CloneFunction.cpp revision 333a94765a78e0d7057059c6cb05dba2330eddf0
1//===- CloneFunction.cpp - Clone a function into another function ---------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the CloneFunctionInto interface, which is used as the 11// low-level function cloner. This is used by the CloneFunction and function 12// inliner to do the dirty work of copying the body of a function around. 13// 14//===----------------------------------------------------------------------===// 15 16#include "llvm/Transforms/Utils/Cloning.h" 17#include "llvm/Constants.h" 18#include "llvm/DerivedTypes.h" 19#include "llvm/Instructions.h" 20#include "llvm/IntrinsicInst.h" 21#include "llvm/GlobalVariable.h" 22#include "llvm/Function.h" 23#include "llvm/LLVMContext.h" 24#include "llvm/Metadata.h" 25#include "llvm/Support/CFG.h" 26#include "ValueMapper.h" 27#include "llvm/Analysis/ConstantFolding.h" 28#include "llvm/Analysis/DebugInfo.h" 29#include "llvm/ADT/SmallVector.h" 30#include <map> 31using namespace llvm; 32 33// CloneBasicBlock - See comments in Cloning.h 34BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB, 35 ValueToValueMapTy &VMap, 36 const Twine &NameSuffix, Function *F, 37 ClonedCodeInfo *CodeInfo) { 38 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F); 39 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 40 41 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 42 43 // Loop over all instructions, and copy them over. 44 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); 45 II != IE; ++II) { 46 Instruction *NewInst = II->clone(); 47 if (II->hasName()) 48 NewInst->setName(II->getName()+NameSuffix); 49 NewBB->getInstList().push_back(NewInst); 50 VMap[II] = NewInst; // Add instruction map to value. 51 52 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II)); 53 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 54 if (isa<ConstantInt>(AI->getArraySize())) 55 hasStaticAllocas = true; 56 else 57 hasDynamicAllocas = true; 58 } 59 } 60 61 if (CodeInfo) { 62 CodeInfo->ContainsCalls |= hasCalls; 63 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator()); 64 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 65 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 66 BB != &BB->getParent()->getEntryBlock(); 67 } 68 return NewBB; 69} 70 71// Clone OldFunc into NewFunc, transforming the old arguments into references to 72// ArgMap values. 73// 74void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc, 75 ValueToValueMapTy &VMap, 76 SmallVectorImpl<ReturnInst*> &Returns, 77 const char *NameSuffix, ClonedCodeInfo *CodeInfo) { 78 assert(NameSuffix && "NameSuffix cannot be null!"); 79 80#ifndef NDEBUG 81 for (Function::const_arg_iterator I = OldFunc->arg_begin(), 82 E = OldFunc->arg_end(); I != E; ++I) 83 assert(VMap.count(I) && "No mapping from source argument specified!"); 84#endif 85 86 // Clone any attributes. 87 if (NewFunc->arg_size() == OldFunc->arg_size()) 88 NewFunc->copyAttributesFrom(OldFunc); 89 else { 90 //Some arguments were deleted with the VMap. Copy arguments one by one 91 for (Function::const_arg_iterator I = OldFunc->arg_begin(), 92 E = OldFunc->arg_end(); I != E; ++I) 93 if (Argument* Anew = dyn_cast<Argument>(VMap[I])) 94 Anew->addAttr( OldFunc->getAttributes() 95 .getParamAttributes(I->getArgNo() + 1)); 96 NewFunc->setAttributes(NewFunc->getAttributes() 97 .addAttr(0, OldFunc->getAttributes() 98 .getRetAttributes())); 99 NewFunc->setAttributes(NewFunc->getAttributes() 100 .addAttr(~0, OldFunc->getAttributes() 101 .getFnAttributes())); 102 103 } 104 105 // Loop over all of the basic blocks in the function, cloning them as 106 // appropriate. Note that we save BE this way in order to handle cloning of 107 // recursive functions into themselves. 108 // 109 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 110 BI != BE; ++BI) { 111 const BasicBlock &BB = *BI; 112 113 // Create a new basic block and copy instructions into it! 114 BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, 115 CodeInfo); 116 VMap[&BB] = CBB; // Add basic block mapping. 117 118 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator())) 119 Returns.push_back(RI); 120 } 121 122 // Loop over all of the instructions in the function, fixing up operand 123 // references as we go. This uses VMap to do all the hard work. 124 // 125 for (Function::iterator BB = cast<BasicBlock>(VMap[OldFunc->begin()]), 126 BE = NewFunc->end(); BB != BE; ++BB) 127 // Loop over all instructions, fixing each one as we find it... 128 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II) 129 RemapInstruction(II, VMap); 130} 131 132/// CloneFunction - Return a copy of the specified function, but without 133/// embedding the function into another module. Also, any references specified 134/// in the VMap are changed to refer to their mapped value instead of the 135/// original one. If any of the arguments to the function are in the VMap, 136/// the arguments are deleted from the resultant function. The VMap is 137/// updated to include mappings from all of the instructions and basicblocks in 138/// the function from their old to new values. 139/// 140Function *llvm::CloneFunction(const Function *F, 141 ValueToValueMapTy &VMap, 142 ClonedCodeInfo *CodeInfo) { 143 std::vector<const Type*> ArgTypes; 144 145 // The user might be deleting arguments to the function by specifying them in 146 // the VMap. If so, we need to not add the arguments to the arg ty vector 147 // 148 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 149 I != E; ++I) 150 if (VMap.count(I) == 0) // Haven't mapped the argument to anything yet? 151 ArgTypes.push_back(I->getType()); 152 153 // Create a new function type... 154 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(), 155 ArgTypes, F->getFunctionType()->isVarArg()); 156 157 // Create the new function... 158 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName()); 159 160 // Loop over the arguments, copying the names of the mapped arguments over... 161 Function::arg_iterator DestI = NewF->arg_begin(); 162 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 163 I != E; ++I) 164 if (VMap.count(I) == 0) { // Is this argument preserved? 165 DestI->setName(I->getName()); // Copy the name over... 166 VMap[I] = DestI++; // Add mapping to VMap 167 } 168 169 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned. 170 CloneFunctionInto(NewF, F, VMap, Returns, "", CodeInfo); 171 return NewF; 172} 173 174 175 176namespace { 177 /// PruningFunctionCloner - This class is a private class used to implement 178 /// the CloneAndPruneFunctionInto method. 179 struct PruningFunctionCloner { 180 Function *NewFunc; 181 const Function *OldFunc; 182 ValueToValueMapTy &VMap; 183 SmallVectorImpl<ReturnInst*> &Returns; 184 const char *NameSuffix; 185 ClonedCodeInfo *CodeInfo; 186 const TargetData *TD; 187 public: 188 PruningFunctionCloner(Function *newFunc, const Function *oldFunc, 189 ValueToValueMapTy &valueMap, 190 SmallVectorImpl<ReturnInst*> &returns, 191 const char *nameSuffix, 192 ClonedCodeInfo *codeInfo, 193 const TargetData *td) 194 : NewFunc(newFunc), OldFunc(oldFunc), VMap(valueMap), Returns(returns), 195 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) { 196 } 197 198 /// CloneBlock - The specified block is found to be reachable, clone it and 199 /// anything that it can reach. 200 void CloneBlock(const BasicBlock *BB, 201 std::vector<const BasicBlock*> &ToClone); 202 203 public: 204 /// ConstantFoldMappedInstruction - Constant fold the specified instruction, 205 /// mapping its operands through VMap if they are available. 206 Constant *ConstantFoldMappedInstruction(const Instruction *I); 207 }; 208} 209 210/// CloneBlock - The specified block is found to be reachable, clone it and 211/// anything that it can reach. 212void PruningFunctionCloner::CloneBlock(const BasicBlock *BB, 213 std::vector<const BasicBlock*> &ToClone){ 214 Value *&BBEntry = VMap[BB]; 215 216 // Have we already cloned this block? 217 if (BBEntry) return; 218 219 // Nope, clone it now. 220 BasicBlock *NewBB; 221 BBEntry = NewBB = BasicBlock::Create(BB->getContext()); 222 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 223 224 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 225 226 // Loop over all instructions, and copy them over, DCE'ing as we go. This 227 // loop doesn't include the terminator. 228 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end(); 229 II != IE; ++II) { 230 // If this instruction constant folds, don't bother cloning the instruction, 231 // instead, just add the constant to the value map. 232 if (Constant *C = ConstantFoldMappedInstruction(II)) { 233 VMap[II] = C; 234 continue; 235 } 236 237 Instruction *NewInst = II->clone(); 238 if (II->hasName()) 239 NewInst->setName(II->getName()+NameSuffix); 240 NewBB->getInstList().push_back(NewInst); 241 VMap[II] = NewInst; // Add instruction map to value. 242 243 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II)); 244 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 245 if (isa<ConstantInt>(AI->getArraySize())) 246 hasStaticAllocas = true; 247 else 248 hasDynamicAllocas = true; 249 } 250 } 251 252 // Finally, clone over the terminator. 253 const TerminatorInst *OldTI = BB->getTerminator(); 254 bool TerminatorDone = false; 255 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) { 256 if (BI->isConditional()) { 257 // If the condition was a known constant in the callee... 258 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition()); 259 // Or is a known constant in the caller... 260 if (Cond == 0) 261 Cond = dyn_cast_or_null<ConstantInt>(VMap[BI->getCondition()]); 262 263 // Constant fold to uncond branch! 264 if (Cond) { 265 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue()); 266 VMap[OldTI] = BranchInst::Create(Dest, NewBB); 267 ToClone.push_back(Dest); 268 TerminatorDone = true; 269 } 270 } 271 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) { 272 // If switching on a value known constant in the caller. 273 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition()); 274 if (Cond == 0) // Or known constant after constant prop in the callee... 275 Cond = dyn_cast_or_null<ConstantInt>(VMap[SI->getCondition()]); 276 if (Cond) { // Constant fold to uncond branch! 277 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond)); 278 VMap[OldTI] = BranchInst::Create(Dest, NewBB); 279 ToClone.push_back(Dest); 280 TerminatorDone = true; 281 } 282 } 283 284 if (!TerminatorDone) { 285 Instruction *NewInst = OldTI->clone(); 286 if (OldTI->hasName()) 287 NewInst->setName(OldTI->getName()+NameSuffix); 288 NewBB->getInstList().push_back(NewInst); 289 VMap[OldTI] = NewInst; // Add instruction map to value. 290 291 // Recursively clone any reachable successor blocks. 292 const TerminatorInst *TI = BB->getTerminator(); 293 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 294 ToClone.push_back(TI->getSuccessor(i)); 295 } 296 297 if (CodeInfo) { 298 CodeInfo->ContainsCalls |= hasCalls; 299 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI); 300 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 301 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 302 BB != &BB->getParent()->front(); 303 } 304 305 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator())) 306 Returns.push_back(RI); 307} 308 309/// ConstantFoldMappedInstruction - Constant fold the specified instruction, 310/// mapping its operands through VMap if they are available. 311Constant *PruningFunctionCloner:: 312ConstantFoldMappedInstruction(const Instruction *I) { 313 SmallVector<Constant*, 8> Ops; 314 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 315 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i), 316 VMap))) 317 Ops.push_back(Op); 318 else 319 return 0; // All operands not constant! 320 321 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 322 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1], 323 TD); 324 325 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) 326 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) 327 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr) 328 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) 329 if (GV->isConstant() && GV->hasDefinitiveInitializer()) 330 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), 331 CE); 332 333 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0], 334 Ops.size(), TD); 335} 336 337static DebugLoc 338UpdateInlinedAtInfo(const DebugLoc &InsnDL, const DebugLoc &TheCallDL, 339 LLVMContext &Ctx) { 340 DebugLoc NewLoc = TheCallDL; 341 if (MDNode *IA = InsnDL.getInlinedAt(Ctx)) 342 NewLoc = UpdateInlinedAtInfo(DebugLoc::getFromDILocation(IA), TheCallDL, 343 Ctx); 344 345 return DebugLoc::get(InsnDL.getLine(), InsnDL.getCol(), 346 InsnDL.getScope(Ctx), NewLoc.getAsMDNode(Ctx)); 347} 348 349/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto, 350/// except that it does some simple constant prop and DCE on the fly. The 351/// effect of this is to copy significantly less code in cases where (for 352/// example) a function call with constant arguments is inlined, and those 353/// constant arguments cause a significant amount of code in the callee to be 354/// dead. Since this doesn't produce an exact copy of the input, it can't be 355/// used for things like CloneFunction or CloneModule. 356void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 357 ValueToValueMapTy &VMap, 358 SmallVectorImpl<ReturnInst*> &Returns, 359 const char *NameSuffix, 360 ClonedCodeInfo *CodeInfo, 361 const TargetData *TD, 362 Instruction *TheCall) { 363 assert(NameSuffix && "NameSuffix cannot be null!"); 364 365#ifndef NDEBUG 366 for (Function::const_arg_iterator II = OldFunc->arg_begin(), 367 E = OldFunc->arg_end(); II != E; ++II) 368 assert(VMap.count(II) && "No mapping from source argument specified!"); 369#endif 370 371 PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, Returns, 372 NameSuffix, CodeInfo, TD); 373 374 // Clone the entry block, and anything recursively reachable from it. 375 std::vector<const BasicBlock*> CloneWorklist; 376 CloneWorklist.push_back(&OldFunc->getEntryBlock()); 377 while (!CloneWorklist.empty()) { 378 const BasicBlock *BB = CloneWorklist.back(); 379 CloneWorklist.pop_back(); 380 PFC.CloneBlock(BB, CloneWorklist); 381 } 382 383 // Loop over all of the basic blocks in the old function. If the block was 384 // reachable, we have cloned it and the old block is now in the value map: 385 // insert it into the new function in the right order. If not, ignore it. 386 // 387 // Defer PHI resolution until rest of function is resolved. 388 SmallVector<const PHINode*, 16> PHIToResolve; 389 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 390 BI != BE; ++BI) { 391 BasicBlock *NewBB = cast_or_null<BasicBlock>(VMap[BI]); 392 if (NewBB == 0) continue; // Dead block. 393 394 // Add the new block to the new function. 395 NewFunc->getBasicBlockList().push_back(NewBB); 396 397 // Loop over all of the instructions in the block, fixing up operand 398 // references as we go. This uses VMap to do all the hard work. 399 // 400 BasicBlock::iterator I = NewBB->begin(); 401 402 DebugLoc TheCallDL; 403 if (TheCall) 404 TheCallDL = TheCall->getDebugLoc(); 405 406 // Handle PHI nodes specially, as we have to remove references to dead 407 // blocks. 408 if (PHINode *PN = dyn_cast<PHINode>(I)) { 409 // Skip over all PHI nodes, remembering them for later. 410 BasicBlock::const_iterator OldI = BI->begin(); 411 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) { 412 if (I->hasMetadata()) { 413 if (!TheCallDL.isUnknown()) { 414 DebugLoc IDL = I->getDebugLoc(); 415 if (!IDL.isUnknown()) { 416 DebugLoc NewDL = UpdateInlinedAtInfo(IDL, TheCallDL, 417 I->getContext()); 418 I->setDebugLoc(NewDL); 419 } 420 } else { 421 // The cloned instruction has dbg info but the call instruction 422 // does not have dbg info. Remove dbg info from cloned instruction. 423 I->setDebugLoc(DebugLoc()); 424 } 425 } 426 PHIToResolve.push_back(cast<PHINode>(OldI)); 427 } 428 } 429 430 // FIXME: 431 // FIXME: 432 // FIXME: Unclone all this metadata stuff. 433 // FIXME: 434 // FIXME: 435 436 // Otherwise, remap the rest of the instructions normally. 437 for (; I != NewBB->end(); ++I) { 438 if (I->hasMetadata()) { 439 if (!TheCallDL.isUnknown()) { 440 DebugLoc IDL = I->getDebugLoc(); 441 if (!IDL.isUnknown()) { 442 DebugLoc NewDL = UpdateInlinedAtInfo(IDL, TheCallDL, 443 I->getContext()); 444 I->setDebugLoc(NewDL); 445 } 446 } else { 447 // The cloned instruction has dbg info but the call instruction 448 // does not have dbg info. Remove dbg info from cloned instruction. 449 I->setDebugLoc(DebugLoc()); 450 } 451 } 452 RemapInstruction(I, VMap); 453 } 454 } 455 456 // Defer PHI resolution until rest of function is resolved, PHI resolution 457 // requires the CFG to be up-to-date. 458 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) { 459 const PHINode *OPN = PHIToResolve[phino]; 460 unsigned NumPreds = OPN->getNumIncomingValues(); 461 const BasicBlock *OldBB = OPN->getParent(); 462 BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]); 463 464 // Map operands for blocks that are live and remove operands for blocks 465 // that are dead. 466 for (; phino != PHIToResolve.size() && 467 PHIToResolve[phino]->getParent() == OldBB; ++phino) { 468 OPN = PHIToResolve[phino]; 469 PHINode *PN = cast<PHINode>(VMap[OPN]); 470 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) { 471 if (BasicBlock *MappedBlock = 472 cast_or_null<BasicBlock>(VMap[PN->getIncomingBlock(pred)])) { 473 Value *InVal = MapValue(PN->getIncomingValue(pred), 474 VMap); 475 assert(InVal && "Unknown input value?"); 476 PN->setIncomingValue(pred, InVal); 477 PN->setIncomingBlock(pred, MappedBlock); 478 } else { 479 PN->removeIncomingValue(pred, false); 480 --pred, --e; // Revisit the next entry. 481 } 482 } 483 } 484 485 // The loop above has removed PHI entries for those blocks that are dead 486 // and has updated others. However, if a block is live (i.e. copied over) 487 // but its terminator has been changed to not go to this block, then our 488 // phi nodes will have invalid entries. Update the PHI nodes in this 489 // case. 490 PHINode *PN = cast<PHINode>(NewBB->begin()); 491 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB)); 492 if (NumPreds != PN->getNumIncomingValues()) { 493 assert(NumPreds < PN->getNumIncomingValues()); 494 // Count how many times each predecessor comes to this block. 495 std::map<BasicBlock*, unsigned> PredCount; 496 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB); 497 PI != E; ++PI) 498 --PredCount[*PI]; 499 500 // Figure out how many entries to remove from each PHI. 501 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 502 ++PredCount[PN->getIncomingBlock(i)]; 503 504 // At this point, the excess predecessor entries are positive in the 505 // map. Loop over all of the PHIs and remove excess predecessor 506 // entries. 507 BasicBlock::iterator I = NewBB->begin(); 508 for (; (PN = dyn_cast<PHINode>(I)); ++I) { 509 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(), 510 E = PredCount.end(); PCI != E; ++PCI) { 511 BasicBlock *Pred = PCI->first; 512 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove) 513 PN->removeIncomingValue(Pred, false); 514 } 515 } 516 } 517 518 // If the loops above have made these phi nodes have 0 or 1 operand, 519 // replace them with undef or the input value. We must do this for 520 // correctness, because 0-operand phis are not valid. 521 PN = cast<PHINode>(NewBB->begin()); 522 if (PN->getNumIncomingValues() == 0) { 523 BasicBlock::iterator I = NewBB->begin(); 524 BasicBlock::const_iterator OldI = OldBB->begin(); 525 while ((PN = dyn_cast<PHINode>(I++))) { 526 Value *NV = UndefValue::get(PN->getType()); 527 PN->replaceAllUsesWith(NV); 528 assert(VMap[OldI] == PN && "VMap mismatch"); 529 VMap[OldI] = NV; 530 PN->eraseFromParent(); 531 ++OldI; 532 } 533 } 534 // NOTE: We cannot eliminate single entry phi nodes here, because of 535 // VMap. Single entry phi nodes can have multiple VMap entries 536 // pointing at them. Thus, deleting one would require scanning the VMap 537 // to update any entries in it that would require that. This would be 538 // really slow. 539 } 540 541 // Now that the inlined function body has been fully constructed, go through 542 // and zap unconditional fall-through branches. This happen all the time when 543 // specializing code: code specialization turns conditional branches into 544 // uncond branches, and this code folds them. 545 Function::iterator I = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]); 546 while (I != NewFunc->end()) { 547 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator()); 548 if (!BI || BI->isConditional()) { ++I; continue; } 549 550 // Note that we can't eliminate uncond branches if the destination has 551 // single-entry PHI nodes. Eliminating the single-entry phi nodes would 552 // require scanning the VMap to update any entries that point to the phi 553 // node. 554 BasicBlock *Dest = BI->getSuccessor(0); 555 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) { 556 ++I; continue; 557 } 558 559 // We know all single-entry PHI nodes in the inlined function have been 560 // removed, so we just need to splice the blocks. 561 BI->eraseFromParent(); 562 563 // Move all the instructions in the succ to the pred. 564 I->getInstList().splice(I->end(), Dest->getInstList()); 565 566 // Make all PHI nodes that referred to Dest now refer to I as their source. 567 Dest->replaceAllUsesWith(I); 568 569 // Remove the dest block. 570 Dest->eraseFromParent(); 571 572 // Do not increment I, iteratively merge all things this block branches to. 573 } 574} 575