include/llvm/Transforms/Utils/Cloning.h

   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/AliasAnalysis.h"
  23 #include "llvm/Analysis/AssumptionCache.h"
  24 #include "llvm/Analysis/InlineCost.h"
  25 #include "llvm/IR/CallSite.h"
  26 #include "llvm/IR/ValueHandle.h"
  27 #include "llvm/Transforms/Utils/ValueMapper.h"
  28 #include <functional>
  29 #include <memory>
  30 #include <vector>
  31
  32 namespace llvm {
  33
  34 class AllocaInst;
  35 class BasicBlock;
  36 class BlockFrequencyInfo;
  37 class CallInst;
  38 class CallGraph;
  39 class DebugInfoFinder;
  40 class DominatorTree;
  41 class Function;
  42 class Instruction;
  43 class InvokeInst;
  44 class Loop;
  45 class LoopInfo;
  46 class Module;
  47 class ProfileSummaryInfo;
  48 class ReturnInst;
  49 class DomTreeUpdater;
  50
  51 /// Return an exact copy of the specified module
  52 std::unique_ptr<Module> CloneModule(const Module &M);
  53 std::unique_ptr<Module> CloneModule(const Module &M, ValueToValueMapTy &VMap);
  54
  55 /// Return a copy of the specified module. The ShouldCloneDefinition function
  56 /// controls whether a specific GlobalValue's definition is cloned. If the
  57 /// function returns false, the module copy will contain an external reference
  58 /// in place of the global definition.
  59 std::unique_ptr<Module>
  60 CloneModule(const Module &M, ValueToValueMapTy &VMap,
  61             function_ref<bool(const GlobalValue *)> ShouldCloneDefinition);
  62
  63 /// This struct can be used to capture information about code
  64 /// being cloned, while it is being cloned.
  65 struct ClonedCodeInfo {
  66   /// This is set to true if the cloned code contains a normal call instruction.
  67   bool ContainsCalls = 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   ClonedCodeInfo() = default;
  80 };
  81
  82 /// Return a copy of the specified basic block, but without
  83 /// embedding the block into a particular function.  The block returned is an
  84 /// exact copy of the specified basic block, without any remapping having been
  85 /// performed.  Because of this, this is only suitable for applications where
  86 /// the basic block will be inserted into the same function that it was cloned
  87 /// from (loop unrolling would use this, for example).
  88 ///
  89 /// Also, note that this function makes a direct copy of the basic block, and
  90 /// can thus produce illegal LLVM code.  In particular, it will copy any PHI
  91 /// nodes from the original block, even though there are no predecessors for the
  92 /// newly cloned block (thus, phi nodes will have to be updated).  Also, this
  93 /// block will branch to the old successors of the original block: these
  94 /// successors will have to have any PHI nodes updated to account for the new
  95 /// incoming edges.
  96 ///
  97 /// The correlation between instructions in the source and result basic blocks
  98 /// is recorded in the VMap map.
  99 ///
 100 /// If you have a particular suffix you'd like to use to add to any cloned
 101 /// names, specify it as the optional third parameter.
 102 ///
 103 /// If you would like the basic block to be auto-inserted into the end of a
 104 /// function, you can specify it as the optional fourth parameter.
 105 ///
 106 /// If you would like to collect additional information about the cloned
 107 /// function, you can specify a ClonedCodeInfo object with the optional fifth
 108 /// parameter.
 109 BasicBlock *CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap,
 110                             const Twine &NameSuffix = "", Function *F = nullptr,
 111                             ClonedCodeInfo *CodeInfo = nullptr,
 112                             DebugInfoFinder *DIFinder = nullptr);
 113
 114 /// Return a copy of the specified function and add it to that
 115 /// function's module.  Also, any references specified in the VMap are changed
 116 /// to refer to their mapped value instead of the original one.  If any of the
 117 /// arguments to the function are in the VMap, the arguments are deleted from
 118 /// the resultant function.  The VMap is updated to include mappings from all of
 119 /// the instructions and basicblocks in the function from their old to new
 120 /// values.  The final argument captures information about the cloned code if
 121 /// non-null.
 122 ///
 123 /// VMap contains no non-identity GlobalValue mappings and debug info metadata
 124 /// will not be cloned.
 125 ///
 126 Function *CloneFunction(Function *F, ValueToValueMapTy &VMap,
 127                         ClonedCodeInfo *CodeInfo = nullptr);
 128
 129 /// Clone OldFunc into NewFunc, transforming the old arguments into references
 130 /// to VMap values.  Note that if NewFunc already has basic blocks, the ones
 131 /// cloned into it will be added to the end of the function.  This function
 132 /// fills in a list of return instructions, and can optionally remap types
 133 /// and/or append the specified suffix to all values cloned.
 134 ///
 135 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
 136 /// mappings.
 137 ///
 138 void CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
 139                        ValueToValueMapTy &VMap, bool ModuleLevelChanges,
 140                        SmallVectorImpl<ReturnInst*> &Returns,
 141                        const char *NameSuffix = "",
 142                        ClonedCodeInfo *CodeInfo = nullptr,
 143                        ValueMapTypeRemapper *TypeMapper = nullptr,
 144                        ValueMaterializer *Materializer = nullptr);
 145
 146 void CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
 147                                const Instruction *StartingInst,
 148                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
 149                                SmallVectorImpl<ReturnInst *> &Returns,
 150                                const char *NameSuffix = "",
 151                                ClonedCodeInfo *CodeInfo = nullptr);
 152
 153 /// This works exactly like CloneFunctionInto,
 154 /// except that it does some simple constant prop and DCE on the fly.  The
 155 /// effect of this is to copy significantly less code in cases where (for
 156 /// example) a function call with constant arguments is inlined, and those
 157 /// constant arguments cause a significant amount of code in the callee to be
 158 /// dead.  Since this doesn't produce an exactly copy of the input, it can't be
 159 /// used for things like CloneFunction or CloneModule.
 160 ///
 161 /// If ModuleLevelChanges is false, VMap contains no non-identity GlobalValue
 162 /// mappings.
 163 ///
 164 void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
 165                                ValueToValueMapTy &VMap, bool ModuleLevelChanges,
 166                                SmallVectorImpl<ReturnInst*> &Returns,
 167                                const char *NameSuffix = "",
 168                                ClonedCodeInfo *CodeInfo = nullptr,
 169                                Instruction *TheCall = nullptr);
 170
 171 /// This class captures the data input to the InlineFunction call, and records
 172 /// the auxiliary results produced by it.
 173 class InlineFunctionInfo {
 174 public:
 175   explicit InlineFunctionInfo(CallGraph *cg = nullptr,
 176                               std::function<AssumptionCache &(Function &)>
 177                                   *GetAssumptionCache = nullptr,
 178                               ProfileSummaryInfo *PSI = nullptr,
 179                               BlockFrequencyInfo *CallerBFI = nullptr,
 180                               BlockFrequencyInfo *CalleeBFI = nullptr)
 181       : CG(cg), GetAssumptionCache(GetAssumptionCache), PSI(PSI),
 182         CallerBFI(CallerBFI), CalleeBFI(CalleeBFI) {}
 183
 184   /// If non-null, InlineFunction will update the callgraph to reflect the
 185   /// changes it makes.
 186   CallGraph *CG;
 187   std::function<AssumptionCache &(Function &)> *GetAssumptionCache;
 188   ProfileSummaryInfo *PSI;
 189   BlockFrequencyInfo *CallerBFI, *CalleeBFI;
 190
 191   /// InlineFunction fills this in with all static allocas that get copied into
 192   /// the caller.
 193   SmallVector<AllocaInst *, 4> StaticAllocas;
 194
 195   /// InlineFunction fills this in with callsites that were inlined from the
 196   /// callee. This is only filled in if CG is non-null.
 197   SmallVector<WeakTrackingVH, 8> InlinedCalls;
 198
 199   /// All of the new call sites inlined into the caller.
 200   ///
 201   /// 'InlineFunction' fills this in by scanning the inlined instructions, and
 202   /// only if CG is null. If CG is non-null, instead the value handle
 203   /// `InlinedCalls` above is used.
 204   SmallVector<CallSite, 8> InlinedCallSites;
 205
 206   void reset() {
 207     StaticAllocas.clear();
 208     InlinedCalls.clear();
 209     InlinedCallSites.clear();
 210   }
 211 };
 212
 213 /// This function inlines the called function into the basic
 214 /// block of the caller.  This returns false if it is not possible to inline
 215 /// this call.  The program is still in a well defined state if this occurs
 216 /// though.
 217 ///
 218 /// Note that this only does one level of inlining.  For example, if the
 219 /// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
 220 /// exists in the instruction stream.  Similarly this will inline a recursive
 221 /// function by one level.
 222 ///
 223 /// Note that while this routine is allowed to cleanup and optimize the
 224 /// *inlined* code to minimize the actual inserted code, it must not delete
 225 /// code in the caller as users of this routine may have pointers to
 226 /// instructions in the caller that need to remain stable.
 227 ///
 228 /// If ForwardVarArgsTo is passed, inlining a function with varargs is allowed
 229 /// and all varargs at the callsite will be passed to any calls to
 230 /// ForwardVarArgsTo. The caller of InlineFunction has to make sure any varargs
 231 /// are only used by ForwardVarArgsTo.
 232 InlineResult InlineFunction(CallBase *CB, InlineFunctionInfo &IFI,
 233                             AAResults *CalleeAAR = nullptr,
 234                             bool InsertLifetime = true);
 235 InlineResult InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
 236                             AAResults *CalleeAAR = nullptr,
 237                             bool InsertLifetime = true,
 238                             Function *ForwardVarArgsTo = nullptr);
 239
 240 /// Clones a loop \p OrigLoop.  Returns the loop and the blocks in \p
 241 /// Blocks.
 242 ///
 243 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block
 244 /// \p LoopDomBB.  Insert the new blocks before block specified in \p Before.
 245 /// Note: Only innermost loops are supported.
 246 Loop *cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
 247                              Loop *OrigLoop, ValueToValueMapTy &VMap,
 248                              const Twine &NameSuffix, LoopInfo *LI,
 249                              DominatorTree *DT,
 250                              SmallVectorImpl<BasicBlock *> &Blocks);
 251
 252 /// Remaps instructions in \p Blocks using the mapping in \p VMap.
 253 void remapInstructionsInBlocks(const SmallVectorImpl<BasicBlock *> &Blocks,
 254                                ValueToValueMapTy &VMap);
 255
 256 /// Split edge between BB and PredBB and duplicate all non-Phi instructions
 257 /// from BB between its beginning and the StopAt instruction into the split
 258 /// block. Phi nodes are not duplicated, but their uses are handled correctly:
 259 /// we replace them with the uses of corresponding Phi inputs. ValueMapping
 260 /// is used to map the original instructions from BB to their newly-created
 261 /// copies. Returns the split block.
 262 BasicBlock *DuplicateInstructionsInSplitBetween(BasicBlock *BB,
 263                                                 BasicBlock *PredBB,
 264                                                 Instruction *StopAt,
 265                                                 ValueToValueMapTy &ValueMapping,
 266                                                 DomTreeUpdater &DTU);
 267
 268 /// Updates profile information by adjusting the entry count by adding
 269 /// entryDelta then scaling callsite information by the new count divided by the
 270 /// old count. VMap is used during inlinng to also update the new clone
 271 void updateProfileCallee(
 272     Function *Callee, int64_t entryDelta,
 273     const ValueMap<const Value *, WeakTrackingVH> *VMap = nullptr);
 274
 275 } // end namespace llvm
 276
 277 #endif // LLVM_TRANSFORMS_UTILS_CLONING_H