1 //===- MergedLoadStoreMotion.cpp - merge and hoist/sink load/stores -------===// 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 //! \file 11 //! \brief This pass performs merges of loads and stores on both sides of a 12 // diamond (hammock). It hoists the loads and sinks the stores. 13 // 14 // The algorithm iteratively hoists two loads to the same address out of a 15 // diamond (hammock) and merges them into a single load in the header. Similar 16 // it sinks and merges two stores to the tail block (footer). The algorithm 17 // iterates over the instructions of one side of the diamond and attempts to 18 // find a matching load/store on the other side. It hoists / sinks when it 19 // thinks it safe to do so. This optimization helps with eg. hiding load 20 // latencies, triggering if-conversion, and reducing static code size. 21 // 22 //===----------------------------------------------------------------------===// 23 // 24 // 25 // Example: 26 // Diamond shaped code before merge: 27 // 28 // header: 29 // br %cond, label %if.then, label %if.else 30 // / \ 31 // / \ 32 // / \ 33 // if.then: if.else: 34 // %lt = load %addr_l %le = load %addr_l 35 // <use %lt> <use %le> 36 // <...> <...> 37 // store %st, %addr_s store %se, %addr_s 38 // br label %if.end br label %if.end 39 // \ / 40 // \ / 41 // \ / 42 // if.end ("footer"): 43 // <...> 44 // 45 // Diamond shaped code after merge: 46 // 47 // header: 48 // %l = load %addr_l 49 // br %cond, label %if.then, label %if.else 50 // / \ 51 // / \ 52 // / \ 53 // if.then: if.else: 54 // <use %l> <use %l> 55 // <...> <...> 56 // br label %if.end br label %if.end 57 // \ / 58 // \ / 59 // \ / 60 // if.end ("footer"): 61 // %s.sink = phi [%st, if.then], [%se, if.else] 62 // <...> 63 // store %s.sink, %addr_s 64 // <...> 65 // 66 // 67 //===----------------------- TODO -----------------------------------------===// 68 // 69 // 1) Generalize to regions other than diamonds 70 // 2) Be more aggressive merging memory operations 71 // Note that both changes require register pressure control 72 // 73 //===----------------------------------------------------------------------===// 74 75 #include "llvm/Transforms/Scalar.h" 76 #include "llvm/ADT/SetVector.h" 77 #include "llvm/ADT/SmallPtrSet.h" 78 #include "llvm/ADT/Statistic.h" 79 #include "llvm/Analysis/AliasAnalysis.h" 80 #include "llvm/Analysis/CFG.h" 81 #include "llvm/Analysis/Loads.h" 82 #include "llvm/Analysis/MemoryBuiltins.h" 83 #include "llvm/Analysis/MemoryDependenceAnalysis.h" 84 #include "llvm/IR/Metadata.h" 85 #include "llvm/IR/PatternMatch.h" 86 #include "llvm/Support/Allocator.h" 87 #include "llvm/Support/CommandLine.h" 88 #include "llvm/Support/Debug.h" 89 #include "llvm/Target/TargetLibraryInfo.h" 90 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 91 #include "llvm/Transforms/Utils/SSAUpdater.h" 92 #include <vector> 93 using namespace llvm; 94 95 #define DEBUG_TYPE "mldst-motion" 96 97 //===----------------------------------------------------------------------===// 98 // MergedLoadStoreMotion Pass 99 //===----------------------------------------------------------------------===// 100 static cl::opt<bool> 101 EnableMLSM("mlsm", cl::desc("Enable motion of merged load and store"), 102 cl::init(true)); 103 104 namespace { 105 class MergedLoadStoreMotion : public FunctionPass { 106 AliasAnalysis *AA; 107 MemoryDependenceAnalysis *MD; 108 109 public: 110 static char ID; // Pass identification, replacement for typeid 111 explicit MergedLoadStoreMotion(void) : FunctionPass(ID), MD(nullptr) { 112 initializeMergedLoadStoreMotionPass(*PassRegistry::getPassRegistry()); 113 } 114 115 bool runOnFunction(Function &F) override; 116 117 private: 118 // This transformation requires dominator postdominator info 119 void getAnalysisUsage(AnalysisUsage &AU) const override { 120 AU.addRequired<TargetLibraryInfo>(); 121 AU.addRequired<MemoryDependenceAnalysis>(); 122 AU.addRequired<AliasAnalysis>(); 123 AU.addPreserved<AliasAnalysis>(); 124 } 125 126 // Helper routines 127 128 /// 129 /// \brief Remove instruction from parent and update memory dependence 130 /// analysis. 131 /// 132 void removeInstruction(Instruction *Inst); 133 BasicBlock *getDiamondTail(BasicBlock *BB); 134 bool isDiamondHead(BasicBlock *BB); 135 // Routines for hoisting loads 136 bool isLoadHoistBarrier(Instruction *Inst); 137 LoadInst *canHoistFromBlock(BasicBlock *BB, LoadInst *LI); 138 void hoistInstruction(BasicBlock *BB, Instruction *HoistCand, 139 Instruction *ElseInst); 140 bool isSafeToHoist(Instruction *I) const; 141 bool hoistLoad(BasicBlock *BB, LoadInst *HoistCand, LoadInst *ElseInst); 142 bool mergeLoads(BasicBlock *BB); 143 // Routines for sinking stores 144 StoreInst *canSinkFromBlock(BasicBlock *BB, StoreInst *SI); 145 PHINode *getPHIOperand(BasicBlock *BB, StoreInst *S0, StoreInst *S1); 146 bool isStoreSinkBarrier(Instruction *Inst); 147 bool sinkStore(BasicBlock *BB, StoreInst *SinkCand, StoreInst *ElseInst); 148 bool mergeStores(BasicBlock *BB); 149 // The mergeLoad/Store algorithms could have Size0 * Size1 complexity, 150 // where Size0 and Size1 are the #instructions on the two sides of 151 // the diamond. The constant chosen here is arbitrary. Compiler Time 152 // Control is enforced by the check Size0 * Size1 < MagicCompileTimeControl. 153 const int MagicCompileTimeControl = 250; 154 }; 155 156 char MergedLoadStoreMotion::ID = 0; 157 } 158 159 /// 160 /// \brief createMergedLoadStoreMotionPass - The public interface to this file. 161 /// 162 FunctionPass *llvm::createMergedLoadStoreMotionPass() { 163 return new MergedLoadStoreMotion(); 164 } 165 166 INITIALIZE_PASS_BEGIN(MergedLoadStoreMotion, "mldst-motion", 167 "MergedLoadStoreMotion", false, false) 168 INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis) 169 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) 170 INITIALIZE_AG_DEPENDENCY(AliasAnalysis) 171 INITIALIZE_PASS_END(MergedLoadStoreMotion, "mldst-motion", 172 "MergedLoadStoreMotion", false, false) 173 174 /// 175 /// \brief Remove instruction from parent and update memory dependence analysis. 176 /// 177 void MergedLoadStoreMotion::removeInstruction(Instruction *Inst) { 178 // Notify the memory dependence analysis. 179 if (MD) { 180 MD->removeInstruction(Inst); 181 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) 182 MD->invalidateCachedPointerInfo(LI->getPointerOperand()); 183 if (Inst->getType()->getScalarType()->isPointerTy()) { 184 MD->invalidateCachedPointerInfo(Inst); 185 } 186 } 187 Inst->eraseFromParent(); 188 } 189 190 /// 191 /// \brief Return tail block of a diamond. 192 /// 193 BasicBlock *MergedLoadStoreMotion::getDiamondTail(BasicBlock *BB) { 194 assert(isDiamondHead(BB) && "Basic block is not head of a diamond"); 195 BranchInst *BI = (BranchInst *)(BB->getTerminator()); 196 BasicBlock *Succ0 = BI->getSuccessor(0); 197 BasicBlock *Tail = Succ0->getTerminator()->getSuccessor(0); 198 return Tail; 199 } 200 201 /// 202 /// \brief True when BB is the head of a diamond (hammock) 203 /// 204 bool MergedLoadStoreMotion::isDiamondHead(BasicBlock *BB) { 205 if (!BB) 206 return false; 207 if (!isa<BranchInst>(BB->getTerminator())) 208 return false; 209 if (BB->getTerminator()->getNumSuccessors() != 2) 210 return false; 211 212 BranchInst *BI = (BranchInst *)(BB->getTerminator()); 213 BasicBlock *Succ0 = BI->getSuccessor(0); 214 BasicBlock *Succ1 = BI->getSuccessor(1); 215 216 if (!Succ0->getSinglePredecessor() || 217 Succ0->getTerminator()->getNumSuccessors() != 1) 218 return false; 219 if (!Succ1->getSinglePredecessor() || 220 Succ1->getTerminator()->getNumSuccessors() != 1) 221 return false; 222 223 BasicBlock *Tail = Succ0->getTerminator()->getSuccessor(0); 224 // Ignore triangles. 225 if (Succ1->getTerminator()->getSuccessor(0) != Tail) 226 return false; 227 return true; 228 } 229 230 /// 231 /// \brief True when instruction is a hoist barrier for a load 232 /// 233 /// Whenever an instruction could possibly modify the value 234 /// being loaded or protect against the load from happening 235 /// it is considered a hoist barrier. 236 /// 237 bool MergedLoadStoreMotion::isLoadHoistBarrier(Instruction *Inst) { 238 // FIXME: A call with no side effects should not be a barrier. 239 // Aren't all such calls covered by mayHaveSideEffects() below? 240 // Then this check can be removed. 241 if (isa<CallInst>(Inst)) 242 return true; 243 if (isa<TerminatorInst>(Inst)) 244 return true; 245 // Note: mayHaveSideEffects covers all instructions that could 246 // trigger a change to state. Eg. in-flight stores have to be executed 247 // before ordered loads or fences, calls could invoke functions that store 248 // data to memory etc. 249 if (Inst->mayHaveSideEffects()) { 250 return true; 251 } 252 DEBUG(dbgs() << "No Hoist Barrier\n"); 253 return false; 254 } 255 256 /// 257 /// \brief Decide if a load can be hoisted 258 /// 259 /// When there is a load in \p BB to the same address as \p LI 260 /// and it can be hoisted from \p BB, return that load. 261 /// Otherwise return Null. 262 /// 263 LoadInst *MergedLoadStoreMotion::canHoistFromBlock(BasicBlock *BB, 264 LoadInst *LI) { 265 LoadInst *I = nullptr; 266 assert(isa<LoadInst>(LI)); 267 if (LI->isUsedOutsideOfBlock(LI->getParent())) 268 return nullptr; 269 270 for (BasicBlock::iterator BBI = BB->begin(), BBE = BB->end(); BBI != BBE; 271 ++BBI) { 272 Instruction *Inst = BBI; 273 274 // Only merge and hoist loads when their result in used only in BB 275 if (isLoadHoistBarrier(Inst)) 276 break; 277 if (!isa<LoadInst>(Inst)) 278 continue; 279 if (Inst->isUsedOutsideOfBlock(Inst->getParent())) 280 continue; 281 282 AliasAnalysis::Location LocLI = AA->getLocation(LI); 283 AliasAnalysis::Location LocInst = AA->getLocation((LoadInst *)Inst); 284 if (AA->isMustAlias(LocLI, LocInst) && LI->getType() == Inst->getType()) { 285 I = (LoadInst *)Inst; 286 break; 287 } 288 } 289 return I; 290 } 291 292 /// 293 /// \brief Merge two equivalent instructions \p HoistCand and \p ElseInst into 294 /// \p BB 295 /// 296 /// BB is the head of a diamond 297 /// 298 void MergedLoadStoreMotion::hoistInstruction(BasicBlock *BB, 299 Instruction *HoistCand, 300 Instruction *ElseInst) { 301 DEBUG(dbgs() << " Hoist Instruction into BB \n"; BB->dump(); 302 dbgs() << "Instruction Left\n"; HoistCand->dump(); dbgs() << "\n"; 303 dbgs() << "Instruction Right\n"; ElseInst->dump(); dbgs() << "\n"); 304 // Hoist the instruction. 305 assert(HoistCand->getParent() != BB); 306 307 // Intersect optional metadata. 308 HoistCand->intersectOptionalDataWith(ElseInst); 309 HoistCand->dropUnknownMetadata(); 310 311 // Prepend point for instruction insert 312 Instruction *HoistPt = BB->getTerminator(); 313 314 // Merged instruction 315 Instruction *HoistedInst = HoistCand->clone(); 316 317 // Notify AA of the new value. 318 if (isa<LoadInst>(HoistCand)) 319 AA->copyValue(HoistCand, HoistedInst); 320 321 // Hoist instruction. 322 HoistedInst->insertBefore(HoistPt); 323 324 HoistCand->replaceAllUsesWith(HoistedInst); 325 removeInstruction(HoistCand); 326 // Replace the else block instruction. 327 ElseInst->replaceAllUsesWith(HoistedInst); 328 removeInstruction(ElseInst); 329 } 330 331 /// 332 /// \brief Return true if no operand of \p I is defined in I's parent block 333 /// 334 bool MergedLoadStoreMotion::isSafeToHoist(Instruction *I) const { 335 BasicBlock *Parent = I->getParent(); 336 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { 337 Instruction *Instr = dyn_cast<Instruction>(I->getOperand(i)); 338 if (Instr && Instr->getParent() == Parent) 339 return false; 340 } 341 return true; 342 } 343 344 /// 345 /// \brief Merge two equivalent loads and GEPs and hoist into diamond head 346 /// 347 bool MergedLoadStoreMotion::hoistLoad(BasicBlock *BB, LoadInst *L0, 348 LoadInst *L1) { 349 // Only one definition? 350 Instruction *A0 = dyn_cast<Instruction>(L0->getPointerOperand()); 351 Instruction *A1 = dyn_cast<Instruction>(L1->getPointerOperand()); 352 if (A0 && A1 && A0->isIdenticalTo(A1) && isSafeToHoist(A0) && 353 A0->hasOneUse() && (A0->getParent() == L0->getParent()) && 354 A1->hasOneUse() && (A1->getParent() == L1->getParent()) && 355 isa<GetElementPtrInst>(A0)) { 356 DEBUG(dbgs() << "Hoist Instruction into BB \n"; BB->dump(); 357 dbgs() << "Instruction Left\n"; L0->dump(); dbgs() << "\n"; 358 dbgs() << "Instruction Right\n"; L1->dump(); dbgs() << "\n"); 359 hoistInstruction(BB, A0, A1); 360 hoistInstruction(BB, L0, L1); 361 return true; 362 } else 363 return false; 364 } 365 366 /// 367 /// \brief Try to hoist two loads to same address into diamond header 368 /// 369 /// Starting from a diamond head block, iterate over the instructions in one 370 /// successor block and try to match a load in the second successor. 371 /// 372 bool MergedLoadStoreMotion::mergeLoads(BasicBlock *BB) { 373 bool MergedLoads = false; 374 assert(isDiamondHead(BB)); 375 BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator()); 376 BasicBlock *Succ0 = BI->getSuccessor(0); 377 BasicBlock *Succ1 = BI->getSuccessor(1); 378 // #Instructions in Succ1 for Compile Time Control 379 int Size1 = Succ1->size(); 380 int NLoads = 0; 381 for (BasicBlock::iterator BBI = Succ0->begin(), BBE = Succ0->end(); 382 BBI != BBE;) { 383 384 Instruction *I = BBI; 385 ++BBI; 386 if (isLoadHoistBarrier(I)) 387 break; 388 389 // Only move non-simple (atomic, volatile) loads. 390 if (!isa<LoadInst>(I)) 391 continue; 392 393 LoadInst *L0 = (LoadInst *)I; 394 if (!L0->isSimple()) 395 continue; 396 397 ++NLoads; 398 if (NLoads * Size1 >= MagicCompileTimeControl) 399 break; 400 if (LoadInst *L1 = canHoistFromBlock(Succ1, L0)) { 401 bool Res = hoistLoad(BB, L0, L1); 402 MergedLoads |= Res; 403 // Don't attempt to hoist above loads that had not been hoisted. 404 if (!Res) 405 break; 406 } 407 } 408 return MergedLoads; 409 } 410 411 /// 412 /// \brief True when instruction is sink barrier for a store 413 /// 414 bool MergedLoadStoreMotion::isStoreSinkBarrier(Instruction *Inst) { 415 if (isa<CallInst>(Inst)) 416 return true; 417 if (isa<TerminatorInst>(Inst) && !isa<BranchInst>(Inst)) 418 return true; 419 // Note: mayHaveSideEffects covers all instructions that could 420 // trigger a change to state. Eg. in-flight stores have to be executed 421 // before ordered loads or fences, calls could invoke functions that store 422 // data to memory etc. 423 if (!isa<StoreInst>(Inst) && Inst->mayHaveSideEffects()) { 424 return true; 425 } 426 DEBUG(dbgs() << "No Sink Barrier\n"); 427 return false; 428 } 429 430 /// 431 /// \brief Check if \p BB contains a store to the same address as \p SI 432 /// 433 /// \return The store in \p when it is safe to sink. Otherwise return Null. 434 /// 435 StoreInst *MergedLoadStoreMotion::canSinkFromBlock(BasicBlock *BB, 436 StoreInst *SI) { 437 StoreInst *I = 0; 438 DEBUG(dbgs() << "can Sink? : "; SI->dump(); dbgs() << "\n"); 439 for (BasicBlock::reverse_iterator RBI = BB->rbegin(), RBE = BB->rend(); 440 RBI != RBE; ++RBI) { 441 Instruction *Inst = &*RBI; 442 443 // Only move loads if they are used in the block. 444 if (isStoreSinkBarrier(Inst)) 445 break; 446 if (isa<StoreInst>(Inst)) { 447 AliasAnalysis::Location LocSI = AA->getLocation(SI); 448 AliasAnalysis::Location LocInst = AA->getLocation((StoreInst *)Inst); 449 if (AA->isMustAlias(LocSI, LocInst)) { 450 I = (StoreInst *)Inst; 451 break; 452 } 453 } 454 } 455 return I; 456 } 457 458 /// 459 /// \brief Create a PHI node in BB for the operands of S0 and S1 460 /// 461 PHINode *MergedLoadStoreMotion::getPHIOperand(BasicBlock *BB, StoreInst *S0, 462 StoreInst *S1) { 463 // Create a phi if the values mismatch. 464 PHINode *NewPN = 0; 465 Value *Opd1 = S0->getValueOperand(); 466 Value *Opd2 = S1->getValueOperand(); 467 if (Opd1 != Opd2) { 468 NewPN = PHINode::Create(Opd1->getType(), 2, Opd2->getName() + ".sink", 469 BB->begin()); 470 NewPN->addIncoming(Opd1, S0->getParent()); 471 NewPN->addIncoming(Opd2, S1->getParent()); 472 if (NewPN->getType()->getScalarType()->isPointerTy()) { 473 // Notify AA of the new value. 474 AA->copyValue(Opd1, NewPN); 475 AA->copyValue(Opd2, NewPN); 476 // AA needs to be informed when a PHI-use of the pointer value is added 477 for (unsigned I = 0, E = NewPN->getNumIncomingValues(); I != E; ++I) { 478 unsigned J = PHINode::getOperandNumForIncomingValue(I); 479 AA->addEscapingUse(NewPN->getOperandUse(J)); 480 } 481 if (MD) 482 MD->invalidateCachedPointerInfo(NewPN); 483 } 484 } 485 return NewPN; 486 } 487 488 /// 489 /// \brief Merge two stores to same address and sink into \p BB 490 /// 491 /// Also sinks GEP instruction computing the store address 492 /// 493 bool MergedLoadStoreMotion::sinkStore(BasicBlock *BB, StoreInst *S0, 494 StoreInst *S1) { 495 // Only one definition? 496 Instruction *A0 = dyn_cast<Instruction>(S0->getPointerOperand()); 497 Instruction *A1 = dyn_cast<Instruction>(S1->getPointerOperand()); 498 if (A0 && A1 && A0->isIdenticalTo(A1) && A0->hasOneUse() && 499 (A0->getParent() == S0->getParent()) && A1->hasOneUse() && 500 (A1->getParent() == S1->getParent()) && isa<GetElementPtrInst>(A0)) { 501 DEBUG(dbgs() << "Sink Instruction into BB \n"; BB->dump(); 502 dbgs() << "Instruction Left\n"; S0->dump(); dbgs() << "\n"; 503 dbgs() << "Instruction Right\n"; S1->dump(); dbgs() << "\n"); 504 // Hoist the instruction. 505 BasicBlock::iterator InsertPt = BB->getFirstInsertionPt(); 506 // Intersect optional metadata. 507 S0->intersectOptionalDataWith(S1); 508 S0->dropUnknownMetadata(); 509 510 // Create the new store to be inserted at the join point. 511 StoreInst *SNew = (StoreInst *)(S0->clone()); 512 Instruction *ANew = A0->clone(); 513 AA->copyValue(S0, SNew); 514 SNew->insertBefore(InsertPt); 515 ANew->insertBefore(SNew); 516 517 assert(S0->getParent() == A0->getParent()); 518 assert(S1->getParent() == A1->getParent()); 519 520 PHINode *NewPN = getPHIOperand(BB, S0, S1); 521 // New PHI operand? Use it. 522 if (NewPN) 523 SNew->setOperand(0, NewPN); 524 removeInstruction(S0); 525 removeInstruction(S1); 526 A0->replaceAllUsesWith(ANew); 527 removeInstruction(A0); 528 A1->replaceAllUsesWith(ANew); 529 removeInstruction(A1); 530 return true; 531 } 532 return false; 533 } 534 535 /// 536 /// \brief True when two stores are equivalent and can sink into the footer 537 /// 538 /// Starting from a diamond tail block, iterate over the instructions in one 539 /// predecessor block and try to match a store in the second predecessor. 540 /// 541 bool MergedLoadStoreMotion::mergeStores(BasicBlock *T) { 542 543 bool MergedStores = false; 544 assert(T && "Footer of a diamond cannot be empty"); 545 546 pred_iterator PI = pred_begin(T), E = pred_end(T); 547 assert(PI != E); 548 BasicBlock *Pred0 = *PI; 549 ++PI; 550 BasicBlock *Pred1 = *PI; 551 ++PI; 552 // tail block of a diamond/hammock? 553 if (Pred0 == Pred1) 554 return false; // No. 555 if (PI != E) 556 return false; // No. More than 2 predecessors. 557 558 // #Instructions in Succ1 for Compile Time Control 559 int Size1 = Pred1->size(); 560 int NStores = 0; 561 562 for (BasicBlock::reverse_iterator RBI = Pred0->rbegin(), RBE = Pred0->rend(); 563 RBI != RBE;) { 564 565 Instruction *I = &*RBI; 566 ++RBI; 567 if (isStoreSinkBarrier(I)) 568 break; 569 // Sink move non-simple (atomic, volatile) stores 570 if (!isa<StoreInst>(I)) 571 continue; 572 StoreInst *S0 = (StoreInst *)I; 573 if (!S0->isSimple()) 574 continue; 575 576 ++NStores; 577 if (NStores * Size1 >= MagicCompileTimeControl) 578 break; 579 if (StoreInst *S1 = canSinkFromBlock(Pred1, S0)) { 580 bool Res = sinkStore(T, S0, S1); 581 MergedStores |= Res; 582 // Don't attempt to sink below stores that had to stick around 583 // But after removal of a store and some of its feeding 584 // instruction search again from the beginning since the iterator 585 // is likely stale at this point. 586 if (!Res) 587 break; 588 else { 589 RBI = Pred0->rbegin(); 590 RBE = Pred0->rend(); 591 DEBUG(dbgs() << "Search again\n"; Instruction *I = &*RBI; I->dump()); 592 } 593 } 594 } 595 return MergedStores; 596 } 597 /// 598 /// \brief Run the transformation for each function 599 /// 600 bool MergedLoadStoreMotion::runOnFunction(Function &F) { 601 MD = &getAnalysis<MemoryDependenceAnalysis>(); 602 AA = &getAnalysis<AliasAnalysis>(); 603 604 bool Changed = false; 605 if (!EnableMLSM) 606 return false; 607 DEBUG(dbgs() << "Instruction Merger\n"); 608 609 // Merge unconditional branches, allowing PRE to catch more 610 // optimization opportunities. 611 for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) { 612 BasicBlock *BB = FI++; 613 614 // Hoist equivalent loads and sink stores 615 // outside diamonds when possible 616 // Run outside core GVN 617 if (isDiamondHead(BB)) { 618 Changed |= mergeLoads(BB); 619 Changed |= mergeStores(getDiamondTail(BB)); 620 } 621 } 622 return Changed; 623 } 624