CloneFunction.cpp revision 051a950000e21935165db56695e35bade668193b
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/Function.h" 21#include "llvm/Support/CFG.h" 22#include "llvm/Support/Compiler.h" 23#include "llvm/Transforms/Utils/ValueMapper.h" 24#include "llvm/Analysis/ConstantFolding.h" 25#include "llvm/ADT/SmallVector.h" 26#include <map> 27using namespace llvm; 28 29// CloneBasicBlock - See comments in Cloning.h 30BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB, 31 DenseMap<const Value*, Value*> &ValueMap, 32 const char *NameSuffix, Function *F, 33 ClonedCodeInfo *CodeInfo) { 34 BasicBlock *NewBB = BasicBlock::Create("", F); 35 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 36 NewBB->setUnwindDest(const_cast<BasicBlock*>(BB->getUnwindDest())); 37 38 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 39 40 // Loop over all instructions, and copy them over. 41 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); 42 II != IE; ++II) { 43 Instruction *NewInst = II->clone(); 44 if (II->hasName()) 45 NewInst->setName(II->getName()+NameSuffix); 46 NewBB->getInstList().push_back(NewInst); 47 ValueMap[II] = NewInst; // Add instruction map to value. 48 49 hasCalls |= isa<CallInst>(II); 50 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 51 if (isa<ConstantInt>(AI->getArraySize())) 52 hasStaticAllocas = true; 53 else 54 hasDynamicAllocas = true; 55 } 56 } 57 58 if (CodeInfo) { 59 CodeInfo->ContainsCalls |= hasCalls; 60 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator()); 61 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 62 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 63 BB != &BB->getParent()->getEntryBlock(); 64 } 65 return NewBB; 66} 67 68// Clone OldFunc into NewFunc, transforming the old arguments into references to 69// ArgMap values. 70// 71void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc, 72 DenseMap<const Value*, Value*> &ValueMap, 73 std::vector<ReturnInst*> &Returns, 74 const char *NameSuffix, ClonedCodeInfo *CodeInfo) { 75 assert(NameSuffix && "NameSuffix cannot be null!"); 76 77#ifndef NDEBUG 78 for (Function::const_arg_iterator I = OldFunc->arg_begin(), 79 E = OldFunc->arg_end(); I != E; ++I) 80 assert(ValueMap.count(I) && "No mapping from source argument specified!"); 81#endif 82 83 // Clone the parameter attributes 84 NewFunc->setParamAttrs(OldFunc->getParamAttrs()); 85 86 // Clone the calling convention 87 NewFunc->setCallingConv(OldFunc->getCallingConv()); 88 89 // Loop over all of the basic blocks in the function, cloning them as 90 // appropriate. Note that we save BE this way in order to handle cloning of 91 // recursive functions into themselves. 92 // 93 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 94 BI != BE; ++BI) { 95 const BasicBlock &BB = *BI; 96 97 // Create a new basic block and copy instructions into it! 98 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc, 99 CodeInfo); 100 ValueMap[&BB] = CBB; // Add basic block mapping. 101 102 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator())) 103 Returns.push_back(RI); 104 } 105 106 // Loop over all of the instructions in the function, fixing up operand 107 // references as we go. This uses ValueMap to do all the hard work. 108 // 109 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]), 110 BE = NewFunc->end(); BB != BE; ++BB) { 111 // Fix up the unwind destination. 112 if (BasicBlock *UnwindDest = BB->getUnwindDest()) 113 BB->setUnwindDest(cast<BasicBlock>(ValueMap[UnwindDest])); 114 115 // Loop over all instructions, fixing each one as we find it... 116 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II) 117 RemapInstruction(II, ValueMap); 118 } 119} 120 121/// CloneFunction - Return a copy of the specified function, but without 122/// embedding the function into another module. Also, any references specified 123/// in the ValueMap are changed to refer to their mapped value instead of the 124/// original one. If any of the arguments to the function are in the ValueMap, 125/// the arguments are deleted from the resultant function. The ValueMap is 126/// updated to include mappings from all of the instructions and basicblocks in 127/// the function from their old to new values. 128/// 129Function *llvm::CloneFunction(const Function *F, 130 DenseMap<const Value*, Value*> &ValueMap, 131 ClonedCodeInfo *CodeInfo) { 132 std::vector<const Type*> ArgTypes; 133 134 // The user might be deleting arguments to the function by specifying them in 135 // the ValueMap. If so, we need to not add the arguments to the arg ty vector 136 // 137 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 138 I != E; ++I) 139 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet? 140 ArgTypes.push_back(I->getType()); 141 142 // Create a new function type... 143 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(), 144 ArgTypes, F->getFunctionType()->isVarArg()); 145 146 // Create the new function... 147 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName()); 148 149 // Loop over the arguments, copying the names of the mapped arguments over... 150 Function::arg_iterator DestI = NewF->arg_begin(); 151 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 152 I != E; ++I) 153 if (ValueMap.count(I) == 0) { // Is this argument preserved? 154 DestI->setName(I->getName()); // Copy the name over... 155 ValueMap[I] = DestI++; // Add mapping to ValueMap 156 } 157 158 std::vector<ReturnInst*> Returns; // Ignore returns cloned... 159 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo); 160 return NewF; 161} 162 163 164 165namespace { 166 /// PruningFunctionCloner - This class is a private class used to implement 167 /// the CloneAndPruneFunctionInto method. 168 struct VISIBILITY_HIDDEN PruningFunctionCloner { 169 Function *NewFunc; 170 const Function *OldFunc; 171 DenseMap<const Value*, Value*> &ValueMap; 172 std::vector<ReturnInst*> &Returns; 173 const char *NameSuffix; 174 ClonedCodeInfo *CodeInfo; 175 const TargetData *TD; 176 177 public: 178 PruningFunctionCloner(Function *newFunc, const Function *oldFunc, 179 DenseMap<const Value*, Value*> &valueMap, 180 std::vector<ReturnInst*> &returns, 181 const char *nameSuffix, 182 ClonedCodeInfo *codeInfo, 183 const TargetData *td) 184 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns), 185 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) { 186 } 187 188 /// CloneBlock - The specified block is found to be reachable, clone it and 189 /// anything that it can reach. 190 void CloneBlock(const BasicBlock *BB, 191 std::vector<const BasicBlock*> &ToClone); 192 193 public: 194 /// ConstantFoldMappedInstruction - Constant fold the specified instruction, 195 /// mapping its operands through ValueMap if they are available. 196 Constant *ConstantFoldMappedInstruction(const Instruction *I); 197 }; 198} 199 200/// CloneBlock - The specified block is found to be reachable, clone it and 201/// anything that it can reach. 202void PruningFunctionCloner::CloneBlock(const BasicBlock *BB, 203 std::vector<const BasicBlock*> &ToClone){ 204 Value *&BBEntry = ValueMap[BB]; 205 206 // Have we already cloned this block? 207 if (BBEntry) return; 208 209 // Nope, clone it now. 210 BasicBlock *NewBB; 211 BBEntry = NewBB = BasicBlock::Create(); 212 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 213 214 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 215 216 // Loop over all instructions, and copy them over, DCE'ing as we go. This 217 // loop doesn't include the terminator. 218 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end(); 219 II != IE; ++II) { 220 // If this instruction constant folds, don't bother cloning the instruction, 221 // instead, just add the constant to the value map. 222 if (Constant *C = ConstantFoldMappedInstruction(II)) { 223 ValueMap[II] = C; 224 continue; 225 } 226 227 Instruction *NewInst = II->clone(); 228 if (II->hasName()) 229 NewInst->setName(II->getName()+NameSuffix); 230 NewBB->getInstList().push_back(NewInst); 231 ValueMap[II] = NewInst; // Add instruction map to value. 232 233 hasCalls |= isa<CallInst>(II); 234 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 235 if (isa<ConstantInt>(AI->getArraySize())) 236 hasStaticAllocas = true; 237 else 238 hasDynamicAllocas = true; 239 } 240 } 241 242 // Finally, clone over the terminator. 243 const TerminatorInst *OldTI = BB->getTerminator(); 244 bool TerminatorDone = false; 245 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) { 246 if (BI->isConditional()) { 247 // If the condition was a known constant in the callee... 248 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition()); 249 // Or is a known constant in the caller... 250 if (Cond == 0) 251 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]); 252 253 // Constant fold to uncond branch! 254 if (Cond) { 255 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue()); 256 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB); 257 ToClone.push_back(Dest); 258 TerminatorDone = true; 259 } 260 } 261 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) { 262 // If switching on a value known constant in the caller. 263 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition()); 264 if (Cond == 0) // Or known constant after constant prop in the callee... 265 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]); 266 if (Cond) { // Constant fold to uncond branch! 267 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond)); 268 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB); 269 ToClone.push_back(Dest); 270 TerminatorDone = true; 271 } 272 } 273 274 if (!TerminatorDone) { 275 Instruction *NewInst = OldTI->clone(); 276 if (OldTI->hasName()) 277 NewInst->setName(OldTI->getName()+NameSuffix); 278 NewBB->getInstList().push_back(NewInst); 279 ValueMap[OldTI] = NewInst; // Add instruction map to value. 280 281 // Recursively clone any reachable successor blocks. 282 const TerminatorInst *TI = BB->getTerminator(); 283 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 284 ToClone.push_back(TI->getSuccessor(i)); 285 } 286 287 if (CodeInfo) { 288 CodeInfo->ContainsCalls |= hasCalls; 289 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI); 290 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 291 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 292 BB != &BB->getParent()->front(); 293 } 294 295 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator())) 296 Returns.push_back(RI); 297} 298 299/// ConstantFoldMappedInstruction - Constant fold the specified instruction, 300/// mapping its operands through ValueMap if they are available. 301Constant *PruningFunctionCloner:: 302ConstantFoldMappedInstruction(const Instruction *I) { 303 SmallVector<Constant*, 8> Ops; 304 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 305 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i), 306 ValueMap))) 307 Ops.push_back(Op); 308 else 309 return 0; // All operands not constant! 310 311 312 if (const CmpInst *CI = dyn_cast<CmpInst>(I)) 313 return ConstantFoldCompareInstOperands(CI->getPredicate(), 314 &Ops[0], Ops.size(), TD); 315 else 316 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), 317 &Ops[0], Ops.size(), TD); 318} 319 320/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto, 321/// except that it does some simple constant prop and DCE on the fly. The 322/// effect of this is to copy significantly less code in cases where (for 323/// example) a function call with constant arguments is inlined, and those 324/// constant arguments cause a significant amount of code in the callee to be 325/// dead. Since this doesn't produce an exact copy of the input, it can't be 326/// used for things like CloneFunction or CloneModule. 327void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 328 DenseMap<const Value*, Value*> &ValueMap, 329 std::vector<ReturnInst*> &Returns, 330 const char *NameSuffix, 331 ClonedCodeInfo *CodeInfo, 332 const TargetData *TD) { 333 assert(NameSuffix && "NameSuffix cannot be null!"); 334 335#ifndef NDEBUG 336 for (Function::const_arg_iterator II = OldFunc->arg_begin(), 337 E = OldFunc->arg_end(); II != E; ++II) 338 assert(ValueMap.count(II) && "No mapping from source argument specified!"); 339#endif 340 341 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns, 342 NameSuffix, CodeInfo, TD); 343 344 // Clone the entry block, and anything recursively reachable from it. 345 std::vector<const BasicBlock*> CloneWorklist; 346 CloneWorklist.push_back(&OldFunc->getEntryBlock()); 347 while (!CloneWorklist.empty()) { 348 const BasicBlock *BB = CloneWorklist.back(); 349 CloneWorklist.pop_back(); 350 PFC.CloneBlock(BB, CloneWorklist); 351 } 352 353 // Loop over all of the basic blocks in the old function. If the block was 354 // reachable, we have cloned it and the old block is now in the value map: 355 // insert it into the new function in the right order. If not, ignore it. 356 // 357 // Defer PHI resolution until rest of function is resolved. 358 std::vector<const PHINode*> PHIToResolve; 359 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 360 BI != BE; ++BI) { 361 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]); 362 if (NewBB == 0) continue; // Dead block. 363 364 // Add the new block to the new function. 365 NewFunc->getBasicBlockList().push_back(NewBB); 366 367 // Loop over all of the instructions in the block, fixing up operand 368 // references as we go. This uses ValueMap to do all the hard work. 369 // 370 BasicBlock::iterator I = NewBB->begin(); 371 372 // Handle PHI nodes specially, as we have to remove references to dead 373 // blocks. 374 if (PHINode *PN = dyn_cast<PHINode>(I)) { 375 // Skip over all PHI nodes, remembering them for later. 376 BasicBlock::const_iterator OldI = BI->begin(); 377 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) 378 PHIToResolve.push_back(cast<PHINode>(OldI)); 379 } 380 381 // Otherwise, remap the rest of the instructions normally. 382 for (; I != NewBB->end(); ++I) 383 RemapInstruction(I, ValueMap); 384 } 385 386 // Defer PHI resolution until rest of function is resolved, PHI resolution 387 // requires the CFG to be up-to-date. 388 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) { 389 const PHINode *OPN = PHIToResolve[phino]; 390 unsigned NumPreds = OPN->getNumIncomingValues(); 391 const BasicBlock *OldBB = OPN->getParent(); 392 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]); 393 394 // Map operands for blocks that are live and remove operands for blocks 395 // that are dead. 396 for (; phino != PHIToResolve.size() && 397 PHIToResolve[phino]->getParent() == OldBB; ++phino) { 398 OPN = PHIToResolve[phino]; 399 PHINode *PN = cast<PHINode>(ValueMap[OPN]); 400 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) { 401 if (BasicBlock *MappedBlock = 402 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) { 403 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap); 404 assert(InVal && "Unknown input value?"); 405 PN->setIncomingValue(pred, InVal); 406 PN->setIncomingBlock(pred, MappedBlock); 407 } else { 408 PN->removeIncomingValue(pred, false); 409 --pred, --e; // Revisit the next entry. 410 } 411 } 412 } 413 414 // The loop above has removed PHI entries for those blocks that are dead 415 // and has updated others. However, if a block is live (i.e. copied over) 416 // but its terminator has been changed to not go to this block, then our 417 // phi nodes will have invalid entries. Update the PHI nodes in this 418 // case. 419 PHINode *PN = cast<PHINode>(NewBB->begin()); 420 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB)); 421 if (NumPreds != PN->getNumIncomingValues()) { 422 assert(NumPreds < PN->getNumIncomingValues()); 423 // Count how many times each predecessor comes to this block. 424 std::map<BasicBlock*, unsigned> PredCount; 425 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB); 426 PI != E; ++PI) 427 --PredCount[*PI]; 428 429 // Figure out how many entries to remove from each PHI. 430 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 431 ++PredCount[PN->getIncomingBlock(i)]; 432 433 // At this point, the excess predecessor entries are positive in the 434 // map. Loop over all of the PHIs and remove excess predecessor 435 // entries. 436 BasicBlock::iterator I = NewBB->begin(); 437 for (; (PN = dyn_cast<PHINode>(I)); ++I) { 438 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(), 439 E = PredCount.end(); PCI != E; ++PCI) { 440 BasicBlock *Pred = PCI->first; 441 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove) 442 PN->removeIncomingValue(Pred, false); 443 } 444 } 445 } 446 447 // If the loops above have made these phi nodes have 0 or 1 operand, 448 // replace them with undef or the input value. We must do this for 449 // correctness, because 0-operand phis are not valid. 450 PN = cast<PHINode>(NewBB->begin()); 451 if (PN->getNumIncomingValues() == 0) { 452 BasicBlock::iterator I = NewBB->begin(); 453 BasicBlock::const_iterator OldI = OldBB->begin(); 454 while ((PN = dyn_cast<PHINode>(I++))) { 455 Value *NV = UndefValue::get(PN->getType()); 456 PN->replaceAllUsesWith(NV); 457 assert(ValueMap[OldI] == PN && "ValueMap mismatch"); 458 ValueMap[OldI] = NV; 459 PN->eraseFromParent(); 460 ++OldI; 461 } 462 } 463 // NOTE: We cannot eliminate single entry phi nodes here, because of 464 // ValueMap. Single entry phi nodes can have multiple ValueMap entries 465 // pointing at them. Thus, deleting one would require scanning the ValueMap 466 // to update any entries in it that would require that. This would be 467 // really slow. 468 } 469 470 // Now that the inlined function body has been fully constructed, go through 471 // and zap unconditional fall-through branches. This happen all the time when 472 // specializing code: code specialization turns conditional branches into 473 // uncond branches, and this code folds them. 474 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]); 475 while (I != NewFunc->end()) { 476 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator()); 477 if (!BI || BI->isConditional()) { ++I; continue; } 478 479 // Note that we can't eliminate uncond branches if the destination has 480 // single-entry PHI nodes. Eliminating the single-entry phi nodes would 481 // require scanning the ValueMap to update any entries that point to the phi 482 // node. 483 BasicBlock *Dest = BI->getSuccessor(0); 484 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) { 485 ++I; continue; 486 } 487 488 // We know all single-entry PHI nodes in the inlined function have been 489 // removed, so we just need to splice the blocks. 490 BI->eraseFromParent(); 491 492 // Move all the instructions in the succ to the pred. 493 I->getInstList().splice(I->end(), Dest->getInstList()); 494 495 // Make all PHI nodes that referred to Dest now refer to I as their source. 496 Dest->replaceAllUsesWith(I); 497 498 // Remove the dest block. 499 Dest->eraseFromParent(); 500 501 // Do not increment I, iteratively merge all things this block branches to. 502 } 503} 504