1 //===- MemoryDependenceAnalysis.cpp - Mem Deps Implementation --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
15 //===----------------------------------------------------------------------===//
17 #define DEBUG_TYPE "memdep"
18 #include "llvm/Analysis/MemoryDependenceAnalysis.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/IntrinsicInst.h"
21 #include "llvm/Function.h"
22 #include "llvm/Analysis/AliasAnalysis.h"
23 #include "llvm/Analysis/MallocHelper.h"
24 #include "llvm/ADT/Statistic.h"
25 #include "llvm/ADT/STLExtras.h"
26 #include "llvm/Support/PredIteratorCache.h"
27 #include "llvm/Support/Debug.h"
30 STATISTIC(NumCacheNonLocal, "Number of fully cached non-local responses");
31 STATISTIC(NumCacheDirtyNonLocal, "Number of dirty cached non-local responses");
32 STATISTIC(NumUncacheNonLocal, "Number of uncached non-local responses");
34 STATISTIC(NumCacheNonLocalPtr,
35 "Number of fully cached non-local ptr responses");
36 STATISTIC(NumCacheDirtyNonLocalPtr,
37 "Number of cached, but dirty, non-local ptr responses");
38 STATISTIC(NumUncacheNonLocalPtr,
39 "Number of uncached non-local ptr responses");
40 STATISTIC(NumCacheCompleteNonLocalPtr,
41 "Number of block queries that were completely cached");
43 char MemoryDependenceAnalysis::ID = 0;
45 // Register this pass...
46 static RegisterPass<MemoryDependenceAnalysis> X("memdep",
47 "Memory Dependence Analysis", false, true);
49 MemoryDependenceAnalysis::MemoryDependenceAnalysis()
50 : FunctionPass(&ID), PredCache(0) {
52 MemoryDependenceAnalysis::~MemoryDependenceAnalysis() {
55 /// Clean up memory in between runs
56 void MemoryDependenceAnalysis::releaseMemory() {
59 NonLocalPointerDeps.clear();
60 ReverseLocalDeps.clear();
61 ReverseNonLocalDeps.clear();
62 ReverseNonLocalPtrDeps.clear();
68 /// getAnalysisUsage - Does not modify anything. It uses Alias Analysis.
70 void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
72 AU.addRequiredTransitive<AliasAnalysis>();
75 bool MemoryDependenceAnalysis::runOnFunction(Function &) {
76 AA = &getAnalysis<AliasAnalysis>();
78 PredCache.reset(new PredIteratorCache());
82 /// RemoveFromReverseMap - This is a helper function that removes Val from
83 /// 'Inst's set in ReverseMap. If the set becomes empty, remove Inst's entry.
84 template <typename KeyTy>
85 static void RemoveFromReverseMap(DenseMap<Instruction*,
86 SmallPtrSet<KeyTy, 4> > &ReverseMap,
87 Instruction *Inst, KeyTy Val) {
88 typename DenseMap<Instruction*, SmallPtrSet<KeyTy, 4> >::iterator
89 InstIt = ReverseMap.find(Inst);
90 assert(InstIt != ReverseMap.end() && "Reverse map out of sync?");
91 bool Found = InstIt->second.erase(Val);
92 assert(Found && "Invalid reverse map!"); Found=Found;
93 if (InstIt->second.empty())
94 ReverseMap.erase(InstIt);
98 /// getCallSiteDependencyFrom - Private helper for finding the local
99 /// dependencies of a call site.
100 MemDepResult MemoryDependenceAnalysis::
101 getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
102 BasicBlock::iterator ScanIt, BasicBlock *BB) {
103 // Walk backwards through the block, looking for dependencies
104 while (ScanIt != BB->begin()) {
105 Instruction *Inst = --ScanIt;
107 // If this inst is a memory op, get the pointer it accessed
109 uint64_t PointerSize = 0;
110 if (StoreInst *S = dyn_cast<StoreInst>(Inst)) {
111 Pointer = S->getPointerOperand();
112 PointerSize = AA->getTypeStoreSize(S->getOperand(0)->getType());
113 } else if (VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
114 Pointer = V->getOperand(0);
115 PointerSize = AA->getTypeStoreSize(V->getType());
116 } else if (FreeInst *F = dyn_cast<FreeInst>(Inst)) {
117 Pointer = F->getPointerOperand();
119 // FreeInsts erase the entire structure
121 } else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
122 // Debug intrinsics don't cause dependences.
123 if (isa<DbgInfoIntrinsic>(Inst)) continue;
124 CallSite InstCS = CallSite::get(Inst);
125 // If these two calls do not interfere, look past it.
126 switch (AA->getModRefInfo(CS, InstCS)) {
127 case AliasAnalysis::NoModRef:
128 // If the two calls don't interact (e.g. InstCS is readnone) keep
131 case AliasAnalysis::Ref:
132 // If the two calls read the same memory locations and CS is a readonly
133 // function, then we have two cases: 1) the calls may not interfere with
134 // each other at all. 2) the calls may produce the same value. In case
135 // #1 we want to ignore the values, in case #2, we want to return Inst
136 // as a Def dependence. This allows us to CSE in cases like:
139 // Y = strlen(P); // Y = X
140 if (isReadOnlyCall) {
141 if (CS.getCalledFunction() != 0 &&
142 CS.getCalledFunction() == InstCS.getCalledFunction())
143 return MemDepResult::getDef(Inst);
144 // Ignore unrelated read/read call dependences.
149 return MemDepResult::getClobber(Inst);
152 // Non-memory instruction.
156 if (AA->getModRefInfo(CS, Pointer, PointerSize) != AliasAnalysis::NoModRef)
157 return MemDepResult::getClobber(Inst);
160 // No dependence found. If this is the entry block of the function, it is a
161 // clobber, otherwise it is non-local.
162 if (BB != &BB->getParent()->getEntryBlock())
163 return MemDepResult::getNonLocal();
164 return MemDepResult::getClobber(ScanIt);
167 /// getPointerDependencyFrom - Return the instruction on which a memory
168 /// location depends. If isLoad is true, this routine ignore may-aliases with
169 /// read-only operations.
170 MemDepResult MemoryDependenceAnalysis::
171 getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad,
172 BasicBlock::iterator ScanIt, BasicBlock *BB) {
174 // Walk backwards through the basic block, looking for dependencies.
175 while (ScanIt != BB->begin()) {
176 Instruction *Inst = --ScanIt;
178 // Debug intrinsics don't cause dependences.
179 if (isa<DbgInfoIntrinsic>(Inst)) continue;
181 // Values depend on loads if the pointers are must aliased. This means that
182 // a load depends on another must aliased load from the same value.
183 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
184 Value *Pointer = LI->getPointerOperand();
185 uint64_t PointerSize = AA->getTypeStoreSize(LI->getType());
187 // If we found a pointer, check if it could be the same as our pointer.
188 AliasAnalysis::AliasResult R =
189 AA->alias(Pointer, PointerSize, MemPtr, MemSize);
190 if (R == AliasAnalysis::NoAlias)
193 // May-alias loads don't depend on each other without a dependence.
194 if (isLoad && R == AliasAnalysis::MayAlias)
196 // Stores depend on may and must aliased loads, loads depend on must-alias
198 return MemDepResult::getDef(Inst);
201 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
202 // If alias analysis can tell that this store is guaranteed to not modify
203 // the query pointer, ignore it. Use getModRefInfo to handle cases where
204 // the query pointer points to constant memory etc.
205 if (AA->getModRefInfo(SI, MemPtr, MemSize) == AliasAnalysis::NoModRef)
208 // Ok, this store might clobber the query pointer. Check to see if it is
209 // a must alias: in this case, we want to return this as a def.
210 Value *Pointer = SI->getPointerOperand();
211 uint64_t PointerSize = AA->getTypeStoreSize(SI->getOperand(0)->getType());
213 // If we found a pointer, check if it could be the same as our pointer.
214 AliasAnalysis::AliasResult R =
215 AA->alias(Pointer, PointerSize, MemPtr, MemSize);
217 if (R == AliasAnalysis::NoAlias)
219 if (R == AliasAnalysis::MayAlias)
220 return MemDepResult::getClobber(Inst);
221 return MemDepResult::getDef(Inst);
224 // If this is an allocation, and if we know that the accessed pointer is to
225 // the allocation, return Def. This means that there is no dependence and
226 // the access can be optimized based on that. For example, a load could
228 // Note: Only determine this to be a malloc if Inst is the malloc call, not
229 // a subsequent bitcast of the malloc call result. There can be stores to
230 // the malloced memory between the malloc call and its bitcast uses, and we
231 // need to continue scanning until the malloc call.
232 if (isa<AllocaInst>(Inst) || extractMallocCall(Inst)) {
233 Value *AccessPtr = MemPtr->getUnderlyingObject();
235 if (AccessPtr == Inst ||
236 AA->alias(Inst, 1, AccessPtr, 1) == AliasAnalysis::MustAlias)
237 return MemDepResult::getDef(Inst);
241 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
242 switch (AA->getModRefInfo(Inst, MemPtr, MemSize)) {
243 case AliasAnalysis::NoModRef:
244 // If the call has no effect on the queried pointer, just ignore it.
246 case AliasAnalysis::Ref:
247 // If the call is known to never store to the pointer, and if this is a
248 // load query, we can safely ignore it (scan past it).
253 // Otherwise, there is a potential dependence. Return a clobber.
254 return MemDepResult::getClobber(Inst);
258 // No dependence found. If this is the entry block of the function, it is a
259 // clobber, otherwise it is non-local.
260 if (BB != &BB->getParent()->getEntryBlock())
261 return MemDepResult::getNonLocal();
262 return MemDepResult::getClobber(ScanIt);
265 /// getDependency - Return the instruction on which a memory operation
267 MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
268 Instruction *ScanPos = QueryInst;
270 // Check for a cached result
271 MemDepResult &LocalCache = LocalDeps[QueryInst];
273 // If the cached entry is non-dirty, just return it. Note that this depends
274 // on MemDepResult's default constructing to 'dirty'.
275 if (!LocalCache.isDirty())
278 // Otherwise, if we have a dirty entry, we know we can start the scan at that
279 // instruction, which may save us some work.
280 if (Instruction *Inst = LocalCache.getInst()) {
283 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst);
286 BasicBlock *QueryParent = QueryInst->getParent();
289 uint64_t MemSize = 0;
292 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
293 // No dependence found. If this is the entry block of the function, it is a
294 // clobber, otherwise it is non-local.
295 if (QueryParent != &QueryParent->getParent()->getEntryBlock())
296 LocalCache = MemDepResult::getNonLocal();
298 LocalCache = MemDepResult::getClobber(QueryInst);
299 } else if (StoreInst *SI = dyn_cast<StoreInst>(QueryInst)) {
300 // If this is a volatile store, don't mess around with it. Just return the
301 // previous instruction as a clobber.
302 if (SI->isVolatile())
303 LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
305 MemPtr = SI->getPointerOperand();
306 MemSize = AA->getTypeStoreSize(SI->getOperand(0)->getType());
308 } else if (LoadInst *LI = dyn_cast<LoadInst>(QueryInst)) {
309 // If this is a volatile load, don't mess around with it. Just return the
310 // previous instruction as a clobber.
311 if (LI->isVolatile())
312 LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
314 MemPtr = LI->getPointerOperand();
315 MemSize = AA->getTypeStoreSize(LI->getType());
317 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
318 CallSite QueryCS = CallSite::get(QueryInst);
319 bool isReadOnly = AA->onlyReadsMemory(QueryCS);
320 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos,
322 } else if (FreeInst *FI = dyn_cast<FreeInst>(QueryInst)) {
323 MemPtr = FI->getPointerOperand();
324 // FreeInsts erase the entire structure, not just a field.
327 // Non-memory instruction.
328 LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
331 // If we need to do a pointer scan, make it happen.
333 LocalCache = getPointerDependencyFrom(MemPtr, MemSize,
334 isa<LoadInst>(QueryInst),
335 ScanPos, QueryParent);
337 // Remember the result!
338 if (Instruction *I = LocalCache.getInst())
339 ReverseLocalDeps[I].insert(QueryInst);
345 /// AssertSorted - This method is used when -debug is specified to verify that
346 /// cache arrays are properly kept sorted.
347 static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
349 if (Count == -1) Count = Cache.size();
350 if (Count == 0) return;
352 for (unsigned i = 1; i != unsigned(Count); ++i)
353 assert(Cache[i-1] <= Cache[i] && "Cache isn't sorted!");
357 /// getNonLocalCallDependency - Perform a full dependency query for the
358 /// specified call, returning the set of blocks that the value is
359 /// potentially live across. The returned set of results will include a
360 /// "NonLocal" result for all blocks where the value is live across.
362 /// This method assumes the instruction returns a "NonLocal" dependency
363 /// within its own block.
365 /// This returns a reference to an internal data structure that may be
366 /// invalidated on the next non-local query or when an instruction is
367 /// removed. Clients must copy this data if they want it around longer than
369 const MemoryDependenceAnalysis::NonLocalDepInfo &
370 MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
371 assert(getDependency(QueryCS.getInstruction()).isNonLocal() &&
372 "getNonLocalCallDependency should only be used on calls with non-local deps!");
373 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()];
374 NonLocalDepInfo &Cache = CacheP.first;
376 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In
377 /// the cached case, this can happen due to instructions being deleted etc. In
378 /// the uncached case, this starts out as the set of predecessors we care
380 SmallVector<BasicBlock*, 32> DirtyBlocks;
382 if (!Cache.empty()) {
383 // Okay, we have a cache entry. If we know it is not dirty, just return it
384 // with no computation.
385 if (!CacheP.second) {
390 // If we already have a partially computed set of results, scan them to
391 // determine what is dirty, seeding our initial DirtyBlocks worklist.
392 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end();
394 if (I->second.isDirty())
395 DirtyBlocks.push_back(I->first);
397 // Sort the cache so that we can do fast binary search lookups below.
398 std::sort(Cache.begin(), Cache.end());
400 ++NumCacheDirtyNonLocal;
401 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: "
402 // << Cache.size() << " cached: " << *QueryInst;
404 // Seed DirtyBlocks with each of the preds of QueryInst's block.
405 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent();
406 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI)
407 DirtyBlocks.push_back(*PI);
408 NumUncacheNonLocal++;
411 // isReadonlyCall - If this is a read-only call, we can be more aggressive.
412 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS);
414 SmallPtrSet<BasicBlock*, 64> Visited;
416 unsigned NumSortedEntries = Cache.size();
417 DEBUG(AssertSorted(Cache));
419 // Iterate while we still have blocks to update.
420 while (!DirtyBlocks.empty()) {
421 BasicBlock *DirtyBB = DirtyBlocks.back();
422 DirtyBlocks.pop_back();
424 // Already processed this block?
425 if (!Visited.insert(DirtyBB))
428 // Do a binary search to see if we already have an entry for this block in
429 // the cache set. If so, find it.
430 DEBUG(AssertSorted(Cache, NumSortedEntries));
431 NonLocalDepInfo::iterator Entry =
432 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries,
433 std::make_pair(DirtyBB, MemDepResult()));
434 if (Entry != Cache.begin() && prior(Entry)->first == DirtyBB)
437 MemDepResult *ExistingResult = 0;
438 if (Entry != Cache.begin()+NumSortedEntries &&
439 Entry->first == DirtyBB) {
440 // If we already have an entry, and if it isn't already dirty, the block
442 if (!Entry->second.isDirty())
445 // Otherwise, remember this slot so we can update the value.
446 ExistingResult = &Entry->second;
449 // If the dirty entry has a pointer, start scanning from it so we don't have
450 // to rescan the entire block.
451 BasicBlock::iterator ScanPos = DirtyBB->end();
452 if (ExistingResult) {
453 if (Instruction *Inst = ExistingResult->getInst()) {
455 // We're removing QueryInst's use of Inst.
456 RemoveFromReverseMap(ReverseNonLocalDeps, Inst,
457 QueryCS.getInstruction());
461 // Find out if this block has a local dependency for QueryInst.
464 if (ScanPos != DirtyBB->begin()) {
465 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
466 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
467 // No dependence found. If this is the entry block of the function, it is
468 // a clobber, otherwise it is non-local.
469 Dep = MemDepResult::getNonLocal();
471 Dep = MemDepResult::getClobber(ScanPos);
474 // If we had a dirty entry for the block, update it. Otherwise, just add
477 *ExistingResult = Dep;
479 Cache.push_back(std::make_pair(DirtyBB, Dep));
481 // If the block has a dependency (i.e. it isn't completely transparent to
482 // the value), remember the association!
483 if (!Dep.isNonLocal()) {
484 // Keep the ReverseNonLocalDeps map up to date so we can efficiently
485 // update this when we remove instructions.
486 if (Instruction *Inst = Dep.getInst())
487 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction());
490 // If the block *is* completely transparent to the load, we need to check
491 // the predecessors of this block. Add them to our worklist.
492 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI)
493 DirtyBlocks.push_back(*PI);
500 /// getNonLocalPointerDependency - Perform a full dependency query for an
501 /// access to the specified (non-volatile) memory location, returning the
502 /// set of instructions that either define or clobber the value.
504 /// This method assumes the pointer has a "NonLocal" dependency within its
507 void MemoryDependenceAnalysis::
508 getNonLocalPointerDependency(Value *Pointer, bool isLoad, BasicBlock *FromBB,
509 SmallVectorImpl<NonLocalDepEntry> &Result) {
510 assert(isa<PointerType>(Pointer->getType()) &&
511 "Can't get pointer deps of a non-pointer!");
514 // We know that the pointer value is live into FromBB find the def/clobbers
515 // from presecessors.
516 const Type *EltTy = cast<PointerType>(Pointer->getType())->getElementType();
517 uint64_t PointeeSize = AA->getTypeStoreSize(EltTy);
519 // This is the set of blocks we've inspected, and the pointer we consider in
520 // each block. Because of critical edges, we currently bail out if querying
521 // a block with multiple different pointers. This can happen during PHI
523 DenseMap<BasicBlock*, Value*> Visited;
524 if (!getNonLocalPointerDepFromBB(Pointer, PointeeSize, isLoad, FromBB,
525 Result, Visited, true))
528 Result.push_back(std::make_pair(FromBB,
529 MemDepResult::getClobber(FromBB->begin())));
532 /// GetNonLocalInfoForBlock - Compute the memdep value for BB with
533 /// Pointer/PointeeSize using either cached information in Cache or by doing a
534 /// lookup (which may use dirty cache info if available). If we do a lookup,
535 /// add the result to the cache.
536 MemDepResult MemoryDependenceAnalysis::
537 GetNonLocalInfoForBlock(Value *Pointer, uint64_t PointeeSize,
538 bool isLoad, BasicBlock *BB,
539 NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
541 // Do a binary search to see if we already have an entry for this block in
542 // the cache set. If so, find it.
543 NonLocalDepInfo::iterator Entry =
544 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries,
545 std::make_pair(BB, MemDepResult()));
546 if (Entry != Cache->begin() && prior(Entry)->first == BB)
549 MemDepResult *ExistingResult = 0;
550 if (Entry != Cache->begin()+NumSortedEntries && Entry->first == BB)
551 ExistingResult = &Entry->second;
553 // If we have a cached entry, and it is non-dirty, use it as the value for
555 if (ExistingResult && !ExistingResult->isDirty()) {
556 ++NumCacheNonLocalPtr;
557 return *ExistingResult;
560 // Otherwise, we have to scan for the value. If we have a dirty cache
561 // entry, start scanning from its position, otherwise we scan from the end
563 BasicBlock::iterator ScanPos = BB->end();
564 if (ExistingResult && ExistingResult->getInst()) {
565 assert(ExistingResult->getInst()->getParent() == BB &&
566 "Instruction invalidated?");
567 ++NumCacheDirtyNonLocalPtr;
568 ScanPos = ExistingResult->getInst();
570 // Eliminating the dirty entry from 'Cache', so update the reverse info.
571 ValueIsLoadPair CacheKey(Pointer, isLoad);
572 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey);
574 ++NumUncacheNonLocalPtr;
577 // Scan the block for the dependency.
578 MemDepResult Dep = getPointerDependencyFrom(Pointer, PointeeSize, isLoad,
581 // If we had a dirty entry for the block, update it. Otherwise, just add
584 *ExistingResult = Dep;
586 Cache->push_back(std::make_pair(BB, Dep));
588 // If the block has a dependency (i.e. it isn't completely transparent to
589 // the value), remember the reverse association because we just added it
591 if (Dep.isNonLocal())
594 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
595 // update MemDep when we remove instructions.
596 Instruction *Inst = Dep.getInst();
597 assert(Inst && "Didn't depend on anything?");
598 ValueIsLoadPair CacheKey(Pointer, isLoad);
599 ReverseNonLocalPtrDeps[Inst].insert(CacheKey);
603 /// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain
604 /// number of elements in the array that are already properly ordered. This is
605 /// optimized for the case when only a few entries are added.
607 SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
608 unsigned NumSortedEntries) {
609 switch (Cache.size() - NumSortedEntries) {
611 // done, no new entries.
614 // Two new entries, insert the last one into place.
615 MemoryDependenceAnalysis::NonLocalDepEntry Val = Cache.back();
617 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
618 std::upper_bound(Cache.begin(), Cache.end()-1, Val);
619 Cache.insert(Entry, Val);
623 // One new entry, Just insert the new value at the appropriate position.
624 if (Cache.size() != 1) {
625 MemoryDependenceAnalysis::NonLocalDepEntry Val = Cache.back();
627 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
628 std::upper_bound(Cache.begin(), Cache.end(), Val);
629 Cache.insert(Entry, Val);
633 // Added many values, do a full scale sort.
634 std::sort(Cache.begin(), Cache.end());
640 /// getNonLocalPointerDepFromBB - Perform a dependency query based on
641 /// pointer/pointeesize starting at the end of StartBB. Add any clobber/def
642 /// results to the results vector and keep track of which blocks are visited in
645 /// This has special behavior for the first block queries (when SkipFirstBlock
646 /// is true). In this special case, it ignores the contents of the specified
647 /// block and starts returning dependence info for its predecessors.
649 /// This function returns false on success, or true to indicate that it could
650 /// not compute dependence information for some reason. This should be treated
651 /// as a clobber dependence on the first instruction in the predecessor block.
652 bool MemoryDependenceAnalysis::
653 getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize,
654 bool isLoad, BasicBlock *StartBB,
655 SmallVectorImpl<NonLocalDepEntry> &Result,
656 DenseMap<BasicBlock*, Value*> &Visited,
657 bool SkipFirstBlock) {
659 // Look up the cached info for Pointer.
660 ValueIsLoadPair CacheKey(Pointer, isLoad);
662 std::pair<BBSkipFirstBlockPair, NonLocalDepInfo> *CacheInfo =
663 &NonLocalPointerDeps[CacheKey];
664 NonLocalDepInfo *Cache = &CacheInfo->second;
666 // If we have valid cached information for exactly the block we are
667 // investigating, just return it with no recomputation.
668 if (CacheInfo->first == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
669 // We have a fully cached result for this query then we can just return the
670 // cached results and populate the visited set. However, we have to verify
671 // that we don't already have conflicting results for these blocks. Check
672 // to ensure that if a block in the results set is in the visited set that
673 // it was for the same pointer query.
674 if (!Visited.empty()) {
675 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
677 DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->first);
678 if (VI == Visited.end() || VI->second == Pointer) continue;
680 // We have a pointer mismatch in a block. Just return clobber, saying
681 // that something was clobbered in this result. We could also do a
682 // non-fully cached query, but there is little point in doing this.
687 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
689 Visited.insert(std::make_pair(I->first, Pointer));
690 if (!I->second.isNonLocal())
691 Result.push_back(*I);
693 ++NumCacheCompleteNonLocalPtr;
697 // Otherwise, either this is a new block, a block with an invalid cache
698 // pointer or one that we're about to invalidate by putting more info into it
699 // than its valid cache info. If empty, the result will be valid cache info,
700 // otherwise it isn't.
702 CacheInfo->first = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
704 CacheInfo->first = BBSkipFirstBlockPair();
706 SmallVector<BasicBlock*, 32> Worklist;
707 Worklist.push_back(StartBB);
709 // Keep track of the entries that we know are sorted. Previously cached
710 // entries will all be sorted. The entries we add we only sort on demand (we
711 // don't insert every element into its sorted position). We know that we
712 // won't get any reuse from currently inserted values, because we don't
713 // revisit blocks after we insert info for them.
714 unsigned NumSortedEntries = Cache->size();
715 DEBUG(AssertSorted(*Cache));
717 while (!Worklist.empty()) {
718 BasicBlock *BB = Worklist.pop_back_val();
720 // Skip the first block if we have it.
721 if (!SkipFirstBlock) {
722 // Analyze the dependency of *Pointer in FromBB. See if we already have
724 assert(Visited.count(BB) && "Should check 'visited' before adding to WL");
726 // Get the dependency info for Pointer in BB. If we have cached
727 // information, we will use it, otherwise we compute it.
728 DEBUG(AssertSorted(*Cache, NumSortedEntries));
729 MemDepResult Dep = GetNonLocalInfoForBlock(Pointer, PointeeSize, isLoad,
730 BB, Cache, NumSortedEntries);
732 // If we got a Def or Clobber, add this to the list of results.
733 if (!Dep.isNonLocal()) {
734 Result.push_back(NonLocalDepEntry(BB, Dep));
739 // If 'Pointer' is an instruction defined in this block, then we need to do
740 // phi translation to change it into a value live in the predecessor block.
741 // If phi translation fails, then we can't continue dependence analysis.
742 Instruction *PtrInst = dyn_cast<Instruction>(Pointer);
743 bool NeedsPHITranslation = PtrInst && PtrInst->getParent() == BB;
745 // If no PHI translation is needed, just add all the predecessors of this
746 // block to scan them as well.
747 if (!NeedsPHITranslation) {
748 SkipFirstBlock = false;
749 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
750 // Verify that we haven't looked at this block yet.
751 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
752 InsertRes = Visited.insert(std::make_pair(*PI, Pointer));
753 if (InsertRes.second) {
754 // First time we've looked at *PI.
755 Worklist.push_back(*PI);
759 // If we have seen this block before, but it was with a different
760 // pointer then we have a phi translation failure and we have to treat
761 // this as a clobber.
762 if (InsertRes.first->second != Pointer)
763 goto PredTranslationFailure;
768 // If we do need to do phi translation, then there are a bunch of different
769 // cases, because we have to find a Value* live in the predecessor block. We
770 // know that PtrInst is defined in this block at least.
772 // We may have added values to the cache list before this PHI translation.
773 // If so, we haven't done anything to ensure that the cache remains sorted.
774 // Sort it now (if needed) so that recursive invocations of
775 // getNonLocalPointerDepFromBB and other routines that could reuse the cache
776 // value will only see properly sorted cache arrays.
777 if (Cache && NumSortedEntries != Cache->size()) {
778 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
779 NumSortedEntries = Cache->size();
782 // If this is directly a PHI node, just use the incoming values for each
783 // pred as the phi translated version.
784 if (PHINode *PtrPHI = dyn_cast<PHINode>(PtrInst)) {
787 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
788 BasicBlock *Pred = *PI;
789 Value *PredPtr = PtrPHI->getIncomingValueForBlock(Pred);
791 // Check to see if we have already visited this pred block with another
792 // pointer. If so, we can't do this lookup. This failure can occur
793 // with PHI translation when a critical edge exists and the PHI node in
794 // the successor translates to a pointer value different than the
795 // pointer the block was first analyzed with.
796 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
797 InsertRes = Visited.insert(std::make_pair(Pred, PredPtr));
799 if (!InsertRes.second) {
800 // If the predecessor was visited with PredPtr, then we already did
801 // the analysis and can ignore it.
802 if (InsertRes.first->second == PredPtr)
805 // Otherwise, the block was previously analyzed with a different
806 // pointer. We can't represent the result of this case, so we just
807 // treat this as a phi translation failure.
808 goto PredTranslationFailure;
811 // FIXME: it is entirely possible that PHI translating will end up with
812 // the same value. Consider PHI translating something like:
813 // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need*
814 // to recurse here, pedantically speaking.
816 // If we have a problem phi translating, fall through to the code below
817 // to handle the failure condition.
818 if (getNonLocalPointerDepFromBB(PredPtr, PointeeSize, isLoad, Pred,
820 goto PredTranslationFailure;
823 // Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
824 CacheInfo = &NonLocalPointerDeps[CacheKey];
825 Cache = &CacheInfo->second;
826 NumSortedEntries = Cache->size();
828 // Since we did phi translation, the "Cache" set won't contain all of the
829 // results for the query. This is ok (we can still use it to accelerate
830 // specific block queries) but we can't do the fastpath "return all
831 // results from the set" Clear out the indicator for this.
832 CacheInfo->first = BBSkipFirstBlockPair();
833 SkipFirstBlock = false;
837 // TODO: BITCAST, GEP.
839 // cerr << "MEMDEP: Could not PHI translate: " << *Pointer;
840 // if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst))
841 // cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0);
842 PredTranslationFailure:
845 // Refresh the CacheInfo/Cache pointer if it got invalidated.
846 CacheInfo = &NonLocalPointerDeps[CacheKey];
847 Cache = &CacheInfo->second;
848 NumSortedEntries = Cache->size();
851 // Since we did phi translation, the "Cache" set won't contain all of the
852 // results for the query. This is ok (we can still use it to accelerate
853 // specific block queries) but we can't do the fastpath "return all
854 // results from the set" Clear out the indicator for this.
855 CacheInfo->first = BBSkipFirstBlockPair();
857 // If *nothing* works, mark the pointer as being clobbered by the first
858 // instruction in this block.
860 // If this is the magic first block, return this as a clobber of the whole
861 // incoming value. Since we can't phi translate to one of the predecessors,
862 // we have to bail out.
866 for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) {
867 assert(I != Cache->rend() && "Didn't find current block??");
871 assert(I->second.isNonLocal() &&
872 "Should only be here with transparent block");
873 I->second = MemDepResult::getClobber(BB->begin());
874 ReverseNonLocalPtrDeps[BB->begin()].insert(CacheKey);
875 Result.push_back(*I);
880 // Okay, we're done now. If we added new values to the cache, re-sort it.
881 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
882 DEBUG(AssertSorted(*Cache));
886 /// RemoveCachedNonLocalPointerDependencies - If P exists in
887 /// CachedNonLocalPointerInfo, remove it.
888 void MemoryDependenceAnalysis::
889 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) {
890 CachedNonLocalPointerInfo::iterator It =
891 NonLocalPointerDeps.find(P);
892 if (It == NonLocalPointerDeps.end()) return;
894 // Remove all of the entries in the BB->val map. This involves removing
895 // instructions from the reverse map.
896 NonLocalDepInfo &PInfo = It->second.second;
898 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
899 Instruction *Target = PInfo[i].second.getInst();
900 if (Target == 0) continue; // Ignore non-local dep results.
901 assert(Target->getParent() == PInfo[i].first);
903 // Eliminating the dirty entry from 'Cache', so update the reverse info.
904 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P);
907 // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo).
908 NonLocalPointerDeps.erase(It);
912 /// invalidateCachedPointerInfo - This method is used to invalidate cached
913 /// information about the specified pointer, because it may be too
914 /// conservative in memdep. This is an optional call that can be used when
915 /// the client detects an equivalence between the pointer and some other
916 /// value and replaces the other value with ptr. This can make Ptr available
917 /// in more places that cached info does not necessarily keep.
918 void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) {
919 // If Ptr isn't really a pointer, just ignore it.
920 if (!isa<PointerType>(Ptr->getType())) return;
921 // Flush store info for the pointer.
922 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false));
923 // Flush load info for the pointer.
924 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true));
927 /// removeInstruction - Remove an instruction from the dependence analysis,
928 /// updating the dependence of instructions that previously depended on it.
929 /// This method attempts to keep the cache coherent using the reverse map.
930 void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) {
931 // Walk through the Non-local dependencies, removing this one as the value
932 // for any cached queries.
933 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst);
934 if (NLDI != NonLocalDeps.end()) {
935 NonLocalDepInfo &BlockMap = NLDI->second.first;
936 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end();
938 if (Instruction *Inst = DI->second.getInst())
939 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst);
940 NonLocalDeps.erase(NLDI);
943 // If we have a cached local dependence query for this instruction, remove it.
945 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst);
946 if (LocalDepEntry != LocalDeps.end()) {
947 // Remove us from DepInst's reverse set now that the local dep info is gone.
948 if (Instruction *Inst = LocalDepEntry->second.getInst())
949 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst);
951 // Remove this local dependency info.
952 LocalDeps.erase(LocalDepEntry);
955 // If we have any cached pointer dependencies on this instruction, remove
956 // them. If the instruction has non-pointer type, then it can't be a pointer
959 // Remove it from both the load info and the store info. The instruction
960 // can't be in either of these maps if it is non-pointer.
961 if (isa<PointerType>(RemInst->getType())) {
962 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false));
963 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true));
966 // Loop over all of the things that depend on the instruction we're removing.
968 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd;
970 // If we find RemInst as a clobber or Def in any of the maps for other values,
971 // we need to replace its entry with a dirty version of the instruction after
972 // it. If RemInst is a terminator, we use a null dirty value.
974 // Using a dirty version of the instruction after RemInst saves having to scan
975 // the entire block to get to this point.
976 MemDepResult NewDirtyVal;
977 if (!RemInst->isTerminator())
978 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst));
980 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst);
981 if (ReverseDepIt != ReverseLocalDeps.end()) {
982 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second;
983 // RemInst can't be the terminator if it has local stuff depending on it.
984 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) &&
985 "Nothing can locally depend on a terminator");
987 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(),
988 E = ReverseDeps.end(); I != E; ++I) {
989 Instruction *InstDependingOnRemInst = *I;
990 assert(InstDependingOnRemInst != RemInst &&
991 "Already removed our local dep info");
993 LocalDeps[InstDependingOnRemInst] = NewDirtyVal;
995 // Make sure to remember that new things depend on NewDepInst.
996 assert(NewDirtyVal.getInst() && "There is no way something else can have "
997 "a local dep on this if it is a terminator!");
998 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(),
999 InstDependingOnRemInst));
1002 ReverseLocalDeps.erase(ReverseDepIt);
1004 // Add new reverse deps after scanning the set, to avoid invalidating the
1005 // 'ReverseDeps' reference.
1006 while (!ReverseDepsToAdd.empty()) {
1007 ReverseLocalDeps[ReverseDepsToAdd.back().first]
1008 .insert(ReverseDepsToAdd.back().second);
1009 ReverseDepsToAdd.pop_back();
1013 ReverseDepIt = ReverseNonLocalDeps.find(RemInst);
1014 if (ReverseDepIt != ReverseNonLocalDeps.end()) {
1015 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second;
1016 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end();
1018 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst");
1020 PerInstNLInfo &INLD = NonLocalDeps[*I];
1021 // The information is now dirty!
1024 for (NonLocalDepInfo::iterator DI = INLD.first.begin(),
1025 DE = INLD.first.end(); DI != DE; ++DI) {
1026 if (DI->second.getInst() != RemInst) continue;
1028 // Convert to a dirty entry for the subsequent instruction.
1029 DI->second = NewDirtyVal;
1031 if (Instruction *NextI = NewDirtyVal.getInst())
1032 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I));
1036 ReverseNonLocalDeps.erase(ReverseDepIt);
1038 // Add new reverse deps after scanning the set, to avoid invalidating 'Set'
1039 while (!ReverseDepsToAdd.empty()) {
1040 ReverseNonLocalDeps[ReverseDepsToAdd.back().first]
1041 .insert(ReverseDepsToAdd.back().second);
1042 ReverseDepsToAdd.pop_back();
1046 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a
1047 // value in the NonLocalPointerDeps info.
1048 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt =
1049 ReverseNonLocalPtrDeps.find(RemInst);
1050 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) {
1051 SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second;
1052 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd;
1054 for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(),
1055 E = Set.end(); I != E; ++I) {
1056 ValueIsLoadPair P = *I;
1057 assert(P.getPointer() != RemInst &&
1058 "Already removed NonLocalPointerDeps info for RemInst");
1060 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].second;
1062 // The cache is not valid for any specific block anymore.
1063 NonLocalPointerDeps[P].first = BBSkipFirstBlockPair();
1065 // Update any entries for RemInst to use the instruction after it.
1066 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
1068 if (DI->second.getInst() != RemInst) continue;
1070 // Convert to a dirty entry for the subsequent instruction.
1071 DI->second = NewDirtyVal;
1073 if (Instruction *NewDirtyInst = NewDirtyVal.getInst())
1074 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P));
1077 // Re-sort the NonLocalDepInfo. Changing the dirty entry to its
1078 // subsequent value may invalidate the sortedness.
1079 std::sort(NLPDI.begin(), NLPDI.end());
1082 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt);
1084 while (!ReversePtrDepsToAdd.empty()) {
1085 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first]
1086 .insert(ReversePtrDepsToAdd.back().second);
1087 ReversePtrDepsToAdd.pop_back();
1092 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?");
1093 AA->deleteValue(RemInst);
1094 DEBUG(verifyRemoved(RemInst));
1096 /// verifyRemoved - Verify that the specified instruction does not occur
1097 /// in our internal data structures.
1098 void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const {
1099 for (LocalDepMapType::const_iterator I = LocalDeps.begin(),
1100 E = LocalDeps.end(); I != E; ++I) {
1101 assert(I->first != D && "Inst occurs in data structures");
1102 assert(I->second.getInst() != D &&
1103 "Inst occurs in data structures");
1106 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(),
1107 E = NonLocalPointerDeps.end(); I != E; ++I) {
1108 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key");
1109 const NonLocalDepInfo &Val = I->second.second;
1110 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end();
1112 assert(II->second.getInst() != D && "Inst occurs as NLPD value");
1115 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(),
1116 E = NonLocalDeps.end(); I != E; ++I) {
1117 assert(I->first != D && "Inst occurs in data structures");
1118 const PerInstNLInfo &INLD = I->second;
1119 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(),
1120 EE = INLD.first.end(); II != EE; ++II)
1121 assert(II->second.getInst() != D && "Inst occurs in data structures");
1124 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(),
1125 E = ReverseLocalDeps.end(); I != E; ++I) {
1126 assert(I->first != D && "Inst occurs in data structures");
1127 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1128 EE = I->second.end(); II != EE; ++II)
1129 assert(*II != D && "Inst occurs in data structures");
1132 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(),
1133 E = ReverseNonLocalDeps.end();
1135 assert(I->first != D && "Inst occurs in data structures");
1136 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1137 EE = I->second.end(); II != EE; ++II)
1138 assert(*II != D && "Inst occurs in data structures");
1141 for (ReverseNonLocalPtrDepTy::const_iterator
1142 I = ReverseNonLocalPtrDeps.begin(),
1143 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) {
1144 assert(I->first != D && "Inst occurs in rev NLPD map");
1146 for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(),
1147 E = I->second.end(); II != E; ++II)
1148 assert(*II != ValueIsLoadPair(D, false) &&
1149 *II != ValueIsLoadPair(D, true) &&
1150 "Inst occurs in ReverseNonLocalPtrDeps map");