Too many operands");
203    NumUserOperands = NumOps;
204  }
205
206  // ---------------------------------------------------------------------------
207  // Operand Iterator interface...
208  //
209  using op_iterator = Use*;
210  using const_op_iterator = const Use*;
211  using op_range = iterator_range<op_iterator>;
212  using const_op_range = iterator_range<const_op_iterator>;
213
214  op_iterator       op_begin()       { return getOperandList(); }
215  const_op_iterator op_begin() const { return getOperandList(); }
216  op_iterator       op_end()         {
217    return getOperandList() + NumUserOperands;
218  }
219  const_op_iterator op_end()   const {
220    return getOperandList() + NumUserOperands;
221  }
222  op_range operands() {
223    return op_range(op_begin(), op_end());
224  }
225  const_op_range operands() const {
226    return const_op_range(op_begin(), op_end());
227  }
228
229  /// \brief Iterator for directly iterating over the operand Values.
230  struct value_op_iterator
231      : iterator_adaptor_base<value_op_iterator, op_iterator,
232                              std::random_access_iterator_tag, Value *,
233                              ptrdiff_t, Value *, Value *> {
234    explicit value_op_iterator(Use *U = nullptr) : iterator_adaptor_base(U) {}
235
236    Value *operator*() const { return *I; }
237    Value *operator->() const { return operator*(); }
238  };
239
240  value_op_iterator value_op_begin() {
241    return value_op_iterator(op_begin());
242  }
243  value_op_iterator value_op_end() {
244    return value_op_iterator(op_end());
245  }
246  iterator_range<value_op_iterator> operand_values() {
247    return make_range(value_op_begin(), value_op_end());
248  }
249
250  struct const_value_op_iterator
251      : iterator_adaptor_base<const_value_op_iterator, const_op_iterator,
252                              std::random_access_iterator_tag, const Value *,
253                              ptrdiff_t, const Value *, const Value *> {
254    explicit const_value_op_iterator(const Use *U = nullptr) :
255      iterator_adaptor_base(U) {}
256
257    const Value *operator*() const { return *I; }
258    const Value *operator->() const { return operator*(); }
259  };
260
261  const_value_op_iterator value_op_begin() const {
262    return const_value_op_iterator(op_begin());
263  }
264  const_value_op_iterator value_op_end() const {
265    return const_value_op_iterator(op_end());
266  }
267  iterator_range<const_value_op_iterator> operand_values() const {
268    return make_range(value_op_begin(), value_op_end());
269  }
270
271  /// \brief Drop all references to operands.
272  ///
273  /// This function is in charge of "letting go" of all objects that this User
274  /// refers to.  This allows one to 'delete' a whole class at a time, even
275  /// though there may be circular references...  First all references are
276  /// dropped, and all use counts go to zero.  Then everything is deleted for
277  /// real.  Note that no operations are valid on an object that has "dropped
278  /// all references", except operator delete.
279  void dropAllReferences() {
280    for (Use &U : operands())
281      U.set(nullptr);
282  }
283
284  /// \brief Replace uses of one Value with another.
285  ///
286  /// Replaces all references to the "From" definition with references to the
287  /// "To" definition.
288  void replaceUsesOfWith(Value *From, Value *To);
289
290  // Methods for support type inquiry through isa, cast, and dyn_cast:
291  static bool classof(const Value *V) {
292    return isa<Instruction>(V) || isa<Constant>(V);
293  }
294};
295
296// Either Use objects, or a Use pointer can be prepended to User.
297static_assert(alignof(Use) >= alignof(User),
298              "Alignment is insufficient after objects prepended to User");
299static_assert(alignof(Use *) >= alignof(User),
300              "Alignment is insufficient after objects prepended to User");
301
302template<> struct simplify_type<User::op_iterator> {
303  using SimpleType = Value*;
304
305  static SimpleType getSimplifiedValue(User::op_iterator &Val) {
306    return Val->get();
307  }
308};
309template<> struct simplify_type<User::const_op_iterator> {
310  using SimpleType = /*const*/ Value*;
311
312  static SimpleType getSimplifiedValue(User::const_op_iterator &Val) {
313    return Val->get();
314  }
315};
316
317} // end namespace llvm
318
319#endif // LLVM_IR_USER_H
320