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 ProfileSummaryInfo; 45 class ReturnInst; 46 class DomTreeUpdater; 47 48 /// Return an exact copy of the specified module 49 std::unique_ptr<Module> CloneModule(const Module &M); 50 std::unique_ptr<Module> CloneModule(const Module &M, ValueToValueMapTy &VMap); 51 52 /// Return a copy of the specified module. The ShouldCloneDefinition function 53 /// controls whether a specific GlobalValue's definition is cloned. If the 54 /// function returns false, the module copy will contain an external reference 55 /// in place of the global definition. 56 std::unique_ptr<Module> 57 CloneModule(const Module &M, ValueToValueMapTy &VMap, 58 function_ref<bool(const GlobalValue *)> ShouldCloneDefinition); 59 60 /// This struct can be used to capture information about code 61 /// being cloned, while it is being cloned. 62 struct ClonedCodeInfo { 63 /// This is set to true if the cloned code contains a normal call instruction. 64 bool ContainsCalls = false; 65 66 /// This is set to true if there is memprof related metadata (memprof or 67 /// callsite metadata) in the cloned code. 68 bool ContainsMemProfMetadata = false; 69 70 /// This is set to true if the cloned code contains a 'dynamic' alloca. 71 /// Dynamic allocas are allocas that are either not in the entry block or they 72 /// are in the entry block but are not a constant size. 73 bool ContainsDynamicAllocas = false; 74 75 /// All cloned call sites that have operand bundles attached are appended to 76 /// this vector. This vector may contain nulls or undefs if some of the 77 /// originally inserted callsites were DCE'ed after they were cloned. 78 std::vector<WeakTrackingVH> OperandBundleCallSites; 79 80 /// Like VMap, but maps only unsimplified instructions. Values in the map 81 /// may be dangling, it is only intended to be used via isSimplified(), to 82 /// check whether the main VMap mapping involves simplification or not. 83 DenseMap<const Value *, const Value *> OrigVMap; 84 85 ClonedCodeInfo() = default; 86 isSimplifiedClonedCodeInfo87 bool isSimplified(const Value *From, const Value *To) const { 88 return OrigVMap.lookup(From) != To; 89 } 90 }; 91 92 /// Return a copy of the specified basic block, but without 93 /// embedding the block into a particular function. The block returned is an 94 /// exact copy of the specified basic block, without any remapping having been 95 /// performed. Because of this, this is only suitable for applications where 96 /// the basic block will be inserted into the same function that it was cloned 97 /// from (loop unrolling would use this, for example). 98 /// 99 /// Also, note that this function makes a direct copy of the basic block, and 100 /// can thus produce illegal LLVM code. In particular, it will copy any PHI 101 /// nodes from the original block, even though there are no predecessors for the 102 /// newly cloned block (thus, phi nodes will have to be updated). Also, this 103 /// block will branch to the old successors of the original block: these 104 /// successors will have to have any PHI nodes updated to account for the new 105 /// incoming edges. 106 /// 107 /// The correlation between instructions in the source and result basic blocks 108 /// is recorded in the VMap map. 109 /// 110 /// If you have a particular suffix you'd like to use to add to any cloned 111 /// names, specify it as the optional third parameter. 112 /// 113 /// If you would like the basic block to be auto-inserted into the end of a 114 /// function, you can specify it as the optional fourth parameter. 115 /// 116 /// If you would like to collect additional information about the cloned 117 /// function, you can specify a ClonedCodeInfo object with the optional fifth 118 /// parameter. 119 BasicBlock *CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap, 120 const Twine &NameSuffix = "", Function *F = nullptr, 121 ClonedCodeInfo *CodeInfo = nullptr, 122 DebugInfoFinder *DIFinder = 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 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc, 178 const Instruction *StartingInst, 179 ValueToValueMapTy &VMap, bool ModuleLevelChanges, 180 SmallVectorImpl<ReturnInst *> &Returns, 181 const char *NameSuffix = "", 182 ClonedCodeInfo *CodeInfo = nullptr); 183 184 /// This works exactly like CloneFunctionInto, 185 /// except that it does some simple constant prop and DCE on the fly. The 186 /// effect of this is to copy significantly less code in cases where (for 187 /// example) a function call with constant arguments is inlined, and those 188 /// constant arguments cause a significant amount of code in the callee to be 189 /// dead. Since this doesn't produce an exactly copy of the input, it can't be 190 /// used for things like CloneFunction or CloneModule. 191 /// 192 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue 193 /// mappings. 194 /// 195 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 196 ValueToValueMapTy &VMap, bool ModuleLevelChanges, 197 SmallVectorImpl<ReturnInst*> &Returns, 198 const char *NameSuffix = "", 199 ClonedCodeInfo *CodeInfo = nullptr); 200 201 /// This class captures the data input to the InlineFunction call, and records 202 /// the auxiliary results produced by it. 203 class InlineFunctionInfo { 204 public: 205 explicit InlineFunctionInfo( 206 function_ref<AssumptionCache &(Function &)> GetAssumptionCache = nullptr, 207 ProfileSummaryInfo *PSI = nullptr, 208 BlockFrequencyInfo *CallerBFI = nullptr, 209 BlockFrequencyInfo *CalleeBFI = nullptr, bool UpdateProfile = true) GetAssumptionCache(GetAssumptionCache)210 : GetAssumptionCache(GetAssumptionCache), PSI(PSI), CallerBFI(CallerBFI), 211 CalleeBFI(CalleeBFI), UpdateProfile(UpdateProfile) {} 212 213 /// If non-null, InlineFunction will update the callgraph to reflect the 214 /// changes it makes. 215 function_ref<AssumptionCache &(Function &)> GetAssumptionCache; 216 ProfileSummaryInfo *PSI; 217 BlockFrequencyInfo *CallerBFI, *CalleeBFI; 218 219 /// InlineFunction fills this in with all static allocas that get copied into 220 /// the caller. 221 SmallVector<AllocaInst *, 4> StaticAllocas; 222 223 /// InlineFunction fills this in with callsites that were inlined from the 224 /// callee. This is only filled in if CG is non-null. 225 SmallVector<WeakTrackingVH, 8> InlinedCalls; 226 227 /// All of the new call sites inlined into the caller. 228 /// 229 /// 'InlineFunction' fills this in by scanning the inlined instructions, and 230 /// only if CG is null. If CG is non-null, instead the value handle 231 /// `InlinedCalls` above is used. 232 SmallVector<CallBase *, 8> InlinedCallSites; 233 234 /// Update profile for callee as well as cloned version. We need to do this 235 /// for regular inlining, but not for inlining from sample profile loader. 236 bool UpdateProfile; 237 reset()238 void reset() { 239 StaticAllocas.clear(); 240 InlinedCalls.clear(); 241 InlinedCallSites.clear(); 242 } 243 }; 244 245 /// This function inlines the called function into the basic 246 /// block of the caller. This returns false if it is not possible to inline 247 /// this call. The program is still in a well defined state if this occurs 248 /// though. 249 /// 250 /// Note that this only does one level of inlining. For example, if the 251 /// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 252 /// exists in the instruction stream. Similarly this will inline a recursive 253 /// function by one level. 254 /// 255 /// Note that while this routine is allowed to cleanup and optimize the 256 /// *inlined* code to minimize the actual inserted code, it must not delete 257 /// code in the caller as users of this routine may have pointers to 258 /// instructions in the caller that need to remain stable. 259 /// 260 /// If ForwardVarArgsTo is passed, inlining a function with varargs is allowed 261 /// and all varargs at the callsite will be passed to any calls to 262 /// ForwardVarArgsTo. The caller of InlineFunction has to make sure any varargs 263 /// are only used by ForwardVarArgsTo. 264 /// 265 /// The callee's function attributes are merged into the callers' if 266 /// MergeAttributes is set to true. 267 InlineResult InlineFunction(CallBase &CB, InlineFunctionInfo &IFI, 268 bool MergeAttributes = false, 269 AAResults *CalleeAAR = nullptr, 270 bool InsertLifetime = true, 271 Function *ForwardVarArgsTo = nullptr); 272 273 /// Clones a loop \p OrigLoop. Returns the loop and the blocks in \p 274 /// Blocks. 275 /// 276 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block 277 /// \p LoopDomBB. Insert the new blocks before block specified in \p Before. 278 /// Note: Only innermost loops are supported. 279 Loop *cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB, 280 Loop *OrigLoop, ValueToValueMapTy &VMap, 281 const Twine &NameSuffix, LoopInfo *LI, 282 DominatorTree *DT, 283 SmallVectorImpl<BasicBlock *> &Blocks); 284 285 /// Remaps instructions in \p Blocks using the mapping in \p VMap. 286 void remapInstructionsInBlocks(ArrayRef<BasicBlock *> Blocks, 287 ValueToValueMapTy &VMap); 288 289 /// Split edge between BB and PredBB and duplicate all non-Phi instructions 290 /// from BB between its beginning and the StopAt instruction into the split 291 /// block. Phi nodes are not duplicated, but their uses are handled correctly: 292 /// we replace them with the uses of corresponding Phi inputs. ValueMapping 293 /// is used to map the original instructions from BB to their newly-created 294 /// copies. Returns the split block. 295 BasicBlock *DuplicateInstructionsInSplitBetween(BasicBlock *BB, 296 BasicBlock *PredBB, 297 Instruction *StopAt, 298 ValueToValueMapTy &ValueMapping, 299 DomTreeUpdater &DTU); 300 301 /// Updates profile information by adjusting the entry count by adding 302 /// EntryDelta then scaling callsite information by the new count divided by the 303 /// old count. VMap is used during inlinng to also update the new clone 304 void updateProfileCallee( 305 Function *Callee, int64_t EntryDelta, 306 const ValueMap<const Value *, WeakTrackingVH> *VMap = nullptr); 307 308 /// Find the 'llvm.experimental.noalias.scope.decl' intrinsics in the specified 309 /// basic blocks and extract their scope. These are candidates for duplication 310 /// when cloning. 311 void identifyNoAliasScopesToClone( 312 ArrayRef<BasicBlock *> BBs, SmallVectorImpl<MDNode *> &NoAliasDeclScopes); 313 314 /// Find the 'llvm.experimental.noalias.scope.decl' intrinsics in the specified 315 /// instruction range and extract their scope. These are candidates for 316 /// duplication when cloning. 317 void identifyNoAliasScopesToClone( 318 BasicBlock::iterator Start, BasicBlock::iterator End, 319 SmallVectorImpl<MDNode *> &NoAliasDeclScopes); 320 321 /// Duplicate the specified list of noalias decl scopes. 322 /// The 'Ext' string is added as an extension to the name. 323 /// Afterwards, the ClonedScopes contains the mapping of the original scope 324 /// MDNode onto the cloned scope. 325 /// Be aware that the cloned scopes are still part of the original scope domain. 326 void cloneNoAliasScopes( 327 ArrayRef<MDNode *> NoAliasDeclScopes, 328 DenseMap<MDNode *, MDNode *> &ClonedScopes, 329 StringRef Ext, LLVMContext &Context); 330 331 /// Adapt the metadata for the specified instruction according to the 332 /// provided mapping. This is normally used after cloning an instruction, when 333 /// some noalias scopes needed to be cloned. 334 void adaptNoAliasScopes( 335 llvm::Instruction *I, const DenseMap<MDNode *, MDNode *> &ClonedScopes, 336 LLVMContext &Context); 337 338 /// Clone the specified noalias decl scopes. Then adapt all instructions in the 339 /// NewBlocks basicblocks to the cloned versions. 340 /// 'Ext' will be added to the duplicate scope names. 341 void cloneAndAdaptNoAliasScopes(ArrayRef<MDNode *> NoAliasDeclScopes, 342 ArrayRef<BasicBlock *> NewBlocks, 343 LLVMContext &Context, StringRef Ext); 344 345 /// Clone the specified noalias decl scopes. Then adapt all instructions in the 346 /// [IStart, IEnd] (IEnd included !) range to the cloned versions. 'Ext' will be 347 /// added to the duplicate scope names. 348 void cloneAndAdaptNoAliasScopes(ArrayRef<MDNode *> NoAliasDeclScopes, 349 Instruction *IStart, Instruction *IEnd, 350 LLVMContext &Context, StringRef Ext); 351 } // end namespace llvm 352 353 #endif // LLVM_TRANSFORMS_UTILS_CLONING_H 354