CloneFunction.cpp revision ab6b226978644c438a3a7768a06dcd48509d000c
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/Support/CFG.h" 24#include "llvm/Support/Compiler.h" 25#include "llvm/Transforms/Utils/ValueMapper.h" 26#include "llvm/Analysis/ConstantFolding.h" 27#include "llvm/ADT/SmallVector.h" 28#include <map> 29using namespace llvm; 30 31// CloneBasicBlock - See comments in Cloning.h 32BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB, 33 DenseMap<const Value*, Value*> &ValueMap, 34 const char *NameSuffix, Function *F, 35 ClonedCodeInfo *CodeInfo) { 36 BasicBlock *NewBB = BasicBlock::Create("", F); 37 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 38 39 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 40 41 // Loop over all instructions, and copy them over. 42 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); 43 II != IE; ++II) { 44 Instruction *NewInst = II->clone(); 45 if (II->hasName()) 46 NewInst->setName(II->getName()+NameSuffix); 47 NewBB->getInstList().push_back(NewInst); 48 ValueMap[II] = NewInst; // Add instruction map to value. 49 50 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II)); 51 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 52 if (isa<ConstantInt>(AI->getArraySize())) 53 hasStaticAllocas = true; 54 else 55 hasDynamicAllocas = true; 56 } 57 } 58 59 if (CodeInfo) { 60 CodeInfo->ContainsCalls |= hasCalls; 61 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator()); 62 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 63 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 64 BB != &BB->getParent()->getEntryBlock(); 65 } 66 return NewBB; 67} 68 69// Clone OldFunc into NewFunc, transforming the old arguments into references to 70// ArgMap values. 71// 72void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc, 73 DenseMap<const Value*, Value*> &ValueMap, 74 std::vector<ReturnInst*> &Returns, 75 const char *NameSuffix, ClonedCodeInfo *CodeInfo) { 76 assert(NameSuffix && "NameSuffix cannot be null!"); 77 78#ifndef NDEBUG 79 for (Function::const_arg_iterator I = OldFunc->arg_begin(), 80 E = OldFunc->arg_end(); I != E; ++I) 81 assert(ValueMap.count(I) && "No mapping from source argument specified!"); 82#endif 83 84 // Clone any attributes. 85 if (NewFunc->arg_size() == OldFunc->arg_size()) 86 NewFunc->copyAttributesFrom(OldFunc); 87 else { 88 //Some arguments were deleted with the ValueMap. Copy arguments one by one 89 for (Function::const_arg_iterator I = OldFunc->arg_begin(), 90 E = OldFunc->arg_end(); I != E; ++I) 91 if (Argument* Anew = dyn_cast<Argument>(ValueMap[I])) 92 Anew->addAttr( OldFunc->getAttributes() 93 .getParamAttributes(I->getArgNo() + 1)); 94 NewFunc->setAttributes(NewFunc->getAttributes() 95 .addAttr(0, OldFunc->getAttributes() 96 .getRetAttributes())); 97 NewFunc->setAttributes(NewFunc->getAttributes() 98 .addAttr(~0, OldFunc->getAttributes() 99 .getFnAttributes())); 100 101 } 102 103 // Loop over all of the basic blocks in the function, cloning them as 104 // appropriate. Note that we save BE this way in order to handle cloning of 105 // recursive functions into themselves. 106 // 107 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 108 BI != BE; ++BI) { 109 const BasicBlock &BB = *BI; 110 111 // Create a new basic block and copy instructions into it! 112 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc, 113 CodeInfo); 114 ValueMap[&BB] = CBB; // Add basic block mapping. 115 116 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator())) 117 Returns.push_back(RI); 118 } 119 120 // Loop over all of the instructions in the function, fixing up operand 121 // references as we go. This uses ValueMap to do all the hard work. 122 // 123 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]), 124 BE = NewFunc->end(); BB != BE; ++BB) 125 // Loop over all instructions, fixing each one as we find it... 126 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II) 127 RemapInstruction(II, ValueMap); 128} 129 130/// CloneFunction - Return a copy of the specified function, but without 131/// embedding the function into another module. Also, any references specified 132/// in the ValueMap are changed to refer to their mapped value instead of the 133/// original one. If any of the arguments to the function are in the ValueMap, 134/// the arguments are deleted from the resultant function. The ValueMap is 135/// updated to include mappings from all of the instructions and basicblocks in 136/// the function from their old to new values. 137/// 138Function *llvm::CloneFunction(const Function *F, 139 DenseMap<const Value*, Value*> &ValueMap, 140 ClonedCodeInfo *CodeInfo) { 141 std::vector<const Type*> ArgTypes; 142 143 // The user might be deleting arguments to the function by specifying them in 144 // the ValueMap. If so, we need to not add the arguments to the arg ty vector 145 // 146 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 147 I != E; ++I) 148 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet? 149 ArgTypes.push_back(I->getType()); 150 151 // Create a new function type... 152 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(), 153 ArgTypes, F->getFunctionType()->isVarArg()); 154 155 // Create the new function... 156 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName()); 157 158 // Loop over the arguments, copying the names of the mapped arguments over... 159 Function::arg_iterator DestI = NewF->arg_begin(); 160 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 161 I != E; ++I) 162 if (ValueMap.count(I) == 0) { // Is this argument preserved? 163 DestI->setName(I->getName()); // Copy the name over... 164 ValueMap[I] = DestI++; // Add mapping to ValueMap 165 } 166 167 std::vector<ReturnInst*> Returns; // Ignore returns cloned... 168 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo); 169 return NewF; 170} 171 172 173 174namespace { 175 /// PruningFunctionCloner - This class is a private class used to implement 176 /// the CloneAndPruneFunctionInto method. 177 struct VISIBILITY_HIDDEN PruningFunctionCloner { 178 Function *NewFunc; 179 const Function *OldFunc; 180 DenseMap<const Value*, Value*> &ValueMap; 181 std::vector<ReturnInst*> &Returns; 182 const char *NameSuffix; 183 ClonedCodeInfo *CodeInfo; 184 const TargetData *TD; 185 Value *DbgFnStart; 186 public: 187 PruningFunctionCloner(Function *newFunc, const Function *oldFunc, 188 DenseMap<const Value*, Value*> &valueMap, 189 std::vector<ReturnInst*> &returns, 190 const char *nameSuffix, 191 ClonedCodeInfo *codeInfo, 192 const TargetData *td) 193 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns), 194 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td), DbgFnStart(NULL) { 195 } 196 197 /// CloneBlock - The specified block is found to be reachable, clone it and 198 /// anything that it can reach. 199 void CloneBlock(const BasicBlock *BB, 200 std::vector<const BasicBlock*> &ToClone); 201 202 public: 203 /// ConstantFoldMappedInstruction - Constant fold the specified instruction, 204 /// mapping its operands through ValueMap if they are available. 205 Constant *ConstantFoldMappedInstruction(const Instruction *I); 206 }; 207} 208 209/// CloneBlock - The specified block is found to be reachable, clone it and 210/// anything that it can reach. 211void PruningFunctionCloner::CloneBlock(const BasicBlock *BB, 212 std::vector<const BasicBlock*> &ToClone){ 213 Value *&BBEntry = ValueMap[BB]; 214 215 // Have we already cloned this block? 216 if (BBEntry) return; 217 218 // Nope, clone it now. 219 BasicBlock *NewBB; 220 BBEntry = NewBB = BasicBlock::Create(); 221 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 222 223 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 224 225 // Loop over all instructions, and copy them over, DCE'ing as we go. This 226 // loop doesn't include the terminator. 227 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end(); 228 II != IE; ++II) { 229 // If this instruction constant folds, don't bother cloning the instruction, 230 // instead, just add the constant to the value map. 231 if (Constant *C = ConstantFoldMappedInstruction(II)) { 232 ValueMap[II] = C; 233 continue; 234 } 235 236 // Do not clone llvm.dbg.func.start and corresponding llvm.dbg.region.end. 237 if (const DbgFuncStartInst *DFSI = dyn_cast<DbgFuncStartInst>(II)) { 238 DbgFnStart = DFSI->getSubprogram(); 239 continue; 240 } 241 if (const DbgRegionEndInst *DREIS = dyn_cast<DbgRegionEndInst>(II)) { 242 if (DREIS->getContext() == DbgFnStart) 243 continue; 244 } 245 246 Instruction *NewInst = II->clone(); 247 if (II->hasName()) 248 NewInst->setName(II->getName()+NameSuffix); 249 NewBB->getInstList().push_back(NewInst); 250 ValueMap[II] = NewInst; // Add instruction map to value. 251 252 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II)); 253 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 254 if (isa<ConstantInt>(AI->getArraySize())) 255 hasStaticAllocas = true; 256 else 257 hasDynamicAllocas = true; 258 } 259 } 260 261 // Finally, clone over the terminator. 262 const TerminatorInst *OldTI = BB->getTerminator(); 263 bool TerminatorDone = false; 264 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) { 265 if (BI->isConditional()) { 266 // If the condition was a known constant in the callee... 267 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition()); 268 // Or is a known constant in the caller... 269 if (Cond == 0) 270 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]); 271 272 // Constant fold to uncond branch! 273 if (Cond) { 274 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue()); 275 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB); 276 ToClone.push_back(Dest); 277 TerminatorDone = true; 278 } 279 } 280 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) { 281 // If switching on a value known constant in the caller. 282 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition()); 283 if (Cond == 0) // Or known constant after constant prop in the callee... 284 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]); 285 if (Cond) { // Constant fold to uncond branch! 286 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond)); 287 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB); 288 ToClone.push_back(Dest); 289 TerminatorDone = true; 290 } 291 } 292 293 if (!TerminatorDone) { 294 Instruction *NewInst = OldTI->clone(); 295 if (OldTI->hasName()) 296 NewInst->setName(OldTI->getName()+NameSuffix); 297 NewBB->getInstList().push_back(NewInst); 298 ValueMap[OldTI] = NewInst; // Add instruction map to value. 299 300 // Recursively clone any reachable successor blocks. 301 const TerminatorInst *TI = BB->getTerminator(); 302 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 303 ToClone.push_back(TI->getSuccessor(i)); 304 } 305 306 if (CodeInfo) { 307 CodeInfo->ContainsCalls |= hasCalls; 308 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI); 309 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 310 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 311 BB != &BB->getParent()->front(); 312 } 313 314 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator())) 315 Returns.push_back(RI); 316} 317 318/// ConstantFoldMappedInstruction - Constant fold the specified instruction, 319/// mapping its operands through ValueMap if they are available. 320Constant *PruningFunctionCloner:: 321ConstantFoldMappedInstruction(const Instruction *I) { 322 SmallVector<Constant*, 8> Ops; 323 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 324 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i), 325 ValueMap))) 326 Ops.push_back(Op); 327 else 328 return 0; // All operands not constant! 329 330 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 331 return ConstantFoldCompareInstOperands(CI->getPredicate(), 332 &Ops[0], Ops.size(), TD); 333 334 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) 335 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) 336 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr) 337 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) 338 if (GV->isConstant() && !GV->isDeclaration() && 339 !GV->mayBeOverridden()) 340 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), 341 CE); 342 343 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0], 344 Ops.size(), TD); 345} 346 347/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto, 348/// except that it does some simple constant prop and DCE on the fly. The 349/// effect of this is to copy significantly less code in cases where (for 350/// example) a function call with constant arguments is inlined, and those 351/// constant arguments cause a significant amount of code in the callee to be 352/// dead. Since this doesn't produce an exact copy of the input, it can't be 353/// used for things like CloneFunction or CloneModule. 354void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 355 DenseMap<const Value*, Value*> &ValueMap, 356 std::vector<ReturnInst*> &Returns, 357 const char *NameSuffix, 358 ClonedCodeInfo *CodeInfo, 359 const TargetData *TD) { 360 assert(NameSuffix && "NameSuffix cannot be null!"); 361 362#ifndef NDEBUG 363 for (Function::const_arg_iterator II = OldFunc->arg_begin(), 364 E = OldFunc->arg_end(); II != E; ++II) 365 assert(ValueMap.count(II) && "No mapping from source argument specified!"); 366#endif 367 368 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns, 369 NameSuffix, CodeInfo, TD); 370 371 // Clone the entry block, and anything recursively reachable from it. 372 std::vector<const BasicBlock*> CloneWorklist; 373 CloneWorklist.push_back(&OldFunc->getEntryBlock()); 374 while (!CloneWorklist.empty()) { 375 const BasicBlock *BB = CloneWorklist.back(); 376 CloneWorklist.pop_back(); 377 PFC.CloneBlock(BB, CloneWorklist); 378 } 379 380 // Loop over all of the basic blocks in the old function. If the block was 381 // reachable, we have cloned it and the old block is now in the value map: 382 // insert it into the new function in the right order. If not, ignore it. 383 // 384 // Defer PHI resolution until rest of function is resolved. 385 std::vector<const PHINode*> PHIToResolve; 386 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 387 BI != BE; ++BI) { 388 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]); 389 if (NewBB == 0) continue; // Dead block. 390 391 // Add the new block to the new function. 392 NewFunc->getBasicBlockList().push_back(NewBB); 393 394 // Loop over all of the instructions in the block, fixing up operand 395 // references as we go. This uses ValueMap to do all the hard work. 396 // 397 BasicBlock::iterator I = NewBB->begin(); 398 399 // Handle PHI nodes specially, as we have to remove references to dead 400 // blocks. 401 if (PHINode *PN = dyn_cast<PHINode>(I)) { 402 // Skip over all PHI nodes, remembering them for later. 403 BasicBlock::const_iterator OldI = BI->begin(); 404 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) 405 PHIToResolve.push_back(cast<PHINode>(OldI)); 406 } 407 408 // Otherwise, remap the rest of the instructions normally. 409 for (; I != NewBB->end(); ++I) 410 RemapInstruction(I, ValueMap); 411 } 412 413 // Defer PHI resolution until rest of function is resolved, PHI resolution 414 // requires the CFG to be up-to-date. 415 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) { 416 const PHINode *OPN = PHIToResolve[phino]; 417 unsigned NumPreds = OPN->getNumIncomingValues(); 418 const BasicBlock *OldBB = OPN->getParent(); 419 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]); 420 421 // Map operands for blocks that are live and remove operands for blocks 422 // that are dead. 423 for (; phino != PHIToResolve.size() && 424 PHIToResolve[phino]->getParent() == OldBB; ++phino) { 425 OPN = PHIToResolve[phino]; 426 PHINode *PN = cast<PHINode>(ValueMap[OPN]); 427 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) { 428 if (BasicBlock *MappedBlock = 429 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) { 430 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap); 431 assert(InVal && "Unknown input value?"); 432 PN->setIncomingValue(pred, InVal); 433 PN->setIncomingBlock(pred, MappedBlock); 434 } else { 435 PN->removeIncomingValue(pred, false); 436 --pred, --e; // Revisit the next entry. 437 } 438 } 439 } 440 441 // The loop above has removed PHI entries for those blocks that are dead 442 // and has updated others. However, if a block is live (i.e. copied over) 443 // but its terminator has been changed to not go to this block, then our 444 // phi nodes will have invalid entries. Update the PHI nodes in this 445 // case. 446 PHINode *PN = cast<PHINode>(NewBB->begin()); 447 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB)); 448 if (NumPreds != PN->getNumIncomingValues()) { 449 assert(NumPreds < PN->getNumIncomingValues()); 450 // Count how many times each predecessor comes to this block. 451 std::map<BasicBlock*, unsigned> PredCount; 452 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB); 453 PI != E; ++PI) 454 --PredCount[*PI]; 455 456 // Figure out how many entries to remove from each PHI. 457 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 458 ++PredCount[PN->getIncomingBlock(i)]; 459 460 // At this point, the excess predecessor entries are positive in the 461 // map. Loop over all of the PHIs and remove excess predecessor 462 // entries. 463 BasicBlock::iterator I = NewBB->begin(); 464 for (; (PN = dyn_cast<PHINode>(I)); ++I) { 465 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(), 466 E = PredCount.end(); PCI != E; ++PCI) { 467 BasicBlock *Pred = PCI->first; 468 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove) 469 PN->removeIncomingValue(Pred, false); 470 } 471 } 472 } 473 474 // If the loops above have made these phi nodes have 0 or 1 operand, 475 // replace them with undef or the input value. We must do this for 476 // correctness, because 0-operand phis are not valid. 477 PN = cast<PHINode>(NewBB->begin()); 478 if (PN->getNumIncomingValues() == 0) { 479 BasicBlock::iterator I = NewBB->begin(); 480 BasicBlock::const_iterator OldI = OldBB->begin(); 481 while ((PN = dyn_cast<PHINode>(I++))) { 482 Value *NV = UndefValue::get(PN->getType()); 483 PN->replaceAllUsesWith(NV); 484 assert(ValueMap[OldI] == PN && "ValueMap mismatch"); 485 ValueMap[OldI] = NV; 486 PN->eraseFromParent(); 487 ++OldI; 488 } 489 } 490 // NOTE: We cannot eliminate single entry phi nodes here, because of 491 // ValueMap. Single entry phi nodes can have multiple ValueMap entries 492 // pointing at them. Thus, deleting one would require scanning the ValueMap 493 // to update any entries in it that would require that. This would be 494 // really slow. 495 } 496 497 // Now that the inlined function body has been fully constructed, go through 498 // and zap unconditional fall-through branches. This happen all the time when 499 // specializing code: code specialization turns conditional branches into 500 // uncond branches, and this code folds them. 501 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]); 502 while (I != NewFunc->end()) { 503 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator()); 504 if (!BI || BI->isConditional()) { ++I; continue; } 505 506 // Note that we can't eliminate uncond branches if the destination has 507 // single-entry PHI nodes. Eliminating the single-entry phi nodes would 508 // require scanning the ValueMap to update any entries that point to the phi 509 // node. 510 BasicBlock *Dest = BI->getSuccessor(0); 511 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) { 512 ++I; continue; 513 } 514 515 // We know all single-entry PHI nodes in the inlined function have been 516 // removed, so we just need to splice the blocks. 517 BI->eraseFromParent(); 518 519 // Move all the instructions in the succ to the pred. 520 I->getInstList().splice(I->end(), Dest->getInstList()); 521 522 // Make all PHI nodes that referred to Dest now refer to I as their source. 523 Dest->replaceAllUsesWith(I); 524 525 // Remove the dest block. 526 Dest->eraseFromParent(); 527 528 // Do not increment I, iteratively merge all things this block branches to. 529 } 530} 531