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> 39using 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(). 47static cl::opt<bool> 48AggregateArgsOpt("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. 52static 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. 71template <typename IteratorT> 72static 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 for (IteratorT I = BBBegin, E = BBEnd; I != E; ++I) { 81 if (!Result.insert(*I)) 82 llvm_unreachable("Repeated basic blocks in extraction input"); 83 84 if (!isBlockValidForExtraction(**I)) { 85 Result.clear(); 86 return Result; 87 } 88 } 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. 105static SetVector<BasicBlock *> 106buildExtractionBlockSet(ArrayRef<BasicBlock *> BBs) { 107 return buildExtractionBlockSet(BBs.begin(), BBs.end()); 108} 109 110/// \brief Helper to call buildExtractionBlockSet with a RegionNode. 111static SetVector<BasicBlock *> 112buildExtractionBlockSet(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 122CodeExtractor::CodeExtractor(BasicBlock *BB, bool AggregateArgs) 123 : DT(nullptr), AggregateArgs(AggregateArgs||AggregateArgsOpt), 124 Blocks(buildExtractionBlockSet(BB)), NumExitBlocks(~0U) {} 125 126CodeExtractor::CodeExtractor(ArrayRef<BasicBlock *> BBs, DominatorTree *DT, 127 bool AggregateArgs) 128 : DT(DT), AggregateArgs(AggregateArgs||AggregateArgsOpt), 129 Blocks(buildExtractionBlockSet(BBs)), NumExitBlocks(~0U) {} 130 131CodeExtractor::CodeExtractor(DominatorTree &DT, Loop &L, bool AggregateArgs) 132 : DT(&DT), AggregateArgs(AggregateArgs||AggregateArgsOpt), 133 Blocks(buildExtractionBlockSet(L.getBlocks())), NumExitBlocks(~0U) {} 134 135CodeExtractor::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. 142static 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. 152static 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 160void CodeExtractor::findInputsOutputs(ValueSet &Inputs, 161 ValueSet &Outputs) const { 162 for (SetVector<BasicBlock *>::const_iterator I = Blocks.begin(), 163 E = Blocks.end(); 164 I != E; ++I) { 165 BasicBlock *BB = *I; 166 167 // If a used value is defined outside the region, it's an input. If an 168 // instruction is used outside the region, it's an output. 169 for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); 170 II != IE; ++II) { 171 for (User::op_iterator OI = II->op_begin(), OE = II->op_end(); 172 OI != OE; ++OI) 173 if (definedInCaller(Blocks, *OI)) 174 Inputs.insert(*OI); 175 176 for (User *U : II->users()) 177 if (!definedInRegion(Blocks, U)) { 178 Outputs.insert(&*II); 179 break; 180 } 181 } 182 } 183} 184 185/// severSplitPHINodes - If a PHI node has multiple inputs from outside of the 186/// region, we need to split the entry block of the region so that the PHI node 187/// is easier to deal with. 188void CodeExtractor::severSplitPHINodes(BasicBlock *&Header) { 189 unsigned NumPredsFromRegion = 0; 190 unsigned NumPredsOutsideRegion = 0; 191 192 if (Header != &Header->getParent()->getEntryBlock()) { 193 PHINode *PN = dyn_cast<PHINode>(Header->begin()); 194 if (!PN) return; // No PHI nodes. 195 196 // If the header node contains any PHI nodes, check to see if there is more 197 // than one entry from outside the region. If so, we need to sever the 198 // header block into two. 199 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 200 if (Blocks.count(PN->getIncomingBlock(i))) 201 ++NumPredsFromRegion; 202 else 203 ++NumPredsOutsideRegion; 204 205 // If there is one (or fewer) predecessor from outside the region, we don't 206 // need to do anything special. 207 if (NumPredsOutsideRegion <= 1) return; 208 } 209 210 // Otherwise, we need to split the header block into two pieces: one 211 // containing PHI nodes merging values from outside of the region, and a 212 // second that contains all of the code for the block and merges back any 213 // incoming values from inside of the region. 214 BasicBlock::iterator AfterPHIs = Header->getFirstNonPHI()->getIterator(); 215 BasicBlock *NewBB = Header->splitBasicBlock(AfterPHIs, 216 Header->getName()+".ce"); 217 218 // We only want to code extract the second block now, and it becomes the new 219 // header of the region. 220 BasicBlock *OldPred = Header; 221 Blocks.remove(OldPred); 222 Blocks.insert(NewBB); 223 Header = NewBB; 224 225 // Okay, update dominator sets. The blocks that dominate the new one are the 226 // blocks that dominate TIBB plus the new block itself. 227 if (DT) 228 DT->splitBlock(NewBB); 229 230 // Okay, now we need to adjust the PHI nodes and any branches from within the 231 // region to go to the new header block instead of the old header block. 232 if (NumPredsFromRegion) { 233 PHINode *PN = cast<PHINode>(OldPred->begin()); 234 // Loop over all of the predecessors of OldPred that are in the region, 235 // changing them to branch to NewBB instead. 236 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 237 if (Blocks.count(PN->getIncomingBlock(i))) { 238 TerminatorInst *TI = PN->getIncomingBlock(i)->getTerminator(); 239 TI->replaceUsesOfWith(OldPred, NewBB); 240 } 241 242 // Okay, everything within the region is now branching to the right block, we 243 // just have to update the PHI nodes now, inserting PHI nodes into NewBB. 244 for (AfterPHIs = OldPred->begin(); isa<PHINode>(AfterPHIs); ++AfterPHIs) { 245 PHINode *PN = cast<PHINode>(AfterPHIs); 246 // Create a new PHI node in the new region, which has an incoming value 247 // from OldPred of PN. 248 PHINode *NewPN = PHINode::Create(PN->getType(), 1 + NumPredsFromRegion, 249 PN->getName() + ".ce", &NewBB->front()); 250 NewPN->addIncoming(PN, OldPred); 251 252 // Loop over all of the incoming value in PN, moving them to NewPN if they 253 // are from the extracted region. 254 for (unsigned i = 0; i != PN->getNumIncomingValues(); ++i) { 255 if (Blocks.count(PN->getIncomingBlock(i))) { 256 NewPN->addIncoming(PN->getIncomingValue(i), PN->getIncomingBlock(i)); 257 PN->removeIncomingValue(i); 258 --i; 259 } 260 } 261 } 262 } 263} 264 265void CodeExtractor::splitReturnBlocks() { 266 for (SetVector<BasicBlock *>::iterator I = Blocks.begin(), E = Blocks.end(); 267 I != E; ++I) 268 if (ReturnInst *RI = dyn_cast<ReturnInst>((*I)->getTerminator())) { 269 BasicBlock *New = 270 (*I)->splitBasicBlock(RI->getIterator(), (*I)->getName() + ".ret"); 271 if (DT) { 272 // Old dominates New. New node dominates all other nodes dominated 273 // by Old. 274 DomTreeNode *OldNode = DT->getNode(*I); 275 SmallVector<DomTreeNode*, 8> Children; 276 for (DomTreeNode::iterator DI = OldNode->begin(), DE = OldNode->end(); 277 DI != DE; ++DI) 278 Children.push_back(*DI); 279 280 DomTreeNode *NewNode = DT->addNewBlock(New, *I); 281 282 for (SmallVectorImpl<DomTreeNode *>::iterator I = Children.begin(), 283 E = Children.end(); I != E; ++I) 284 DT->changeImmediateDominator(*I, NewNode); 285 } 286 } 287} 288 289/// constructFunction - make a function based on inputs and outputs, as follows: 290/// f(in0, ..., inN, out0, ..., outN) 291/// 292Function *CodeExtractor::constructFunction(const ValueSet &inputs, 293 const ValueSet &outputs, 294 BasicBlock *header, 295 BasicBlock *newRootNode, 296 BasicBlock *newHeader, 297 Function *oldFunction, 298 Module *M) { 299 DEBUG(dbgs() << "inputs: " << inputs.size() << "\n"); 300 DEBUG(dbgs() << "outputs: " << outputs.size() << "\n"); 301 302 // This function returns unsigned, outputs will go back by reference. 303 switch (NumExitBlocks) { 304 case 0: 305 case 1: RetTy = Type::getVoidTy(header->getContext()); break; 306 case 2: RetTy = Type::getInt1Ty(header->getContext()); break; 307 default: RetTy = Type::getInt16Ty(header->getContext()); break; 308 } 309 310 std::vector<Type*> paramTy; 311 312 // Add the types of the input values to the function's argument list 313 for (ValueSet::const_iterator i = inputs.begin(), e = inputs.end(); 314 i != e; ++i) { 315 const Value *value = *i; 316 DEBUG(dbgs() << "value used in func: " << *value << "\n"); 317 paramTy.push_back(value->getType()); 318 } 319 320 // Add the types of the output values to the function's argument list. 321 for (ValueSet::const_iterator I = outputs.begin(), E = outputs.end(); 322 I != E; ++I) { 323 DEBUG(dbgs() << "instr used in func: " << **I << "\n"); 324 if (AggregateArgs) 325 paramTy.push_back((*I)->getType()); 326 else 327 paramTy.push_back(PointerType::getUnqual((*I)->getType())); 328 } 329 330 DEBUG(dbgs() << "Function type: " << *RetTy << " f("); 331 for (std::vector<Type*>::iterator i = paramTy.begin(), 332 e = paramTy.end(); i != e; ++i) 333 DEBUG(dbgs() << **i << ", "); 334 DEBUG(dbgs() << ")\n"); 335 336 StructType *StructTy; 337 if (AggregateArgs && (inputs.size() + outputs.size() > 0)) { 338 StructTy = StructType::get(M->getContext(), paramTy); 339 paramTy.clear(); 340 paramTy.push_back(PointerType::getUnqual(StructTy)); 341 } 342 FunctionType *funcType = 343 FunctionType::get(RetTy, paramTy, false); 344 345 // Create the new function 346 Function *newFunction = Function::Create(funcType, 347 GlobalValue::InternalLinkage, 348 oldFunction->getName() + "_" + 349 header->getName(), M); 350 // If the old function is no-throw, so is the new one. 351 if (oldFunction->doesNotThrow()) 352 newFunction->setDoesNotThrow(); 353 354 newFunction->getBasicBlockList().push_back(newRootNode); 355 356 // Create an iterator to name all of the arguments we inserted. 357 Function::arg_iterator AI = newFunction->arg_begin(); 358 359 // Rewrite all users of the inputs in the extracted region to use the 360 // arguments (or appropriate addressing into struct) instead. 361 for (unsigned i = 0, e = inputs.size(); i != e; ++i) { 362 Value *RewriteVal; 363 if (AggregateArgs) { 364 Value *Idx[2]; 365 Idx[0] = Constant::getNullValue(Type::getInt32Ty(header->getContext())); 366 Idx[1] = ConstantInt::get(Type::getInt32Ty(header->getContext()), i); 367 TerminatorInst *TI = newFunction->begin()->getTerminator(); 368 GetElementPtrInst *GEP = GetElementPtrInst::Create( 369 StructTy, &*AI, Idx, "gep_" + inputs[i]->getName(), TI); 370 RewriteVal = new LoadInst(GEP, "loadgep_" + inputs[i]->getName(), TI); 371 } else 372 RewriteVal = &*AI++; 373 374 std::vector<User*> Users(inputs[i]->user_begin(), inputs[i]->user_end()); 375 for (std::vector<User*>::iterator use = Users.begin(), useE = Users.end(); 376 use != useE; ++use) 377 if (Instruction* inst = dyn_cast<Instruction>(*use)) 378 if (Blocks.count(inst->getParent())) 379 inst->replaceUsesOfWith(inputs[i], RewriteVal); 380 } 381 382 // Set names for input and output arguments. 383 if (!AggregateArgs) { 384 AI = newFunction->arg_begin(); 385 for (unsigned i = 0, e = inputs.size(); i != e; ++i, ++AI) 386 AI->setName(inputs[i]->getName()); 387 for (unsigned i = 0, e = outputs.size(); i != e; ++i, ++AI) 388 AI->setName(outputs[i]->getName()+".out"); 389 } 390 391 // Rewrite branches to basic blocks outside of the loop to new dummy blocks 392 // within the new function. This must be done before we lose track of which 393 // blocks were originally in the code region. 394 std::vector<User*> Users(header->user_begin(), header->user_end()); 395 for (unsigned i = 0, e = Users.size(); i != e; ++i) 396 // The BasicBlock which contains the branch is not in the region 397 // modify the branch target to a new block 398 if (TerminatorInst *TI = dyn_cast<TerminatorInst>(Users[i])) 399 if (!Blocks.count(TI->getParent()) && 400 TI->getParent()->getParent() == oldFunction) 401 TI->replaceUsesOfWith(header, newHeader); 402 403 return newFunction; 404} 405 406/// FindPhiPredForUseInBlock - Given a value and a basic block, find a PHI 407/// that uses the value within the basic block, and return the predecessor 408/// block associated with that use, or return 0 if none is found. 409static BasicBlock* FindPhiPredForUseInBlock(Value* Used, BasicBlock* BB) { 410 for (Use &U : Used->uses()) { 411 PHINode *P = dyn_cast<PHINode>(U.getUser()); 412 if (P && P->getParent() == BB) 413 return P->getIncomingBlock(U); 414 } 415 416 return nullptr; 417} 418 419/// emitCallAndSwitchStatement - This method sets up the caller side by adding 420/// the call instruction, splitting any PHI nodes in the header block as 421/// necessary. 422void CodeExtractor:: 423emitCallAndSwitchStatement(Function *newFunction, BasicBlock *codeReplacer, 424 ValueSet &inputs, ValueSet &outputs) { 425 // Emit a call to the new function, passing in: *pointer to struct (if 426 // aggregating parameters), or plan inputs and allocated memory for outputs 427 std::vector<Value*> params, StructValues, ReloadOutputs, Reloads; 428 429 LLVMContext &Context = newFunction->getContext(); 430 431 // Add inputs as params, or to be filled into the struct 432 for (ValueSet::iterator i = inputs.begin(), e = inputs.end(); i != e; ++i) 433 if (AggregateArgs) 434 StructValues.push_back(*i); 435 else 436 params.push_back(*i); 437 438 // Create allocas for the outputs 439 for (ValueSet::iterator i = outputs.begin(), e = outputs.end(); i != e; ++i) { 440 if (AggregateArgs) { 441 StructValues.push_back(*i); 442 } else { 443 AllocaInst *alloca = 444 new AllocaInst((*i)->getType(), nullptr, (*i)->getName() + ".loc", 445 &codeReplacer->getParent()->front().front()); 446 ReloadOutputs.push_back(alloca); 447 params.push_back(alloca); 448 } 449 } 450 451 StructType *StructArgTy = nullptr; 452 AllocaInst *Struct = nullptr; 453 if (AggregateArgs && (inputs.size() + outputs.size() > 0)) { 454 std::vector<Type*> ArgTypes; 455 for (ValueSet::iterator v = StructValues.begin(), 456 ve = StructValues.end(); v != ve; ++v) 457 ArgTypes.push_back((*v)->getType()); 458 459 // Allocate a struct at the beginning of this function 460 StructArgTy = StructType::get(newFunction->getContext(), ArgTypes); 461 Struct = new AllocaInst(StructArgTy, nullptr, "structArg", 462 &codeReplacer->getParent()->front().front()); 463 params.push_back(Struct); 464 465 for (unsigned i = 0, e = inputs.size(); i != e; ++i) { 466 Value *Idx[2]; 467 Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context)); 468 Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), i); 469 GetElementPtrInst *GEP = GetElementPtrInst::Create( 470 StructArgTy, Struct, Idx, "gep_" + StructValues[i]->getName()); 471 codeReplacer->getInstList().push_back(GEP); 472 StoreInst *SI = new StoreInst(StructValues[i], GEP); 473 codeReplacer->getInstList().push_back(SI); 474 } 475 } 476 477 // Emit the call to the function 478 CallInst *call = CallInst::Create(newFunction, params, 479 NumExitBlocks > 1 ? "targetBlock" : ""); 480 codeReplacer->getInstList().push_back(call); 481 482 Function::arg_iterator OutputArgBegin = newFunction->arg_begin(); 483 unsigned FirstOut = inputs.size(); 484 if (!AggregateArgs) 485 std::advance(OutputArgBegin, inputs.size()); 486 487 // Reload the outputs passed in by reference 488 for (unsigned i = 0, e = outputs.size(); i != e; ++i) { 489 Value *Output = nullptr; 490 if (AggregateArgs) { 491 Value *Idx[2]; 492 Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context)); 493 Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), FirstOut + i); 494 GetElementPtrInst *GEP = GetElementPtrInst::Create( 495 StructArgTy, Struct, Idx, "gep_reload_" + outputs[i]->getName()); 496 codeReplacer->getInstList().push_back(GEP); 497 Output = GEP; 498 } else { 499 Output = ReloadOutputs[i]; 500 } 501 LoadInst *load = new LoadInst(Output, outputs[i]->getName()+".reload"); 502 Reloads.push_back(load); 503 codeReplacer->getInstList().push_back(load); 504 std::vector<User*> Users(outputs[i]->user_begin(), outputs[i]->user_end()); 505 for (unsigned u = 0, e = Users.size(); u != e; ++u) { 506 Instruction *inst = cast<Instruction>(Users[u]); 507 if (!Blocks.count(inst->getParent())) 508 inst->replaceUsesOfWith(outputs[i], load); 509 } 510 } 511 512 // Now we can emit a switch statement using the call as a value. 513 SwitchInst *TheSwitch = 514 SwitchInst::Create(Constant::getNullValue(Type::getInt16Ty(Context)), 515 codeReplacer, 0, codeReplacer); 516 517 // Since there may be multiple exits from the original region, make the new 518 // function return an unsigned, switch on that number. This loop iterates 519 // over all of the blocks in the extracted region, updating any terminator 520 // instructions in the to-be-extracted region that branch to blocks that are 521 // not in the region to be extracted. 522 std::map<BasicBlock*, BasicBlock*> ExitBlockMap; 523 524 unsigned switchVal = 0; 525 for (SetVector<BasicBlock*>::const_iterator i = Blocks.begin(), 526 e = Blocks.end(); i != e; ++i) { 527 TerminatorInst *TI = (*i)->getTerminator(); 528 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) 529 if (!Blocks.count(TI->getSuccessor(i))) { 530 BasicBlock *OldTarget = TI->getSuccessor(i); 531 // add a new basic block which returns the appropriate value 532 BasicBlock *&NewTarget = ExitBlockMap[OldTarget]; 533 if (!NewTarget) { 534 // If we don't already have an exit stub for this non-extracted 535 // destination, create one now! 536 NewTarget = BasicBlock::Create(Context, 537 OldTarget->getName() + ".exitStub", 538 newFunction); 539 unsigned SuccNum = switchVal++; 540 541 Value *brVal = nullptr; 542 switch (NumExitBlocks) { 543 case 0: 544 case 1: break; // No value needed. 545 case 2: // Conditional branch, return a bool 546 brVal = ConstantInt::get(Type::getInt1Ty(Context), !SuccNum); 547 break; 548 default: 549 brVal = ConstantInt::get(Type::getInt16Ty(Context), SuccNum); 550 break; 551 } 552 553 ReturnInst *NTRet = ReturnInst::Create(Context, brVal, NewTarget); 554 555 // Update the switch instruction. 556 TheSwitch->addCase(ConstantInt::get(Type::getInt16Ty(Context), 557 SuccNum), 558 OldTarget); 559 560 // Restore values just before we exit 561 Function::arg_iterator OAI = OutputArgBegin; 562 for (unsigned out = 0, e = outputs.size(); out != e; ++out) { 563 // For an invoke, the normal destination is the only one that is 564 // dominated by the result of the invocation 565 BasicBlock *DefBlock = cast<Instruction>(outputs[out])->getParent(); 566 567 bool DominatesDef = true; 568 569 BasicBlock *NormalDest = nullptr; 570 if (auto *Invoke = dyn_cast<InvokeInst>(outputs[out])) 571 NormalDest = Invoke->getNormalDest(); 572 573 if (NormalDest) { 574 DefBlock = NormalDest; 575 576 // Make sure we are looking at the original successor block, not 577 // at a newly inserted exit block, which won't be in the dominator 578 // info. 579 for (std::map<BasicBlock*, BasicBlock*>::iterator I = 580 ExitBlockMap.begin(), E = ExitBlockMap.end(); I != E; ++I) 581 if (DefBlock == I->second) { 582 DefBlock = I->first; 583 break; 584 } 585 586 // In the extract block case, if the block we are extracting ends 587 // with an invoke instruction, make sure that we don't emit a 588 // store of the invoke value for the unwind block. 589 if (!DT && DefBlock != OldTarget) 590 DominatesDef = false; 591 } 592 593 if (DT) { 594 DominatesDef = DT->dominates(DefBlock, OldTarget); 595 596 // If the output value is used by a phi in the target block, 597 // then we need to test for dominance of the phi's predecessor 598 // instead. Unfortunately, this a little complicated since we 599 // have already rewritten uses of the value to uses of the reload. 600 BasicBlock* pred = FindPhiPredForUseInBlock(Reloads[out], 601 OldTarget); 602 if (pred && DT && DT->dominates(DefBlock, pred)) 603 DominatesDef = true; 604 } 605 606 if (DominatesDef) { 607 if (AggregateArgs) { 608 Value *Idx[2]; 609 Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context)); 610 Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), 611 FirstOut+out); 612 GetElementPtrInst *GEP = GetElementPtrInst::Create( 613 StructArgTy, &*OAI, Idx, "gep_" + outputs[out]->getName(), 614 NTRet); 615 new StoreInst(outputs[out], GEP, NTRet); 616 } else { 617 new StoreInst(outputs[out], &*OAI, NTRet); 618 } 619 } 620 // Advance output iterator even if we don't emit a store 621 if (!AggregateArgs) ++OAI; 622 } 623 } 624 625 // rewrite the original branch instruction with this new target 626 TI->setSuccessor(i, NewTarget); 627 } 628 } 629 630 // Now that we've done the deed, simplify the switch instruction. 631 Type *OldFnRetTy = TheSwitch->getParent()->getParent()->getReturnType(); 632 switch (NumExitBlocks) { 633 case 0: 634 // There are no successors (the block containing the switch itself), which 635 // means that previously this was the last part of the function, and hence 636 // this should be rewritten as a `ret' 637 638 // Check if the function should return a value 639 if (OldFnRetTy->isVoidTy()) { 640 ReturnInst::Create(Context, nullptr, TheSwitch); // Return void 641 } else if (OldFnRetTy == TheSwitch->getCondition()->getType()) { 642 // return what we have 643 ReturnInst::Create(Context, TheSwitch->getCondition(), TheSwitch); 644 } else { 645 // Otherwise we must have code extracted an unwind or something, just 646 // return whatever we want. 647 ReturnInst::Create(Context, 648 Constant::getNullValue(OldFnRetTy), TheSwitch); 649 } 650 651 TheSwitch->eraseFromParent(); 652 break; 653 case 1: 654 // Only a single destination, change the switch into an unconditional 655 // branch. 656 BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch); 657 TheSwitch->eraseFromParent(); 658 break; 659 case 2: 660 BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch->getSuccessor(2), 661 call, TheSwitch); 662 TheSwitch->eraseFromParent(); 663 break; 664 default: 665 // Otherwise, make the default destination of the switch instruction be one 666 // of the other successors. 667 TheSwitch->setCondition(call); 668 TheSwitch->setDefaultDest(TheSwitch->getSuccessor(NumExitBlocks)); 669 // Remove redundant case 670 TheSwitch->removeCase(SwitchInst::CaseIt(TheSwitch, NumExitBlocks-1)); 671 break; 672 } 673} 674 675void CodeExtractor::moveCodeToFunction(Function *newFunction) { 676 Function *oldFunc = (*Blocks.begin())->getParent(); 677 Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList(); 678 Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList(); 679 680 for (SetVector<BasicBlock*>::const_iterator i = Blocks.begin(), 681 e = Blocks.end(); i != e; ++i) { 682 // Delete the basic block from the old function, and the list of blocks 683 oldBlocks.remove(*i); 684 685 // Insert this basic block into the new function 686 newBlocks.push_back(*i); 687 } 688} 689 690Function *CodeExtractor::extractCodeRegion() { 691 if (!isEligible()) 692 return nullptr; 693 694 ValueSet inputs, outputs; 695 696 // Assumption: this is a single-entry code region, and the header is the first 697 // block in the region. 698 BasicBlock *header = *Blocks.begin(); 699 700 // If we have to split PHI nodes or the entry block, do so now. 701 severSplitPHINodes(header); 702 703 // If we have any return instructions in the region, split those blocks so 704 // that the return is not in the region. 705 splitReturnBlocks(); 706 707 Function *oldFunction = header->getParent(); 708 709 // This takes place of the original loop 710 BasicBlock *codeReplacer = BasicBlock::Create(header->getContext(), 711 "codeRepl", oldFunction, 712 header); 713 714 // The new function needs a root node because other nodes can branch to the 715 // head of the region, but the entry node of a function cannot have preds. 716 BasicBlock *newFuncRoot = BasicBlock::Create(header->getContext(), 717 "newFuncRoot"); 718 newFuncRoot->getInstList().push_back(BranchInst::Create(header)); 719 720 // Find inputs to, outputs from the code region. 721 findInputsOutputs(inputs, outputs); 722 723 SmallPtrSet<BasicBlock *, 1> ExitBlocks; 724 for (SetVector<BasicBlock *>::iterator I = Blocks.begin(), E = Blocks.end(); 725 I != E; ++I) 726 for (succ_iterator SI = succ_begin(*I), SE = succ_end(*I); SI != SE; ++SI) 727 if (!Blocks.count(*SI)) 728 ExitBlocks.insert(*SI); 729 NumExitBlocks = ExitBlocks.size(); 730 731 // Construct new function based on inputs/outputs & add allocas for all defs. 732 Function *newFunction = constructFunction(inputs, outputs, header, 733 newFuncRoot, 734 codeReplacer, oldFunction, 735 oldFunction->getParent()); 736 737 emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs); 738 739 moveCodeToFunction(newFunction); 740 741 // Loop over all of the PHI nodes in the header block, and change any 742 // references to the old incoming edge to be the new incoming edge. 743 for (BasicBlock::iterator I = header->begin(); isa<PHINode>(I); ++I) { 744 PHINode *PN = cast<PHINode>(I); 745 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 746 if (!Blocks.count(PN->getIncomingBlock(i))) 747 PN->setIncomingBlock(i, newFuncRoot); 748 } 749 750 // Look at all successors of the codeReplacer block. If any of these blocks 751 // had PHI nodes in them, we need to update the "from" block to be the code 752 // replacer, not the original block in the extracted region. 753 std::vector<BasicBlock*> Succs(succ_begin(codeReplacer), 754 succ_end(codeReplacer)); 755 for (unsigned i = 0, e = Succs.size(); i != e; ++i) 756 for (BasicBlock::iterator I = Succs[i]->begin(); isa<PHINode>(I); ++I) { 757 PHINode *PN = cast<PHINode>(I); 758 std::set<BasicBlock*> ProcessedPreds; 759 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 760 if (Blocks.count(PN->getIncomingBlock(i))) { 761 if (ProcessedPreds.insert(PN->getIncomingBlock(i)).second) 762 PN->setIncomingBlock(i, codeReplacer); 763 else { 764 // There were multiple entries in the PHI for this block, now there 765 // is only one, so remove the duplicated entries. 766 PN->removeIncomingValue(i, false); 767 --i; --e; 768 } 769 } 770 } 771 772 //cerr << "NEW FUNCTION: " << *newFunction; 773 // verifyFunction(*newFunction); 774 775 // cerr << "OLD FUNCTION: " << *oldFunction; 776 // verifyFunction(*oldFunction); 777 778 DEBUG(if (verifyFunction(*newFunction)) 779 report_fatal_error("verifyFunction failed!")); 780 return newFunction; 781} 782