CloneFunction.cpp revision 7bc230ec6aad867333db43636f7beda68bb628ae
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 MDNode *UpdateInlinedAtInfo(MDNode *InsnMD, MDNode *TheCallMD) { 338 DILocation ILoc(InsnMD); 339 if (!ILoc.Verify()) return InsnMD; 340 341 DILocation CallLoc(TheCallMD); 342 if (!CallLoc.Verify()) return InsnMD; 343 344 DILocation OrigLocation = ILoc.getOrigLocation(); 345 MDNode *NewLoc = TheCallMD; 346 if (OrigLocation.Verify()) 347 NewLoc = UpdateInlinedAtInfo(OrigLocation, TheCallMD); 348 349 Value *MDVs[] = { 350 InsnMD->getOperand(0), // Line 351 InsnMD->getOperand(1), // Col 352 InsnMD->getOperand(2), // Scope 353 NewLoc 354 }; 355 return MDNode::get(InsnMD->getContext(), MDVs, 4); 356} 357 358/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto, 359/// except that it does some simple constant prop and DCE on the fly. The 360/// effect of this is to copy significantly less code in cases where (for 361/// example) a function call with constant arguments is inlined, and those 362/// constant arguments cause a significant amount of code in the callee to be 363/// dead. Since this doesn't produce an exact copy of the input, it can't be 364/// used for things like CloneFunction or CloneModule. 365void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 366 ValueToValueMapTy &VMap, 367 SmallVectorImpl<ReturnInst*> &Returns, 368 const char *NameSuffix, 369 ClonedCodeInfo *CodeInfo, 370 const TargetData *TD, 371 Instruction *TheCall) { 372 assert(NameSuffix && "NameSuffix cannot be null!"); 373 374#ifndef NDEBUG 375 for (Function::const_arg_iterator II = OldFunc->arg_begin(), 376 E = OldFunc->arg_end(); II != E; ++II) 377 assert(VMap.count(II) && "No mapping from source argument specified!"); 378#endif 379 380 PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, Returns, 381 NameSuffix, CodeInfo, TD); 382 383 // Clone the entry block, and anything recursively reachable from it. 384 std::vector<const BasicBlock*> CloneWorklist; 385 CloneWorklist.push_back(&OldFunc->getEntryBlock()); 386 while (!CloneWorklist.empty()) { 387 const BasicBlock *BB = CloneWorklist.back(); 388 CloneWorklist.pop_back(); 389 PFC.CloneBlock(BB, CloneWorklist); 390 } 391 392 // Loop over all of the basic blocks in the old function. If the block was 393 // reachable, we have cloned it and the old block is now in the value map: 394 // insert it into the new function in the right order. If not, ignore it. 395 // 396 // Defer PHI resolution until rest of function is resolved. 397 SmallVector<const PHINode*, 16> PHIToResolve; 398 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 399 BI != BE; ++BI) { 400 BasicBlock *NewBB = cast_or_null<BasicBlock>(VMap[BI]); 401 if (NewBB == 0) continue; // Dead block. 402 403 // Add the new block to the new function. 404 NewFunc->getBasicBlockList().push_back(NewBB); 405 406 // Loop over all of the instructions in the block, fixing up operand 407 // references as we go. This uses VMap to do all the hard work. 408 // 409 BasicBlock::iterator I = NewBB->begin(); 410 411 MDNode *TheCallMD = NULL; 412 if (TheCall && TheCall->hasMetadata()) 413 TheCallMD = TheCall->getMetadata(LLVMContext::MD_dbg); 414 415 // Handle PHI nodes specially, as we have to remove references to dead 416 // blocks. 417 if (PHINode *PN = dyn_cast<PHINode>(I)) { 418 // Skip over all PHI nodes, remembering them for later. 419 BasicBlock::const_iterator OldI = BI->begin(); 420 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) { 421 if (I->hasMetadata()) { 422 if (TheCallMD) { 423 if (MDNode *IMD = I->getMetadata(LLVMContext::MD_dbg)) { 424 MDNode *NewMD = UpdateInlinedAtInfo(IMD, TheCallMD); 425 I->setMetadata(LLVMContext::MD_dbg, NewMD); 426 } 427 } else { 428 // The cloned instruction has dbg info but the call instruction 429 // does not have dbg info. Remove dbg info from cloned instruction. 430 I->setMetadata(LLVMContext::MD_dbg, 0); 431 } 432 } 433 PHIToResolve.push_back(cast<PHINode>(OldI)); 434 } 435 } 436 437 // FIXME: 438 // FIXME: 439 // FIXME: Unclone all this metadata stuff. 440 // FIXME: 441 // FIXME: 442 443 // Otherwise, remap the rest of the instructions normally. 444 for (; I != NewBB->end(); ++I) { 445 if (I->hasMetadata()) { 446 if (TheCallMD) { 447 if (MDNode *IMD = I->getMetadata(LLVMContext::MD_dbg)) { 448 MDNode *NewMD = UpdateInlinedAtInfo(IMD, TheCallMD); 449 I->setMetadata(LLVMContext::MD_dbg, NewMD); 450 } 451 } else { 452 // The cloned instruction has dbg info but the call instruction 453 // does not have dbg info. Remove dbg info from cloned instruction. 454 I->setMetadata(LLVMContext::MD_dbg, 0); 455 } 456 } 457 RemapInstruction(I, VMap); 458 } 459 } 460 461 // Defer PHI resolution until rest of function is resolved, PHI resolution 462 // requires the CFG to be up-to-date. 463 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) { 464 const PHINode *OPN = PHIToResolve[phino]; 465 unsigned NumPreds = OPN->getNumIncomingValues(); 466 const BasicBlock *OldBB = OPN->getParent(); 467 BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]); 468 469 // Map operands for blocks that are live and remove operands for blocks 470 // that are dead. 471 for (; phino != PHIToResolve.size() && 472 PHIToResolve[phino]->getParent() == OldBB; ++phino) { 473 OPN = PHIToResolve[phino]; 474 PHINode *PN = cast<PHINode>(VMap[OPN]); 475 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) { 476 if (BasicBlock *MappedBlock = 477 cast_or_null<BasicBlock>(VMap[PN->getIncomingBlock(pred)])) { 478 Value *InVal = MapValue(PN->getIncomingValue(pred), 479 VMap); 480 assert(InVal && "Unknown input value?"); 481 PN->setIncomingValue(pred, InVal); 482 PN->setIncomingBlock(pred, MappedBlock); 483 } else { 484 PN->removeIncomingValue(pred, false); 485 --pred, --e; // Revisit the next entry. 486 } 487 } 488 } 489 490 // The loop above has removed PHI entries for those blocks that are dead 491 // and has updated others. However, if a block is live (i.e. copied over) 492 // but its terminator has been changed to not go to this block, then our 493 // phi nodes will have invalid entries. Update the PHI nodes in this 494 // case. 495 PHINode *PN = cast<PHINode>(NewBB->begin()); 496 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB)); 497 if (NumPreds != PN->getNumIncomingValues()) { 498 assert(NumPreds < PN->getNumIncomingValues()); 499 // Count how many times each predecessor comes to this block. 500 std::map<BasicBlock*, unsigned> PredCount; 501 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB); 502 PI != E; ++PI) 503 --PredCount[*PI]; 504 505 // Figure out how many entries to remove from each PHI. 506 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 507 ++PredCount[PN->getIncomingBlock(i)]; 508 509 // At this point, the excess predecessor entries are positive in the 510 // map. Loop over all of the PHIs and remove excess predecessor 511 // entries. 512 BasicBlock::iterator I = NewBB->begin(); 513 for (; (PN = dyn_cast<PHINode>(I)); ++I) { 514 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(), 515 E = PredCount.end(); PCI != E; ++PCI) { 516 BasicBlock *Pred = PCI->first; 517 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove) 518 PN->removeIncomingValue(Pred, false); 519 } 520 } 521 } 522 523 // If the loops above have made these phi nodes have 0 or 1 operand, 524 // replace them with undef or the input value. We must do this for 525 // correctness, because 0-operand phis are not valid. 526 PN = cast<PHINode>(NewBB->begin()); 527 if (PN->getNumIncomingValues() == 0) { 528 BasicBlock::iterator I = NewBB->begin(); 529 BasicBlock::const_iterator OldI = OldBB->begin(); 530 while ((PN = dyn_cast<PHINode>(I++))) { 531 Value *NV = UndefValue::get(PN->getType()); 532 PN->replaceAllUsesWith(NV); 533 assert(VMap[OldI] == PN && "VMap mismatch"); 534 VMap[OldI] = NV; 535 PN->eraseFromParent(); 536 ++OldI; 537 } 538 } 539 // NOTE: We cannot eliminate single entry phi nodes here, because of 540 // VMap. Single entry phi nodes can have multiple VMap entries 541 // pointing at them. Thus, deleting one would require scanning the VMap 542 // to update any entries in it that would require that. This would be 543 // really slow. 544 } 545 546 // Now that the inlined function body has been fully constructed, go through 547 // and zap unconditional fall-through branches. This happen all the time when 548 // specializing code: code specialization turns conditional branches into 549 // uncond branches, and this code folds them. 550 Function::iterator I = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]); 551 while (I != NewFunc->end()) { 552 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator()); 553 if (!BI || BI->isConditional()) { ++I; continue; } 554 555 // Note that we can't eliminate uncond branches if the destination has 556 // single-entry PHI nodes. Eliminating the single-entry phi nodes would 557 // require scanning the VMap to update any entries that point to the phi 558 // node. 559 BasicBlock *Dest = BI->getSuccessor(0); 560 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) { 561 ++I; continue; 562 } 563 564 // We know all single-entry PHI nodes in the inlined function have been 565 // removed, so we just need to splice the blocks. 566 BI->eraseFromParent(); 567 568 // Move all the instructions in the succ to the pred. 569 I->getInstList().splice(I->end(), Dest->getInstList()); 570 571 // Make all PHI nodes that referred to Dest now refer to I as their source. 572 Dest->replaceAllUsesWith(I); 573 574 // Remove the dest block. 575 Dest->eraseFromParent(); 576 577 // Do not increment I, iteratively merge all things this block branches to. 578 } 579} 580