LLVM  6.0.0svn
ValueMapper.h
Go to the documentation of this file.
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 Constant;
25 class Function;
26 class GlobalAlias;
27 class GlobalVariable;
28 class Instruction;
29 class MDNode;
30 class Metadata;
31 class Type;
32 class Value;
33 
35 
36 /// This is a class that can be implemented by clients to remap types when
37 /// cloning constants and instructions.
39  virtual void anchor(); // Out of line method.
40 
41 public:
42  virtual ~ValueMapTypeRemapper() = default;
43 
44  /// The client should implement this method if they want to remap types while
45  /// mapping values.
46  virtual Type *remapType(Type *SrcTy) = 0;
47 };
48 
49 /// This is a class that can be implemented by clients to materialize Values on
50 /// demand.
52  virtual void anchor(); // Out of line method.
53 
54 protected:
55  ValueMaterializer() = default;
56  ValueMaterializer(const ValueMaterializer &) = default;
57  ValueMaterializer &operator=(const ValueMaterializer &) = default;
58  ~ValueMaterializer() = default;
59 
60 public:
61  /// This method can be implemented to generate a mapped Value on demand. For
62  /// example, if linking lazily. Returns null if the value is not materialized.
63  virtual Value *materialize(Value *V) = 0;
64 };
65 
66 /// These are flags that the value mapping APIs allow.
67 enum RemapFlags {
68  RF_None = 0,
69 
70  /// If this flag is set, the remapper knows that only local values within a
71  /// function (such as an instruction or argument) are mapped, not global
72  /// values like functions and global metadata.
74 
75  /// If this flag is set, the remapper ignores missing function-local entries
76  /// (Argument, Instruction, BasicBlock) that are not in the value map. If it
77  /// is unset, it aborts if an operand is asked to be remapped which doesn't
78  /// exist in the mapping.
79  ///
80  /// There are no such assertions in MapValue(), whose results are almost
81  /// unchanged by this flag. This flag mainly changes the assertion behaviour
82  /// in RemapInstruction().
83  ///
84  /// Since an Instruction's metadata operands (even that point to SSA values)
85  /// aren't guaranteed to be dominated by their definitions, MapMetadata will
86  /// return "!{}" instead of "null" for \a LocalAsMetadata instances whose SSA
87  /// values are unmapped when this flag is set. Otherwise, \a MapValue()
88  /// completely ignores this flag.
89  ///
90  /// \a MapMetadata() always ignores this flag.
92 
93  /// Instruct the remapper to move distinct metadata instead of duplicating it
94  /// when there are module-level changes.
96 
97  /// Any global values not in value map are mapped to null instead of mapping
98  /// to self. Illegal if RF_IgnoreMissingLocals is also set.
100 };
101 
103  return RemapFlags(unsigned(LHS) | unsigned(RHS));
104 }
105 
106 /// Context for (re-)mapping values (and metadata).
107 ///
108 /// A shared context used for mapping and remapping of Value and Metadata
109 /// instances using \a ValueToValueMapTy, \a RemapFlags, \a
110 /// ValueMapTypeRemapper, and \a ValueMaterializer.
111 ///
112 /// There are a number of top-level entry points:
113 /// - \a mapValue() (and \a mapConstant());
114 /// - \a mapMetadata() (and \a mapMDNode());
115 /// - \a remapInstruction(); and
116 /// - \a remapFunction().
117 ///
118 /// The \a ValueMaterializer can be used as a callback, but cannot invoke any
119 /// of these top-level functions recursively. Instead, callbacks should use
120 /// one of the following to schedule work lazily in the \a ValueMapper
121 /// instance:
122 /// - \a scheduleMapGlobalInitializer()
123 /// - \a scheduleMapAppendingVariable()
124 /// - \a scheduleMapGlobalAliasee()
125 /// - \a scheduleRemapFunction()
126 ///
127 /// Sometimes a callback needs a different mapping context. Such a context can
128 /// be registered using \a registerAlternateMappingContext(), which takes an
129 /// alternate \a ValueToValueMapTy and \a ValueMaterializer and returns a ID to
130 /// pass into the schedule*() functions.
131 ///
132 /// TODO: lib/Linker really doesn't need the \a ValueHandle in the \a
133 /// ValueToValueMapTy. We should template \a ValueMapper (and its
134 /// implementation classes), and explicitly instantiate on two concrete
135 /// instances of \a ValueMap (one as \a ValueToValueMap, and one with raw \a
136 /// Value pointers). It may be viable to do away with \a TrackingMDRef in the
137 /// \a Metadata side map for the lib/Linker case as well, in which case we'll
138 /// need a new template parameter on \a ValueMap.
139 ///
140 /// TODO: Update callers of \a RemapInstruction() and \a MapValue() (etc.) to
141 /// use \a ValueMapper directly.
142 class ValueMapper {
143  void *pImpl;
144 
145 public:
147  ValueMapTypeRemapper *TypeMapper = nullptr,
148  ValueMaterializer *Materializer = nullptr);
149  ValueMapper(ValueMapper &&) = delete;
150  ValueMapper(const ValueMapper &) = delete;
151  ValueMapper &operator=(ValueMapper &&) = delete;
152  ValueMapper &operator=(const ValueMapper &) = delete;
153  ~ValueMapper();
154 
155  /// Register an alternate mapping context.
156  ///
157  /// Returns a MappingContextID that can be used with the various schedule*()
158  /// API to switch in a different value map on-the-fly.
159  unsigned
160  registerAlternateMappingContext(ValueToValueMapTy &VM,
161  ValueMaterializer *Materializer = nullptr);
162 
163  /// Add to the current \a RemapFlags.
164  ///
165  /// \note Like the top-level mapping functions, \a addFlags() must be called
166  /// at the top level, not during a callback in a \a ValueMaterializer.
167  void addFlags(RemapFlags Flags);
168 
169  Metadata *mapMetadata(const Metadata &MD);
170  MDNode *mapMDNode(const MDNode &N);
171 
172  Value *mapValue(const Value &V);
173  Constant *mapConstant(const Constant &C);
174 
176  void remapFunction(Function &F);
177 
178  void scheduleMapGlobalInitializer(GlobalVariable &GV, Constant &Init,
179  unsigned MappingContextID = 0);
180  void scheduleMapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
181  bool IsOldCtorDtor,
182  ArrayRef<Constant *> NewMembers,
183  unsigned MappingContextID = 0);
184  void scheduleMapGlobalAliasee(GlobalAlias &GA, Constant &Aliasee,
185  unsigned MappingContextID = 0);
186  void scheduleRemapFunction(Function &F, unsigned MappingContextID = 0);
187 };
188 
189 /// Look up or compute a value in the value map.
190 ///
191 /// Return a mapped value for a function-local value (Argument, Instruction,
192 /// BasicBlock), or compute and memoize a value for a Constant.
193 ///
194 /// 1. If \c V is in VM, return the result.
195 /// 2. Else if \c V can be materialized with \c Materializer, do so, memoize
196 /// it in \c VM, and return it.
197 /// 3. Else if \c V is a function-local value, return nullptr.
198 /// 4. Else if \c V is a \a GlobalValue, return \c nullptr or \c V depending
199 /// on \a RF_NullMapMissingGlobalValues.
200 /// 5. Else if \c V is a \a MetadataAsValue wrapping a LocalAsMetadata,
201 /// recurse on the local SSA value, and return nullptr or "metadata !{}" on
202 /// missing depending on RF_IgnoreMissingValues.
203 /// 6. Else if \c V is a \a MetadataAsValue, rewrap the return of \a
204 /// MapMetadata().
205 /// 7. Else, compute the equivalent constant, and return it.
206 inline Value *MapValue(const Value *V, ValueToValueMapTy &VM,
207  RemapFlags Flags = RF_None,
208  ValueMapTypeRemapper *TypeMapper = nullptr,
209  ValueMaterializer *Materializer = nullptr) {
210  return ValueMapper(VM, Flags, TypeMapper, Materializer).mapValue(*V);
211 }
212 
213 /// Lookup or compute a mapping for a piece of metadata.
214 ///
215 /// Compute and memoize a mapping for \c MD.
216 ///
217 /// 1. If \c MD is mapped, return it.
218 /// 2. Else if \a RF_NoModuleLevelChanges or \c MD is an \a MDString, return
219 /// \c MD.
220 /// 3. Else if \c MD is a \a ConstantAsMetadata, call \a MapValue() and
221 /// re-wrap its return (returning nullptr on nullptr).
222 /// 4. Else, \c MD is an \a MDNode. These are remapped, along with their
223 /// transitive operands. Distinct nodes are duplicated or moved depending
224 /// on \a RF_MoveDistinctNodes. Uniqued nodes are remapped like constants.
225 ///
226 /// \note \a LocalAsMetadata is completely unsupported by \a MapMetadata.
227 /// Instead, use \a MapValue() with its wrapping \a MetadataAsValue instance.
229  RemapFlags Flags = RF_None,
230  ValueMapTypeRemapper *TypeMapper = nullptr,
231  ValueMaterializer *Materializer = nullptr) {
232  return ValueMapper(VM, Flags, TypeMapper, Materializer).mapMetadata(*MD);
233 }
234 
235 /// Version of MapMetadata with type safety for MDNode.
237  RemapFlags Flags = RF_None,
238  ValueMapTypeRemapper *TypeMapper = nullptr,
239  ValueMaterializer *Materializer = nullptr) {
240  return ValueMapper(VM, Flags, TypeMapper, Materializer).mapMDNode(*MD);
241 }
242 
243 /// Convert the instruction operands from referencing the current values into
244 /// those specified by VM.
245 ///
246 /// If \a RF_IgnoreMissingLocals is set and an operand can't be found via \a
247 /// MapValue(), use the old value. Otherwise assert that this doesn't happen.
248 ///
249 /// Note that \a MapValue() only returns \c nullptr for SSA values missing from
250 /// \c VM.
252  RemapFlags Flags = RF_None,
253  ValueMapTypeRemapper *TypeMapper = nullptr,
254  ValueMaterializer *Materializer = nullptr) {
255  ValueMapper(VM, Flags, TypeMapper, Materializer).remapInstruction(*I);
256 }
257 
258 /// Remap the operands, metadata, arguments, and instructions of a function.
259 ///
260 /// Calls \a MapValue() on prefix data, prologue data, and personality
261 /// function; calls \a MapMetadata() on each attached MDNode; remaps the
262 /// argument types using the provided \c TypeMapper; and calls \a
263 /// RemapInstruction() on every instruction.
265  RemapFlags Flags = RF_None,
266  ValueMapTypeRemapper *TypeMapper = nullptr,
267  ValueMaterializer *Materializer = nullptr) {
268  ValueMapper(VM, Flags, TypeMapper, Materializer).remapFunction(F);
269 }
270 
271 /// Version of MapValue with type safety for Constant.
273  RemapFlags Flags = RF_None,
274  ValueMapTypeRemapper *TypeMapper = nullptr,
275  ValueMaterializer *Materializer = nullptr) {
276  return ValueMapper(VM, Flags, TypeMapper, Materializer).mapConstant(*V);
277 }
278 
279 } // end namespace llvm
280 
281 #endif // LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H
uint64_t CallInst * C
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:264
Any global values not in value map are mapped to null instead of mapping to self. ...
Definition: ValueMapper.h:99
virtual ~ValueMapTypeRemapper()=default
Metadata node.
Definition: Metadata.h:862
F(f)
Context for (re-)mapping values (and metadata).
Definition: ValueMapper.h:142
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:228
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:95
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:73
This is a class that can be implemented by clients to materialize Values on demand.
Definition: ValueMapper.h:51
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:67
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:206
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:251
This is a class that can be implemented by clients to remap types when cloning constants and instruct...
Definition: ValueMapper.h:38
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:91
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
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
std::vector< uint32_t > Metadata
PAL metadata represented as a vector.
MDNode * mapMDNode(const MDNode &N)