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/LLVMContext.h"
23 #include "llvm/Analysis/AliasAnalysis.h"
24 #include "llvm/Analysis/Dominators.h"
25 #include "llvm/Analysis/InstructionSimplify.h"
26 #include "llvm/Analysis/MemoryBuiltins.h"
27 #include "llvm/Analysis/PHITransAddr.h"
28 #include "llvm/Analysis/ValueTracking.h"
29 #include "llvm/ADT/Statistic.h"
30 #include "llvm/ADT/STLExtras.h"
31 #include "llvm/Support/PredIteratorCache.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/Target/TargetData.h"
36 STATISTIC(NumCacheNonLocal, "Number of fully cached non-local responses");
37 STATISTIC(NumCacheDirtyNonLocal, "Number of dirty cached non-local responses");
38 STATISTIC(NumUncacheNonLocal, "Number of uncached non-local responses");
40 STATISTIC(NumCacheNonLocalPtr,
41 "Number of fully cached non-local ptr responses");
42 STATISTIC(NumCacheDirtyNonLocalPtr,
43 "Number of cached, but dirty, non-local ptr responses");
44 STATISTIC(NumUncacheNonLocalPtr,
45 "Number of uncached non-local ptr responses");
46 STATISTIC(NumCacheCompleteNonLocalPtr,
47 "Number of block queries that were completely cached");
49 // Limit for the number of instructions to scan in a block.
50 // FIXME: Figure out what a sane value is for this.
51 // (500 is relatively insane.)
52 static const int BlockScanLimit = 500;
54 char MemoryDependenceAnalysis::ID = 0;
56 // Register this pass...
57 INITIALIZE_PASS_BEGIN(MemoryDependenceAnalysis, "memdep",
58 "Memory Dependence Analysis", false, true)
59 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
60 INITIALIZE_PASS_END(MemoryDependenceAnalysis, "memdep",
61 "Memory Dependence Analysis", false, true)
63 MemoryDependenceAnalysis::MemoryDependenceAnalysis()
64 : FunctionPass(ID), PredCache(0) {
65 initializeMemoryDependenceAnalysisPass(*PassRegistry::getPassRegistry());
67 MemoryDependenceAnalysis::~MemoryDependenceAnalysis() {
70 /// Clean up memory in between runs
71 void MemoryDependenceAnalysis::releaseMemory() {
74 NonLocalPointerDeps.clear();
75 ReverseLocalDeps.clear();
76 ReverseNonLocalDeps.clear();
77 ReverseNonLocalPtrDeps.clear();
83 /// getAnalysisUsage - Does not modify anything. It uses Alias Analysis.
85 void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
87 AU.addRequiredTransitive<AliasAnalysis>();
90 bool MemoryDependenceAnalysis::runOnFunction(Function &) {
91 AA = &getAnalysis<AliasAnalysis>();
92 TD = getAnalysisIfAvailable<TargetData>();
93 DT = getAnalysisIfAvailable<DominatorTree>();
95 PredCache.reset(new PredIteratorCache());
99 /// RemoveFromReverseMap - This is a helper function that removes Val from
100 /// 'Inst's set in ReverseMap. If the set becomes empty, remove Inst's entry.
101 template <typename KeyTy>
102 static void RemoveFromReverseMap(DenseMap<Instruction*,
103 SmallPtrSet<KeyTy, 4> > &ReverseMap,
104 Instruction *Inst, KeyTy Val) {
105 typename DenseMap<Instruction*, SmallPtrSet<KeyTy, 4> >::iterator
106 InstIt = ReverseMap.find(Inst);
107 assert(InstIt != ReverseMap.end() && "Reverse map out of sync?");
108 bool Found = InstIt->second.erase(Val);
109 assert(Found && "Invalid reverse map!"); (void)Found;
110 if (InstIt->second.empty())
111 ReverseMap.erase(InstIt);
114 /// GetLocation - If the given instruction references a specific memory
115 /// location, fill in Loc with the details, otherwise set Loc.Ptr to null.
116 /// Return a ModRefInfo value describing the general behavior of the
119 AliasAnalysis::ModRefResult GetLocation(const Instruction *Inst,
120 AliasAnalysis::Location &Loc,
122 if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
123 if (LI->isUnordered()) {
124 Loc = AA->getLocation(LI);
125 return AliasAnalysis::Ref;
126 } else if (LI->getOrdering() == Monotonic) {
127 Loc = AA->getLocation(LI);
128 return AliasAnalysis::ModRef;
130 Loc = AliasAnalysis::Location();
131 return AliasAnalysis::ModRef;
134 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
135 if (SI->isUnordered()) {
136 Loc = AA->getLocation(SI);
137 return AliasAnalysis::Mod;
138 } else if (SI->getOrdering() == Monotonic) {
139 Loc = AA->getLocation(SI);
140 return AliasAnalysis::ModRef;
142 Loc = AliasAnalysis::Location();
143 return AliasAnalysis::ModRef;
146 if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
147 Loc = AA->getLocation(V);
148 return AliasAnalysis::ModRef;
151 if (const CallInst *CI = isFreeCall(Inst)) {
152 // calls to free() deallocate the entire structure
153 Loc = AliasAnalysis::Location(CI->getArgOperand(0));
154 return AliasAnalysis::Mod;
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))
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))
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;
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;
189 /// getCallSiteDependencyFrom - Private helper for finding the local
190 /// dependencies of a call site.
191 MemDepResult MemoryDependenceAnalysis::
192 getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
193 BasicBlock::iterator ScanIt, BasicBlock *BB) {
194 unsigned Limit = BlockScanLimit;
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.
202 return MemDepResult::getUnknown();
204 Instruction *Inst = --ScanIt;
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);
210 // A simple instruction.
211 if (AA->getModRefInfo(CS, Loc) != AliasAnalysis::NoModRef)
212 return MemDepResult::getClobber(Inst);
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);
228 // Otherwise if the two calls don't interact (e.g. InstCS is readnone)
232 return MemDepResult::getClobber(Inst);
237 // No dependence found. If this is the entry block of the function, it is
238 // unknown, otherwise it is non-local.
239 if (BB != &BB->getParent()->getEntryBlock())
240 return MemDepResult::getNonLocal();
241 return MemDepResult::getNonFuncLocal();
244 /// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
245 /// would fully overlap MemLoc if done as a wider legal integer load.
247 /// MemLocBase, MemLocOffset are lazily computed here the first time the
248 /// base/offs of memloc is needed.
250 isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc,
251 const Value *&MemLocBase,
254 const TargetData *TD) {
255 // If we have no target data, we can't do this.
256 if (TD == 0) return false;
258 // If we haven't already computed the base/offset of MemLoc, do so now.
260 MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, *TD);
262 unsigned Size = MemoryDependenceAnalysis::
263 getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size,
268 /// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that
269 /// looks at a memory location for a load (specified by MemLocBase, Offs,
270 /// and Size) and compares it against a load. If the specified load could
271 /// be safely widened to a larger integer load that is 1) still efficient,
272 /// 2) safe for the target, and 3) would provide the specified memory
273 /// location value, then this function returns the size in bytes of the
274 /// load width to use. If not, this returns zero.
275 unsigned MemoryDependenceAnalysis::
276 getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
277 unsigned MemLocSize, const LoadInst *LI,
278 const TargetData &TD) {
279 // We can only extend simple integer loads.
280 if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0;
282 // Get the base of this load.
284 const Value *LIBase =
285 GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, TD);
287 // If the two pointers are not based on the same pointer, we can't tell that
289 if (LIBase != MemLocBase) return 0;
291 // Okay, the two values are based on the same pointer, but returned as
292 // no-alias. This happens when we have things like two byte loads at "P+1"
293 // and "P+3". Check to see if increasing the size of the "LI" load up to its
294 // alignment (or the largest native integer type) will allow us to load all
295 // the bits required by MemLoc.
297 // If MemLoc is before LI, then no widening of LI will help us out.
298 if (MemLocOffs < LIOffs) return 0;
300 // Get the alignment of the load in bytes. We assume that it is safe to load
301 // any legal integer up to this size without a problem. For example, if we're
302 // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can
303 // widen it up to an i32 load. If it is known 2-byte aligned, we can widen it
305 unsigned LoadAlign = LI->getAlignment();
307 int64_t MemLocEnd = MemLocOffs+MemLocSize;
309 // If no amount of rounding up will let MemLoc fit into LI, then bail out.
310 if (LIOffs+LoadAlign < MemLocEnd) return 0;
312 // This is the size of the load to try. Start with the next larger power of
314 unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U;
315 NewLoadByteSize = NextPowerOf2(NewLoadByteSize);
318 // If this load size is bigger than our known alignment or would not fit
319 // into a native integer register, then we fail.
320 if (NewLoadByteSize > LoadAlign ||
321 !TD.fitsInLegalInteger(NewLoadByteSize*8))
324 if (LIOffs+NewLoadByteSize > MemLocEnd &&
325 LI->getParent()->getParent()->hasFnAttr(Attribute::AddressSafety)) {
326 // We will be reading past the location accessed by the original program.
327 // While this is safe in a regular build, Address Safety analysis tools
328 // may start reporting false warnings. So, don't do widening.
332 // If a load of this width would include all of MemLoc, then we succeed.
333 if (LIOffs+NewLoadByteSize >= MemLocEnd)
334 return NewLoadByteSize;
336 NewLoadByteSize <<= 1;
340 /// getPointerDependencyFrom - Return the instruction on which a memory
341 /// location depends. If isLoad is true, this routine ignores may-aliases with
342 /// read-only operations. If isLoad is false, this routine ignores may-aliases
343 /// with reads from read-only locations.
344 MemDepResult MemoryDependenceAnalysis::
345 getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
346 BasicBlock::iterator ScanIt, BasicBlock *BB) {
348 const Value *MemLocBase = 0;
349 int64_t MemLocOffset = 0;
351 unsigned Limit = BlockScanLimit;
353 // Walk backwards through the basic block, looking for dependencies.
354 while (ScanIt != BB->begin()) {
355 // Limit the amount of scanning we do so we don't end up with quadratic
356 // running time on extreme testcases.
359 return MemDepResult::getUnknown();
361 Instruction *Inst = --ScanIt;
363 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
364 // Debug intrinsics don't (and can't) cause dependences.
365 if (isa<DbgInfoIntrinsic>(II)) continue;
367 // If we reach a lifetime begin or end marker, then the query ends here
368 // because the value is undefined.
369 if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
370 // FIXME: This only considers queries directly on the invariant-tagged
371 // pointer, not on query pointers that are indexed off of them. It'd
372 // be nice to handle that at some point (the right approach is to use
373 // GetPointerBaseWithConstantOffset).
374 if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)),
376 return MemDepResult::getDef(II);
381 // Values depend on loads if the pointers are must aliased. This means that
382 // a load depends on another must aliased load from the same value.
383 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
384 // Atomic loads have complications involved.
385 // FIXME: This is overly conservative.
386 if (!LI->isUnordered())
387 return MemDepResult::getClobber(LI);
389 AliasAnalysis::Location LoadLoc = AA->getLocation(LI);
391 // If we found a pointer, check if it could be the same as our pointer.
392 AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc);
395 if (R == AliasAnalysis::NoAlias) {
396 // If this is an over-aligned integer load (for example,
397 // "load i8* %P, align 4") see if it would obviously overlap with the
398 // queried location if widened to a larger load (e.g. if the queried
399 // location is 1 byte at P+1). If so, return it as a load/load
400 // clobber result, allowing the client to decide to widen the load if
402 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
403 if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() &&
404 isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase,
405 MemLocOffset, LI, TD))
406 return MemDepResult::getClobber(Inst);
411 // Must aliased loads are defs of each other.
412 if (R == AliasAnalysis::MustAlias)
413 return MemDepResult::getDef(Inst);
415 #if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads
416 // in terms of clobbering loads, but since it does this by looking
417 // at the clobbering load directly, it doesn't know about any
418 // phi translation that may have happened along the way.
420 // If we have a partial alias, then return this as a clobber for the
422 if (R == AliasAnalysis::PartialAlias)
423 return MemDepResult::getClobber(Inst);
426 // Random may-alias loads don't depend on each other without a
431 // Stores don't depend on other no-aliased accesses.
432 if (R == AliasAnalysis::NoAlias)
435 // Stores don't alias loads from read-only memory.
436 if (AA->pointsToConstantMemory(LoadLoc))
439 // Stores depend on may/must aliased loads.
440 return MemDepResult::getDef(Inst);
443 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
444 // Atomic stores have complications involved.
445 // FIXME: This is overly conservative.
446 if (!SI->isUnordered())
447 return MemDepResult::getClobber(SI);
449 // If alias analysis can tell that this store is guaranteed to not modify
450 // the query pointer, ignore it. Use getModRefInfo to handle cases where
451 // the query pointer points to constant memory etc.
452 if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef)
455 // Ok, this store might clobber the query pointer. Check to see if it is
456 // a must alias: in this case, we want to return this as a def.
457 AliasAnalysis::Location StoreLoc = AA->getLocation(SI);
459 // If we found a pointer, check if it could be the same as our pointer.
460 AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc);
462 if (R == AliasAnalysis::NoAlias)
464 if (R == AliasAnalysis::MustAlias)
465 return MemDepResult::getDef(Inst);
466 return MemDepResult::getClobber(Inst);
469 // If this is an allocation, and if we know that the accessed pointer is to
470 // the allocation, return Def. This means that there is no dependence and
471 // the access can be optimized based on that. For example, a load could
473 // Note: Only determine this to be a malloc if Inst is the malloc call, not
474 // a subsequent bitcast of the malloc call result. There can be stores to
475 // the malloced memory between the malloc call and its bitcast uses, and we
476 // need to continue scanning until the malloc call.
477 if (isa<AllocaInst>(Inst) ||
478 (isa<CallInst>(Inst) && extractMallocCall(Inst))) {
479 const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, TD);
481 if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
482 return MemDepResult::getDef(Inst);
486 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
487 AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc);
488 // If necessary, perform additional analysis.
489 if (MR == AliasAnalysis::ModRef)
490 MR = AA->callCapturesBefore(Inst, MemLoc, DT);
492 case AliasAnalysis::NoModRef:
493 // If the call has no effect on the queried pointer, just ignore it.
495 case AliasAnalysis::Mod:
496 return MemDepResult::getClobber(Inst);
497 case AliasAnalysis::Ref:
498 // If the call is known to never store to the pointer, and if this is a
499 // load query, we can safely ignore it (scan past it).
503 // Otherwise, there is a potential dependence. Return a clobber.
504 return MemDepResult::getClobber(Inst);
508 // No dependence found. If this is the entry block of the function, it is
509 // unknown, otherwise it is non-local.
510 if (BB != &BB->getParent()->getEntryBlock())
511 return MemDepResult::getNonLocal();
512 return MemDepResult::getNonFuncLocal();
515 /// getDependency - Return the instruction on which a memory operation
517 MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
518 Instruction *ScanPos = QueryInst;
520 // Check for a cached result
521 MemDepResult &LocalCache = LocalDeps[QueryInst];
523 // If the cached entry is non-dirty, just return it. Note that this depends
524 // on MemDepResult's default constructing to 'dirty'.
525 if (!LocalCache.isDirty())
528 // Otherwise, if we have a dirty entry, we know we can start the scan at that
529 // instruction, which may save us some work.
530 if (Instruction *Inst = LocalCache.getInst()) {
533 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst);
536 BasicBlock *QueryParent = QueryInst->getParent();
539 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
540 // No dependence found. If this is the entry block of the function, it is
541 // unknown, otherwise it is non-local.
542 if (QueryParent != &QueryParent->getParent()->getEntryBlock())
543 LocalCache = MemDepResult::getNonLocal();
545 LocalCache = MemDepResult::getNonFuncLocal();
547 AliasAnalysis::Location MemLoc;
548 AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
550 // If we can do a pointer scan, make it happen.
551 bool isLoad = !(MR & AliasAnalysis::Mod);
552 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst))
553 isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start;
555 LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos,
557 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
558 CallSite QueryCS(QueryInst);
559 bool isReadOnly = AA->onlyReadsMemory(QueryCS);
560 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos,
563 // Non-memory instruction.
564 LocalCache = MemDepResult::getUnknown();
567 // Remember the result!
568 if (Instruction *I = LocalCache.getInst())
569 ReverseLocalDeps[I].insert(QueryInst);
575 /// AssertSorted - This method is used when -debug is specified to verify that
576 /// cache arrays are properly kept sorted.
577 static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
579 if (Count == -1) Count = Cache.size();
580 if (Count == 0) return;
582 for (unsigned i = 1; i != unsigned(Count); ++i)
583 assert(!(Cache[i] < Cache[i-1]) && "Cache isn't sorted!");
587 /// getNonLocalCallDependency - Perform a full dependency query for the
588 /// specified call, returning the set of blocks that the value is
589 /// potentially live across. The returned set of results will include a
590 /// "NonLocal" result for all blocks where the value is live across.
592 /// This method assumes the instruction returns a "NonLocal" dependency
593 /// within its own block.
595 /// This returns a reference to an internal data structure that may be
596 /// invalidated on the next non-local query or when an instruction is
597 /// removed. Clients must copy this data if they want it around longer than
599 const MemoryDependenceAnalysis::NonLocalDepInfo &
600 MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
601 assert(getDependency(QueryCS.getInstruction()).isNonLocal() &&
602 "getNonLocalCallDependency should only be used on calls with non-local deps!");
603 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()];
604 NonLocalDepInfo &Cache = CacheP.first;
606 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In
607 /// the cached case, this can happen due to instructions being deleted etc. In
608 /// the uncached case, this starts out as the set of predecessors we care
610 SmallVector<BasicBlock*, 32> DirtyBlocks;
612 if (!Cache.empty()) {
613 // Okay, we have a cache entry. If we know it is not dirty, just return it
614 // with no computation.
615 if (!CacheP.second) {
620 // If we already have a partially computed set of results, scan them to
621 // determine what is dirty, seeding our initial DirtyBlocks worklist.
622 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end();
624 if (I->getResult().isDirty())
625 DirtyBlocks.push_back(I->getBB());
627 // Sort the cache so that we can do fast binary search lookups below.
628 std::sort(Cache.begin(), Cache.end());
630 ++NumCacheDirtyNonLocal;
631 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: "
632 // << Cache.size() << " cached: " << *QueryInst;
634 // Seed DirtyBlocks with each of the preds of QueryInst's block.
635 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent();
636 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI)
637 DirtyBlocks.push_back(*PI);
638 ++NumUncacheNonLocal;
641 // isReadonlyCall - If this is a read-only call, we can be more aggressive.
642 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS);
644 SmallPtrSet<BasicBlock*, 64> Visited;
646 unsigned NumSortedEntries = Cache.size();
647 DEBUG(AssertSorted(Cache));
649 // Iterate while we still have blocks to update.
650 while (!DirtyBlocks.empty()) {
651 BasicBlock *DirtyBB = DirtyBlocks.back();
652 DirtyBlocks.pop_back();
654 // Already processed this block?
655 if (!Visited.insert(DirtyBB))
658 // Do a binary search to see if we already have an entry for this block in
659 // the cache set. If so, find it.
660 DEBUG(AssertSorted(Cache, NumSortedEntries));
661 NonLocalDepInfo::iterator Entry =
662 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries,
663 NonLocalDepEntry(DirtyBB));
664 if (Entry != Cache.begin() && prior(Entry)->getBB() == DirtyBB)
667 NonLocalDepEntry *ExistingResult = 0;
668 if (Entry != Cache.begin()+NumSortedEntries &&
669 Entry->getBB() == DirtyBB) {
670 // If we already have an entry, and if it isn't already dirty, the block
672 if (!Entry->getResult().isDirty())
675 // Otherwise, remember this slot so we can update the value.
676 ExistingResult = &*Entry;
679 // If the dirty entry has a pointer, start scanning from it so we don't have
680 // to rescan the entire block.
681 BasicBlock::iterator ScanPos = DirtyBB->end();
682 if (ExistingResult) {
683 if (Instruction *Inst = ExistingResult->getResult().getInst()) {
685 // We're removing QueryInst's use of Inst.
686 RemoveFromReverseMap(ReverseNonLocalDeps, Inst,
687 QueryCS.getInstruction());
691 // Find out if this block has a local dependency for QueryInst.
694 if (ScanPos != DirtyBB->begin()) {
695 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
696 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
697 // No dependence found. If this is the entry block of the function, it is
698 // a clobber, otherwise it is unknown.
699 Dep = MemDepResult::getNonLocal();
701 Dep = MemDepResult::getNonFuncLocal();
704 // If we had a dirty entry for the block, update it. Otherwise, just add
707 ExistingResult->setResult(Dep);
709 Cache.push_back(NonLocalDepEntry(DirtyBB, Dep));
711 // If the block has a dependency (i.e. it isn't completely transparent to
712 // the value), remember the association!
713 if (!Dep.isNonLocal()) {
714 // Keep the ReverseNonLocalDeps map up to date so we can efficiently
715 // update this when we remove instructions.
716 if (Instruction *Inst = Dep.getInst())
717 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction());
720 // If the block *is* completely transparent to the load, we need to check
721 // the predecessors of this block. Add them to our worklist.
722 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI)
723 DirtyBlocks.push_back(*PI);
730 /// getNonLocalPointerDependency - Perform a full dependency query for an
731 /// access to the specified (non-volatile) memory location, returning the
732 /// set of instructions that either define or clobber the value.
734 /// This method assumes the pointer has a "NonLocal" dependency within its
737 void MemoryDependenceAnalysis::
738 getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad,
740 SmallVectorImpl<NonLocalDepResult> &Result) {
741 assert(Loc.Ptr->getType()->isPointerTy() &&
742 "Can't get pointer deps of a non-pointer!");
745 PHITransAddr Address(const_cast<Value *>(Loc.Ptr), TD);
747 // This is the set of blocks we've inspected, and the pointer we consider in
748 // each block. Because of critical edges, we currently bail out if querying
749 // a block with multiple different pointers. This can happen during PHI
751 DenseMap<BasicBlock*, Value*> Visited;
752 if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB,
753 Result, Visited, true))
756 Result.push_back(NonLocalDepResult(FromBB,
757 MemDepResult::getUnknown(),
758 const_cast<Value *>(Loc.Ptr)));
761 /// GetNonLocalInfoForBlock - Compute the memdep value for BB with
762 /// Pointer/PointeeSize using either cached information in Cache or by doing a
763 /// lookup (which may use dirty cache info if available). If we do a lookup,
764 /// add the result to the cache.
765 MemDepResult MemoryDependenceAnalysis::
766 GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
767 bool isLoad, BasicBlock *BB,
768 NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
770 // Do a binary search to see if we already have an entry for this block in
771 // the cache set. If so, find it.
772 NonLocalDepInfo::iterator Entry =
773 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries,
774 NonLocalDepEntry(BB));
775 if (Entry != Cache->begin() && (Entry-1)->getBB() == BB)
778 NonLocalDepEntry *ExistingResult = 0;
779 if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB)
780 ExistingResult = &*Entry;
782 // If we have a cached entry, and it is non-dirty, use it as the value for
784 if (ExistingResult && !ExistingResult->getResult().isDirty()) {
785 ++NumCacheNonLocalPtr;
786 return ExistingResult->getResult();
789 // Otherwise, we have to scan for the value. If we have a dirty cache
790 // entry, start scanning from its position, otherwise we scan from the end
792 BasicBlock::iterator ScanPos = BB->end();
793 if (ExistingResult && ExistingResult->getResult().getInst()) {
794 assert(ExistingResult->getResult().getInst()->getParent() == BB &&
795 "Instruction invalidated?");
796 ++NumCacheDirtyNonLocalPtr;
797 ScanPos = ExistingResult->getResult().getInst();
799 // Eliminating the dirty entry from 'Cache', so update the reverse info.
800 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
801 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey);
803 ++NumUncacheNonLocalPtr;
806 // Scan the block for the dependency.
807 MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB);
809 // If we had a dirty entry for the block, update it. Otherwise, just add
812 ExistingResult->setResult(Dep);
814 Cache->push_back(NonLocalDepEntry(BB, Dep));
816 // If the block has a dependency (i.e. it isn't completely transparent to
817 // the value), remember the reverse association because we just added it
819 if (!Dep.isDef() && !Dep.isClobber())
822 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
823 // update MemDep when we remove instructions.
824 Instruction *Inst = Dep.getInst();
825 assert(Inst && "Didn't depend on anything?");
826 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
827 ReverseNonLocalPtrDeps[Inst].insert(CacheKey);
831 /// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain
832 /// number of elements in the array that are already properly ordered. This is
833 /// optimized for the case when only a few entries are added.
835 SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
836 unsigned NumSortedEntries) {
837 switch (Cache.size() - NumSortedEntries) {
839 // done, no new entries.
842 // Two new entries, insert the last one into place.
843 NonLocalDepEntry Val = Cache.back();
845 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
846 std::upper_bound(Cache.begin(), Cache.end()-1, Val);
847 Cache.insert(Entry, Val);
851 // One new entry, Just insert the new value at the appropriate position.
852 if (Cache.size() != 1) {
853 NonLocalDepEntry Val = Cache.back();
855 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
856 std::upper_bound(Cache.begin(), Cache.end(), Val);
857 Cache.insert(Entry, Val);
861 // Added many values, do a full scale sort.
862 std::sort(Cache.begin(), Cache.end());
867 /// getNonLocalPointerDepFromBB - Perform a dependency query based on
868 /// pointer/pointeesize starting at the end of StartBB. Add any clobber/def
869 /// results to the results vector and keep track of which blocks are visited in
872 /// This has special behavior for the first block queries (when SkipFirstBlock
873 /// is true). In this special case, it ignores the contents of the specified
874 /// block and starts returning dependence info for its predecessors.
876 /// This function returns false on success, or true to indicate that it could
877 /// not compute dependence information for some reason. This should be treated
878 /// as a clobber dependence on the first instruction in the predecessor block.
879 bool MemoryDependenceAnalysis::
880 getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
881 const AliasAnalysis::Location &Loc,
882 bool isLoad, BasicBlock *StartBB,
883 SmallVectorImpl<NonLocalDepResult> &Result,
884 DenseMap<BasicBlock*, Value*> &Visited,
885 bool SkipFirstBlock) {
887 // Look up the cached info for Pointer.
888 ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad);
890 // Set up a temporary NLPI value. If the map doesn't yet have an entry for
891 // CacheKey, this value will be inserted as the associated value. Otherwise,
892 // it'll be ignored, and we'll have to check to see if the cached size and
893 // tbaa tag are consistent with the current query.
894 NonLocalPointerInfo InitialNLPI;
895 InitialNLPI.Size = Loc.Size;
896 InitialNLPI.TBAATag = Loc.TBAATag;
898 // Get the NLPI for CacheKey, inserting one into the map if it doesn't
900 std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair =
901 NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI));
902 NonLocalPointerInfo *CacheInfo = &Pair.first->second;
904 // If we already have a cache entry for this CacheKey, we may need to do some
905 // work to reconcile the cache entry and the current query.
907 if (CacheInfo->Size < Loc.Size) {
908 // The query's Size is greater than the cached one. Throw out the
909 // cached data and proceed with the query at the greater size.
910 CacheInfo->Pair = BBSkipFirstBlockPair();
911 CacheInfo->Size = Loc.Size;
912 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
913 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
914 if (Instruction *Inst = DI->getResult().getInst())
915 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
916 CacheInfo->NonLocalDeps.clear();
917 } else if (CacheInfo->Size > Loc.Size) {
918 // This query's Size is less than the cached one. Conservatively restart
919 // the query using the greater size.
920 return getNonLocalPointerDepFromBB(Pointer,
921 Loc.getWithNewSize(CacheInfo->Size),
922 isLoad, StartBB, Result, Visited,
926 // If the query's TBAATag is inconsistent with the cached one,
927 // conservatively throw out the cached data and restart the query with
929 if (CacheInfo->TBAATag != Loc.TBAATag) {
930 if (CacheInfo->TBAATag) {
931 CacheInfo->Pair = BBSkipFirstBlockPair();
932 CacheInfo->TBAATag = 0;
933 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
934 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
935 if (Instruction *Inst = DI->getResult().getInst())
936 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
937 CacheInfo->NonLocalDeps.clear();
940 return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(),
941 isLoad, StartBB, Result, Visited,
946 NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps;
948 // If we have valid cached information for exactly the block we are
949 // investigating, just return it with no recomputation.
950 if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
951 // We have a fully cached result for this query then we can just return the
952 // cached results and populate the visited set. However, we have to verify
953 // that we don't already have conflicting results for these blocks. Check
954 // to ensure that if a block in the results set is in the visited set that
955 // it was for the same pointer query.
956 if (!Visited.empty()) {
957 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
959 DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->getBB());
960 if (VI == Visited.end() || VI->second == Pointer.getAddr())
963 // We have a pointer mismatch in a block. Just return clobber, saying
964 // that something was clobbered in this result. We could also do a
965 // non-fully cached query, but there is little point in doing this.
970 Value *Addr = Pointer.getAddr();
971 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
973 Visited.insert(std::make_pair(I->getBB(), Addr));
974 if (!I->getResult().isNonLocal())
975 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr));
977 ++NumCacheCompleteNonLocalPtr;
981 // Otherwise, either this is a new block, a block with an invalid cache
982 // pointer or one that we're about to invalidate by putting more info into it
983 // than its valid cache info. If empty, the result will be valid cache info,
984 // otherwise it isn't.
986 CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
988 CacheInfo->Pair = BBSkipFirstBlockPair();
990 SmallVector<BasicBlock*, 32> Worklist;
991 Worklist.push_back(StartBB);
993 // PredList used inside loop.
994 SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList;
996 // Keep track of the entries that we know are sorted. Previously cached
997 // entries will all be sorted. The entries we add we only sort on demand (we
998 // don't insert every element into its sorted position). We know that we
999 // won't get any reuse from currently inserted values, because we don't
1000 // revisit blocks after we insert info for them.
1001 unsigned NumSortedEntries = Cache->size();
1002 DEBUG(AssertSorted(*Cache));
1004 while (!Worklist.empty()) {
1005 BasicBlock *BB = Worklist.pop_back_val();
1007 // Skip the first block if we have it.
1008 if (!SkipFirstBlock) {
1009 // Analyze the dependency of *Pointer in FromBB. See if we already have
1011 assert(Visited.count(BB) && "Should check 'visited' before adding to WL");
1013 // Get the dependency info for Pointer in BB. If we have cached
1014 // information, we will use it, otherwise we compute it.
1015 DEBUG(AssertSorted(*Cache, NumSortedEntries));
1016 MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache,
1019 // If we got a Def or Clobber, add this to the list of results.
1020 if (!Dep.isNonLocal()) {
1021 Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr()));
1026 // If 'Pointer' is an instruction defined in this block, then we need to do
1027 // phi translation to change it into a value live in the predecessor block.
1028 // If not, we just add the predecessors to the worklist and scan them with
1029 // the same Pointer.
1030 if (!Pointer.NeedsPHITranslationFromBlock(BB)) {
1031 SkipFirstBlock = false;
1032 SmallVector<BasicBlock*, 16> NewBlocks;
1033 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1034 // Verify that we haven't looked at this block yet.
1035 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1036 InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr()));
1037 if (InsertRes.second) {
1038 // First time we've looked at *PI.
1039 NewBlocks.push_back(*PI);
1043 // If we have seen this block before, but it was with a different
1044 // pointer then we have a phi translation failure and we have to treat
1045 // this as a clobber.
1046 if (InsertRes.first->second != Pointer.getAddr()) {
1047 // Make sure to clean up the Visited map before continuing on to
1048 // PredTranslationFailure.
1049 for (unsigned i = 0; i < NewBlocks.size(); i++)
1050 Visited.erase(NewBlocks[i]);
1051 goto PredTranslationFailure;
1054 Worklist.append(NewBlocks.begin(), NewBlocks.end());
1058 // We do need to do phi translation, if we know ahead of time we can't phi
1059 // translate this value, don't even try.
1060 if (!Pointer.IsPotentiallyPHITranslatable())
1061 goto PredTranslationFailure;
1063 // We may have added values to the cache list before this PHI translation.
1064 // If so, we haven't done anything to ensure that the cache remains sorted.
1065 // Sort it now (if needed) so that recursive invocations of
1066 // getNonLocalPointerDepFromBB and other routines that could reuse the cache
1067 // value will only see properly sorted cache arrays.
1068 if (Cache && NumSortedEntries != Cache->size()) {
1069 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1070 NumSortedEntries = Cache->size();
1075 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1076 BasicBlock *Pred = *PI;
1077 PredList.push_back(std::make_pair(Pred, Pointer));
1079 // Get the PHI translated pointer in this predecessor. This can fail if
1080 // not translatable, in which case the getAddr() returns null.
1081 PHITransAddr &PredPointer = PredList.back().second;
1082 PredPointer.PHITranslateValue(BB, Pred, 0);
1084 Value *PredPtrVal = PredPointer.getAddr();
1086 // Check to see if we have already visited this pred block with another
1087 // pointer. If so, we can't do this lookup. This failure can occur
1088 // with PHI translation when a critical edge exists and the PHI node in
1089 // the successor translates to a pointer value different than the
1090 // pointer the block was first analyzed with.
1091 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1092 InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal));
1094 if (!InsertRes.second) {
1095 // We found the pred; take it off the list of preds to visit.
1096 PredList.pop_back();
1098 // If the predecessor was visited with PredPtr, then we already did
1099 // the analysis and can ignore it.
1100 if (InsertRes.first->second == PredPtrVal)
1103 // Otherwise, the block was previously analyzed with a different
1104 // pointer. We can't represent the result of this case, so we just
1105 // treat this as a phi translation failure.
1107 // Make sure to clean up the Visited map before continuing on to
1108 // PredTranslationFailure.
1109 for (unsigned i = 0; i < PredList.size(); i++)
1110 Visited.erase(PredList[i].first);
1112 goto PredTranslationFailure;
1116 // Actually process results here; this need to be a separate loop to avoid
1117 // calling getNonLocalPointerDepFromBB for blocks we don't want to return
1118 // any results for. (getNonLocalPointerDepFromBB will modify our
1119 // datastructures in ways the code after the PredTranslationFailure label
1121 for (unsigned i = 0; i < PredList.size(); i++) {
1122 BasicBlock *Pred = PredList[i].first;
1123 PHITransAddr &PredPointer = PredList[i].second;
1124 Value *PredPtrVal = PredPointer.getAddr();
1126 bool CanTranslate = true;
1127 // If PHI translation was unable to find an available pointer in this
1128 // predecessor, then we have to assume that the pointer is clobbered in
1129 // that predecessor. We can still do PRE of the load, which would insert
1130 // a computation of the pointer in this predecessor.
1131 if (PredPtrVal == 0)
1132 CanTranslate = false;
1134 // FIXME: it is entirely possible that PHI translating will end up with
1135 // the same value. Consider PHI translating something like:
1136 // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need*
1137 // to recurse here, pedantically speaking.
1139 // If getNonLocalPointerDepFromBB fails here, that means the cached
1140 // result conflicted with the Visited list; we have to conservatively
1141 // assume it is unknown, but this also does not block PRE of the load.
1142 if (!CanTranslate ||
1143 getNonLocalPointerDepFromBB(PredPointer,
1144 Loc.getWithNewPtr(PredPtrVal),
1147 // Add the entry to the Result list.
1148 NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal);
1149 Result.push_back(Entry);
1151 // Since we had a phi translation failure, the cache for CacheKey won't
1152 // include all of the entries that we need to immediately satisfy future
1153 // queries. Mark this in NonLocalPointerDeps by setting the
1154 // BBSkipFirstBlockPair pointer to null. This requires reuse of the
1155 // cached value to do more work but not miss the phi trans failure.
1156 NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey];
1157 NLPI.Pair = BBSkipFirstBlockPair();
1162 // Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
1163 CacheInfo = &NonLocalPointerDeps[CacheKey];
1164 Cache = &CacheInfo->NonLocalDeps;
1165 NumSortedEntries = Cache->size();
1167 // Since we did phi translation, the "Cache" set won't contain all of the
1168 // results for the query. This is ok (we can still use it to accelerate
1169 // specific block queries) but we can't do the fastpath "return all
1170 // results from the set" Clear out the indicator for this.
1171 CacheInfo->Pair = BBSkipFirstBlockPair();
1172 SkipFirstBlock = false;
1175 PredTranslationFailure:
1176 // The following code is "failure"; we can't produce a sane translation
1177 // for the given block. It assumes that we haven't modified any of
1178 // our datastructures while processing the current block.
1181 // Refresh the CacheInfo/Cache pointer if it got invalidated.
1182 CacheInfo = &NonLocalPointerDeps[CacheKey];
1183 Cache = &CacheInfo->NonLocalDeps;
1184 NumSortedEntries = Cache->size();
1187 // Since we failed phi translation, the "Cache" set won't contain all of the
1188 // results for the query. This is ok (we can still use it to accelerate
1189 // specific block queries) but we can't do the fastpath "return all
1190 // results from the set". Clear out the indicator for this.
1191 CacheInfo->Pair = BBSkipFirstBlockPair();
1193 // If *nothing* works, mark the pointer as unknown.
1195 // If this is the magic first block, return this as a clobber of the whole
1196 // incoming value. Since we can't phi translate to one of the predecessors,
1197 // we have to bail out.
1201 for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) {
1202 assert(I != Cache->rend() && "Didn't find current block??");
1203 if (I->getBB() != BB)
1206 assert(I->getResult().isNonLocal() &&
1207 "Should only be here with transparent block");
1208 I->setResult(MemDepResult::getUnknown());
1209 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(),
1210 Pointer.getAddr()));
1215 // Okay, we're done now. If we added new values to the cache, re-sort it.
1216 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1217 DEBUG(AssertSorted(*Cache));
1221 /// RemoveCachedNonLocalPointerDependencies - If P exists in
1222 /// CachedNonLocalPointerInfo, remove it.
1223 void MemoryDependenceAnalysis::
1224 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) {
1225 CachedNonLocalPointerInfo::iterator It =
1226 NonLocalPointerDeps.find(P);
1227 if (It == NonLocalPointerDeps.end()) return;
1229 // Remove all of the entries in the BB->val map. This involves removing
1230 // instructions from the reverse map.
1231 NonLocalDepInfo &PInfo = It->second.NonLocalDeps;
1233 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
1234 Instruction *Target = PInfo[i].getResult().getInst();
1235 if (Target == 0) continue; // Ignore non-local dep results.
1236 assert(Target->getParent() == PInfo[i].getBB());
1238 // Eliminating the dirty entry from 'Cache', so update the reverse info.
1239 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P);
1242 // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo).
1243 NonLocalPointerDeps.erase(It);
1247 /// invalidateCachedPointerInfo - This method is used to invalidate cached
1248 /// information about the specified pointer, because it may be too
1249 /// conservative in memdep. This is an optional call that can be used when
1250 /// the client detects an equivalence between the pointer and some other
1251 /// value and replaces the other value with ptr. This can make Ptr available
1252 /// in more places that cached info does not necessarily keep.
1253 void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) {
1254 // If Ptr isn't really a pointer, just ignore it.
1255 if (!Ptr->getType()->isPointerTy()) return;
1256 // Flush store info for the pointer.
1257 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false));
1258 // Flush load info for the pointer.
1259 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true));
1262 /// invalidateCachedPredecessors - Clear the PredIteratorCache info.
1263 /// This needs to be done when the CFG changes, e.g., due to splitting
1265 void MemoryDependenceAnalysis::invalidateCachedPredecessors() {
1269 /// removeInstruction - Remove an instruction from the dependence analysis,
1270 /// updating the dependence of instructions that previously depended on it.
1271 /// This method attempts to keep the cache coherent using the reverse map.
1272 void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) {
1273 // Walk through the Non-local dependencies, removing this one as the value
1274 // for any cached queries.
1275 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst);
1276 if (NLDI != NonLocalDeps.end()) {
1277 NonLocalDepInfo &BlockMap = NLDI->second.first;
1278 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end();
1280 if (Instruction *Inst = DI->getResult().getInst())
1281 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst);
1282 NonLocalDeps.erase(NLDI);
1285 // If we have a cached local dependence query for this instruction, remove it.
1287 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst);
1288 if (LocalDepEntry != LocalDeps.end()) {
1289 // Remove us from DepInst's reverse set now that the local dep info is gone.
1290 if (Instruction *Inst = LocalDepEntry->second.getInst())
1291 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst);
1293 // Remove this local dependency info.
1294 LocalDeps.erase(LocalDepEntry);
1297 // If we have any cached pointer dependencies on this instruction, remove
1298 // them. If the instruction has non-pointer type, then it can't be a pointer
1301 // Remove it from both the load info and the store info. The instruction
1302 // can't be in either of these maps if it is non-pointer.
1303 if (RemInst->getType()->isPointerTy()) {
1304 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false));
1305 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true));
1308 // Loop over all of the things that depend on the instruction we're removing.
1310 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd;
1312 // If we find RemInst as a clobber or Def in any of the maps for other values,
1313 // we need to replace its entry with a dirty version of the instruction after
1314 // it. If RemInst is a terminator, we use a null dirty value.
1316 // Using a dirty version of the instruction after RemInst saves having to scan
1317 // the entire block to get to this point.
1318 MemDepResult NewDirtyVal;
1319 if (!RemInst->isTerminator())
1320 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst));
1322 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst);
1323 if (ReverseDepIt != ReverseLocalDeps.end()) {
1324 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second;
1325 // RemInst can't be the terminator if it has local stuff depending on it.
1326 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) &&
1327 "Nothing can locally depend on a terminator");
1329 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(),
1330 E = ReverseDeps.end(); I != E; ++I) {
1331 Instruction *InstDependingOnRemInst = *I;
1332 assert(InstDependingOnRemInst != RemInst &&
1333 "Already removed our local dep info");
1335 LocalDeps[InstDependingOnRemInst] = NewDirtyVal;
1337 // Make sure to remember that new things depend on NewDepInst.
1338 assert(NewDirtyVal.getInst() && "There is no way something else can have "
1339 "a local dep on this if it is a terminator!");
1340 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(),
1341 InstDependingOnRemInst));
1344 ReverseLocalDeps.erase(ReverseDepIt);
1346 // Add new reverse deps after scanning the set, to avoid invalidating the
1347 // 'ReverseDeps' reference.
1348 while (!ReverseDepsToAdd.empty()) {
1349 ReverseLocalDeps[ReverseDepsToAdd.back().first]
1350 .insert(ReverseDepsToAdd.back().second);
1351 ReverseDepsToAdd.pop_back();
1355 ReverseDepIt = ReverseNonLocalDeps.find(RemInst);
1356 if (ReverseDepIt != ReverseNonLocalDeps.end()) {
1357 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second;
1358 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end();
1360 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst");
1362 PerInstNLInfo &INLD = NonLocalDeps[*I];
1363 // The information is now dirty!
1366 for (NonLocalDepInfo::iterator DI = INLD.first.begin(),
1367 DE = INLD.first.end(); DI != DE; ++DI) {
1368 if (DI->getResult().getInst() != RemInst) continue;
1370 // Convert to a dirty entry for the subsequent instruction.
1371 DI->setResult(NewDirtyVal);
1373 if (Instruction *NextI = NewDirtyVal.getInst())
1374 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I));
1378 ReverseNonLocalDeps.erase(ReverseDepIt);
1380 // Add new reverse deps after scanning the set, to avoid invalidating 'Set'
1381 while (!ReverseDepsToAdd.empty()) {
1382 ReverseNonLocalDeps[ReverseDepsToAdd.back().first]
1383 .insert(ReverseDepsToAdd.back().second);
1384 ReverseDepsToAdd.pop_back();
1388 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a
1389 // value in the NonLocalPointerDeps info.
1390 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt =
1391 ReverseNonLocalPtrDeps.find(RemInst);
1392 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) {
1393 SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second;
1394 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd;
1396 for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(),
1397 E = Set.end(); I != E; ++I) {
1398 ValueIsLoadPair P = *I;
1399 assert(P.getPointer() != RemInst &&
1400 "Already removed NonLocalPointerDeps info for RemInst");
1402 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps;
1404 // The cache is not valid for any specific block anymore.
1405 NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair();
1407 // Update any entries for RemInst to use the instruction after it.
1408 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
1410 if (DI->getResult().getInst() != RemInst) continue;
1412 // Convert to a dirty entry for the subsequent instruction.
1413 DI->setResult(NewDirtyVal);
1415 if (Instruction *NewDirtyInst = NewDirtyVal.getInst())
1416 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P));
1419 // Re-sort the NonLocalDepInfo. Changing the dirty entry to its
1420 // subsequent value may invalidate the sortedness.
1421 std::sort(NLPDI.begin(), NLPDI.end());
1424 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt);
1426 while (!ReversePtrDepsToAdd.empty()) {
1427 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first]
1428 .insert(ReversePtrDepsToAdd.back().second);
1429 ReversePtrDepsToAdd.pop_back();
1434 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?");
1435 AA->deleteValue(RemInst);
1436 DEBUG(verifyRemoved(RemInst));
1438 /// verifyRemoved - Verify that the specified instruction does not occur
1439 /// in our internal data structures.
1440 void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const {
1441 for (LocalDepMapType::const_iterator I = LocalDeps.begin(),
1442 E = LocalDeps.end(); I != E; ++I) {
1443 assert(I->first != D && "Inst occurs in data structures");
1444 assert(I->second.getInst() != D &&
1445 "Inst occurs in data structures");
1448 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(),
1449 E = NonLocalPointerDeps.end(); I != E; ++I) {
1450 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key");
1451 const NonLocalDepInfo &Val = I->second.NonLocalDeps;
1452 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end();
1454 assert(II->getResult().getInst() != D && "Inst occurs as NLPD value");
1457 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(),
1458 E = NonLocalDeps.end(); I != E; ++I) {
1459 assert(I->first != D && "Inst occurs in data structures");
1460 const PerInstNLInfo &INLD = I->second;
1461 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(),
1462 EE = INLD.first.end(); II != EE; ++II)
1463 assert(II->getResult().getInst() != D && "Inst occurs in data structures");
1466 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(),
1467 E = ReverseLocalDeps.end(); I != E; ++I) {
1468 assert(I->first != D && "Inst occurs in data structures");
1469 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1470 EE = I->second.end(); II != EE; ++II)
1471 assert(*II != D && "Inst occurs in data structures");
1474 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(),
1475 E = ReverseNonLocalDeps.end();
1477 assert(I->first != D && "Inst occurs in data structures");
1478 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1479 EE = I->second.end(); II != EE; ++II)
1480 assert(*II != D && "Inst occurs in data structures");
1483 for (ReverseNonLocalPtrDepTy::const_iterator
1484 I = ReverseNonLocalPtrDeps.begin(),
1485 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) {
1486 assert(I->first != D && "Inst occurs in rev NLPD map");
1488 for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(),
1489 E = I->second.end(); II != E; ++II)
1490 assert(*II != ValueIsLoadPair(D, false) &&
1491 *II != ValueIsLoadPair(D, true) &&
1492 "Inst occurs in ReverseNonLocalPtrDeps map");