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 /// VMap contains no non-identity GlobalValue mappings and debug info metadata 123 /// will not be cloned. 124 /// 125 Function *CloneFunction(Function *F, ValueToValueMapTy &VMap, 126 ClonedCodeInfo *CodeInfo = nullptr); 127 128 /// Clone OldFunc into NewFunc, transforming the old arguments into references 129 /// to VMap values. Note that if NewFunc already has basic blocks, the ones 130 /// cloned into it will be added to the end of the function. This function 131 /// fills in a list of return instructions, and can optionally remap types 132 /// and/or append the specified suffix to all values cloned. 133 /// 134 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue 135 /// mappings. 136 /// 137 void CloneFunctionInto(Function *NewFunc, const Function *OldFunc, 138 ValueToValueMapTy &VMap, bool ModuleLevelChanges, 139 SmallVectorImpl<ReturnInst*> &Returns, 140 const char *NameSuffix = "", 141 ClonedCodeInfo *CodeInfo = nullptr, 142 ValueMapTypeRemapper *TypeMapper = nullptr, 143 ValueMaterializer *Materializer = nullptr); 144 145 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc, 146 const Instruction *StartingInst, 147 ValueToValueMapTy &VMap, bool ModuleLevelChanges, 148 SmallVectorImpl<ReturnInst *> &Returns, 149 const char *NameSuffix = "", 150 ClonedCodeInfo *CodeInfo = nullptr); 151 152 /// This works exactly like CloneFunctionInto, 153 /// except that it does some simple constant prop and DCE on the fly. The 154 /// effect of this is to copy significantly less code in cases where (for 155 /// example) a function call with constant arguments is inlined, and those 156 /// constant arguments cause a significant amount of code in the callee to be 157 /// dead. Since this doesn't produce an exactly copy of the input, it can't be 158 /// used for things like CloneFunction or CloneModule. 159 /// 160 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue 161 /// mappings. 162 /// 163 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 164 ValueToValueMapTy &VMap, bool ModuleLevelChanges, 165 SmallVectorImpl<ReturnInst*> &Returns, 166 const char *NameSuffix = "", 167 ClonedCodeInfo *CodeInfo = nullptr, 168 Instruction *TheCall = nullptr); 169 170 /// This class captures the data input to the InlineFunction call, and records 171 /// the auxiliary results produced by it. 172 class InlineFunctionInfo { 173 public: 174 explicit InlineFunctionInfo( 175 CallGraph *cg = nullptr, 176 function_ref<AssumptionCache &(Function &)> GetAssumptionCache = nullptr, 177 ProfileSummaryInfo *PSI = nullptr, 178 BlockFrequencyInfo *CallerBFI = nullptr, 179 BlockFrequencyInfo *CalleeBFI = nullptr) 180 : CG(cg), GetAssumptionCache(GetAssumptionCache), PSI(PSI), 181 CallerBFI(CallerBFI), CalleeBFI(CalleeBFI) {} 182 183 /// If non-null, InlineFunction will update the callgraph to reflect the 184 /// changes it makes. 185 CallGraph *CG; 186 function_ref<AssumptionCache &(Function &)> GetAssumptionCache; 187 ProfileSummaryInfo *PSI; 188 BlockFrequencyInfo *CallerBFI, *CalleeBFI; 189 190 /// InlineFunction fills this in with all static allocas that get copied into 191 /// the caller. 192 SmallVector<AllocaInst *, 4> StaticAllocas; 193 194 /// InlineFunction fills this in with callsites that were inlined from the 195 /// callee. This is only filled in if CG is non-null. 196 SmallVector<WeakTrackingVH, 8> InlinedCalls; 197 198 /// All of the new call sites inlined into the caller. 199 /// 200 /// 'InlineFunction' fills this in by scanning the inlined instructions, and 201 /// only if CG is null. If CG is non-null, instead the value handle 202 /// `InlinedCalls` above is used. 203 SmallVector<CallBase *, 8> InlinedCallSites; 204 205 void reset() { 206 StaticAllocas.clear(); 207 InlinedCalls.clear(); 208 InlinedCallSites.clear(); 209 } 210 }; 211 212 /// This function inlines the called function into the basic 213 /// block of the caller. This returns false if it is not possible to inline 214 /// this call. The program is still in a well defined state if this occurs 215 /// though. 216 /// 217 /// Note that this only does one level of inlining. For example, if the 218 /// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now 219 /// exists in the instruction stream. Similarly this will inline a recursive 220 /// function by one level. 221 /// 222 /// Note that while this routine is allowed to cleanup and optimize the 223 /// *inlined* code to minimize the actual inserted code, it must not delete 224 /// code in the caller as users of this routine may have pointers to 225 /// instructions in the caller that need to remain stable. 226 /// 227 /// If ForwardVarArgsTo is passed, inlining a function with varargs is allowed 228 /// and all varargs at the callsite will be passed to any calls to 229 /// ForwardVarArgsTo. The caller of InlineFunction has to make sure any varargs 230 /// are only used by ForwardVarArgsTo. 231 InlineResult InlineFunction(CallBase &CB, InlineFunctionInfo &IFI, 232 AAResults *CalleeAAR = nullptr, 233 bool InsertLifetime = true, 234 Function *ForwardVarArgsTo = nullptr); 235 236 /// Clones a loop \p OrigLoop. Returns the loop and the blocks in \p 237 /// Blocks. 238 /// 239 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block 240 /// \p LoopDomBB. Insert the new blocks before block specified in \p Before. 241 /// Note: Only innermost loops are supported. 242 Loop *cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB, 243 Loop *OrigLoop, ValueToValueMapTy &VMap, 244 const Twine &NameSuffix, LoopInfo *LI, 245 DominatorTree *DT, 246 SmallVectorImpl<BasicBlock *> &Blocks); 247 248 /// Remaps instructions in \p Blocks using the mapping in \p VMap. 249 void remapInstructionsInBlocks(const SmallVectorImpl<BasicBlock *> &Blocks, 250 ValueToValueMapTy &VMap); 251 252 /// Split edge between BB and PredBB and duplicate all non-Phi instructions 253 /// from BB between its beginning and the StopAt instruction into the split 254 /// block. Phi nodes are not duplicated, but their uses are handled correctly: 255 /// we replace them with the uses of corresponding Phi inputs. ValueMapping 256 /// is used to map the original instructions from BB to their newly-created 257 /// copies. Returns the split block. 258 BasicBlock *DuplicateInstructionsInSplitBetween(BasicBlock *BB, 259 BasicBlock *PredBB, 260 Instruction *StopAt, 261 ValueToValueMapTy &ValueMapping, 262 DomTreeUpdater &DTU); 263 264 /// Updates profile information by adjusting the entry count by adding 265 /// entryDelta then scaling callsite information by the new count divided by the 266 /// old count. VMap is used during inlinng to also update the new clone 267 void updateProfileCallee( 268 Function *Callee, int64_t entryDelta, 269 const ValueMap<const Value *, WeakTrackingVH> *VMap = nullptr); 270 271 } // end namespace llvm 272 273 #endif // LLVM_TRANSFORMS_UTILS_CLONING_H 274