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/Constants.h"
20 #include "llvm/Instructions.h"
21 #include "llvm/Function.h"
22 #include "llvm/Analysis/AliasAnalysis.h"
23 #include "llvm/ADT/Statistic.h"
24 #include "llvm/ADT/STLExtras.h"
25 #include "llvm/Support/PredIteratorCache.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Target/TargetData.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>();
73 AU.addRequiredTransitive<TargetData>();
76 bool MemoryDependenceAnalysis::runOnFunction(Function &) {
77 AA = &getAnalysis<AliasAnalysis>();
78 TD = &getAnalysis<TargetData>();
80 PredCache.reset(new PredIteratorCache());
84 /// RemoveFromReverseMap - This is a helper function that removes Val from
85 /// 'Inst's set in ReverseMap. If the set becomes empty, remove Inst's entry.
86 template <typename KeyTy>
87 static void RemoveFromReverseMap(DenseMap<Instruction*,
88 SmallPtrSet<KeyTy*, 4> > &ReverseMap,
89 Instruction *Inst, KeyTy *Val) {
90 typename DenseMap<Instruction*, SmallPtrSet<KeyTy*, 4> >::iterator
91 InstIt = ReverseMap.find(Inst);
92 assert(InstIt != ReverseMap.end() && "Reverse map out of sync?");
93 bool Found = InstIt->second.erase(Val);
94 assert(Found && "Invalid reverse map!"); Found=Found;
95 if (InstIt->second.empty())
96 ReverseMap.erase(InstIt);
100 /// getCallSiteDependencyFrom - Private helper for finding the local
101 /// dependencies of a call site.
102 MemDepResult MemoryDependenceAnalysis::
103 getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
104 BasicBlock::iterator ScanIt, BasicBlock *BB) {
105 // Walk backwards through the block, looking for dependencies
106 while (ScanIt != BB->begin()) {
107 Instruction *Inst = --ScanIt;
109 // If this inst is a memory op, get the pointer it accessed
111 uint64_t PointerSize = 0;
112 if (StoreInst *S = dyn_cast<StoreInst>(Inst)) {
113 Pointer = S->getPointerOperand();
114 PointerSize = TD->getTypeStoreSize(S->getOperand(0)->getType());
115 } else if (VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
116 Pointer = V->getOperand(0);
117 PointerSize = TD->getTypeStoreSize(V->getType());
118 } else if (FreeInst *F = dyn_cast<FreeInst>(Inst)) {
119 Pointer = F->getPointerOperand();
121 // FreeInsts erase the entire structure
123 } else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
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 // Values depend on loads if the pointers are must aliased. This means that
179 // a load depends on another must aliased load from the same value.
180 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
181 Value *Pointer = LI->getPointerOperand();
182 uint64_t PointerSize = TD->getTypeStoreSize(LI->getType());
184 // If we found a pointer, check if it could be the same as our pointer.
185 AliasAnalysis::AliasResult R =
186 AA->alias(Pointer, PointerSize, MemPtr, MemSize);
187 if (R == AliasAnalysis::NoAlias)
190 // May-alias loads don't depend on each other without a dependence.
191 if (isLoad && R == AliasAnalysis::MayAlias)
193 // Stores depend on may and must aliased loads, loads depend on must-alias
195 return MemDepResult::getDef(Inst);
198 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
199 Value *Pointer = SI->getPointerOperand();
200 uint64_t PointerSize = TD->getTypeStoreSize(SI->getOperand(0)->getType());
202 // If we found a pointer, check if it could be the same as our pointer.
203 AliasAnalysis::AliasResult R =
204 AA->alias(Pointer, PointerSize, MemPtr, MemSize);
206 if (R == AliasAnalysis::NoAlias)
208 if (R == AliasAnalysis::MayAlias)
209 return MemDepResult::getClobber(Inst);
210 return MemDepResult::getDef(Inst);
213 // If this is an allocation, and if we know that the accessed pointer is to
214 // the allocation, return Def. This means that there is no dependence and
215 // the access can be optimized based on that. For example, a load could
217 if (AllocationInst *AI = dyn_cast<AllocationInst>(Inst)) {
218 Value *AccessPtr = MemPtr->getUnderlyingObject();
220 if (AccessPtr == AI ||
221 AA->alias(AI, 1, AccessPtr, 1) == AliasAnalysis::MustAlias)
222 return MemDepResult::getDef(AI);
226 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
227 switch (AA->getModRefInfo(Inst, MemPtr, MemSize)) {
228 case AliasAnalysis::NoModRef:
229 // If the call has no effect on the queried pointer, just ignore it.
231 case AliasAnalysis::Ref:
232 // If the call is known to never store to the pointer, and if this is a
233 // load query, we can safely ignore it (scan past it).
238 // Otherwise, there is a potential dependence. Return a clobber.
239 return MemDepResult::getClobber(Inst);
243 // No dependence found. If this is the entry block of the function, it is a
244 // clobber, otherwise it is non-local.
245 if (BB != &BB->getParent()->getEntryBlock())
246 return MemDepResult::getNonLocal();
247 return MemDepResult::getClobber(ScanIt);
250 /// getDependency - Return the instruction on which a memory operation
252 MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
253 Instruction *ScanPos = QueryInst;
255 // Check for a cached result
256 MemDepResult &LocalCache = LocalDeps[QueryInst];
258 // If the cached entry is non-dirty, just return it. Note that this depends
259 // on MemDepResult's default constructing to 'dirty'.
260 if (!LocalCache.isDirty())
263 // Otherwise, if we have a dirty entry, we know we can start the scan at that
264 // instruction, which may save us some work.
265 if (Instruction *Inst = LocalCache.getInst()) {
268 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst);
271 BasicBlock *QueryParent = QueryInst->getParent();
274 uint64_t MemSize = 0;
277 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
278 // No dependence found. If this is the entry block of the function, it is a
279 // clobber, otherwise it is non-local.
280 if (QueryParent != &QueryParent->getParent()->getEntryBlock())
281 LocalCache = MemDepResult::getNonLocal();
283 LocalCache = MemDepResult::getClobber(QueryInst);
284 } else if (StoreInst *SI = dyn_cast<StoreInst>(QueryInst)) {
285 // If this is a volatile store, don't mess around with it. Just return the
286 // previous instruction as a clobber.
287 if (SI->isVolatile())
288 LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
290 MemPtr = SI->getPointerOperand();
291 MemSize = TD->getTypeStoreSize(SI->getOperand(0)->getType());
293 } else if (LoadInst *LI = dyn_cast<LoadInst>(QueryInst)) {
294 // If this is a volatile load, don't mess around with it. Just return the
295 // previous instruction as a clobber.
296 if (LI->isVolatile())
297 LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
299 MemPtr = LI->getPointerOperand();
300 MemSize = TD->getTypeStoreSize(LI->getType());
302 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
303 CallSite QueryCS = CallSite::get(QueryInst);
304 bool isReadOnly = AA->onlyReadsMemory(QueryCS);
305 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos,
307 } else if (FreeInst *FI = dyn_cast<FreeInst>(QueryInst)) {
308 MemPtr = FI->getPointerOperand();
309 // FreeInsts erase the entire structure, not just a field.
312 // Non-memory instruction.
313 LocalCache = MemDepResult::getClobber(--BasicBlock::iterator(ScanPos));
316 // If we need to do a pointer scan, make it happen.
318 LocalCache = getPointerDependencyFrom(MemPtr, MemSize,
319 isa<LoadInst>(QueryInst),
320 ScanPos, QueryParent);
322 // Remember the result!
323 if (Instruction *I = LocalCache.getInst())
324 ReverseLocalDeps[I].insert(QueryInst);
329 /// getNonLocalCallDependency - Perform a full dependency query for the
330 /// specified call, returning the set of blocks that the value is
331 /// potentially live across. The returned set of results will include a
332 /// "NonLocal" result for all blocks where the value is live across.
334 /// This method assumes the instruction returns a "NonLocal" dependency
335 /// within its own block.
337 /// This returns a reference to an internal data structure that may be
338 /// invalidated on the next non-local query or when an instruction is
339 /// removed. Clients must copy this data if they want it around longer than
341 const MemoryDependenceAnalysis::NonLocalDepInfo &
342 MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
343 assert(getDependency(QueryCS.getInstruction()).isNonLocal() &&
344 "getNonLocalCallDependency should only be used on calls with non-local deps!");
345 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()];
346 NonLocalDepInfo &Cache = CacheP.first;
348 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In
349 /// the cached case, this can happen due to instructions being deleted etc. In
350 /// the uncached case, this starts out as the set of predecessors we care
352 SmallVector<BasicBlock*, 32> DirtyBlocks;
354 if (!Cache.empty()) {
355 // Okay, we have a cache entry. If we know it is not dirty, just return it
356 // with no computation.
357 if (!CacheP.second) {
362 // If we already have a partially computed set of results, scan them to
363 // determine what is dirty, seeding our initial DirtyBlocks worklist.
364 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end();
366 if (I->second.isDirty())
367 DirtyBlocks.push_back(I->first);
369 // Sort the cache so that we can do fast binary search lookups below.
370 std::sort(Cache.begin(), Cache.end());
372 ++NumCacheDirtyNonLocal;
373 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: "
374 // << Cache.size() << " cached: " << *QueryInst;
376 // Seed DirtyBlocks with each of the preds of QueryInst's block.
377 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent();
378 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI)
379 DirtyBlocks.push_back(*PI);
380 NumUncacheNonLocal++;
383 // isReadonlyCall - If this is a read-only call, we can be more aggressive.
384 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS);
386 // Visited checked first, vector in sorted order.
387 SmallPtrSet<BasicBlock*, 64> Visited;
389 unsigned NumSortedEntries = Cache.size();
391 // Iterate while we still have blocks to update.
392 while (!DirtyBlocks.empty()) {
393 BasicBlock *DirtyBB = DirtyBlocks.back();
394 DirtyBlocks.pop_back();
396 // Already processed this block?
397 if (!Visited.insert(DirtyBB))
400 // Do a binary search to see if we already have an entry for this block in
401 // the cache set. If so, find it.
402 NonLocalDepInfo::iterator Entry =
403 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries,
404 std::make_pair(DirtyBB, MemDepResult()));
405 if (Entry != Cache.begin() && prior(Entry)->first == DirtyBB)
408 MemDepResult *ExistingResult = 0;
409 if (Entry != Cache.begin()+NumSortedEntries &&
410 Entry->first == DirtyBB) {
411 // If we already have an entry, and if it isn't already dirty, the block
413 if (!Entry->second.isDirty())
416 // Otherwise, remember this slot so we can update the value.
417 ExistingResult = &Entry->second;
420 // If the dirty entry has a pointer, start scanning from it so we don't have
421 // to rescan the entire block.
422 BasicBlock::iterator ScanPos = DirtyBB->end();
423 if (ExistingResult) {
424 if (Instruction *Inst = ExistingResult->getInst()) {
426 // We're removing QueryInst's use of Inst.
427 RemoveFromReverseMap(ReverseNonLocalDeps, Inst,
428 QueryCS.getInstruction());
432 // Find out if this block has a local dependency for QueryInst.
435 if (ScanPos != DirtyBB->begin()) {
436 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
437 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
438 // No dependence found. If this is the entry block of the function, it is
439 // a clobber, otherwise it is non-local.
440 Dep = MemDepResult::getNonLocal();
442 Dep = MemDepResult::getClobber(ScanPos);
445 // If we had a dirty entry for the block, update it. Otherwise, just add
448 *ExistingResult = Dep;
450 Cache.push_back(std::make_pair(DirtyBB, Dep));
452 // If the block has a dependency (i.e. it isn't completely transparent to
453 // the value), remember the association!
454 if (!Dep.isNonLocal()) {
455 // Keep the ReverseNonLocalDeps map up to date so we can efficiently
456 // update this when we remove instructions.
457 if (Instruction *Inst = Dep.getInst())
458 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction());
461 // If the block *is* completely transparent to the load, we need to check
462 // the predecessors of this block. Add them to our worklist.
463 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI)
464 DirtyBlocks.push_back(*PI);
471 /// getNonLocalPointerDependency - Perform a full dependency query for an
472 /// access to the specified (non-volatile) memory location, returning the
473 /// set of instructions that either define or clobber the value.
475 /// This method assumes the pointer has a "NonLocal" dependency within its
478 void MemoryDependenceAnalysis::
479 getNonLocalPointerDependency(Value *Pointer, bool isLoad, BasicBlock *FromBB,
480 SmallVectorImpl<NonLocalDepEntry> &Result) {
481 assert(isa<PointerType>(Pointer->getType()) &&
482 "Can't get pointer deps of a non-pointer!");
485 // We know that the pointer value is live into FromBB find the def/clobbers
486 // from presecessors.
487 const Type *EltTy = cast<PointerType>(Pointer->getType())->getElementType();
488 uint64_t PointeeSize = TD->getTypeStoreSize(EltTy);
490 // While we have blocks to analyze, get their values.
491 SmallPtrSet<BasicBlock*, 64> Visited;
492 getNonLocalPointerDepFromBB(Pointer, PointeeSize, isLoad, FromBB,
496 /// GetNonLocalInfoForBlock - Compute the memdep value for BB with
497 /// Pointer/PointeeSize using either cached information in Cache or by doing a
498 /// lookup (which may use dirty cache info if available). If we do a lookup,
499 /// add the result to the cache.
500 MemDepResult MemoryDependenceAnalysis::
501 GetNonLocalInfoForBlock(Value *Pointer, uint64_t PointeeSize,
502 bool isLoad, BasicBlock *BB,
503 NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
505 // Do a binary search to see if we already have an entry for this block in
506 // the cache set. If so, find it.
507 NonLocalDepInfo::iterator Entry =
508 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries,
509 std::make_pair(BB, MemDepResult()));
510 if (Entry != Cache->begin() && prior(Entry)->first == BB)
513 MemDepResult *ExistingResult = 0;
514 if (Entry != Cache->begin()+NumSortedEntries && Entry->first == BB)
515 ExistingResult = &Entry->second;
517 // If we have a cached entry, and it is non-dirty, use it as the value for
519 if (ExistingResult && !ExistingResult->isDirty()) {
520 ++NumCacheNonLocalPtr;
521 return *ExistingResult;
524 // Otherwise, we have to scan for the value. If we have a dirty cache
525 // entry, start scanning from its position, otherwise we scan from the end
527 BasicBlock::iterator ScanPos = BB->end();
528 if (ExistingResult && ExistingResult->getInst()) {
529 assert(ExistingResult->getInst()->getParent() == BB &&
530 "Instruction invalidated?");
531 ++NumCacheDirtyNonLocalPtr;
532 ScanPos = ExistingResult->getInst();
534 // Eliminating the dirty entry from 'Cache', so update the reverse info.
535 ValueIsLoadPair CacheKey(Pointer, isLoad);
536 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos,
537 CacheKey.getOpaqueValue());
539 ++NumUncacheNonLocalPtr;
542 // Scan the block for the dependency.
543 MemDepResult Dep = getPointerDependencyFrom(Pointer, PointeeSize, isLoad,
546 // If we had a dirty entry for the block, update it. Otherwise, just add
549 *ExistingResult = Dep;
551 Cache->push_back(std::make_pair(BB, Dep));
553 // If the block has a dependency (i.e. it isn't completely transparent to
554 // the value), remember the reverse association because we just added it
556 if (Dep.isNonLocal())
559 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
560 // update MemDep when we remove instructions.
561 Instruction *Inst = Dep.getInst();
562 assert(Inst && "Didn't depend on anything?");
563 ValueIsLoadPair CacheKey(Pointer, isLoad);
564 ReverseNonLocalPtrDeps[Inst].insert(CacheKey.getOpaqueValue());
569 /// getNonLocalPointerDepFromBB -
570 void MemoryDependenceAnalysis::
571 getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize,
572 bool isLoad, BasicBlock *StartBB,
573 SmallVectorImpl<NonLocalDepEntry> &Result,
574 SmallPtrSet<BasicBlock*, 64> &Visited) {
575 // Look up the cached info for Pointer.
576 ValueIsLoadPair CacheKey(Pointer, isLoad);
578 std::pair<BasicBlock*, NonLocalDepInfo> &CacheInfo =
579 NonLocalPointerDeps[CacheKey];
580 NonLocalDepInfo *Cache = &CacheInfo.second;
582 // If we have valid cached information for exactly the block we are
583 // investigating, just return it with no recomputation.
584 if (CacheInfo.first == StartBB) {
585 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
587 if (!I->second.isNonLocal())
588 Result.push_back(*I);
589 ++NumCacheCompleteNonLocalPtr;
593 // Otherwise, either this is a new block, a block with an invalid cache
594 // pointer or one that we're about to invalidate by putting more info into it
595 // than its valid cache info. If empty, the result will be valid cache info,
596 // otherwise it isn't.
597 CacheInfo.first = Cache->empty() ? StartBB : 0;
599 SmallVector<BasicBlock*, 32> Worklist;
600 Worklist.push_back(StartBB);
602 // Keep track of the entries that we know are sorted. Previously cached
603 // entries will all be sorted. The entries we add we only sort on demand (we
604 // don't insert every element into its sorted position). We know that we
605 // won't get any reuse from currently inserted values, because we don't
606 // revisit blocks after we insert info for them.
607 unsigned NumSortedEntries = Cache->size();
609 // SkipFirstBlock - If this is the very first block that we're processing, we
610 // don't want to scan or think about its body, because the client was supposed
611 // to do a local dependence query. Instead, just start processing it by
612 // adding its predecessors to the worklist and iterating.
613 bool SkipFirstBlock = Visited.empty();
615 while (!Worklist.empty()) {
616 BasicBlock *BB = Worklist.pop_back_val();
618 // Skip the first block if we have it.
619 if (SkipFirstBlock) {
620 SkipFirstBlock = false;
622 // Analyze the dependency of *Pointer in FromBB. See if we already have
624 if (!Visited.insert(BB))
627 // Get the dependency info for Pointer in BB. If we have cached
628 // information, we will use it, otherwise we compute it.
629 MemDepResult Dep = GetNonLocalInfoForBlock(Pointer, PointeeSize, isLoad,
630 BB, Cache, NumSortedEntries);
632 // If we got a Def or Clobber, add this to the list of results.
633 if (!Dep.isNonLocal()) {
634 Result.push_back(NonLocalDepEntry(BB, Dep));
639 // Otherwise, we have to process all the predecessors of this block to scan
641 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
642 // TODO: PHI TRANSLATE.
643 Worklist.push_back(*PI);
647 // Okay, we're done now. If we added new values to the cache, re-sort it.
648 switch (Cache->size()-NumSortedEntries) {
650 // done, no new entries.
653 // Two new entries, insert the last one into place.
654 NonLocalDepEntry Val = Cache->back();
656 NonLocalDepInfo::iterator Entry =
657 std::upper_bound(Cache->begin(), Cache->end()-1, Val);
658 Cache->insert(Entry, Val);
662 // One new entry, Just insert the new value at the appropriate position.
663 NonLocalDepEntry Val = Cache->back();
665 NonLocalDepInfo::iterator Entry =
666 std::upper_bound(Cache->begin(), Cache->end(), Val);
667 Cache->insert(Entry, Val);
671 // Added many values, do a full scale sort.
672 std::sort(Cache->begin(), Cache->end());
676 /// RemoveCachedNonLocalPointerDependencies - If P exists in
677 /// CachedNonLocalPointerInfo, remove it.
678 void MemoryDependenceAnalysis::
679 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) {
680 CachedNonLocalPointerInfo::iterator It =
681 NonLocalPointerDeps.find(P);
682 if (It == NonLocalPointerDeps.end()) return;
684 // Remove all of the entries in the BB->val map. This involves removing
685 // instructions from the reverse map.
686 NonLocalDepInfo &PInfo = It->second.second;
688 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
689 Instruction *Target = PInfo[i].second.getInst();
690 if (Target == 0) continue; // Ignore non-local dep results.
691 assert(Target->getParent() == PInfo[i].first);
693 // Eliminating the dirty entry from 'Cache', so update the reverse info.
694 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P.getOpaqueValue());
697 // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo).
698 NonLocalPointerDeps.erase(It);
702 /// invalidateCachedPointerInfo - This method is used to invalidate cached
703 /// information about the specified pointer, because it may be too
704 /// conservative in memdep. This is an optional call that can be used when
705 /// the client detects an equivalence between the pointer and some other
706 /// value and replaces the other value with ptr. This can make Ptr available
707 /// in more places that cached info does not necessarily keep.
708 void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) {
709 // If Ptr isn't really a pointer, just ignore it.
710 if (!isa<PointerType>(Ptr->getType())) return;
711 // Flush store info for the pointer.
712 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false));
713 // Flush load info for the pointer.
714 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true));
717 /// removeInstruction - Remove an instruction from the dependence analysis,
718 /// updating the dependence of instructions that previously depended on it.
719 /// This method attempts to keep the cache coherent using the reverse map.
720 void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) {
721 // Walk through the Non-local dependencies, removing this one as the value
722 // for any cached queries.
723 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst);
724 if (NLDI != NonLocalDeps.end()) {
725 NonLocalDepInfo &BlockMap = NLDI->second.first;
726 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end();
728 if (Instruction *Inst = DI->second.getInst())
729 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst);
730 NonLocalDeps.erase(NLDI);
733 // If we have a cached local dependence query for this instruction, remove it.
735 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst);
736 if (LocalDepEntry != LocalDeps.end()) {
737 // Remove us from DepInst's reverse set now that the local dep info is gone.
738 if (Instruction *Inst = LocalDepEntry->second.getInst())
739 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst);
741 // Remove this local dependency info.
742 LocalDeps.erase(LocalDepEntry);
745 // If we have any cached pointer dependencies on this instruction, remove
746 // them. If the instruction has non-pointer type, then it can't be a pointer
749 // Remove it from both the load info and the store info. The instruction
750 // can't be in either of these maps if it is non-pointer.
751 if (isa<PointerType>(RemInst->getType())) {
752 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false));
753 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true));
756 // Loop over all of the things that depend on the instruction we're removing.
758 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd;
760 // If we find RemInst as a clobber or Def in any of the maps for other values,
761 // we need to replace its entry with a dirty version of the instruction after
762 // it. If RemInst is a terminator, we use a null dirty value.
764 // Using a dirty version of the instruction after RemInst saves having to scan
765 // the entire block to get to this point.
766 MemDepResult NewDirtyVal;
767 if (!RemInst->isTerminator())
768 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst));
770 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst);
771 if (ReverseDepIt != ReverseLocalDeps.end()) {
772 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second;
773 // RemInst can't be the terminator if it has local stuff depending on it.
774 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) &&
775 "Nothing can locally depend on a terminator");
777 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(),
778 E = ReverseDeps.end(); I != E; ++I) {
779 Instruction *InstDependingOnRemInst = *I;
780 assert(InstDependingOnRemInst != RemInst &&
781 "Already removed our local dep info");
783 LocalDeps[InstDependingOnRemInst] = NewDirtyVal;
785 // Make sure to remember that new things depend on NewDepInst.
786 assert(NewDirtyVal.getInst() && "There is no way something else can have "
787 "a local dep on this if it is a terminator!");
788 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(),
789 InstDependingOnRemInst));
792 ReverseLocalDeps.erase(ReverseDepIt);
794 // Add new reverse deps after scanning the set, to avoid invalidating the
795 // 'ReverseDeps' reference.
796 while (!ReverseDepsToAdd.empty()) {
797 ReverseLocalDeps[ReverseDepsToAdd.back().first]
798 .insert(ReverseDepsToAdd.back().second);
799 ReverseDepsToAdd.pop_back();
803 ReverseDepIt = ReverseNonLocalDeps.find(RemInst);
804 if (ReverseDepIt != ReverseNonLocalDeps.end()) {
805 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second;
806 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end();
808 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst");
810 PerInstNLInfo &INLD = NonLocalDeps[*I];
811 // The information is now dirty!
814 for (NonLocalDepInfo::iterator DI = INLD.first.begin(),
815 DE = INLD.first.end(); DI != DE; ++DI) {
816 if (DI->second.getInst() != RemInst) continue;
818 // Convert to a dirty entry for the subsequent instruction.
819 DI->second = NewDirtyVal;
821 if (Instruction *NextI = NewDirtyVal.getInst())
822 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I));
826 ReverseNonLocalDeps.erase(ReverseDepIt);
828 // Add new reverse deps after scanning the set, to avoid invalidating 'Set'
829 while (!ReverseDepsToAdd.empty()) {
830 ReverseNonLocalDeps[ReverseDepsToAdd.back().first]
831 .insert(ReverseDepsToAdd.back().second);
832 ReverseDepsToAdd.pop_back();
836 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a
837 // value in the NonLocalPointerDeps info.
838 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt =
839 ReverseNonLocalPtrDeps.find(RemInst);
840 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) {
841 SmallPtrSet<void*, 4> &Set = ReversePtrDepIt->second;
842 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd;
844 for (SmallPtrSet<void*, 4>::iterator I = Set.begin(), E = Set.end();
847 P.setFromOpaqueValue(*I);
848 assert(P.getPointer() != RemInst &&
849 "Already removed NonLocalPointerDeps info for RemInst");
851 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].second;
853 // The cache is not valid for any specific block anymore.
854 NonLocalPointerDeps[P].first = 0;
856 // Update any entries for RemInst to use the instruction after it.
857 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
859 if (DI->second.getInst() != RemInst) continue;
861 // Convert to a dirty entry for the subsequent instruction.
862 DI->second = NewDirtyVal;
864 if (Instruction *NewDirtyInst = NewDirtyVal.getInst())
865 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P));
869 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt);
871 while (!ReversePtrDepsToAdd.empty()) {
872 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first]
873 .insert(ReversePtrDepsToAdd.back().second.getOpaqueValue());
874 ReversePtrDepsToAdd.pop_back();
879 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?");
880 AA->deleteValue(RemInst);
881 DEBUG(verifyRemoved(RemInst));
883 /// verifyRemoved - Verify that the specified instruction does not occur
884 /// in our internal data structures.
885 void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const {
886 for (LocalDepMapType::const_iterator I = LocalDeps.begin(),
887 E = LocalDeps.end(); I != E; ++I) {
888 assert(I->first != D && "Inst occurs in data structures");
889 assert(I->second.getInst() != D &&
890 "Inst occurs in data structures");
893 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(),
894 E = NonLocalPointerDeps.end(); I != E; ++I) {
895 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key");
896 const NonLocalDepInfo &Val = I->second.second;
897 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end();
899 assert(II->second.getInst() != D && "Inst occurs as NLPD value");
902 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(),
903 E = NonLocalDeps.end(); I != E; ++I) {
904 assert(I->first != D && "Inst occurs in data structures");
905 const PerInstNLInfo &INLD = I->second;
906 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(),
907 EE = INLD.first.end(); II != EE; ++II)
908 assert(II->second.getInst() != D && "Inst occurs in data structures");
911 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(),
912 E = ReverseLocalDeps.end(); I != E; ++I) {
913 assert(I->first != D && "Inst occurs in data structures");
914 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
915 EE = I->second.end(); II != EE; ++II)
916 assert(*II != D && "Inst occurs in data structures");
919 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(),
920 E = ReverseNonLocalDeps.end();
922 assert(I->first != D && "Inst occurs in data structures");
923 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
924 EE = I->second.end(); II != EE; ++II)
925 assert(*II != D && "Inst occurs in data structures");
928 for (ReverseNonLocalPtrDepTy::const_iterator
929 I = ReverseNonLocalPtrDeps.begin(),
930 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) {
931 assert(I->first != D && "Inst occurs in rev NLPD map");
933 for (SmallPtrSet<void*, 4>::const_iterator II = I->second.begin(),
934 E = I->second.end(); II != E; ++II)
935 assert(*II != ValueIsLoadPair(D, false).getOpaqueValue() &&
936 *II != ValueIsLoadPair(D, true).getOpaqueValue() &&
937 "Inst occurs in ReverseNonLocalPtrDeps map");