LoopUnswitch.cpp revision 7f8897f22e88271cfa114998a4d6088e7c8e8e11
1//===-- LoopUnswitch.cpp - Hoist loop-invariant conditionals in loop ------===// 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 pass transforms loops that contain branches on loop-invariant conditions 11// to have multiple loops. For example, it turns the left into the right code: 12// 13// for (...) if (lic) 14// A for (...) 15// if (lic) A; B; C 16// B else 17// C for (...) 18// A; C 19// 20// This can increase the size of the code exponentially (doubling it every time 21// a loop is unswitched) so we only unswitch if the resultant code will be 22// smaller than a threshold. 23// 24// This pass expects LICM to be run before it to hoist invariant conditions out 25// of the loop, to make the unswitching opportunity obvious. 26// 27//===----------------------------------------------------------------------===// 28 29#define DEBUG_TYPE "loop-unswitch" 30#include "llvm/Transforms/Scalar.h" 31#include "llvm/Constants.h" 32#include "llvm/Function.h" 33#include "llvm/Instructions.h" 34#include "llvm/Analysis/LoopInfo.h" 35#include "llvm/Transforms/Utils/Cloning.h" 36#include "llvm/Transforms/Utils/Local.h" 37#include "llvm/Transforms/Utils/BasicBlockUtils.h" 38#include "llvm/ADT/Statistic.h" 39#include "llvm/ADT/PostOrderIterator.h" 40#include "llvm/Support/Debug.h" 41#include "llvm/Support/CommandLine.h" 42#include <algorithm> 43#include <iostream> 44#include <set> 45using namespace llvm; 46 47namespace { 48 Statistic<> NumBranches("loop-unswitch", "Number of branches unswitched"); 49 Statistic<> NumSwitches("loop-unswitch", "Number of switches unswitched"); 50 Statistic<> NumSelects ("loop-unswitch", "Number of selects unswitched"); 51 Statistic<> NumTrivial ("loop-unswitch", 52 "Number of unswitches that are trivial"); 53 Statistic<> NumSimplify("loop-unswitch", 54 "Number of simplifications of unswitched code"); 55 cl::opt<unsigned> 56 Threshold("loop-unswitch-threshold", cl::desc("Max loop size to unswitch"), 57 cl::init(10), cl::Hidden); 58 59 class LoopUnswitch : public FunctionPass { 60 LoopInfo *LI; // Loop information 61 62 // LoopProcessWorklist - List of loops we need to process. 63 std::vector<Loop*> LoopProcessWorklist; 64 public: 65 virtual bool runOnFunction(Function &F); 66 bool visitLoop(Loop *L); 67 68 /// This transformation requires natural loop information & requires that 69 /// loop preheaders be inserted into the CFG... 70 /// 71 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 72 AU.addRequiredID(LoopSimplifyID); 73 AU.addPreservedID(LoopSimplifyID); 74 AU.addRequired<LoopInfo>(); 75 AU.addPreserved<LoopInfo>(); 76 AU.addRequiredID(LCSSAID); 77 AU.addPreservedID(LCSSAID); 78 } 79 80 private: 81 /// RemoveLoopFromWorklist - If the specified loop is on the loop worklist, 82 /// remove it. 83 void RemoveLoopFromWorklist(Loop *L) { 84 std::vector<Loop*>::iterator I = std::find(LoopProcessWorklist.begin(), 85 LoopProcessWorklist.end(), L); 86 if (I != LoopProcessWorklist.end()) 87 LoopProcessWorklist.erase(I); 88 } 89 90 bool UnswitchIfProfitable(Value *LoopCond, Constant *Val,Loop *L); 91 unsigned getLoopUnswitchCost(Loop *L, Value *LIC); 92 void UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val, 93 BasicBlock *ExitBlock); 94 void UnswitchNontrivialCondition(Value *LIC, Constant *OnVal, Loop *L); 95 BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To); 96 BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt); 97 98 void RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC, 99 Constant *Val, bool isEqual); 100 101 void SimplifyCode(std::vector<Instruction*> &Worklist); 102 void RemoveBlockIfDead(BasicBlock *BB, 103 std::vector<Instruction*> &Worklist); 104 void RemoveLoopFromHierarchy(Loop *L); 105 }; 106 RegisterPass<LoopUnswitch> X("loop-unswitch", "Unswitch loops"); 107} 108 109FunctionPass *llvm::createLoopUnswitchPass() { return new LoopUnswitch(); } 110 111bool LoopUnswitch::runOnFunction(Function &F) { 112 bool Changed = false; 113 LI = &getAnalysis<LoopInfo>(); 114 115 // Populate the worklist of loops to process in post-order. 116 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) 117 for (po_iterator<Loop*> LI = po_begin(*I), E = po_end(*I); LI != E; ++LI) 118 LoopProcessWorklist.push_back(*LI); 119 120 // Process the loops in worklist order, this is a post-order visitation of 121 // the loops. We use a worklist of loops so that loops can be removed at any 122 // time if they are deleted (e.g. the backedge of a loop is removed). 123 while (!LoopProcessWorklist.empty()) { 124 Loop *L = LoopProcessWorklist.back(); 125 LoopProcessWorklist.pop_back(); 126 Changed |= visitLoop(L); 127 } 128 129 return Changed; 130} 131 132/// FindLIVLoopCondition - Cond is a condition that occurs in L. If it is 133/// invariant in the loop, or has an invariant piece, return the invariant. 134/// Otherwise, return null. 135static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) { 136 // Constants should be folded, not unswitched on! 137 if (isa<Constant>(Cond)) return false; 138 139 // TODO: Handle: br (VARIANT|INVARIANT). 140 // TODO: Hoist simple expressions out of loops. 141 if (L->isLoopInvariant(Cond)) return Cond; 142 143 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Cond)) 144 if (BO->getOpcode() == Instruction::And || 145 BO->getOpcode() == Instruction::Or) { 146 // If either the left or right side is invariant, we can unswitch on this, 147 // which will cause the branch to go away in one loop and the condition to 148 // simplify in the other one. 149 if (Value *LHS = FindLIVLoopCondition(BO->getOperand(0), L, Changed)) 150 return LHS; 151 if (Value *RHS = FindLIVLoopCondition(BO->getOperand(1), L, Changed)) 152 return RHS; 153 } 154 155 return 0; 156} 157 158bool LoopUnswitch::visitLoop(Loop *L) { 159 assert(L->isLCSSAForm()); 160 161 bool Changed = false; 162 163 // Loop over all of the basic blocks in the loop. If we find an interior 164 // block that is branching on a loop-invariant condition, we can unswitch this 165 // loop. 166 for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 167 I != E; ++I) { 168 TerminatorInst *TI = (*I)->getTerminator(); 169 if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { 170 // If this isn't branching on an invariant condition, we can't unswitch 171 // it. 172 if (BI->isConditional()) { 173 // See if this, or some part of it, is loop invariant. If so, we can 174 // unswitch on it if we desire. 175 Value *LoopCond = FindLIVLoopCondition(BI->getCondition(), L, Changed); 176 if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantBool::True, L)) { 177 ++NumBranches; 178 return true; 179 } 180 } 181 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { 182 Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), L, Changed); 183 if (LoopCond && SI->getNumCases() > 1) { 184 // Find a value to unswitch on: 185 // FIXME: this should chose the most expensive case! 186 Constant *UnswitchVal = SI->getCaseValue(1); 187 if (UnswitchIfProfitable(LoopCond, UnswitchVal, L)) { 188 ++NumSwitches; 189 return true; 190 } 191 } 192 } 193 194 // Scan the instructions to check for unswitchable values. 195 for (BasicBlock::iterator BBI = (*I)->begin(), E = (*I)->end(); 196 BBI != E; ++BBI) 197 if (SelectInst *SI = dyn_cast<SelectInst>(BBI)) { 198 Value *LoopCond = FindLIVLoopCondition(SI->getCondition(), L, Changed); 199 if (LoopCond && UnswitchIfProfitable(LoopCond, ConstantBool::True, L)) { 200 ++NumSelects; 201 return true; 202 } 203 } 204 } 205 206 assert(L->isLCSSAForm()); 207 208 return Changed; 209} 210 211/// isTrivialLoopExitBlock - Check to see if all paths from BB either: 212/// 1. Exit the loop with no side effects. 213/// 2. Branch to the latch block with no side-effects. 214/// 215/// If these conditions are true, we return true and set ExitBB to the block we 216/// exit through. 217/// 218static bool isTrivialLoopExitBlockHelper(Loop *L, BasicBlock *BB, 219 BasicBlock *&ExitBB, 220 std::set<BasicBlock*> &Visited) { 221 if (!Visited.insert(BB).second) { 222 // Already visited and Ok, end of recursion. 223 return true; 224 } else if (!L->contains(BB)) { 225 // Otherwise, this is a loop exit, this is fine so long as this is the 226 // first exit. 227 if (ExitBB != 0) return false; 228 ExitBB = BB; 229 return true; 230 } 231 232 // Otherwise, this is an unvisited intra-loop node. Check all successors. 233 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) { 234 // Check to see if the successor is a trivial loop exit. 235 if (!isTrivialLoopExitBlockHelper(L, *SI, ExitBB, Visited)) 236 return false; 237 } 238 239 // Okay, everything after this looks good, check to make sure that this block 240 // doesn't include any side effects. 241 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 242 if (I->mayWriteToMemory()) 243 return false; 244 245 return true; 246} 247 248/// isTrivialLoopExitBlock - Return true if the specified block unconditionally 249/// leads to an exit from the specified loop, and has no side-effects in the 250/// process. If so, return the block that is exited to, otherwise return null. 251static BasicBlock *isTrivialLoopExitBlock(Loop *L, BasicBlock *BB) { 252 std::set<BasicBlock*> Visited; 253 Visited.insert(L->getHeader()); // Branches to header are ok. 254 BasicBlock *ExitBB = 0; 255 if (isTrivialLoopExitBlockHelper(L, BB, ExitBB, Visited)) 256 return ExitBB; 257 return 0; 258} 259 260/// IsTrivialUnswitchCondition - Check to see if this unswitch condition is 261/// trivial: that is, that the condition controls whether or not the loop does 262/// anything at all. If this is a trivial condition, unswitching produces no 263/// code duplications (equivalently, it produces a simpler loop and a new empty 264/// loop, which gets deleted). 265/// 266/// If this is a trivial condition, return true, otherwise return false. When 267/// returning true, this sets Cond and Val to the condition that controls the 268/// trivial condition: when Cond dynamically equals Val, the loop is known to 269/// exit. Finally, this sets LoopExit to the BB that the loop exits to when 270/// Cond == Val. 271/// 272static bool IsTrivialUnswitchCondition(Loop *L, Value *Cond, Constant **Val = 0, 273 BasicBlock **LoopExit = 0) { 274 BasicBlock *Header = L->getHeader(); 275 TerminatorInst *HeaderTerm = Header->getTerminator(); 276 277 BasicBlock *LoopExitBB = 0; 278 if (BranchInst *BI = dyn_cast<BranchInst>(HeaderTerm)) { 279 // If the header block doesn't end with a conditional branch on Cond, we 280 // can't handle it. 281 if (!BI->isConditional() || BI->getCondition() != Cond) 282 return false; 283 284 // Check to see if a successor of the branch is guaranteed to go to the 285 // latch block or exit through a one exit block without having any 286 // side-effects. If so, determine the value of Cond that causes it to do 287 // this. 288 if ((LoopExitBB = isTrivialLoopExitBlock(L, BI->getSuccessor(0)))) { 289 if (Val) *Val = ConstantBool::True; 290 } else if ((LoopExitBB = isTrivialLoopExitBlock(L, BI->getSuccessor(1)))) { 291 if (Val) *Val = ConstantBool::False; 292 } 293 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(HeaderTerm)) { 294 // If this isn't a switch on Cond, we can't handle it. 295 if (SI->getCondition() != Cond) return false; 296 297 // Check to see if a successor of the switch is guaranteed to go to the 298 // latch block or exit through a one exit block without having any 299 // side-effects. If so, determine the value of Cond that causes it to do 300 // this. Note that we can't trivially unswitch on the default case. 301 for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) 302 if ((LoopExitBB = isTrivialLoopExitBlock(L, SI->getSuccessor(i)))) { 303 // Okay, we found a trivial case, remember the value that is trivial. 304 if (Val) *Val = SI->getCaseValue(i); 305 break; 306 } 307 } 308 309 // If we didn't find a single unique LoopExit block, or if the loop exit block 310 // contains phi nodes, this isn't trivial. 311 if (!LoopExitBB || isa<PHINode>(LoopExitBB->begin())) 312 return false; // Can't handle this. 313 314 if (LoopExit) *LoopExit = LoopExitBB; 315 316 // We already know that nothing uses any scalar values defined inside of this 317 // loop. As such, we just have to check to see if this loop will execute any 318 // side-effecting instructions (e.g. stores, calls, volatile loads) in the 319 // part of the loop that the code *would* execute. We already checked the 320 // tail, check the header now. 321 for (BasicBlock::iterator I = Header->begin(), E = Header->end(); I != E; ++I) 322 if (I->mayWriteToMemory()) 323 return false; 324 return true; 325} 326 327/// getLoopUnswitchCost - Return the cost (code size growth) that will happen if 328/// we choose to unswitch the specified loop on the specified value. 329/// 330unsigned LoopUnswitch::getLoopUnswitchCost(Loop *L, Value *LIC) { 331 // If the condition is trivial, always unswitch. There is no code growth for 332 // this case. 333 if (IsTrivialUnswitchCondition(L, LIC)) 334 return 0; 335 336 // FIXME: This is really overly conservative. However, more liberal 337 // estimations have thus far resulted in excessive unswitching, which is bad 338 // both in compile time and in code size. This should be replaced once 339 // someone figures out how a good estimation. 340 return L->getBlocks().size(); 341 342 unsigned Cost = 0; 343 // FIXME: this is brain dead. It should take into consideration code 344 // shrinkage. 345 for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 346 I != E; ++I) { 347 BasicBlock *BB = *I; 348 // Do not include empty blocks in the cost calculation. This happen due to 349 // loop canonicalization and will be removed. 350 if (BB->begin() == BasicBlock::iterator(BB->getTerminator())) 351 continue; 352 353 // Count basic blocks. 354 ++Cost; 355 } 356 357 return Cost; 358} 359 360/// UnswitchIfProfitable - We have found that we can unswitch L when 361/// LoopCond == Val to simplify the loop. If we decide that this is profitable, 362/// unswitch the loop, reprocess the pieces, then return true. 363bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val,Loop *L){ 364 // Check to see if it would be profitable to unswitch this loop. 365 unsigned Cost = getLoopUnswitchCost(L, LoopCond); 366 if (Cost > Threshold) { 367 // FIXME: this should estimate growth by the amount of code shared by the 368 // resultant unswitched loops. 369 // 370 DEBUG(std::cerr << "NOT unswitching loop %" 371 << L->getHeader()->getName() << ", cost too high: " 372 << L->getBlocks().size() << "\n"); 373 return false; 374 } 375 376 // If this is a trivial condition to unswitch (which results in no code 377 // duplication), do it now. 378 Constant *CondVal; 379 BasicBlock *ExitBlock; 380 if (IsTrivialUnswitchCondition(L, LoopCond, &CondVal, &ExitBlock)) { 381 UnswitchTrivialCondition(L, LoopCond, CondVal, ExitBlock); 382 } else { 383 UnswitchNontrivialCondition(LoopCond, Val, L); 384 } 385 386 return true; 387} 388 389/// SplitBlock - Split the specified block at the specified instruction - every 390/// thing before SplitPt stays in Old and everything starting with SplitPt moves 391/// to a new block. The two blocks are joined by an unconditional branch and 392/// the loop info is updated. 393/// 394BasicBlock *LoopUnswitch::SplitBlock(BasicBlock *Old, Instruction *SplitPt) { 395 BasicBlock::iterator SplitIt = SplitPt; 396 while (isa<PHINode>(SplitIt)) 397 ++SplitIt; 398 BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split"); 399 400 // The new block lives in whichever loop the old one did. 401 if (Loop *L = LI->getLoopFor(Old)) 402 L->addBasicBlockToLoop(New, *LI); 403 404 return New; 405} 406 407 408BasicBlock *LoopUnswitch::SplitEdge(BasicBlock *BB, BasicBlock *Succ) { 409 TerminatorInst *LatchTerm = BB->getTerminator(); 410 unsigned SuccNum = 0; 411 for (unsigned i = 0, e = LatchTerm->getNumSuccessors(); ; ++i) { 412 assert(i != e && "Didn't find edge?"); 413 if (LatchTerm->getSuccessor(i) == Succ) { 414 SuccNum = i; 415 break; 416 } 417 } 418 419 // If this is a critical edge, let SplitCriticalEdge do it. 420 if (SplitCriticalEdge(BB->getTerminator(), SuccNum, this)) 421 return LatchTerm->getSuccessor(SuccNum); 422 423 // If the edge isn't critical, then BB has a single successor or Succ has a 424 // single pred. Split the block. 425 BasicBlock::iterator SplitPoint; 426 if (BasicBlock *SP = Succ->getSinglePredecessor()) { 427 // If the successor only has a single pred, split the top of the successor 428 // block. 429 assert(SP == BB && "CFG broken"); 430 return SplitBlock(Succ, Succ->begin()); 431 } else { 432 // Otherwise, if BB has a single successor, split it at the bottom of the 433 // block. 434 assert(BB->getTerminator()->getNumSuccessors() == 1 && 435 "Should have a single succ!"); 436 return SplitBlock(BB, BB->getTerminator()); 437 } 438} 439 440 441 442// RemapInstruction - Convert the instruction operands from referencing the 443// current values into those specified by ValueMap. 444// 445static inline void RemapInstruction(Instruction *I, 446 std::map<const Value *, Value*> &ValueMap) { 447 for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) { 448 Value *Op = I->getOperand(op); 449 std::map<const Value *, Value*>::iterator It = ValueMap.find(Op); 450 if (It != ValueMap.end()) Op = It->second; 451 I->setOperand(op, Op); 452 } 453} 454 455/// CloneLoop - Recursively clone the specified loop and all of its children, 456/// mapping the blocks with the specified map. 457static Loop *CloneLoop(Loop *L, Loop *PL, std::map<const Value*, Value*> &VM, 458 LoopInfo *LI) { 459 Loop *New = new Loop(); 460 461 if (PL) 462 PL->addChildLoop(New); 463 else 464 LI->addTopLevelLoop(New); 465 466 // Add all of the blocks in L to the new loop. 467 for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 468 I != E; ++I) 469 if (LI->getLoopFor(*I) == L) 470 New->addBasicBlockToLoop(cast<BasicBlock>(VM[*I]), *LI); 471 472 // Add all of the subloops to the new loop. 473 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) 474 CloneLoop(*I, New, VM, LI); 475 476 return New; 477} 478 479/// EmitPreheaderBranchOnCondition - Emit a conditional branch on two values 480/// if LIC == Val, branch to TrueDst, otherwise branch to FalseDest. Insert the 481/// code immediately before InsertPt. 482static void EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val, 483 BasicBlock *TrueDest, 484 BasicBlock *FalseDest, 485 Instruction *InsertPt) { 486 // Insert a conditional branch on LIC to the two preheaders. The original 487 // code is the true version and the new code is the false version. 488 Value *BranchVal = LIC; 489 if (!isa<ConstantBool>(Val)) { 490 BranchVal = BinaryOperator::createSetEQ(LIC, Val, "tmp", InsertPt); 491 } else if (Val != ConstantBool::True) { 492 // We want to enter the new loop when the condition is true. 493 std::swap(TrueDest, FalseDest); 494 } 495 496 // Insert the new branch. 497 new BranchInst(TrueDest, FalseDest, BranchVal, InsertPt); 498} 499 500 501/// UnswitchTrivialCondition - Given a loop that has a trivial unswitchable 502/// condition in it (a cond branch from its header block to its latch block, 503/// where the path through the loop that doesn't execute its body has no 504/// side-effects), unswitch it. This doesn't involve any code duplication, just 505/// moving the conditional branch outside of the loop and updating loop info. 506void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond, 507 Constant *Val, 508 BasicBlock *ExitBlock) { 509 DEBUG(std::cerr << "loop-unswitch: Trivial-Unswitch loop %" 510 << L->getHeader()->getName() << " [" << L->getBlocks().size() 511 << " blocks] in Function " << L->getHeader()->getParent()->getName() 512 << " on cond: " << *Val << " == " << *Cond << "\n"); 513 514 // First step, split the preheader, so that we know that there is a safe place 515 // to insert the conditional branch. We will change 'OrigPH' to have a 516 // conditional branch on Cond. 517 BasicBlock *OrigPH = L->getLoopPreheader(); 518 BasicBlock *NewPH = SplitEdge(OrigPH, L->getHeader()); 519 520 // Now that we have a place to insert the conditional branch, create a place 521 // to branch to: this is the exit block out of the loop that we should 522 // short-circuit to. 523 524 // Split this block now, so that the loop maintains its exit block, and so 525 // that the jump from the preheader can execute the contents of the exit block 526 // without actually branching to it (the exit block should be dominated by the 527 // loop header, not the preheader). 528 assert(!L->contains(ExitBlock) && "Exit block is in the loop?"); 529 BasicBlock *NewExit = SplitBlock(ExitBlock, ExitBlock->begin()); 530 531 // Okay, now we have a position to branch from and a position to branch to, 532 // insert the new conditional branch. 533 EmitPreheaderBranchOnCondition(Cond, Val, NewExit, NewPH, 534 OrigPH->getTerminator()); 535 OrigPH->getTerminator()->eraseFromParent(); 536 537 // We need to reprocess this loop, it could be unswitched again. 538 LoopProcessWorklist.push_back(L); 539 540 // Now that we know that the loop is never entered when this condition is a 541 // particular value, rewrite the loop with this info. We know that this will 542 // at least eliminate the old branch. 543 RewriteLoopBodyWithConditionConstant(L, Cond, Val, false); 544 ++NumTrivial; 545} 546 547 548/// VersionLoop - We determined that the loop is profitable to unswitch when LIC 549/// equal Val. Split it into loop versions and test the condition outside of 550/// either loop. Return the loops created as Out1/Out2. 551void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val, 552 Loop *L) { 553 Function *F = L->getHeader()->getParent(); 554 DEBUG(std::cerr << "loop-unswitch: Unswitching loop %" 555 << L->getHeader()->getName() << " [" << L->getBlocks().size() 556 << " blocks] in Function " << F->getName() 557 << " when '" << *Val << "' == " << *LIC << "\n"); 558 559 // LoopBlocks contains all of the basic blocks of the loop, including the 560 // preheader of the loop, the body of the loop, and the exit blocks of the 561 // loop, in that order. 562 std::vector<BasicBlock*> LoopBlocks; 563 564 // First step, split the preheader and exit blocks, and add these blocks to 565 // the LoopBlocks list. 566 BasicBlock *OrigPreheader = L->getLoopPreheader(); 567 LoopBlocks.push_back(SplitEdge(OrigPreheader, L->getHeader())); 568 569 // We want the loop to come after the preheader, but before the exit blocks. 570 LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end()); 571 572 std::vector<BasicBlock*> ExitBlocks; 573 L->getExitBlocks(ExitBlocks); 574 std::sort(ExitBlocks.begin(), ExitBlocks.end()); 575 ExitBlocks.erase(std::unique(ExitBlocks.begin(), ExitBlocks.end()), 576 ExitBlocks.end()); 577 578 // Split all of the edges from inside the loop to their exit blocks. Update 579 // the appropriate Phi nodes as we do so. 580 unsigned NumBlocks = L->getBlocks().size(); 581 582 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 583 BasicBlock *ExitBlock = ExitBlocks[i]; 584 std::vector<BasicBlock*> Preds(pred_begin(ExitBlock), pred_end(ExitBlock)); 585 586 for (unsigned j = 0, e = Preds.size(); j != e; ++j) { 587 assert(L->contains(Preds[j]) && 588 "All preds of loop exit blocks must be the same loop!"); 589 BasicBlock* MiddleBlock = SplitEdge(Preds[j], ExitBlock); 590 BasicBlock* StartBlock = Preds[j]; 591 BasicBlock* EndBlock; 592 if (MiddleBlock->getSinglePredecessor() == ExitBlock) { 593 EndBlock = MiddleBlock; 594 MiddleBlock = EndBlock->getSinglePredecessor();; 595 } else { 596 EndBlock = ExitBlock; 597 } 598 599 std::set<PHINode*> InsertedPHIs; 600 PHINode* OldLCSSA = 0; 601 for (BasicBlock::iterator I = EndBlock->begin(); 602 (OldLCSSA = dyn_cast<PHINode>(I)); ++I) { 603 Value* OldValue = OldLCSSA->getIncomingValueForBlock(MiddleBlock); 604 PHINode* NewLCSSA = new PHINode(OldLCSSA->getType(), 605 OldLCSSA->getName() + ".us-lcssa", 606 MiddleBlock->getTerminator()); 607 NewLCSSA->addIncoming(OldValue, StartBlock); 608 OldLCSSA->setIncomingValue(OldLCSSA->getBasicBlockIndex(MiddleBlock), 609 NewLCSSA); 610 InsertedPHIs.insert(NewLCSSA); 611 } 612 613 BasicBlock::iterator InsertPt = EndBlock->begin(); 614 while (dyn_cast<PHINode>(InsertPt)) ++InsertPt; 615 for (BasicBlock::iterator I = MiddleBlock->begin(); 616 (OldLCSSA = dyn_cast<PHINode>(I)) && InsertedPHIs.count(OldLCSSA) == 0; 617 ++I) { 618 PHINode *NewLCSSA = new PHINode(OldLCSSA->getType(), 619 OldLCSSA->getName() + ".us-lcssa", 620 InsertPt); 621 OldLCSSA->replaceAllUsesWith(NewLCSSA); 622 NewLCSSA->addIncoming(OldLCSSA, MiddleBlock); 623 } 624 } 625 } 626 627 // The exit blocks may have been changed due to edge splitting, recompute. 628 ExitBlocks.clear(); 629 L->getExitBlocks(ExitBlocks); 630 std::sort(ExitBlocks.begin(), ExitBlocks.end()); 631 ExitBlocks.erase(std::unique(ExitBlocks.begin(), ExitBlocks.end()), 632 ExitBlocks.end()); 633 634 // Add exit blocks to the loop blocks. 635 LoopBlocks.insert(LoopBlocks.end(), ExitBlocks.begin(), ExitBlocks.end()); 636 637 // Next step, clone all of the basic blocks that make up the loop (including 638 // the loop preheader and exit blocks), keeping track of the mapping between 639 // the instructions and blocks. 640 std::vector<BasicBlock*> NewBlocks; 641 NewBlocks.reserve(LoopBlocks.size()); 642 std::map<const Value*, Value*> ValueMap; 643 for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) { 644 BasicBlock *New = CloneBasicBlock(LoopBlocks[i], ValueMap, ".us", F); 645 NewBlocks.push_back(New); 646 ValueMap[LoopBlocks[i]] = New; // Keep the BB mapping. 647 } 648 649 // Splice the newly inserted blocks into the function right before the 650 // original preheader. 651 F->getBasicBlockList().splice(LoopBlocks[0], F->getBasicBlockList(), 652 NewBlocks[0], F->end()); 653 654 // Now we create the new Loop object for the versioned loop. 655 Loop *NewLoop = CloneLoop(L, L->getParentLoop(), ValueMap, LI); 656 Loop *ParentLoop = L->getParentLoop(); 657 if (ParentLoop) { 658 // Make sure to add the cloned preheader and exit blocks to the parent loop 659 // as well. 660 ParentLoop->addBasicBlockToLoop(NewBlocks[0], *LI); 661 } 662 663 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) { 664 BasicBlock *NewExit = cast<BasicBlock>(ValueMap[ExitBlocks[i]]); 665 // The new exit block should be in the same loop as the old one. 666 if (Loop *ExitBBLoop = LI->getLoopFor(ExitBlocks[i])) 667 ExitBBLoop->addBasicBlockToLoop(NewExit, *LI); 668 669 assert(NewExit->getTerminator()->getNumSuccessors() == 1 && 670 "Exit block should have been split to have one successor!"); 671 BasicBlock *ExitSucc = NewExit->getTerminator()->getSuccessor(0); 672 673 // If the successor of the exit block had PHI nodes, add an entry for 674 // NewExit. 675 PHINode *PN; 676 for (BasicBlock::iterator I = ExitSucc->begin(); 677 (PN = dyn_cast<PHINode>(I)); ++I) { 678 Value *V = PN->getIncomingValueForBlock(ExitBlocks[i]); 679 std::map<const Value *, Value*>::iterator It = ValueMap.find(V); 680 if (It != ValueMap.end()) V = It->second; 681 PN->addIncoming(V, NewExit); 682 } 683 } 684 685 // Rewrite the code to refer to itself. 686 for (unsigned i = 0, e = NewBlocks.size(); i != e; ++i) 687 for (BasicBlock::iterator I = NewBlocks[i]->begin(), 688 E = NewBlocks[i]->end(); I != E; ++I) 689 RemapInstruction(I, ValueMap); 690 691 // Rewrite the original preheader to select between versions of the loop. 692 BranchInst *OldBR = cast<BranchInst>(OrigPreheader->getTerminator()); 693 assert(OldBR->isUnconditional() && OldBR->getSuccessor(0) == LoopBlocks[0] && 694 "Preheader splitting did not work correctly!"); 695 696 // Emit the new branch that selects between the two versions of this loop. 697 EmitPreheaderBranchOnCondition(LIC, Val, NewBlocks[0], LoopBlocks[0], OldBR); 698 OldBR->eraseFromParent(); 699 700 LoopProcessWorklist.push_back(L); 701 LoopProcessWorklist.push_back(NewLoop); 702 703 // Now we rewrite the original code to know that the condition is true and the 704 // new code to know that the condition is false. 705 RewriteLoopBodyWithConditionConstant(L , LIC, Val, false); 706 707 // It's possible that simplifying one loop could cause the other to be 708 // deleted. If so, don't simplify it. 709 if (!LoopProcessWorklist.empty() && LoopProcessWorklist.back() == NewLoop) 710 RewriteLoopBodyWithConditionConstant(NewLoop, LIC, Val, true); 711} 712 713/// RemoveFromWorklist - Remove all instances of I from the worklist vector 714/// specified. 715static void RemoveFromWorklist(Instruction *I, 716 std::vector<Instruction*> &Worklist) { 717 std::vector<Instruction*>::iterator WI = std::find(Worklist.begin(), 718 Worklist.end(), I); 719 while (WI != Worklist.end()) { 720 unsigned Offset = WI-Worklist.begin(); 721 Worklist.erase(WI); 722 WI = std::find(Worklist.begin()+Offset, Worklist.end(), I); 723 } 724} 725 726/// ReplaceUsesOfWith - When we find that I really equals V, remove I from the 727/// program, replacing all uses with V and update the worklist. 728static void ReplaceUsesOfWith(Instruction *I, Value *V, 729 std::vector<Instruction*> &Worklist) { 730 DEBUG(std::cerr << "Replace with '" << *V << "': " << *I); 731 732 // Add uses to the worklist, which may be dead now. 733 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 734 if (Instruction *Use = dyn_cast<Instruction>(I->getOperand(i))) 735 Worklist.push_back(Use); 736 737 // Add users to the worklist which may be simplified now. 738 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); 739 UI != E; ++UI) 740 Worklist.push_back(cast<Instruction>(*UI)); 741 I->replaceAllUsesWith(V); 742 I->eraseFromParent(); 743 RemoveFromWorklist(I, Worklist); 744 ++NumSimplify; 745} 746 747/// RemoveBlockIfDead - If the specified block is dead, remove it, update loop 748/// information, and remove any dead successors it has. 749/// 750void LoopUnswitch::RemoveBlockIfDead(BasicBlock *BB, 751 std::vector<Instruction*> &Worklist) { 752 if (pred_begin(BB) != pred_end(BB)) { 753 // This block isn't dead, since an edge to BB was just removed, see if there 754 // are any easy simplifications we can do now. 755 if (BasicBlock *Pred = BB->getSinglePredecessor()) { 756 // If it has one pred, fold phi nodes in BB. 757 while (isa<PHINode>(BB->begin())) 758 ReplaceUsesOfWith(BB->begin(), 759 cast<PHINode>(BB->begin())->getIncomingValue(0), 760 Worklist); 761 762 // If this is the header of a loop and the only pred is the latch, we now 763 // have an unreachable loop. 764 if (Loop *L = LI->getLoopFor(BB)) 765 if (L->getHeader() == BB && L->contains(Pred)) { 766 // Remove the branch from the latch to the header block, this makes 767 // the header dead, which will make the latch dead (because the header 768 // dominates the latch). 769 Pred->getTerminator()->eraseFromParent(); 770 new UnreachableInst(Pred); 771 772 // The loop is now broken, remove it from LI. 773 RemoveLoopFromHierarchy(L); 774 775 // Reprocess the header, which now IS dead. 776 RemoveBlockIfDead(BB, Worklist); 777 return; 778 } 779 780 // If pred ends in a uncond branch, add uncond branch to worklist so that 781 // the two blocks will get merged. 782 if (BranchInst *BI = dyn_cast<BranchInst>(Pred->getTerminator())) 783 if (BI->isUnconditional()) 784 Worklist.push_back(BI); 785 } 786 return; 787 } 788 789 DEBUG(std::cerr << "Nuking dead block: " << *BB); 790 791 // Remove the instructions in the basic block from the worklist. 792 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 793 RemoveFromWorklist(I, Worklist); 794 795 // Anything that uses the instructions in this basic block should have their 796 // uses replaced with undefs. 797 if (!I->use_empty()) 798 I->replaceAllUsesWith(UndefValue::get(I->getType())); 799 } 800 801 // If this is the edge to the header block for a loop, remove the loop and 802 // promote all subloops. 803 if (Loop *BBLoop = LI->getLoopFor(BB)) { 804 if (BBLoop->getLoopLatch() == BB) 805 RemoveLoopFromHierarchy(BBLoop); 806 } 807 808 // Remove the block from the loop info, which removes it from any loops it 809 // was in. 810 LI->removeBlock(BB); 811 812 813 // Remove phi node entries in successors for this block. 814 TerminatorInst *TI = BB->getTerminator(); 815 std::vector<BasicBlock*> Succs; 816 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) { 817 Succs.push_back(TI->getSuccessor(i)); 818 TI->getSuccessor(i)->removePredecessor(BB); 819 } 820 821 // Unique the successors, remove anything with multiple uses. 822 std::sort(Succs.begin(), Succs.end()); 823 Succs.erase(std::unique(Succs.begin(), Succs.end()), Succs.end()); 824 825 // Remove the basic block, including all of the instructions contained in it. 826 BB->eraseFromParent(); 827 828 // Remove successor blocks here that are not dead, so that we know we only 829 // have dead blocks in this list. Nondead blocks have a way of becoming dead, 830 // then getting removed before we revisit them, which is badness. 831 // 832 for (unsigned i = 0; i != Succs.size(); ++i) 833 if (pred_begin(Succs[i]) != pred_end(Succs[i])) { 834 // One exception is loop headers. If this block was the preheader for a 835 // loop, then we DO want to visit the loop so the loop gets deleted. 836 // We know that if the successor is a loop header, that this loop had to 837 // be the preheader: the case where this was the latch block was handled 838 // above and headers can only have two predecessors. 839 if (!LI->isLoopHeader(Succs[i])) { 840 Succs.erase(Succs.begin()+i); 841 --i; 842 } 843 } 844 845 for (unsigned i = 0, e = Succs.size(); i != e; ++i) 846 RemoveBlockIfDead(Succs[i], Worklist); 847} 848 849/// RemoveLoopFromHierarchy - We have discovered that the specified loop has 850/// become unwrapped, either because the backedge was deleted, or because the 851/// edge into the header was removed. If the edge into the header from the 852/// latch block was removed, the loop is unwrapped but subloops are still alive, 853/// so they just reparent loops. If the loops are actually dead, they will be 854/// removed later. 855void LoopUnswitch::RemoveLoopFromHierarchy(Loop *L) { 856 if (Loop *ParentLoop = L->getParentLoop()) { // Not a top-level loop. 857 // Reparent all of the blocks in this loop. Since BBLoop had a parent, 858 // they are now all in it. 859 for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 860 I != E; ++I) 861 if (LI->getLoopFor(*I) == L) // Don't change blocks in subloops. 862 LI->changeLoopFor(*I, ParentLoop); 863 864 // Remove the loop from its parent loop. 865 for (Loop::iterator I = ParentLoop->begin(), E = ParentLoop->end();; 866 ++I) { 867 assert(I != E && "Couldn't find loop"); 868 if (*I == L) { 869 ParentLoop->removeChildLoop(I); 870 break; 871 } 872 } 873 874 // Move all subloops into the parent loop. 875 while (L->begin() != L->end()) 876 ParentLoop->addChildLoop(L->removeChildLoop(L->end()-1)); 877 } else { 878 // Reparent all of the blocks in this loop. Since BBLoop had no parent, 879 // they no longer in a loop at all. 880 881 for (unsigned i = 0; i != L->getBlocks().size(); ++i) { 882 // Don't change blocks in subloops. 883 if (LI->getLoopFor(L->getBlocks()[i]) == L) { 884 LI->removeBlock(L->getBlocks()[i]); 885 --i; 886 } 887 } 888 889 // Remove the loop from the top-level LoopInfo object. 890 for (LoopInfo::iterator I = LI->begin(), E = LI->end();; ++I) { 891 assert(I != E && "Couldn't find loop"); 892 if (*I == L) { 893 LI->removeLoop(I); 894 break; 895 } 896 } 897 898 // Move all of the subloops to the top-level. 899 while (L->begin() != L->end()) 900 LI->addTopLevelLoop(L->removeChildLoop(L->end()-1)); 901 } 902 903 delete L; 904 RemoveLoopFromWorklist(L); 905} 906 907 908 909// RewriteLoopBodyWithConditionConstant - We know either that the value LIC has 910// the value specified by Val in the specified loop, or we know it does NOT have 911// that value. Rewrite any uses of LIC or of properties correlated to it. 912void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC, 913 Constant *Val, 914 bool IsEqual) { 915 assert(!isa<Constant>(LIC) && "Why are we unswitching on a constant?"); 916 917 // FIXME: Support correlated properties, like: 918 // for (...) 919 // if (li1 < li2) 920 // ... 921 // if (li1 > li2) 922 // ... 923 924 // FOLD boolean conditions (X|LIC), (X&LIC). Fold conditional branches, 925 // selects, switches. 926 std::vector<User*> Users(LIC->use_begin(), LIC->use_end()); 927 std::vector<Instruction*> Worklist; 928 929 // If we know that LIC == Val, or that LIC == NotVal, just replace uses of LIC 930 // in the loop with the appropriate one directly. 931 if (IsEqual || isa<ConstantBool>(Val)) { 932 Value *Replacement; 933 if (IsEqual) 934 Replacement = Val; 935 else 936 Replacement = ConstantBool::get(!cast<ConstantBool>(Val)->getValue()); 937 938 for (unsigned i = 0, e = Users.size(); i != e; ++i) 939 if (Instruction *U = cast<Instruction>(Users[i])) { 940 if (!L->contains(U->getParent())) 941 continue; 942 U->replaceUsesOfWith(LIC, Replacement); 943 Worklist.push_back(U); 944 } 945 } else { 946 // Otherwise, we don't know the precise value of LIC, but we do know that it 947 // is certainly NOT "Val". As such, simplify any uses in the loop that we 948 // can. This case occurs when we unswitch switch statements. 949 for (unsigned i = 0, e = Users.size(); i != e; ++i) 950 if (Instruction *U = cast<Instruction>(Users[i])) { 951 if (!L->contains(U->getParent())) 952 continue; 953 954 Worklist.push_back(U); 955 956 // If we know that LIC is not Val, use this info to simplify code. 957 if (SwitchInst *SI = dyn_cast<SwitchInst>(U)) { 958 for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i) { 959 if (SI->getCaseValue(i) == Val) { 960 // Found a dead case value. Don't remove PHI nodes in the 961 // successor if they become single-entry, those PHI nodes may 962 // be in the Users list. 963 964 // FIXME: This is a hack. We need to keep the successor around 965 // and hooked up so as to preserve the loop structure, because 966 // trying to update it is complicated. So instead we preserve the 967 // loop structure and put the block on an dead code path. 968 969 BasicBlock* Old = SI->getParent(); 970 BasicBlock* Split = SplitBlock(Old, SI); 971 972 Instruction* OldTerm = Old->getTerminator(); 973 BranchInst* Branch = new BranchInst(Split, 974 SI->getSuccessor(i), 975 ConstantBool::True, 976 OldTerm); 977 978 Old->getTerminator()->eraseFromParent(); 979 980 981 PHINode *PN; 982 for (BasicBlock::iterator II = SI->getSuccessor(i)->begin(); 983 (PN = dyn_cast<PHINode>(II)); ++II) { 984 Value *InVal = PN->removeIncomingValue(Split, false); 985 PN->addIncoming(InVal, Old); 986 } 987 988 SI->removeCase(i); 989 break; 990 } 991 } 992 } 993 994 // TODO: We could do other simplifications, for example, turning 995 // LIC == Val -> false. 996 } 997 } 998 999 SimplifyCode(Worklist); 1000} 1001 1002/// SimplifyCode - Okay, now that we have simplified some instructions in the 1003/// loop, walk over it and constant prop, dce, and fold control flow where 1004/// possible. Note that this is effectively a very simple loop-structure-aware 1005/// optimizer. During processing of this loop, L could very well be deleted, so 1006/// it must not be used. 1007/// 1008/// FIXME: When the loop optimizer is more mature, separate this out to a new 1009/// pass. 1010/// 1011void LoopUnswitch::SimplifyCode(std::vector<Instruction*> &Worklist) { 1012 while (!Worklist.empty()) { 1013 Instruction *I = Worklist.back(); 1014 Worklist.pop_back(); 1015 1016 // Simple constant folding. 1017 if (Constant *C = ConstantFoldInstruction(I)) { 1018 ReplaceUsesOfWith(I, C, Worklist); 1019 continue; 1020 } 1021 1022 // Simple DCE. 1023 if (isInstructionTriviallyDead(I)) { 1024 DEBUG(std::cerr << "Remove dead instruction '" << *I); 1025 1026 // Add uses to the worklist, which may be dead now. 1027 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 1028 if (Instruction *Use = dyn_cast<Instruction>(I->getOperand(i))) 1029 Worklist.push_back(Use); 1030 I->eraseFromParent(); 1031 RemoveFromWorklist(I, Worklist); 1032 ++NumSimplify; 1033 continue; 1034 } 1035 1036 // Special case hacks that appear commonly in unswitched code. 1037 switch (I->getOpcode()) { 1038 case Instruction::Select: 1039 if (ConstantBool *CB = dyn_cast<ConstantBool>(I->getOperand(0))) { 1040 ReplaceUsesOfWith(I, I->getOperand(!CB->getValue()+1), Worklist); 1041 continue; 1042 } 1043 break; 1044 case Instruction::And: 1045 if (isa<ConstantBool>(I->getOperand(0))) // constant -> RHS 1046 cast<BinaryOperator>(I)->swapOperands(); 1047 if (ConstantBool *CB = dyn_cast<ConstantBool>(I->getOperand(1))) { 1048 if (CB->getValue()) // X & 1 -> X 1049 ReplaceUsesOfWith(I, I->getOperand(0), Worklist); 1050 else // X & 0 -> 0 1051 ReplaceUsesOfWith(I, I->getOperand(1), Worklist); 1052 continue; 1053 } 1054 break; 1055 case Instruction::Or: 1056 if (isa<ConstantBool>(I->getOperand(0))) // constant -> RHS 1057 cast<BinaryOperator>(I)->swapOperands(); 1058 if (ConstantBool *CB = dyn_cast<ConstantBool>(I->getOperand(1))) { 1059 if (CB->getValue()) // X | 1 -> 1 1060 ReplaceUsesOfWith(I, I->getOperand(1), Worklist); 1061 else // X | 0 -> X 1062 ReplaceUsesOfWith(I, I->getOperand(0), Worklist); 1063 continue; 1064 } 1065 break; 1066 case Instruction::Br: { 1067 BranchInst *BI = cast<BranchInst>(I); 1068 if (BI->isUnconditional()) { 1069 // If BI's parent is the only pred of the successor, fold the two blocks 1070 // together. 1071 BasicBlock *Pred = BI->getParent(); 1072 BasicBlock *Succ = BI->getSuccessor(0); 1073 BasicBlock *SinglePred = Succ->getSinglePredecessor(); 1074 if (!SinglePred) continue; // Nothing to do. 1075 assert(SinglePred == Pred && "CFG broken"); 1076 1077 DEBUG(std::cerr << "Merging blocks: " << Pred->getName() << " <- " 1078 << Succ->getName() << "\n"); 1079 1080 // Resolve any single entry PHI nodes in Succ. 1081 while (PHINode *PN = dyn_cast<PHINode>(Succ->begin())) 1082 ReplaceUsesOfWith(PN, PN->getIncomingValue(0), Worklist); 1083 1084 // Move all of the successor contents from Succ to Pred. 1085 Pred->getInstList().splice(BI, Succ->getInstList(), Succ->begin(), 1086 Succ->end()); 1087 BI->eraseFromParent(); 1088 RemoveFromWorklist(BI, Worklist); 1089 1090 // If Succ has any successors with PHI nodes, update them to have 1091 // entries coming from Pred instead of Succ. 1092 Succ->replaceAllUsesWith(Pred); 1093 1094 // Remove Succ from the loop tree. 1095 LI->removeBlock(Succ); 1096 Succ->eraseFromParent(); 1097 ++NumSimplify; 1098 } else if (ConstantBool *CB = dyn_cast<ConstantBool>(BI->getCondition())){ 1099 // Conditional branch. Turn it into an unconditional branch, then 1100 // remove dead blocks. 1101 break; // FIXME: Enable. 1102 1103 DEBUG(std::cerr << "Folded branch: " << *BI); 1104 BasicBlock *DeadSucc = BI->getSuccessor(CB->getValue()); 1105 BasicBlock *LiveSucc = BI->getSuccessor(!CB->getValue()); 1106 DeadSucc->removePredecessor(BI->getParent(), true); 1107 Worklist.push_back(new BranchInst(LiveSucc, BI)); 1108 BI->eraseFromParent(); 1109 RemoveFromWorklist(BI, Worklist); 1110 ++NumSimplify; 1111 1112 RemoveBlockIfDead(DeadSucc, Worklist); 1113 } 1114 break; 1115 } 1116 } 1117 } 1118} 1119