lib/Transforms/Utils/CloneFunction.cpp

   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/Transforms/Utils/Local.h"
  24 using namespace llvm;
  25
  26 // CloneBasicBlock - See comments in Cloning.h
  27 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
  28                                   std::map<const Value*, Value*> &ValueMap,
  29                                   const char *NameSuffix, Function *F,
  30                                   ClonedCodeInfo *CodeInfo) {
  31   BasicBlock *NewBB = new BasicBlock("", F);
  32   if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
  33
  34   bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
  35
  36   // Loop over all instructions, and copy them over.
  37   for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
  38        II != IE; ++II) {
  39     Instruction *NewInst = II->clone();
  40     if (II->hasName())
  41       NewInst->setName(II->getName()+NameSuffix);
  42     NewBB->getInstList().push_back(NewInst);
  43     ValueMap[II] = NewInst;                // Add instruction map to value.
  44
  45     hasCalls |= isa<CallInst>(II);
  46     if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
  47       if (isa<ConstantInt>(AI->getArraySize()))
  48         hasStaticAllocas = true;
  49       else
  50         hasDynamicAllocas = true;
  51     }
  52   }
  53
  54   if (CodeInfo) {
  55     CodeInfo->ContainsCalls          |= hasCalls;
  56     CodeInfo->ContainsUnwinds        |= isa<UnwindInst>(BB->getTerminator());
  57     CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
  58     CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
  59                                         BB != &BB->getParent()->front();
  60   }
  61   return NewBB;
  62 }
  63
  64 // Clone OldFunc into NewFunc, transforming the old arguments into references to
  65 // ArgMap values.
  66 //
  67 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
  68                              std::map<const Value*, Value*> &ValueMap,
  69                              std::vector<ReturnInst*> &Returns,
  70                              const char *NameSuffix, ClonedCodeInfo *CodeInfo) {
  71   assert(NameSuffix && "NameSuffix cannot be null!");
  72
  73 #ifndef NDEBUG
  74   for (Function::const_arg_iterator I = OldFunc->arg_begin(),
  75        E = OldFunc->arg_end(); I != E; ++I)
  76     assert(ValueMap.count(I) && "No mapping from source argument specified!");
  77 #endif
  78
  79   // Loop over all of the basic blocks in the function, cloning them as
  80   // appropriate.  Note that we save BE this way in order to handle cloning of
  81   // recursive functions into themselves.
  82   //
  83   for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
  84        BI != BE; ++BI) {
  85     const BasicBlock &BB = *BI;
  86
  87     // Create a new basic block and copy instructions into it!
  88     BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
  89                                       CodeInfo);
  90     ValueMap[&BB] = CBB;                       // Add basic block mapping.
  91
  92     if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
  93       Returns.push_back(RI);
  94   }
  95
  96   // Loop over all of the instructions in the function, fixing up operand
  97   // references as we go.  This uses ValueMap to do all the hard work.
  98   //
  99   for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
 100          BE = NewFunc->end(); BB != BE; ++BB)
 101     // Loop over all instructions, fixing each one as we find it...
 102     for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
 103       RemapInstruction(II, ValueMap);
 104 }
 105
 106 /// CloneFunction - Return a copy of the specified function, but without
 107 /// embedding the function into another module.  Also, any references specified
 108 /// in the ValueMap are changed to refer to their mapped value instead of the
 109 /// original one.  If any of the arguments to the function are in the ValueMap,
 110 /// the arguments are deleted from the resultant function.  The ValueMap is
 111 /// updated to include mappings from all of the instructions and basicblocks in
 112 /// the function from their old to new values.
 113 ///
 114 Function *llvm::CloneFunction(const Function *F,
 115                               std::map<const Value*, Value*> &ValueMap,
 116                               ClonedCodeInfo *CodeInfo) {
 117   std::vector<const Type*> ArgTypes;
 118
 119   // The user might be deleting arguments to the function by specifying them in
 120   // the ValueMap.  If so, we need to not add the arguments to the arg ty vector
 121   //
 122   for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
 123        I != E; ++I)
 124     if (ValueMap.count(I) == 0)  // Haven't mapped the argument to anything yet?
 125       ArgTypes.push_back(I->getType());
 126
 127   // Create a new function type...
 128   FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
 129                                     ArgTypes, F->getFunctionType()->isVarArg());
 130
 131   // Create the new function...
 132   Function *NewF = new Function(FTy, F->getLinkage(), F->getName());
 133
 134   // Loop over the arguments, copying the names of the mapped arguments over...
 135   Function::arg_iterator DestI = NewF->arg_begin();
 136   for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
 137        I != E; ++I)
 138     if (ValueMap.count(I) == 0) {   // Is this argument preserved?
 139       DestI->setName(I->getName()); // Copy the name over...
 140       ValueMap[I] = DestI++;        // Add mapping to ValueMap
 141     }
 142
 143   std::vector<ReturnInst*> Returns;  // Ignore returns cloned...
 144   CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
 145   return NewF;
 146 }
 147
 148
 149
 150 namespace {
 151   /// PruningFunctionCloner - This class is a private class used to implement
 152   /// the CloneAndPruneFunctionInto method.
 153   struct PruningFunctionCloner {
 154     Function *NewFunc;
 155     const Function *OldFunc;
 156     std::map<const Value*, Value*> &ValueMap;
 157     std::vector<ReturnInst*> &Returns;
 158     const char *NameSuffix;
 159     ClonedCodeInfo *CodeInfo;
 160
 161   public:
 162     PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
 163                           std::map<const Value*, Value*> &valueMap,
 164                           std::vector<ReturnInst*> &returns,
 165                           const char *nameSuffix,
 166                           ClonedCodeInfo *codeInfo)
 167     : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
 168       NameSuffix(nameSuffix), CodeInfo(codeInfo) {
 169     }
 170
 171     /// CloneBlock - The specified block is found to be reachable, clone it and
 172     /// anything that it can reach.
 173     void CloneBlock(const BasicBlock *BB);
 174
 175   public:
 176     /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
 177     /// mapping its operands through ValueMap if they are available.
 178     Constant *ConstantFoldMappedInstruction(const Instruction *I);
 179   };
 180 }
 181
 182 /// CloneBlock - The specified block is found to be reachable, clone it and
 183 /// anything that it can reach.
 184 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB) {
 185   Value *&BBEntry = ValueMap[BB];
 186
 187   // Have we already cloned this block?
 188   if (BBEntry) return;
 189
 190   // Nope, clone it now.
 191   BasicBlock *NewBB;
 192   BBEntry = NewBB = new BasicBlock();
 193   if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
 194
 195   bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
 196
 197   // Loop over all instructions, and copy them over, DCE'ing as we go.  This
 198   // loop doesn't include the terminator.
 199   for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
 200        II != IE; ++II) {
 201     // If this instruction constant folds, don't bother cloning the instruction,
 202     // instead, just add the constant to the value map.
 203     if (Constant *C = ConstantFoldMappedInstruction(II)) {
 204       ValueMap[II] = C;
 205       continue;
 206     }
 207
 208     Instruction *NewInst = II->clone();
 209     if (II->hasName())
 210       NewInst->setName(II->getName()+NameSuffix);
 211     NewBB->getInstList().push_back(NewInst);
 212     ValueMap[II] = NewInst;                // Add instruction map to value.
 213
 214     hasCalls |= isa<CallInst>(II);
 215     if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
 216       if (isa<ConstantInt>(AI->getArraySize()))
 217         hasStaticAllocas = true;
 218       else
 219         hasDynamicAllocas = true;
 220     }
 221   }
 222
 223   // Finally, clone over the terminator.
 224   const TerminatorInst *OldTI = BB->getTerminator();
 225   bool TerminatorDone = false;
 226   if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
 227     if (BI->isConditional()) {
 228       // If the condition was a known constant in the callee...
 229       ConstantBool *Cond = dyn_cast<ConstantBool>(BI->getCondition());
 230       if (Cond == 0)  // Or is a known constant in the caller...
 231         Cond = dyn_cast_or_null<ConstantBool>(ValueMap[BI->getCondition()]);
 232       if (Cond) {     // Constant fold to uncond branch!
 233         BasicBlock *Dest = BI->getSuccessor(!Cond->getValue());
 234         ValueMap[OldTI] = new BranchInst(Dest, NewBB);
 235         CloneBlock(Dest);
 236         TerminatorDone = true;
 237       }
 238     }
 239   } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
 240     // If switching on a value known constant in the caller.
 241     ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
 242     if (Cond == 0)  // Or known constant after constant prop in the callee...
 243       Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
 244     if (Cond) {     // Constant fold to uncond branch!
 245       BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
 246       ValueMap[OldTI] = new BranchInst(Dest, NewBB);
 247       CloneBlock(Dest);
 248       TerminatorDone = true;
 249     }
 250   }
 251
 252   if (!TerminatorDone) {
 253     Instruction *NewInst = OldTI->clone();
 254     if (OldTI->hasName())
 255       NewInst->setName(OldTI->getName()+NameSuffix);
 256     NewBB->getInstList().push_back(NewInst);
 257     ValueMap[OldTI] = NewInst;             // Add instruction map to value.
 258
 259     // Recursively clone any reachable successor blocks.
 260     const TerminatorInst *TI = BB->getTerminator();
 261     for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
 262       CloneBlock(TI->getSuccessor(i));
 263   }
 264
 265   if (CodeInfo) {
 266     CodeInfo->ContainsCalls          |= hasCalls;
 267     CodeInfo->ContainsUnwinds        |= isa<UnwindInst>(OldTI);
 268     CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
 269     CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
 270       BB != &BB->getParent()->front();
 271   }
 272
 273   if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
 274     Returns.push_back(RI);
 275 }
 276
 277 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
 278 /// mapping its operands through ValueMap if they are available.
 279 Constant *PruningFunctionCloner::
 280 ConstantFoldMappedInstruction(const Instruction *I) {
 281   if (isa<BinaryOperator>(I) || isa<ShiftInst>(I)) {
 282     if (Constant *Op0 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(0),
 283                                                             ValueMap)))
 284       if (Constant *Op1 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(1),
 285                                                               ValueMap)))
 286         return ConstantExpr::get(I->getOpcode(), Op0, Op1);
 287     return 0;
 288   }
 289
 290   std::vector<Constant*> Ops;
 291   for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
 292     if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
 293                                                            ValueMap)))
 294       Ops.push_back(Op);
 295     else
 296       return 0;  // All operands not constant!
 297
 298   return ConstantFoldInstOperands(I->getOpcode(), I->getType(), Ops);
 299 }
 300
 301 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
 302 /// except that it does some simple constant prop and DCE on the fly.  The
 303 /// effect of this is to copy significantly less code in cases where (for
 304 /// example) a function call with constant arguments is inlined, and those
 305 /// constant arguments cause a significant amount of code in the callee to be
 306 /// dead.  Since this doesn't produce an exactly copy of the input, it can't be
 307 /// used for things like CloneFunction or CloneModule.
 308 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
 309                                      std::map<const Value*, Value*> &ValueMap,
 310                                      std::vector<ReturnInst*> &Returns,
 311                                      const char *NameSuffix,
 312                                      ClonedCodeInfo *CodeInfo) {
 313   assert(NameSuffix && "NameSuffix cannot be null!");
 314
 315 #ifndef NDEBUG
 316   for (Function::const_arg_iterator I = OldFunc->arg_begin(),
 317        E = OldFunc->arg_end(); I != E; ++I)
 318     assert(ValueMap.count(I) && "No mapping from source argument specified!");
 319 #endif
 320
 321   PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
 322                             NameSuffix, CodeInfo);
 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
 365     unsigned NumPreds = OPN->getNumIncomingValues();
 366
 367     unsigned BBPHIStart = phino;
 368     const BasicBlock *OldBB = OPN->getParent();
 369     BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
 370
 371     // Map operands for blocks that are live and remove operands for blocks
 372     // that are dead.
 373     for (; phino != PHIToResolve.size() &&
 374          PHIToResolve[phino]->getParent() == OldBB; ++phino) {
 375       OPN = PHIToResolve[phino];
 376       PHINode *PN = cast<PHINode>(ValueMap[OPN]);
 377       for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
 378         if (BasicBlock *MappedBlock =
 379             cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
 380           Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
 381           assert(InVal && "Unknown input value?");
 382           PN->setIncomingValue(pred, InVal);
 383           PN->setIncomingBlock(pred, MappedBlock);
 384         } else {
 385           PN->removeIncomingValue(pred, false);
 386           --pred, --e;  // Revisit the next entry.
 387         }
 388       }
 389     }
 390
 391     // The loop above has removed PHI entries for those blocks that are dead
 392     // and has updated others.  However, if a block is live (i.e. copied over)
 393     // but its terminator has been changed to not go to this block, then our
 394     // phi nodes will have invalid entries.  Update the PHI nodes in this
 395     // case.
 396     PHINode *PN = cast<PHINode>(NewBB->begin());
 397     NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
 398     if (NumPreds != PN->getNumIncomingValues()) {
 399       assert(NumPreds < PN->getNumIncomingValues());
 400       // Count how many times each predecessor comes to this block.
 401       std::map<BasicBlock*, unsigned> PredCount;
 402       for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
 403            PI != E; ++PI)
 404         --PredCount[*PI];
 405
 406       // Figure out how many entries to remove from each PHI.
 407       for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
 408         ++PredCount[PN->getIncomingBlock(i)];
 409
 410       // At this point, the excess predecessor entries are positive in the
 411       // map.  Loop over all of the PHIs and remove excess predecessor
 412       // entries.
 413       BasicBlock::iterator I = NewBB->begin();
 414       for (; (PN = dyn_cast<PHINode>(I)); ++I) {
 415         for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
 416              E = PredCount.end(); PCI != E; ++PCI) {
 417           BasicBlock *Pred     = PCI->first;
 418           for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
 419             PN->removeIncomingValue(Pred, false);
 420         }
 421       }
 422     }
 423
 424     // If the loops above have made these phi nodes have 0 or 1 operand,
 425     // replace them with undef or the input value.  We must do this for
 426     // correctness, because 0-operand phis are not valid.
 427     PN = cast<PHINode>(NewBB->begin());
 428     if (PN->getNumIncomingValues() == 0) {
 429       BasicBlock::iterator I = NewBB->begin();
 430       BasicBlock::const_iterator OldI = OldBB->begin();
 431       while ((PN = dyn_cast<PHINode>(I++))) {
 432         Value *NV = UndefValue::get(PN->getType());
 433         PN->replaceAllUsesWith(NV);
 434         assert(ValueMap[OldI] == PN && "ValueMap mismatch");
 435         ValueMap[OldI] = NV;
 436         PN->eraseFromParent();
 437         ++OldI;
 438       }
 439     } else if (PN->getNumIncomingValues() == 1) {
 440       BasicBlock::iterator I = NewBB->begin();
 441       BasicBlock::const_iterator OldI = OldBB->begin();
 442       while ((PN = dyn_cast<PHINode>(I++))) {
 443         Value *NV = PN->getIncomingValue(0);
 444         PN->replaceAllUsesWith(NV);
 445         assert(ValueMap[OldI] == PN && "ValueMap mismatch");
 446         ValueMap[OldI] = NV;
 447         PN->eraseFromParent();
 448         ++OldI;
 449       }
 450     }
 451   }
 452 }
 453
 454