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