1//===- ValueMapper.h - Remapping for constants and metadata -----*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines the MapValue interface which is used by various parts of
10// the Transforms/Utils library to implement cloning and linking facilities.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H
15#define LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H
16
17#include "llvm/ADT/ArrayRef.h"
18#include "llvm/ADT/simple_ilist.h"
19#include "llvm/IR/ValueHandle.h"
20#include "llvm/IR/ValueMap.h"
21
22namespace llvm {
23
24class Constant;
25class DIBuilder;
26class DbgRecord;
27class Function;
28class GlobalVariable;
29class Instruction;
30class MDNode;
31class Metadata;
32class Module;
33class Type;
34class Value;
35
36using ValueToValueMapTy = ValueMap<const Value *, WeakTrackingVH>;
37using DbgRecordIterator = simple_ilist<DbgRecord>::iterator;
38
39/// This is a class that can be implemented by clients to remap types when
40/// cloning constants and instructions.
41class ValueMapTypeRemapper {
42 virtual void anchor(); // Out of line method.
43
44public:
45 virtual ~ValueMapTypeRemapper() = default;
46
47 /// The client should implement this method if they want to remap types while
48 /// mapping values.
49 virtual Type *remapType(Type *SrcTy) = 0;
50};
51
52/// This is a class that can be implemented by clients to materialize Values on
53/// demand.
54class ValueMaterializer {
55 virtual void anchor(); // Out of line method.
56
57protected:
58 ValueMaterializer() = default;
59 ValueMaterializer(const ValueMaterializer &) = default;
60 ValueMaterializer &operator=(const ValueMaterializer &) = default;
61 ~ValueMaterializer() = default;
62
63public:
64 /// This method can be implemented to generate a mapped Value on demand. For
65 /// example, if linking lazily. Returns null if the value is not materialized.
66 virtual Value *materialize(Value *V) = 0;
67};
68
69/// These are flags that the value mapping APIs allow.
70enum RemapFlags {
71 RF_None = 0,
72
73 /// If this flag is set, the remapper knows that only local values within a
74 /// function (such as an instruction or argument) are mapped, not global
75 /// values like functions and global metadata.
76 RF_NoModuleLevelChanges = 1,
77
78 /// If this flag is set, the remapper ignores missing function-local entries
79 /// (Argument, Instruction, BasicBlock) that are not in the value map. If it
80 /// is unset, it aborts if an operand is asked to be remapped which doesn't
81 /// exist in the mapping.
82 ///
83 /// There are no such assertions in MapValue(), whose results are almost
84 /// unchanged by this flag. This flag mainly changes the assertion behaviour
85 /// in RemapInstruction().
86 ///
87 /// Since an Instruction's metadata operands (even that point to SSA values)
88 /// aren't guaranteed to be dominated by their definitions, MapMetadata will
89 /// return "!{}" instead of "null" for \a LocalAsMetadata instances whose SSA
90 /// values are unmapped when this flag is set. Otherwise, \a MapValue()
91 /// completely ignores this flag.
92 ///
93 /// \a MapMetadata() always ignores this flag.
94 RF_IgnoreMissingLocals = 2,
95
96 /// Instruct the remapper to reuse and mutate distinct metadata (remapping
97 /// them in place) instead of cloning remapped copies. This flag has no
98 /// effect when RF_NoModuleLevelChanges, since that implies an identity
99 /// mapping.
100 RF_ReuseAndMutateDistinctMDs = 4,
101
102 /// Any global values not in value map are mapped to null instead of mapping
103 /// to self. Illegal if RF_IgnoreMissingLocals is also set.
104 RF_NullMapMissingGlobalValues = 8,
105};
106
107inline RemapFlags operator|(RemapFlags LHS, RemapFlags RHS) {
108 return RemapFlags(unsigned(LHS) | unsigned(RHS));
109}
110
111/// Context for (re-)mapping values (and metadata).
112///
113/// A shared context used for mapping and remapping of Value and Metadata
114/// instances using \a ValueToValueMapTy, \a RemapFlags, \a
115/// ValueMapTypeRemapper, and \a ValueMaterializer.
116///
117/// There are a number of top-level entry points:
118/// - \a mapValue() (and \a mapConstant());
119/// - \a mapMetadata() (and \a mapMDNode());
120/// - \a remapInstruction();
121/// - \a remapFunction(); and
122/// - \a remapGlobalObjectMetadata().
123///
124/// The \a ValueMaterializer can be used as a callback, but cannot invoke any
125/// of these top-level functions recursively. Instead, callbacks should use
126/// one of the following to schedule work lazily in the \a ValueMapper
127/// instance:
128/// - \a scheduleMapGlobalInitializer()
129/// - \a scheduleMapAppendingVariable()
130/// - \a scheduleMapGlobalAlias()
131/// - \a scheduleMapGlobalIFunc()
132/// - \a scheduleRemapFunction()
133///
134/// Sometimes a callback needs a different mapping context. Such a context can
135/// be registered using \a registerAlternateMappingContext(), which takes an
136/// alternate \a ValueToValueMapTy and \a ValueMaterializer and returns a ID to
137/// pass into the schedule*() functions.
138///
139/// TODO: lib/Linker really doesn't need the \a ValueHandle in the \a
140/// ValueToValueMapTy. We should template \a ValueMapper (and its
141/// implementation classes), and explicitly instantiate on two concrete
142/// instances of \a ValueMap (one as \a ValueToValueMap, and one with raw \a
143/// Value pointers). It may be viable to do away with \a TrackingMDRef in the
144/// \a Metadata side map for the lib/Linker case as well, in which case we'll
145/// need a new template parameter on \a ValueMap.
146///
147/// TODO: Update callers of \a RemapInstruction() and \a MapValue() (etc.) to
148/// use \a ValueMapper directly.
149class ValueMapper {
150 void *pImpl;
151
152public:
153 ValueMapper(ValueToValueMapTy &VM, RemapFlags Flags = RF_None,
154 ValueMapTypeRemapper *TypeMapper = nullptr,
155 ValueMaterializer *Materializer = nullptr);
156 ValueMapper(ValueMapper &&) = delete;
157 ValueMapper(const ValueMapper &) = delete;
158 ValueMapper &operator=(ValueMapper &&) = delete;
159 ValueMapper &operator=(const ValueMapper &) = delete;
160 ~ValueMapper();
161
162 /// Register an alternate mapping context.
163 ///
164 /// Returns a MappingContextID that can be used with the various schedule*()
165 /// API to switch in a different value map on-the-fly.
166 unsigned
167 registerAlternateMappingContext(ValueToValueMapTy &VM,
168 ValueMaterializer *Materializer = nullptr);
169
170 /// Add to the current \a RemapFlags.
171 ///
172 /// \note Like the top-level mapping functions, \a addFlags() must be called
173 /// at the top level, not during a callback in a \a ValueMaterializer.
174 void addFlags(RemapFlags Flags);
175
176 Metadata *mapMetadata(const Metadata &MD);
177 MDNode *mapMDNode(const MDNode &N);
178
179 Value *mapValue(const Value &V);
180 Constant *mapConstant(const Constant &C);
181
182 void remapInstruction(Instruction &I);
183 void remapDbgVariableRecord(Module *M, DbgVariableRecord &V);
184 void remapDbgVariableRecordRange(Module *M,
185 iterator_range<DbgRecordIterator> Range);
186 void remapFunction(Function &F);
187 void remapGlobalObjectMetadata(GlobalObject &GO);
188
189 void scheduleMapGlobalInitializer(GlobalVariable &GV, Constant &Init,
190 unsigned MappingContextID = 0);
191 void scheduleMapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
192 bool IsOldCtorDtor,
193 ArrayRef<Constant *> NewMembers,
194 unsigned MappingContextID = 0);
195 void scheduleMapGlobalAlias(GlobalAlias &GA, Constant &Aliasee,
196 unsigned MappingContextID = 0);
197 void scheduleMapGlobalIFunc(GlobalIFunc &GI, Constant &Resolver,
198 unsigned MappingContextID = 0);
199 void scheduleRemapFunction(Function &F, unsigned MappingContextID = 0);
200};
201
202/// Look up or compute a value in the value map.
203///
204/// Return a mapped value for a function-local value (Argument, Instruction,
205/// BasicBlock), or compute and memoize a value for a Constant.
206///
207/// 1. If \c V is in VM, return the result.
208/// 2. Else if \c V can be materialized with \c Materializer, do so, memoize
209/// it in \c VM, and return it.
210/// 3. Else if \c V is a function-local value, return nullptr.
211/// 4. Else if \c V is a \a GlobalValue, return \c nullptr or \c V depending
212/// on \a RF_NullMapMissingGlobalValues.
213/// 5. Else if \c V is a \a MetadataAsValue wrapping a LocalAsMetadata,
214/// recurse on the local SSA value, and return nullptr or "metadata !{}" on
215/// missing depending on RF_IgnoreMissingValues.
216/// 6. Else if \c V is a \a MetadataAsValue, rewrap the return of \a
217/// MapMetadata().
218/// 7. Else, compute the equivalent constant, and return it.
219inline Value *MapValue(const Value *V, ValueToValueMapTy &VM,
220 RemapFlags Flags = RF_None,
221 ValueMapTypeRemapper *TypeMapper = nullptr,
222 ValueMaterializer *Materializer = nullptr) {
223 return ValueMapper(VM, Flags, TypeMapper, Materializer).mapValue(V: *V);
224}
225
226/// Lookup or compute a mapping for a piece of metadata.
227///
228/// Compute and memoize a mapping for \c MD.
229///
230/// 1. If \c MD is mapped, return it.
231/// 2. Else if \a RF_NoModuleLevelChanges or \c MD is an \a MDString, return
232/// \c MD.
233/// 3. Else if \c MD is a \a ConstantAsMetadata, call \a MapValue() and
234/// re-wrap its return (returning nullptr on nullptr).
235/// 4. Else, \c MD is an \a MDNode. These are remapped, along with their
236/// transitive operands. Distinct nodes are duplicated or moved depending
237/// on \a RF_MoveDistinctNodes. Uniqued nodes are remapped like constants.
238///
239/// \note \a LocalAsMetadata is completely unsupported by \a MapMetadata.
240/// Instead, use \a MapValue() with its wrapping \a MetadataAsValue instance.
241inline Metadata *MapMetadata(const Metadata *MD, ValueToValueMapTy &VM,
242 RemapFlags Flags = RF_None,
243 ValueMapTypeRemapper *TypeMapper = nullptr,
244 ValueMaterializer *Materializer = nullptr) {
245 return ValueMapper(VM, Flags, TypeMapper, Materializer).mapMetadata(MD: *MD);
246}
247
248/// Version of MapMetadata with type safety for MDNode.
249inline MDNode *MapMetadata(const MDNode *MD, ValueToValueMapTy &VM,
250 RemapFlags Flags = RF_None,
251 ValueMapTypeRemapper *TypeMapper = nullptr,
252 ValueMaterializer *Materializer = nullptr) {
253 return ValueMapper(VM, Flags, TypeMapper, Materializer).mapMDNode(N: *MD);
254}
255
256/// Convert the instruction operands from referencing the current values into
257/// those specified by VM.
258///
259/// If \a RF_IgnoreMissingLocals is set and an operand can't be found via \a
260/// MapValue(), use the old value. Otherwise assert that this doesn't happen.
261///
262/// Note that \a MapValue() only returns \c nullptr for SSA values missing from
263/// \c VM.
264inline void RemapInstruction(Instruction *I, ValueToValueMapTy &VM,
265 RemapFlags Flags = RF_None,
266 ValueMapTypeRemapper *TypeMapper = nullptr,
267 ValueMaterializer *Materializer = nullptr) {
268 ValueMapper(VM, Flags, TypeMapper, Materializer).remapInstruction(I&: *I);
269}
270
271/// Remap the Values used in the DbgVariableRecord \a V using the value map \a
272/// VM.
273inline void RemapDbgVariableRecord(Module *M, DbgVariableRecord *V,
274 ValueToValueMapTy &VM,
275 RemapFlags Flags = RF_None,
276 ValueMapTypeRemapper *TypeMapper = nullptr,
277 ValueMaterializer *Materializer = nullptr) {
278 ValueMapper(VM, Flags, TypeMapper, Materializer)
279 .remapDbgVariableRecord(M, V&: *V);
280}
281
282/// Remap the Values used in the DbgVariableRecord \a V using the value map \a
283/// VM.
284inline void
285RemapDbgVariableRecordRange(Module *M, iterator_range<DbgRecordIterator> Range,
286 ValueToValueMapTy &VM, RemapFlags Flags = RF_None,
287 ValueMapTypeRemapper *TypeMapper = nullptr,
288 ValueMaterializer *Materializer = nullptr) {
289 ValueMapper(VM, Flags, TypeMapper, Materializer)
290 .remapDbgVariableRecordRange(M, Range);
291}
292
293/// Remap the operands, metadata, arguments, and instructions of a function.
294///
295/// Calls \a MapValue() on prefix data, prologue data, and personality
296/// function; calls \a MapMetadata() on each attached MDNode; remaps the
297/// argument types using the provided \c TypeMapper; and calls \a
298/// RemapInstruction() on every instruction.
299inline void RemapFunction(Function &F, ValueToValueMapTy &VM,
300 RemapFlags Flags = RF_None,
301 ValueMapTypeRemapper *TypeMapper = nullptr,
302 ValueMaterializer *Materializer = nullptr) {
303 ValueMapper(VM, Flags, TypeMapper, Materializer).remapFunction(F);
304}
305
306/// Version of MapValue with type safety for Constant.
307inline Constant *MapValue(const Constant *V, ValueToValueMapTy &VM,
308 RemapFlags Flags = RF_None,
309 ValueMapTypeRemapper *TypeMapper = nullptr,
310 ValueMaterializer *Materializer = nullptr) {
311 return ValueMapper(VM, Flags, TypeMapper, Materializer).mapConstant(C: *V);
312}
313
314} // end namespace llvm
315
316#endif // LLVM_TRANSFORMS_UTILS_VALUEMAPPER_H
317

source code of llvm/include/llvm/Transforms/Utils/ValueMapper.h