lib/Transforms/Utils/CloneFunction.cpp

   1 //===- CloneFunction.cpp - Clone a function into another function ---------===//
   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 implements the CloneFunctionInto interface, which is used as the
  10 // low-level function cloner.  This is used by the CloneFunction and function
  11 // inliner to do the dirty work of copying the body of a function around.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/ADT/SetVector.h"
  16 #include "llvm/ADT/SmallVector.h"
  17 #include "llvm/Analysis/ConstantFolding.h"
  18 #include "llvm/Analysis/DomTreeUpdater.h"
  19 #include "llvm/Analysis/InstructionSimplify.h"
  20 #include "llvm/Analysis/LoopInfo.h"
  21 #include "llvm/IR/CFG.h"
  22 #include "llvm/IR/Constants.h"
  23 #include "llvm/IR/DebugInfo.h"
  24 #include "llvm/IR/DerivedTypes.h"
  25 #include "llvm/IR/Function.h"
  26 #include "llvm/IR/GlobalVariable.h"
  27 #include "llvm/IR/Instructions.h"
  28 #include "llvm/IR/IntrinsicInst.h"
  29 #include "llvm/IR/LLVMContext.h"
  30 #include "llvm/IR/Metadata.h"
  31 #include "llvm/IR/Module.h"
  32 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  33 #include "llvm/Transforms/Utils/Cloning.h"
  34 #include "llvm/Transforms/Utils/Local.h"
  35 #include "llvm/Transforms/Utils/ValueMapper.h"
  36 #include <map>
  37 using namespace llvm;
  38
  39 /// See comments in Cloning.h.
  40 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap,
  41                                   const Twine &NameSuffix, Function *F,
  42                                   ClonedCodeInfo *CodeInfo,
  43                                   DebugInfoFinder *DIFinder) {
  44   DenseMap<const MDNode *, MDNode *> Cache;
  45   BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
  46   if (BB->hasName())
  47     NewBB->setName(BB->getName() + NameSuffix);
  48
  49   bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
  50   Module *TheModule = F ? F->getParent() : nullptr;
  51
  52   // Loop over all instructions, and copy them over.
  53   for (const Instruction &I : *BB) {
  54     if (DIFinder && TheModule)
  55       DIFinder->processInstruction(*TheModule, I);
  56
  57     Instruction *NewInst = I.clone();
  58     if (I.hasName())
  59       NewInst->setName(I.getName() + NameSuffix);
  60     NewBB->getInstList().push_back(NewInst);
  61     VMap[&I] = NewInst; // Add instruction map to value.
  62
  63     hasCalls |= (isa<CallInst>(I) && !isa<DbgInfoIntrinsic>(I));
  64     if (const AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
  65       if (isa<ConstantInt>(AI->getArraySize()))
  66         hasStaticAllocas = true;
  67       else
  68         hasDynamicAllocas = true;
  69     }
  70   }
  71
  72   if (CodeInfo) {
  73     CodeInfo->ContainsCalls          |= hasCalls;
  74     CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
  75     CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
  76                                         BB != &BB->getParent()->getEntryBlock();
  77   }
  78   return NewBB;
  79 }
  80
  81 // Clone OldFunc into NewFunc, transforming the old arguments into references to
  82 // VMap values.
  83 //
  84 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
  85                              ValueToValueMapTy &VMap,
  86                              bool ModuleLevelChanges,
  87                              SmallVectorImpl<ReturnInst*> &Returns,
  88                              const char *NameSuffix, ClonedCodeInfo *CodeInfo,
  89                              ValueMapTypeRemapper *TypeMapper,
  90                              ValueMaterializer *Materializer) {
  91   assert(NameSuffix && "NameSuffix cannot be null!");
  92
  93 #ifndef NDEBUG
  94   for (const Argument &I : OldFunc->args())
  95     assert(VMap.count(&I) && "No mapping from source argument specified!");
  96 #endif
  97
  98   // Copy all attributes other than those stored in the AttributeList.  We need
  99   // to remap the parameter indices of the AttributeList.
 100   AttributeList NewAttrs = NewFunc->getAttributes();
 101   NewFunc->copyAttributesFrom(OldFunc);
 102   NewFunc->setAttributes(NewAttrs);
 103
 104   // Fix up the personality function that got copied over.
 105   if (OldFunc->hasPersonalityFn())
 106     NewFunc->setPersonalityFn(
 107         MapValue(OldFunc->getPersonalityFn(), VMap,
 108                  ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
 109                  TypeMapper, Materializer));
 110
 111   SmallVector<AttributeSet, 4> NewArgAttrs(NewFunc->arg_size());
 112   AttributeList OldAttrs = OldFunc->getAttributes();
 113
 114   // Clone any argument attributes that are present in the VMap.
 115   for (const Argument &OldArg : OldFunc->args()) {
 116     if (Argument *NewArg = dyn_cast<Argument>(VMap[&OldArg])) {
 117       NewArgAttrs[NewArg->getArgNo()] =
 118           OldAttrs.getParamAttributes(OldArg.getArgNo());
 119     }
 120   }
 121
 122   NewFunc->setAttributes(
 123       AttributeList::get(NewFunc->getContext(), OldAttrs.getFnAttributes(),
 124                          OldAttrs.getRetAttributes(), NewArgAttrs));
 125
 126   bool MustCloneSP =
 127       OldFunc->getParent() && OldFunc->getParent() == NewFunc->getParent();
 128   DISubprogram *SP = OldFunc->getSubprogram();
 129   if (SP) {
 130     assert(!MustCloneSP || ModuleLevelChanges);
 131     // Add mappings for some DebugInfo nodes that we don't want duplicated
 132     // even if they're distinct.
 133     auto &MD = VMap.MD();
 134     MD[SP->getUnit()].reset(SP->getUnit());
 135     MD[SP->getType()].reset(SP->getType());
 136     MD[SP->getFile()].reset(SP->getFile());
 137     // If we're not cloning into the same module, no need to clone the
 138     // subprogram
 139     if (!MustCloneSP)
 140       MD[SP].reset(SP);
 141   }
 142
 143   SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
 144   OldFunc->getAllMetadata(MDs);
 145   for (auto MD : MDs) {
 146     NewFunc->addMetadata(
 147         MD.first,
 148         *MapMetadata(MD.second, VMap,
 149                      ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
 150                      TypeMapper, Materializer));
 151   }
 152
 153   // When we remap instructions, we want to avoid duplicating inlined
 154   // DISubprograms, so record all subprograms we find as we duplicate
 155   // instructions and then freeze them in the MD map.
 156   // We also record information about dbg.value and dbg.declare to avoid
 157   // duplicating the types.
 158   DebugInfoFinder DIFinder;
 159
 160   // Loop over all of the basic blocks in the function, cloning them as
 161   // appropriate.  Note that we save BE this way in order to handle cloning of
 162   // recursive functions into themselves.
 163   //
 164   for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
 165        BI != BE; ++BI) {
 166     const BasicBlock &BB = *BI;
 167
 168     // Create a new basic block and copy instructions into it!
 169     BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo,
 170                                       ModuleLevelChanges ? &DIFinder : nullptr);
 171
 172     // Add basic block mapping.
 173     VMap[&BB] = CBB;
 174
 175     // It is only legal to clone a function if a block address within that
 176     // function is never referenced outside of the function.  Given that, we
 177     // want to map block addresses from the old function to block addresses in
 178     // the clone. (This is different from the generic ValueMapper
 179     // implementation, which generates an invalid blockaddress when
 180     // cloning a function.)
 181     if (BB.hasAddressTaken()) {
 182       Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
 183                                               const_cast<BasicBlock*>(&BB));
 184       VMap[OldBBAddr] = BlockAddress::get(NewFunc, CBB);
 185     }
 186
 187     // Note return instructions for the caller.
 188     if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
 189       Returns.push_back(RI);
 190   }
 191
 192   for (DISubprogram *ISP : DIFinder.subprograms())
 193     if (ISP != SP)
 194       VMap.MD()[ISP].reset(ISP);
 195
 196   for (DICompileUnit *CU : DIFinder.compile_units())
 197     VMap.MD()[CU].reset(CU);
 198
 199   for (DIType *Type : DIFinder.types())
 200     VMap.MD()[Type].reset(Type);
 201
 202   // Loop over all of the instructions in the function, fixing up operand
 203   // references as we go.  This uses VMap to do all the hard work.
 204   for (Function::iterator BB =
 205            cast<BasicBlock>(VMap[&OldFunc->front()])->getIterator(),
 206                           BE = NewFunc->end();
 207        BB != BE; ++BB)
 208     // Loop over all instructions, fixing each one as we find it...
 209     for (Instruction &II : *BB)
 210       RemapInstruction(&II, VMap,
 211                        ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
 212                        TypeMapper, Materializer);
 213 }
 214
 215 /// Return a copy of the specified function and add it to that function's
 216 /// module.  Also, any references specified in the VMap are changed to refer to
 217 /// their mapped value instead of the original one.  If any of the arguments to
 218 /// the function are in the VMap, the arguments are deleted from the resultant
 219 /// function.  The VMap is updated to include mappings from all of the
 220 /// instructions and basicblocks in the function from their old to new values.
 221 ///
 222 Function *llvm::CloneFunction(Function *F, ValueToValueMapTy &VMap,
 223                               ClonedCodeInfo *CodeInfo) {
 224   std::vector<Type*> ArgTypes;
 225
 226   // The user might be deleting arguments to the function by specifying them in
 227   // the VMap.  If so, we need to not add the arguments to the arg ty vector
 228   //
 229   for (const Argument &I : F->args())
 230     if (VMap.count(&I) == 0) // Haven't mapped the argument to anything yet?
 231       ArgTypes.push_back(I.getType());
 232
 233   // Create a new function type...
 234   FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
 235                                     ArgTypes, F->getFunctionType()->isVarArg());
 236
 237   // Create the new function...
 238   Function *NewF = Function::Create(FTy, F->getLinkage(), F->getAddressSpace(),
 239                                     F->getName(), F->getParent());
 240
 241   // Loop over the arguments, copying the names of the mapped arguments over...
 242   Function::arg_iterator DestI = NewF->arg_begin();
 243   for (const Argument & I : F->args())
 244     if (VMap.count(&I) == 0) {     // Is this argument preserved?
 245       DestI->setName(I.getName()); // Copy the name over...
 246       VMap[&I] = &*DestI++;        // Add mapping to VMap
 247     }
 248
 249   SmallVector<ReturnInst*, 8> Returns;  // Ignore returns cloned.
 250   CloneFunctionInto(NewF, F, VMap, F->getSubprogram() != nullptr, Returns, "",
 251                     CodeInfo);
 252
 253   return NewF;
 254 }
 255
 256
 257
 258 namespace {
 259   /// This is a private class used to implement CloneAndPruneFunctionInto.
 260   struct PruningFunctionCloner {
 261     Function *NewFunc;
 262     const Function *OldFunc;
 263     ValueToValueMapTy &VMap;
 264     bool ModuleLevelChanges;
 265     const char *NameSuffix;
 266     ClonedCodeInfo *CodeInfo;
 267
 268   public:
 269     PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
 270                           ValueToValueMapTy &valueMap, bool moduleLevelChanges,
 271                           const char *nameSuffix, ClonedCodeInfo *codeInfo)
 272         : NewFunc(newFunc), OldFunc(oldFunc), VMap(valueMap),
 273           ModuleLevelChanges(moduleLevelChanges), NameSuffix(nameSuffix),
 274           CodeInfo(codeInfo) {}
 275
 276     /// The specified block is found to be reachable, clone it and
 277     /// anything that it can reach.
 278     void CloneBlock(const BasicBlock *BB,
 279                     BasicBlock::const_iterator StartingInst,
 280                     std::vector<const BasicBlock*> &ToClone);
 281   };
 282 }
 283
 284 /// The specified block is found to be reachable, clone it and
 285 /// anything that it can reach.
 286 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
 287                                        BasicBlock::const_iterator StartingInst,
 288                                        std::vector<const BasicBlock*> &ToClone){
 289   WeakTrackingVH &BBEntry = VMap[BB];
 290
 291   // Have we already cloned this block?
 292   if (BBEntry) return;
 293
 294   // Nope, clone it now.
 295   BasicBlock *NewBB;
 296   BBEntry = NewBB = BasicBlock::Create(BB->getContext());
 297   if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
 298
 299   // It is only legal to clone a function if a block address within that
 300   // function is never referenced outside of the function.  Given that, we
 301   // want to map block addresses from the old function to block addresses in
 302   // the clone. (This is different from the generic ValueMapper
 303   // implementation, which generates an invalid blockaddress when
 304   // cloning a function.)
 305   //
 306   // Note that we don't need to fix the mapping for unreachable blocks;
 307   // the default mapping there is safe.
 308   if (BB->hasAddressTaken()) {
 309     Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
 310                                             const_cast<BasicBlock*>(BB));
 311     VMap[OldBBAddr] = BlockAddress::get(NewFunc, NewBB);
 312   }
 313
 314   bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
 315
 316   // Loop over all instructions, and copy them over, DCE'ing as we go.  This
 317   // loop doesn't include the terminator.
 318   for (BasicBlock::const_iterator II = StartingInst, IE = --BB->end();
 319        II != IE; ++II) {
 320
 321     Instruction *NewInst = II->clone();
 322
 323     // Eagerly remap operands to the newly cloned instruction, except for PHI
 324     // nodes for which we defer processing until we update the CFG.
 325     if (!isa<PHINode>(NewInst)) {
 326       RemapInstruction(NewInst, VMap,
 327                        ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
 328
 329       // If we can simplify this instruction to some other value, simply add
 330       // a mapping to that value rather than inserting a new instruction into
 331       // the basic block.
 332       if (Value *V =
 333               SimplifyInstruction(NewInst, BB->getModule()->getDataLayout())) {
 334         // On the off-chance that this simplifies to an instruction in the old
 335         // function, map it back into the new function.
 336         if (NewFunc != OldFunc)
 337           if (Value *MappedV = VMap.lookup(V))
 338             V = MappedV;
 339
 340         if (!NewInst->mayHaveSideEffects()) {
 341           VMap[&*II] = V;
 342           NewInst->deleteValue();
 343           continue;
 344         }
 345       }
 346     }
 347
 348     if (II->hasName())
 349       NewInst->setName(II->getName()+NameSuffix);
 350     VMap[&*II] = NewInst; // Add instruction map to value.
 351     NewBB->getInstList().push_back(NewInst);
 352     hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
 353
 354     if (CodeInfo)
 355       if (auto CS = ImmutableCallSite(&*II))
 356         if (CS.hasOperandBundles())
 357           CodeInfo->OperandBundleCallSites.push_back(NewInst);
 358
 359     if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
 360       if (isa<ConstantInt>(AI->getArraySize()))
 361         hasStaticAllocas = true;
 362       else
 363         hasDynamicAllocas = true;
 364     }
 365   }
 366
 367   // Finally, clone over the terminator.
 368   const Instruction *OldTI = BB->getTerminator();
 369   bool TerminatorDone = false;
 370   if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
 371     if (BI->isConditional()) {
 372       // If the condition was a known constant in the callee...
 373       ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
 374       // Or is a known constant in the caller...
 375       if (!Cond) {
 376         Value *V = VMap.lookup(BI->getCondition());
 377         Cond = dyn_cast_or_null<ConstantInt>(V);
 378       }
 379
 380       // Constant fold to uncond branch!
 381       if (Cond) {
 382         BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
 383         VMap[OldTI] = BranchInst::Create(Dest, NewBB);
 384         ToClone.push_back(Dest);
 385         TerminatorDone = true;
 386       }
 387     }
 388   } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
 389     // If switching on a value known constant in the caller.
 390     ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
 391     if (!Cond) { // Or known constant after constant prop in the callee...
 392       Value *V = VMap.lookup(SI->getCondition());
 393       Cond = dyn_cast_or_null<ConstantInt>(V);
 394     }
 395     if (Cond) {     // Constant fold to uncond branch!
 396       SwitchInst::ConstCaseHandle Case = *SI->findCaseValue(Cond);
 397       BasicBlock *Dest = const_cast<BasicBlock*>(Case.getCaseSuccessor());
 398       VMap[OldTI] = BranchInst::Create(Dest, NewBB);
 399       ToClone.push_back(Dest);
 400       TerminatorDone = true;
 401     }
 402   }
 403
 404   if (!TerminatorDone) {
 405     Instruction *NewInst = OldTI->clone();
 406     if (OldTI->hasName())
 407       NewInst->setName(OldTI->getName()+NameSuffix);
 408     NewBB->getInstList().push_back(NewInst);
 409     VMap[OldTI] = NewInst;             // Add instruction map to value.
 410
 411     if (CodeInfo)
 412       if (auto CS = ImmutableCallSite(OldTI))
 413         if (CS.hasOperandBundles())
 414           CodeInfo->OperandBundleCallSites.push_back(NewInst);
 415
 416     // Recursively clone any reachable successor blocks.
 417     const Instruction *TI = BB->getTerminator();
 418     for (const BasicBlock *Succ : successors(TI))
 419       ToClone.push_back(Succ);
 420   }
 421
 422   if (CodeInfo) {
 423     CodeInfo->ContainsCalls          |= hasCalls;
 424     CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
 425     CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
 426       BB != &BB->getParent()->front();
 427   }
 428 }
 429
 430 /// This works like CloneAndPruneFunctionInto, except that it does not clone the
 431 /// entire function. Instead it starts at an instruction provided by the caller
 432 /// and copies (and prunes) only the code reachable from that instruction.
 433 void llvm::CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
 434                                      const Instruction *StartingInst,
 435                                      ValueToValueMapTy &VMap,
 436                                      bool ModuleLevelChanges,
 437                                      SmallVectorImpl<ReturnInst *> &Returns,
 438                                      const char *NameSuffix,
 439                                      ClonedCodeInfo *CodeInfo) {
 440   assert(NameSuffix && "NameSuffix cannot be null!");
 441
 442   ValueMapTypeRemapper *TypeMapper = nullptr;
 443   ValueMaterializer *Materializer = nullptr;
 444
 445 #ifndef NDEBUG
 446   // If the cloning starts at the beginning of the function, verify that
 447   // the function arguments are mapped.
 448   if (!StartingInst)
 449     for (const Argument &II : OldFunc->args())
 450       assert(VMap.count(&II) && "No mapping from source argument specified!");
 451 #endif
 452
 453   PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
 454                             NameSuffix, CodeInfo);
 455   const BasicBlock *StartingBB;
 456   if (StartingInst)
 457     StartingBB = StartingInst->getParent();
 458   else {
 459     StartingBB = &OldFunc->getEntryBlock();
 460     StartingInst = &StartingBB->front();
 461   }
 462
 463   // Clone the entry block, and anything recursively reachable from it.
 464   std::vector<const BasicBlock*> CloneWorklist;
 465   PFC.CloneBlock(StartingBB, StartingInst->getIterator(), CloneWorklist);
 466   while (!CloneWorklist.empty()) {
 467     const BasicBlock *BB = CloneWorklist.back();
 468     CloneWorklist.pop_back();
 469     PFC.CloneBlock(BB, BB->begin(), CloneWorklist);
 470   }
 471
 472   // Loop over all of the basic blocks in the old function.  If the block was
 473   // reachable, we have cloned it and the old block is now in the value map:
 474   // insert it into the new function in the right order.  If not, ignore it.
 475   //
 476   // Defer PHI resolution until rest of function is resolved.
 477   SmallVector<const PHINode*, 16> PHIToResolve;
 478   for (const BasicBlock &BI : *OldFunc) {
 479     Value *V = VMap.lookup(&BI);
 480     BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
 481     if (!NewBB) continue;  // Dead block.
 482
 483     // Add the new block to the new function.
 484     NewFunc->getBasicBlockList().push_back(NewBB);
 485
 486     // Handle PHI nodes specially, as we have to remove references to dead
 487     // blocks.
 488     for (const PHINode &PN : BI.phis()) {
 489       // PHI nodes may have been remapped to non-PHI nodes by the caller or
 490       // during the cloning process.
 491       if (isa<PHINode>(VMap[&PN]))
 492         PHIToResolve.push_back(&PN);
 493       else
 494         break;
 495     }
 496
 497     // Finally, remap the terminator instructions, as those can't be remapped
 498     // until all BBs are mapped.
 499     RemapInstruction(NewBB->getTerminator(), VMap,
 500                      ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
 501                      TypeMapper, Materializer);
 502   }
 503
 504   // Defer PHI resolution until rest of function is resolved, PHI resolution
 505   // requires the CFG to be up-to-date.
 506   for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
 507     const PHINode *OPN = PHIToResolve[phino];
 508     unsigned NumPreds = OPN->getNumIncomingValues();
 509     const BasicBlock *OldBB = OPN->getParent();
 510     BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);
 511
 512     // Map operands for blocks that are live and remove operands for blocks
 513     // that are dead.
 514     for (; phino != PHIToResolve.size() &&
 515          PHIToResolve[phino]->getParent() == OldBB; ++phino) {
 516       OPN = PHIToResolve[phino];
 517       PHINode *PN = cast<PHINode>(VMap[OPN]);
 518       for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
 519         Value *V = VMap.lookup(PN->getIncomingBlock(pred));
 520         if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
 521           Value *InVal = MapValue(PN->getIncomingValue(pred),
 522                                   VMap,
 523                         ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
 524           assert(InVal && "Unknown input value?");
 525           PN->setIncomingValue(pred, InVal);
 526           PN->setIncomingBlock(pred, MappedBlock);
 527         } else {
 528           PN->removeIncomingValue(pred, false);
 529           --pred;  // Revisit the next entry.
 530           --e;
 531         }
 532       }
 533     }
 534
 535     // The loop above has removed PHI entries for those blocks that are dead
 536     // and has updated others.  However, if a block is live (i.e. copied over)
 537     // but its terminator has been changed to not go to this block, then our
 538     // phi nodes will have invalid entries.  Update the PHI nodes in this
 539     // case.
 540     PHINode *PN = cast<PHINode>(NewBB->begin());
 541     NumPreds = pred_size(NewBB);
 542     if (NumPreds != PN->getNumIncomingValues()) {
 543       assert(NumPreds < PN->getNumIncomingValues());
 544       // Count how many times each predecessor comes to this block.
 545       std::map<BasicBlock*, unsigned> PredCount;
 546       for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
 547            PI != E; ++PI)
 548         --PredCount[*PI];
 549
 550       // Figure out how many entries to remove from each PHI.
 551       for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
 552         ++PredCount[PN->getIncomingBlock(i)];
 553
 554       // At this point, the excess predecessor entries are positive in the
 555       // map.  Loop over all of the PHIs and remove excess predecessor
 556       // entries.
 557       BasicBlock::iterator I = NewBB->begin();
 558       for (; (PN = dyn_cast<PHINode>(I)); ++I) {
 559         for (const auto &PCI : PredCount) {
 560           BasicBlock *Pred = PCI.first;
 561           for (unsigned NumToRemove = PCI.second; NumToRemove; --NumToRemove)
 562             PN->removeIncomingValue(Pred, false);
 563         }
 564       }
 565     }
 566
 567     // If the loops above have made these phi nodes have 0 or 1 operand,
 568     // replace them with undef or the input value.  We must do this for
 569     // correctness, because 0-operand phis are not valid.
 570     PN = cast<PHINode>(NewBB->begin());
 571     if (PN->getNumIncomingValues() == 0) {
 572       BasicBlock::iterator I = NewBB->begin();
 573       BasicBlock::const_iterator OldI = OldBB->begin();
 574       while ((PN = dyn_cast<PHINode>(I++))) {
 575         Value *NV = UndefValue::get(PN->getType());
 576         PN->replaceAllUsesWith(NV);
 577         assert(VMap[&*OldI] == PN && "VMap mismatch");
 578         VMap[&*OldI] = NV;
 579         PN->eraseFromParent();
 580         ++OldI;
 581       }
 582     }
 583   }
 584
 585   // Make a second pass over the PHINodes now that all of them have been
 586   // remapped into the new function, simplifying the PHINode and performing any
 587   // recursive simplifications exposed. This will transparently update the
 588   // WeakTrackingVH in the VMap. Notably, we rely on that so that if we coalesce
 589   // two PHINodes, the iteration over the old PHIs remains valid, and the
 590   // mapping will just map us to the new node (which may not even be a PHI
 591   // node).
 592   const DataLayout &DL = NewFunc->getParent()->getDataLayout();
 593   SmallSetVector<const Value *, 8> Worklist;
 594   for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
 595     if (isa<PHINode>(VMap[PHIToResolve[Idx]]))
 596       Worklist.insert(PHIToResolve[Idx]);
 597
 598   // Note that we must test the size on each iteration, the worklist can grow.
 599   for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) {
 600     const Value *OrigV = Worklist[Idx];
 601     auto *I = dyn_cast_or_null<Instruction>(VMap.lookup(OrigV));
 602     if (!I)
 603       continue;
 604
 605     // Skip over non-intrinsic callsites, we don't want to remove any nodes from
 606     // the CGSCC.
 607     CallSite CS = CallSite(I);
 608     if (CS && CS.getCalledFunction() && !CS.getCalledFunction()->isIntrinsic())
 609       continue;
 610
 611     // See if this instruction simplifies.
 612     Value *SimpleV = SimplifyInstruction(I, DL);
 613     if (!SimpleV)
 614       continue;
 615
 616     // Stash away all the uses of the old instruction so we can check them for
 617     // recursive simplifications after a RAUW. This is cheaper than checking all
 618     // uses of To on the recursive step in most cases.
 619     for (const User *U : OrigV->users())
 620       Worklist.insert(cast<Instruction>(U));
 621
 622     // Replace the instruction with its simplified value.
 623     I->replaceAllUsesWith(SimpleV);
 624
 625     // If the original instruction had no side effects, remove it.
 626     if (isInstructionTriviallyDead(I))
 627       I->eraseFromParent();
 628     else
 629       VMap[OrigV] = I;
 630   }
 631
 632   // Now that the inlined function body has been fully constructed, go through
 633   // and zap unconditional fall-through branches. This happens all the time when
 634   // specializing code: code specialization turns conditional branches into
 635   // uncond branches, and this code folds them.
 636   Function::iterator Begin = cast<BasicBlock>(VMap[StartingBB])->getIterator();
 637   Function::iterator I = Begin;
 638   while (I != NewFunc->end()) {
 639     // We need to simplify conditional branches and switches with a constant
 640     // operand. We try to prune these out when cloning, but if the
 641     // simplification required looking through PHI nodes, those are only
 642     // available after forming the full basic block. That may leave some here,
 643     // and we still want to prune the dead code as early as possible.
 644     //
 645     // Do the folding before we check if the block is dead since we want code
 646     // like
 647     //  bb:
 648     //    br i1 undef, label %bb, label %bb
 649     // to be simplified to
 650     //  bb:
 651     //    br label %bb
 652     // before we call I->getSinglePredecessor().
 653     ConstantFoldTerminator(&*I);
 654
 655     // Check if this block has become dead during inlining or other
 656     // simplifications. Note that the first block will appear dead, as it has
 657     // not yet been wired up properly.
 658     if (I != Begin && (pred_begin(&*I) == pred_end(&*I) ||
 659                        I->getSinglePredecessor() == &*I)) {
 660       BasicBlock *DeadBB = &*I++;
 661       DeleteDeadBlock(DeadBB);
 662       continue;
 663     }
 664
 665     BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
 666     if (!BI || BI->isConditional()) { ++I; continue; }
 667
 668     BasicBlock *Dest = BI->getSuccessor(0);
 669     if (!Dest->getSinglePredecessor()) {
 670       ++I; continue;
 671     }
 672
 673     // We shouldn't be able to get single-entry PHI nodes here, as instsimplify
 674     // above should have zapped all of them..
 675     assert(!isa<PHINode>(Dest->begin()));
 676
 677     // We know all single-entry PHI nodes in the inlined function have been
 678     // removed, so we just need to splice the blocks.
 679     BI->eraseFromParent();
 680
 681     // Make all PHI nodes that referred to Dest now refer to I as their source.
 682     Dest->replaceAllUsesWith(&*I);
 683
 684     // Move all the instructions in the succ to the pred.
 685     I->getInstList().splice(I->end(), Dest->getInstList());
 686
 687     // Remove the dest block.
 688     Dest->eraseFromParent();
 689
 690     // Do not increment I, iteratively merge all things this block branches to.
 691   }
 692
 693   // Make a final pass over the basic blocks from the old function to gather
 694   // any return instructions which survived folding. We have to do this here
 695   // because we can iteratively remove and merge returns above.
 696   for (Function::iterator I = cast<BasicBlock>(VMap[StartingBB])->getIterator(),
 697                           E = NewFunc->end();
 698        I != E; ++I)
 699     if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
 700       Returns.push_back(RI);
 701 }
 702
 703
 704 /// This works exactly like CloneFunctionInto,
 705 /// except that it does some simple constant prop and DCE on the fly.  The
 706 /// effect of this is to copy significantly less code in cases where (for
 707 /// example) a function call with constant arguments is inlined, and those
 708 /// constant arguments cause a significant amount of code in the callee to be
 709 /// dead.  Since this doesn't produce an exact copy of the input, it can't be
 710 /// used for things like CloneFunction or CloneModule.
 711 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
 712                                      ValueToValueMapTy &VMap,
 713                                      bool ModuleLevelChanges,
 714                                      SmallVectorImpl<ReturnInst*> &Returns,
 715                                      const char *NameSuffix,
 716                                      ClonedCodeInfo *CodeInfo,
 717                                      Instruction *TheCall) {
 718   CloneAndPruneIntoFromInst(NewFunc, OldFunc, &OldFunc->front().front(), VMap,
 719                             ModuleLevelChanges, Returns, NameSuffix, CodeInfo);
 720 }
 721
 722 /// Remaps instructions in \p Blocks using the mapping in \p VMap.
 723 void llvm::remapInstructionsInBlocks(
 724     const SmallVectorImpl<BasicBlock *> &Blocks, ValueToValueMapTy &VMap) {
 725   // Rewrite the code to refer to itself.
 726   for (auto *BB : Blocks)
 727     for (auto &Inst : *BB)
 728       RemapInstruction(&Inst, VMap,
 729                        RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
 730 }
 731
 732 /// Clones a loop \p OrigLoop.  Returns the loop and the blocks in \p
 733 /// Blocks.
 734 ///
 735 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block
 736 /// \p LoopDomBB.  Insert the new blocks before block specified in \p Before.
 737 Loop *llvm::cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
 738                                    Loop *OrigLoop, ValueToValueMapTy &VMap,
 739                                    const Twine &NameSuffix, LoopInfo *LI,
 740                                    DominatorTree *DT,
 741                                    SmallVectorImpl<BasicBlock *> &Blocks) {
 742   Function *F = OrigLoop->getHeader()->getParent();
 743   Loop *ParentLoop = OrigLoop->getParentLoop();
 744   DenseMap<Loop *, Loop *> LMap;
 745
 746   Loop *NewLoop = LI->AllocateLoop();
 747   LMap[OrigLoop] = NewLoop;
 748   if (ParentLoop)
 749     ParentLoop->addChildLoop(NewLoop);
 750   else
 751     LI->addTopLevelLoop(NewLoop);
 752
 753   BasicBlock *OrigPH = OrigLoop->getLoopPreheader();
 754   assert(OrigPH && "No preheader");
 755   BasicBlock *NewPH = CloneBasicBlock(OrigPH, VMap, NameSuffix, F);
 756   // To rename the loop PHIs.
 757   VMap[OrigPH] = NewPH;
 758   Blocks.push_back(NewPH);
 759
 760   // Update LoopInfo.
 761   if (ParentLoop)
 762     ParentLoop->addBasicBlockToLoop(NewPH, *LI);
 763
 764   // Update DominatorTree.
 765   DT->addNewBlock(NewPH, LoopDomBB);
 766
 767   for (Loop *CurLoop : OrigLoop->getLoopsInPreorder()) {
 768     Loop *&NewLoop = LMap[CurLoop];
 769     if (!NewLoop) {
 770       NewLoop = LI->AllocateLoop();
 771
 772       // Establish the parent/child relationship.
 773       Loop *OrigParent = CurLoop->getParentLoop();
 774       assert(OrigParent && "Could not find the original parent loop");
 775       Loop *NewParentLoop = LMap[OrigParent];
 776       assert(NewParentLoop && "Could not find the new parent loop");
 777
 778       NewParentLoop->addChildLoop(NewLoop);
 779     }
 780   }
 781
 782   for (BasicBlock *BB : OrigLoop->getBlocks()) {
 783     Loop *CurLoop = LI->getLoopFor(BB);
 784     Loop *&NewLoop = LMap[CurLoop];
 785     assert(NewLoop && "Expecting new loop to be allocated");
 786
 787     BasicBlock *NewBB = CloneBasicBlock(BB, VMap, NameSuffix, F);
 788     VMap[BB] = NewBB;
 789
 790     // Update LoopInfo.
 791     NewLoop->addBasicBlockToLoop(NewBB, *LI);
 792     if (BB == CurLoop->getHeader())
 793       NewLoop->moveToHeader(NewBB);
 794
 795     // Add DominatorTree node. After seeing all blocks, update to correct
 796     // IDom.
 797     DT->addNewBlock(NewBB, NewPH);
 798
 799     Blocks.push_back(NewBB);
 800   }
 801
 802   for (BasicBlock *BB : OrigLoop->getBlocks()) {
 803     // Update DominatorTree.
 804     BasicBlock *IDomBB = DT->getNode(BB)->getIDom()->getBlock();
 805     DT->changeImmediateDominator(cast<BasicBlock>(VMap[BB]),
 806                                  cast<BasicBlock>(VMap[IDomBB]));
 807   }
 808
 809   // Move them physically from the end of the block list.
 810   F->getBasicBlockList().splice(Before->getIterator(), F->getBasicBlockList(),
 811                                 NewPH);
 812   F->getBasicBlockList().splice(Before->getIterator(), F->getBasicBlockList(),
 813                                 NewLoop->getHeader()->getIterator(), F->end());
 814
 815   return NewLoop;
 816 }
 817
 818 /// Duplicate non-Phi instructions from the beginning of block up to
 819 /// StopAt instruction into a split block between BB and its predecessor.
 820 BasicBlock *llvm::DuplicateInstructionsInSplitBetween(
 821     BasicBlock *BB, BasicBlock *PredBB, Instruction *StopAt,
 822     ValueToValueMapTy &ValueMapping, DomTreeUpdater &DTU) {
 823
 824   assert(count(successors(PredBB), BB) == 1 &&
 825          "There must be a single edge between PredBB and BB!");
 826   // We are going to have to map operands from the original BB block to the new
 827   // copy of the block 'NewBB'.  If there are PHI nodes in BB, evaluate them to
 828   // account for entry from PredBB.
 829   BasicBlock::iterator BI = BB->begin();
 830   for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
 831     ValueMapping[PN] = PN->getIncomingValueForBlock(PredBB);
 832
 833   BasicBlock *NewBB = SplitEdge(PredBB, BB);
 834   NewBB->setName(PredBB->getName() + ".split");
 835   Instruction *NewTerm = NewBB->getTerminator();
 836
 837   // FIXME: SplitEdge does not yet take a DTU, so we include the split edge
 838   //        in the update set here.
 839   DTU.applyUpdates({{DominatorTree::Delete, PredBB, BB},
 840                     {DominatorTree::Insert, PredBB, NewBB},
 841                     {DominatorTree::Insert, NewBB, BB}});
 842
 843   // Clone the non-phi instructions of BB into NewBB, keeping track of the
 844   // mapping and using it to remap operands in the cloned instructions.
 845   // Stop once we see the terminator too. This covers the case where BB's
 846   // terminator gets replaced and StopAt == BB's terminator.
 847   for (; StopAt != &*BI && BB->getTerminator() != &*BI; ++BI) {
 848     Instruction *New = BI->clone();
 849     New->setName(BI->getName());
 850     New->insertBefore(NewTerm);
 851     ValueMapping[&*BI] = New;
 852
 853     // Remap operands to patch up intra-block references.
 854     for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
 855       if (Instruction *Inst = dyn_cast<Instruction>(New->getOperand(i))) {
 856         auto I = ValueMapping.find(Inst);
 857         if (I != ValueMapping.end())
 858           New->setOperand(i, I->second);
 859       }
 860   }
 861
 862   return NewBB;
 863 }