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ValueMapper.h
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1 //===- ValueMapper.h - Remapping for constants and metadata -----*- 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 file defines the MapValue interface which is used by various parts of
11 // the Transforms/Utils library to implement cloning and linking facilities.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H
16 #define LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H
17 
18 #include "llvm/ADT/ArrayRef.h"
19 #include "llvm/IR/ValueHandle.h"
20 #include "llvm/IR/ValueMap.h"
21 
22 namespace llvm {
23 
24 class Value;
27 
28 /// This is a class that can be implemented by clients to remap types when
29 /// cloning constants and instructions.
31  virtual void anchor(); // Out of line method.
32 
33 public:
34  virtual ~ValueMapTypeRemapper() = default;
35 
36  /// The client should implement this method if they want to remap types while
37  /// mapping values.
38  virtual Type *remapType(Type *SrcTy) = 0;
39 };
40 
41 /// This is a class that can be implemented by clients to materialize Values on
42 /// demand.
44  virtual void anchor(); // Out of line method.
45 
46 protected:
47  ~ValueMaterializer() = default;
48  ValueMaterializer() = default;
49  ValueMaterializer(const ValueMaterializer &) = default;
50  ValueMaterializer &operator=(const ValueMaterializer &) = default;
51 
52 public:
53  /// This method can be implemented to generate a mapped Value on demand. For
54  /// example, if linking lazily. Returns null if the value is not materialized.
55  virtual Value *materialize(Value *V) = 0;
56 };
57 
58 /// These are flags that the value mapping APIs allow.
59 enum RemapFlags {
60  RF_None = 0,
61 
62  /// If this flag is set, the remapper knows that only local values within a
63  /// function (such as an instruction or argument) are mapped, not global
64  /// values like functions and global metadata.
66 
67  /// If this flag is set, the remapper ignores missing function-local entries
68  /// (Argument, Instruction, BasicBlock) that are not in the value map. If it
69  /// is unset, it aborts if an operand is asked to be remapped which doesn't
70  /// exist in the mapping.
71  ///
72  /// There are no such assertions in MapValue(), whose results are almost
73  /// unchanged by this flag. This flag mainly changes the assertion behaviour
74  /// in RemapInstruction().
75  ///
76  /// Since an Instruction's metadata operands (even that point to SSA values)
77  /// aren't guaranteed to be dominated by their definitions, MapMetadata will
78  /// return "!{}" instead of "null" for \a LocalAsMetadata instances whose SSA
79  /// values are unmapped when this flag is set. Otherwise, \a MapValue()
80  /// completely ignores this flag.
81  ///
82  /// \a MapMetadata() always ignores this flag.
84 
85  /// Instruct the remapper to move distinct metadata instead of duplicating it
86  /// when there are module-level changes.
88 
89  /// Any global values not in value map are mapped to null instead of mapping
90  /// to self. Illegal if RF_IgnoreMissingLocals is also set.
92 };
93 
94 static inline RemapFlags operator|(RemapFlags LHS, RemapFlags RHS) {
95  return RemapFlags(unsigned(LHS) | unsigned(RHS));
96 }
97 
98 /// Context for (re-)mapping values (and metadata).
99 ///
100 /// A shared context used for mapping and remapping of Value and Metadata
101 /// instances using \a ValueToValueMapTy, \a RemapFlags, \a
102 /// ValueMapTypeRemapper, and \a ValueMaterializer.
103 ///
104 /// There are a number of top-level entry points:
105 /// - \a mapValue() (and \a mapConstant());
106 /// - \a mapMetadata() (and \a mapMDNode());
107 /// - \a remapInstruction(); and
108 /// - \a remapFunction().
109 ///
110 /// The \a ValueMaterializer can be used as a callback, but cannot invoke any
111 /// of these top-level functions recursively. Instead, callbacks should use
112 /// one of the following to schedule work lazily in the \a ValueMapper
113 /// instance:
114 /// - \a scheduleMapGlobalInitializer()
115 /// - \a scheduleMapAppendingVariable()
116 /// - \a scheduleMapGlobalAliasee()
117 /// - \a scheduleRemapFunction()
118 ///
119 /// Sometimes a callback needs a different mapping context. Such a context can
120 /// be registered using \a registerAlternateMappingContext(), which takes an
121 /// alternate \a ValueToValueMapTy and \a ValueMaterializer and returns a ID to
122 /// pass into the schedule*() functions.
123 ///
124 /// TODO: lib/Linker really doesn't need the \a ValueHandle in the \a
125 /// ValueToValueMapTy. We should template \a ValueMapper (and its
126 /// implementation classes), and explicitly instantiate on two concrete
127 /// instances of \a ValueMap (one as \a ValueToValueMap, and one with raw \a
128 /// Value pointers). It may be viable to do away with \a TrackingMDRef in the
129 /// \a Metadata side map for the lib/Linker case as well, in which case we'll
130 /// need a new template parameter on \a ValueMap.
131 ///
132 /// TODO: Update callers of \a RemapInstruction() and \a MapValue() (etc.) to
133 /// use \a ValueMapper directly.
134 class ValueMapper {
135  void *pImpl;
136 
137 public:
138  ValueMapper(ValueToValueMapTy &VM, RemapFlags Flags = RF_None,
139  ValueMapTypeRemapper *TypeMapper = nullptr,
140  ValueMaterializer *Materializer = nullptr);
141  ValueMapper(ValueMapper &&) = delete;
142  ValueMapper(const ValueMapper &) = delete;
143  ValueMapper &operator=(ValueMapper &&) = delete;
144  ValueMapper &operator=(const ValueMapper &) = delete;
145  ~ValueMapper();
146 
147  /// Register an alternate mapping context.
148  ///
149  /// Returns a MappingContextID that can be used with the various schedule*()
150  /// API to switch in a different value map on-the-fly.
151  unsigned
152  registerAlternateMappingContext(ValueToValueMapTy &VM,
153  ValueMaterializer *Materializer = nullptr);
154 
155  /// Add to the current \a RemapFlags.
156  ///
157  /// \note Like the top-level mapping functions, \a addFlags() must be called
158  /// at the top level, not during a callback in a \a ValueMaterializer.
159  void addFlags(RemapFlags Flags);
160 
161  Metadata *mapMetadata(const Metadata &MD);
162  MDNode *mapMDNode(const MDNode &N);
163 
164  Value *mapValue(const Value &V);
165  Constant *mapConstant(const Constant &C);
166 
168  void remapFunction(Function &F);
169 
170  void scheduleMapGlobalInitializer(GlobalVariable &GV, Constant &Init,
171  unsigned MappingContextID = 0);
172  void scheduleMapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
173  bool IsOldCtorDtor,
174  ArrayRef<Constant *> NewMembers,
175  unsigned MappingContextID = 0);
176  void scheduleMapGlobalAliasee(GlobalAlias &GA, Constant &Aliasee,
177  unsigned MappingContextID = 0);
178  void scheduleRemapFunction(Function &F, unsigned MappingContextID = 0);
179 };
180 
181 /// Look up or compute a value in the value map.
182 ///
183 /// Return a mapped value for a function-local value (Argument, Instruction,
184 /// BasicBlock), or compute and memoize a value for a Constant.
185 ///
186 /// 1. If \c V is in VM, return the result.
187 /// 2. Else if \c V can be materialized with \c Materializer, do so, memoize
188 /// it in \c VM, and return it.
189 /// 3. Else if \c V is a function-local value, return nullptr.
190 /// 4. Else if \c V is a \a GlobalValue, return \c nullptr or \c V depending
191 /// on \a RF_NullMapMissingGlobalValues.
192 /// 5. Else if \c V is a \a MetadataAsValue wrapping a LocalAsMetadata,
193 /// recurse on the local SSA value, and return nullptr or "metadata !{}" on
194 /// missing depending on RF_IgnoreMissingValues.
195 /// 6. Else if \c V is a \a MetadataAsValue, rewrap the return of \a
196 /// MapMetadata().
197 /// 7. Else, compute the equivalent constant, and return it.
198 inline Value *MapValue(const Value *V, ValueToValueMapTy &VM,
200  ValueMapTypeRemapper *TypeMapper = nullptr,
201  ValueMaterializer *Materializer = nullptr) {
202  return ValueMapper(VM, Flags, TypeMapper, Materializer).mapValue(*V);
203 }
204 
205 /// Lookup or compute a mapping for a piece of metadata.
206 ///
207 /// Compute and memoize a mapping for \c MD.
208 ///
209 /// 1. If \c MD is mapped, return it.
210 /// 2. Else if \a RF_NoModuleLevelChanges or \c MD is an \a MDString, return
211 /// \c MD.
212 /// 3. Else if \c MD is a \a ConstantAsMetadata, call \a MapValue() and
213 /// re-wrap its return (returning nullptr on nullptr).
214 /// 4. Else, \c MD is an \a MDNode. These are remapped, along with their
215 /// transitive operands. Distinct nodes are duplicated or moved depending
216 /// on \a RF_MoveDistinctNodes. Uniqued nodes are remapped like constants.
217 ///
218 /// \note \a LocalAsMetadata is completely unsupported by \a MapMetadata.
219 /// Instead, use \a MapValue() with its wrapping \a MetadataAsValue instance.
220 inline Metadata *MapMetadata(const Metadata *MD, ValueToValueMapTy &VM,
222  ValueMapTypeRemapper *TypeMapper = nullptr,
223  ValueMaterializer *Materializer = nullptr) {
224  return ValueMapper(VM, Flags, TypeMapper, Materializer).mapMetadata(*MD);
225 }
226 
227 /// Version of MapMetadata with type safety for MDNode.
228 inline MDNode *MapMetadata(const MDNode *MD, ValueToValueMapTy &VM,
230  ValueMapTypeRemapper *TypeMapper = nullptr,
231  ValueMaterializer *Materializer = nullptr) {
232  return ValueMapper(VM, Flags, TypeMapper, Materializer).mapMDNode(*MD);
233 }
234 
235 /// Convert the instruction operands from referencing the current values into
236 /// those specified by VM.
237 ///
238 /// If \a RF_IgnoreMissingLocals is set and an operand can't be found via \a
239 /// MapValue(), use the old value. Otherwise assert that this doesn't happen.
240 ///
241 /// Note that \a MapValue() only returns \c nullptr for SSA values missing from
242 /// \c VM.
243 inline void RemapInstruction(Instruction *I, ValueToValueMapTy &VM,
245  ValueMapTypeRemapper *TypeMapper = nullptr,
246  ValueMaterializer *Materializer = nullptr) {
247  ValueMapper(VM, Flags, TypeMapper, Materializer).remapInstruction(*I);
248 }
249 
250 /// Remap the operands, metadata, arguments, and instructions of a function.
251 ///
252 /// Calls \a MapValue() on prefix data, prologue data, and personality
253 /// function; calls \a MapMetadata() on each attached MDNode; remaps the
254 /// argument types using the provided \c TypeMapper; and calls \a
255 /// RemapInstruction() on every instruction.
256 inline void RemapFunction(Function &F, ValueToValueMapTy &VM,
258  ValueMapTypeRemapper *TypeMapper = nullptr,
259  ValueMaterializer *Materializer = nullptr) {
260  ValueMapper(VM, Flags, TypeMapper, Materializer).remapFunction(F);
261 }
262 
263 /// Version of MapValue with type safety for Constant.
264 inline Constant *MapValue(const Constant *V, ValueToValueMapTy &VM,
266  ValueMapTypeRemapper *TypeMapper = nullptr,
267  ValueMaterializer *Materializer = nullptr) {
268  return ValueMapper(VM, Flags, TypeMapper, Materializer).mapConstant(*V);
269 }
270 
271 } // end namespace llvm
272 
273 #endif // LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H
uint64_t CallInst * C
ValueMap< const Value *, WeakTrackingVH > ValueToValueMapTy
Definition: ValueMapper.h:25
static void remapInstruction(Instruction *I, ValueToValueMapTy &VMap)
Convert the instruction operands from referencing the current values into those specified by VMap...
Definition: LoopUnroll.cpp:67
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
void RemapFunction(Function &F, ValueToValueMapTy &VM, RemapFlags Flags=RF_None, ValueMapTypeRemapper *TypeMapper=nullptr, ValueMaterializer *Materializer=nullptr)
Remap the operands, metadata, arguments, and instructions of a function.
Definition: ValueMapper.h:256
Any global values not in value map are mapped to null instead of mapping to self. ...
Definition: ValueMapper.h:91
virtual ~ValueMapTypeRemapper()=default
Metadata node.
Definition: Metadata.h:862
Context for (re-)mapping values (and metadata).
Definition: ValueMapper.h:134
Metadata * MapMetadata(const Metadata *MD, ValueToValueMapTy &VM, RemapFlags Flags=RF_None, ValueMapTypeRemapper *TypeMapper=nullptr, ValueMaterializer *Materializer=nullptr)
Lookup or compute a mapping for a piece of metadata.
Definition: ValueMapper.h:220
void remapInstruction(Instruction &I)
Constant * mapConstant(const Constant &C)
Metadata * mapMetadata(const Metadata &MD)
Instruct the remapper to move distinct metadata instead of duplicating it when there are module-level...
Definition: ValueMapper.h:87
#define F(x, y, z)
Definition: MD5.cpp:55
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory)...
Definition: APInt.h:33
If this flag is set, the remapper knows that only local values within a function (such as an instruct...
Definition: ValueMapper.h:65
This is a class that can be implemented by clients to materialize Values on demand.
Definition: ValueMapper.h:43
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
This is an important base class in LLVM.
Definition: Constant.h:42
RemapFlags
These are flags that the value mapping APIs allow.
Definition: ValueMapper.h:59
Value * MapValue(const Value *V, ValueToValueMapTy &VM, RemapFlags Flags=RF_None, ValueMapTypeRemapper *TypeMapper=nullptr, ValueMaterializer *Materializer=nullptr)
Look up or compute a value in the value map.
Definition: ValueMapper.h:198
const size_t N
void remapFunction(Function &F)
void RemapInstruction(Instruction *I, ValueToValueMapTy &VM, RemapFlags Flags=RF_None, ValueMapTypeRemapper *TypeMapper=nullptr, ValueMaterializer *Materializer=nullptr)
Convert the instruction operands from referencing the current values into those specified by VM...
Definition: ValueMapper.h:243
This is a class that can be implemented by clients to remap types when cloning constants and instruct...
Definition: ValueMapper.h:30
If this flag is set, the remapper ignores missing function-local entries (Argument, Instruction, BasicBlock) that are not in the value map.
Definition: ValueMapper.h:83
static std::vector< std::string > Flags
Definition: FlagsTest.cpp:8
#define I(x, y, z)
Definition: MD5.cpp:58
Value * mapValue(const Value &V)
LLVM Value Representation.
Definition: Value.h:73
virtual Type * remapType(Type *SrcTy)=0
The client should implement this method if they want to remap types while mapping values...
APInt operator|(APInt a, const APInt &b)
Definition: APInt.h:1978
Root of the metadata hierarchy.
Definition: Metadata.h:58
MDNode * mapMDNode(const MDNode &N)