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 GlobalIndirectSymbol; 26 class GlobalVariable; 27 class Instruction; 28 class MDNode; 29 class Metadata; 30 class Type; 31 class Value; 32 33 using ValueToValueMapTy = ValueMap<const Value *, WeakTrackingVH>; 34 35 /// This is a class that can be implemented by clients to remap types when 36 /// cloning constants and instructions. 37 class ValueMapTypeRemapper { 38 virtual void anchor(); // Out of line method. 39 40 public: 41 virtual ~ValueMapTypeRemapper() = default; 42 43 /// The client should implement this method if they want to remap types while 44 /// mapping values. 45 virtual Type *remapType(Type *SrcTy) = 0; 46 }; 47 48 /// This is a class that can be implemented by clients to materialize Values on 49 /// demand. 50 class ValueMaterializer { 51 virtual void anchor(); // Out of line method. 52 53 protected: 54 ValueMaterializer() = default; 55 ValueMaterializer(const ValueMaterializer &) = default; 56 ValueMaterializer &operator=(const ValueMaterializer &) = default; 57 ~ValueMaterializer() = default; 58 59 public: 60 /// This method can be implemented to generate a mapped Value on demand. For 61 /// example, if linking lazily. Returns null if the value is not materialized. 62 virtual Value *materialize(Value *V) = 0; 63 }; 64 65 /// These are flags that the value mapping APIs allow. 66 enum RemapFlags { 67 RF_None = 0, 68 69 /// If this flag is set, the remapper knows that only local values within a 70 /// function (such as an instruction or argument) are mapped, not global 71 /// values like functions and global metadata. 72 RF_NoModuleLevelChanges = 1, 73 74 /// If this flag is set, the remapper ignores missing function-local entries 75 /// (Argument, Instruction, BasicBlock) that are not in the value map. If it 76 /// is unset, it aborts if an operand is asked to be remapped which doesn't 77 /// exist in the mapping. 78 /// 79 /// There are no such assertions in MapValue(), whose results are almost 80 /// unchanged by this flag. This flag mainly changes the assertion behaviour 81 /// in RemapInstruction(). 82 /// 83 /// Since an Instruction's metadata operands (even that point to SSA values) 84 /// aren't guaranteed to be dominated by their definitions, MapMetadata will 85 /// return "!{}" instead of "null" for \a LocalAsMetadata instances whose SSA 86 /// values are unmapped when this flag is set. Otherwise, \a MapValue() 87 /// completely ignores this flag. 88 /// 89 /// \a MapMetadata() always ignores this flag. 90 RF_IgnoreMissingLocals = 2, 91 92 /// Instruct the remapper to move distinct metadata instead of duplicating it 93 /// when there are module-level changes. 94 RF_MoveDistinctMDs = 4, 95 96 /// Any global values not in value map are mapped to null instead of mapping 97 /// to self. Illegal if RF_IgnoreMissingLocals is also set. 98 RF_NullMapMissingGlobalValues = 8, 99 }; 100 101 inline RemapFlags operator|(RemapFlags LHS, RemapFlags RHS) { 102 return RemapFlags(unsigned(LHS) | unsigned(RHS)); 103 } 104 105 /// Context for (re-)mapping values (and metadata). 106 /// 107 /// A shared context used for mapping and remapping of Value and Metadata 108 /// instances using \a ValueToValueMapTy, \a RemapFlags, \a 109 /// ValueMapTypeRemapper, and \a ValueMaterializer. 110 /// 111 /// There are a number of top-level entry points: 112 /// - \a mapValue() (and \a mapConstant()); 113 /// - \a mapMetadata() (and \a mapMDNode()); 114 /// - \a remapInstruction(); and 115 /// - \a remapFunction(). 116 /// 117 /// The \a ValueMaterializer can be used as a callback, but cannot invoke any 118 /// of these top-level functions recursively. Instead, callbacks should use 119 /// one of the following to schedule work lazily in the \a ValueMapper 120 /// instance: 121 /// - \a scheduleMapGlobalInitializer() 122 /// - \a scheduleMapAppendingVariable() 123 /// - \a scheduleMapGlobalIndirectSymbol() 124 /// - \a scheduleRemapFunction() 125 /// 126 /// Sometimes a callback needs a different mapping context. Such a context can 127 /// be registered using \a registerAlternateMappingContext(), which takes an 128 /// alternate \a ValueToValueMapTy and \a ValueMaterializer and returns a ID to 129 /// pass into the schedule*() functions. 130 /// 131 /// TODO: lib/Linker really doesn't need the \a ValueHandle in the \a 132 /// ValueToValueMapTy. We should template \a ValueMapper (and its 133 /// implementation classes), and explicitly instantiate on two concrete 134 /// instances of \a ValueMap (one as \a ValueToValueMap, and one with raw \a 135 /// Value pointers). It may be viable to do away with \a TrackingMDRef in the 136 /// \a Metadata side map for the lib/Linker case as well, in which case we'll 137 /// need a new template parameter on \a ValueMap. 138 /// 139 /// TODO: Update callers of \a RemapInstruction() and \a MapValue() (etc.) to 140 /// use \a ValueMapper directly. 141 class ValueMapper { 142 void *pImpl; 143 144 public: 145 ValueMapper(ValueToValueMapTy &VM, RemapFlags Flags = RF_None, 146 ValueMapTypeRemapper *TypeMapper = nullptr, 147 ValueMaterializer *Materializer = nullptr); 148 ValueMapper(ValueMapper &&) = delete; 149 ValueMapper(const ValueMapper &) = delete; 150 ValueMapper &operator=(ValueMapper &&) = delete; 151 ValueMapper &operator=(const ValueMapper &) = delete; 152 ~ValueMapper(); 153 154 /// Register an alternate mapping context. 155 /// 156 /// Returns a MappingContextID that can be used with the various schedule*() 157 /// API to switch in a different value map on-the-fly. 158 unsigned 159 registerAlternateMappingContext(ValueToValueMapTy &VM, 160 ValueMaterializer *Materializer = nullptr); 161 162 /// Add to the current \a RemapFlags. 163 /// 164 /// \note Like the top-level mapping functions, \a addFlags() must be called 165 /// at the top level, not during a callback in a \a ValueMaterializer. 166 void addFlags(RemapFlags Flags); 167 168 Metadata *mapMetadata(const Metadata &MD); 169 MDNode *mapMDNode(const MDNode &N); 170 171 Value *mapValue(const Value &V); 172 Constant *mapConstant(const Constant &C); 173 174 void remapInstruction(Instruction &I); 175 void remapFunction(Function &F); 176 177 void scheduleMapGlobalInitializer(GlobalVariable &GV, Constant &Init, 178 unsigned MappingContextID = 0); 179 void scheduleMapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix, 180 bool IsOldCtorDtor, 181 ArrayRef<Constant *> NewMembers, 182 unsigned MappingContextID = 0); 183 void scheduleMapGlobalIndirectSymbol(GlobalIndirectSymbol &GIS, 184 Constant &Target, 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. 228 inline Metadata *MapMetadata(const Metadata *MD, ValueToValueMapTy &VM, 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. 236 inline MDNode *MapMetadata(const MDNode *MD, ValueToValueMapTy &VM, 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. 251 inline void RemapInstruction(Instruction *I, ValueToValueMapTy &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. 264 inline void RemapFunction(Function &F, ValueToValueMapTy &VM, 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. 272 inline Constant *MapValue(const Constant *V, ValueToValueMapTy &VM, 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 282