MemoryDependenceAnalysis.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338
1//===- MemoryDependenceAnalysis.cpp - Mem Deps Implementation -------------===// 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/ADT/STLExtras.h" 20#include "llvm/ADT/Statistic.h" 21#include "llvm/Analysis/AliasAnalysis.h" 22#include "llvm/Analysis/InstructionSimplify.h" 23#include "llvm/Analysis/MemoryBuiltins.h" 24#include "llvm/Analysis/PHITransAddr.h" 25#include "llvm/Analysis/ValueTracking.h" 26#include "llvm/IR/DataLayout.h" 27#include "llvm/IR/Dominators.h" 28#include "llvm/IR/Function.h" 29#include "llvm/IR/Instructions.h" 30#include "llvm/IR/IntrinsicInst.h" 31#include "llvm/IR/LLVMContext.h" 32#include "llvm/IR/PredIteratorCache.h" 33#include "llvm/Support/Debug.h" 34using namespace llvm; 35 36STATISTIC(NumCacheNonLocal, "Number of fully cached non-local responses"); 37STATISTIC(NumCacheDirtyNonLocal, "Number of dirty cached non-local responses"); 38STATISTIC(NumUncacheNonLocal, "Number of uncached non-local responses"); 39 40STATISTIC(NumCacheNonLocalPtr, 41 "Number of fully cached non-local ptr responses"); 42STATISTIC(NumCacheDirtyNonLocalPtr, 43 "Number of cached, but dirty, non-local ptr responses"); 44STATISTIC(NumUncacheNonLocalPtr, 45 "Number of uncached non-local ptr responses"); 46STATISTIC(NumCacheCompleteNonLocalPtr, 47 "Number of block queries that were completely cached"); 48 49// Limit for the number of instructions to scan in a block. 50static const int BlockScanLimit = 100; 51 52char MemoryDependenceAnalysis::ID = 0; 53 54// Register this pass... 55INITIALIZE_PASS_BEGIN(MemoryDependenceAnalysis, "memdep", 56 "Memory Dependence Analysis", false, true) 57INITIALIZE_AG_DEPENDENCY(AliasAnalysis) 58INITIALIZE_PASS_END(MemoryDependenceAnalysis, "memdep", 59 "Memory Dependence Analysis", false, true) 60 61MemoryDependenceAnalysis::MemoryDependenceAnalysis() 62 : FunctionPass(ID), PredCache() { 63 initializeMemoryDependenceAnalysisPass(*PassRegistry::getPassRegistry()); 64} 65MemoryDependenceAnalysis::~MemoryDependenceAnalysis() { 66} 67 68/// Clean up memory in between runs 69void MemoryDependenceAnalysis::releaseMemory() { 70 LocalDeps.clear(); 71 NonLocalDeps.clear(); 72 NonLocalPointerDeps.clear(); 73 ReverseLocalDeps.clear(); 74 ReverseNonLocalDeps.clear(); 75 ReverseNonLocalPtrDeps.clear(); 76 PredCache->clear(); 77} 78 79 80 81/// getAnalysisUsage - Does not modify anything. It uses Alias Analysis. 82/// 83void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { 84 AU.setPreservesAll(); 85 AU.addRequiredTransitive<AliasAnalysis>(); 86} 87 88bool MemoryDependenceAnalysis::runOnFunction(Function &) { 89 AA = &getAnalysis<AliasAnalysis>(); 90 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>(); 91 DL = DLP ? &DLP->getDataLayout() : 0; 92 DominatorTreeWrapperPass *DTWP = 93 getAnalysisIfAvailable<DominatorTreeWrapperPass>(); 94 DT = DTWP ? &DTWP->getDomTree() : 0; 95 if (!PredCache) 96 PredCache.reset(new PredIteratorCache()); 97 return false; 98} 99 100/// RemoveFromReverseMap - This is a helper function that removes Val from 101/// 'Inst's set in ReverseMap. If the set becomes empty, remove Inst's entry. 102template <typename KeyTy> 103static void RemoveFromReverseMap(DenseMap<Instruction*, 104 SmallPtrSet<KeyTy, 4> > &ReverseMap, 105 Instruction *Inst, KeyTy Val) { 106 typename DenseMap<Instruction*, SmallPtrSet<KeyTy, 4> >::iterator 107 InstIt = ReverseMap.find(Inst); 108 assert(InstIt != ReverseMap.end() && "Reverse map out of sync?"); 109 bool Found = InstIt->second.erase(Val); 110 assert(Found && "Invalid reverse map!"); (void)Found; 111 if (InstIt->second.empty()) 112 ReverseMap.erase(InstIt); 113} 114 115/// GetLocation - If the given instruction references a specific memory 116/// location, fill in Loc with the details, otherwise set Loc.Ptr to null. 117/// Return a ModRefInfo value describing the general behavior of the 118/// instruction. 119static 120AliasAnalysis::ModRefResult GetLocation(const Instruction *Inst, 121 AliasAnalysis::Location &Loc, 122 AliasAnalysis *AA) { 123 if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) { 124 if (LI->isUnordered()) { 125 Loc = AA->getLocation(LI); 126 return AliasAnalysis::Ref; 127 } 128 if (LI->getOrdering() == Monotonic) { 129 Loc = AA->getLocation(LI); 130 return AliasAnalysis::ModRef; 131 } 132 Loc = AliasAnalysis::Location(); 133 return AliasAnalysis::ModRef; 134 } 135 136 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 137 if (SI->isUnordered()) { 138 Loc = AA->getLocation(SI); 139 return AliasAnalysis::Mod; 140 } 141 if (SI->getOrdering() == Monotonic) { 142 Loc = AA->getLocation(SI); 143 return AliasAnalysis::ModRef; 144 } 145 Loc = AliasAnalysis::Location(); 146 return AliasAnalysis::ModRef; 147 } 148 149 if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) { 150 Loc = AA->getLocation(V); 151 return AliasAnalysis::ModRef; 152 } 153 154 if (const CallInst *CI = isFreeCall(Inst, AA->getTargetLibraryInfo())) { 155 // calls to free() deallocate the entire structure 156 Loc = AliasAnalysis::Location(CI->getArgOperand(0)); 157 return AliasAnalysis::Mod; 158 } 159 160 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) 161 switch (II->getIntrinsicID()) { 162 case Intrinsic::lifetime_start: 163 case Intrinsic::lifetime_end: 164 case Intrinsic::invariant_start: 165 Loc = AliasAnalysis::Location(II->getArgOperand(1), 166 cast<ConstantInt>(II->getArgOperand(0)) 167 ->getZExtValue(), 168 II->getMetadata(LLVMContext::MD_tbaa)); 169 // These intrinsics don't really modify the memory, but returning Mod 170 // will allow them to be handled conservatively. 171 return AliasAnalysis::Mod; 172 case Intrinsic::invariant_end: 173 Loc = AliasAnalysis::Location(II->getArgOperand(2), 174 cast<ConstantInt>(II->getArgOperand(1)) 175 ->getZExtValue(), 176 II->getMetadata(LLVMContext::MD_tbaa)); 177 // These intrinsics don't really modify the memory, but returning Mod 178 // will allow them to be handled conservatively. 179 return AliasAnalysis::Mod; 180 default: 181 break; 182 } 183 184 // Otherwise, just do the coarse-grained thing that always works. 185 if (Inst->mayWriteToMemory()) 186 return AliasAnalysis::ModRef; 187 if (Inst->mayReadFromMemory()) 188 return AliasAnalysis::Ref; 189 return AliasAnalysis::NoModRef; 190} 191 192/// getCallSiteDependencyFrom - Private helper for finding the local 193/// dependencies of a call site. 194MemDepResult MemoryDependenceAnalysis:: 195getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall, 196 BasicBlock::iterator ScanIt, BasicBlock *BB) { 197 unsigned Limit = BlockScanLimit; 198 199 // Walk backwards through the block, looking for dependencies 200 while (ScanIt != BB->begin()) { 201 // Limit the amount of scanning we do so we don't end up with quadratic 202 // running time on extreme testcases. 203 --Limit; 204 if (!Limit) 205 return MemDepResult::getUnknown(); 206 207 Instruction *Inst = --ScanIt; 208 209 // If this inst is a memory op, get the pointer it accessed 210 AliasAnalysis::Location Loc; 211 AliasAnalysis::ModRefResult MR = GetLocation(Inst, Loc, AA); 212 if (Loc.Ptr) { 213 // A simple instruction. 214 if (AA->getModRefInfo(CS, Loc) != AliasAnalysis::NoModRef) 215 return MemDepResult::getClobber(Inst); 216 continue; 217 } 218 219 if (CallSite InstCS = cast<Value>(Inst)) { 220 // Debug intrinsics don't cause dependences. 221 if (isa<DbgInfoIntrinsic>(Inst)) continue; 222 // If these two calls do not interfere, look past it. 223 switch (AA->getModRefInfo(CS, InstCS)) { 224 case AliasAnalysis::NoModRef: 225 // If the two calls are the same, return InstCS as a Def, so that 226 // CS can be found redundant and eliminated. 227 if (isReadOnlyCall && !(MR & AliasAnalysis::Mod) && 228 CS.getInstruction()->isIdenticalToWhenDefined(Inst)) 229 return MemDepResult::getDef(Inst); 230 231 // Otherwise if the two calls don't interact (e.g. InstCS is readnone) 232 // keep scanning. 233 continue; 234 default: 235 return MemDepResult::getClobber(Inst); 236 } 237 } 238 239 // If we could not obtain a pointer for the instruction and the instruction 240 // touches memory then assume that this is a dependency. 241 if (MR != AliasAnalysis::NoModRef) 242 return MemDepResult::getClobber(Inst); 243 } 244 245 // No dependence found. If this is the entry block of the function, it is 246 // unknown, otherwise it is non-local. 247 if (BB != &BB->getParent()->getEntryBlock()) 248 return MemDepResult::getNonLocal(); 249 return MemDepResult::getNonFuncLocal(); 250} 251 252/// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that 253/// would fully overlap MemLoc if done as a wider legal integer load. 254/// 255/// MemLocBase, MemLocOffset are lazily computed here the first time the 256/// base/offs of memloc is needed. 257static bool 258isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc, 259 const Value *&MemLocBase, 260 int64_t &MemLocOffs, 261 const LoadInst *LI, 262 const DataLayout *DL) { 263 // If we have no target data, we can't do this. 264 if (DL == 0) return false; 265 266 // If we haven't already computed the base/offset of MemLoc, do so now. 267 if (MemLocBase == 0) 268 MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, DL); 269 270 unsigned Size = MemoryDependenceAnalysis:: 271 getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size, 272 LI, *DL); 273 return Size != 0; 274} 275 276/// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that 277/// looks at a memory location for a load (specified by MemLocBase, Offs, 278/// and Size) and compares it against a load. If the specified load could 279/// be safely widened to a larger integer load that is 1) still efficient, 280/// 2) safe for the target, and 3) would provide the specified memory 281/// location value, then this function returns the size in bytes of the 282/// load width to use. If not, this returns zero. 283unsigned MemoryDependenceAnalysis:: 284getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs, 285 unsigned MemLocSize, const LoadInst *LI, 286 const DataLayout &DL) { 287 // We can only extend simple integer loads. 288 if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0; 289 290 // Load widening is hostile to ThreadSanitizer: it may cause false positives 291 // or make the reports more cryptic (access sizes are wrong). 292 if (LI->getParent()->getParent()->getAttributes(). 293 hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeThread)) 294 return 0; 295 296 // Get the base of this load. 297 int64_t LIOffs = 0; 298 const Value *LIBase = 299 GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, &DL); 300 301 // If the two pointers are not based on the same pointer, we can't tell that 302 // they are related. 303 if (LIBase != MemLocBase) return 0; 304 305 // Okay, the two values are based on the same pointer, but returned as 306 // no-alias. This happens when we have things like two byte loads at "P+1" 307 // and "P+3". Check to see if increasing the size of the "LI" load up to its 308 // alignment (or the largest native integer type) will allow us to load all 309 // the bits required by MemLoc. 310 311 // If MemLoc is before LI, then no widening of LI will help us out. 312 if (MemLocOffs < LIOffs) return 0; 313 314 // Get the alignment of the load in bytes. We assume that it is safe to load 315 // any legal integer up to this size without a problem. For example, if we're 316 // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can 317 // widen it up to an i32 load. If it is known 2-byte aligned, we can widen it 318 // to i16. 319 unsigned LoadAlign = LI->getAlignment(); 320 321 int64_t MemLocEnd = MemLocOffs+MemLocSize; 322 323 // If no amount of rounding up will let MemLoc fit into LI, then bail out. 324 if (LIOffs+LoadAlign < MemLocEnd) return 0; 325 326 // This is the size of the load to try. Start with the next larger power of 327 // two. 328 unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U; 329 NewLoadByteSize = NextPowerOf2(NewLoadByteSize); 330 331 while (1) { 332 // If this load size is bigger than our known alignment or would not fit 333 // into a native integer register, then we fail. 334 if (NewLoadByteSize > LoadAlign || 335 !DL.fitsInLegalInteger(NewLoadByteSize*8)) 336 return 0; 337 338 if (LIOffs+NewLoadByteSize > MemLocEnd && 339 LI->getParent()->getParent()->getAttributes(). 340 hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeAddress)) 341 // We will be reading past the location accessed by the original program. 342 // While this is safe in a regular build, Address Safety analysis tools 343 // may start reporting false warnings. So, don't do widening. 344 return 0; 345 346 // If a load of this width would include all of MemLoc, then we succeed. 347 if (LIOffs+NewLoadByteSize >= MemLocEnd) 348 return NewLoadByteSize; 349 350 NewLoadByteSize <<= 1; 351 } 352} 353 354/// getPointerDependencyFrom - Return the instruction on which a memory 355/// location depends. If isLoad is true, this routine ignores may-aliases with 356/// read-only operations. If isLoad is false, this routine ignores may-aliases 357/// with reads from read-only locations. If possible, pass the query 358/// instruction as well; this function may take advantage of the metadata 359/// annotated to the query instruction to refine the result. 360MemDepResult MemoryDependenceAnalysis:: 361getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad, 362 BasicBlock::iterator ScanIt, BasicBlock *BB, 363 Instruction *QueryInst) { 364 365 const Value *MemLocBase = 0; 366 int64_t MemLocOffset = 0; 367 unsigned Limit = BlockScanLimit; 368 bool isInvariantLoad = false; 369 if (isLoad && QueryInst) { 370 LoadInst *LI = dyn_cast<LoadInst>(QueryInst); 371 if (LI && LI->getMetadata(LLVMContext::MD_invariant_load) != 0) 372 isInvariantLoad = true; 373 } 374 375 // Walk backwards through the basic block, looking for dependencies. 376 while (ScanIt != BB->begin()) { 377 Instruction *Inst = --ScanIt; 378 379 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) 380 // Debug intrinsics don't (and can't) cause dependencies. 381 if (isa<DbgInfoIntrinsic>(II)) continue; 382 383 // Limit the amount of scanning we do so we don't end up with quadratic 384 // running time on extreme testcases. 385 --Limit; 386 if (!Limit) 387 return MemDepResult::getUnknown(); 388 389 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 390 // If we reach a lifetime begin or end marker, then the query ends here 391 // because the value is undefined. 392 if (II->getIntrinsicID() == Intrinsic::lifetime_start) { 393 // FIXME: This only considers queries directly on the invariant-tagged 394 // pointer, not on query pointers that are indexed off of them. It'd 395 // be nice to handle that at some point (the right approach is to use 396 // GetPointerBaseWithConstantOffset). 397 if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)), 398 MemLoc)) 399 return MemDepResult::getDef(II); 400 continue; 401 } 402 } 403 404 // Values depend on loads if the pointers are must aliased. This means that 405 // a load depends on another must aliased load from the same value. 406 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) { 407 // Atomic loads have complications involved. 408 // FIXME: This is overly conservative. 409 if (!LI->isUnordered()) 410 return MemDepResult::getClobber(LI); 411 412 AliasAnalysis::Location LoadLoc = AA->getLocation(LI); 413 414 // If we found a pointer, check if it could be the same as our pointer. 415 AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc); 416 417 if (isLoad) { 418 if (R == AliasAnalysis::NoAlias) { 419 // If this is an over-aligned integer load (for example, 420 // "load i8* %P, align 4") see if it would obviously overlap with the 421 // queried location if widened to a larger load (e.g. if the queried 422 // location is 1 byte at P+1). If so, return it as a load/load 423 // clobber result, allowing the client to decide to widen the load if 424 // it wants to. 425 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) 426 if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() && 427 isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase, 428 MemLocOffset, LI, DL)) 429 return MemDepResult::getClobber(Inst); 430 431 continue; 432 } 433 434 // Must aliased loads are defs of each other. 435 if (R == AliasAnalysis::MustAlias) 436 return MemDepResult::getDef(Inst); 437 438#if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads 439 // in terms of clobbering loads, but since it does this by looking 440 // at the clobbering load directly, it doesn't know about any 441 // phi translation that may have happened along the way. 442 443 // If we have a partial alias, then return this as a clobber for the 444 // client to handle. 445 if (R == AliasAnalysis::PartialAlias) 446 return MemDepResult::getClobber(Inst); 447#endif 448 449 // Random may-alias loads don't depend on each other without a 450 // dependence. 451 continue; 452 } 453 454 // Stores don't depend on other no-aliased accesses. 455 if (R == AliasAnalysis::NoAlias) 456 continue; 457 458 // Stores don't alias loads from read-only memory. 459 if (AA->pointsToConstantMemory(LoadLoc)) 460 continue; 461 462 // Stores depend on may/must aliased loads. 463 return MemDepResult::getDef(Inst); 464 } 465 466 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 467 // Atomic stores have complications involved. 468 // FIXME: This is overly conservative. 469 if (!SI->isUnordered()) 470 return MemDepResult::getClobber(SI); 471 472 // If alias analysis can tell that this store is guaranteed to not modify 473 // the query pointer, ignore it. Use getModRefInfo to handle cases where 474 // the query pointer points to constant memory etc. 475 if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef) 476 continue; 477 478 // Ok, this store might clobber the query pointer. Check to see if it is 479 // a must alias: in this case, we want to return this as a def. 480 AliasAnalysis::Location StoreLoc = AA->getLocation(SI); 481 482 // If we found a pointer, check if it could be the same as our pointer. 483 AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc); 484 485 if (R == AliasAnalysis::NoAlias) 486 continue; 487 if (R == AliasAnalysis::MustAlias) 488 return MemDepResult::getDef(Inst); 489 if (isInvariantLoad) 490 continue; 491 return MemDepResult::getClobber(Inst); 492 } 493 494 // If this is an allocation, and if we know that the accessed pointer is to 495 // the allocation, return Def. This means that there is no dependence and 496 // the access can be optimized based on that. For example, a load could 497 // turn into undef. 498 // Note: Only determine this to be a malloc if Inst is the malloc call, not 499 // a subsequent bitcast of the malloc call result. There can be stores to 500 // the malloced memory between the malloc call and its bitcast uses, and we 501 // need to continue scanning until the malloc call. 502 const TargetLibraryInfo *TLI = AA->getTargetLibraryInfo(); 503 if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, TLI)) { 504 const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, DL); 505 506 if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr)) 507 return MemDepResult::getDef(Inst); 508 // Be conservative if the accessed pointer may alias the allocation. 509 if (AA->alias(Inst, AccessPtr) != AliasAnalysis::NoAlias) 510 return MemDepResult::getClobber(Inst); 511 // If the allocation is not aliased and does not read memory (like 512 // strdup), it is safe to ignore. 513 if (isa<AllocaInst>(Inst) || 514 isMallocLikeFn(Inst, TLI) || isCallocLikeFn(Inst, TLI)) 515 continue; 516 } 517 518 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer. 519 AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc); 520 // If necessary, perform additional analysis. 521 if (MR == AliasAnalysis::ModRef) 522 MR = AA->callCapturesBefore(Inst, MemLoc, DT); 523 switch (MR) { 524 case AliasAnalysis::NoModRef: 525 // If the call has no effect on the queried pointer, just ignore it. 526 continue; 527 case AliasAnalysis::Mod: 528 return MemDepResult::getClobber(Inst); 529 case AliasAnalysis::Ref: 530 // If the call is known to never store to the pointer, and if this is a 531 // load query, we can safely ignore it (scan past it). 532 if (isLoad) 533 continue; 534 default: 535 // Otherwise, there is a potential dependence. Return a clobber. 536 return MemDepResult::getClobber(Inst); 537 } 538 } 539 540 // No dependence found. If this is the entry block of the function, it is 541 // unknown, otherwise it is non-local. 542 if (BB != &BB->getParent()->getEntryBlock()) 543 return MemDepResult::getNonLocal(); 544 return MemDepResult::getNonFuncLocal(); 545} 546 547/// getDependency - Return the instruction on which a memory operation 548/// depends. 549MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) { 550 Instruction *ScanPos = QueryInst; 551 552 // Check for a cached result 553 MemDepResult &LocalCache = LocalDeps[QueryInst]; 554 555 // If the cached entry is non-dirty, just return it. Note that this depends 556 // on MemDepResult's default constructing to 'dirty'. 557 if (!LocalCache.isDirty()) 558 return LocalCache; 559 560 // Otherwise, if we have a dirty entry, we know we can start the scan at that 561 // instruction, which may save us some work. 562 if (Instruction *Inst = LocalCache.getInst()) { 563 ScanPos = Inst; 564 565 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst); 566 } 567 568 BasicBlock *QueryParent = QueryInst->getParent(); 569 570 // Do the scan. 571 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) { 572 // No dependence found. If this is the entry block of the function, it is 573 // unknown, otherwise it is non-local. 574 if (QueryParent != &QueryParent->getParent()->getEntryBlock()) 575 LocalCache = MemDepResult::getNonLocal(); 576 else 577 LocalCache = MemDepResult::getNonFuncLocal(); 578 } else { 579 AliasAnalysis::Location MemLoc; 580 AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA); 581 if (MemLoc.Ptr) { 582 // If we can do a pointer scan, make it happen. 583 bool isLoad = !(MR & AliasAnalysis::Mod); 584 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst)) 585 isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start; 586 587 LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos, 588 QueryParent, QueryInst); 589 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) { 590 CallSite QueryCS(QueryInst); 591 bool isReadOnly = AA->onlyReadsMemory(QueryCS); 592 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos, 593 QueryParent); 594 } else 595 // Non-memory instruction. 596 LocalCache = MemDepResult::getUnknown(); 597 } 598 599 // Remember the result! 600 if (Instruction *I = LocalCache.getInst()) 601 ReverseLocalDeps[I].insert(QueryInst); 602 603 return LocalCache; 604} 605 606#ifndef NDEBUG 607/// AssertSorted - This method is used when -debug is specified to verify that 608/// cache arrays are properly kept sorted. 609static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache, 610 int Count = -1) { 611 if (Count == -1) Count = Cache.size(); 612 if (Count == 0) return; 613 614 for (unsigned i = 1; i != unsigned(Count); ++i) 615 assert(!(Cache[i] < Cache[i-1]) && "Cache isn't sorted!"); 616} 617#endif 618 619/// getNonLocalCallDependency - Perform a full dependency query for the 620/// specified call, returning the set of blocks that the value is 621/// potentially live across. The returned set of results will include a 622/// "NonLocal" result for all blocks where the value is live across. 623/// 624/// This method assumes the instruction returns a "NonLocal" dependency 625/// within its own block. 626/// 627/// This returns a reference to an internal data structure that may be 628/// invalidated on the next non-local query or when an instruction is 629/// removed. Clients must copy this data if they want it around longer than 630/// that. 631const MemoryDependenceAnalysis::NonLocalDepInfo & 632MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) { 633 assert(getDependency(QueryCS.getInstruction()).isNonLocal() && 634 "getNonLocalCallDependency should only be used on calls with non-local deps!"); 635 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()]; 636 NonLocalDepInfo &Cache = CacheP.first; 637 638 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In 639 /// the cached case, this can happen due to instructions being deleted etc. In 640 /// the uncached case, this starts out as the set of predecessors we care 641 /// about. 642 SmallVector<BasicBlock*, 32> DirtyBlocks; 643 644 if (!Cache.empty()) { 645 // Okay, we have a cache entry. If we know it is not dirty, just return it 646 // with no computation. 647 if (!CacheP.second) { 648 ++NumCacheNonLocal; 649 return Cache; 650 } 651 652 // If we already have a partially computed set of results, scan them to 653 // determine what is dirty, seeding our initial DirtyBlocks worklist. 654 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end(); 655 I != E; ++I) 656 if (I->getResult().isDirty()) 657 DirtyBlocks.push_back(I->getBB()); 658 659 // Sort the cache so that we can do fast binary search lookups below. 660 std::sort(Cache.begin(), Cache.end()); 661 662 ++NumCacheDirtyNonLocal; 663 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: " 664 // << Cache.size() << " cached: " << *QueryInst; 665 } else { 666 // Seed DirtyBlocks with each of the preds of QueryInst's block. 667 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent(); 668 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI) 669 DirtyBlocks.push_back(*PI); 670 ++NumUncacheNonLocal; 671 } 672 673 // isReadonlyCall - If this is a read-only call, we can be more aggressive. 674 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS); 675 676 SmallPtrSet<BasicBlock*, 64> Visited; 677 678 unsigned NumSortedEntries = Cache.size(); 679 DEBUG(AssertSorted(Cache)); 680 681 // Iterate while we still have blocks to update. 682 while (!DirtyBlocks.empty()) { 683 BasicBlock *DirtyBB = DirtyBlocks.back(); 684 DirtyBlocks.pop_back(); 685 686 // Already processed this block? 687 if (!Visited.insert(DirtyBB)) 688 continue; 689 690 // Do a binary search to see if we already have an entry for this block in 691 // the cache set. If so, find it. 692 DEBUG(AssertSorted(Cache, NumSortedEntries)); 693 NonLocalDepInfo::iterator Entry = 694 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries, 695 NonLocalDepEntry(DirtyBB)); 696 if (Entry != Cache.begin() && std::prev(Entry)->getBB() == DirtyBB) 697 --Entry; 698 699 NonLocalDepEntry *ExistingResult = 0; 700 if (Entry != Cache.begin()+NumSortedEntries && 701 Entry->getBB() == DirtyBB) { 702 // If we already have an entry, and if it isn't already dirty, the block 703 // is done. 704 if (!Entry->getResult().isDirty()) 705 continue; 706 707 // Otherwise, remember this slot so we can update the value. 708 ExistingResult = &*Entry; 709 } 710 711 // If the dirty entry has a pointer, start scanning from it so we don't have 712 // to rescan the entire block. 713 BasicBlock::iterator ScanPos = DirtyBB->end(); 714 if (ExistingResult) { 715 if (Instruction *Inst = ExistingResult->getResult().getInst()) { 716 ScanPos = Inst; 717 // We're removing QueryInst's use of Inst. 718 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, 719 QueryCS.getInstruction()); 720 } 721 } 722 723 // Find out if this block has a local dependency for QueryInst. 724 MemDepResult Dep; 725 726 if (ScanPos != DirtyBB->begin()) { 727 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB); 728 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) { 729 // No dependence found. If this is the entry block of the function, it is 730 // a clobber, otherwise it is unknown. 731 Dep = MemDepResult::getNonLocal(); 732 } else { 733 Dep = MemDepResult::getNonFuncLocal(); 734 } 735 736 // If we had a dirty entry for the block, update it. Otherwise, just add 737 // a new entry. 738 if (ExistingResult) 739 ExistingResult->setResult(Dep); 740 else 741 Cache.push_back(NonLocalDepEntry(DirtyBB, Dep)); 742 743 // If the block has a dependency (i.e. it isn't completely transparent to 744 // the value), remember the association! 745 if (!Dep.isNonLocal()) { 746 // Keep the ReverseNonLocalDeps map up to date so we can efficiently 747 // update this when we remove instructions. 748 if (Instruction *Inst = Dep.getInst()) 749 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction()); 750 } else { 751 752 // If the block *is* completely transparent to the load, we need to check 753 // the predecessors of this block. Add them to our worklist. 754 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI) 755 DirtyBlocks.push_back(*PI); 756 } 757 } 758 759 return Cache; 760} 761 762/// getNonLocalPointerDependency - Perform a full dependency query for an 763/// access to the specified (non-volatile) memory location, returning the 764/// set of instructions that either define or clobber the value. 765/// 766/// This method assumes the pointer has a "NonLocal" dependency within its 767/// own block. 768/// 769void MemoryDependenceAnalysis:: 770getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad, 771 BasicBlock *FromBB, 772 SmallVectorImpl<NonLocalDepResult> &Result) { 773 assert(Loc.Ptr->getType()->isPointerTy() && 774 "Can't get pointer deps of a non-pointer!"); 775 Result.clear(); 776 777 PHITransAddr Address(const_cast<Value *>(Loc.Ptr), DL); 778 779 // This is the set of blocks we've inspected, and the pointer we consider in 780 // each block. Because of critical edges, we currently bail out if querying 781 // a block with multiple different pointers. This can happen during PHI 782 // translation. 783 DenseMap<BasicBlock*, Value*> Visited; 784 if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB, 785 Result, Visited, true)) 786 return; 787 Result.clear(); 788 Result.push_back(NonLocalDepResult(FromBB, 789 MemDepResult::getUnknown(), 790 const_cast<Value *>(Loc.Ptr))); 791} 792 793/// GetNonLocalInfoForBlock - Compute the memdep value for BB with 794/// Pointer/PointeeSize using either cached information in Cache or by doing a 795/// lookup (which may use dirty cache info if available). If we do a lookup, 796/// add the result to the cache. 797MemDepResult MemoryDependenceAnalysis:: 798GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc, 799 bool isLoad, BasicBlock *BB, 800 NonLocalDepInfo *Cache, unsigned NumSortedEntries) { 801 802 // Do a binary search to see if we already have an entry for this block in 803 // the cache set. If so, find it. 804 NonLocalDepInfo::iterator Entry = 805 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries, 806 NonLocalDepEntry(BB)); 807 if (Entry != Cache->begin() && (Entry-1)->getBB() == BB) 808 --Entry; 809 810 NonLocalDepEntry *ExistingResult = 0; 811 if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB) 812 ExistingResult = &*Entry; 813 814 // If we have a cached entry, and it is non-dirty, use it as the value for 815 // this dependency. 816 if (ExistingResult && !ExistingResult->getResult().isDirty()) { 817 ++NumCacheNonLocalPtr; 818 return ExistingResult->getResult(); 819 } 820 821 // Otherwise, we have to scan for the value. If we have a dirty cache 822 // entry, start scanning from its position, otherwise we scan from the end 823 // of the block. 824 BasicBlock::iterator ScanPos = BB->end(); 825 if (ExistingResult && ExistingResult->getResult().getInst()) { 826 assert(ExistingResult->getResult().getInst()->getParent() == BB && 827 "Instruction invalidated?"); 828 ++NumCacheDirtyNonLocalPtr; 829 ScanPos = ExistingResult->getResult().getInst(); 830 831 // Eliminating the dirty entry from 'Cache', so update the reverse info. 832 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad); 833 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey); 834 } else { 835 ++NumUncacheNonLocalPtr; 836 } 837 838 // Scan the block for the dependency. 839 MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB); 840 841 // If we had a dirty entry for the block, update it. Otherwise, just add 842 // a new entry. 843 if (ExistingResult) 844 ExistingResult->setResult(Dep); 845 else 846 Cache->push_back(NonLocalDepEntry(BB, Dep)); 847 848 // If the block has a dependency (i.e. it isn't completely transparent to 849 // the value), remember the reverse association because we just added it 850 // to Cache! 851 if (!Dep.isDef() && !Dep.isClobber()) 852 return Dep; 853 854 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently 855 // update MemDep when we remove instructions. 856 Instruction *Inst = Dep.getInst(); 857 assert(Inst && "Didn't depend on anything?"); 858 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad); 859 ReverseNonLocalPtrDeps[Inst].insert(CacheKey); 860 return Dep; 861} 862 863/// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain 864/// number of elements in the array that are already properly ordered. This is 865/// optimized for the case when only a few entries are added. 866static void 867SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache, 868 unsigned NumSortedEntries) { 869 switch (Cache.size() - NumSortedEntries) { 870 case 0: 871 // done, no new entries. 872 break; 873 case 2: { 874 // Two new entries, insert the last one into place. 875 NonLocalDepEntry Val = Cache.back(); 876 Cache.pop_back(); 877 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry = 878 std::upper_bound(Cache.begin(), Cache.end()-1, Val); 879 Cache.insert(Entry, Val); 880 // FALL THROUGH. 881 } 882 case 1: 883 // One new entry, Just insert the new value at the appropriate position. 884 if (Cache.size() != 1) { 885 NonLocalDepEntry Val = Cache.back(); 886 Cache.pop_back(); 887 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry = 888 std::upper_bound(Cache.begin(), Cache.end(), Val); 889 Cache.insert(Entry, Val); 890 } 891 break; 892 default: 893 // Added many values, do a full scale sort. 894 std::sort(Cache.begin(), Cache.end()); 895 break; 896 } 897} 898 899/// getNonLocalPointerDepFromBB - Perform a dependency query based on 900/// pointer/pointeesize starting at the end of StartBB. Add any clobber/def 901/// results to the results vector and keep track of which blocks are visited in 902/// 'Visited'. 903/// 904/// This has special behavior for the first block queries (when SkipFirstBlock 905/// is true). In this special case, it ignores the contents of the specified 906/// block and starts returning dependence info for its predecessors. 907/// 908/// This function returns false on success, or true to indicate that it could 909/// not compute dependence information for some reason. This should be treated 910/// as a clobber dependence on the first instruction in the predecessor block. 911bool MemoryDependenceAnalysis:: 912getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, 913 const AliasAnalysis::Location &Loc, 914 bool isLoad, BasicBlock *StartBB, 915 SmallVectorImpl<NonLocalDepResult> &Result, 916 DenseMap<BasicBlock*, Value*> &Visited, 917 bool SkipFirstBlock) { 918 // Look up the cached info for Pointer. 919 ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad); 920 921 // Set up a temporary NLPI value. If the map doesn't yet have an entry for 922 // CacheKey, this value will be inserted as the associated value. Otherwise, 923 // it'll be ignored, and we'll have to check to see if the cached size and 924 // tbaa tag are consistent with the current query. 925 NonLocalPointerInfo InitialNLPI; 926 InitialNLPI.Size = Loc.Size; 927 InitialNLPI.TBAATag = Loc.TBAATag; 928 929 // Get the NLPI for CacheKey, inserting one into the map if it doesn't 930 // already have one. 931 std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair = 932 NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI)); 933 NonLocalPointerInfo *CacheInfo = &Pair.first->second; 934 935 // If we already have a cache entry for this CacheKey, we may need to do some 936 // work to reconcile the cache entry and the current query. 937 if (!Pair.second) { 938 if (CacheInfo->Size < Loc.Size) { 939 // The query's Size is greater than the cached one. Throw out the 940 // cached data and proceed with the query at the greater size. 941 CacheInfo->Pair = BBSkipFirstBlockPair(); 942 CacheInfo->Size = Loc.Size; 943 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(), 944 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI) 945 if (Instruction *Inst = DI->getResult().getInst()) 946 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey); 947 CacheInfo->NonLocalDeps.clear(); 948 } else if (CacheInfo->Size > Loc.Size) { 949 // This query's Size is less than the cached one. Conservatively restart 950 // the query using the greater size. 951 return getNonLocalPointerDepFromBB(Pointer, 952 Loc.getWithNewSize(CacheInfo->Size), 953 isLoad, StartBB, Result, Visited, 954 SkipFirstBlock); 955 } 956 957 // If the query's TBAATag is inconsistent with the cached one, 958 // conservatively throw out the cached data and restart the query with 959 // no tag if needed. 960 if (CacheInfo->TBAATag != Loc.TBAATag) { 961 if (CacheInfo->TBAATag) { 962 CacheInfo->Pair = BBSkipFirstBlockPair(); 963 CacheInfo->TBAATag = 0; 964 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(), 965 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI) 966 if (Instruction *Inst = DI->getResult().getInst()) 967 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey); 968 CacheInfo->NonLocalDeps.clear(); 969 } 970 if (Loc.TBAATag) 971 return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(), 972 isLoad, StartBB, Result, Visited, 973 SkipFirstBlock); 974 } 975 } 976 977 NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps; 978 979 // If we have valid cached information for exactly the block we are 980 // investigating, just return it with no recomputation. 981 if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) { 982 // We have a fully cached result for this query then we can just return the 983 // cached results and populate the visited set. However, we have to verify 984 // that we don't already have conflicting results for these blocks. Check 985 // to ensure that if a block in the results set is in the visited set that 986 // it was for the same pointer query. 987 if (!Visited.empty()) { 988 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end(); 989 I != E; ++I) { 990 DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->getBB()); 991 if (VI == Visited.end() || VI->second == Pointer.getAddr()) 992 continue; 993 994 // We have a pointer mismatch in a block. Just return clobber, saying 995 // that something was clobbered in this result. We could also do a 996 // non-fully cached query, but there is little point in doing this. 997 return true; 998 } 999 } 1000 1001 Value *Addr = Pointer.getAddr(); 1002 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end(); 1003 I != E; ++I) { 1004 Visited.insert(std::make_pair(I->getBB(), Addr)); 1005 if (I->getResult().isNonLocal()) { 1006 continue; 1007 } 1008 1009 if (!DT) { 1010 Result.push_back(NonLocalDepResult(I->getBB(), 1011 MemDepResult::getUnknown(), 1012 Addr)); 1013 } else if (DT->isReachableFromEntry(I->getBB())) { 1014 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr)); 1015 } 1016 } 1017 ++NumCacheCompleteNonLocalPtr; 1018 return false; 1019 } 1020 1021 // Otherwise, either this is a new block, a block with an invalid cache 1022 // pointer or one that we're about to invalidate by putting more info into it 1023 // than its valid cache info. If empty, the result will be valid cache info, 1024 // otherwise it isn't. 1025 if (Cache->empty()) 1026 CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock); 1027 else 1028 CacheInfo->Pair = BBSkipFirstBlockPair(); 1029 1030 SmallVector<BasicBlock*, 32> Worklist; 1031 Worklist.push_back(StartBB); 1032 1033 // PredList used inside loop. 1034 SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList; 1035 1036 // Keep track of the entries that we know are sorted. Previously cached 1037 // entries will all be sorted. The entries we add we only sort on demand (we 1038 // don't insert every element into its sorted position). We know that we 1039 // won't get any reuse from currently inserted values, because we don't 1040 // revisit blocks after we insert info for them. 1041 unsigned NumSortedEntries = Cache->size(); 1042 DEBUG(AssertSorted(*Cache)); 1043 1044 while (!Worklist.empty()) { 1045 BasicBlock *BB = Worklist.pop_back_val(); 1046 1047 // Skip the first block if we have it. 1048 if (!SkipFirstBlock) { 1049 // Analyze the dependency of *Pointer in FromBB. See if we already have 1050 // been here. 1051 assert(Visited.count(BB) && "Should check 'visited' before adding to WL"); 1052 1053 // Get the dependency info for Pointer in BB. If we have cached 1054 // information, we will use it, otherwise we compute it. 1055 DEBUG(AssertSorted(*Cache, NumSortedEntries)); 1056 MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache, 1057 NumSortedEntries); 1058 1059 // If we got a Def or Clobber, add this to the list of results. 1060 if (!Dep.isNonLocal()) { 1061 if (!DT) { 1062 Result.push_back(NonLocalDepResult(BB, 1063 MemDepResult::getUnknown(), 1064 Pointer.getAddr())); 1065 continue; 1066 } else if (DT->isReachableFromEntry(BB)) { 1067 Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr())); 1068 continue; 1069 } 1070 } 1071 } 1072 1073 // If 'Pointer' is an instruction defined in this block, then we need to do 1074 // phi translation to change it into a value live in the predecessor block. 1075 // If not, we just add the predecessors to the worklist and scan them with 1076 // the same Pointer. 1077 if (!Pointer.NeedsPHITranslationFromBlock(BB)) { 1078 SkipFirstBlock = false; 1079 SmallVector<BasicBlock*, 16> NewBlocks; 1080 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { 1081 // Verify that we haven't looked at this block yet. 1082 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool> 1083 InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr())); 1084 if (InsertRes.second) { 1085 // First time we've looked at *PI. 1086 NewBlocks.push_back(*PI); 1087 continue; 1088 } 1089 1090 // If we have seen this block before, but it was with a different 1091 // pointer then we have a phi translation failure and we have to treat 1092 // this as a clobber. 1093 if (InsertRes.first->second != Pointer.getAddr()) { 1094 // Make sure to clean up the Visited map before continuing on to 1095 // PredTranslationFailure. 1096 for (unsigned i = 0; i < NewBlocks.size(); i++) 1097 Visited.erase(NewBlocks[i]); 1098 goto PredTranslationFailure; 1099 } 1100 } 1101 Worklist.append(NewBlocks.begin(), NewBlocks.end()); 1102 continue; 1103 } 1104 1105 // We do need to do phi translation, if we know ahead of time we can't phi 1106 // translate this value, don't even try. 1107 if (!Pointer.IsPotentiallyPHITranslatable()) 1108 goto PredTranslationFailure; 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 Cache = 0; 1120 1121 PredList.clear(); 1122 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { 1123 BasicBlock *Pred = *PI; 1124 PredList.push_back(std::make_pair(Pred, Pointer)); 1125 1126 // Get the PHI translated pointer in this predecessor. This can fail if 1127 // not translatable, in which case the getAddr() returns null. 1128 PHITransAddr &PredPointer = PredList.back().second; 1129 PredPointer.PHITranslateValue(BB, Pred, 0); 1130 1131 Value *PredPtrVal = PredPointer.getAddr(); 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, PredPtrVal)); 1140 1141 if (!InsertRes.second) { 1142 // We found the pred; take it off the list of preds to visit. 1143 PredList.pop_back(); 1144 1145 // If the predecessor was visited with PredPtr, then we already did 1146 // the analysis and can ignore it. 1147 if (InsertRes.first->second == PredPtrVal) 1148 continue; 1149 1150 // Otherwise, the block was previously analyzed with a different 1151 // pointer. We can't represent the result of this case, so we just 1152 // treat this as a phi translation failure. 1153 1154 // Make sure to clean up the Visited map before continuing on to 1155 // PredTranslationFailure. 1156 for (unsigned i = 0, n = PredList.size(); i < n; ++i) 1157 Visited.erase(PredList[i].first); 1158 1159 goto PredTranslationFailure; 1160 } 1161 } 1162 1163 // Actually process results here; this need to be a separate loop to avoid 1164 // calling getNonLocalPointerDepFromBB for blocks we don't want to return 1165 // any results for. (getNonLocalPointerDepFromBB will modify our 1166 // datastructures in ways the code after the PredTranslationFailure label 1167 // doesn't expect.) 1168 for (unsigned i = 0, n = PredList.size(); i < n; ++i) { 1169 BasicBlock *Pred = PredList[i].first; 1170 PHITransAddr &PredPointer = PredList[i].second; 1171 Value *PredPtrVal = PredPointer.getAddr(); 1172 1173 bool CanTranslate = true; 1174 // If PHI translation was unable to find an available pointer in this 1175 // predecessor, then we have to assume that the pointer is clobbered in 1176 // that predecessor. We can still do PRE of the load, which would insert 1177 // a computation of the pointer in this predecessor. 1178 if (PredPtrVal == 0) 1179 CanTranslate = false; 1180 1181 // FIXME: it is entirely possible that PHI translating will end up with 1182 // the same value. Consider PHI translating something like: 1183 // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need* 1184 // to recurse here, pedantically speaking. 1185 1186 // If getNonLocalPointerDepFromBB fails here, that means the cached 1187 // result conflicted with the Visited list; we have to conservatively 1188 // assume it is unknown, but this also does not block PRE of the load. 1189 if (!CanTranslate || 1190 getNonLocalPointerDepFromBB(PredPointer, 1191 Loc.getWithNewPtr(PredPtrVal), 1192 isLoad, Pred, 1193 Result, Visited)) { 1194 // Add the entry to the Result list. 1195 NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal); 1196 Result.push_back(Entry); 1197 1198 // Since we had a phi translation failure, the cache for CacheKey won't 1199 // include all of the entries that we need to immediately satisfy future 1200 // queries. Mark this in NonLocalPointerDeps by setting the 1201 // BBSkipFirstBlockPair pointer to null. This requires reuse of the 1202 // cached value to do more work but not miss the phi trans failure. 1203 NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey]; 1204 NLPI.Pair = BBSkipFirstBlockPair(); 1205 continue; 1206 } 1207 } 1208 1209 // Refresh the CacheInfo/Cache pointer so that it isn't invalidated. 1210 CacheInfo = &NonLocalPointerDeps[CacheKey]; 1211 Cache = &CacheInfo->NonLocalDeps; 1212 NumSortedEntries = Cache->size(); 1213 1214 // Since we did phi translation, the "Cache" set won't contain all of the 1215 // results for the query. This is ok (we can still use it to accelerate 1216 // specific block queries) but we can't do the fastpath "return all 1217 // results from the set" Clear out the indicator for this. 1218 CacheInfo->Pair = BBSkipFirstBlockPair(); 1219 SkipFirstBlock = false; 1220 continue; 1221 1222 PredTranslationFailure: 1223 // The following code is "failure"; we can't produce a sane translation 1224 // for the given block. It assumes that we haven't modified any of 1225 // our datastructures while processing the current block. 1226 1227 if (Cache == 0) { 1228 // Refresh the CacheInfo/Cache pointer if it got invalidated. 1229 CacheInfo = &NonLocalPointerDeps[CacheKey]; 1230 Cache = &CacheInfo->NonLocalDeps; 1231 NumSortedEntries = Cache->size(); 1232 } 1233 1234 // Since we failed phi translation, the "Cache" set won't contain all of the 1235 // results for the query. This is ok (we can still use it to accelerate 1236 // specific block queries) but we can't do the fastpath "return all 1237 // results from the set". Clear out the indicator for this. 1238 CacheInfo->Pair = BBSkipFirstBlockPair(); 1239 1240 // If *nothing* works, mark the pointer as unknown. 1241 // 1242 // If this is the magic first block, return this as a clobber of the whole 1243 // incoming value. Since we can't phi translate to one of the predecessors, 1244 // we have to bail out. 1245 if (SkipFirstBlock) 1246 return true; 1247 1248 for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) { 1249 assert(I != Cache->rend() && "Didn't find current block??"); 1250 if (I->getBB() != BB) 1251 continue; 1252 1253 assert(I->getResult().isNonLocal() && 1254 "Should only be here with transparent block"); 1255 I->setResult(MemDepResult::getUnknown()); 1256 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), 1257 Pointer.getAddr())); 1258 break; 1259 } 1260 } 1261 1262 // Okay, we're done now. If we added new values to the cache, re-sort it. 1263 SortNonLocalDepInfoCache(*Cache, NumSortedEntries); 1264 DEBUG(AssertSorted(*Cache)); 1265 return false; 1266} 1267 1268/// RemoveCachedNonLocalPointerDependencies - If P exists in 1269/// CachedNonLocalPointerInfo, remove it. 1270void MemoryDependenceAnalysis:: 1271RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) { 1272 CachedNonLocalPointerInfo::iterator It = 1273 NonLocalPointerDeps.find(P); 1274 if (It == NonLocalPointerDeps.end()) return; 1275 1276 // Remove all of the entries in the BB->val map. This involves removing 1277 // instructions from the reverse map. 1278 NonLocalDepInfo &PInfo = It->second.NonLocalDeps; 1279 1280 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) { 1281 Instruction *Target = PInfo[i].getResult().getInst(); 1282 if (Target == 0) continue; // Ignore non-local dep results. 1283 assert(Target->getParent() == PInfo[i].getBB()); 1284 1285 // Eliminating the dirty entry from 'Cache', so update the reverse info. 1286 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P); 1287 } 1288 1289 // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo). 1290 NonLocalPointerDeps.erase(It); 1291} 1292 1293 1294/// invalidateCachedPointerInfo - This method is used to invalidate cached 1295/// information about the specified pointer, because it may be too 1296/// conservative in memdep. This is an optional call that can be used when 1297/// the client detects an equivalence between the pointer and some other 1298/// value and replaces the other value with ptr. This can make Ptr available 1299/// in more places that cached info does not necessarily keep. 1300void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) { 1301 // If Ptr isn't really a pointer, just ignore it. 1302 if (!Ptr->getType()->isPointerTy()) return; 1303 // Flush store info for the pointer. 1304 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false)); 1305 // Flush load info for the pointer. 1306 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true)); 1307} 1308 1309/// invalidateCachedPredecessors - Clear the PredIteratorCache info. 1310/// This needs to be done when the CFG changes, e.g., due to splitting 1311/// critical edges. 1312void MemoryDependenceAnalysis::invalidateCachedPredecessors() { 1313 PredCache->clear(); 1314} 1315 1316/// removeInstruction - Remove an instruction from the dependence analysis, 1317/// updating the dependence of instructions that previously depended on it. 1318/// This method attempts to keep the cache coherent using the reverse map. 1319void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) { 1320 // Walk through the Non-local dependencies, removing this one as the value 1321 // for any cached queries. 1322 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst); 1323 if (NLDI != NonLocalDeps.end()) { 1324 NonLocalDepInfo &BlockMap = NLDI->second.first; 1325 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end(); 1326 DI != DE; ++DI) 1327 if (Instruction *Inst = DI->getResult().getInst()) 1328 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst); 1329 NonLocalDeps.erase(NLDI); 1330 } 1331 1332 // If we have a cached local dependence query for this instruction, remove it. 1333 // 1334 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst); 1335 if (LocalDepEntry != LocalDeps.end()) { 1336 // Remove us from DepInst's reverse set now that the local dep info is gone. 1337 if (Instruction *Inst = LocalDepEntry->second.getInst()) 1338 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst); 1339 1340 // Remove this local dependency info. 1341 LocalDeps.erase(LocalDepEntry); 1342 } 1343 1344 // If we have any cached pointer dependencies on this instruction, remove 1345 // them. If the instruction has non-pointer type, then it can't be a pointer 1346 // base. 1347 1348 // Remove it from both the load info and the store info. The instruction 1349 // can't be in either of these maps if it is non-pointer. 1350 if (RemInst->getType()->isPointerTy()) { 1351 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false)); 1352 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true)); 1353 } 1354 1355 // Loop over all of the things that depend on the instruction we're removing. 1356 // 1357 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd; 1358 1359 // If we find RemInst as a clobber or Def in any of the maps for other values, 1360 // we need to replace its entry with a dirty version of the instruction after 1361 // it. If RemInst is a terminator, we use a null dirty value. 1362 // 1363 // Using a dirty version of the instruction after RemInst saves having to scan 1364 // the entire block to get to this point. 1365 MemDepResult NewDirtyVal; 1366 if (!RemInst->isTerminator()) 1367 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst)); 1368 1369 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst); 1370 if (ReverseDepIt != ReverseLocalDeps.end()) { 1371 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second; 1372 // RemInst can't be the terminator if it has local stuff depending on it. 1373 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) && 1374 "Nothing can locally depend on a terminator"); 1375 1376 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(), 1377 E = ReverseDeps.end(); I != E; ++I) { 1378 Instruction *InstDependingOnRemInst = *I; 1379 assert(InstDependingOnRemInst != RemInst && 1380 "Already removed our local dep info"); 1381 1382 LocalDeps[InstDependingOnRemInst] = NewDirtyVal; 1383 1384 // Make sure to remember that new things depend on NewDepInst. 1385 assert(NewDirtyVal.getInst() && "There is no way something else can have " 1386 "a local dep on this if it is a terminator!"); 1387 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(), 1388 InstDependingOnRemInst)); 1389 } 1390 1391 ReverseLocalDeps.erase(ReverseDepIt); 1392 1393 // Add new reverse deps after scanning the set, to avoid invalidating the 1394 // 'ReverseDeps' reference. 1395 while (!ReverseDepsToAdd.empty()) { 1396 ReverseLocalDeps[ReverseDepsToAdd.back().first] 1397 .insert(ReverseDepsToAdd.back().second); 1398 ReverseDepsToAdd.pop_back(); 1399 } 1400 } 1401 1402 ReverseDepIt = ReverseNonLocalDeps.find(RemInst); 1403 if (ReverseDepIt != ReverseNonLocalDeps.end()) { 1404 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second; 1405 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end(); 1406 I != E; ++I) { 1407 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst"); 1408 1409 PerInstNLInfo &INLD = NonLocalDeps[*I]; 1410 // The information is now dirty! 1411 INLD.second = true; 1412 1413 for (NonLocalDepInfo::iterator DI = INLD.first.begin(), 1414 DE = INLD.first.end(); DI != DE; ++DI) { 1415 if (DI->getResult().getInst() != RemInst) continue; 1416 1417 // Convert to a dirty entry for the subsequent instruction. 1418 DI->setResult(NewDirtyVal); 1419 1420 if (Instruction *NextI = NewDirtyVal.getInst()) 1421 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I)); 1422 } 1423 } 1424 1425 ReverseNonLocalDeps.erase(ReverseDepIt); 1426 1427 // Add new reverse deps after scanning the set, to avoid invalidating 'Set' 1428 while (!ReverseDepsToAdd.empty()) { 1429 ReverseNonLocalDeps[ReverseDepsToAdd.back().first] 1430 .insert(ReverseDepsToAdd.back().second); 1431 ReverseDepsToAdd.pop_back(); 1432 } 1433 } 1434 1435 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a 1436 // value in the NonLocalPointerDeps info. 1437 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt = 1438 ReverseNonLocalPtrDeps.find(RemInst); 1439 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) { 1440 SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second; 1441 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd; 1442 1443 for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(), 1444 E = Set.end(); I != E; ++I) { 1445 ValueIsLoadPair P = *I; 1446 assert(P.getPointer() != RemInst && 1447 "Already removed NonLocalPointerDeps info for RemInst"); 1448 1449 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps; 1450 1451 // The cache is not valid for any specific block anymore. 1452 NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair(); 1453 1454 // Update any entries for RemInst to use the instruction after it. 1455 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end(); 1456 DI != DE; ++DI) { 1457 if (DI->getResult().getInst() != RemInst) continue; 1458 1459 // Convert to a dirty entry for the subsequent instruction. 1460 DI->setResult(NewDirtyVal); 1461 1462 if (Instruction *NewDirtyInst = NewDirtyVal.getInst()) 1463 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P)); 1464 } 1465 1466 // Re-sort the NonLocalDepInfo. Changing the dirty entry to its 1467 // subsequent value may invalidate the sortedness. 1468 std::sort(NLPDI.begin(), NLPDI.end()); 1469 } 1470 1471 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt); 1472 1473 while (!ReversePtrDepsToAdd.empty()) { 1474 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first] 1475 .insert(ReversePtrDepsToAdd.back().second); 1476 ReversePtrDepsToAdd.pop_back(); 1477 } 1478 } 1479 1480 1481 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?"); 1482 AA->deleteValue(RemInst); 1483 DEBUG(verifyRemoved(RemInst)); 1484} 1485/// verifyRemoved - Verify that the specified instruction does not occur 1486/// in our internal data structures. 1487void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const { 1488 for (LocalDepMapType::const_iterator I = LocalDeps.begin(), 1489 E = LocalDeps.end(); I != E; ++I) { 1490 assert(I->first != D && "Inst occurs in data structures"); 1491 assert(I->second.getInst() != D && 1492 "Inst occurs in data structures"); 1493 } 1494 1495 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(), 1496 E = NonLocalPointerDeps.end(); I != E; ++I) { 1497 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key"); 1498 const NonLocalDepInfo &Val = I->second.NonLocalDeps; 1499 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end(); 1500 II != E; ++II) 1501 assert(II->getResult().getInst() != D && "Inst occurs as NLPD value"); 1502 } 1503 1504 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(), 1505 E = NonLocalDeps.end(); I != E; ++I) { 1506 assert(I->first != D && "Inst occurs in data structures"); 1507 const PerInstNLInfo &INLD = I->second; 1508 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(), 1509 EE = INLD.first.end(); II != EE; ++II) 1510 assert(II->getResult().getInst() != D && "Inst occurs in data structures"); 1511 } 1512 1513 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(), 1514 E = ReverseLocalDeps.end(); I != E; ++I) { 1515 assert(I->first != D && "Inst occurs in data structures"); 1516 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(), 1517 EE = I->second.end(); II != EE; ++II) 1518 assert(*II != D && "Inst occurs in data structures"); 1519 } 1520 1521 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(), 1522 E = ReverseNonLocalDeps.end(); 1523 I != E; ++I) { 1524 assert(I->first != D && "Inst occurs in data structures"); 1525 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(), 1526 EE = I->second.end(); II != EE; ++II) 1527 assert(*II != D && "Inst occurs in data structures"); 1528 } 1529 1530 for (ReverseNonLocalPtrDepTy::const_iterator 1531 I = ReverseNonLocalPtrDeps.begin(), 1532 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) { 1533 assert(I->first != D && "Inst occurs in rev NLPD map"); 1534 1535 for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(), 1536 E = I->second.end(); II != E; ++II) 1537 assert(*II != ValueIsLoadPair(D, false) && 1538 *II != ValueIsLoadPair(D, true) && 1539 "Inst occurs in ReverseNonLocalPtrDeps map"); 1540 } 1541 1542} 1543