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 CallGraph; 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 the cloned code contains a 'dynamic' alloca. 67 /// Dynamic allocas are allocas that are either not in the entry block or they 68 /// are in the entry block but are not a constant size. 69 bool ContainsDynamicAllocas = false; 70 71 /// All cloned call sites that have operand bundles attached are appended to 72 /// this vector. This vector may contain nulls or undefs if some of the 73 /// originally inserted callsites were DCE'ed after they were cloned. 74 std::vector<WeakTrackingVH> OperandBundleCallSites; 75 76 /// Like VMap, but maps only unsimplified instructions. Values in the map 77 /// may be dangling, it is only intended to be used via isSimplified(), to 78 /// check whether the main VMap mapping involves simplification or not. 79 DenseMap<const Value *, const Value *> OrigVMap; 80 81 ClonedCodeInfo() = default; 82 83 bool isSimplified(const Value *From, const Value *To) const { 84 return OrigVMap.lookup(From) != To; 85 } 86 }; 87 88 /// Return a copy of the specified basic block, but without 89 /// embedding the block into a particular function. The block returned is an 90 /// exact copy of the specified basic block, without any remapping having been 91 /// performed. Because of this, this is only suitable for applications where 92 /// the basic block will be inserted into the same function that it was cloned 93 /// from (loop unrolling would use this, for example). 94 /// 95 /// Also, note that this function makes a direct copy of the basic block, and 96 /// can thus produce illegal LLVM code. In particular, it will copy any PHI 97 /// nodes from the original block, even though there are no predecessors for the 98 /// newly cloned block (thus, phi nodes will have to be updated). Also, this 99 /// block will branch to the old successors of the original block: these 100 /// successors will have to have any PHI nodes updated to account for the new 101 /// incoming edges. 102 /// 103 /// The correlation between instructions in the source and result basic blocks 104 /// is recorded in the VMap map. 105 /// 106 /// If you have a particular suffix you'd like to use to add to any cloned 107 /// names, specify it as the optional third parameter. 108 /// 109 /// If you would like the basic block to be auto-inserted into the end of a 110 /// function, you can specify it as the optional fourth parameter. 111 /// 112 /// If you would like to collect additional information about the cloned 113 /// function, you can specify a ClonedCodeInfo object with the optional fifth 114 /// parameter. 115 BasicBlock *CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap, 116 const Twine &NameSuffix = "", Function *F = nullptr, 117 ClonedCodeInfo *CodeInfo = nullptr, 118 DebugInfoFinder *DIFinder = nullptr); 119 120 /// Return a copy of the specified function and add it to that 121 /// function's module. Also, any references specified in the VMap are changed 122 /// to refer to their mapped value instead of the original one. If any of the 123 /// arguments to the function are in the VMap, the arguments are deleted from 124 /// the resultant function. The VMap is updated to include mappings from all of 125 /// the instructions and basicblocks in the function from their old to new 126 /// values. The final argument captures information about the cloned code if 127 /// non-null. 128 /// 129 /// \pre VMap contains no non-identity GlobalValue mappings. 130 /// 131 Function *CloneFunction(Function *F, ValueToValueMapTy &VMap, 132 ClonedCodeInfo *CodeInfo = nullptr); 133 134 enum class CloneFunctionChangeType { 135 LocalChangesOnly, 136 GlobalChanges, 137 DifferentModule, 138 ClonedModule, 139 }; 140 141 /// Clone OldFunc into NewFunc, transforming the old arguments into references 142 /// to VMap values. Note that if NewFunc already has basic blocks, the ones 143 /// cloned into it will be added to the end of the function. This function 144 /// fills in a list of return instructions, and can optionally remap types 145 /// and/or append the specified suffix to all values cloned. 146 /// 147 /// If \p Changes is \a CloneFunctionChangeType::LocalChangesOnly, VMap is 148 /// required to contain no non-identity GlobalValue mappings. Otherwise, 149 /// referenced metadata will be cloned. 150 /// 151 /// If \p Changes is less than \a CloneFunctionChangeType::DifferentModule 152 /// indicating cloning into the same module (even if it's LocalChangesOnly), if 153 /// debug info metadata transitively references a \a DISubprogram, it will be 154 /// cloned, effectively upgrading \p Changes to GlobalChanges while suppressing 155 /// cloning of types and compile units. 156 /// 157 /// If \p Changes is \a CloneFunctionChangeType::DifferentModule, the new 158 /// module's \c !llvm.dbg.cu will get updated with any newly created compile 159 /// units. (\a CloneFunctionChangeType::ClonedModule leaves that work for the 160 /// caller.) 161 /// 162 /// FIXME: Consider simplifying this function by splitting out \a 163 /// CloneFunctionMetadataInto() and expecting / updating callers to call it 164 /// first when / how it's needed. 165 void CloneFunctionInto(Function *NewFunc, const Function *OldFunc, 166 ValueToValueMapTy &VMap, CloneFunctionChangeType Changes, 167 SmallVectorImpl<ReturnInst *> &Returns, 168 const char *NameSuffix = "", 169 ClonedCodeInfo *CodeInfo = nullptr, 170 ValueMapTypeRemapper *TypeMapper = nullptr, 171 ValueMaterializer *Materializer = nullptr); 172 173 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc, 174 const Instruction *StartingInst, 175 ValueToValueMapTy &VMap, bool ModuleLevelChanges, 176 SmallVectorImpl<ReturnInst *> &Returns, 177 const char *NameSuffix = "", 178 ClonedCodeInfo *CodeInfo = nullptr); 179 180 /// This works exactly like CloneFunctionInto, 181 /// except that it does some simple constant prop and DCE on the fly. The 182 /// effect of this is to copy significantly less code in cases where (for 183 /// example) a function call with constant arguments is inlined, and those 184 /// constant arguments cause a significant amount of code in the callee to be 185 /// dead. Since this doesn't produce an exactly copy of the input, it can't be 186 /// used for things like CloneFunction or CloneModule. 187 /// 188 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue 189 /// mappings. 190 /// 191 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 192 ValueToValueMapTy &VMap, bool ModuleLevelChanges, 193 SmallVectorImpl<ReturnInst*> &Returns, 194 const char *NameSuffix = "", 195 ClonedCodeInfo *CodeInfo = nullptr); 196 197 /// This class captures the data input to the InlineFunction call, and records 198 /// the auxiliary results produced by it. 199 class InlineFunctionInfo { 200 public: 201 explicit InlineFunctionInfo( 202 CallGraph *cg = nullptr, 203 function_ref<AssumptionCache &(Function &)> GetAssumptionCache = nullptr, 204 ProfileSummaryInfo *PSI = nullptr, 205 BlockFrequencyInfo *CallerBFI = nullptr, 206 BlockFrequencyInfo *CalleeBFI = nullptr, bool UpdateProfile = true) 207 : CG(cg), GetAssumptionCache(GetAssumptionCache), PSI(PSI), 208 CallerBFI(CallerBFI), CalleeBFI(CalleeBFI), 209 UpdateProfile(UpdateProfile) {} 210 211 /// If non-null, InlineFunction will update the callgraph to reflect the 212 /// changes it makes. 213 CallGraph *CG; 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 InlineResult InlineFunction(CallBase &CB, InlineFunctionInfo &IFI, 264 AAResults *CalleeAAR = nullptr, 265 bool InsertLifetime = true, 266 Function *ForwardVarArgsTo = nullptr); 267 268 /// Clones a loop \p OrigLoop. Returns the loop and the blocks in \p 269 /// Blocks. 270 /// 271 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block 272 /// \p LoopDomBB. Insert the new blocks before block specified in \p Before. 273 /// Note: Only innermost loops are supported. 274 Loop *cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB, 275 Loop *OrigLoop, ValueToValueMapTy &VMap, 276 const Twine &NameSuffix, LoopInfo *LI, 277 DominatorTree *DT, 278 SmallVectorImpl<BasicBlock *> &Blocks); 279 280 /// Remaps instructions in \p Blocks using the mapping in \p VMap. 281 void remapInstructionsInBlocks(const SmallVectorImpl<BasicBlock *> &Blocks, 282 ValueToValueMapTy &VMap); 283 284 /// Split edge between BB and PredBB and duplicate all non-Phi instructions 285 /// from BB between its beginning and the StopAt instruction into the split 286 /// block. Phi nodes are not duplicated, but their uses are handled correctly: 287 /// we replace them with the uses of corresponding Phi inputs. ValueMapping 288 /// is used to map the original instructions from BB to their newly-created 289 /// copies. Returns the split block. 290 BasicBlock *DuplicateInstructionsInSplitBetween(BasicBlock *BB, 291 BasicBlock *PredBB, 292 Instruction *StopAt, 293 ValueToValueMapTy &ValueMapping, 294 DomTreeUpdater &DTU); 295 296 /// Updates profile information by adjusting the entry count by adding 297 /// EntryDelta then scaling callsite information by the new count divided by the 298 /// old count. VMap is used during inlinng to also update the new clone 299 void updateProfileCallee( 300 Function *Callee, int64_t EntryDelta, 301 const ValueMap<const Value *, WeakTrackingVH> *VMap = nullptr); 302 303 /// Find the 'llvm.experimental.noalias.scope.decl' intrinsics in the specified 304 /// basic blocks and extract their scope. These are candidates for duplication 305 /// when cloning. 306 void identifyNoAliasScopesToClone( 307 ArrayRef<BasicBlock *> BBs, SmallVectorImpl<MDNode *> &NoAliasDeclScopes); 308 309 /// Find the 'llvm.experimental.noalias.scope.decl' intrinsics in the specified 310 /// instruction range and extract their scope. These are candidates for 311 /// duplication when cloning. 312 void identifyNoAliasScopesToClone( 313 BasicBlock::iterator Start, BasicBlock::iterator End, 314 SmallVectorImpl<MDNode *> &NoAliasDeclScopes); 315 316 /// Duplicate the specified list of noalias decl scopes. 317 /// The 'Ext' string is added as an extension to the name. 318 /// Afterwards, the ClonedScopes contains the mapping of the original scope 319 /// MDNode onto the cloned scope. 320 /// Be aware that the cloned scopes are still part of the original scope domain. 321 void cloneNoAliasScopes( 322 ArrayRef<MDNode *> NoAliasDeclScopes, 323 DenseMap<MDNode *, MDNode *> &ClonedScopes, 324 StringRef Ext, LLVMContext &Context); 325 326 /// Adapt the metadata for the specified instruction according to the 327 /// provided mapping. This is normally used after cloning an instruction, when 328 /// some noalias scopes needed to be cloned. 329 void adaptNoAliasScopes( 330 llvm::Instruction *I, const DenseMap<MDNode *, MDNode *> &ClonedScopes, 331 LLVMContext &Context); 332 333 /// Clone the specified noalias decl scopes. Then adapt all instructions in the 334 /// NewBlocks basicblocks to the cloned versions. 335 /// 'Ext' will be added to the duplicate scope names. 336 void cloneAndAdaptNoAliasScopes(ArrayRef<MDNode *> NoAliasDeclScopes, 337 ArrayRef<BasicBlock *> NewBlocks, 338 LLVMContext &Context, StringRef Ext); 339 340 /// Clone the specified noalias decl scopes. Then adapt all instructions in the 341 /// [IStart, IEnd] (IEnd included !) range to the cloned versions. 'Ext' will be 342 /// added to the duplicate scope names. 343 void cloneAndAdaptNoAliasScopes(ArrayRef<MDNode *> NoAliasDeclScopes, 344 Instruction *IStart, Instruction *IEnd, 345 LLVMContext &Context, StringRef Ext); 346 } // end namespace llvm 347 348 #endif // LLVM_TRANSFORMS_UTILS_CLONING_H 349