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 } 864