1 //===- Cloning.h - Clone various parts of LLVM programs ---------*- 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 various functions that are used to clone chunks of LLVM 10 // code for various purposes. This varies from copying whole modules into new 11 // modules, to cloning functions with different arguments, to inlining 12 // functions, to copying basic blocks to support loop unrolling or superblock 13 // formation, etc. 14 // 15 //===----------------------------------------------------------------------===// 16 17 #ifndef LLVM_TRANSFORMS_UTILS_CLONING_H 18 #define LLVM_TRANSFORMS_UTILS_CLONING_H 19 20 #include "llvm/ADT/SmallVector.h" 21 #include "llvm/ADT/Twine.h" 22 #include "llvm/Analysis/AssumptionCache.h" 23 #include "llvm/Analysis/InlineCost.h" 24 #include "llvm/IR/BasicBlock.h" 25 #include "llvm/IR/ValueHandle.h" 26 #include "llvm/Transforms/Utils/ValueMapper.h" 27 #include <functional> 28 #include <memory> 29 #include <vector> 30 31 namespace llvm { 32 33 class AAResults; 34 class AllocaInst; 35 class BasicBlock; 36 class BlockFrequencyInfo; 37 class DebugInfoFinder; 38 class DominatorTree; 39 class Function; 40 class Instruction; 41 class Loop; 42 class LoopInfo; 43 class Module; 44 class PGOContextualProfile; 45 class ProfileSummaryInfo; 46 class ReturnInst; 47 class DomTreeUpdater; 48 49 /// Return an exact copy of the specified module 50 std::unique_ptr<Module> CloneModule(const Module &M); 51 std::unique_ptr<Module> CloneModule(const Module &M, ValueToValueMapTy &VMap); 52 53 /// Return a copy of the specified module. The ShouldCloneDefinition function 54 /// controls whether a specific GlobalValue's definition is cloned. If the 55 /// function returns false, the module copy will contain an external reference 56 /// in place of the global definition. 57 std::unique_ptr<Module> 58 CloneModule(const Module &M, ValueToValueMapTy &VMap, 59 function_ref<bool(const GlobalValue *)> ShouldCloneDefinition); 60 61 /// This struct can be used to capture information about code 62 /// being cloned, while it is being cloned. 63 struct ClonedCodeInfo { 64 /// This is set to true if the cloned code contains a normal call instruction. 65 bool ContainsCalls = false; 66 67 /// This is set to true if there is memprof related metadata (memprof or 68 /// callsite metadata) in the cloned code. 69 bool ContainsMemProfMetadata = false; 70 71 /// This is set to true if the cloned code contains a 'dynamic' alloca. 72 /// Dynamic allocas are allocas that are either not in the entry block or they 73 /// are in the entry block but are not a constant size. 74 bool ContainsDynamicAllocas = false; 75 76 /// All cloned call sites that have operand bundles attached are appended to 77 /// this vector. This vector may contain nulls or undefs if some of the 78 /// originally inserted callsites were DCE'ed after they were cloned. 79 std::vector<WeakTrackingVH> OperandBundleCallSites; 80 81 /// Like VMap, but maps only unsimplified instructions. Values in the map 82 /// may be dangling, it is only intended to be used via isSimplified(), to 83 /// check whether the main VMap mapping involves simplification or not. 84 DenseMap<const Value *, const Value *> OrigVMap; 85 86 ClonedCodeInfo() = default; 87 88 bool isSimplified(const Value *From, const Value *To) const { 89 return OrigVMap.lookup(From) != To; 90 } 91 }; 92 93 /// Return a copy of the specified basic block, but without 94 /// embedding the block into a particular function. The block returned is an 95 /// exact copy of the specified basic block, without any remapping having been 96 /// performed. Because of this, this is only suitable for applications where 97 /// the basic block will be inserted into the same function that it was cloned 98 /// from (loop unrolling would use this, for example). 99 /// 100 /// Also, note that this function makes a direct copy of the basic block, and 101 /// can thus produce illegal LLVM code. In particular, it will copy any PHI 102 /// nodes from the original block, even though there are no predecessors for the 103 /// newly cloned block (thus, phi nodes will have to be updated). Also, this 104 /// block will branch to the old successors of the original block: these 105 /// successors will have to have any PHI nodes updated to account for the new 106 /// incoming edges. 107 /// 108 /// The correlation between instructions in the source and result basic blocks 109 /// is recorded in the VMap map. 110 /// 111 /// If you have a particular suffix you'd like to use to add to any cloned 112 /// names, specify it as the optional third parameter. 113 /// 114 /// If you would like the basic block to be auto-inserted into the end of a 115 /// function, you can specify it as the optional fourth parameter. 116 /// 117 /// If you would like to collect additional information about the cloned 118 /// function, you can specify a ClonedCodeInfo object with the optional fifth 119 /// parameter. 120 BasicBlock *CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap, 121 const Twine &NameSuffix = "", Function *F = nullptr, 122 ClonedCodeInfo *CodeInfo = nullptr); 123 124 /// Return a copy of the specified function and add it to that 125 /// function's module. Also, any references specified in the VMap are changed 126 /// to refer to their mapped value instead of the original one. If any of the 127 /// arguments to the function are in the VMap, the arguments are deleted from 128 /// the resultant function. The VMap is updated to include mappings from all of 129 /// the instructions and basicblocks in the function from their old to new 130 /// values. The final argument captures information about the cloned code if 131 /// non-null. 132 /// 133 /// \pre VMap contains no non-identity GlobalValue mappings. 134 /// 135 Function *CloneFunction(Function *F, ValueToValueMapTy &VMap, 136 ClonedCodeInfo *CodeInfo = nullptr); 137 138 enum class CloneFunctionChangeType { 139 LocalChangesOnly, 140 GlobalChanges, 141 DifferentModule, 142 ClonedModule, 143 }; 144 145 /// Clone OldFunc into NewFunc, transforming the old arguments into references 146 /// to VMap values. Note that if NewFunc already has basic blocks, the ones 147 /// cloned into it will be added to the end of the function. This function 148 /// fills in a list of return instructions, and can optionally remap types 149 /// and/or append the specified suffix to all values cloned. 150 /// 151 /// If \p Changes is \a CloneFunctionChangeType::LocalChangesOnly, VMap is 152 /// required to contain no non-identity GlobalValue mappings. Otherwise, 153 /// referenced metadata will be cloned. 154 /// 155 /// If \p Changes is less than \a CloneFunctionChangeType::DifferentModule 156 /// indicating cloning into the same module (even if it's LocalChangesOnly), if 157 /// debug info metadata transitively references a \a DISubprogram, it will be 158 /// cloned, effectively upgrading \p Changes to GlobalChanges while suppressing 159 /// cloning of types and compile units. 160 /// 161 /// If \p Changes is \a CloneFunctionChangeType::DifferentModule, the new 162 /// module's \c !llvm.dbg.cu will get updated with any newly created compile 163 /// units. (\a CloneFunctionChangeType::ClonedModule leaves that work for the 164 /// caller.) 165 /// 166 /// FIXME: Consider simplifying this function by splitting out \a 167 /// CloneFunctionMetadataInto() and expecting / updating callers to call it 168 /// first when / how it's needed. 169 void CloneFunctionInto(Function *NewFunc, const Function *OldFunc, 170 ValueToValueMapTy &VMap, CloneFunctionChangeType Changes, 171 SmallVectorImpl<ReturnInst *> &Returns, 172 const char *NameSuffix = "", 173 ClonedCodeInfo *CodeInfo = nullptr, 174 ValueMapTypeRemapper *TypeMapper = nullptr, 175 ValueMaterializer *Materializer = nullptr); 176 177 /// Clone OldFunc's attributes into NewFunc, transforming values based on the 178 /// mappings in VMap. 179 void CloneFunctionAttributesInto(Function *NewFunc, const Function *OldFunc, 180 ValueToValueMapTy &VMap, 181 bool ModuleLevelChanges, 182 ValueMapTypeRemapper *TypeMapper = nullptr, 183 ValueMaterializer *Materializer = nullptr); 184 185 /// Clone OldFunc's metadata into NewFunc. 186 /// 187 /// The caller is expected to populate \p VMap beforehand and set an appropriate 188 /// \p RemapFlag. Subprograms/CUs/types that were already mapped to themselves 189 /// won't be duplicated. 190 /// 191 /// NOTE: This function doesn't clone !llvm.dbg.cu when cloning into a different 192 /// module. Use CloneFunctionInto for that behavior. 193 void CloneFunctionMetadataInto(Function &NewFunc, const Function &OldFunc, 194 ValueToValueMapTy &VMap, RemapFlags RemapFlag, 195 ValueMapTypeRemapper *TypeMapper = nullptr, 196 ValueMaterializer *Materializer = nullptr, 197 const MetadataSetTy *IdentityMD = nullptr); 198 199 /// Clone OldFunc's body into NewFunc. 200 void CloneFunctionBodyInto(Function &NewFunc, const Function &OldFunc, 201 ValueToValueMapTy &VMap, RemapFlags RemapFlag, 202 SmallVectorImpl<ReturnInst *> &Returns, 203 const char *NameSuffix = "", 204 ClonedCodeInfo *CodeInfo = nullptr, 205 ValueMapTypeRemapper *TypeMapper = nullptr, 206 ValueMaterializer *Materializer = nullptr, 207 const MetadataSetTy *IdentityMD = nullptr); 208 209 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc, 210 const Instruction *StartingInst, 211 ValueToValueMapTy &VMap, bool ModuleLevelChanges, 212 SmallVectorImpl<ReturnInst *> &Returns, 213 const char *NameSuffix = "", 214 ClonedCodeInfo *CodeInfo = nullptr); 215 216 /// This works exactly like CloneFunctionInto, 217 /// except that it does some simple constant prop and DCE on the fly. The 218 /// effect of this is to copy significantly less code in cases where (for 219 /// example) a function call with constant arguments is inlined, and those 220 /// constant arguments cause a significant amount of code in the callee to be 221 /// dead. Since this doesn't produce an exactly copy of the input, it can't be 222 /// used for things like CloneFunction or CloneModule. 223 /// 224 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue 225 /// mappings. 226 /// 227 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 228 ValueToValueMapTy &VMap, bool ModuleLevelChanges, 229 SmallVectorImpl<ReturnInst*> &Returns, 230 const char *NameSuffix = "", 231 ClonedCodeInfo *CodeInfo = nullptr); 232 233 /// Collect debug information such as types, compile units, and other 234 /// subprograms that are reachable from \p F and can be considered global for 235 /// the purposes of cloning (and hence not needing to be cloned). 236 /// 237 /// What debug information should be processed depends on \p Changes: when 238 /// cloning into the same module we process \p F's subprogram and instructions; 239 /// when into a cloned module, neither of those. 240 /// 241 /// Returns DISubprogram of the cloned function when cloning into the same 242 /// module or nullptr otherwise. 243 DISubprogram *CollectDebugInfoForCloning(const Function &F, 244 CloneFunctionChangeType Changes, 245 DebugInfoFinder &DIFinder); 246 247 /// Based on \p Changes and \p DIFinder return debug info that needs to be 248 /// identity mapped during Metadata cloning. 249 /// 250 /// NOTE: Such \a MetadataSetTy can be used by \a CloneFunction* to directly 251 /// specify metadata that should be identity mapped (and hence not cloned). The 252 /// metadata will be identity mapped in \a ValueToValueMapTy on first use. There 253 /// are several reasons for doing it this way rather than eagerly identity 254 /// mapping metadata nodes in a \a ValueMap: 255 /// 1. Mapping metadata is not cheap, particularly because of tracking. 256 /// 2. When cloning a Function we identity map lots of global module-level 257 /// metadata to avoid cloning it, while only a fraction of it is actually 258 /// used by the function. Mapping on first use is a lot faster for modules 259 /// with meaningful amount of debug info. 260 /// 3. Eagerly identity mapping metadata makes it harder to cache module-level 261 /// data (e.g. a set of metadata nodes in a \a DICompileUnit). 262 MetadataSetTy FindDebugInfoToIdentityMap(CloneFunctionChangeType Changes, 263 DebugInfoFinder &DIFinder, 264 DISubprogram *SPClonedWithinModule); 265 266 /// This class captures the data input to the InlineFunction call, and records 267 /// the auxiliary results produced by it. 268 class InlineFunctionInfo { 269 public: 270 explicit InlineFunctionInfo( 271 function_ref<AssumptionCache &(Function &)> GetAssumptionCache = nullptr, 272 ProfileSummaryInfo *PSI = nullptr, 273 BlockFrequencyInfo *CallerBFI = nullptr, 274 BlockFrequencyInfo *CalleeBFI = nullptr, bool UpdateProfile = true) 275 : GetAssumptionCache(GetAssumptionCache), PSI(PSI), CallerBFI(CallerBFI), 276 CalleeBFI(CalleeBFI), UpdateProfile(UpdateProfile) {} 277 278 /// If non-null, InlineFunction will update the callgraph to reflect the 279 /// changes it makes. 280 function_ref<AssumptionCache &(Function &)> GetAssumptionCache; 281 ProfileSummaryInfo *PSI; 282 BlockFrequencyInfo *CallerBFI, *CalleeBFI; 283 284 /// InlineFunction fills this in with all static allocas that get copied into 285 /// the caller. 286 SmallVector<AllocaInst *, 4> StaticAllocas; 287 288 /// InlineFunction fills this in with callsites that were inlined from the 289 /// callee. This is only filled in if CG is non-null. 290 SmallVector<WeakTrackingVH, 8> InlinedCalls; 291 292 /// All of the new call sites inlined into the caller. 293 /// 294 /// 'InlineFunction' fills this in by scanning the inlined instructions, and 295 /// only if CG is null. If CG is non-null, instead the value handle 296 /// `InlinedCalls` above is used. 297 SmallVector<CallBase *, 8> InlinedCallSites; 298 299 /// Update profile for callee as well as cloned version. We need to do this 300 /// for regular inlining, but not for inlining from sample profile loader. 301 bool UpdateProfile; 302 303 void reset() { 304 StaticAllocas.clear(); 305 InlinedCalls.clear(); 306 InlinedCallSites.clear(); 307 } 308 }; 309 310 /// This function inlines the called function into the basic 311 /// block of the caller. This returns false if it is not possible to inline 312 /// this call. The program is still in a well defined state if this occurs 313 /// though. 314 /// 315 /// Note that this only does one level of inlining. For example, if the 316 /// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 317 /// exists in the instruction stream. Similarly this will inline a recursive 318 /// function by one level. 319 /// 320 /// Note that while this routine is allowed to cleanup and optimize the 321 /// *inlined* code to minimize the actual inserted code, it must not delete 322 /// code in the caller as users of this routine may have pointers to 323 /// instructions in the caller that need to remain stable. 324 /// 325 /// If ForwardVarArgsTo is passed, inlining a function with varargs is allowed 326 /// and all varargs at the callsite will be passed to any calls to 327 /// ForwardVarArgsTo. The caller of InlineFunction has to make sure any varargs 328 /// are only used by ForwardVarArgsTo. 329 /// 330 /// The callee's function attributes are merged into the callers' if 331 /// MergeAttributes is set to true. 332 InlineResult InlineFunction(CallBase &CB, InlineFunctionInfo &IFI, 333 bool MergeAttributes = false, 334 AAResults *CalleeAAR = nullptr, 335 bool InsertLifetime = true, 336 Function *ForwardVarArgsTo = nullptr); 337 338 /// Same as above, but it will update the contextual profile. If the contextual 339 /// profile is invalid (i.e. not loaded because it is not present), it defaults 340 /// to the behavior of the non-contextual profile updating variant above. This 341 /// makes it easy to drop-in replace uses of the non-contextual overload. 342 InlineResult InlineFunction(CallBase &CB, InlineFunctionInfo &IFI, 343 PGOContextualProfile &CtxProf, 344 bool MergeAttributes = false, 345 AAResults *CalleeAAR = nullptr, 346 bool InsertLifetime = true, 347 Function *ForwardVarArgsTo = nullptr); 348 349 /// Clones a loop \p OrigLoop. Returns the loop and the blocks in \p 350 /// Blocks. 351 /// 352 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block 353 /// \p LoopDomBB. Insert the new blocks before block specified in \p Before. 354 /// Note: Only innermost loops are supported. 355 Loop *cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB, 356 Loop *OrigLoop, ValueToValueMapTy &VMap, 357 const Twine &NameSuffix, LoopInfo *LI, 358 DominatorTree *DT, 359 SmallVectorImpl<BasicBlock *> &Blocks); 360 361 /// Remaps instructions in \p Blocks using the mapping in \p VMap. 362 void remapInstructionsInBlocks(ArrayRef<BasicBlock *> Blocks, 363 ValueToValueMapTy &VMap); 364 365 /// Split edge between BB and PredBB and duplicate all non-Phi instructions 366 /// from BB between its beginning and the StopAt instruction into the split 367 /// block. Phi nodes are not duplicated, but their uses are handled correctly: 368 /// we replace them with the uses of corresponding Phi inputs. ValueMapping 369 /// is used to map the original instructions from BB to their newly-created 370 /// copies. Returns the split block. 371 BasicBlock *DuplicateInstructionsInSplitBetween(BasicBlock *BB, 372 BasicBlock *PredBB, 373 Instruction *StopAt, 374 ValueToValueMapTy &ValueMapping, 375 DomTreeUpdater &DTU); 376 377 /// Updates profile information by adjusting the entry count by adding 378 /// EntryDelta then scaling callsite information by the new count divided by the 379 /// old count. VMap is used during inlinng to also update the new clone 380 void updateProfileCallee( 381 Function *Callee, int64_t EntryDelta, 382 const ValueMap<const Value *, WeakTrackingVH> *VMap = nullptr); 383 384 /// Find the 'llvm.experimental.noalias.scope.decl' intrinsics in the specified 385 /// basic blocks and extract their scope. These are candidates for duplication 386 /// when cloning. 387 void identifyNoAliasScopesToClone( 388 ArrayRef<BasicBlock *> BBs, SmallVectorImpl<MDNode *> &NoAliasDeclScopes); 389 390 /// Find the 'llvm.experimental.noalias.scope.decl' intrinsics in the specified 391 /// instruction range and extract their scope. These are candidates for 392 /// duplication when cloning. 393 void identifyNoAliasScopesToClone( 394 BasicBlock::iterator Start, BasicBlock::iterator End, 395 SmallVectorImpl<MDNode *> &NoAliasDeclScopes); 396 397 /// Duplicate the specified list of noalias decl scopes. 398 /// The 'Ext' string is added as an extension to the name. 399 /// Afterwards, the ClonedScopes contains the mapping of the original scope 400 /// MDNode onto the cloned scope. 401 /// Be aware that the cloned scopes are still part of the original scope domain. 402 void cloneNoAliasScopes( 403 ArrayRef<MDNode *> NoAliasDeclScopes, 404 DenseMap<MDNode *, MDNode *> &ClonedScopes, 405 StringRef Ext, LLVMContext &Context); 406 407 /// Adapt the metadata for the specified instruction according to the 408 /// provided mapping. This is normally used after cloning an instruction, when 409 /// some noalias scopes needed to be cloned. 410 void adaptNoAliasScopes( 411 llvm::Instruction *I, const DenseMap<MDNode *, MDNode *> &ClonedScopes, 412 LLVMContext &Context); 413 414 /// Clone the specified noalias decl scopes. Then adapt all instructions in the 415 /// NewBlocks basicblocks to the cloned versions. 416 /// 'Ext' will be added to the duplicate scope names. 417 void cloneAndAdaptNoAliasScopes(ArrayRef<MDNode *> NoAliasDeclScopes, 418 ArrayRef<BasicBlock *> NewBlocks, 419 LLVMContext &Context, StringRef Ext); 420 421 /// Clone the specified noalias decl scopes. Then adapt all instructions in the 422 /// [IStart, IEnd] (IEnd included !) range to the cloned versions. 'Ext' will be 423 /// added to the duplicate scope names. 424 void cloneAndAdaptNoAliasScopes(ArrayRef<MDNode *> NoAliasDeclScopes, 425 Instruction *IStart, Instruction *IEnd, 426 LLVMContext &Context, StringRef Ext); 427 } // end namespace llvm 428 429 #endif // LLVM_TRANSFORMS_UTILS_CLONING_H 430