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/Dominators.h" 23#include "llvm/Analysis/InstructionSimplify.h" 24#include "llvm/Analysis/MemoryBuiltins.h" 25#include "llvm/Analysis/PHITransAddr.h" 26#include "llvm/Analysis/ValueTracking.h" 27#include "llvm/IR/DataLayout.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/Support/Debug.h" 33#include "llvm/Support/PredIteratorCache.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(0) { 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 TD = getAnalysisIfAvailable<DataLayout>(); 91 DT = getAnalysisIfAvailable<DominatorTree>(); 92 if (!PredCache) 93 PredCache.reset(new PredIteratorCache()); 94 return false; 95} 96 97/// RemoveFromReverseMap - This is a helper function that removes Val from 98/// 'Inst's set in ReverseMap. If the set becomes empty, remove Inst's entry. 99template <typename KeyTy> 100static void RemoveFromReverseMap(DenseMap<Instruction*, 101 SmallPtrSet<KeyTy, 4> > &ReverseMap, 102 Instruction *Inst, KeyTy Val) { 103 typename DenseMap<Instruction*, SmallPtrSet<KeyTy, 4> >::iterator 104 InstIt = ReverseMap.find(Inst); 105 assert(InstIt != ReverseMap.end() && "Reverse map out of sync?"); 106 bool Found = InstIt->second.erase(Val); 107 assert(Found && "Invalid reverse map!"); (void)Found; 108 if (InstIt->second.empty()) 109 ReverseMap.erase(InstIt); 110} 111 112/// GetLocation - If the given instruction references a specific memory 113/// location, fill in Loc with the details, otherwise set Loc.Ptr to null. 114/// Return a ModRefInfo value describing the general behavior of the 115/// instruction. 116static 117AliasAnalysis::ModRefResult GetLocation(const Instruction *Inst, 118 AliasAnalysis::Location &Loc, 119 AliasAnalysis *AA) { 120 if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) { 121 if (LI->isUnordered()) { 122 Loc = AA->getLocation(LI); 123 return AliasAnalysis::Ref; 124 } 125 if (LI->getOrdering() == Monotonic) { 126 Loc = AA->getLocation(LI); 127 return AliasAnalysis::ModRef; 128 } 129 Loc = AliasAnalysis::Location(); 130 return AliasAnalysis::ModRef; 131 } 132 133 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 134 if (SI->isUnordered()) { 135 Loc = AA->getLocation(SI); 136 return AliasAnalysis::Mod; 137 } 138 if (SI->getOrdering() == Monotonic) { 139 Loc = AA->getLocation(SI); 140 return AliasAnalysis::ModRef; 141 } 142 Loc = AliasAnalysis::Location(); 143 return AliasAnalysis::ModRef; 144 } 145 146 if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) { 147 Loc = AA->getLocation(V); 148 return AliasAnalysis::ModRef; 149 } 150 151 if (const CallInst *CI = isFreeCall(Inst, AA->getTargetLibraryInfo())) { 152 // calls to free() deallocate the entire structure 153 Loc = AliasAnalysis::Location(CI->getArgOperand(0)); 154 return AliasAnalysis::Mod; 155 } 156 157 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) 158 switch (II->getIntrinsicID()) { 159 case Intrinsic::lifetime_start: 160 case Intrinsic::lifetime_end: 161 case Intrinsic::invariant_start: 162 Loc = AliasAnalysis::Location(II->getArgOperand(1), 163 cast<ConstantInt>(II->getArgOperand(0)) 164 ->getZExtValue(), 165 II->getMetadata(LLVMContext::MD_tbaa)); 166 // These intrinsics don't really modify the memory, but returning Mod 167 // will allow them to be handled conservatively. 168 return AliasAnalysis::Mod; 169 case Intrinsic::invariant_end: 170 Loc = AliasAnalysis::Location(II->getArgOperand(2), 171 cast<ConstantInt>(II->getArgOperand(1)) 172 ->getZExtValue(), 173 II->getMetadata(LLVMContext::MD_tbaa)); 174 // These intrinsics don't really modify the memory, but returning Mod 175 // will allow them to be handled conservatively. 176 return AliasAnalysis::Mod; 177 default: 178 break; 179 } 180 181 // Otherwise, just do the coarse-grained thing that always works. 182 if (Inst->mayWriteToMemory()) 183 return AliasAnalysis::ModRef; 184 if (Inst->mayReadFromMemory()) 185 return AliasAnalysis::Ref; 186 return AliasAnalysis::NoModRef; 187} 188 189/// getCallSiteDependencyFrom - Private helper for finding the local 190/// dependencies of a call site. 191MemDepResult MemoryDependenceAnalysis:: 192getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall, 193 BasicBlock::iterator ScanIt, BasicBlock *BB) { 194 unsigned Limit = BlockScanLimit; 195 196 // Walk backwards through the block, looking for dependencies 197 while (ScanIt != BB->begin()) { 198 // Limit the amount of scanning we do so we don't end up with quadratic 199 // running time on extreme testcases. 200 --Limit; 201 if (!Limit) 202 return MemDepResult::getUnknown(); 203 204 Instruction *Inst = --ScanIt; 205 206 // If this inst is a memory op, get the pointer it accessed 207 AliasAnalysis::Location Loc; 208 AliasAnalysis::ModRefResult MR = GetLocation(Inst, Loc, AA); 209 if (Loc.Ptr) { 210 // A simple instruction. 211 if (AA->getModRefInfo(CS, Loc) != AliasAnalysis::NoModRef) 212 return MemDepResult::getClobber(Inst); 213 continue; 214 } 215 216 if (CallSite InstCS = cast<Value>(Inst)) { 217 // Debug intrinsics don't cause dependences. 218 if (isa<DbgInfoIntrinsic>(Inst)) continue; 219 // If these two calls do not interfere, look past it. 220 switch (AA->getModRefInfo(CS, InstCS)) { 221 case AliasAnalysis::NoModRef: 222 // If the two calls are the same, return InstCS as a Def, so that 223 // CS can be found redundant and eliminated. 224 if (isReadOnlyCall && !(MR & AliasAnalysis::Mod) && 225 CS.getInstruction()->isIdenticalToWhenDefined(Inst)) 226 return MemDepResult::getDef(Inst); 227 228 // Otherwise if the two calls don't interact (e.g. InstCS is readnone) 229 // keep scanning. 230 continue; 231 default: 232 return MemDepResult::getClobber(Inst); 233 } 234 } 235 236 // If we could not obtain a pointer for the instruction and the instruction 237 // touches memory then assume that this is a dependency. 238 if (MR != AliasAnalysis::NoModRef) 239 return MemDepResult::getClobber(Inst); 240 } 241 242 // No dependence found. If this is the entry block of the function, it is 243 // unknown, otherwise it is non-local. 244 if (BB != &BB->getParent()->getEntryBlock()) 245 return MemDepResult::getNonLocal(); 246 return MemDepResult::getNonFuncLocal(); 247} 248 249/// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that 250/// would fully overlap MemLoc if done as a wider legal integer load. 251/// 252/// MemLocBase, MemLocOffset are lazily computed here the first time the 253/// base/offs of memloc is needed. 254static bool 255isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc, 256 const Value *&MemLocBase, 257 int64_t &MemLocOffs, 258 const LoadInst *LI, 259 const DataLayout *TD) { 260 // If we have no target data, we can't do this. 261 if (TD == 0) return false; 262 263 // If we haven't already computed the base/offset of MemLoc, do so now. 264 if (MemLocBase == 0) 265 MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, TD); 266 267 unsigned Size = MemoryDependenceAnalysis:: 268 getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size, 269 LI, *TD); 270 return Size != 0; 271} 272 273/// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that 274/// looks at a memory location for a load (specified by MemLocBase, Offs, 275/// and Size) and compares it against a load. If the specified load could 276/// be safely widened to a larger integer load that is 1) still efficient, 277/// 2) safe for the target, and 3) would provide the specified memory 278/// location value, then this function returns the size in bytes of the 279/// load width to use. If not, this returns zero. 280unsigned MemoryDependenceAnalysis:: 281getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs, 282 unsigned MemLocSize, const LoadInst *LI, 283 const DataLayout &TD) { 284 // We can only extend simple integer loads. 285 if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0; 286 287 // Load widening is hostile to ThreadSanitizer: it may cause false positives 288 // or make the reports more cryptic (access sizes are wrong). 289 if (LI->getParent()->getParent()->getAttributes(). 290 hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeThread)) 291 return 0; 292 293 // Get the base of this load. 294 int64_t LIOffs = 0; 295 const Value *LIBase = 296 GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, &TD); 297 298 // If the two pointers are not based on the same pointer, we can't tell that 299 // they are related. 300 if (LIBase != MemLocBase) return 0; 301 302 // Okay, the two values are based on the same pointer, but returned as 303 // no-alias. This happens when we have things like two byte loads at "P+1" 304 // and "P+3". Check to see if increasing the size of the "LI" load up to its 305 // alignment (or the largest native integer type) will allow us to load all 306 // the bits required by MemLoc. 307 308 // If MemLoc is before LI, then no widening of LI will help us out. 309 if (MemLocOffs < LIOffs) return 0; 310 311 // Get the alignment of the load in bytes. We assume that it is safe to load 312 // any legal integer up to this size without a problem. For example, if we're 313 // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can 314 // widen it up to an i32 load. If it is known 2-byte aligned, we can widen it 315 // to i16. 316 unsigned LoadAlign = LI->getAlignment(); 317 318 int64_t MemLocEnd = MemLocOffs+MemLocSize; 319 320 // If no amount of rounding up will let MemLoc fit into LI, then bail out. 321 if (LIOffs+LoadAlign < MemLocEnd) return 0; 322 323 // This is the size of the load to try. Start with the next larger power of 324 // two. 325 unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U; 326 NewLoadByteSize = NextPowerOf2(NewLoadByteSize); 327 328 while (1) { 329 // If this load size is bigger than our known alignment or would not fit 330 // into a native integer register, then we fail. 331 if (NewLoadByteSize > LoadAlign || 332 !TD.fitsInLegalInteger(NewLoadByteSize*8)) 333 return 0; 334 335 if (LIOffs+NewLoadByteSize > MemLocEnd && 336 LI->getParent()->getParent()->getAttributes(). 337 hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeAddress)) 338 // We will be reading past the location accessed by the original program. 339 // While this is safe in a regular build, Address Safety analysis tools 340 // may start reporting false warnings. So, don't do widening. 341 return 0; 342 343 // If a load of this width would include all of MemLoc, then we succeed. 344 if (LIOffs+NewLoadByteSize >= MemLocEnd) 345 return NewLoadByteSize; 346 347 NewLoadByteSize <<= 1; 348 } 349} 350 351/// getPointerDependencyFrom - Return the instruction on which a memory 352/// location depends. If isLoad is true, this routine ignores may-aliases with 353/// read-only operations. If isLoad is false, this routine ignores may-aliases 354/// with reads from read-only locations. If possible, pass the query 355/// instruction as well; this function may take advantage of the metadata 356/// annotated to the query instruction to refine the result. 357MemDepResult MemoryDependenceAnalysis:: 358getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad, 359 BasicBlock::iterator ScanIt, BasicBlock *BB, 360 Instruction *QueryInst) { 361 362 const Value *MemLocBase = 0; 363 int64_t MemLocOffset = 0; 364 unsigned Limit = BlockScanLimit; 365 bool isInvariantLoad = false; 366 if (isLoad && QueryInst) { 367 LoadInst *LI = dyn_cast<LoadInst>(QueryInst); 368 if (LI && LI->getMetadata(LLVMContext::MD_invariant_load) != 0) 369 isInvariantLoad = true; 370 } 371 372 // Walk backwards through the basic block, looking for dependencies. 373 while (ScanIt != BB->begin()) { 374 Instruction *Inst = --ScanIt; 375 376 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) 377 // Debug intrinsics don't (and can't) cause dependencies. 378 if (isa<DbgInfoIntrinsic>(II)) continue; 379 380 // Limit the amount of scanning we do so we don't end up with quadratic 381 // running time on extreme testcases. 382 --Limit; 383 if (!Limit) 384 return MemDepResult::getUnknown(); 385 386 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { 387 // If we reach a lifetime begin or end marker, then the query ends here 388 // because the value is undefined. 389 if (II->getIntrinsicID() == Intrinsic::lifetime_start) { 390 // FIXME: This only considers queries directly on the invariant-tagged 391 // pointer, not on query pointers that are indexed off of them. It'd 392 // be nice to handle that at some point (the right approach is to use 393 // GetPointerBaseWithConstantOffset). 394 if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)), 395 MemLoc)) 396 return MemDepResult::getDef(II); 397 continue; 398 } 399 } 400 401 // Values depend on loads if the pointers are must aliased. This means that 402 // a load depends on another must aliased load from the same value. 403 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) { 404 // Atomic loads have complications involved. 405 // FIXME: This is overly conservative. 406 if (!LI->isUnordered()) 407 return MemDepResult::getClobber(LI); 408 409 AliasAnalysis::Location LoadLoc = AA->getLocation(LI); 410 411 // If we found a pointer, check if it could be the same as our pointer. 412 AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc); 413 414 if (isLoad) { 415 if (R == AliasAnalysis::NoAlias) { 416 // If this is an over-aligned integer load (for example, 417 // "load i8* %P, align 4") see if it would obviously overlap with the 418 // queried location if widened to a larger load (e.g. if the queried 419 // location is 1 byte at P+1). If so, return it as a load/load 420 // clobber result, allowing the client to decide to widen the load if 421 // it wants to. 422 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) 423 if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() && 424 isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase, 425 MemLocOffset, LI, TD)) 426 return MemDepResult::getClobber(Inst); 427 428 continue; 429 } 430 431 // Must aliased loads are defs of each other. 432 if (R == AliasAnalysis::MustAlias) 433 return MemDepResult::getDef(Inst); 434 435#if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads 436 // in terms of clobbering loads, but since it does this by looking 437 // at the clobbering load directly, it doesn't know about any 438 // phi translation that may have happened along the way. 439 440 // If we have a partial alias, then return this as a clobber for the 441 // client to handle. 442 if (R == AliasAnalysis::PartialAlias) 443 return MemDepResult::getClobber(Inst); 444#endif 445 446 // Random may-alias loads don't depend on each other without a 447 // dependence. 448 continue; 449 } 450 451 // Stores don't depend on other no-aliased accesses. 452 if (R == AliasAnalysis::NoAlias) 453 continue; 454 455 // Stores don't alias loads from read-only memory. 456 if (AA->pointsToConstantMemory(LoadLoc)) 457 continue; 458 459 // Stores depend on may/must aliased loads. 460 return MemDepResult::getDef(Inst); 461 } 462 463 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 464 // Atomic stores have complications involved. 465 // FIXME: This is overly conservative. 466 if (!SI->isUnordered()) 467 return MemDepResult::getClobber(SI); 468 469 // If alias analysis can tell that this store is guaranteed to not modify 470 // the query pointer, ignore it. Use getModRefInfo to handle cases where 471 // the query pointer points to constant memory etc. 472 if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef) 473 continue; 474 475 // Ok, this store might clobber the query pointer. Check to see if it is 476 // a must alias: in this case, we want to return this as a def. 477 AliasAnalysis::Location StoreLoc = AA->getLocation(SI); 478 479 // If we found a pointer, check if it could be the same as our pointer. 480 AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc); 481 482 if (R == AliasAnalysis::NoAlias) 483 continue; 484 if (R == AliasAnalysis::MustAlias) 485 return MemDepResult::getDef(Inst); 486 if (isInvariantLoad) 487 continue; 488 return MemDepResult::getClobber(Inst); 489 } 490 491 // If this is an allocation, and if we know that the accessed pointer is to 492 // the allocation, return Def. This means that there is no dependence and 493 // the access can be optimized based on that. For example, a load could 494 // turn into undef. 495 // Note: Only determine this to be a malloc if Inst is the malloc call, not 496 // a subsequent bitcast of the malloc call result. There can be stores to 497 // the malloced memory between the malloc call and its bitcast uses, and we 498 // need to continue scanning until the malloc call. 499 const TargetLibraryInfo *TLI = AA->getTargetLibraryInfo(); 500 if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, TLI)) { 501 const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, TD); 502 503 if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr)) 504 return MemDepResult::getDef(Inst); 505 // Be conservative if the accessed pointer may alias the allocation. 506 if (AA->alias(Inst, AccessPtr) != AliasAnalysis::NoAlias) 507 return MemDepResult::getClobber(Inst); 508 // If the allocation is not aliased and does not read memory (like 509 // strdup), it is safe to ignore. 510 if (isa<AllocaInst>(Inst) || 511 isMallocLikeFn(Inst, TLI) || isCallocLikeFn(Inst, TLI)) 512 continue; 513 } 514 515 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer. 516 AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc); 517 // If necessary, perform additional analysis. 518 if (MR == AliasAnalysis::ModRef) 519 MR = AA->callCapturesBefore(Inst, MemLoc, DT); 520 switch (MR) { 521 case AliasAnalysis::NoModRef: 522 // If the call has no effect on the queried pointer, just ignore it. 523 continue; 524 case AliasAnalysis::Mod: 525 return MemDepResult::getClobber(Inst); 526 case AliasAnalysis::Ref: 527 // If the call is known to never store to the pointer, and if this is a 528 // load query, we can safely ignore it (scan past it). 529 if (isLoad) 530 continue; 531 default: 532 // Otherwise, there is a potential dependence. Return a clobber. 533 return MemDepResult::getClobber(Inst); 534 } 535 } 536 537 // No dependence found. If this is the entry block of the function, it is 538 // unknown, otherwise it is non-local. 539 if (BB != &BB->getParent()->getEntryBlock()) 540 return MemDepResult::getNonLocal(); 541 return MemDepResult::getNonFuncLocal(); 542} 543 544/// getDependency - Return the instruction on which a memory operation 545/// depends. 546MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) { 547 Instruction *ScanPos = QueryInst; 548 549 // Check for a cached result 550 MemDepResult &LocalCache = LocalDeps[QueryInst]; 551 552 // If the cached entry is non-dirty, just return it. Note that this depends 553 // on MemDepResult's default constructing to 'dirty'. 554 if (!LocalCache.isDirty()) 555 return LocalCache; 556 557 // Otherwise, if we have a dirty entry, we know we can start the scan at that 558 // instruction, which may save us some work. 559 if (Instruction *Inst = LocalCache.getInst()) { 560 ScanPos = Inst; 561 562 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst); 563 } 564 565 BasicBlock *QueryParent = QueryInst->getParent(); 566 567 // Do the scan. 568 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) { 569 // No dependence found. If this is the entry block of the function, it is 570 // unknown, otherwise it is non-local. 571 if (QueryParent != &QueryParent->getParent()->getEntryBlock()) 572 LocalCache = MemDepResult::getNonLocal(); 573 else 574 LocalCache = MemDepResult::getNonFuncLocal(); 575 } else { 576 AliasAnalysis::Location MemLoc; 577 AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA); 578 if (MemLoc.Ptr) { 579 // If we can do a pointer scan, make it happen. 580 bool isLoad = !(MR & AliasAnalysis::Mod); 581 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst)) 582 isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start; 583 584 LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos, 585 QueryParent, QueryInst); 586 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) { 587 CallSite QueryCS(QueryInst); 588 bool isReadOnly = AA->onlyReadsMemory(QueryCS); 589 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos, 590 QueryParent); 591 } else 592 // Non-memory instruction. 593 LocalCache = MemDepResult::getUnknown(); 594 } 595 596 // Remember the result! 597 if (Instruction *I = LocalCache.getInst()) 598 ReverseLocalDeps[I].insert(QueryInst); 599 600 return LocalCache; 601} 602 603#ifndef NDEBUG 604/// AssertSorted - This method is used when -debug is specified to verify that 605/// cache arrays are properly kept sorted. 606static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache, 607 int Count = -1) { 608 if (Count == -1) Count = Cache.size(); 609 if (Count == 0) return; 610 611 for (unsigned i = 1; i != unsigned(Count); ++i) 612 assert(!(Cache[i] < Cache[i-1]) && "Cache isn't sorted!"); 613} 614#endif 615 616/// getNonLocalCallDependency - Perform a full dependency query for the 617/// specified call, returning the set of blocks that the value is 618/// potentially live across. The returned set of results will include a 619/// "NonLocal" result for all blocks where the value is live across. 620/// 621/// This method assumes the instruction returns a "NonLocal" dependency 622/// within its own block. 623/// 624/// This returns a reference to an internal data structure that may be 625/// invalidated on the next non-local query or when an instruction is 626/// removed. Clients must copy this data if they want it around longer than 627/// that. 628const MemoryDependenceAnalysis::NonLocalDepInfo & 629MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) { 630 assert(getDependency(QueryCS.getInstruction()).isNonLocal() && 631 "getNonLocalCallDependency should only be used on calls with non-local deps!"); 632 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()]; 633 NonLocalDepInfo &Cache = CacheP.first; 634 635 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In 636 /// the cached case, this can happen due to instructions being deleted etc. In 637 /// the uncached case, this starts out as the set of predecessors we care 638 /// about. 639 SmallVector<BasicBlock*, 32> DirtyBlocks; 640 641 if (!Cache.empty()) { 642 // Okay, we have a cache entry. If we know it is not dirty, just return it 643 // with no computation. 644 if (!CacheP.second) { 645 ++NumCacheNonLocal; 646 return Cache; 647 } 648 649 // If we already have a partially computed set of results, scan them to 650 // determine what is dirty, seeding our initial DirtyBlocks worklist. 651 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end(); 652 I != E; ++I) 653 if (I->getResult().isDirty()) 654 DirtyBlocks.push_back(I->getBB()); 655 656 // Sort the cache so that we can do fast binary search lookups below. 657 std::sort(Cache.begin(), Cache.end()); 658 659 ++NumCacheDirtyNonLocal; 660 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: " 661 // << Cache.size() << " cached: " << *QueryInst; 662 } else { 663 // Seed DirtyBlocks with each of the preds of QueryInst's block. 664 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent(); 665 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI) 666 DirtyBlocks.push_back(*PI); 667 ++NumUncacheNonLocal; 668 } 669 670 // isReadonlyCall - If this is a read-only call, we can be more aggressive. 671 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS); 672 673 SmallPtrSet<BasicBlock*, 64> Visited; 674 675 unsigned NumSortedEntries = Cache.size(); 676 DEBUG(AssertSorted(Cache)); 677 678 // Iterate while we still have blocks to update. 679 while (!DirtyBlocks.empty()) { 680 BasicBlock *DirtyBB = DirtyBlocks.back(); 681 DirtyBlocks.pop_back(); 682 683 // Already processed this block? 684 if (!Visited.insert(DirtyBB)) 685 continue; 686 687 // Do a binary search to see if we already have an entry for this block in 688 // the cache set. If so, find it. 689 DEBUG(AssertSorted(Cache, NumSortedEntries)); 690 NonLocalDepInfo::iterator Entry = 691 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries, 692 NonLocalDepEntry(DirtyBB)); 693 if (Entry != Cache.begin() && prior(Entry)->getBB() == DirtyBB) 694 --Entry; 695 696 NonLocalDepEntry *ExistingResult = 0; 697 if (Entry != Cache.begin()+NumSortedEntries && 698 Entry->getBB() == DirtyBB) { 699 // If we already have an entry, and if it isn't already dirty, the block 700 // is done. 701 if (!Entry->getResult().isDirty()) 702 continue; 703 704 // Otherwise, remember this slot so we can update the value. 705 ExistingResult = &*Entry; 706 } 707 708 // If the dirty entry has a pointer, start scanning from it so we don't have 709 // to rescan the entire block. 710 BasicBlock::iterator ScanPos = DirtyBB->end(); 711 if (ExistingResult) { 712 if (Instruction *Inst = ExistingResult->getResult().getInst()) { 713 ScanPos = Inst; 714 // We're removing QueryInst's use of Inst. 715 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, 716 QueryCS.getInstruction()); 717 } 718 } 719 720 // Find out if this block has a local dependency for QueryInst. 721 MemDepResult Dep; 722 723 if (ScanPos != DirtyBB->begin()) { 724 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB); 725 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) { 726 // No dependence found. If this is the entry block of the function, it is 727 // a clobber, otherwise it is unknown. 728 Dep = MemDepResult::getNonLocal(); 729 } else { 730 Dep = MemDepResult::getNonFuncLocal(); 731 } 732 733 // If we had a dirty entry for the block, update it. Otherwise, just add 734 // a new entry. 735 if (ExistingResult) 736 ExistingResult->setResult(Dep); 737 else 738 Cache.push_back(NonLocalDepEntry(DirtyBB, Dep)); 739 740 // If the block has a dependency (i.e. it isn't completely transparent to 741 // the value), remember the association! 742 if (!Dep.isNonLocal()) { 743 // Keep the ReverseNonLocalDeps map up to date so we can efficiently 744 // update this when we remove instructions. 745 if (Instruction *Inst = Dep.getInst()) 746 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction()); 747 } else { 748 749 // If the block *is* completely transparent to the load, we need to check 750 // the predecessors of this block. Add them to our worklist. 751 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI) 752 DirtyBlocks.push_back(*PI); 753 } 754 } 755 756 return Cache; 757} 758 759/// getNonLocalPointerDependency - Perform a full dependency query for an 760/// access to the specified (non-volatile) memory location, returning the 761/// set of instructions that either define or clobber the value. 762/// 763/// This method assumes the pointer has a "NonLocal" dependency within its 764/// own block. 765/// 766void MemoryDependenceAnalysis:: 767getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad, 768 BasicBlock *FromBB, 769 SmallVectorImpl<NonLocalDepResult> &Result) { 770 assert(Loc.Ptr->getType()->isPointerTy() && 771 "Can't get pointer deps of a non-pointer!"); 772 Result.clear(); 773 774 PHITransAddr Address(const_cast<Value *>(Loc.Ptr), TD); 775 776 // This is the set of blocks we've inspected, and the pointer we consider in 777 // each block. Because of critical edges, we currently bail out if querying 778 // a block with multiple different pointers. This can happen during PHI 779 // translation. 780 DenseMap<BasicBlock*, Value*> Visited; 781 if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB, 782 Result, Visited, true)) 783 return; 784 Result.clear(); 785 Result.push_back(NonLocalDepResult(FromBB, 786 MemDepResult::getUnknown(), 787 const_cast<Value *>(Loc.Ptr))); 788} 789 790/// GetNonLocalInfoForBlock - Compute the memdep value for BB with 791/// Pointer/PointeeSize using either cached information in Cache or by doing a 792/// lookup (which may use dirty cache info if available). If we do a lookup, 793/// add the result to the cache. 794MemDepResult MemoryDependenceAnalysis:: 795GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc, 796 bool isLoad, BasicBlock *BB, 797 NonLocalDepInfo *Cache, unsigned NumSortedEntries) { 798 799 // Do a binary search to see if we already have an entry for this block in 800 // the cache set. If so, find it. 801 NonLocalDepInfo::iterator Entry = 802 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries, 803 NonLocalDepEntry(BB)); 804 if (Entry != Cache->begin() && (Entry-1)->getBB() == BB) 805 --Entry; 806 807 NonLocalDepEntry *ExistingResult = 0; 808 if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB) 809 ExistingResult = &*Entry; 810 811 // If we have a cached entry, and it is non-dirty, use it as the value for 812 // this dependency. 813 if (ExistingResult && !ExistingResult->getResult().isDirty()) { 814 ++NumCacheNonLocalPtr; 815 return ExistingResult->getResult(); 816 } 817 818 // Otherwise, we have to scan for the value. If we have a dirty cache 819 // entry, start scanning from its position, otherwise we scan from the end 820 // of the block. 821 BasicBlock::iterator ScanPos = BB->end(); 822 if (ExistingResult && ExistingResult->getResult().getInst()) { 823 assert(ExistingResult->getResult().getInst()->getParent() == BB && 824 "Instruction invalidated?"); 825 ++NumCacheDirtyNonLocalPtr; 826 ScanPos = ExistingResult->getResult().getInst(); 827 828 // Eliminating the dirty entry from 'Cache', so update the reverse info. 829 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad); 830 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey); 831 } else { 832 ++NumUncacheNonLocalPtr; 833 } 834 835 // Scan the block for the dependency. 836 MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB); 837 838 // If we had a dirty entry for the block, update it. Otherwise, just add 839 // a new entry. 840 if (ExistingResult) 841 ExistingResult->setResult(Dep); 842 else 843 Cache->push_back(NonLocalDepEntry(BB, Dep)); 844 845 // If the block has a dependency (i.e. it isn't completely transparent to 846 // the value), remember the reverse association because we just added it 847 // to Cache! 848 if (!Dep.isDef() && !Dep.isClobber()) 849 return Dep; 850 851 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently 852 // update MemDep when we remove instructions. 853 Instruction *Inst = Dep.getInst(); 854 assert(Inst && "Didn't depend on anything?"); 855 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad); 856 ReverseNonLocalPtrDeps[Inst].insert(CacheKey); 857 return Dep; 858} 859 860/// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain 861/// number of elements in the array that are already properly ordered. This is 862/// optimized for the case when only a few entries are added. 863static void 864SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache, 865 unsigned NumSortedEntries) { 866 switch (Cache.size() - NumSortedEntries) { 867 case 0: 868 // done, no new entries. 869 break; 870 case 2: { 871 // Two new entries, insert the last one into place. 872 NonLocalDepEntry Val = Cache.back(); 873 Cache.pop_back(); 874 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry = 875 std::upper_bound(Cache.begin(), Cache.end()-1, Val); 876 Cache.insert(Entry, Val); 877 // FALL THROUGH. 878 } 879 case 1: 880 // One new entry, Just insert the new value at the appropriate position. 881 if (Cache.size() != 1) { 882 NonLocalDepEntry Val = Cache.back(); 883 Cache.pop_back(); 884 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry = 885 std::upper_bound(Cache.begin(), Cache.end(), Val); 886 Cache.insert(Entry, Val); 887 } 888 break; 889 default: 890 // Added many values, do a full scale sort. 891 std::sort(Cache.begin(), Cache.end()); 892 break; 893 } 894} 895 896/// getNonLocalPointerDepFromBB - Perform a dependency query based on 897/// pointer/pointeesize starting at the end of StartBB. Add any clobber/def 898/// results to the results vector and keep track of which blocks are visited in 899/// 'Visited'. 900/// 901/// This has special behavior for the first block queries (when SkipFirstBlock 902/// is true). In this special case, it ignores the contents of the specified 903/// block and starts returning dependence info for its predecessors. 904/// 905/// This function returns false on success, or true to indicate that it could 906/// not compute dependence information for some reason. This should be treated 907/// as a clobber dependence on the first instruction in the predecessor block. 908bool MemoryDependenceAnalysis:: 909getNonLocalPointerDepFromBB(const PHITransAddr &Pointer, 910 const AliasAnalysis::Location &Loc, 911 bool isLoad, BasicBlock *StartBB, 912 SmallVectorImpl<NonLocalDepResult> &Result, 913 DenseMap<BasicBlock*, Value*> &Visited, 914 bool SkipFirstBlock) { 915 // Look up the cached info for Pointer. 916 ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad); 917 918 // Set up a temporary NLPI value. If the map doesn't yet have an entry for 919 // CacheKey, this value will be inserted as the associated value. Otherwise, 920 // it'll be ignored, and we'll have to check to see if the cached size and 921 // tbaa tag are consistent with the current query. 922 NonLocalPointerInfo InitialNLPI; 923 InitialNLPI.Size = Loc.Size; 924 InitialNLPI.TBAATag = Loc.TBAATag; 925 926 // Get the NLPI for CacheKey, inserting one into the map if it doesn't 927 // already have one. 928 std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair = 929 NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI)); 930 NonLocalPointerInfo *CacheInfo = &Pair.first->second; 931 932 // If we already have a cache entry for this CacheKey, we may need to do some 933 // work to reconcile the cache entry and the current query. 934 if (!Pair.second) { 935 if (CacheInfo->Size < Loc.Size) { 936 // The query's Size is greater than the cached one. Throw out the 937 // cached data and proceed with the query at the greater size. 938 CacheInfo->Pair = BBSkipFirstBlockPair(); 939 CacheInfo->Size = Loc.Size; 940 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(), 941 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI) 942 if (Instruction *Inst = DI->getResult().getInst()) 943 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey); 944 CacheInfo->NonLocalDeps.clear(); 945 } else if (CacheInfo->Size > Loc.Size) { 946 // This query's Size is less than the cached one. Conservatively restart 947 // the query using the greater size. 948 return getNonLocalPointerDepFromBB(Pointer, 949 Loc.getWithNewSize(CacheInfo->Size), 950 isLoad, StartBB, Result, Visited, 951 SkipFirstBlock); 952 } 953 954 // If the query's TBAATag is inconsistent with the cached one, 955 // conservatively throw out the cached data and restart the query with 956 // no tag if needed. 957 if (CacheInfo->TBAATag != Loc.TBAATag) { 958 if (CacheInfo->TBAATag) { 959 CacheInfo->Pair = BBSkipFirstBlockPair(); 960 CacheInfo->TBAATag = 0; 961 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(), 962 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI) 963 if (Instruction *Inst = DI->getResult().getInst()) 964 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey); 965 CacheInfo->NonLocalDeps.clear(); 966 } 967 if (Loc.TBAATag) 968 return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(), 969 isLoad, StartBB, Result, Visited, 970 SkipFirstBlock); 971 } 972 } 973 974 NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps; 975 976 // If we have valid cached information for exactly the block we are 977 // investigating, just return it with no recomputation. 978 if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) { 979 // We have a fully cached result for this query then we can just return the 980 // cached results and populate the visited set. However, we have to verify 981 // that we don't already have conflicting results for these blocks. Check 982 // to ensure that if a block in the results set is in the visited set that 983 // it was for the same pointer query. 984 if (!Visited.empty()) { 985 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end(); 986 I != E; ++I) { 987 DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->getBB()); 988 if (VI == Visited.end() || VI->second == Pointer.getAddr()) 989 continue; 990 991 // We have a pointer mismatch in a block. Just return clobber, saying 992 // that something was clobbered in this result. We could also do a 993 // non-fully cached query, but there is little point in doing this. 994 return true; 995 } 996 } 997 998 Value *Addr = Pointer.getAddr(); 999 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end(); 1000 I != E; ++I) { 1001 Visited.insert(std::make_pair(I->getBB(), Addr)); 1002 if (I->getResult().isNonLocal()) { 1003 continue; 1004 } 1005 1006 if (!DT) { 1007 Result.push_back(NonLocalDepResult(I->getBB(), 1008 MemDepResult::getUnknown(), 1009 Addr)); 1010 } else if (DT->isReachableFromEntry(I->getBB())) { 1011 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr)); 1012 } 1013 } 1014 ++NumCacheCompleteNonLocalPtr; 1015 return false; 1016 } 1017 1018 // Otherwise, either this is a new block, a block with an invalid cache 1019 // pointer or one that we're about to invalidate by putting more info into it 1020 // than its valid cache info. If empty, the result will be valid cache info, 1021 // otherwise it isn't. 1022 if (Cache->empty()) 1023 CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock); 1024 else 1025 CacheInfo->Pair = BBSkipFirstBlockPair(); 1026 1027 SmallVector<BasicBlock*, 32> Worklist; 1028 Worklist.push_back(StartBB); 1029 1030 // PredList used inside loop. 1031 SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList; 1032 1033 // Keep track of the entries that we know are sorted. Previously cached 1034 // entries will all be sorted. The entries we add we only sort on demand (we 1035 // don't insert every element into its sorted position). We know that we 1036 // won't get any reuse from currently inserted values, because we don't 1037 // revisit blocks after we insert info for them. 1038 unsigned NumSortedEntries = Cache->size(); 1039 DEBUG(AssertSorted(*Cache)); 1040 1041 while (!Worklist.empty()) { 1042 BasicBlock *BB = Worklist.pop_back_val(); 1043 1044 // Skip the first block if we have it. 1045 if (!SkipFirstBlock) { 1046 // Analyze the dependency of *Pointer in FromBB. See if we already have 1047 // been here. 1048 assert(Visited.count(BB) && "Should check 'visited' before adding to WL"); 1049 1050 // Get the dependency info for Pointer in BB. If we have cached 1051 // information, we will use it, otherwise we compute it. 1052 DEBUG(AssertSorted(*Cache, NumSortedEntries)); 1053 MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache, 1054 NumSortedEntries); 1055 1056 // If we got a Def or Clobber, add this to the list of results. 1057 if (!Dep.isNonLocal()) { 1058 if (!DT) { 1059 Result.push_back(NonLocalDepResult(BB, 1060 MemDepResult::getUnknown(), 1061 Pointer.getAddr())); 1062 continue; 1063 } else if (DT->isReachableFromEntry(BB)) { 1064 Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr())); 1065 continue; 1066 } 1067 } 1068 } 1069 1070 // If 'Pointer' is an instruction defined in this block, then we need to do 1071 // phi translation to change it into a value live in the predecessor block. 1072 // If not, we just add the predecessors to the worklist and scan them with 1073 // the same Pointer. 1074 if (!Pointer.NeedsPHITranslationFromBlock(BB)) { 1075 SkipFirstBlock = false; 1076 SmallVector<BasicBlock*, 16> NewBlocks; 1077 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { 1078 // Verify that we haven't looked at this block yet. 1079 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool> 1080 InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr())); 1081 if (InsertRes.second) { 1082 // First time we've looked at *PI. 1083 NewBlocks.push_back(*PI); 1084 continue; 1085 } 1086 1087 // If we have seen this block before, but it was with a different 1088 // pointer then we have a phi translation failure and we have to treat 1089 // this as a clobber. 1090 if (InsertRes.first->second != Pointer.getAddr()) { 1091 // Make sure to clean up the Visited map before continuing on to 1092 // PredTranslationFailure. 1093 for (unsigned i = 0; i < NewBlocks.size(); i++) 1094 Visited.erase(NewBlocks[i]); 1095 goto PredTranslationFailure; 1096 } 1097 } 1098 Worklist.append(NewBlocks.begin(), NewBlocks.end()); 1099 continue; 1100 } 1101 1102 // We do need to do phi translation, if we know ahead of time we can't phi 1103 // translate this value, don't even try. 1104 if (!Pointer.IsPotentiallyPHITranslatable()) 1105 goto PredTranslationFailure; 1106 1107 // We may have added values to the cache list before this PHI translation. 1108 // If so, we haven't done anything to ensure that the cache remains sorted. 1109 // Sort it now (if needed) so that recursive invocations of 1110 // getNonLocalPointerDepFromBB and other routines that could reuse the cache 1111 // value will only see properly sorted cache arrays. 1112 if (Cache && NumSortedEntries != Cache->size()) { 1113 SortNonLocalDepInfoCache(*Cache, NumSortedEntries); 1114 NumSortedEntries = Cache->size(); 1115 } 1116 Cache = 0; 1117 1118 PredList.clear(); 1119 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) { 1120 BasicBlock *Pred = *PI; 1121 PredList.push_back(std::make_pair(Pred, Pointer)); 1122 1123 // Get the PHI translated pointer in this predecessor. This can fail if 1124 // not translatable, in which case the getAddr() returns null. 1125 PHITransAddr &PredPointer = PredList.back().second; 1126 PredPointer.PHITranslateValue(BB, Pred, 0); 1127 1128 Value *PredPtrVal = PredPointer.getAddr(); 1129 1130 // Check to see if we have already visited this pred block with another 1131 // pointer. If so, we can't do this lookup. This failure can occur 1132 // with PHI translation when a critical edge exists and the PHI node in 1133 // the successor translates to a pointer value different than the 1134 // pointer the block was first analyzed with. 1135 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool> 1136 InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal)); 1137 1138 if (!InsertRes.second) { 1139 // We found the pred; take it off the list of preds to visit. 1140 PredList.pop_back(); 1141 1142 // If the predecessor was visited with PredPtr, then we already did 1143 // the analysis and can ignore it. 1144 if (InsertRes.first->second == PredPtrVal) 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 1151 // Make sure to clean up the Visited map before continuing on to 1152 // PredTranslationFailure. 1153 for (unsigned i = 0, n = PredList.size(); i < n; ++i) 1154 Visited.erase(PredList[i].first); 1155 1156 goto PredTranslationFailure; 1157 } 1158 } 1159 1160 // Actually process results here; this need to be a separate loop to avoid 1161 // calling getNonLocalPointerDepFromBB for blocks we don't want to return 1162 // any results for. (getNonLocalPointerDepFromBB will modify our 1163 // datastructures in ways the code after the PredTranslationFailure label 1164 // doesn't expect.) 1165 for (unsigned i = 0, n = PredList.size(); i < n; ++i) { 1166 BasicBlock *Pred = PredList[i].first; 1167 PHITransAddr &PredPointer = PredList[i].second; 1168 Value *PredPtrVal = PredPointer.getAddr(); 1169 1170 bool CanTranslate = true; 1171 // If PHI translation was unable to find an available pointer in this 1172 // predecessor, then we have to assume that the pointer is clobbered in 1173 // that predecessor. We can still do PRE of the load, which would insert 1174 // a computation of the pointer in this predecessor. 1175 if (PredPtrVal == 0) 1176 CanTranslate = false; 1177 1178 // FIXME: it is entirely possible that PHI translating will end up with 1179 // the same value. Consider PHI translating something like: 1180 // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need* 1181 // to recurse here, pedantically speaking. 1182 1183 // If getNonLocalPointerDepFromBB fails here, that means the cached 1184 // result conflicted with the Visited list; we have to conservatively 1185 // assume it is unknown, but this also does not block PRE of the load. 1186 if (!CanTranslate || 1187 getNonLocalPointerDepFromBB(PredPointer, 1188 Loc.getWithNewPtr(PredPtrVal), 1189 isLoad, Pred, 1190 Result, Visited)) { 1191 // Add the entry to the Result list. 1192 NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal); 1193 Result.push_back(Entry); 1194 1195 // Since we had a phi translation failure, the cache for CacheKey won't 1196 // include all of the entries that we need to immediately satisfy future 1197 // queries. Mark this in NonLocalPointerDeps by setting the 1198 // BBSkipFirstBlockPair pointer to null. This requires reuse of the 1199 // cached value to do more work but not miss the phi trans failure. 1200 NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey]; 1201 NLPI.Pair = BBSkipFirstBlockPair(); 1202 continue; 1203 } 1204 } 1205 1206 // Refresh the CacheInfo/Cache pointer so that it isn't invalidated. 1207 CacheInfo = &NonLocalPointerDeps[CacheKey]; 1208 Cache = &CacheInfo->NonLocalDeps; 1209 NumSortedEntries = Cache->size(); 1210 1211 // Since we did phi translation, the "Cache" set won't contain all of the 1212 // results for the query. This is ok (we can still use it to accelerate 1213 // specific block queries) but we can't do the fastpath "return all 1214 // results from the set" Clear out the indicator for this. 1215 CacheInfo->Pair = BBSkipFirstBlockPair(); 1216 SkipFirstBlock = false; 1217 continue; 1218 1219 PredTranslationFailure: 1220 // The following code is "failure"; we can't produce a sane translation 1221 // for the given block. It assumes that we haven't modified any of 1222 // our datastructures while processing the current block. 1223 1224 if (Cache == 0) { 1225 // Refresh the CacheInfo/Cache pointer if it got invalidated. 1226 CacheInfo = &NonLocalPointerDeps[CacheKey]; 1227 Cache = &CacheInfo->NonLocalDeps; 1228 NumSortedEntries = Cache->size(); 1229 } 1230 1231 // Since we failed phi translation, the "Cache" set won't contain all of the 1232 // results for the query. This is ok (we can still use it to accelerate 1233 // specific block queries) but we can't do the fastpath "return all 1234 // results from the set". Clear out the indicator for this. 1235 CacheInfo->Pair = BBSkipFirstBlockPair(); 1236 1237 // If *nothing* works, mark the pointer as unknown. 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->getBB() != BB) 1248 continue; 1249 1250 assert(I->getResult().isNonLocal() && 1251 "Should only be here with transparent block"); 1252 I->setResult(MemDepResult::getUnknown()); 1253 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), 1254 Pointer.getAddr())); 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.NonLocalDeps; 1276 1277 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) { 1278 Instruction *Target = PInfo[i].getResult().getInst(); 1279 if (Target == 0) continue; // Ignore non-local dep results. 1280 assert(Target->getParent() == PInfo[i].getBB()); 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 (!Ptr->getType()->isPointerTy()) 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/// invalidateCachedPredecessors - Clear the PredIteratorCache info. 1307/// This needs to be done when the CFG changes, e.g., due to splitting 1308/// critical edges. 1309void MemoryDependenceAnalysis::invalidateCachedPredecessors() { 1310 PredCache->clear(); 1311} 1312 1313/// removeInstruction - Remove an instruction from the dependence analysis, 1314/// updating the dependence of instructions that previously depended on it. 1315/// This method attempts to keep the cache coherent using the reverse map. 1316void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) { 1317 // Walk through the Non-local dependencies, removing this one as the value 1318 // for any cached queries. 1319 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst); 1320 if (NLDI != NonLocalDeps.end()) { 1321 NonLocalDepInfo &BlockMap = NLDI->second.first; 1322 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end(); 1323 DI != DE; ++DI) 1324 if (Instruction *Inst = DI->getResult().getInst()) 1325 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst); 1326 NonLocalDeps.erase(NLDI); 1327 } 1328 1329 // If we have a cached local dependence query for this instruction, remove it. 1330 // 1331 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst); 1332 if (LocalDepEntry != LocalDeps.end()) { 1333 // Remove us from DepInst's reverse set now that the local dep info is gone. 1334 if (Instruction *Inst = LocalDepEntry->second.getInst()) 1335 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst); 1336 1337 // Remove this local dependency info. 1338 LocalDeps.erase(LocalDepEntry); 1339 } 1340 1341 // If we have any cached pointer dependencies on this instruction, remove 1342 // them. If the instruction has non-pointer type, then it can't be a pointer 1343 // base. 1344 1345 // Remove it from both the load info and the store info. The instruction 1346 // can't be in either of these maps if it is non-pointer. 1347 if (RemInst->getType()->isPointerTy()) { 1348 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false)); 1349 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true)); 1350 } 1351 1352 // Loop over all of the things that depend on the instruction we're removing. 1353 // 1354 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd; 1355 1356 // If we find RemInst as a clobber or Def in any of the maps for other values, 1357 // we need to replace its entry with a dirty version of the instruction after 1358 // it. If RemInst is a terminator, we use a null dirty value. 1359 // 1360 // Using a dirty version of the instruction after RemInst saves having to scan 1361 // the entire block to get to this point. 1362 MemDepResult NewDirtyVal; 1363 if (!RemInst->isTerminator()) 1364 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst)); 1365 1366 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst); 1367 if (ReverseDepIt != ReverseLocalDeps.end()) { 1368 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second; 1369 // RemInst can't be the terminator if it has local stuff depending on it. 1370 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) && 1371 "Nothing can locally depend on a terminator"); 1372 1373 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(), 1374 E = ReverseDeps.end(); I != E; ++I) { 1375 Instruction *InstDependingOnRemInst = *I; 1376 assert(InstDependingOnRemInst != RemInst && 1377 "Already removed our local dep info"); 1378 1379 LocalDeps[InstDependingOnRemInst] = NewDirtyVal; 1380 1381 // Make sure to remember that new things depend on NewDepInst. 1382 assert(NewDirtyVal.getInst() && "There is no way something else can have " 1383 "a local dep on this if it is a terminator!"); 1384 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(), 1385 InstDependingOnRemInst)); 1386 } 1387 1388 ReverseLocalDeps.erase(ReverseDepIt); 1389 1390 // Add new reverse deps after scanning the set, to avoid invalidating the 1391 // 'ReverseDeps' reference. 1392 while (!ReverseDepsToAdd.empty()) { 1393 ReverseLocalDeps[ReverseDepsToAdd.back().first] 1394 .insert(ReverseDepsToAdd.back().second); 1395 ReverseDepsToAdd.pop_back(); 1396 } 1397 } 1398 1399 ReverseDepIt = ReverseNonLocalDeps.find(RemInst); 1400 if (ReverseDepIt != ReverseNonLocalDeps.end()) { 1401 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second; 1402 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end(); 1403 I != E; ++I) { 1404 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst"); 1405 1406 PerInstNLInfo &INLD = NonLocalDeps[*I]; 1407 // The information is now dirty! 1408 INLD.second = true; 1409 1410 for (NonLocalDepInfo::iterator DI = INLD.first.begin(), 1411 DE = INLD.first.end(); DI != DE; ++DI) { 1412 if (DI->getResult().getInst() != RemInst) continue; 1413 1414 // Convert to a dirty entry for the subsequent instruction. 1415 DI->setResult(NewDirtyVal); 1416 1417 if (Instruction *NextI = NewDirtyVal.getInst()) 1418 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I)); 1419 } 1420 } 1421 1422 ReverseNonLocalDeps.erase(ReverseDepIt); 1423 1424 // Add new reverse deps after scanning the set, to avoid invalidating 'Set' 1425 while (!ReverseDepsToAdd.empty()) { 1426 ReverseNonLocalDeps[ReverseDepsToAdd.back().first] 1427 .insert(ReverseDepsToAdd.back().second); 1428 ReverseDepsToAdd.pop_back(); 1429 } 1430 } 1431 1432 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a 1433 // value in the NonLocalPointerDeps info. 1434 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt = 1435 ReverseNonLocalPtrDeps.find(RemInst); 1436 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) { 1437 SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second; 1438 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd; 1439 1440 for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(), 1441 E = Set.end(); I != E; ++I) { 1442 ValueIsLoadPair P = *I; 1443 assert(P.getPointer() != RemInst && 1444 "Already removed NonLocalPointerDeps info for RemInst"); 1445 1446 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps; 1447 1448 // The cache is not valid for any specific block anymore. 1449 NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair(); 1450 1451 // Update any entries for RemInst to use the instruction after it. 1452 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end(); 1453 DI != DE; ++DI) { 1454 if (DI->getResult().getInst() != RemInst) continue; 1455 1456 // Convert to a dirty entry for the subsequent instruction. 1457 DI->setResult(NewDirtyVal); 1458 1459 if (Instruction *NewDirtyInst = NewDirtyVal.getInst()) 1460 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P)); 1461 } 1462 1463 // Re-sort the NonLocalDepInfo. Changing the dirty entry to its 1464 // subsequent value may invalidate the sortedness. 1465 std::sort(NLPDI.begin(), NLPDI.end()); 1466 } 1467 1468 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt); 1469 1470 while (!ReversePtrDepsToAdd.empty()) { 1471 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first] 1472 .insert(ReversePtrDepsToAdd.back().second); 1473 ReversePtrDepsToAdd.pop_back(); 1474 } 1475 } 1476 1477 1478 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?"); 1479 AA->deleteValue(RemInst); 1480 DEBUG(verifyRemoved(RemInst)); 1481} 1482/// verifyRemoved - Verify that the specified instruction does not occur 1483/// in our internal data structures. 1484void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const { 1485 for (LocalDepMapType::const_iterator I = LocalDeps.begin(), 1486 E = LocalDeps.end(); I != E; ++I) { 1487 assert(I->first != D && "Inst occurs in data structures"); 1488 assert(I->second.getInst() != D && 1489 "Inst occurs in data structures"); 1490 } 1491 1492 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(), 1493 E = NonLocalPointerDeps.end(); I != E; ++I) { 1494 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key"); 1495 const NonLocalDepInfo &Val = I->second.NonLocalDeps; 1496 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end(); 1497 II != E; ++II) 1498 assert(II->getResult().getInst() != D && "Inst occurs as NLPD value"); 1499 } 1500 1501 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(), 1502 E = NonLocalDeps.end(); I != E; ++I) { 1503 assert(I->first != D && "Inst occurs in data structures"); 1504 const PerInstNLInfo &INLD = I->second; 1505 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(), 1506 EE = INLD.first.end(); II != EE; ++II) 1507 assert(II->getResult().getInst() != D && "Inst occurs in data structures"); 1508 } 1509 1510 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(), 1511 E = ReverseLocalDeps.end(); I != E; ++I) { 1512 assert(I->first != D && "Inst occurs in data structures"); 1513 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(), 1514 EE = I->second.end(); II != EE; ++II) 1515 assert(*II != D && "Inst occurs in data structures"); 1516 } 1517 1518 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(), 1519 E = ReverseNonLocalDeps.end(); 1520 I != E; ++I) { 1521 assert(I->first != D && "Inst occurs in data structures"); 1522 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(), 1523 EE = I->second.end(); II != EE; ++II) 1524 assert(*II != D && "Inst occurs in data structures"); 1525 } 1526 1527 for (ReverseNonLocalPtrDepTy::const_iterator 1528 I = ReverseNonLocalPtrDeps.begin(), 1529 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) { 1530 assert(I->first != D && "Inst occurs in rev NLPD map"); 1531 1532 for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(), 1533 E = I->second.end(); II != E; ++II) 1534 assert(*II != ValueIsLoadPair(D, false) && 1535 *II != ValueIsLoadPair(D, true) && 1536 "Inst occurs in ReverseNonLocalPtrDeps map"); 1537 } 1538 1539} 1540