CloneFunction.cpp revision 79066fa6acce02c97c714a5a6e151ed8a249721c
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 "ValueMapper.h" 23#include "llvm/Analysis/ConstantFolding.h" 24#include "llvm/ADT/SmallVector.h" 25using namespace llvm; 26 27// CloneBasicBlock - See comments in Cloning.h 28BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB, 29 std::map<const Value*, Value*> &ValueMap, 30 const char *NameSuffix, Function *F, 31 ClonedCodeInfo *CodeInfo) { 32 BasicBlock *NewBB = new BasicBlock("", F); 33 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 34 35 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 36 37 // Loop over all instructions, and copy them over. 38 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); 39 II != IE; ++II) { 40 Instruction *NewInst = II->clone(); 41 if (II->hasName()) 42 NewInst->setName(II->getName()+NameSuffix); 43 NewBB->getInstList().push_back(NewInst); 44 ValueMap[II] = NewInst; // Add instruction map to value. 45 46 hasCalls |= isa<CallInst>(II); 47 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 48 if (isa<ConstantInt>(AI->getArraySize())) 49 hasStaticAllocas = true; 50 else 51 hasDynamicAllocas = true; 52 } 53 } 54 55 if (CodeInfo) { 56 CodeInfo->ContainsCalls |= hasCalls; 57 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator()); 58 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 59 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 60 BB != &BB->getParent()->front(); 61 } 62 return NewBB; 63} 64 65// Clone OldFunc into NewFunc, transforming the old arguments into references to 66// ArgMap values. 67// 68void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc, 69 std::map<const Value*, Value*> &ValueMap, 70 std::vector<ReturnInst*> &Returns, 71 const char *NameSuffix, ClonedCodeInfo *CodeInfo) { 72 assert(NameSuffix && "NameSuffix cannot be null!"); 73 74#ifndef NDEBUG 75 for (Function::const_arg_iterator I = OldFunc->arg_begin(), 76 E = OldFunc->arg_end(); I != E; ++I) 77 assert(ValueMap.count(I) && "No mapping from source argument specified!"); 78#endif 79 80 // Loop over all of the basic blocks in the function, cloning them as 81 // appropriate. Note that we save BE this way in order to handle cloning of 82 // recursive functions into themselves. 83 // 84 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 85 BI != BE; ++BI) { 86 const BasicBlock &BB = *BI; 87 88 // Create a new basic block and copy instructions into it! 89 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc, 90 CodeInfo); 91 ValueMap[&BB] = CBB; // Add basic block mapping. 92 93 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator())) 94 Returns.push_back(RI); 95 } 96 97 // Loop over all of the instructions in the function, fixing up operand 98 // references as we go. This uses ValueMap to do all the hard work. 99 // 100 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]), 101 BE = NewFunc->end(); BB != BE; ++BB) 102 // Loop over all instructions, fixing each one as we find it... 103 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II) 104 RemapInstruction(II, ValueMap); 105} 106 107/// CloneFunction - Return a copy of the specified function, but without 108/// embedding the function into another module. Also, any references specified 109/// in the ValueMap are changed to refer to their mapped value instead of the 110/// original one. If any of the arguments to the function are in the ValueMap, 111/// the arguments are deleted from the resultant function. The ValueMap is 112/// updated to include mappings from all of the instructions and basicblocks in 113/// the function from their old to new values. 114/// 115Function *llvm::CloneFunction(const Function *F, 116 std::map<const Value*, Value*> &ValueMap, 117 ClonedCodeInfo *CodeInfo) { 118 std::vector<const Type*> ArgTypes; 119 120 // The user might be deleting arguments to the function by specifying them in 121 // the ValueMap. If so, we need to not add the arguments to the arg ty vector 122 // 123 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 124 I != E; ++I) 125 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet? 126 ArgTypes.push_back(I->getType()); 127 128 // Create a new function type... 129 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(), 130 ArgTypes, F->getFunctionType()->isVarArg()); 131 132 // Create the new function... 133 Function *NewF = new Function(FTy, F->getLinkage(), F->getName()); 134 135 // Loop over the arguments, copying the names of the mapped arguments over... 136 Function::arg_iterator DestI = NewF->arg_begin(); 137 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); 138 I != E; ++I) 139 if (ValueMap.count(I) == 0) { // Is this argument preserved? 140 DestI->setName(I->getName()); // Copy the name over... 141 ValueMap[I] = DestI++; // Add mapping to ValueMap 142 } 143 144 std::vector<ReturnInst*> Returns; // Ignore returns cloned... 145 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo); 146 return NewF; 147} 148 149 150 151namespace { 152 /// PruningFunctionCloner - This class is a private class used to implement 153 /// the CloneAndPruneFunctionInto method. 154 struct PruningFunctionCloner { 155 Function *NewFunc; 156 const Function *OldFunc; 157 std::map<const Value*, Value*> &ValueMap; 158 std::vector<ReturnInst*> &Returns; 159 const char *NameSuffix; 160 ClonedCodeInfo *CodeInfo; 161 const TargetData *TD; 162 163 public: 164 PruningFunctionCloner(Function *newFunc, const Function *oldFunc, 165 std::map<const Value*, Value*> &valueMap, 166 std::vector<ReturnInst*> &returns, 167 const char *nameSuffix, 168 ClonedCodeInfo *codeInfo, 169 const TargetData *td) 170 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns), 171 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) { 172 } 173 174 /// CloneBlock - The specified block is found to be reachable, clone it and 175 /// anything that it can reach. 176 void CloneBlock(const BasicBlock *BB); 177 178 public: 179 /// ConstantFoldMappedInstruction - Constant fold the specified instruction, 180 /// mapping its operands through ValueMap if they are available. 181 Constant *ConstantFoldMappedInstruction(const Instruction *I); 182 }; 183} 184 185/// CloneBlock - The specified block is found to be reachable, clone it and 186/// anything that it can reach. 187void PruningFunctionCloner::CloneBlock(const BasicBlock *BB) { 188 Value *&BBEntry = ValueMap[BB]; 189 190 // Have we already cloned this block? 191 if (BBEntry) return; 192 193 // Nope, clone it now. 194 BasicBlock *NewBB; 195 BBEntry = NewBB = new BasicBlock(); 196 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); 197 198 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; 199 200 // Loop over all instructions, and copy them over, DCE'ing as we go. This 201 // loop doesn't include the terminator. 202 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end(); 203 II != IE; ++II) { 204 // If this instruction constant folds, don't bother cloning the instruction, 205 // instead, just add the constant to the value map. 206 if (Constant *C = ConstantFoldMappedInstruction(II)) { 207 ValueMap[II] = C; 208 continue; 209 } 210 211 Instruction *NewInst = II->clone(); 212 if (II->hasName()) 213 NewInst->setName(II->getName()+NameSuffix); 214 NewBB->getInstList().push_back(NewInst); 215 ValueMap[II] = NewInst; // Add instruction map to value. 216 217 hasCalls |= isa<CallInst>(II); 218 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) { 219 if (isa<ConstantInt>(AI->getArraySize())) 220 hasStaticAllocas = true; 221 else 222 hasDynamicAllocas = true; 223 } 224 } 225 226 // Finally, clone over the terminator. 227 const TerminatorInst *OldTI = BB->getTerminator(); 228 bool TerminatorDone = false; 229 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) { 230 if (BI->isConditional()) { 231 // If the condition was a known constant in the callee... 232 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition()); 233 // Or is a known constant in the caller... 234 if (Cond == 0) 235 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]); 236 237 // Constant fold to uncond branch! 238 if (Cond) { 239 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue()); 240 ValueMap[OldTI] = new BranchInst(Dest, NewBB); 241 CloneBlock(Dest); 242 TerminatorDone = true; 243 } 244 } 245 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) { 246 // If switching on a value known constant in the caller. 247 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition()); 248 if (Cond == 0) // Or known constant after constant prop in the callee... 249 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]); 250 if (Cond) { // Constant fold to uncond branch! 251 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond)); 252 ValueMap[OldTI] = new BranchInst(Dest, NewBB); 253 CloneBlock(Dest); 254 TerminatorDone = true; 255 } 256 } 257 258 if (!TerminatorDone) { 259 Instruction *NewInst = OldTI->clone(); 260 if (OldTI->hasName()) 261 NewInst->setName(OldTI->getName()+NameSuffix); 262 NewBB->getInstList().push_back(NewInst); 263 ValueMap[OldTI] = NewInst; // Add instruction map to value. 264 265 // Recursively clone any reachable successor blocks. 266 const TerminatorInst *TI = BB->getTerminator(); 267 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 268 CloneBlock(TI->getSuccessor(i)); 269 } 270 271 if (CodeInfo) { 272 CodeInfo->ContainsCalls |= hasCalls; 273 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI); 274 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; 275 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && 276 BB != &BB->getParent()->front(); 277 } 278 279 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator())) 280 Returns.push_back(RI); 281} 282 283/// ConstantFoldMappedInstruction - Constant fold the specified instruction, 284/// mapping its operands through ValueMap if they are available. 285Constant *PruningFunctionCloner:: 286ConstantFoldMappedInstruction(const Instruction *I) { 287 SmallVector<Constant*, 8> Ops; 288 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 289 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i), 290 ValueMap))) 291 Ops.push_back(Op); 292 else 293 return 0; // All operands not constant! 294 295 return ConstantFoldInstOperands(I, &Ops[0], Ops.size(), TD); 296} 297 298/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto, 299/// except that it does some simple constant prop and DCE on the fly. The 300/// effect of this is to copy significantly less code in cases where (for 301/// example) a function call with constant arguments is inlined, and those 302/// constant arguments cause a significant amount of code in the callee to be 303/// dead. Since this doesn't produce an exactly copy of the input, it can't be 304/// used for things like CloneFunction or CloneModule. 305void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, 306 std::map<const Value*, Value*> &ValueMap, 307 std::vector<ReturnInst*> &Returns, 308 const char *NameSuffix, 309 ClonedCodeInfo *CodeInfo, 310 const TargetData *TD) { 311 assert(NameSuffix && "NameSuffix cannot be null!"); 312 313#ifndef NDEBUG 314 for (Function::const_arg_iterator II = OldFunc->arg_begin(), 315 E = OldFunc->arg_end(); II != E; ++II) 316 assert(ValueMap.count(II) && "No mapping from source argument specified!"); 317#endif 318 319 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns, 320 NameSuffix, CodeInfo, TD); 321 322 // Clone the entry block, and anything recursively reachable from it. 323 PFC.CloneBlock(&OldFunc->getEntryBlock()); 324 325 // Loop over all of the basic blocks in the old function. If the block was 326 // reachable, we have cloned it and the old block is now in the value map: 327 // insert it into the new function in the right order. If not, ignore it. 328 // 329 // Defer PHI resolution until rest of function is resolved. 330 std::vector<const PHINode*> PHIToResolve; 331 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); 332 BI != BE; ++BI) { 333 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]); 334 if (NewBB == 0) continue; // Dead block. 335 336 // Add the new block to the new function. 337 NewFunc->getBasicBlockList().push_back(NewBB); 338 339 // Loop over all of the instructions in the block, fixing up operand 340 // references as we go. This uses ValueMap to do all the hard work. 341 // 342 BasicBlock::iterator I = NewBB->begin(); 343 344 // Handle PHI nodes specially, as we have to remove references to dead 345 // blocks. 346 if (PHINode *PN = dyn_cast<PHINode>(I)) { 347 // Skip over all PHI nodes, remembering them for later. 348 BasicBlock::const_iterator OldI = BI->begin(); 349 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) 350 PHIToResolve.push_back(cast<PHINode>(OldI)); 351 } 352 353 // Otherwise, remap the rest of the instructions normally. 354 for (; I != NewBB->end(); ++I) 355 RemapInstruction(I, ValueMap); 356 } 357 358 // Defer PHI resolution until rest of function is resolved, PHI resolution 359 // requires the CFG to be up-to-date. 360 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) { 361 const PHINode *OPN = PHIToResolve[phino]; 362 unsigned NumPreds = OPN->getNumIncomingValues(); 363 const BasicBlock *OldBB = OPN->getParent(); 364 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]); 365 366 // Map operands for blocks that are live and remove operands for blocks 367 // that are dead. 368 for (; phino != PHIToResolve.size() && 369 PHIToResolve[phino]->getParent() == OldBB; ++phino) { 370 OPN = PHIToResolve[phino]; 371 PHINode *PN = cast<PHINode>(ValueMap[OPN]); 372 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) { 373 if (BasicBlock *MappedBlock = 374 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) { 375 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap); 376 assert(InVal && "Unknown input value?"); 377 PN->setIncomingValue(pred, InVal); 378 PN->setIncomingBlock(pred, MappedBlock); 379 } else { 380 PN->removeIncomingValue(pred, false); 381 --pred, --e; // Revisit the next entry. 382 } 383 } 384 } 385 386 // The loop above has removed PHI entries for those blocks that are dead 387 // and has updated others. However, if a block is live (i.e. copied over) 388 // but its terminator has been changed to not go to this block, then our 389 // phi nodes will have invalid entries. Update the PHI nodes in this 390 // case. 391 PHINode *PN = cast<PHINode>(NewBB->begin()); 392 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB)); 393 if (NumPreds != PN->getNumIncomingValues()) { 394 assert(NumPreds < PN->getNumIncomingValues()); 395 // Count how many times each predecessor comes to this block. 396 std::map<BasicBlock*, unsigned> PredCount; 397 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB); 398 PI != E; ++PI) 399 --PredCount[*PI]; 400 401 // Figure out how many entries to remove from each PHI. 402 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 403 ++PredCount[PN->getIncomingBlock(i)]; 404 405 // At this point, the excess predecessor entries are positive in the 406 // map. Loop over all of the PHIs and remove excess predecessor 407 // entries. 408 BasicBlock::iterator I = NewBB->begin(); 409 for (; (PN = dyn_cast<PHINode>(I)); ++I) { 410 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(), 411 E = PredCount.end(); PCI != E; ++PCI) { 412 BasicBlock *Pred = PCI->first; 413 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove) 414 PN->removeIncomingValue(Pred, false); 415 } 416 } 417 } 418 419 // If the loops above have made these phi nodes have 0 or 1 operand, 420 // replace them with undef or the input value. We must do this for 421 // correctness, because 0-operand phis are not valid. 422 PN = cast<PHINode>(NewBB->begin()); 423 if (PN->getNumIncomingValues() == 0) { 424 BasicBlock::iterator I = NewBB->begin(); 425 BasicBlock::const_iterator OldI = OldBB->begin(); 426 while ((PN = dyn_cast<PHINode>(I++))) { 427 Value *NV = UndefValue::get(PN->getType()); 428 PN->replaceAllUsesWith(NV); 429 assert(ValueMap[OldI] == PN && "ValueMap mismatch"); 430 ValueMap[OldI] = NV; 431 PN->eraseFromParent(); 432 ++OldI; 433 } 434 } else if (PN->getNumIncomingValues() == 1) { 435 BasicBlock::iterator I = NewBB->begin(); 436 BasicBlock::const_iterator OldI = OldBB->begin(); 437 while ((PN = dyn_cast<PHINode>(I++))) { 438 Value *NV = PN->getIncomingValue(0); 439 PN->replaceAllUsesWith(NV); 440 assert(ValueMap[OldI] == PN && "ValueMap mismatch"); 441 ValueMap[OldI] = NV; 442 PN->eraseFromParent(); 443 ++OldI; 444 } 445 } 446 } 447 448 // Now that the inlined function body has been fully constructed, go through 449 // and zap unconditional fall-through branches. This happen all the time when 450 // specializing code: code specialization turns conditional branches into 451 // uncond branches, and this code folds them. 452 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]); 453 while (I != NewFunc->end()) { 454 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator()); 455 if (!BI || BI->isConditional()) { ++I; continue; } 456 457 BasicBlock *Dest = BI->getSuccessor(0); 458 if (!Dest->getSinglePredecessor()) { ++I; continue; } 459 460 // We know all single-entry PHI nodes in the inlined function have been 461 // removed, so we just need to splice the blocks. 462 BI->eraseFromParent(); 463 464 // Move all the instructions in the succ to the pred. 465 I->getInstList().splice(I->end(), Dest->getInstList()); 466 467 // Make all PHI nodes that referred to Dest now refer to I as their source. 468 Dest->replaceAllUsesWith(I); 469 470 // Remove the dest block. 471 Dest->eraseFromParent(); 472 473 // Do not increment I, iteratively merge all things this block branches to. 474 } 475} 476