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