MemoryDependenceAnalysis.cpp revision 9ff5a23186f8761d9e5b4b5adf6fae9ce7d63860
1//===- MemoryDependenceAnalysis.cpp - Mem Deps Implementation --*- C++ -*-===// 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 an analysis that determines, for a given memory 11// operation, what preceding memory operations it depends on. It builds on 12// alias analysis information, and tries to provide a lazy, caching interface to 13// a common kind of alias information query. 14// 15//===----------------------------------------------------------------------===// 16 17#define DEBUG_TYPE "memdep" 18#include "llvm/Analysis/MemoryDependenceAnalysis.h" 19#include "llvm/Instructions.h" 20#include "llvm/IntrinsicInst.h" 21#include "llvm/Function.h" 22#include "llvm/Analysis/AliasAnalysis.h" 23#include "llvm/Analysis/Dominators.h" 24#include "llvm/Analysis/InstructionSimplify.h" 25#include "llvm/Analysis/MemoryBuiltins.h" 26#include "llvm/ADT/Statistic.h" 27#include "llvm/ADT/STLExtras.h" 28#include "llvm/Support/PredIteratorCache.h" 29#include "llvm/Support/Debug.h" 30using namespace llvm; 31 32STATISTIC(NumCacheNonLocal, "Number of fully cached non-local responses"); 33STATISTIC(NumCacheDirtyNonLocal, "Number of dirty cached non-local responses"); 34STATISTIC(NumUncacheNonLocal, "Number of uncached non-local responses"); 35 36STATISTIC(NumCacheNonLocalPtr, 37 "Number of fully cached non-local ptr responses"); 38STATISTIC(NumCacheDirtyNonLocalPtr, 39 "Number of cached, but dirty, non-local ptr responses"); 40STATISTIC(NumUncacheNonLocalPtr, 41 "Number of uncached non-local ptr responses"); 42STATISTIC(NumCacheCompleteNonLocalPtr, 43 "Number of block queries that were completely cached"); 44 45char MemoryDependenceAnalysis::ID = 0; 46 47// Register this pass... 48static RegisterPass<MemoryDependenceAnalysis> X("memdep", 49 "Memory Dependence Analysis", false, true); 50 51MemoryDependenceAnalysis::MemoryDependenceAnalysis() 52: FunctionPass(&ID), PredCache(0) { 53} 54MemoryDependenceAnalysis::~MemoryDependenceAnalysis() { 55} 56 57/// Clean up memory in between runs 58void MemoryDependenceAnalysis::releaseMemory() { 59 LocalDeps.clear(); 60 NonLocalDeps.clear(); 61 NonLocalPointerDeps.clear(); 62 ReverseLocalDeps.clear(); 63 ReverseNonLocalDeps.clear(); 64 ReverseNonLocalPtrDeps.clear(); 65 PredCache->clear(); 66} 67 68 69 70/// getAnalysisUsage - Does not modify anything. It uses Alias Analysis. 71/// 72void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { 73 AU.setPreservesAll(); 74 AU.addRequiredTransitive<AliasAnalysis>(); 75} 76 77bool MemoryDependenceAnalysis::runOnFunction(Function &) { 78 AA = &getAnalysis<AliasAnalysis>(); 79 if (PredCache == 0) 80 PredCache.reset(new PredIteratorCache()); 81 return false; 82} 83 84/// RemoveFromReverseMap - This is a helper function that removes Val from 85/// 'Inst's set in ReverseMap. If the set becomes empty, remove Inst's entry. 86template <typename KeyTy> 87static void RemoveFromReverseMap(DenseMap<Instruction*, 88 SmallPtrSet<KeyTy, 4> > &ReverseMap, 89 Instruction *Inst, KeyTy Val) { 90 typename DenseMap<Instruction*, SmallPtrSet<KeyTy, 4> >::iterator 91 InstIt = ReverseMap.find(Inst); 92 assert(InstIt != ReverseMap.end() && "Reverse map out of sync?"); 93 bool Found = InstIt->second.erase(Val); 94 assert(Found && "Invalid reverse map!"); Found=Found; 95 if (InstIt->second.empty()) 96 ReverseMap.erase(InstIt); 97} 98 99 100/// getCallSiteDependencyFrom - Private helper for finding the local 101/// dependencies of a call site. 102MemDepResult MemoryDependenceAnalysis:: 103getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall, 104 BasicBlock::iterator ScanIt, BasicBlock *BB) { 105 // Walk backwards through the block, looking for dependencies 106 while (ScanIt != BB->begin()) { 107 Instruction *Inst = --ScanIt; 108 109 // If this inst is a memory op, get the pointer it accessed 110 Value *Pointer = 0; 111 uint64_t PointerSize = 0; 112 if (StoreInst *S = dyn_cast<StoreInst>(Inst)) { 113 Pointer = S->getPointerOperand(); 114 PointerSize = AA->getTypeStoreSize(S->getOperand(0)->getType()); 115 } else if (VAArgInst *V = dyn_cast<VAArgInst>(Inst)) { 116 Pointer = V->getOperand(0); 117 PointerSize = AA->getTypeStoreSize(V->getType()); 118 } else if (isFreeCall(Inst)) { 119 Pointer = Inst->getOperand(1); 120 // calls to free() erase the entire structure 121 PointerSize = ~0ULL; 122 } else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) { 123 // Debug intrinsics don't cause dependences. 124 if (isa<DbgInfoIntrinsic>(Inst)) continue; 125 CallSite InstCS = CallSite::get(Inst); 126 // If these two calls do not interfere, look past it. 127 switch (AA->getModRefInfo(CS, InstCS)) { 128 case AliasAnalysis::NoModRef: 129 // If the two calls don't interact (e.g. InstCS is readnone) keep 130 // scanning. 131 continue; 132 case AliasAnalysis::Ref: 133 // If the two calls read the same memory locations and CS is a readonly 134 // function, then we have two cases: 1) the calls may not interfere with 135 // each other at all. 2) the calls may produce the same value. In case 136 // #1 we want to ignore the values, in case #2, we want to return Inst 137 // as a Def dependence. This allows us to CSE in cases like: 138 // X = strlen(P); 139 // memchr(...); 140 // Y = strlen(P); // Y = X 141 if (isReadOnlyCall) { 142 if (CS.getCalledFunction() != 0 && 143 CS.getCalledFunction() == InstCS.getCalledFunction()) 144 return MemDepResult::getDef(Inst); 145 // Ignore unrelated read/read call dependences. 146 continue; 147 } 148 // FALL THROUGH 149 default: 150 return MemDepResult::getClobber(Inst); 151 } 152 } else { 153 // Non-memory instruction. 154 continue; 155 } 156 157 if (AA->getModRefInfo(CS, Pointer, PointerSize) != AliasAnalysis::NoModRef) 158 return MemDepResult::getClobber(Inst); 159 } 160 161 // No dependence found. If this is the entry block of the function, it is a 162 // clobber, otherwise it is non-local. 163 if (BB != &BB->getParent()->getEntryBlock()) 164 return MemDepResult::getNonLocal(); 165 return MemDepResult::getClobber(ScanIt); 166} 167 168/// getPointerDependencyFrom - Return the instruction on which a memory 169/// location depends. If isLoad is true, this routine ignore may-aliases with 170/// read-only operations. 171MemDepResult MemoryDependenceAnalysis:: 172getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad, 173 BasicBlock::iterator ScanIt, BasicBlock *BB) { 174 175 Value *InvariantTag = 0; 176 177 // Walk backwards through the basic block, looking for dependencies. 178 while (ScanIt != BB->begin()) { 179 Instruction *Inst = --ScanIt; 180 181 // If we're in an invariant region, no dependencies can be found before 182 // we pass an invariant-begin marker. 183 if (InvariantTag == Inst) { 184 InvariantTag = 0; 185 continue; 186 } 187 188 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 189 // Debug intrinsics don't cause dependences. 190 if (isa<DbgInfoIntrinsic>(Inst)) continue; 191 192 // If we pass an invariant-end marker, then we've just entered an 193 // invariant region and can start ignoring dependencies. 194 if (II->getIntrinsicID() == Intrinsic::invariant_end) { 195 // FIXME: This only considers queries directly on the invariant-tagged 196 // pointer, not on query pointers that are indexed off of them. It'd 197 // be nice to handle that at some point. 198 AliasAnalysis::AliasResult R = 199 AA->alias(II->getOperand(3), ~0ULL, MemPtr, ~0ULL); 200 if (R == AliasAnalysis::MustAlias) { 201 InvariantTag = II->getOperand(1); 202 continue; 203 } 204 205 // If we reach a lifetime begin or end marker, then the query ends here 206 // because the value is undefined. 207 } else if (II->getIntrinsicID() == Intrinsic::lifetime_start) { 208 // FIXME: This only considers queries directly on the invariant-tagged 209 // pointer, not on query pointers that are indexed off of them. It'd 210 // be nice to handle that at some point. 211 AliasAnalysis::AliasResult R = 212 AA->alias(II->getOperand(2), ~0ULL, MemPtr, ~0ULL); 213 if (R == AliasAnalysis::MustAlias) 214 return MemDepResult::getDef(II); 215 } 216 } 217 218 // If we're querying on a load and we're in an invariant region, we're done 219 // at this point. Nothing a load depends on can live in an invariant region. 220 if (isLoad && InvariantTag) continue; 221 222 // Values depend on loads if the pointers are must aliased. This means that 223 // a load depends on another must aliased load from the same value. 224 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) { 225 Value *Pointer = LI->getPointerOperand(); 226 uint64_t PointerSize = AA->getTypeStoreSize(LI->getType()); 227 228 // If we found a pointer, check if it could be the same as our pointer. 229 AliasAnalysis::AliasResult R = 230 AA->alias(Pointer, PointerSize, MemPtr, MemSize); 231 if (R == AliasAnalysis::NoAlias) 232 continue; 233 234 // May-alias loads don't depend on each other without a dependence. 235 if (isLoad && R == AliasAnalysis::MayAlias) 236 continue; 237 // Stores depend on may and must aliased loads, loads depend on must-alias 238 // loads. 239 return MemDepResult::getDef(Inst); 240 } 241 242 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 243 // There can't be stores to the value we care about inside an 244 // invariant region. 245 if (InvariantTag) continue; 246 247 // If alias analysis can tell that this store is guaranteed to not modify 248 // the query pointer, ignore it. Use getModRefInfo to handle cases where 249 // the query pointer points to constant memory etc. 250 if (AA->getModRefInfo(SI, MemPtr, MemSize) == AliasAnalysis::NoModRef) 251 continue; 252 253 // Ok, this store might clobber the query pointer. Check to see if it is 254 // a must alias: in this case, we want to return this as a def. 255 Value *Pointer = SI->getPointerOperand(); 256 uint64_t PointerSize = AA->getTypeStoreSize(SI->getOperand(0)->getType()); 257 258 // If we found a pointer, check if it could be the same as our pointer. 259 AliasAnalysis::AliasResult R = 260 AA->alias(Pointer, PointerSize, MemPtr, MemSize); 261 262 if (R == AliasAnalysis::NoAlias) 263 continue; 264 if (R == AliasAnalysis::MayAlias) 265 return MemDepResult::getClobber(Inst); 266 return MemDepResult::getDef(Inst); 267 } 268 269 // If this is an allocation, and if we know that the accessed pointer is to 270 // the allocation, return Def. This means that there is no dependence and 271 // the access can be optimized based on that. For example, a load could 272 // turn into undef. 273 // Note: Only determine this to be a malloc if Inst is the malloc call, not 274 // a subsequent bitcast of the malloc call result. There can be stores to 275 // the malloced memory between the malloc call and its bitcast uses, and we 276 // need to continue scanning until the malloc call. 277 if (isa<AllocaInst>(Inst) || extractMallocCall(Inst)) { 278 Value *AccessPtr = MemPtr->getUnderlyingObject(); 279 280 if (AccessPtr == Inst || 281 AA->alias(Inst, 1, AccessPtr, 1) == AliasAnalysis::MustAlias) 282 return MemDepResult::getDef(Inst); 283 continue; 284 } 285 286 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer. 287 switch (AA->getModRefInfo(Inst, MemPtr, MemSize)) { 288 case AliasAnalysis::NoModRef: 289 // If the call has no effect on the queried pointer, just ignore it. 290 continue; 291 case AliasAnalysis::Mod: 292 // If we're in an invariant region, we can ignore calls that ONLY 293 // modify the pointer. 294 if (InvariantTag) continue; 295 return MemDepResult::getClobber(Inst); 296 case AliasAnalysis::Ref: 297 // If the call is known to never store to the pointer, and if this is a 298 // load query, we can safely ignore it (scan past it). 299 if (isLoad) 300 continue; 301 default: 302 // Otherwise, there is a potential dependence. Return a clobber. 303 return MemDepResult::getClobber(Inst); 304 } 305 } 306 307 // No dependence found. If this is the entry block of the function, it is a 308 // clobber, otherwise it is non-local. 309 if (BB != &BB->getParent()->getEntryBlock()) 310 return MemDepResult::getNonLocal(); 311 return MemDepResult::getClobber(ScanIt); 312} 313 314/// getDependency - Return the instruction on which a memory operation 315/// depends. 316MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) { 317 Instruction *ScanPos = QueryInst; 318 319 // Check for a cached result 320 MemDepResult &LocalCache = LocalDeps[QueryInst]; 321 322 // If the cached entry is non-dirty, just return it. Note that this depends 323 // on MemDepResult's default constructing to 'dirty'. 324 if (!LocalCache.isDirty()) 325 return LocalCache; 326 327 // Otherwise, if we have a dirty entry, we know we can start the scan at that 328 // instruction, which may save us some work. 329 if (Instruction *Inst = LocalCache.getInst()) { 330 ScanPos = Inst; 331 332 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst); 333 } 334 335 BasicBlock *QueryParent = QueryInst->getParent(); 336 337 Value *MemPtr = 0; 338 uint64_t MemSize = 0; 339 340 // Do the scan. 341 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) { 342 // No dependence found. If this is the entry block of the function, it is a 343 // clobber, otherwise it is non-local. 344 if (QueryParent != &QueryParent->getParent()->getEntryBlock()) 345 LocalCache = MemDepResult::getNonLocal(); 346 else 347 LocalCache = MemDepResult::getClobber(QueryInst); 348 } else if (StoreInst *SI = dyn_cast<StoreInst>(QueryInst)) { 349 // If this is a volatile store, don't mess around with it. Just return the 350 // previous instruction as a clobber. 351 if (SI->isVolatile()) 352 LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos)); 353 else { 354 MemPtr = SI->getPointerOperand(); 355 MemSize = AA->getTypeStoreSize(SI->getOperand(0)->getType()); 356 } 357 } else if (LoadInst *LI = dyn_cast<LoadInst>(QueryInst)) { 358 // If this is a volatile load, don't mess around with it. Just return the 359 // previous instruction as a clobber. 360 if (LI->isVolatile()) 361 LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos)); 362 else { 363 MemPtr = LI->getPointerOperand(); 364 MemSize = AA->getTypeStoreSize(LI->getType()); 365 } 366 } else if (isFreeCall(QueryInst)) { 367 MemPtr = QueryInst->getOperand(1); 368 // calls to free() erase the entire structure, not just a field. 369 MemSize = ~0UL; 370 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) { 371 int IntrinsicID = 0; // Intrinsic IDs start at 1. 372 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst)) 373 IntrinsicID = II->getIntrinsicID(); 374 375 switch (IntrinsicID) { 376 case Intrinsic::lifetime_start: 377 case Intrinsic::lifetime_end: 378 case Intrinsic::invariant_start: 379 MemPtr = QueryInst->getOperand(2); 380 MemSize = cast<ConstantInt>(QueryInst->getOperand(1))->getZExtValue(); 381 break; 382 case Intrinsic::invariant_end: 383 MemPtr = QueryInst->getOperand(3); 384 MemSize = cast<ConstantInt>(QueryInst->getOperand(2))->getZExtValue(); 385 break; 386 default: 387 CallSite QueryCS = CallSite::get(QueryInst); 388 bool isReadOnly = AA->onlyReadsMemory(QueryCS); 389 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos, 390 QueryParent); 391 } 392 } else { 393 // Non-memory instruction. 394 LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos)); 395 } 396 397 // If we need to do a pointer scan, make it happen. 398 if (MemPtr) { 399 bool isLoad = !QueryInst->mayWriteToMemory(); 400 if (IntrinsicInst *II = dyn_cast<MemoryUseIntrinsic>(QueryInst)) { 401 isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_end; 402 } 403 LocalCache = getPointerDependencyFrom(MemPtr, MemSize, isLoad, ScanPos, 404 QueryParent); 405 } 406 407 // Remember the result! 408 if (Instruction *I = LocalCache.getInst()) 409 ReverseLocalDeps[I].insert(QueryInst); 410 411 return LocalCache; 412} 413 414#ifndef NDEBUG 415/// AssertSorted - This method is used when -debug is specified to verify that 416/// cache arrays are properly kept sorted. 417static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache, 418 int Count = -1) { 419 if (Count == -1) Count = Cache.size(); 420 if (Count == 0) return; 421 422 for (unsigned i = 1; i != unsigned(Count); ++i) 423 assert(Cache[i-1] <= Cache[i] && "Cache isn't sorted!"); 424} 425#endif 426 427/// getNonLocalCallDependency - Perform a full dependency query for the 428/// specified call, returning the set of blocks that the value is 429/// potentially live across. The returned set of results will include a 430/// "NonLocal" result for all blocks where the value is live across. 431/// 432/// This method assumes the instruction returns a "NonLocal" dependency 433/// within its own block. 434/// 435/// This returns a reference to an internal data structure that may be 436/// invalidated on the next non-local query or when an instruction is 437/// removed. Clients must copy this data if they want it around longer than 438/// that. 439const MemoryDependenceAnalysis::NonLocalDepInfo & 440MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) { 441 assert(getDependency(QueryCS.getInstruction()).isNonLocal() && 442 "getNonLocalCallDependency should only be used on calls with non-local deps!"); 443 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()]; 444 NonLocalDepInfo &Cache = CacheP.first; 445 446 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In 447 /// the cached case, this can happen due to instructions being deleted etc. In 448 /// the uncached case, this starts out as the set of predecessors we care 449 /// about. 450 SmallVector<BasicBlock*, 32> DirtyBlocks; 451 452 if (!Cache.empty()) { 453 // Okay, we have a cache entry. If we know it is not dirty, just return it 454 // with no computation. 455 if (!CacheP.second) { 456 NumCacheNonLocal++; 457 return Cache; 458 } 459 460 // If we already have a partially computed set of results, scan them to 461 // determine what is dirty, seeding our initial DirtyBlocks worklist. 462 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end(); 463 I != E; ++I) 464 if (I->second.isDirty()) 465 DirtyBlocks.push_back(I->first); 466 467 // Sort the cache so that we can do fast binary search lookups below. 468 std::sort(Cache.begin(), Cache.end()); 469 470 ++NumCacheDirtyNonLocal; 471 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: " 472 // << Cache.size() << " cached: " << *QueryInst; 473 } else { 474 // Seed DirtyBlocks with each of the preds of QueryInst's block. 475 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent(); 476 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI) 477 DirtyBlocks.push_back(*PI); 478 NumUncacheNonLocal++; 479 } 480 481 // isReadonlyCall - If this is a read-only call, we can be more aggressive. 482 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS); 483 484 SmallPtrSet<BasicBlock*, 64> Visited; 485 486 unsigned NumSortedEntries = Cache.size(); 487 DEBUG(AssertSorted(Cache)); 488 489 // Iterate while we still have blocks to update. 490 while (!DirtyBlocks.empty()) { 491 BasicBlock *DirtyBB = DirtyBlocks.back(); 492 DirtyBlocks.pop_back(); 493 494 // Already processed this block? 495 if (!Visited.insert(DirtyBB)) 496 continue; 497 498 // Do a binary search to see if we already have an entry for this block in 499 // the cache set. If so, find it. 500 DEBUG(AssertSorted(Cache, NumSortedEntries)); 501 NonLocalDepInfo::iterator Entry = 502 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries, 503 std::make_pair(DirtyBB, MemDepResult())); 504 if (Entry != Cache.begin() && prior(Entry)->first == DirtyBB) 505 --Entry; 506 507 MemDepResult *ExistingResult = 0; 508 if (Entry != Cache.begin()+NumSortedEntries && 509 Entry->first == DirtyBB) { 510 // If we already have an entry, and if it isn't already dirty, the block 511 // is done. 512 if (!Entry->second.isDirty()) 513 continue; 514 515 // Otherwise, remember this slot so we can update the value. 516 ExistingResult = &Entry->second; 517 } 518 519 // If the dirty entry has a pointer, start scanning from it so we don't have 520 // to rescan the entire block. 521 BasicBlock::iterator ScanPos = DirtyBB->end(); 522 if (ExistingResult) { 523 if (Instruction *Inst = ExistingResult->getInst()) { 524 ScanPos = Inst; 525 // We're removing QueryInst's use of Inst. 526 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, 527 QueryCS.getInstruction()); 528 } 529 } 530 531 // Find out if this block has a local dependency for QueryInst. 532 MemDepResult Dep; 533 534 if (ScanPos != DirtyBB->begin()) { 535 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB); 536 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) { 537 // No dependence found. If this is the entry block of the function, it is 538 // a clobber, otherwise it is non-local. 539 Dep = MemDepResult::getNonLocal(); 540 } else { 541 Dep = MemDepResult::getClobber(ScanPos); 542 } 543 544 // If we had a dirty entry for the block, update it. Otherwise, just add 545 // a new entry. 546 if (ExistingResult) 547 *ExistingResult = Dep; 548 else 549 Cache.push_back(std::make_pair(DirtyBB, Dep)); 550 551 // If the block has a dependency (i.e. it isn't completely transparent to 552 // the value), remember the association! 553 if (!Dep.isNonLocal()) { 554 // Keep the ReverseNonLocalDeps map up to date so we can efficiently 555 // update this when we remove instructions. 556 if (Instruction *Inst = Dep.getInst()) 557 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction()); 558 } else { 559 560 // If the block *is* completely transparent to the load, we need to check 561 // the predecessors of this block. Add them to our worklist. 562 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI) 563 DirtyBlocks.push_back(*PI); 564 } 565 } 566 567 return Cache; 568} 569 570/// getNonLocalPointerDependency - Perform a full dependency query for an 571/// access to the specified (non-volatile) memory location, returning the 572/// set of instructions that either define or clobber the value. 573/// 574/// This method assumes the pointer has a "NonLocal" dependency within its 575/// own block. 576/// 577void MemoryDependenceAnalysis:: 578getNonLocalPointerDependency(Value *Pointer, bool isLoad, BasicBlock *FromBB, 579 SmallVectorImpl<NonLocalDepEntry> &Result) { 580 assert(isa<PointerType>(Pointer->getType()) && 581 "Can't get pointer deps of a non-pointer!"); 582 Result.clear(); 583 584 // We know that the pointer value is live into FromBB find the def/clobbers 585 // from presecessors. 586 const Type *EltTy = cast<PointerType>(Pointer->getType())->getElementType(); 587 uint64_t PointeeSize = AA->getTypeStoreSize(EltTy); 588 589 // This is the set of blocks we've inspected, and the pointer we consider in 590 // each block. Because of critical edges, we currently bail out if querying 591 // a block with multiple different pointers. This can happen during PHI 592 // translation. 593 DenseMap<BasicBlock*, Value*> Visited; 594 if (!getNonLocalPointerDepFromBB(Pointer, PointeeSize, isLoad, FromBB, 595 Result, Visited, true)) 596 return; 597 Result.clear(); 598 Result.push_back(std::make_pair(FromBB, 599 MemDepResult::getClobber(FromBB->begin()))); 600} 601 602/// GetNonLocalInfoForBlock - Compute the memdep value for BB with 603/// Pointer/PointeeSize using either cached information in Cache or by doing a 604/// lookup (which may use dirty cache info if available). If we do a lookup, 605/// add the result to the cache. 606MemDepResult MemoryDependenceAnalysis:: 607GetNonLocalInfoForBlock(Value *Pointer, uint64_t PointeeSize, 608 bool isLoad, BasicBlock *BB, 609 NonLocalDepInfo *Cache, unsigned NumSortedEntries) { 610 611 // Do a binary search to see if we already have an entry for this block in 612 // the cache set. If so, find it. 613 NonLocalDepInfo::iterator Entry = 614 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries, 615 std::make_pair(BB, MemDepResult())); 616 if (Entry != Cache->begin() && prior(Entry)->first == BB) 617 --Entry; 618 619 MemDepResult *ExistingResult = 0; 620 if (Entry != Cache->begin()+NumSortedEntries && Entry->first == BB) 621 ExistingResult = &Entry->second; 622 623 // If we have a cached entry, and it is non-dirty, use it as the value for 624 // this dependency. 625 if (ExistingResult && !ExistingResult->isDirty()) { 626 ++NumCacheNonLocalPtr; 627 return *ExistingResult; 628 } 629 630 // Otherwise, we have to scan for the value. If we have a dirty cache 631 // entry, start scanning from its position, otherwise we scan from the end 632 // of the block. 633 BasicBlock::iterator ScanPos = BB->end(); 634 if (ExistingResult && ExistingResult->getInst()) { 635 assert(ExistingResult->getInst()->getParent() == BB && 636 "Instruction invalidated?"); 637 ++NumCacheDirtyNonLocalPtr; 638 ScanPos = ExistingResult->getInst(); 639 640 // Eliminating the dirty entry from 'Cache', so update the reverse info. 641 ValueIsLoadPair CacheKey(Pointer, isLoad); 642 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey); 643 } else { 644 ++NumUncacheNonLocalPtr; 645 } 646 647 // Scan the block for the dependency. 648 MemDepResult Dep = getPointerDependencyFrom(Pointer, PointeeSize, isLoad, 649 ScanPos, BB); 650 651 // If we had a dirty entry for the block, update it. Otherwise, just add 652 // a new entry. 653 if (ExistingResult) 654 *ExistingResult = Dep; 655 else 656 Cache->push_back(std::make_pair(BB, Dep)); 657 658 // If the block has a dependency (i.e. it isn't completely transparent to 659 // the value), remember the reverse association because we just added it 660 // to Cache! 661 if (Dep.isNonLocal()) 662 return Dep; 663 664 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently 665 // update MemDep when we remove instructions. 666 Instruction *Inst = Dep.getInst(); 667 assert(Inst && "Didn't depend on anything?"); 668 ValueIsLoadPair CacheKey(Pointer, isLoad); 669 ReverseNonLocalPtrDeps[Inst].insert(CacheKey); 670 return Dep; 671} 672 673/// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain 674/// number of elements in the array that are already properly ordered. This is 675/// optimized for the case when only a few entries are added. 676static void 677SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache, 678 unsigned NumSortedEntries) { 679 switch (Cache.size() - NumSortedEntries) { 680 case 0: 681 // done, no new entries. 682 break; 683 case 2: { 684 // Two new entries, insert the last one into place. 685 MemoryDependenceAnalysis::NonLocalDepEntry Val = Cache.back(); 686 Cache.pop_back(); 687 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry = 688 std::upper_bound(Cache.begin(), Cache.end()-1, Val); 689 Cache.insert(Entry, Val); 690 // FALL THROUGH. 691 } 692 case 1: 693 // One new entry, Just insert the new value at the appropriate position. 694 if (Cache.size() != 1) { 695 MemoryDependenceAnalysis::NonLocalDepEntry Val = Cache.back(); 696 Cache.pop_back(); 697 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry = 698 std::upper_bound(Cache.begin(), Cache.end(), Val); 699 Cache.insert(Entry, Val); 700 } 701 break; 702 default: 703 // Added many values, do a full scale sort. 704 std::sort(Cache.begin(), Cache.end()); 705 break; 706 } 707} 708 709/// isPHITranslatable - Return true if the specified computation is derived from 710/// a PHI node in the current block and if it is simple enough for us to handle. 711static bool isPHITranslatable(Instruction *Inst) { 712 if (isa<PHINode>(Inst)) 713 return true; 714 715 // We can handle bitcast of a PHI, but the PHI needs to be in the same block 716 // as the bitcast. 717 if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) { 718 Instruction *OpI = dyn_cast<Instruction>(BC->getOperand(0)); 719 if (OpI == 0 || OpI->getParent() != Inst->getParent()) 720 return true; 721 return isPHITranslatable(OpI); 722 } 723 724 // We can translate a GEP if all of its operands defined in this block are phi 725 // translatable. 726 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) { 727 for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) { 728 Instruction *OpI = dyn_cast<Instruction>(GEP->getOperand(i)); 729 if (OpI == 0 || OpI->getParent() != Inst->getParent()) 730 continue; 731 732 if (!isPHITranslatable(OpI)) 733 return false; 734 } 735 return true; 736 } 737 738 if (Inst->getOpcode() == Instruction::Add && 739 isa<ConstantInt>(Inst->getOperand(1))) { 740 Instruction *OpI = dyn_cast<Instruction>(Inst->getOperand(0)); 741 if (OpI == 0 || OpI->getParent() != Inst->getParent()) 742 return true; 743 return isPHITranslatable(OpI); 744 } 745 746 // cerr << "MEMDEP: Could not PHI translate: " << *Pointer; 747 // if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst)) 748 // cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0); 749 750 return false; 751} 752 753/// GetPHITranslatedValue - Given a computation that satisfied the 754/// isPHITranslatable predicate, see if we can translate the computation into 755/// the specified predecessor block. If so, return that value. 756Value *MemoryDependenceAnalysis:: 757GetPHITranslatedValue(Value *InVal, BasicBlock *CurBB, BasicBlock *Pred, 758 const TargetData *TD) const { 759 // If the input value is not an instruction, or if it is not defined in CurBB, 760 // then we don't need to phi translate it. 761 Instruction *Inst = dyn_cast<Instruction>(InVal); 762 if (Inst == 0 || Inst->getParent() != CurBB) 763 return InVal; 764 765 if (PHINode *PN = dyn_cast<PHINode>(Inst)) 766 return PN->getIncomingValueForBlock(Pred); 767 768 // Handle bitcast of PHI. 769 if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) { 770 // PHI translate the input operand. 771 Value *PHIIn = GetPHITranslatedValue(BC->getOperand(0), CurBB, Pred, TD); 772 if (PHIIn == 0) return 0; 773 774 // Constants are trivial to phi translate. 775 if (Constant *C = dyn_cast<Constant>(PHIIn)) 776 return ConstantExpr::getBitCast(C, BC->getType()); 777 778 // Otherwise we have to see if a bitcasted version of the incoming pointer 779 // is available. If so, we can use it, otherwise we have to fail. 780 for (Value::use_iterator UI = PHIIn->use_begin(), E = PHIIn->use_end(); 781 UI != E; ++UI) { 782 if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI)) 783 if (BCI->getType() == BC->getType()) 784 return BCI; 785 } 786 return 0; 787 } 788 789 // Handle getelementptr with at least one PHI translatable operand. 790 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) { 791 SmallVector<Value*, 8> GEPOps; 792 BasicBlock *CurBB = GEP->getParent(); 793 for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) { 794 Value *GEPOp = GEP->getOperand(i); 795 // No PHI translation is needed of operands whose values are live in to 796 // the predecessor block. 797 if (!isa<Instruction>(GEPOp) || 798 cast<Instruction>(GEPOp)->getParent() != CurBB) { 799 GEPOps.push_back(GEPOp); 800 continue; 801 } 802 803 // If the operand is a phi node, do phi translation. 804 Value *InOp = GetPHITranslatedValue(GEPOp, CurBB, Pred, TD); 805 if (InOp == 0) return 0; 806 807 GEPOps.push_back(InOp); 808 } 809 810 // Simplify the GEP to handle 'gep x, 0' -> x etc. 811 if (Value *V = SimplifyGEPInst(&GEPOps[0], GEPOps.size(), TD)) 812 return V; 813 814 // Scan to see if we have this GEP available. 815 Value *APHIOp = GEPOps[0]; 816 for (Value::use_iterator UI = APHIOp->use_begin(), E = APHIOp->use_end(); 817 UI != E; ++UI) { 818 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) 819 if (GEPI->getType() == GEP->getType() && 820 GEPI->getNumOperands() == GEPOps.size() && 821 GEPI->getParent()->getParent() == CurBB->getParent()) { 822 bool Mismatch = false; 823 for (unsigned i = 0, e = GEPOps.size(); i != e; ++i) 824 if (GEPI->getOperand(i) != GEPOps[i]) { 825 Mismatch = true; 826 break; 827 } 828 if (!Mismatch) 829 return GEPI; 830 } 831 } 832 return 0; 833 } 834 835 // Handle add with a constant RHS. 836 if (Inst->getOpcode() == Instruction::Add && 837 isa<ConstantInt>(Inst->getOperand(1))) { 838 // PHI translate the LHS. 839 Value *LHS; 840 Constant *RHS = cast<ConstantInt>(Inst->getOperand(1)); 841 Instruction *OpI = dyn_cast<Instruction>(Inst->getOperand(0)); 842 bool isNSW = cast<BinaryOperator>(Inst)->hasNoSignedWrap(); 843 bool isNUW = cast<BinaryOperator>(Inst)->hasNoUnsignedWrap(); 844 845 if (OpI == 0 || OpI->getParent() != Inst->getParent()) 846 LHS = Inst->getOperand(0); 847 else { 848 LHS = GetPHITranslatedValue(Inst->getOperand(0), CurBB, Pred, TD); 849 if (LHS == 0) 850 return 0; 851 } 852 853 // If the PHI translated LHS is an add of a constant, fold the immediates. 854 if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(LHS)) 855 if (BOp->getOpcode() == Instruction::Add) 856 if (ConstantInt *CI = dyn_cast<ConstantInt>(BOp->getOperand(1))) { 857 LHS = BOp->getOperand(0); 858 RHS = ConstantExpr::getAdd(RHS, CI); 859 isNSW = isNUW = false; 860 } 861 862 // See if the add simplifies away. 863 if (Value *Res = SimplifyAddInst(LHS, RHS, isNSW, isNUW, TD)) 864 return Res; 865 866 // Otherwise, see if we have this add available somewhere. 867 for (Value::use_iterator UI = LHS->use_begin(), E = LHS->use_end(); 868 UI != E; ++UI) { 869 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*UI)) 870 if (BO->getOperand(0) == LHS && BO->getOperand(1) == RHS && 871 BO->getParent()->getParent() == CurBB->getParent()) 872 return BO; 873 } 874 875 return 0; 876 } 877 878 return 0; 879} 880 881/// GetAvailablePHITranslatePointer - Return the value computed by 882/// PHITranslatePointer if it dominates PredBB, otherwise return null. 883Value *MemoryDependenceAnalysis:: 884GetAvailablePHITranslatedValue(Value *V, 885 BasicBlock *CurBB, BasicBlock *PredBB, 886 const TargetData *TD, 887 const DominatorTree &DT) const { 888 // See if PHI translation succeeds. 889 V = GetPHITranslatedValue(V, CurBB, PredBB, TD); 890 if (V == 0) return 0; 891 892 // Make sure the value is live in the predecessor. 893 if (Instruction *Inst = dyn_cast_or_null<Instruction>(V)) 894 if (!DT.dominates(Inst->getParent(), PredBB)) 895 return 0; 896 return V; 897} 898 899 900/// InsertPHITranslatedPointer - Insert a computation of the PHI translated 901/// version of 'V' for the edge PredBB->CurBB into the end of the PredBB 902/// block. All newly created instructions are added to the NewInsts list. 903/// 904Value *MemoryDependenceAnalysis:: 905InsertPHITranslatedPointer(Value *InVal, BasicBlock *CurBB, 906 BasicBlock *PredBB, const TargetData *TD, 907 const DominatorTree &DT, 908 SmallVectorImpl<Instruction*> &NewInsts) const { 909 // See if we have a version of this value already available and dominating 910 // PredBB. If so, there is no need to insert a new copy. 911 if (Value *Res = GetAvailablePHITranslatedValue(InVal, CurBB, PredBB, TD, DT)) 912 return Res; 913 914 // If we don't have an available version of this value, it must be an 915 // instruction. 916 Instruction *Inst = cast<Instruction>(InVal); 917 918 // Handle bitcast of PHI translatable value. 919 if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) { 920 Value *OpVal = InsertPHITranslatedPointer(BC->getOperand(0), 921 CurBB, PredBB, TD, DT, NewInsts); 922 if (OpVal == 0) return 0; 923 924 // Otherwise insert a bitcast at the end of PredBB. 925 BitCastInst *New = new BitCastInst(OpVal, InVal->getType(), 926 InVal->getName()+".phi.trans.insert", 927 PredBB->getTerminator()); 928 NewInsts.push_back(New); 929 return New; 930 } 931 932 // Handle getelementptr with at least one PHI operand. 933 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) { 934 SmallVector<Value*, 8> GEPOps; 935 BasicBlock *CurBB = GEP->getParent(); 936 for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) { 937 Value *OpVal = InsertPHITranslatedPointer(GEP->getOperand(i), 938 CurBB, PredBB, TD, DT, NewInsts); 939 if (OpVal == 0) return 0; 940 GEPOps.push_back(OpVal); 941 } 942 943 GetElementPtrInst *Result = 944 GetElementPtrInst::Create(GEPOps[0], GEPOps.begin()+1, GEPOps.end(), 945 InVal->getName()+".phi.trans.insert", 946 PredBB->getTerminator()); 947 Result->setIsInBounds(GEP->isInBounds()); 948 NewInsts.push_back(Result); 949 return Result; 950 } 951 952#if 0 953 // FIXME: This code works, but it is unclear that we actually want to insert 954 // a big chain of computation in order to make a value available in a block. 955 // This needs to be evaluated carefully to consider its cost trade offs. 956 957 // Handle add with a constant RHS. 958 if (Inst->getOpcode() == Instruction::Add && 959 isa<ConstantInt>(Inst->getOperand(1))) { 960 // PHI translate the LHS. 961 Value *OpVal = InsertPHITranslatedPointer(Inst->getOperand(0), 962 CurBB, PredBB, TD, DT, NewInsts); 963 if (OpVal == 0) return 0; 964 965 BinaryOperator *Res = BinaryOperator::CreateAdd(OpVal, Inst->getOperand(1), 966 InVal->getName()+".phi.trans.insert", 967 PredBB->getTerminator()); 968 Res->setHasNoSignedWrap(cast<BinaryOperator>(Inst)->hasNoSignedWrap()); 969 Res->setHasNoUnsignedWrap(cast<BinaryOperator>(Inst)->hasNoUnsignedWrap()); 970 NewInsts.push_back(Res); 971 return Res; 972 } 973#endif 974 975 return 0; 976} 977 978/// getNonLocalPointerDepFromBB - Perform a dependency query based on 979/// pointer/pointeesize starting at the end of StartBB. Add any clobber/def 980/// results to the results vector and keep track of which blocks are visited in 981/// 'Visited'. 982/// 983/// This has special behavior for the first block queries (when SkipFirstBlock 984/// is true). In this special case, it ignores the contents of the specified 985/// block and starts returning dependence info for its predecessors. 986/// 987/// This function returns false on success, or true to indicate that it could 988/// not compute dependence information for some reason. This should be treated 989/// as a clobber dependence on the first instruction in the predecessor block. 990bool MemoryDependenceAnalysis:: 991getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize, 992 bool isLoad, BasicBlock *StartBB, 993 SmallVectorImpl<NonLocalDepEntry> &Result, 994 DenseMap<BasicBlock*, Value*> &Visited, 995 bool SkipFirstBlock) { 996 997 // Look up the cached info for Pointer. 998 ValueIsLoadPair CacheKey(Pointer, isLoad); 999 1000 std::pair<BBSkipFirstBlockPair, NonLocalDepInfo> *CacheInfo = 1001 &NonLocalPointerDeps[CacheKey]; 1002 NonLocalDepInfo *Cache = &CacheInfo->second; 1003 1004 // If we have valid cached information for exactly the block we are 1005 // investigating, just return it with no recomputation. 1006 if (CacheInfo->first == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) { 1007 // We have a fully cached result for this query then we can just return the 1008 // cached results and populate the visited set. However, we have to verify 1009 // that we don't already have conflicting results for these blocks. Check 1010 // to ensure that if a block in the results set is in the visited set that 1011 // it was for the same pointer query. 1012 if (!Visited.empty()) { 1013 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end(); 1014 I != E; ++I) { 1015 DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->first); 1016 if (VI == Visited.end() || VI->second == Pointer) continue; 1017 1018 // We have a pointer mismatch in a block. Just return clobber, saying 1019 // that something was clobbered in this result. We could also do a 1020 // non-fully cached query, but there is little point in doing this. 1021 return true; 1022 } 1023 } 1024 1025 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end(); 1026 I != E; ++I) { 1027 Visited.insert(std::make_pair(I->first, Pointer)); 1028 if (!I->second.isNonLocal()) 1029 Result.push_back(*I); 1030 } 1031 ++NumCacheCompleteNonLocalPtr; 1032 return false; 1033 } 1034 1035 // Otherwise, either this is a new block, a block with an invalid cache 1036 // pointer or one that we're about to invalidate by putting more info into it 1037 // than its valid cache info. If empty, the result will be valid cache info, 1038 // otherwise it isn't. 1039 if (Cache->empty()) 1040 CacheInfo->first = BBSkipFirstBlockPair(StartBB, SkipFirstBlock); 1041 else 1042 CacheInfo->first = BBSkipFirstBlockPair(); 1043 1044 SmallVector<BasicBlock*, 32> Worklist; 1045 Worklist.push_back(StartBB); 1046 1047 // Keep track of the entries that we know are sorted. Previously cached 1048 // entries will all be sorted. The entries we add we only sort on demand (we 1049 // don't insert every element into its sorted position). We know that we 1050 // won't get any reuse from currently inserted values, because we don't 1051 // revisit blocks after we insert info for them. 1052 unsigned NumSortedEntries = Cache->size(); 1053 DEBUG(AssertSorted(*Cache)); 1054 1055 while (!Worklist.empty()) { 1056 BasicBlock *BB = Worklist.pop_back_val(); 1057 1058 // Skip the first block if we have it. 1059 if (!SkipFirstBlock) { 1060 // Analyze the dependency of *Pointer in FromBB. See if we already have 1061 // been here. 1062 assert(Visited.count(BB) && "Should check 'visited' before adding to WL"); 1063 1064 // Get the dependency info for Pointer in BB. If we have cached 1065 // information, we will use it, otherwise we compute it. 1066 DEBUG(AssertSorted(*Cache, NumSortedEntries)); 1067 MemDepResult Dep = GetNonLocalInfoForBlock(Pointer, PointeeSize, isLoad, 1068 BB, Cache, NumSortedEntries); 1069 1070 // If we got a Def or Clobber, add this to the list of results. 1071 if (!Dep.isNonLocal()) { 1072 Result.push_back(NonLocalDepEntry(BB, Dep)); 1073 continue; 1074 } 1075 } 1076 1077 // If 'Pointer' is an instruction defined in this block, then we need to do 1078 // phi translation to change it into a value live in the predecessor block. 1079 // If phi translation fails, then we can't continue dependence analysis. 1080 Instruction *PtrInst = dyn_cast<Instruction>(Pointer); 1081 bool NeedsPHITranslation = PtrInst && PtrInst->getParent() == BB; 1082 1083 // If no PHI translation is needed, just add all the predecessors of this 1084 // block to scan them as well. 1085 if (!NeedsPHITranslation) { 1086 SkipFirstBlock = false; 1087 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { 1088 // Verify that we haven't looked at this block yet. 1089 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool> 1090 InsertRes = Visited.insert(std::make_pair(*PI, Pointer)); 1091 if (InsertRes.second) { 1092 // First time we've looked at *PI. 1093 Worklist.push_back(*PI); 1094 continue; 1095 } 1096 1097 // If we have seen this block before, but it was with a different 1098 // pointer then we have a phi translation failure and we have to treat 1099 // this as a clobber. 1100 if (InsertRes.first->second != Pointer) 1101 goto PredTranslationFailure; 1102 } 1103 continue; 1104 } 1105 1106 // If we do need to do phi translation, then there are a bunch of different 1107 // cases, because we have to find a Value* live in the predecessor block. We 1108 // know that PtrInst is defined in this block at least. 1109 1110 // We may have added values to the cache list before this PHI translation. 1111 // If so, we haven't done anything to ensure that the cache remains sorted. 1112 // Sort it now (if needed) so that recursive invocations of 1113 // getNonLocalPointerDepFromBB and other routines that could reuse the cache 1114 // value will only see properly sorted cache arrays. 1115 if (Cache && NumSortedEntries != Cache->size()) { 1116 SortNonLocalDepInfoCache(*Cache, NumSortedEntries); 1117 NumSortedEntries = Cache->size(); 1118 } 1119 1120 // If this is a computation derived from a PHI node, use the suitably 1121 // translated incoming values for each pred as the phi translated version. 1122 if (!isPHITranslatable(PtrInst)) 1123 goto PredTranslationFailure; 1124 1125 Cache = 0; 1126 1127 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { 1128 BasicBlock *Pred = *PI; 1129 // Get the PHI translated pointer in this predecessor. This can fail and 1130 // return null if not translatable. 1131 Value *PredPtr = GetPHITranslatedValue(PtrInst, BB, Pred, TD); 1132 1133 // Check to see if we have already visited this pred block with another 1134 // pointer. If so, we can't do this lookup. This failure can occur 1135 // with PHI translation when a critical edge exists and the PHI node in 1136 // the successor translates to a pointer value different than the 1137 // pointer the block was first analyzed with. 1138 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool> 1139 InsertRes = Visited.insert(std::make_pair(Pred, PredPtr)); 1140 1141 if (!InsertRes.second) { 1142 // If the predecessor was visited with PredPtr, then we already did 1143 // the analysis and can ignore it. 1144 if (InsertRes.first->second == PredPtr) 1145 continue; 1146 1147 // Otherwise, the block was previously analyzed with a different 1148 // pointer. We can't represent the result of this case, so we just 1149 // treat this as a phi translation failure. 1150 goto PredTranslationFailure; 1151 } 1152 1153 // If PHI translation was unable to find an available pointer in this 1154 // predecessor, then we have to assume that the pointer is clobbered in 1155 // that predecessor. We can still do PRE of the load, which would insert 1156 // a computation of the pointer in this predecessor. 1157 if (PredPtr == 0) { 1158 // Add the entry to the Result list. 1159 NonLocalDepEntry Entry(Pred, 1160 MemDepResult::getClobber(Pred->getTerminator())); 1161 Result.push_back(Entry); 1162 1163 // Add it to the cache for this CacheKey so that subsequent queries get 1164 // this result. 1165 Cache = &NonLocalPointerDeps[CacheKey].second; 1166 MemoryDependenceAnalysis::NonLocalDepInfo::iterator It = 1167 std::upper_bound(Cache->begin(), Cache->end(), Entry); 1168 1169 if (It != Cache->begin() && prior(It)->first == Pred) 1170 --It; 1171 1172 if (It == Cache->end() || It->first != Pred) { 1173 Cache->insert(It, Entry); 1174 // Add it to the reverse map. 1175 ReverseNonLocalPtrDeps[Pred->getTerminator()].insert(CacheKey); 1176 } else if (!It->second.isDirty()) { 1177 // noop 1178 } else if (It->second.getInst() == Pred->getTerminator()) { 1179 // Same instruction, clear the dirty marker. 1180 It->second = Entry.second; 1181 } else if (It->second.getInst() == 0) { 1182 // Dirty, with no instruction, just add this. 1183 It->second = Entry.second; 1184 ReverseNonLocalPtrDeps[Pred->getTerminator()].insert(CacheKey); 1185 } else { 1186 // Otherwise, dirty with a different instruction. 1187 RemoveFromReverseMap(ReverseNonLocalPtrDeps, It->second.getInst(), 1188 CacheKey); 1189 It->second = Entry.second; 1190 ReverseNonLocalPtrDeps[Pred->getTerminator()].insert(CacheKey); 1191 } 1192 Cache = 0; 1193 continue; 1194 } 1195 1196 // FIXME: it is entirely possible that PHI translating will end up with 1197 // the same value. Consider PHI translating something like: 1198 // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need* 1199 // to recurse here, pedantically speaking. 1200 1201 // If we have a problem phi translating, fall through to the code below 1202 // to handle the failure condition. 1203 if (getNonLocalPointerDepFromBB(PredPtr, PointeeSize, isLoad, Pred, 1204 Result, Visited)) 1205 goto PredTranslationFailure; 1206 } 1207 1208 // Refresh the CacheInfo/Cache pointer so that it isn't invalidated. 1209 CacheInfo = &NonLocalPointerDeps[CacheKey]; 1210 Cache = &CacheInfo->second; 1211 NumSortedEntries = Cache->size(); 1212 1213 // Since we did phi translation, the "Cache" set won't contain all of the 1214 // results for the query. This is ok (we can still use it to accelerate 1215 // specific block queries) but we can't do the fastpath "return all 1216 // results from the set" Clear out the indicator for this. 1217 CacheInfo->first = BBSkipFirstBlockPair(); 1218 SkipFirstBlock = false; 1219 continue; 1220 1221 PredTranslationFailure: 1222 1223 if (Cache == 0) { 1224 // Refresh the CacheInfo/Cache pointer if it got invalidated. 1225 CacheInfo = &NonLocalPointerDeps[CacheKey]; 1226 Cache = &CacheInfo->second; 1227 NumSortedEntries = Cache->size(); 1228 } 1229 1230 // Since we did phi translation, the "Cache" set won't contain all of the 1231 // results for the query. This is ok (we can still use it to accelerate 1232 // specific block queries) but we can't do the fastpath "return all 1233 // results from the set" Clear out the indicator for this. 1234 CacheInfo->first = BBSkipFirstBlockPair(); 1235 1236 // If *nothing* works, mark the pointer as being clobbered by the first 1237 // instruction in this block. 1238 // 1239 // If this is the magic first block, return this as a clobber of the whole 1240 // incoming value. Since we can't phi translate to one of the predecessors, 1241 // we have to bail out. 1242 if (SkipFirstBlock) 1243 return true; 1244 1245 for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) { 1246 assert(I != Cache->rend() && "Didn't find current block??"); 1247 if (I->first != BB) 1248 continue; 1249 1250 assert(I->second.isNonLocal() && 1251 "Should only be here with transparent block"); 1252 I->second = MemDepResult::getClobber(BB->begin()); 1253 ReverseNonLocalPtrDeps[BB->begin()].insert(CacheKey); 1254 Result.push_back(*I); 1255 break; 1256 } 1257 } 1258 1259 // Okay, we're done now. If we added new values to the cache, re-sort it. 1260 SortNonLocalDepInfoCache(*Cache, NumSortedEntries); 1261 DEBUG(AssertSorted(*Cache)); 1262 return false; 1263} 1264 1265/// RemoveCachedNonLocalPointerDependencies - If P exists in 1266/// CachedNonLocalPointerInfo, remove it. 1267void MemoryDependenceAnalysis:: 1268RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) { 1269 CachedNonLocalPointerInfo::iterator It = 1270 NonLocalPointerDeps.find(P); 1271 if (It == NonLocalPointerDeps.end()) return; 1272 1273 // Remove all of the entries in the BB->val map. This involves removing 1274 // instructions from the reverse map. 1275 NonLocalDepInfo &PInfo = It->second.second; 1276 1277 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) { 1278 Instruction *Target = PInfo[i].second.getInst(); 1279 if (Target == 0) continue; // Ignore non-local dep results. 1280 assert(Target->getParent() == PInfo[i].first); 1281 1282 // Eliminating the dirty entry from 'Cache', so update the reverse info. 1283 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P); 1284 } 1285 1286 // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo). 1287 NonLocalPointerDeps.erase(It); 1288} 1289 1290 1291/// invalidateCachedPointerInfo - This method is used to invalidate cached 1292/// information about the specified pointer, because it may be too 1293/// conservative in memdep. This is an optional call that can be used when 1294/// the client detects an equivalence between the pointer and some other 1295/// value and replaces the other value with ptr. This can make Ptr available 1296/// in more places that cached info does not necessarily keep. 1297void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) { 1298 // If Ptr isn't really a pointer, just ignore it. 1299 if (!isa<PointerType>(Ptr->getType())) return; 1300 // Flush store info for the pointer. 1301 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false)); 1302 // Flush load info for the pointer. 1303 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true)); 1304} 1305 1306/// removeInstruction - Remove an instruction from the dependence analysis, 1307/// updating the dependence of instructions that previously depended on it. 1308/// This method attempts to keep the cache coherent using the reverse map. 1309void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) { 1310 // Walk through the Non-local dependencies, removing this one as the value 1311 // for any cached queries. 1312 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst); 1313 if (NLDI != NonLocalDeps.end()) { 1314 NonLocalDepInfo &BlockMap = NLDI->second.first; 1315 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end(); 1316 DI != DE; ++DI) 1317 if (Instruction *Inst = DI->second.getInst()) 1318 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst); 1319 NonLocalDeps.erase(NLDI); 1320 } 1321 1322 // If we have a cached local dependence query for this instruction, remove it. 1323 // 1324 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst); 1325 if (LocalDepEntry != LocalDeps.end()) { 1326 // Remove us from DepInst's reverse set now that the local dep info is gone. 1327 if (Instruction *Inst = LocalDepEntry->second.getInst()) 1328 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst); 1329 1330 // Remove this local dependency info. 1331 LocalDeps.erase(LocalDepEntry); 1332 } 1333 1334 // If we have any cached pointer dependencies on this instruction, remove 1335 // them. If the instruction has non-pointer type, then it can't be a pointer 1336 // base. 1337 1338 // Remove it from both the load info and the store info. The instruction 1339 // can't be in either of these maps if it is non-pointer. 1340 if (isa<PointerType>(RemInst->getType())) { 1341 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false)); 1342 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true)); 1343 } 1344 1345 // Loop over all of the things that depend on the instruction we're removing. 1346 // 1347 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd; 1348 1349 // If we find RemInst as a clobber or Def in any of the maps for other values, 1350 // we need to replace its entry with a dirty version of the instruction after 1351 // it. If RemInst is a terminator, we use a null dirty value. 1352 // 1353 // Using a dirty version of the instruction after RemInst saves having to scan 1354 // the entire block to get to this point. 1355 MemDepResult NewDirtyVal; 1356 if (!RemInst->isTerminator()) 1357 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst)); 1358 1359 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst); 1360 if (ReverseDepIt != ReverseLocalDeps.end()) { 1361 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second; 1362 // RemInst can't be the terminator if it has local stuff depending on it. 1363 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) && 1364 "Nothing can locally depend on a terminator"); 1365 1366 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(), 1367 E = ReverseDeps.end(); I != E; ++I) { 1368 Instruction *InstDependingOnRemInst = *I; 1369 assert(InstDependingOnRemInst != RemInst && 1370 "Already removed our local dep info"); 1371 1372 LocalDeps[InstDependingOnRemInst] = NewDirtyVal; 1373 1374 // Make sure to remember that new things depend on NewDepInst. 1375 assert(NewDirtyVal.getInst() && "There is no way something else can have " 1376 "a local dep on this if it is a terminator!"); 1377 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(), 1378 InstDependingOnRemInst)); 1379 } 1380 1381 ReverseLocalDeps.erase(ReverseDepIt); 1382 1383 // Add new reverse deps after scanning the set, to avoid invalidating the 1384 // 'ReverseDeps' reference. 1385 while (!ReverseDepsToAdd.empty()) { 1386 ReverseLocalDeps[ReverseDepsToAdd.back().first] 1387 .insert(ReverseDepsToAdd.back().second); 1388 ReverseDepsToAdd.pop_back(); 1389 } 1390 } 1391 1392 ReverseDepIt = ReverseNonLocalDeps.find(RemInst); 1393 if (ReverseDepIt != ReverseNonLocalDeps.end()) { 1394 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second; 1395 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end(); 1396 I != E; ++I) { 1397 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst"); 1398 1399 PerInstNLInfo &INLD = NonLocalDeps[*I]; 1400 // The information is now dirty! 1401 INLD.second = true; 1402 1403 for (NonLocalDepInfo::iterator DI = INLD.first.begin(), 1404 DE = INLD.first.end(); DI != DE; ++DI) { 1405 if (DI->second.getInst() != RemInst) continue; 1406 1407 // Convert to a dirty entry for the subsequent instruction. 1408 DI->second = NewDirtyVal; 1409 1410 if (Instruction *NextI = NewDirtyVal.getInst()) 1411 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I)); 1412 } 1413 } 1414 1415 ReverseNonLocalDeps.erase(ReverseDepIt); 1416 1417 // Add new reverse deps after scanning the set, to avoid invalidating 'Set' 1418 while (!ReverseDepsToAdd.empty()) { 1419 ReverseNonLocalDeps[ReverseDepsToAdd.back().first] 1420 .insert(ReverseDepsToAdd.back().second); 1421 ReverseDepsToAdd.pop_back(); 1422 } 1423 } 1424 1425 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a 1426 // value in the NonLocalPointerDeps info. 1427 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt = 1428 ReverseNonLocalPtrDeps.find(RemInst); 1429 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) { 1430 SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second; 1431 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd; 1432 1433 for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(), 1434 E = Set.end(); I != E; ++I) { 1435 ValueIsLoadPair P = *I; 1436 assert(P.getPointer() != RemInst && 1437 "Already removed NonLocalPointerDeps info for RemInst"); 1438 1439 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].second; 1440 1441 // The cache is not valid for any specific block anymore. 1442 NonLocalPointerDeps[P].first = BBSkipFirstBlockPair(); 1443 1444 // Update any entries for RemInst to use the instruction after it. 1445 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end(); 1446 DI != DE; ++DI) { 1447 if (DI->second.getInst() != RemInst) continue; 1448 1449 // Convert to a dirty entry for the subsequent instruction. 1450 DI->second = NewDirtyVal; 1451 1452 if (Instruction *NewDirtyInst = NewDirtyVal.getInst()) 1453 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P)); 1454 } 1455 1456 // Re-sort the NonLocalDepInfo. Changing the dirty entry to its 1457 // subsequent value may invalidate the sortedness. 1458 std::sort(NLPDI.begin(), NLPDI.end()); 1459 } 1460 1461 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt); 1462 1463 while (!ReversePtrDepsToAdd.empty()) { 1464 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first] 1465 .insert(ReversePtrDepsToAdd.back().second); 1466 ReversePtrDepsToAdd.pop_back(); 1467 } 1468 } 1469 1470 1471 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?"); 1472 AA->deleteValue(RemInst); 1473 DEBUG(verifyRemoved(RemInst)); 1474} 1475/// verifyRemoved - Verify that the specified instruction does not occur 1476/// in our internal data structures. 1477void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const { 1478 for (LocalDepMapType::const_iterator I = LocalDeps.begin(), 1479 E = LocalDeps.end(); I != E; ++I) { 1480 assert(I->first != D && "Inst occurs in data structures"); 1481 assert(I->second.getInst() != D && 1482 "Inst occurs in data structures"); 1483 } 1484 1485 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(), 1486 E = NonLocalPointerDeps.end(); I != E; ++I) { 1487 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key"); 1488 const NonLocalDepInfo &Val = I->second.second; 1489 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end(); 1490 II != E; ++II) 1491 assert(II->second.getInst() != D && "Inst occurs as NLPD value"); 1492 } 1493 1494 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(), 1495 E = NonLocalDeps.end(); I != E; ++I) { 1496 assert(I->first != D && "Inst occurs in data structures"); 1497 const PerInstNLInfo &INLD = I->second; 1498 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(), 1499 EE = INLD.first.end(); II != EE; ++II) 1500 assert(II->second.getInst() != D && "Inst occurs in data structures"); 1501 } 1502 1503 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(), 1504 E = ReverseLocalDeps.end(); I != E; ++I) { 1505 assert(I->first != D && "Inst occurs in data structures"); 1506 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(), 1507 EE = I->second.end(); II != EE; ++II) 1508 assert(*II != D && "Inst occurs in data structures"); 1509 } 1510 1511 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(), 1512 E = ReverseNonLocalDeps.end(); 1513 I != E; ++I) { 1514 assert(I->first != D && "Inst occurs in data structures"); 1515 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(), 1516 EE = I->second.end(); II != EE; ++II) 1517 assert(*II != D && "Inst occurs in data structures"); 1518 } 1519 1520 for (ReverseNonLocalPtrDepTy::const_iterator 1521 I = ReverseNonLocalPtrDeps.begin(), 1522 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) { 1523 assert(I->first != D && "Inst occurs in rev NLPD map"); 1524 1525 for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(), 1526 E = I->second.end(); II != E; ++II) 1527 assert(*II != ValueIsLoadPair(D, false) && 1528 *II != ValueIsLoadPair(D, true) && 1529 "Inst occurs in ReverseNonLocalPtrDeps map"); 1530 } 1531 1532} 1533