1 //===- CodeExtractor.cpp - Pull code region into a new 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 interface to tear out a code region, such as an 11 // individual loop or a parallel section, into a new function, replacing it with 12 // a call to the new function. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/Transforms/Utils/CodeExtractor.h" 17 #include "llvm/ADT/STLExtras.h" 18 #include "llvm/ADT/SetVector.h" 19 #include "llvm/ADT/StringExtras.h" 20 #include "llvm/Analysis/LoopInfo.h" 21 #include "llvm/Analysis/RegionInfo.h" 22 #include "llvm/Analysis/RegionIterator.h" 23 #include "llvm/IR/Constants.h" 24 #include "llvm/IR/DerivedTypes.h" 25 #include "llvm/IR/Dominators.h" 26 #include "llvm/IR/Instructions.h" 27 #include "llvm/IR/Intrinsics.h" 28 #include "llvm/IR/LLVMContext.h" 29 #include "llvm/IR/Module.h" 30 #include "llvm/IR/Verifier.h" 31 #include "llvm/Pass.h" 32 #include "llvm/Support/CommandLine.h" 33 #include "llvm/Support/Debug.h" 34 #include "llvm/Support/ErrorHandling.h" 35 #include "llvm/Support/raw_ostream.h" 36 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 37 #include <algorithm> 38 #include <set> 39 using namespace llvm; 40 41 #define DEBUG_TYPE "code-extractor" 42 43 // Provide a command-line option to aggregate function arguments into a struct 44 // for functions produced by the code extractor. This is useful when converting 45 // extracted functions to pthread-based code, as only one argument (void*) can 46 // be passed in to pthread_create(). 47 static cl::opt<bool> 48 AggregateArgsOpt("aggregate-extracted-args", cl::Hidden, 49 cl::desc("Aggregate arguments to code-extracted functions")); 50 51 /// \brief Test whether a block is valid for extraction. 52 static bool isBlockValidForExtraction(const BasicBlock &BB) { 53 // Landing pads must be in the function where they were inserted for cleanup. 54 if (BB.isEHPad()) 55 return false; 56 57 // Don't hoist code containing allocas, invokes, or vastarts. 58 for (BasicBlock::const_iterator I = BB.begin(), E = BB.end(); I != E; ++I) { 59 if (isa<AllocaInst>(I) || isa<InvokeInst>(I)) 60 return false; 61 if (const CallInst *CI = dyn_cast<CallInst>(I)) 62 if (const Function *F = CI->getCalledFunction()) 63 if (F->getIntrinsicID() == Intrinsic::vastart) 64 return false; 65 } 66 67 return true; 68 } 69 70 /// \brief Build a set of blocks to extract if the input blocks are viable. 71 template <typename IteratorT> 72 static SetVector<BasicBlock *> buildExtractionBlockSet(IteratorT BBBegin, 73 IteratorT BBEnd) { 74 SetVector<BasicBlock *> Result; 75 76 assert(BBBegin != BBEnd); 77 78 // Loop over the blocks, adding them to our set-vector, and aborting with an 79 // empty set if we encounter invalid blocks. 80 do { 81 if (!Result.insert(*BBBegin)) 82 llvm_unreachable("Repeated basic blocks in extraction input"); 83 84 if (!isBlockValidForExtraction(**BBBegin)) { 85 Result.clear(); 86 return Result; 87 } 88 } while (++BBBegin != BBEnd); 89 90 #ifndef NDEBUG 91 for (SetVector<BasicBlock *>::iterator I = std::next(Result.begin()), 92 E = Result.end(); 93 I != E; ++I) 94 for (pred_iterator PI = pred_begin(*I), PE = pred_end(*I); 95 PI != PE; ++PI) 96 assert(Result.count(*PI) && 97 "No blocks in this region may have entries from outside the region" 98 " except for the first block!"); 99 #endif 100 101 return Result; 102 } 103 104 /// \brief Helper to call buildExtractionBlockSet with an ArrayRef. 105 static SetVector<BasicBlock *> 106 buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs) { 107 return buildExtractionBlockSet(BBs.begin(), BBs.end()); 108 } 109 110 /// \brief Helper to call buildExtractionBlockSet with a RegionNode. 111 static SetVector<BasicBlock *> 112 buildExtractionBlockSet(const RegionNode &RN) { 113 if (!RN.isSubRegion()) 114 // Just a single BasicBlock. 115 return buildExtractionBlockSet(RN.getNodeAs<BasicBlock>()); 116 117 const Region &R = *RN.getNodeAs<Region>(); 118 119 return buildExtractionBlockSet(R.block_begin(), R.block_end()); 120 } 121 122 CodeExtractor::CodeExtractor(BasicBlock *BB, bool AggregateArgs) 123 : DT(nullptr), AggregateArgs(AggregateArgs||AggregateArgsOpt), 124 Blocks(buildExtractionBlockSet(BB)), NumExitBlocks(~0U) {} 125 126 CodeExtractor::CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT, 127 bool AggregateArgs) 128 : DT(DT), AggregateArgs(AggregateArgs||AggregateArgsOpt), 129 Blocks(buildExtractionBlockSet(BBs)), NumExitBlocks(~0U) {} 130 131 CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs) 132 : DT(&DT), AggregateArgs(AggregateArgs||AggregateArgsOpt), 133 Blocks(buildExtractionBlockSet(L.getBlocks())), NumExitBlocks(~0U) {} 134 135 CodeExtractor::CodeExtractor(DominatorTree &DT, const RegionNode &RN, 136 bool AggregateArgs) 137 : DT(&DT), AggregateArgs(AggregateArgs||AggregateArgsOpt), 138 Blocks(buildExtractionBlockSet(RN)), NumExitBlocks(~0U) {} 139 140 /// definedInRegion - Return true if the specified value is defined in the 141 /// extracted region. 142 static bool definedInRegion(const SetVector<BasicBlock *> &Blocks, Value *V) { 143 if (Instruction *I = dyn_cast<Instruction>(V)) 144 if (Blocks.count(I->getParent())) 145 return true; 146 return false; 147 } 148 149 /// definedInCaller - Return true if the specified value is defined in the 150 /// function being code extracted, but not in the region being extracted. 151 /// These values must be passed in as live-ins to the function. 152 static bool definedInCaller(const SetVector<BasicBlock *> &Blocks, Value *V) { 153 if (isa<Argument>(V)) return true; 154 if (Instruction *I = dyn_cast<Instruction>(V)) 155 if (!Blocks.count(I->getParent())) 156 return true; 157 return false; 158 } 159 160 void CodeExtractor::findInputsOutputs(ValueSet &Inputs, 161 ValueSet &Outputs) const { 162 for (BasicBlock *BB : Blocks) { 163 // If a used value is defined outside the region, it's an input. If an 164 // instruction is used outside the region, it's an output. 165 for (Instruction &II : *BB) { 166 for (User::op_iterator OI = II.op_begin(), OE = II.op_end(); OI != OE; 167 ++OI) 168 if (definedInCaller(Blocks, *OI)) 169 Inputs.insert(*OI); 170 171 for (User *U : II.users()) 172 if (!definedInRegion(Blocks, U)) { 173 Outputs.insert(&II); 174 break; 175 } 176 } 177 } 178 } 179 180 /// severSplitPHINodes - If a PHI node has multiple inputs from outside of the 181 /// region, we need to split the entry block of the region so that the PHI node 182 /// is easier to deal with. 183 void CodeExtractor::severSplitPHINodes(BasicBlock *&Header) { 184 unsigned NumPredsFromRegion = 0; 185 unsigned NumPredsOutsideRegion = 0; 186 187 if (Header != &Header->getParent()->getEntryBlock()) { 188 PHINode *PN = dyn_cast<PHINode>(Header->begin()); 189 if (!PN) return; // No PHI nodes. 190 191 // If the header node contains any PHI nodes, check to see if there is more 192 // than one entry from outside the region. If so, we need to sever the 193 // header block into two. 194 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 195 if (Blocks.count(PN->getIncomingBlock(i))) 196 ++NumPredsFromRegion; 197 else 198 ++NumPredsOutsideRegion; 199 200 // If there is one (or fewer) predecessor from outside the region, we don't 201 // need to do anything special. 202 if (NumPredsOutsideRegion <= 1) return; 203 } 204 205 // Otherwise, we need to split the header block into two pieces: one 206 // containing PHI nodes merging values from outside of the region, and a 207 // second that contains all of the code for the block and merges back any 208 // incoming values from inside of the region. 209 BasicBlock::iterator AfterPHIs = Header->getFirstNonPHI()->getIterator(); 210 BasicBlock *NewBB = Header->splitBasicBlock(AfterPHIs, 211 Header->getName()+".ce"); 212 213 // We only want to code extract the second block now, and it becomes the new 214 // header of the region. 215 BasicBlock *OldPred = Header; 216 Blocks.remove(OldPred); 217 Blocks.insert(NewBB); 218 Header = NewBB; 219 220 // Okay, update dominator sets. The blocks that dominate the new one are the 221 // blocks that dominate TIBB plus the new block itself. 222 if (DT) 223 DT->splitBlock(NewBB); 224 225 // Okay, now we need to adjust the PHI nodes and any branches from within the 226 // region to go to the new header block instead of the old header block. 227 if (NumPredsFromRegion) { 228 PHINode *PN = cast<PHINode>(OldPred->begin()); 229 // Loop over all of the predecessors of OldPred that are in the region, 230 // changing them to branch to NewBB instead. 231 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 232 if (Blocks.count(PN->getIncomingBlock(i))) { 233 TerminatorInst *TI = PN->getIncomingBlock(i)->getTerminator(); 234 TI->replaceUsesOfWith(OldPred, NewBB); 235 } 236 237 // Okay, everything within the region is now branching to the right block, we 238 // just have to update the PHI nodes now, inserting PHI nodes into NewBB. 239 for (AfterPHIs = OldPred->begin(); isa<PHINode>(AfterPHIs); ++AfterPHIs) { 240 PHINode *PN = cast<PHINode>(AfterPHIs); 241 // Create a new PHI node in the new region, which has an incoming value 242 // from OldPred of PN. 243 PHINode *NewPN = PHINode::Create(PN->getType(), 1 + NumPredsFromRegion, 244 PN->getName() + ".ce", &NewBB->front()); 245 NewPN->addIncoming(PN, OldPred); 246 247 // Loop over all of the incoming value in PN, moving them to NewPN if they 248 // are from the extracted region. 249 for (unsigned i = 0; i != PN->getNumIncomingValues(); ++i) { 250 if (Blocks.count(PN->getIncomingBlock(i))) { 251 NewPN->addIncoming(PN->getIncomingValue(i), PN->getIncomingBlock(i)); 252 PN->removeIncomingValue(i); 253 --i; 254 } 255 } 256 } 257 } 258 } 259 260 void CodeExtractor::splitReturnBlocks() { 261 for (BasicBlock *Block : Blocks) 262 if (ReturnInst *RI = dyn_cast<ReturnInst>(Block->getTerminator())) { 263 BasicBlock *New = 264 Block->splitBasicBlock(RI->getIterator(), Block->getName() + ".ret"); 265 if (DT) { 266 // Old dominates New. New node dominates all other nodes dominated 267 // by Old. 268 DomTreeNode *OldNode = DT->getNode(Block); 269 SmallVector<DomTreeNode *, 8> Children(OldNode->begin(), 270 OldNode->end()); 271 272 DomTreeNode *NewNode = DT->addNewBlock(New, Block); 273 274 for (DomTreeNode *I : Children) 275 DT->changeImmediateDominator(I, NewNode); 276 } 277 } 278 } 279 280 /// constructFunction - make a function based on inputs and outputs, as follows: 281 /// f(in0, ..., inN, out0, ..., outN) 282 /// 283 Function *CodeExtractor::constructFunction(const ValueSet &inputs, 284 const ValueSet &outputs, 285 BasicBlock *header, 286 BasicBlock *newRootNode, 287 BasicBlock *newHeader, 288 Function *oldFunction, 289 Module *M) { 290 DEBUG(dbgs() << "inputs: " << inputs.size() << "\n"); 291 DEBUG(dbgs() << "outputs: " << outputs.size() << "\n"); 292 293 // This function returns unsigned, outputs will go back by reference. 294 switch (NumExitBlocks) { 295 case 0: 296 case 1: RetTy = Type::getVoidTy(header->getContext()); break; 297 case 2: RetTy = Type::getInt1Ty(header->getContext()); break; 298 default: RetTy = Type::getInt16Ty(header->getContext()); break; 299 } 300 301 std::vector<Type*> paramTy; 302 303 // Add the types of the input values to the function's argument list 304 for (Value *value : inputs) { 305 DEBUG(dbgs() << "value used in func: " << *value << "\n"); 306 paramTy.push_back(value->getType()); 307 } 308 309 // Add the types of the output values to the function's argument list. 310 for (Value *output : outputs) { 311 DEBUG(dbgs() << "instr used in func: " << *output << "\n"); 312 if (AggregateArgs) 313 paramTy.push_back(output->getType()); 314 else 315 paramTy.push_back(PointerType::getUnqual(output->getType())); 316 } 317 318 DEBUG({ 319 dbgs() << "Function type: " << *RetTy << " f("; 320 for (Type *i : paramTy) 321 dbgs() << *i << ", "; 322 dbgs() << ")\n"; 323 }); 324 325 StructType *StructTy; 326 if (AggregateArgs && (inputs.size() + outputs.size() > 0)) { 327 StructTy = StructType::get(M->getContext(), paramTy); 328 paramTy.clear(); 329 paramTy.push_back(PointerType::getUnqual(StructTy)); 330 } 331 FunctionType *funcType = 332 FunctionType::get(RetTy, paramTy, false); 333 334 // Create the new function 335 Function *newFunction = Function::Create(funcType, 336 GlobalValue::InternalLinkage, 337 oldFunction->getName() + "_" + 338 header->getName(), M); 339 // If the old function is no-throw, so is the new one. 340 if (oldFunction->doesNotThrow()) 341 newFunction->setDoesNotThrow(); 342 343 newFunction->getBasicBlockList().push_back(newRootNode); 344 345 // Create an iterator to name all of the arguments we inserted. 346 Function::arg_iterator AI = newFunction->arg_begin(); 347 348 // Rewrite all users of the inputs in the extracted region to use the 349 // arguments (or appropriate addressing into struct) instead. 350 for (unsigned i = 0, e = inputs.size(); i != e; ++i) { 351 Value *RewriteVal; 352 if (AggregateArgs) { 353 Value *Idx[2]; 354 Idx[0] = Constant::getNullValue(Type::getInt32Ty(header->getContext())); 355 Idx[1] = ConstantInt::get(Type::getInt32Ty(header->getContext()), i); 356 TerminatorInst *TI = newFunction->begin()->getTerminator(); 357 GetElementPtrInst *GEP = GetElementPtrInst::Create( 358 StructTy, &*AI, Idx, "gep_" + inputs[i]->getName(), TI); 359 RewriteVal = new LoadInst(GEP, "loadgep_" + inputs[i]->getName(), TI); 360 } else 361 RewriteVal = &*AI++; 362 363 std::vector<User*> Users(inputs[i]->user_begin(), inputs[i]->user_end()); 364 for (User *use : Users) 365 if (Instruction *inst = dyn_cast<Instruction>(use)) 366 if (Blocks.count(inst->getParent())) 367 inst->replaceUsesOfWith(inputs[i], RewriteVal); 368 } 369 370 // Set names for input and output arguments. 371 if (!AggregateArgs) { 372 AI = newFunction->arg_begin(); 373 for (unsigned i = 0, e = inputs.size(); i != e; ++i, ++AI) 374 AI->setName(inputs[i]->getName()); 375 for (unsigned i = 0, e = outputs.size(); i != e; ++i, ++AI) 376 AI->setName(outputs[i]->getName()+".out"); 377 } 378 379 // Rewrite branches to basic blocks outside of the loop to new dummy blocks 380 // within the new function. This must be done before we lose track of which 381 // blocks were originally in the code region. 382 std::vector<User*> Users(header->user_begin(), header->user_end()); 383 for (unsigned i = 0, e = Users.size(); i != e; ++i) 384 // The BasicBlock which contains the branch is not in the region 385 // modify the branch target to a new block 386 if (TerminatorInst *TI = dyn_cast<TerminatorInst>(Users[i])) 387 if (!Blocks.count(TI->getParent()) && 388 TI->getParent()->getParent() == oldFunction) 389 TI->replaceUsesOfWith(header, newHeader); 390 391 return newFunction; 392 } 393 394 /// FindPhiPredForUseInBlock - Given a value and a basic block, find a PHI 395 /// that uses the value within the basic block, and return the predecessor 396 /// block associated with that use, or return 0 if none is found. 397 static BasicBlock* FindPhiPredForUseInBlock(Value* Used, BasicBlock* BB) { 398 for (Use &U : Used->uses()) { 399 PHINode *P = dyn_cast<PHINode>(U.getUser()); 400 if (P && P->getParent() == BB) 401 return P->getIncomingBlock(U); 402 } 403 404 return nullptr; 405 } 406 407 /// emitCallAndSwitchStatement - This method sets up the caller side by adding 408 /// the call instruction, splitting any PHI nodes in the header block as 409 /// necessary. 410 void CodeExtractor:: 411 emitCallAndSwitchStatement(Function *newFunction, BasicBlock *codeReplacer, 412 ValueSet &inputs, ValueSet &outputs) { 413 // Emit a call to the new function, passing in: *pointer to struct (if 414 // aggregating parameters), or plan inputs and allocated memory for outputs 415 std::vector<Value*> params, StructValues, ReloadOutputs, Reloads; 416 417 LLVMContext &Context = newFunction->getContext(); 418 419 // Add inputs as params, or to be filled into the struct 420 for (Value *input : inputs) 421 if (AggregateArgs) 422 StructValues.push_back(input); 423 else 424 params.push_back(input); 425 426 // Create allocas for the outputs 427 for (Value *output : outputs) { 428 if (AggregateArgs) { 429 StructValues.push_back(output); 430 } else { 431 AllocaInst *alloca = 432 new AllocaInst(output->getType(), nullptr, output->getName() + ".loc", 433 &codeReplacer->getParent()->front().front()); 434 ReloadOutputs.push_back(alloca); 435 params.push_back(alloca); 436 } 437 } 438 439 StructType *StructArgTy = nullptr; 440 AllocaInst *Struct = nullptr; 441 if (AggregateArgs && (inputs.size() + outputs.size() > 0)) { 442 std::vector<Type*> ArgTypes; 443 for (ValueSet::iterator v = StructValues.begin(), 444 ve = StructValues.end(); v != ve; ++v) 445 ArgTypes.push_back((*v)->getType()); 446 447 // Allocate a struct at the beginning of this function 448 StructArgTy = StructType::get(newFunction->getContext(), ArgTypes); 449 Struct = new AllocaInst(StructArgTy, nullptr, "structArg", 450 &codeReplacer->getParent()->front().front()); 451 params.push_back(Struct); 452 453 for (unsigned i = 0, e = inputs.size(); i != e; ++i) { 454 Value *Idx[2]; 455 Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context)); 456 Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), i); 457 GetElementPtrInst *GEP = GetElementPtrInst::Create( 458 StructArgTy, Struct, Idx, "gep_" + StructValues[i]->getName()); 459 codeReplacer->getInstList().push_back(GEP); 460 StoreInst *SI = new StoreInst(StructValues[i], GEP); 461 codeReplacer->getInstList().push_back(SI); 462 } 463 } 464 465 // Emit the call to the function 466 CallInst *call = CallInst::Create(newFunction, params, 467 NumExitBlocks > 1 ? "targetBlock" : ""); 468 codeReplacer->getInstList().push_back(call); 469 470 Function::arg_iterator OutputArgBegin = newFunction->arg_begin(); 471 unsigned FirstOut = inputs.size(); 472 if (!AggregateArgs) 473 std::advance(OutputArgBegin, inputs.size()); 474 475 // Reload the outputs passed in by reference 476 for (unsigned i = 0, e = outputs.size(); i != e; ++i) { 477 Value *Output = nullptr; 478 if (AggregateArgs) { 479 Value *Idx[2]; 480 Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context)); 481 Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), FirstOut + i); 482 GetElementPtrInst *GEP = GetElementPtrInst::Create( 483 StructArgTy, Struct, Idx, "gep_reload_" + outputs[i]->getName()); 484 codeReplacer->getInstList().push_back(GEP); 485 Output = GEP; 486 } else { 487 Output = ReloadOutputs[i]; 488 } 489 LoadInst *load = new LoadInst(Output, outputs[i]->getName()+".reload"); 490 Reloads.push_back(load); 491 codeReplacer->getInstList().push_back(load); 492 std::vector<User*> Users(outputs[i]->user_begin(), outputs[i]->user_end()); 493 for (unsigned u = 0, e = Users.size(); u != e; ++u) { 494 Instruction *inst = cast<Instruction>(Users[u]); 495 if (!Blocks.count(inst->getParent())) 496 inst->replaceUsesOfWith(outputs[i], load); 497 } 498 } 499 500 // Now we can emit a switch statement using the call as a value. 501 SwitchInst *TheSwitch = 502 SwitchInst::Create(Constant::getNullValue(Type::getInt16Ty(Context)), 503 codeReplacer, 0, codeReplacer); 504 505 // Since there may be multiple exits from the original region, make the new 506 // function return an unsigned, switch on that number. This loop iterates 507 // over all of the blocks in the extracted region, updating any terminator 508 // instructions in the to-be-extracted region that branch to blocks that are 509 // not in the region to be extracted. 510 std::map<BasicBlock*, BasicBlock*> ExitBlockMap; 511 512 unsigned switchVal = 0; 513 for (BasicBlock *Block : Blocks) { 514 TerminatorInst *TI = Block->getTerminator(); 515 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 516 if (!Blocks.count(TI->getSuccessor(i))) { 517 BasicBlock *OldTarget = TI->getSuccessor(i); 518 // add a new basic block which returns the appropriate value 519 BasicBlock *&NewTarget = ExitBlockMap[OldTarget]; 520 if (!NewTarget) { 521 // If we don't already have an exit stub for this non-extracted 522 // destination, create one now! 523 NewTarget = BasicBlock::Create(Context, 524 OldTarget->getName() + ".exitStub", 525 newFunction); 526 unsigned SuccNum = switchVal++; 527 528 Value *brVal = nullptr; 529 switch (NumExitBlocks) { 530 case 0: 531 case 1: break; // No value needed. 532 case 2: // Conditional branch, return a bool 533 brVal = ConstantInt::get(Type::getInt1Ty(Context), !SuccNum); 534 break; 535 default: 536 brVal = ConstantInt::get(Type::getInt16Ty(Context), SuccNum); 537 break; 538 } 539 540 ReturnInst *NTRet = ReturnInst::Create(Context, brVal, NewTarget); 541 542 // Update the switch instruction. 543 TheSwitch->addCase(ConstantInt::get(Type::getInt16Ty(Context), 544 SuccNum), 545 OldTarget); 546 547 // Restore values just before we exit 548 Function::arg_iterator OAI = OutputArgBegin; 549 for (unsigned out = 0, e = outputs.size(); out != e; ++out) { 550 // For an invoke, the normal destination is the only one that is 551 // dominated by the result of the invocation 552 BasicBlock *DefBlock = cast<Instruction>(outputs[out])->getParent(); 553 554 bool DominatesDef = true; 555 556 BasicBlock *NormalDest = nullptr; 557 if (auto *Invoke = dyn_cast<InvokeInst>(outputs[out])) 558 NormalDest = Invoke->getNormalDest(); 559 560 if (NormalDest) { 561 DefBlock = NormalDest; 562 563 // Make sure we are looking at the original successor block, not 564 // at a newly inserted exit block, which won't be in the dominator 565 // info. 566 for (const auto &I : ExitBlockMap) 567 if (DefBlock == I.second) { 568 DefBlock = I.first; 569 break; 570 } 571 572 // In the extract block case, if the block we are extracting ends 573 // with an invoke instruction, make sure that we don't emit a 574 // store of the invoke value for the unwind block. 575 if (!DT && DefBlock != OldTarget) 576 DominatesDef = false; 577 } 578 579 if (DT) { 580 DominatesDef = DT->dominates(DefBlock, OldTarget); 581 582 // If the output value is used by a phi in the target block, 583 // then we need to test for dominance of the phi's predecessor 584 // instead. Unfortunately, this a little complicated since we 585 // have already rewritten uses of the value to uses of the reload. 586 BasicBlock* pred = FindPhiPredForUseInBlock(Reloads[out], 587 OldTarget); 588 if (pred && DT && DT->dominates(DefBlock, pred)) 589 DominatesDef = true; 590 } 591 592 if (DominatesDef) { 593 if (AggregateArgs) { 594 Value *Idx[2]; 595 Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context)); 596 Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), 597 FirstOut+out); 598 GetElementPtrInst *GEP = GetElementPtrInst::Create( 599 StructArgTy, &*OAI, Idx, "gep_" + outputs[out]->getName(), 600 NTRet); 601 new StoreInst(outputs[out], GEP, NTRet); 602 } else { 603 new StoreInst(outputs[out], &*OAI, NTRet); 604 } 605 } 606 // Advance output iterator even if we don't emit a store 607 if (!AggregateArgs) ++OAI; 608 } 609 } 610 611 // rewrite the original branch instruction with this new target 612 TI->setSuccessor(i, NewTarget); 613 } 614 } 615 616 // Now that we've done the deed, simplify the switch instruction. 617 Type *OldFnRetTy = TheSwitch->getParent()->getParent()->getReturnType(); 618 switch (NumExitBlocks) { 619 case 0: 620 // There are no successors (the block containing the switch itself), which 621 // means that previously this was the last part of the function, and hence 622 // this should be rewritten as a `ret' 623 624 // Check if the function should return a value 625 if (OldFnRetTy->isVoidTy()) { 626 ReturnInst::Create(Context, nullptr, TheSwitch); // Return void 627 } else if (OldFnRetTy == TheSwitch->getCondition()->getType()) { 628 // return what we have 629 ReturnInst::Create(Context, TheSwitch->getCondition(), TheSwitch); 630 } else { 631 // Otherwise we must have code extracted an unwind or something, just 632 // return whatever we want. 633 ReturnInst::Create(Context, 634 Constant::getNullValue(OldFnRetTy), TheSwitch); 635 } 636 637 TheSwitch->eraseFromParent(); 638 break; 639 case 1: 640 // Only a single destination, change the switch into an unconditional 641 // branch. 642 BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch); 643 TheSwitch->eraseFromParent(); 644 break; 645 case 2: 646 BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch->getSuccessor(2), 647 call, TheSwitch); 648 TheSwitch->eraseFromParent(); 649 break; 650 default: 651 // Otherwise, make the default destination of the switch instruction be one 652 // of the other successors. 653 TheSwitch->setCondition(call); 654 TheSwitch->setDefaultDest(TheSwitch->getSuccessor(NumExitBlocks)); 655 // Remove redundant case 656 TheSwitch->removeCase(SwitchInst::CaseIt(TheSwitch, NumExitBlocks-1)); 657 break; 658 } 659 } 660 661 void CodeExtractor::moveCodeToFunction(Function *newFunction) { 662 Function *oldFunc = (*Blocks.begin())->getParent(); 663 Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList(); 664 Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList(); 665 666 for (BasicBlock *Block : Blocks) { 667 // Delete the basic block from the old function, and the list of blocks 668 oldBlocks.remove(Block); 669 670 // Insert this basic block into the new function 671 newBlocks.push_back(Block); 672 } 673 } 674 675 Function *CodeExtractor::extractCodeRegion() { 676 if (!isEligible()) 677 return nullptr; 678 679 ValueSet inputs, outputs; 680 681 // Assumption: this is a single-entry code region, and the header is the first 682 // block in the region. 683 BasicBlock *header = *Blocks.begin(); 684 685 // If we have to split PHI nodes or the entry block, do so now. 686 severSplitPHINodes(header); 687 688 // If we have any return instructions in the region, split those blocks so 689 // that the return is not in the region. 690 splitReturnBlocks(); 691 692 Function *oldFunction = header->getParent(); 693 694 // This takes place of the original loop 695 BasicBlock *codeReplacer = BasicBlock::Create(header->getContext(), 696 "codeRepl", oldFunction, 697 header); 698 699 // The new function needs a root node because other nodes can branch to the 700 // head of the region, but the entry node of a function cannot have preds. 701 BasicBlock *newFuncRoot = BasicBlock::Create(header->getContext(), 702 "newFuncRoot"); 703 newFuncRoot->getInstList().push_back(BranchInst::Create(header)); 704 705 // Find inputs to, outputs from the code region. 706 findInputsOutputs(inputs, outputs); 707 708 SmallPtrSet<BasicBlock *, 1> ExitBlocks; 709 for (BasicBlock *Block : Blocks) 710 for (succ_iterator SI = succ_begin(Block), SE = succ_end(Block); SI != SE; 711 ++SI) 712 if (!Blocks.count(*SI)) 713 ExitBlocks.insert(*SI); 714 NumExitBlocks = ExitBlocks.size(); 715 716 // Construct new function based on inputs/outputs & add allocas for all defs. 717 Function *newFunction = constructFunction(inputs, outputs, header, 718 newFuncRoot, 719 codeReplacer, oldFunction, 720 oldFunction->getParent()); 721 722 emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs); 723 724 moveCodeToFunction(newFunction); 725 726 // Loop over all of the PHI nodes in the header block, and change any 727 // references to the old incoming edge to be the new incoming edge. 728 for (BasicBlock::iterator I = header->begin(); isa<PHINode>(I); ++I) { 729 PHINode *PN = cast<PHINode>(I); 730 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 731 if (!Blocks.count(PN->getIncomingBlock(i))) 732 PN->setIncomingBlock(i, newFuncRoot); 733 } 734 735 // Look at all successors of the codeReplacer block. If any of these blocks 736 // had PHI nodes in them, we need to update the "from" block to be the code 737 // replacer, not the original block in the extracted region. 738 std::vector<BasicBlock*> Succs(succ_begin(codeReplacer), 739 succ_end(codeReplacer)); 740 for (unsigned i = 0, e = Succs.size(); i != e; ++i) 741 for (BasicBlock::iterator I = Succs[i]->begin(); isa<PHINode>(I); ++I) { 742 PHINode *PN = cast<PHINode>(I); 743 std::set<BasicBlock*> ProcessedPreds; 744 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 745 if (Blocks.count(PN->getIncomingBlock(i))) { 746 if (ProcessedPreds.insert(PN->getIncomingBlock(i)).second) 747 PN->setIncomingBlock(i, codeReplacer); 748 else { 749 // There were multiple entries in the PHI for this block, now there 750 // is only one, so remove the duplicated entries. 751 PN->removeIncomingValue(i, false); 752 --i; --e; 753 } 754 } 755 } 756 757 //cerr << "NEW FUNCTION: " << *newFunction; 758 // verifyFunction(*newFunction); 759 760 // cerr << "OLD FUNCTION: " << *oldFunction; 761 // verifyFunction(*oldFunction); 762 763 DEBUG(if (verifyFunction(*newFunction)) 764 report_fatal_error("verifyFunction failed!")); 765 return newFunction; 766 } 767