CloneFunction.cpp revision 9133fe28954d498fc4de13064c7d65bd811de02c
1//===- CloneFunction.cpp - Clone a function into another function ---------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source 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 "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 = new BasicBlock("", F); 35 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 36 37 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 38 39 // Loop over all instructions, and copy them over. 40 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); 41 II != IE; ++II) { 42 Instruction *NewInst = II->clone(); 43 if (II->hasName()) 44 NewInst->setName(II->getName()+NameSuffix); 45 NewBB->getInstList().push_back(NewInst); 46 ValueMap[II] = NewInst; // Add instruction map to value. 47 48 hasCalls |= isa<CallInst>(II); 49 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 50 if (isa<ConstantInt>(AI->getArraySize())) 51 hasStaticAllocas = true; 52 else 53 hasDynamicAllocas = true; 54 } 55 } 56 57 if (CodeInfo) { 58 CodeInfo->ContainsCalls |= hasCalls; 59 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator()); 60 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 61 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 62 BB != &BB->getParent()->front(); 63 } 64 return NewBB; 65} 66 67// Clone OldFunc into NewFunc, transforming the old arguments into references to 68// ArgMap values. 69// 70void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc, 71 DenseMap<const Value*, Value*> &ValueMap, 72 std::vector<ReturnInst*> &Returns, 73 const char *NameSuffix, ClonedCodeInfo *CodeInfo) { 74 assert(NameSuffix && "NameSuffix cannot be null!"); 75 76#ifndef NDEBUG 77 for (Function::const_arg_iterator I = OldFunc->arg_begin(), 78 E = OldFunc->arg_end(); I != E; ++I) 79 assert(ValueMap.count(I) && "No mapping from source argument specified!"); 80#endif 81 82 // Loop over all of the basic blocks in the function, cloning them as 83 // appropriate. Note that we save BE this way in order to handle cloning of 84 // recursive functions into themselves. 85 // 86 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 87 BI != BE; ++BI) { 88 const BasicBlock &BB = *BI; 89 90 // Create a new basic block and copy instructions into it! 91 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc, 92 CodeInfo); 93 ValueMap[&BB] = CBB; // Add basic block mapping. 94 95 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator())) 96 Returns.push_back(RI); 97 } 98 99 // Loop over all of the instructions in the function, fixing up operand 100 // references as we go. This uses ValueMap to do all the hard work. 101 // 102 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]), 103 BE = NewFunc->end(); BB != BE; ++BB) 104 // Loop over all instructions, fixing each one as we find it... 105 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II) 106 RemapInstruction(II, ValueMap); 107} 108 109/// CloneFunction - Return a copy of the specified function, but without 110/// embedding the function into another module. Also, any references specified 111/// in the ValueMap are changed to refer to their mapped value instead of the 112/// original one. If any of the arguments to the function are in the ValueMap, 113/// the arguments are deleted from the resultant function. The ValueMap is 114/// updated to include mappings from all of the instructions and basicblocks in 115/// the function from their old to new values. 116/// 117Function *llvm::CloneFunction(const Function *F, 118 DenseMap<const Value*, Value*> &ValueMap, 119 ClonedCodeInfo *CodeInfo) { 120 std::vector<const Type*> ArgTypes; 121 122 // The user might be deleting arguments to the function by specifying them in 123 // the ValueMap. If so, we need to not add the arguments to the arg ty vector 124 // 125 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 126 I != E; ++I) 127 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet? 128 ArgTypes.push_back(I->getType()); 129 130 // Create a new function type... 131 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(), 132 ArgTypes, F->getFunctionType()->isVarArg()); 133 134 // Create the new function... 135 Function *NewF = new Function(FTy, F->getLinkage(), F->getName()); 136 137 // Loop over the arguments, copying the names of the mapped arguments over... 138 Function::arg_iterator DestI = NewF->arg_begin(); 139 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 140 I != E; ++I) 141 if (ValueMap.count(I) == 0) { // Is this argument preserved? 142 DestI->setName(I->getName()); // Copy the name over... 143 ValueMap[I] = DestI++; // Add mapping to ValueMap 144 } 145 146 std::vector<ReturnInst*> Returns; // Ignore returns cloned... 147 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo); 148 return NewF; 149} 150 151 152 153namespace { 154 /// PruningFunctionCloner - This class is a private class used to implement 155 /// the CloneAndPruneFunctionInto method. 156 struct VISIBILITY_HIDDEN PruningFunctionCloner { 157 Function *NewFunc; 158 const Function *OldFunc; 159 DenseMap<const Value*, Value*> &ValueMap; 160 std::vector<ReturnInst*> &Returns; 161 const char *NameSuffix; 162 ClonedCodeInfo *CodeInfo; 163 const TargetData *TD; 164 165 public: 166 PruningFunctionCloner(Function *newFunc, const Function *oldFunc, 167 DenseMap<const Value*, Value*> &valueMap, 168 std::vector<ReturnInst*> &returns, 169 const char *nameSuffix, 170 ClonedCodeInfo *codeInfo, 171 const TargetData *td) 172 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns), 173 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) { 174 } 175 176 /// CloneBlock - The specified block is found to be reachable, clone it and 177 /// anything that it can reach. 178 void CloneBlock(const BasicBlock *BB); 179 180 public: 181 /// ConstantFoldMappedInstruction - Constant fold the specified instruction, 182 /// mapping its operands through ValueMap if they are available. 183 Constant *ConstantFoldMappedInstruction(const Instruction *I); 184 }; 185} 186 187/// CloneBlock - The specified block is found to be reachable, clone it and 188/// anything that it can reach. 189void PruningFunctionCloner::CloneBlock(const BasicBlock *BB) { 190 Value *&BBEntry = ValueMap[BB]; 191 192 // Have we already cloned this block? 193 if (BBEntry) return; 194 195 // Nope, clone it now. 196 BasicBlock *NewBB; 197 BBEntry = NewBB = new BasicBlock(); 198 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 199 200 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 201 202 // Loop over all instructions, and copy them over, DCE'ing as we go. This 203 // loop doesn't include the terminator. 204 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end(); 205 II != IE; ++II) { 206 // If this instruction constant folds, don't bother cloning the instruction, 207 // instead, just add the constant to the value map. 208 if (Constant *C = ConstantFoldMappedInstruction(II)) { 209 ValueMap[II] = C; 210 continue; 211 } 212 213 Instruction *NewInst = II->clone(); 214 if (II->hasName()) 215 NewInst->setName(II->getName()+NameSuffix); 216 NewBB->getInstList().push_back(NewInst); 217 ValueMap[II] = NewInst; // Add instruction map to value. 218 219 hasCalls |= isa<CallInst>(II); 220 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 221 if (isa<ConstantInt>(AI->getArraySize())) 222 hasStaticAllocas = true; 223 else 224 hasDynamicAllocas = true; 225 } 226 } 227 228 // Finally, clone over the terminator. 229 const TerminatorInst *OldTI = BB->getTerminator(); 230 bool TerminatorDone = false; 231 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) { 232 if (BI->isConditional()) { 233 // If the condition was a known constant in the callee... 234 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition()); 235 // Or is a known constant in the caller... 236 if (Cond == 0) 237 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]); 238 239 // Constant fold to uncond branch! 240 if (Cond) { 241 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue()); 242 ValueMap[OldTI] = new BranchInst(Dest, NewBB); 243 CloneBlock(Dest); 244 TerminatorDone = true; 245 } 246 } 247 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) { 248 // If switching on a value known constant in the caller. 249 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition()); 250 if (Cond == 0) // Or known constant after constant prop in the callee... 251 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]); 252 if (Cond) { // Constant fold to uncond branch! 253 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond)); 254 ValueMap[OldTI] = new BranchInst(Dest, NewBB); 255 CloneBlock(Dest); 256 TerminatorDone = true; 257 } 258 } 259 260 if (!TerminatorDone) { 261 Instruction *NewInst = OldTI->clone(); 262 if (OldTI->hasName()) 263 NewInst->setName(OldTI->getName()+NameSuffix); 264 NewBB->getInstList().push_back(NewInst); 265 ValueMap[OldTI] = NewInst; // Add instruction map to value. 266 267 // Recursively clone any reachable successor blocks. 268 const TerminatorInst *TI = BB->getTerminator(); 269 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 270 CloneBlock(TI->getSuccessor(i)); 271 } 272 273 if (CodeInfo) { 274 CodeInfo->ContainsCalls |= hasCalls; 275 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI); 276 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 277 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 278 BB != &BB->getParent()->front(); 279 } 280 281 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator())) 282 Returns.push_back(RI); 283} 284 285/// ConstantFoldMappedInstruction - Constant fold the specified instruction, 286/// mapping its operands through ValueMap if they are available. 287Constant *PruningFunctionCloner:: 288ConstantFoldMappedInstruction(const Instruction *I) { 289 SmallVector<Constant*, 8> Ops; 290 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 291 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i), 292 ValueMap))) 293 Ops.push_back(Op); 294 else 295 return 0; // All operands not constant! 296 297 return ConstantFoldInstOperands(I, &Ops[0], Ops.size(), TD); 298} 299 300/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto, 301/// except that it does some simple constant prop and DCE on the fly. The 302/// effect of this is to copy significantly less code in cases where (for 303/// example) a function call with constant arguments is inlined, and those 304/// constant arguments cause a significant amount of code in the callee to be 305/// dead. Since this doesn't produce an exactly copy of the input, it can't be 306/// used for things like CloneFunction or CloneModule. 307void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 308 DenseMap<const Value*, Value*> &ValueMap, 309 std::vector<ReturnInst*> &Returns, 310 const char *NameSuffix, 311 ClonedCodeInfo *CodeInfo, 312 const TargetData *TD) { 313 assert(NameSuffix && "NameSuffix cannot be null!"); 314 315#ifndef NDEBUG 316 for (Function::const_arg_iterator II = OldFunc->arg_begin(), 317 E = OldFunc->arg_end(); II != E; ++II) 318 assert(ValueMap.count(II) && "No mapping from source argument specified!"); 319#endif 320 321 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns, 322 NameSuffix, CodeInfo, TD); 323 324 // Clone the entry block, and anything recursively reachable from it. 325 PFC.CloneBlock(&OldFunc->getEntryBlock()); 326 327 // Loop over all of the basic blocks in the old function. If the block was 328 // reachable, we have cloned it and the old block is now in the value map: 329 // insert it into the new function in the right order. If not, ignore it. 330 // 331 // Defer PHI resolution until rest of function is resolved. 332 std::vector<const PHINode*> PHIToResolve; 333 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 334 BI != BE; ++BI) { 335 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]); 336 if (NewBB == 0) continue; // Dead block. 337 338 // Add the new block to the new function. 339 NewFunc->getBasicBlockList().push_back(NewBB); 340 341 // Loop over all of the instructions in the block, fixing up operand 342 // references as we go. This uses ValueMap to do all the hard work. 343 // 344 BasicBlock::iterator I = NewBB->begin(); 345 346 // Handle PHI nodes specially, as we have to remove references to dead 347 // blocks. 348 if (PHINode *PN = dyn_cast<PHINode>(I)) { 349 // Skip over all PHI nodes, remembering them for later. 350 BasicBlock::const_iterator OldI = BI->begin(); 351 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) 352 PHIToResolve.push_back(cast<PHINode>(OldI)); 353 } 354 355 // Otherwise, remap the rest of the instructions normally. 356 for (; I != NewBB->end(); ++I) 357 RemapInstruction(I, ValueMap); 358 } 359 360 // Defer PHI resolution until rest of function is resolved, PHI resolution 361 // requires the CFG to be up-to-date. 362 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) { 363 const PHINode *OPN = PHIToResolve[phino]; 364 unsigned NumPreds = OPN->getNumIncomingValues(); 365 const BasicBlock *OldBB = OPN->getParent(); 366 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]); 367 368 // Map operands for blocks that are live and remove operands for blocks 369 // that are dead. 370 for (; phino != PHIToResolve.size() && 371 PHIToResolve[phino]->getParent() == OldBB; ++phino) { 372 OPN = PHIToResolve[phino]; 373 PHINode *PN = cast<PHINode>(ValueMap[OPN]); 374 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) { 375 if (BasicBlock *MappedBlock = 376 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) { 377 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap); 378 assert(InVal && "Unknown input value?"); 379 PN->setIncomingValue(pred, InVal); 380 PN->setIncomingBlock(pred, MappedBlock); 381 } else { 382 PN->removeIncomingValue(pred, false); 383 --pred, --e; // Revisit the next entry. 384 } 385 } 386 } 387 388 // The loop above has removed PHI entries for those blocks that are dead 389 // and has updated others. However, if a block is live (i.e. copied over) 390 // but its terminator has been changed to not go to this block, then our 391 // phi nodes will have invalid entries. Update the PHI nodes in this 392 // case. 393 PHINode *PN = cast<PHINode>(NewBB->begin()); 394 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB)); 395 if (NumPreds != PN->getNumIncomingValues()) { 396 assert(NumPreds < PN->getNumIncomingValues()); 397 // Count how many times each predecessor comes to this block. 398 std::map<BasicBlock*, unsigned> PredCount; 399 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB); 400 PI != E; ++PI) 401 --PredCount[*PI]; 402 403 // Figure out how many entries to remove from each PHI. 404 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 405 ++PredCount[PN->getIncomingBlock(i)]; 406 407 // At this point, the excess predecessor entries are positive in the 408 // map. Loop over all of the PHIs and remove excess predecessor 409 // entries. 410 BasicBlock::iterator I = NewBB->begin(); 411 for (; (PN = dyn_cast<PHINode>(I)); ++I) { 412 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(), 413 E = PredCount.end(); PCI != E; ++PCI) { 414 BasicBlock *Pred = PCI->first; 415 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove) 416 PN->removeIncomingValue(Pred, false); 417 } 418 } 419 } 420 421 // If the loops above have made these phi nodes have 0 or 1 operand, 422 // replace them with undef or the input value. We must do this for 423 // correctness, because 0-operand phis are not valid. 424 PN = cast<PHINode>(NewBB->begin()); 425 if (PN->getNumIncomingValues() == 0) { 426 BasicBlock::iterator I = NewBB->begin(); 427 BasicBlock::const_iterator OldI = OldBB->begin(); 428 while ((PN = dyn_cast<PHINode>(I++))) { 429 Value *NV = UndefValue::get(PN->getType()); 430 PN->replaceAllUsesWith(NV); 431 assert(ValueMap[OldI] == PN && "ValueMap mismatch"); 432 ValueMap[OldI] = NV; 433 PN->eraseFromParent(); 434 ++OldI; 435 } 436 } 437 // NOTE: We cannot eliminate single entry phi nodes here, because of 438 // ValueMap. Single entry phi nodes can have multiple ValueMap entries 439 // pointing at them. Thus, deleting one would require scanning the ValueMap 440 // to update any entries in it that would require that. This would be 441 // really slow. 442 } 443 444 // Now that the inlined function body has been fully constructed, go through 445 // and zap unconditional fall-through branches. This happen all the time when 446 // specializing code: code specialization turns conditional branches into 447 // uncond branches, and this code folds them. 448 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]); 449 while (I != NewFunc->end()) { 450 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator()); 451 if (!BI || BI->isConditional()) { ++I; continue; } 452 453 // Note that we can't eliminate uncond branches if the destination has 454 // single-entry PHI nodes. Eliminating the single-entry phi nodes would 455 // require scanning the ValueMap to update any entries that point to the phi 456 // node. 457 BasicBlock *Dest = BI->getSuccessor(0); 458 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) { 459 ++I; continue; 460 } 461 462 // We know all single-entry PHI nodes in the inlined function have been 463 // removed, so we just need to splice the blocks. 464 BI->eraseFromParent(); 465 466 // Move all the instructions in the succ to the pred. 467 I->getInstList().splice(I->end(), Dest->getInstList()); 468 469 // Make all PHI nodes that referred to Dest now refer to I as their source. 470 Dest->replaceAllUsesWith(I); 471 472 // Remove the dest block. 473 Dest->eraseFromParent(); 474 475 // Do not increment I, iteratively merge all things this block branches to. 476 } 477} 478