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