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, AA->getTargetLibraryInfo())) {
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);
236 // If we could not obtain a pointer for the instruction and the instruction
237 // touches memory then assume that this is a dependency.
238 if (MR != AliasAnalysis::NoModRef)
239 return MemDepResult::getClobber(Inst);
242 // No dependence found. If this is the entry block of the function, it is
243 // unknown, otherwise it is non-local.
244 if (BB != &BB->getParent()->getEntryBlock())
245 return MemDepResult::getNonLocal();
246 return MemDepResult::getNonFuncLocal();
249 /// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
250 /// would fully overlap MemLoc if done as a wider legal integer load.
252 /// MemLocBase, MemLocOffset are lazily computed here the first time the
253 /// base/offs of memloc is needed.
255 isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc,
256 const Value *&MemLocBase,
259 const TargetData *TD) {
260 // If we have no target data, we can't do this.
261 if (TD == 0) return false;
263 // If we haven't already computed the base/offset of MemLoc, do so now.
265 MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, *TD);
267 unsigned Size = MemoryDependenceAnalysis::
268 getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size,
273 /// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that
274 /// looks at a memory location for a load (specified by MemLocBase, Offs,
275 /// and Size) and compares it against a load. If the specified load could
276 /// be safely widened to a larger integer load that is 1) still efficient,
277 /// 2) safe for the target, and 3) would provide the specified memory
278 /// location value, then this function returns the size in bytes of the
279 /// load width to use. If not, this returns zero.
280 unsigned MemoryDependenceAnalysis::
281 getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
282 unsigned MemLocSize, const LoadInst *LI,
283 const TargetData &TD) {
284 // We can only extend simple integer loads.
285 if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0;
287 // Get the base of this load.
289 const Value *LIBase =
290 GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, TD);
292 // If the two pointers are not based on the same pointer, we can't tell that
294 if (LIBase != MemLocBase) return 0;
296 // Okay, the two values are based on the same pointer, but returned as
297 // no-alias. This happens when we have things like two byte loads at "P+1"
298 // and "P+3". Check to see if increasing the size of the "LI" load up to its
299 // alignment (or the largest native integer type) will allow us to load all
300 // the bits required by MemLoc.
302 // If MemLoc is before LI, then no widening of LI will help us out.
303 if (MemLocOffs < LIOffs) return 0;
305 // Get the alignment of the load in bytes. We assume that it is safe to load
306 // any legal integer up to this size without a problem. For example, if we're
307 // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can
308 // widen it up to an i32 load. If it is known 2-byte aligned, we can widen it
310 unsigned LoadAlign = LI->getAlignment();
312 int64_t MemLocEnd = MemLocOffs+MemLocSize;
314 // If no amount of rounding up will let MemLoc fit into LI, then bail out.
315 if (LIOffs+LoadAlign < MemLocEnd) return 0;
317 // This is the size of the load to try. Start with the next larger power of
319 unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U;
320 NewLoadByteSize = NextPowerOf2(NewLoadByteSize);
323 // If this load size is bigger than our known alignment or would not fit
324 // into a native integer register, then we fail.
325 if (NewLoadByteSize > LoadAlign ||
326 !TD.fitsInLegalInteger(NewLoadByteSize*8))
329 if (LIOffs+NewLoadByteSize > MemLocEnd &&
330 LI->getParent()->getParent()->hasFnAttr(Attribute::AddressSafety)) {
331 // We will be reading past the location accessed by the original program.
332 // While this is safe in a regular build, Address Safety analysis tools
333 // may start reporting false warnings. So, don't do widening.
337 // If a load of this width would include all of MemLoc, then we succeed.
338 if (LIOffs+NewLoadByteSize >= MemLocEnd)
339 return NewLoadByteSize;
341 NewLoadByteSize <<= 1;
345 /// getPointerDependencyFrom - Return the instruction on which a memory
346 /// location depends. If isLoad is true, this routine ignores may-aliases with
347 /// read-only operations. If isLoad is false, this routine ignores may-aliases
348 /// with reads from read-only locations.
349 MemDepResult MemoryDependenceAnalysis::
350 getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
351 BasicBlock::iterator ScanIt, BasicBlock *BB) {
353 const Value *MemLocBase = 0;
354 int64_t MemLocOffset = 0;
356 unsigned Limit = BlockScanLimit;
358 // Walk backwards through the basic block, looking for dependencies.
359 while (ScanIt != BB->begin()) {
360 // Limit the amount of scanning we do so we don't end up with quadratic
361 // running time on extreme testcases.
364 return MemDepResult::getUnknown();
366 Instruction *Inst = --ScanIt;
368 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
369 // Debug intrinsics don't (and can't) cause dependences.
370 if (isa<DbgInfoIntrinsic>(II)) continue;
372 // If we reach a lifetime begin or end marker, then the query ends here
373 // because the value is undefined.
374 if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
375 // FIXME: This only considers queries directly on the invariant-tagged
376 // pointer, not on query pointers that are indexed off of them. It'd
377 // be nice to handle that at some point (the right approach is to use
378 // GetPointerBaseWithConstantOffset).
379 if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)),
381 return MemDepResult::getDef(II);
386 // Values depend on loads if the pointers are must aliased. This means that
387 // a load depends on another must aliased load from the same value.
388 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
389 // Atomic loads have complications involved.
390 // FIXME: This is overly conservative.
391 if (!LI->isUnordered())
392 return MemDepResult::getClobber(LI);
394 AliasAnalysis::Location LoadLoc = AA->getLocation(LI);
396 // If we found a pointer, check if it could be the same as our pointer.
397 AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc);
400 if (R == AliasAnalysis::NoAlias) {
401 // If this is an over-aligned integer load (for example,
402 // "load i8* %P, align 4") see if it would obviously overlap with the
403 // queried location if widened to a larger load (e.g. if the queried
404 // location is 1 byte at P+1). If so, return it as a load/load
405 // clobber result, allowing the client to decide to widen the load if
407 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
408 if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() &&
409 isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase,
410 MemLocOffset, LI, TD))
411 return MemDepResult::getClobber(Inst);
416 // Must aliased loads are defs of each other.
417 if (R == AliasAnalysis::MustAlias)
418 return MemDepResult::getDef(Inst);
420 #if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads
421 // in terms of clobbering loads, but since it does this by looking
422 // at the clobbering load directly, it doesn't know about any
423 // phi translation that may have happened along the way.
425 // If we have a partial alias, then return this as a clobber for the
427 if (R == AliasAnalysis::PartialAlias)
428 return MemDepResult::getClobber(Inst);
431 // Random may-alias loads don't depend on each other without a
436 // Stores don't depend on other no-aliased accesses.
437 if (R == AliasAnalysis::NoAlias)
440 // Stores don't alias loads from read-only memory.
441 if (AA->pointsToConstantMemory(LoadLoc))
444 // Stores depend on may/must aliased loads.
445 return MemDepResult::getDef(Inst);
448 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
449 // Atomic stores have complications involved.
450 // FIXME: This is overly conservative.
451 if (!SI->isUnordered())
452 return MemDepResult::getClobber(SI);
454 // If alias analysis can tell that this store is guaranteed to not modify
455 // the query pointer, ignore it. Use getModRefInfo to handle cases where
456 // the query pointer points to constant memory etc.
457 if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef)
460 // Ok, this store might clobber the query pointer. Check to see if it is
461 // a must alias: in this case, we want to return this as a def.
462 AliasAnalysis::Location StoreLoc = AA->getLocation(SI);
464 // If we found a pointer, check if it could be the same as our pointer.
465 AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc);
467 if (R == AliasAnalysis::NoAlias)
469 if (R == AliasAnalysis::MustAlias)
470 return MemDepResult::getDef(Inst);
471 return MemDepResult::getClobber(Inst);
474 // If this is an allocation, and if we know that the accessed pointer is to
475 // the allocation, return Def. This means that there is no dependence and
476 // the access can be optimized based on that. For example, a load could
478 // Note: Only determine this to be a malloc if Inst is the malloc call, not
479 // a subsequent bitcast of the malloc call result. There can be stores to
480 // the malloced memory between the malloc call and its bitcast uses, and we
481 // need to continue scanning until the malloc call.
482 if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, AA->getTargetLibraryInfo())){
483 const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, TD);
485 if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
486 return MemDepResult::getDef(Inst);
490 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
491 AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc);
492 // If necessary, perform additional analysis.
493 if (MR == AliasAnalysis::ModRef)
494 MR = AA->callCapturesBefore(Inst, MemLoc, DT);
496 case AliasAnalysis::NoModRef:
497 // If the call has no effect on the queried pointer, just ignore it.
499 case AliasAnalysis::Mod:
500 return MemDepResult::getClobber(Inst);
501 case AliasAnalysis::Ref:
502 // If the call is known to never store to the pointer, and if this is a
503 // load query, we can safely ignore it (scan past it).
507 // Otherwise, there is a potential dependence. Return a clobber.
508 return MemDepResult::getClobber(Inst);
512 // No dependence found. If this is the entry block of the function, it is
513 // unknown, otherwise it is non-local.
514 if (BB != &BB->getParent()->getEntryBlock())
515 return MemDepResult::getNonLocal();
516 return MemDepResult::getNonFuncLocal();
519 /// getDependency - Return the instruction on which a memory operation
521 MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
522 Instruction *ScanPos = QueryInst;
524 // Check for a cached result
525 MemDepResult &LocalCache = LocalDeps[QueryInst];
527 // If the cached entry is non-dirty, just return it. Note that this depends
528 // on MemDepResult's default constructing to 'dirty'.
529 if (!LocalCache.isDirty())
532 // Otherwise, if we have a dirty entry, we know we can start the scan at that
533 // instruction, which may save us some work.
534 if (Instruction *Inst = LocalCache.getInst()) {
537 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst);
540 BasicBlock *QueryParent = QueryInst->getParent();
543 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
544 // No dependence found. If this is the entry block of the function, it is
545 // unknown, otherwise it is non-local.
546 if (QueryParent != &QueryParent->getParent()->getEntryBlock())
547 LocalCache = MemDepResult::getNonLocal();
549 LocalCache = MemDepResult::getNonFuncLocal();
551 AliasAnalysis::Location MemLoc;
552 AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
554 // If we can do a pointer scan, make it happen.
555 bool isLoad = !(MR & AliasAnalysis::Mod);
556 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst))
557 isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start;
559 LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos,
561 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
562 CallSite QueryCS(QueryInst);
563 bool isReadOnly = AA->onlyReadsMemory(QueryCS);
564 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos,
567 // Non-memory instruction.
568 LocalCache = MemDepResult::getUnknown();
571 // Remember the result!
572 if (Instruction *I = LocalCache.getInst())
573 ReverseLocalDeps[I].insert(QueryInst);
579 /// AssertSorted - This method is used when -debug is specified to verify that
580 /// cache arrays are properly kept sorted.
581 static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
583 if (Count == -1) Count = Cache.size();
584 if (Count == 0) return;
586 for (unsigned i = 1; i != unsigned(Count); ++i)
587 assert(!(Cache[i] < Cache[i-1]) && "Cache isn't sorted!");
591 /// getNonLocalCallDependency - Perform a full dependency query for the
592 /// specified call, returning the set of blocks that the value is
593 /// potentially live across. The returned set of results will include a
594 /// "NonLocal" result for all blocks where the value is live across.
596 /// This method assumes the instruction returns a "NonLocal" dependency
597 /// within its own block.
599 /// This returns a reference to an internal data structure that may be
600 /// invalidated on the next non-local query or when an instruction is
601 /// removed. Clients must copy this data if they want it around longer than
603 const MemoryDependenceAnalysis::NonLocalDepInfo &
604 MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
605 assert(getDependency(QueryCS.getInstruction()).isNonLocal() &&
606 "getNonLocalCallDependency should only be used on calls with non-local deps!");
607 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()];
608 NonLocalDepInfo &Cache = CacheP.first;
610 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In
611 /// the cached case, this can happen due to instructions being deleted etc. In
612 /// the uncached case, this starts out as the set of predecessors we care
614 SmallVector<BasicBlock*, 32> DirtyBlocks;
616 if (!Cache.empty()) {
617 // Okay, we have a cache entry. If we know it is not dirty, just return it
618 // with no computation.
619 if (!CacheP.second) {
624 // If we already have a partially computed set of results, scan them to
625 // determine what is dirty, seeding our initial DirtyBlocks worklist.
626 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end();
628 if (I->getResult().isDirty())
629 DirtyBlocks.push_back(I->getBB());
631 // Sort the cache so that we can do fast binary search lookups below.
632 std::sort(Cache.begin(), Cache.end());
634 ++NumCacheDirtyNonLocal;
635 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: "
636 // << Cache.size() << " cached: " << *QueryInst;
638 // Seed DirtyBlocks with each of the preds of QueryInst's block.
639 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent();
640 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI)
641 DirtyBlocks.push_back(*PI);
642 ++NumUncacheNonLocal;
645 // isReadonlyCall - If this is a read-only call, we can be more aggressive.
646 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS);
648 SmallPtrSet<BasicBlock*, 64> Visited;
650 unsigned NumSortedEntries = Cache.size();
651 DEBUG(AssertSorted(Cache));
653 // Iterate while we still have blocks to update.
654 while (!DirtyBlocks.empty()) {
655 BasicBlock *DirtyBB = DirtyBlocks.back();
656 DirtyBlocks.pop_back();
658 // Already processed this block?
659 if (!Visited.insert(DirtyBB))
662 // Do a binary search to see if we already have an entry for this block in
663 // the cache set. If so, find it.
664 DEBUG(AssertSorted(Cache, NumSortedEntries));
665 NonLocalDepInfo::iterator Entry =
666 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries,
667 NonLocalDepEntry(DirtyBB));
668 if (Entry != Cache.begin() && prior(Entry)->getBB() == DirtyBB)
671 NonLocalDepEntry *ExistingResult = 0;
672 if (Entry != Cache.begin()+NumSortedEntries &&
673 Entry->getBB() == DirtyBB) {
674 // If we already have an entry, and if it isn't already dirty, the block
676 if (!Entry->getResult().isDirty())
679 // Otherwise, remember this slot so we can update the value.
680 ExistingResult = &*Entry;
683 // If the dirty entry has a pointer, start scanning from it so we don't have
684 // to rescan the entire block.
685 BasicBlock::iterator ScanPos = DirtyBB->end();
686 if (ExistingResult) {
687 if (Instruction *Inst = ExistingResult->getResult().getInst()) {
689 // We're removing QueryInst's use of Inst.
690 RemoveFromReverseMap(ReverseNonLocalDeps, Inst,
691 QueryCS.getInstruction());
695 // Find out if this block has a local dependency for QueryInst.
698 if (ScanPos != DirtyBB->begin()) {
699 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
700 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
701 // No dependence found. If this is the entry block of the function, it is
702 // a clobber, otherwise it is unknown.
703 Dep = MemDepResult::getNonLocal();
705 Dep = MemDepResult::getNonFuncLocal();
708 // If we had a dirty entry for the block, update it. Otherwise, just add
711 ExistingResult->setResult(Dep);
713 Cache.push_back(NonLocalDepEntry(DirtyBB, Dep));
715 // If the block has a dependency (i.e. it isn't completely transparent to
716 // the value), remember the association!
717 if (!Dep.isNonLocal()) {
718 // Keep the ReverseNonLocalDeps map up to date so we can efficiently
719 // update this when we remove instructions.
720 if (Instruction *Inst = Dep.getInst())
721 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction());
724 // If the block *is* completely transparent to the load, we need to check
725 // the predecessors of this block. Add them to our worklist.
726 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI)
727 DirtyBlocks.push_back(*PI);
734 /// getNonLocalPointerDependency - Perform a full dependency query for an
735 /// access to the specified (non-volatile) memory location, returning the
736 /// set of instructions that either define or clobber the value.
738 /// This method assumes the pointer has a "NonLocal" dependency within its
741 void MemoryDependenceAnalysis::
742 getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad,
744 SmallVectorImpl<NonLocalDepResult> &Result) {
745 assert(Loc.Ptr->getType()->isPointerTy() &&
746 "Can't get pointer deps of a non-pointer!");
749 PHITransAddr Address(const_cast<Value *>(Loc.Ptr), TD);
751 // This is the set of blocks we've inspected, and the pointer we consider in
752 // each block. Because of critical edges, we currently bail out if querying
753 // a block with multiple different pointers. This can happen during PHI
755 DenseMap<BasicBlock*, Value*> Visited;
756 if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB,
757 Result, Visited, true))
760 Result.push_back(NonLocalDepResult(FromBB,
761 MemDepResult::getUnknown(),
762 const_cast<Value *>(Loc.Ptr)));
765 /// GetNonLocalInfoForBlock - Compute the memdep value for BB with
766 /// Pointer/PointeeSize using either cached information in Cache or by doing a
767 /// lookup (which may use dirty cache info if available). If we do a lookup,
768 /// add the result to the cache.
769 MemDepResult MemoryDependenceAnalysis::
770 GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
771 bool isLoad, BasicBlock *BB,
772 NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
774 // Do a binary search to see if we already have an entry for this block in
775 // the cache set. If so, find it.
776 NonLocalDepInfo::iterator Entry =
777 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries,
778 NonLocalDepEntry(BB));
779 if (Entry != Cache->begin() && (Entry-1)->getBB() == BB)
782 NonLocalDepEntry *ExistingResult = 0;
783 if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB)
784 ExistingResult = &*Entry;
786 // If we have a cached entry, and it is non-dirty, use it as the value for
788 if (ExistingResult && !ExistingResult->getResult().isDirty()) {
789 ++NumCacheNonLocalPtr;
790 return ExistingResult->getResult();
793 // Otherwise, we have to scan for the value. If we have a dirty cache
794 // entry, start scanning from its position, otherwise we scan from the end
796 BasicBlock::iterator ScanPos = BB->end();
797 if (ExistingResult && ExistingResult->getResult().getInst()) {
798 assert(ExistingResult->getResult().getInst()->getParent() == BB &&
799 "Instruction invalidated?");
800 ++NumCacheDirtyNonLocalPtr;
801 ScanPos = ExistingResult->getResult().getInst();
803 // Eliminating the dirty entry from 'Cache', so update the reverse info.
804 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
805 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey);
807 ++NumUncacheNonLocalPtr;
810 // Scan the block for the dependency.
811 MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB);
813 // If we had a dirty entry for the block, update it. Otherwise, just add
816 ExistingResult->setResult(Dep);
818 Cache->push_back(NonLocalDepEntry(BB, Dep));
820 // If the block has a dependency (i.e. it isn't completely transparent to
821 // the value), remember the reverse association because we just added it
823 if (!Dep.isDef() && !Dep.isClobber())
826 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
827 // update MemDep when we remove instructions.
828 Instruction *Inst = Dep.getInst();
829 assert(Inst && "Didn't depend on anything?");
830 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
831 ReverseNonLocalPtrDeps[Inst].insert(CacheKey);
835 /// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain
836 /// number of elements in the array that are already properly ordered. This is
837 /// optimized for the case when only a few entries are added.
839 SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
840 unsigned NumSortedEntries) {
841 switch (Cache.size() - NumSortedEntries) {
843 // done, no new entries.
846 // Two new entries, insert the last one into place.
847 NonLocalDepEntry Val = Cache.back();
849 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
850 std::upper_bound(Cache.begin(), Cache.end()-1, Val);
851 Cache.insert(Entry, Val);
855 // One new entry, Just insert the new value at the appropriate position.
856 if (Cache.size() != 1) {
857 NonLocalDepEntry Val = Cache.back();
859 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
860 std::upper_bound(Cache.begin(), Cache.end(), Val);
861 Cache.insert(Entry, Val);
865 // Added many values, do a full scale sort.
866 std::sort(Cache.begin(), Cache.end());
871 /// getNonLocalPointerDepFromBB - Perform a dependency query based on
872 /// pointer/pointeesize starting at the end of StartBB. Add any clobber/def
873 /// results to the results vector and keep track of which blocks are visited in
876 /// This has special behavior for the first block queries (when SkipFirstBlock
877 /// is true). In this special case, it ignores the contents of the specified
878 /// block and starts returning dependence info for its predecessors.
880 /// This function returns false on success, or true to indicate that it could
881 /// not compute dependence information for some reason. This should be treated
882 /// as a clobber dependence on the first instruction in the predecessor block.
883 bool MemoryDependenceAnalysis::
884 getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
885 const AliasAnalysis::Location &Loc,
886 bool isLoad, BasicBlock *StartBB,
887 SmallVectorImpl<NonLocalDepResult> &Result,
888 DenseMap<BasicBlock*, Value*> &Visited,
889 bool SkipFirstBlock) {
891 // Look up the cached info for Pointer.
892 ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad);
894 // Set up a temporary NLPI value. If the map doesn't yet have an entry for
895 // CacheKey, this value will be inserted as the associated value. Otherwise,
896 // it'll be ignored, and we'll have to check to see if the cached size and
897 // tbaa tag are consistent with the current query.
898 NonLocalPointerInfo InitialNLPI;
899 InitialNLPI.Size = Loc.Size;
900 InitialNLPI.TBAATag = Loc.TBAATag;
902 // Get the NLPI for CacheKey, inserting one into the map if it doesn't
904 std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair =
905 NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI));
906 NonLocalPointerInfo *CacheInfo = &Pair.first->second;
908 // If we already have a cache entry for this CacheKey, we may need to do some
909 // work to reconcile the cache entry and the current query.
911 if (CacheInfo->Size < Loc.Size) {
912 // The query's Size is greater than the cached one. Throw out the
913 // cached data and proceed with the query at the greater size.
914 CacheInfo->Pair = BBSkipFirstBlockPair();
915 CacheInfo->Size = Loc.Size;
916 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
917 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
918 if (Instruction *Inst = DI->getResult().getInst())
919 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
920 CacheInfo->NonLocalDeps.clear();
921 } else if (CacheInfo->Size > Loc.Size) {
922 // This query's Size is less than the cached one. Conservatively restart
923 // the query using the greater size.
924 return getNonLocalPointerDepFromBB(Pointer,
925 Loc.getWithNewSize(CacheInfo->Size),
926 isLoad, StartBB, Result, Visited,
930 // If the query's TBAATag is inconsistent with the cached one,
931 // conservatively throw out the cached data and restart the query with
933 if (CacheInfo->TBAATag != Loc.TBAATag) {
934 if (CacheInfo->TBAATag) {
935 CacheInfo->Pair = BBSkipFirstBlockPair();
936 CacheInfo->TBAATag = 0;
937 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
938 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
939 if (Instruction *Inst = DI->getResult().getInst())
940 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
941 CacheInfo->NonLocalDeps.clear();
944 return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(),
945 isLoad, StartBB, Result, Visited,
950 NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps;
952 // If we have valid cached information for exactly the block we are
953 // investigating, just return it with no recomputation.
954 if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
955 // We have a fully cached result for this query then we can just return the
956 // cached results and populate the visited set. However, we have to verify
957 // that we don't already have conflicting results for these blocks. Check
958 // to ensure that if a block in the results set is in the visited set that
959 // it was for the same pointer query.
960 if (!Visited.empty()) {
961 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
963 DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->getBB());
964 if (VI == Visited.end() || VI->second == Pointer.getAddr())
967 // We have a pointer mismatch in a block. Just return clobber, saying
968 // that something was clobbered in this result. We could also do a
969 // non-fully cached query, but there is little point in doing this.
974 Value *Addr = Pointer.getAddr();
975 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
977 Visited.insert(std::make_pair(I->getBB(), Addr));
978 if (!I->getResult().isNonLocal())
979 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr));
981 ++NumCacheCompleteNonLocalPtr;
985 // Otherwise, either this is a new block, a block with an invalid cache
986 // pointer or one that we're about to invalidate by putting more info into it
987 // than its valid cache info. If empty, the result will be valid cache info,
988 // otherwise it isn't.
990 CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
992 CacheInfo->Pair = BBSkipFirstBlockPair();
994 SmallVector<BasicBlock*, 32> Worklist;
995 Worklist.push_back(StartBB);
997 // PredList used inside loop.
998 SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList;
1000 // Keep track of the entries that we know are sorted. Previously cached
1001 // entries will all be sorted. The entries we add we only sort on demand (we
1002 // don't insert every element into its sorted position). We know that we
1003 // won't get any reuse from currently inserted values, because we don't
1004 // revisit blocks after we insert info for them.
1005 unsigned NumSortedEntries = Cache->size();
1006 DEBUG(AssertSorted(*Cache));
1008 while (!Worklist.empty()) {
1009 BasicBlock *BB = Worklist.pop_back_val();
1011 // Skip the first block if we have it.
1012 if (!SkipFirstBlock) {
1013 // Analyze the dependency of *Pointer in FromBB. See if we already have
1015 assert(Visited.count(BB) && "Should check 'visited' before adding to WL");
1017 // Get the dependency info for Pointer in BB. If we have cached
1018 // information, we will use it, otherwise we compute it.
1019 DEBUG(AssertSorted(*Cache, NumSortedEntries));
1020 MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache,
1023 // If we got a Def or Clobber, add this to the list of results.
1024 if (!Dep.isNonLocal()) {
1025 Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr()));
1030 // If 'Pointer' is an instruction defined in this block, then we need to do
1031 // phi translation to change it into a value live in the predecessor block.
1032 // If not, we just add the predecessors to the worklist and scan them with
1033 // the same Pointer.
1034 if (!Pointer.NeedsPHITranslationFromBlock(BB)) {
1035 SkipFirstBlock = false;
1036 SmallVector<BasicBlock*, 16> NewBlocks;
1037 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1038 // Verify that we haven't looked at this block yet.
1039 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1040 InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr()));
1041 if (InsertRes.second) {
1042 // First time we've looked at *PI.
1043 NewBlocks.push_back(*PI);
1047 // If we have seen this block before, but it was with a different
1048 // pointer then we have a phi translation failure and we have to treat
1049 // this as a clobber.
1050 if (InsertRes.first->second != Pointer.getAddr()) {
1051 // Make sure to clean up the Visited map before continuing on to
1052 // PredTranslationFailure.
1053 for (unsigned i = 0; i < NewBlocks.size(); i++)
1054 Visited.erase(NewBlocks[i]);
1055 goto PredTranslationFailure;
1058 Worklist.append(NewBlocks.begin(), NewBlocks.end());
1062 // We do need to do phi translation, if we know ahead of time we can't phi
1063 // translate this value, don't even try.
1064 if (!Pointer.IsPotentiallyPHITranslatable())
1065 goto PredTranslationFailure;
1067 // We may have added values to the cache list before this PHI translation.
1068 // If so, we haven't done anything to ensure that the cache remains sorted.
1069 // Sort it now (if needed) so that recursive invocations of
1070 // getNonLocalPointerDepFromBB and other routines that could reuse the cache
1071 // value will only see properly sorted cache arrays.
1072 if (Cache && NumSortedEntries != Cache->size()) {
1073 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1074 NumSortedEntries = Cache->size();
1079 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1080 BasicBlock *Pred = *PI;
1081 PredList.push_back(std::make_pair(Pred, Pointer));
1083 // Get the PHI translated pointer in this predecessor. This can fail if
1084 // not translatable, in which case the getAddr() returns null.
1085 PHITransAddr &PredPointer = PredList.back().second;
1086 PredPointer.PHITranslateValue(BB, Pred, 0);
1088 Value *PredPtrVal = PredPointer.getAddr();
1090 // Check to see if we have already visited this pred block with another
1091 // pointer. If so, we can't do this lookup. This failure can occur
1092 // with PHI translation when a critical edge exists and the PHI node in
1093 // the successor translates to a pointer value different than the
1094 // pointer the block was first analyzed with.
1095 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1096 InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal));
1098 if (!InsertRes.second) {
1099 // We found the pred; take it off the list of preds to visit.
1100 PredList.pop_back();
1102 // If the predecessor was visited with PredPtr, then we already did
1103 // the analysis and can ignore it.
1104 if (InsertRes.first->second == PredPtrVal)
1107 // Otherwise, the block was previously analyzed with a different
1108 // pointer. We can't represent the result of this case, so we just
1109 // treat this as a phi translation failure.
1111 // Make sure to clean up the Visited map before continuing on to
1112 // PredTranslationFailure.
1113 for (unsigned i = 0; i < PredList.size(); i++)
1114 Visited.erase(PredList[i].first);
1116 goto PredTranslationFailure;
1120 // Actually process results here; this need to be a separate loop to avoid
1121 // calling getNonLocalPointerDepFromBB for blocks we don't want to return
1122 // any results for. (getNonLocalPointerDepFromBB will modify our
1123 // datastructures in ways the code after the PredTranslationFailure label
1125 for (unsigned i = 0; i < PredList.size(); i++) {
1126 BasicBlock *Pred = PredList[i].first;
1127 PHITransAddr &PredPointer = PredList[i].second;
1128 Value *PredPtrVal = PredPointer.getAddr();
1130 bool CanTranslate = true;
1131 // If PHI translation was unable to find an available pointer in this
1132 // predecessor, then we have to assume that the pointer is clobbered in
1133 // that predecessor. We can still do PRE of the load, which would insert
1134 // a computation of the pointer in this predecessor.
1135 if (PredPtrVal == 0)
1136 CanTranslate = false;
1138 // FIXME: it is entirely possible that PHI translating will end up with
1139 // the same value. Consider PHI translating something like:
1140 // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need*
1141 // to recurse here, pedantically speaking.
1143 // If getNonLocalPointerDepFromBB fails here, that means the cached
1144 // result conflicted with the Visited list; we have to conservatively
1145 // assume it is unknown, but this also does not block PRE of the load.
1146 if (!CanTranslate ||
1147 getNonLocalPointerDepFromBB(PredPointer,
1148 Loc.getWithNewPtr(PredPtrVal),
1151 // Add the entry to the Result list.
1152 NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal);
1153 Result.push_back(Entry);
1155 // Since we had a phi translation failure, the cache for CacheKey won't
1156 // include all of the entries that we need to immediately satisfy future
1157 // queries. Mark this in NonLocalPointerDeps by setting the
1158 // BBSkipFirstBlockPair pointer to null. This requires reuse of the
1159 // cached value to do more work but not miss the phi trans failure.
1160 NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey];
1161 NLPI.Pair = BBSkipFirstBlockPair();
1166 // Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
1167 CacheInfo = &NonLocalPointerDeps[CacheKey];
1168 Cache = &CacheInfo->NonLocalDeps;
1169 NumSortedEntries = Cache->size();
1171 // Since we did phi translation, the "Cache" set won't contain all of the
1172 // results for the query. This is ok (we can still use it to accelerate
1173 // specific block queries) but we can't do the fastpath "return all
1174 // results from the set" Clear out the indicator for this.
1175 CacheInfo->Pair = BBSkipFirstBlockPair();
1176 SkipFirstBlock = false;
1179 PredTranslationFailure:
1180 // The following code is "failure"; we can't produce a sane translation
1181 // for the given block. It assumes that we haven't modified any of
1182 // our datastructures while processing the current block.
1185 // Refresh the CacheInfo/Cache pointer if it got invalidated.
1186 CacheInfo = &NonLocalPointerDeps[CacheKey];
1187 Cache = &CacheInfo->NonLocalDeps;
1188 NumSortedEntries = Cache->size();
1191 // Since we failed phi translation, the "Cache" set won't contain all of the
1192 // results for the query. This is ok (we can still use it to accelerate
1193 // specific block queries) but we can't do the fastpath "return all
1194 // results from the set". Clear out the indicator for this.
1195 CacheInfo->Pair = BBSkipFirstBlockPair();
1197 // If *nothing* works, mark the pointer as unknown.
1199 // If this is the magic first block, return this as a clobber of the whole
1200 // incoming value. Since we can't phi translate to one of the predecessors,
1201 // we have to bail out.
1205 for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) {
1206 assert(I != Cache->rend() && "Didn't find current block??");
1207 if (I->getBB() != BB)
1210 assert(I->getResult().isNonLocal() &&
1211 "Should only be here with transparent block");
1212 I->setResult(MemDepResult::getUnknown());
1213 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(),
1214 Pointer.getAddr()));
1219 // Okay, we're done now. If we added new values to the cache, re-sort it.
1220 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1221 DEBUG(AssertSorted(*Cache));
1225 /// RemoveCachedNonLocalPointerDependencies - If P exists in
1226 /// CachedNonLocalPointerInfo, remove it.
1227 void MemoryDependenceAnalysis::
1228 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) {
1229 CachedNonLocalPointerInfo::iterator It =
1230 NonLocalPointerDeps.find(P);
1231 if (It == NonLocalPointerDeps.end()) return;
1233 // Remove all of the entries in the BB->val map. This involves removing
1234 // instructions from the reverse map.
1235 NonLocalDepInfo &PInfo = It->second.NonLocalDeps;
1237 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
1238 Instruction *Target = PInfo[i].getResult().getInst();
1239 if (Target == 0) continue; // Ignore non-local dep results.
1240 assert(Target->getParent() == PInfo[i].getBB());
1242 // Eliminating the dirty entry from 'Cache', so update the reverse info.
1243 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P);
1246 // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo).
1247 NonLocalPointerDeps.erase(It);
1251 /// invalidateCachedPointerInfo - This method is used to invalidate cached
1252 /// information about the specified pointer, because it may be too
1253 /// conservative in memdep. This is an optional call that can be used when
1254 /// the client detects an equivalence between the pointer and some other
1255 /// value and replaces the other value with ptr. This can make Ptr available
1256 /// in more places that cached info does not necessarily keep.
1257 void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) {
1258 // If Ptr isn't really a pointer, just ignore it.
1259 if (!Ptr->getType()->isPointerTy()) return;
1260 // Flush store info for the pointer.
1261 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false));
1262 // Flush load info for the pointer.
1263 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true));
1266 /// invalidateCachedPredecessors - Clear the PredIteratorCache info.
1267 /// This needs to be done when the CFG changes, e.g., due to splitting
1269 void MemoryDependenceAnalysis::invalidateCachedPredecessors() {
1273 /// removeInstruction - Remove an instruction from the dependence analysis,
1274 /// updating the dependence of instructions that previously depended on it.
1275 /// This method attempts to keep the cache coherent using the reverse map.
1276 void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) {
1277 // Walk through the Non-local dependencies, removing this one as the value
1278 // for any cached queries.
1279 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst);
1280 if (NLDI != NonLocalDeps.end()) {
1281 NonLocalDepInfo &BlockMap = NLDI->second.first;
1282 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end();
1284 if (Instruction *Inst = DI->getResult().getInst())
1285 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst);
1286 NonLocalDeps.erase(NLDI);
1289 // If we have a cached local dependence query for this instruction, remove it.
1291 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst);
1292 if (LocalDepEntry != LocalDeps.end()) {
1293 // Remove us from DepInst's reverse set now that the local dep info is gone.
1294 if (Instruction *Inst = LocalDepEntry->second.getInst())
1295 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst);
1297 // Remove this local dependency info.
1298 LocalDeps.erase(LocalDepEntry);
1301 // If we have any cached pointer dependencies on this instruction, remove
1302 // them. If the instruction has non-pointer type, then it can't be a pointer
1305 // Remove it from both the load info and the store info. The instruction
1306 // can't be in either of these maps if it is non-pointer.
1307 if (RemInst->getType()->isPointerTy()) {
1308 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false));
1309 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true));
1312 // Loop over all of the things that depend on the instruction we're removing.
1314 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd;
1316 // If we find RemInst as a clobber or Def in any of the maps for other values,
1317 // we need to replace its entry with a dirty version of the instruction after
1318 // it. If RemInst is a terminator, we use a null dirty value.
1320 // Using a dirty version of the instruction after RemInst saves having to scan
1321 // the entire block to get to this point.
1322 MemDepResult NewDirtyVal;
1323 if (!RemInst->isTerminator())
1324 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst));
1326 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst);
1327 if (ReverseDepIt != ReverseLocalDeps.end()) {
1328 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second;
1329 // RemInst can't be the terminator if it has local stuff depending on it.
1330 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) &&
1331 "Nothing can locally depend on a terminator");
1333 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(),
1334 E = ReverseDeps.end(); I != E; ++I) {
1335 Instruction *InstDependingOnRemInst = *I;
1336 assert(InstDependingOnRemInst != RemInst &&
1337 "Already removed our local dep info");
1339 LocalDeps[InstDependingOnRemInst] = NewDirtyVal;
1341 // Make sure to remember that new things depend on NewDepInst.
1342 assert(NewDirtyVal.getInst() && "There is no way something else can have "
1343 "a local dep on this if it is a terminator!");
1344 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(),
1345 InstDependingOnRemInst));
1348 ReverseLocalDeps.erase(ReverseDepIt);
1350 // Add new reverse deps after scanning the set, to avoid invalidating the
1351 // 'ReverseDeps' reference.
1352 while (!ReverseDepsToAdd.empty()) {
1353 ReverseLocalDeps[ReverseDepsToAdd.back().first]
1354 .insert(ReverseDepsToAdd.back().second);
1355 ReverseDepsToAdd.pop_back();
1359 ReverseDepIt = ReverseNonLocalDeps.find(RemInst);
1360 if (ReverseDepIt != ReverseNonLocalDeps.end()) {
1361 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second;
1362 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end();
1364 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst");
1366 PerInstNLInfo &INLD = NonLocalDeps[*I];
1367 // The information is now dirty!
1370 for (NonLocalDepInfo::iterator DI = INLD.first.begin(),
1371 DE = INLD.first.end(); DI != DE; ++DI) {
1372 if (DI->getResult().getInst() != RemInst) continue;
1374 // Convert to a dirty entry for the subsequent instruction.
1375 DI->setResult(NewDirtyVal);
1377 if (Instruction *NextI = NewDirtyVal.getInst())
1378 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I));
1382 ReverseNonLocalDeps.erase(ReverseDepIt);
1384 // Add new reverse deps after scanning the set, to avoid invalidating 'Set'
1385 while (!ReverseDepsToAdd.empty()) {
1386 ReverseNonLocalDeps[ReverseDepsToAdd.back().first]
1387 .insert(ReverseDepsToAdd.back().second);
1388 ReverseDepsToAdd.pop_back();
1392 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a
1393 // value in the NonLocalPointerDeps info.
1394 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt =
1395 ReverseNonLocalPtrDeps.find(RemInst);
1396 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) {
1397 SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second;
1398 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd;
1400 for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(),
1401 E = Set.end(); I != E; ++I) {
1402 ValueIsLoadPair P = *I;
1403 assert(P.getPointer() != RemInst &&
1404 "Already removed NonLocalPointerDeps info for RemInst");
1406 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps;
1408 // The cache is not valid for any specific block anymore.
1409 NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair();
1411 // Update any entries for RemInst to use the instruction after it.
1412 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
1414 if (DI->getResult().getInst() != RemInst) continue;
1416 // Convert to a dirty entry for the subsequent instruction.
1417 DI->setResult(NewDirtyVal);
1419 if (Instruction *NewDirtyInst = NewDirtyVal.getInst())
1420 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P));
1423 // Re-sort the NonLocalDepInfo. Changing the dirty entry to its
1424 // subsequent value may invalidate the sortedness.
1425 std::sort(NLPDI.begin(), NLPDI.end());
1428 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt);
1430 while (!ReversePtrDepsToAdd.empty()) {
1431 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first]
1432 .insert(ReversePtrDepsToAdd.back().second);
1433 ReversePtrDepsToAdd.pop_back();
1438 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?");
1439 AA->deleteValue(RemInst);
1440 DEBUG(verifyRemoved(RemInst));
1442 /// verifyRemoved - Verify that the specified instruction does not occur
1443 /// in our internal data structures.
1444 void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const {
1445 for (LocalDepMapType::const_iterator I = LocalDeps.begin(),
1446 E = LocalDeps.end(); I != E; ++I) {
1447 assert(I->first != D && "Inst occurs in data structures");
1448 assert(I->second.getInst() != D &&
1449 "Inst occurs in data structures");
1452 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(),
1453 E = NonLocalPointerDeps.end(); I != E; ++I) {
1454 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key");
1455 const NonLocalDepInfo &Val = I->second.NonLocalDeps;
1456 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end();
1458 assert(II->getResult().getInst() != D && "Inst occurs as NLPD value");
1461 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(),
1462 E = NonLocalDeps.end(); I != E; ++I) {
1463 assert(I->first != D && "Inst occurs in data structures");
1464 const PerInstNLInfo &INLD = I->second;
1465 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(),
1466 EE = INLD.first.end(); II != EE; ++II)
1467 assert(II->getResult().getInst() != D && "Inst occurs in data structures");
1470 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(),
1471 E = ReverseLocalDeps.end(); I != E; ++I) {
1472 assert(I->first != D && "Inst occurs in data structures");
1473 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1474 EE = I->second.end(); II != EE; ++II)
1475 assert(*II != D && "Inst occurs in data structures");
1478 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(),
1479 E = ReverseNonLocalDeps.end();
1481 assert(I->first != D && "Inst occurs in data structures");
1482 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1483 EE = I->second.end(); II != EE; ++II)
1484 assert(*II != D && "Inst occurs in data structures");
1487 for (ReverseNonLocalPtrDepTy::const_iterator
1488 I = ReverseNonLocalPtrDeps.begin(),
1489 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) {
1490 assert(I->first != D && "Inst occurs in rev NLPD map");
1492 for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(),
1493 E = I->second.end(); II != E; ++II)
1494 assert(*II != ValueIsLoadPair(D, false) &&
1495 *II != ValueIsLoadPair(D, true) &&
1496 "Inst occurs in ReverseNonLocalPtrDeps map");