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/Analysis/ValueTracking.h"
20 #include "llvm/Instructions.h"
21 #include "llvm/IntrinsicInst.h"
22 #include "llvm/Function.h"
23 #include "llvm/LLVMContext.h"
24 #include "llvm/Analysis/AliasAnalysis.h"
25 #include "llvm/Analysis/CaptureTracking.h"
26 #include "llvm/Analysis/Dominators.h"
27 #include "llvm/Analysis/InstructionSimplify.h"
28 #include "llvm/Analysis/MemoryBuiltins.h"
29 #include "llvm/Analysis/PHITransAddr.h"
30 #include "llvm/Analysis/ValueTracking.h"
31 #include "llvm/ADT/Statistic.h"
32 #include "llvm/ADT/STLExtras.h"
33 #include "llvm/Support/PredIteratorCache.h"
34 #include "llvm/Support/Debug.h"
35 #include "llvm/Target/TargetData.h"
38 STATISTIC(NumCacheNonLocal, "Number of fully cached non-local responses");
39 STATISTIC(NumCacheDirtyNonLocal, "Number of dirty cached non-local responses");
40 STATISTIC(NumUncacheNonLocal, "Number of uncached non-local responses");
42 STATISTIC(NumCacheNonLocalPtr,
43 "Number of fully cached non-local ptr responses");
44 STATISTIC(NumCacheDirtyNonLocalPtr,
45 "Number of cached, but dirty, non-local ptr responses");
46 STATISTIC(NumUncacheNonLocalPtr,
47 "Number of uncached non-local ptr responses");
48 STATISTIC(NumCacheCompleteNonLocalPtr,
49 "Number of block queries that were completely cached");
51 // Limit for the number of instructions to scan in a block.
52 // FIXME: Figure out what a sane value is for this.
53 // (500 is relatively insane.)
54 static const int BlockScanLimit = 500;
56 char MemoryDependenceAnalysis::ID = 0;
58 // Register this pass...
59 INITIALIZE_PASS_BEGIN(MemoryDependenceAnalysis, "memdep",
60 "Memory Dependence Analysis", false, true)
61 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
62 INITIALIZE_PASS_END(MemoryDependenceAnalysis, "memdep",
63 "Memory Dependence Analysis", false, true)
65 MemoryDependenceAnalysis::MemoryDependenceAnalysis()
66 : FunctionPass(ID), PredCache(0) {
67 initializeMemoryDependenceAnalysisPass(*PassRegistry::getPassRegistry());
69 MemoryDependenceAnalysis::~MemoryDependenceAnalysis() {
72 /// Clean up memory in between runs
73 void MemoryDependenceAnalysis::releaseMemory() {
76 NonLocalPointerDeps.clear();
77 ReverseLocalDeps.clear();
78 ReverseNonLocalDeps.clear();
79 ReverseNonLocalPtrDeps.clear();
85 /// getAnalysisUsage - Does not modify anything. It uses Alias Analysis.
87 void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
89 AU.addRequiredTransitive<AliasAnalysis>();
92 bool MemoryDependenceAnalysis::runOnFunction(Function &) {
93 AA = &getAnalysis<AliasAnalysis>();
94 TD = getAnalysisIfAvailable<TargetData>();
95 DT = getAnalysisIfAvailable<DominatorTree>();
97 PredCache.reset(new PredIteratorCache());
101 /// RemoveFromReverseMap - This is a helper function that removes Val from
102 /// 'Inst's set in ReverseMap. If the set becomes empty, remove Inst's entry.
103 template <typename KeyTy>
104 static void RemoveFromReverseMap(DenseMap<Instruction*,
105 SmallPtrSet<KeyTy, 4> > &ReverseMap,
106 Instruction *Inst, KeyTy Val) {
107 typename DenseMap<Instruction*, SmallPtrSet<KeyTy, 4> >::iterator
108 InstIt = ReverseMap.find(Inst);
109 assert(InstIt != ReverseMap.end() && "Reverse map out of sync?");
110 bool Found = InstIt->second.erase(Val);
111 assert(Found && "Invalid reverse map!"); (void)Found;
112 if (InstIt->second.empty())
113 ReverseMap.erase(InstIt);
116 /// GetLocation - If the given instruction references a specific memory
117 /// location, fill in Loc with the details, otherwise set Loc.Ptr to null.
118 /// Return a ModRefInfo value describing the general behavior of the
121 AliasAnalysis::ModRefResult GetLocation(const Instruction *Inst,
122 AliasAnalysis::Location &Loc,
124 if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
125 if (LI->isUnordered()) {
126 Loc = AA->getLocation(LI);
127 return AliasAnalysis::Ref;
128 } else if (LI->getOrdering() == Monotonic) {
129 Loc = AA->getLocation(LI);
130 return AliasAnalysis::ModRef;
132 Loc = AliasAnalysis::Location();
133 return AliasAnalysis::ModRef;
136 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
137 if (SI->isUnordered()) {
138 Loc = AA->getLocation(SI);
139 return AliasAnalysis::Mod;
140 } else if (SI->getOrdering() == Monotonic) {
141 Loc = AA->getLocation(SI);
142 return AliasAnalysis::ModRef;
144 Loc = AliasAnalysis::Location();
145 return AliasAnalysis::ModRef;
148 if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
149 Loc = AA->getLocation(V);
150 return AliasAnalysis::ModRef;
153 if (const CallInst *CI = isFreeCall(Inst)) {
154 // calls to free() deallocate the entire structure
155 Loc = AliasAnalysis::Location(CI->getArgOperand(0));
156 return AliasAnalysis::Mod;
159 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst))
160 switch (II->getIntrinsicID()) {
161 case Intrinsic::lifetime_start:
162 case Intrinsic::lifetime_end:
163 case Intrinsic::invariant_start:
164 Loc = AliasAnalysis::Location(II->getArgOperand(1),
165 cast<ConstantInt>(II->getArgOperand(0))
167 II->getMetadata(LLVMContext::MD_tbaa));
168 // These intrinsics don't really modify the memory, but returning Mod
169 // will allow them to be handled conservatively.
170 return AliasAnalysis::Mod;
171 case Intrinsic::invariant_end:
172 Loc = AliasAnalysis::Location(II->getArgOperand(2),
173 cast<ConstantInt>(II->getArgOperand(1))
175 II->getMetadata(LLVMContext::MD_tbaa));
176 // These intrinsics don't really modify the memory, but returning Mod
177 // will allow them to be handled conservatively.
178 return AliasAnalysis::Mod;
183 // Otherwise, just do the coarse-grained thing that always works.
184 if (Inst->mayWriteToMemory())
185 return AliasAnalysis::ModRef;
186 if (Inst->mayReadFromMemory())
187 return AliasAnalysis::Ref;
188 return AliasAnalysis::NoModRef;
191 /// getCallSiteDependencyFrom - Private helper for finding the local
192 /// dependencies of a call site.
193 MemDepResult MemoryDependenceAnalysis::
194 getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
195 BasicBlock::iterator ScanIt, BasicBlock *BB) {
196 unsigned Limit = BlockScanLimit;
198 // Walk backwards through the block, looking for dependencies
199 while (ScanIt != BB->begin()) {
200 // Limit the amount of scanning we do so we don't end up with quadratic
201 // running time on extreme testcases.
204 return MemDepResult::getUnknown();
206 Instruction *Inst = --ScanIt;
208 // If this inst is a memory op, get the pointer it accessed
209 AliasAnalysis::Location Loc;
210 AliasAnalysis::ModRefResult MR = GetLocation(Inst, Loc, AA);
212 // A simple instruction.
213 if (AA->getModRefInfo(CS, Loc) != AliasAnalysis::NoModRef)
214 return MemDepResult::getClobber(Inst);
218 if (CallSite InstCS = cast<Value>(Inst)) {
219 // Debug intrinsics don't cause dependences.
220 if (isa<DbgInfoIntrinsic>(Inst)) continue;
221 // If these two calls do not interfere, look past it.
222 switch (AA->getModRefInfo(CS, InstCS)) {
223 case AliasAnalysis::NoModRef:
224 // If the two calls are the same, return InstCS as a Def, so that
225 // CS can be found redundant and eliminated.
226 if (isReadOnlyCall && !(MR & AliasAnalysis::Mod) &&
227 CS.getInstruction()->isIdenticalToWhenDefined(Inst))
228 return MemDepResult::getDef(Inst);
230 // Otherwise if the two calls don't interact (e.g. InstCS is readnone)
234 return MemDepResult::getClobber(Inst);
239 // No dependence found. If this is the entry block of the function, it is
240 // unknown, otherwise it is non-local.
241 if (BB != &BB->getParent()->getEntryBlock())
242 return MemDepResult::getNonLocal();
243 return MemDepResult::getNonFuncLocal();
246 /// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
247 /// would fully overlap MemLoc if done as a wider legal integer load.
249 /// MemLocBase, MemLocOffset are lazily computed here the first time the
250 /// base/offs of memloc is needed.
252 isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc,
253 const Value *&MemLocBase,
256 const TargetData *TD) {
257 // If we have no target data, we can't do this.
258 if (TD == 0) return false;
260 // If we haven't already computed the base/offset of MemLoc, do so now.
262 MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, *TD);
264 unsigned Size = MemoryDependenceAnalysis::
265 getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size,
270 /// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that
271 /// looks at a memory location for a load (specified by MemLocBase, Offs,
272 /// and Size) and compares it against a load. If the specified load could
273 /// be safely widened to a larger integer load that is 1) still efficient,
274 /// 2) safe for the target, and 3) would provide the specified memory
275 /// location value, then this function returns the size in bytes of the
276 /// load width to use. If not, this returns zero.
277 unsigned MemoryDependenceAnalysis::
278 getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
279 unsigned MemLocSize, const LoadInst *LI,
280 const TargetData &TD) {
281 // We can only extend simple integer loads.
282 if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0;
284 // Get the base of this load.
286 const Value *LIBase =
287 GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, TD);
289 // If the two pointers are not based on the same pointer, we can't tell that
291 if (LIBase != MemLocBase) return 0;
293 // Okay, the two values are based on the same pointer, but returned as
294 // no-alias. This happens when we have things like two byte loads at "P+1"
295 // and "P+3". Check to see if increasing the size of the "LI" load up to its
296 // alignment (or the largest native integer type) will allow us to load all
297 // the bits required by MemLoc.
299 // If MemLoc is before LI, then no widening of LI will help us out.
300 if (MemLocOffs < LIOffs) return 0;
302 // Get the alignment of the load in bytes. We assume that it is safe to load
303 // any legal integer up to this size without a problem. For example, if we're
304 // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can
305 // widen it up to an i32 load. If it is known 2-byte aligned, we can widen it
307 unsigned LoadAlign = LI->getAlignment();
309 int64_t MemLocEnd = MemLocOffs+MemLocSize;
311 // If no amount of rounding up will let MemLoc fit into LI, then bail out.
312 if (LIOffs+LoadAlign < MemLocEnd) return 0;
314 // This is the size of the load to try. Start with the next larger power of
316 unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U;
317 NewLoadByteSize = NextPowerOf2(NewLoadByteSize);
320 // If this load size is bigger than our known alignment or would not fit
321 // into a native integer register, then we fail.
322 if (NewLoadByteSize > LoadAlign ||
323 !TD.fitsInLegalInteger(NewLoadByteSize*8))
326 // If a load of this width would include all of MemLoc, then we succeed.
327 if (LIOffs+NewLoadByteSize >= MemLocEnd)
328 return NewLoadByteSize;
330 NewLoadByteSize <<= 1;
337 /// Only find pointer captures which happen before the given instruction. Uses
338 /// the dominator tree to determine whether one instruction is before another.
339 struct CapturesBefore {
340 CapturesBefore(const Instruction *I, DominatorTree *DT)
341 : BeforeHere(I), DT(DT), Captured(false) {}
343 void tooManyUses() { Captured = true; }
345 bool shouldExplore(Use *U) {
346 Instruction *I = cast<Instruction>(U->getUser());
347 if (BeforeHere != I && DT->dominates(BeforeHere, I))
352 bool captured(Instruction *I) {
353 if (BeforeHere != I && DT->dominates(BeforeHere, I))
359 const Instruction *BeforeHere;
366 AliasAnalysis::ModRefResult
367 MemoryDependenceAnalysis::getModRefInfo(const Instruction *Inst,
368 const AliasAnalysis::Location &MemLoc) {
369 AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc);
370 if (MR != AliasAnalysis::ModRef) return MR;
372 // FIXME: this is really just shoring-up a deficiency in alias analysis.
373 // BasicAA isn't willing to spend linear time determining whether an alloca
374 // was captured before or after this particular call, while we are. However,
375 // with a smarter AA in place, this test is just wasting compile time.
376 if (!DT) return AliasAnalysis::ModRef;
377 const Value *Object = GetUnderlyingObject(MemLoc.Ptr, TD);
378 if (!isIdentifiedObject(Object) || isa<GlobalVariable>(Object))
379 return AliasAnalysis::ModRef;
380 ImmutableCallSite CS(Inst);
381 if (!CS.getInstruction()) return AliasAnalysis::ModRef;
383 CapturesBefore CB(Inst, DT);
384 llvm::PointerMayBeCaptured(Object, CB);
386 if (isa<Constant>(Object) || CS.getInstruction() == Object || CB.Captured)
387 return AliasAnalysis::ModRef;
390 for (ImmutableCallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
391 CI != CE; ++CI, ++ArgNo) {
392 // Only look at the no-capture or byval pointer arguments. If this
393 // pointer were passed to arguments that were neither of these, then it
394 // couldn't be no-capture.
395 if (!(*CI)->getType()->isPointerTy() ||
396 (!CS.doesNotCapture(ArgNo) && !CS.isByValArgument(ArgNo)))
399 // If this is a no-capture pointer argument, see if we can tell that it
400 // is impossible to alias the pointer we're checking. If not, we have to
401 // assume that the call could touch the pointer, even though it doesn't
403 if (!AA->isNoAlias(AliasAnalysis::Location(*CI),
404 AliasAnalysis::Location(Object))) {
405 return AliasAnalysis::ModRef;
408 return AliasAnalysis::NoModRef;
411 /// getPointerDependencyFrom - Return the instruction on which a memory
412 /// location depends. If isLoad is true, this routine ignores may-aliases with
413 /// read-only operations. If isLoad is false, this routine ignores may-aliases
414 /// with reads from read-only locations.
415 MemDepResult MemoryDependenceAnalysis::
416 getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
417 BasicBlock::iterator ScanIt, BasicBlock *BB) {
419 const Value *MemLocBase = 0;
420 int64_t MemLocOffset = 0;
422 unsigned Limit = BlockScanLimit;
424 // Walk backwards through the basic block, looking for dependencies.
425 while (ScanIt != BB->begin()) {
426 // Limit the amount of scanning we do so we don't end up with quadratic
427 // running time on extreme testcases.
430 return MemDepResult::getUnknown();
432 Instruction *Inst = --ScanIt;
434 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
435 // Debug intrinsics don't (and can't) cause dependences.
436 if (isa<DbgInfoIntrinsic>(II)) continue;
438 // If we reach a lifetime begin or end marker, then the query ends here
439 // because the value is undefined.
440 if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
441 // FIXME: This only considers queries directly on the invariant-tagged
442 // pointer, not on query pointers that are indexed off of them. It'd
443 // be nice to handle that at some point (the right approach is to use
444 // GetPointerBaseWithConstantOffset).
445 if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)),
447 return MemDepResult::getDef(II);
452 // Values depend on loads if the pointers are must aliased. This means that
453 // a load depends on another must aliased load from the same value.
454 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
455 // Atomic loads have complications involved.
456 // FIXME: This is overly conservative.
457 if (!LI->isUnordered())
458 return MemDepResult::getClobber(LI);
460 AliasAnalysis::Location LoadLoc = AA->getLocation(LI);
462 // If we found a pointer, check if it could be the same as our pointer.
463 AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc);
466 if (R == AliasAnalysis::NoAlias) {
467 // If this is an over-aligned integer load (for example,
468 // "load i8* %P, align 4") see if it would obviously overlap with the
469 // queried location if widened to a larger load (e.g. if the queried
470 // location is 1 byte at P+1). If so, return it as a load/load
471 // clobber result, allowing the client to decide to widen the load if
473 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
474 if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() &&
475 isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase,
476 MemLocOffset, LI, TD))
477 return MemDepResult::getClobber(Inst);
482 // Must aliased loads are defs of each other.
483 if (R == AliasAnalysis::MustAlias)
484 return MemDepResult::getDef(Inst);
486 #if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads
487 // in terms of clobbering loads, but since it does this by looking
488 // at the clobbering load directly, it doesn't know about any
489 // phi translation that may have happened along the way.
491 // If we have a partial alias, then return this as a clobber for the
493 if (R == AliasAnalysis::PartialAlias)
494 return MemDepResult::getClobber(Inst);
497 // Random may-alias loads don't depend on each other without a
502 // Stores don't depend on other no-aliased accesses.
503 if (R == AliasAnalysis::NoAlias)
506 // Stores don't alias loads from read-only memory.
507 if (AA->pointsToConstantMemory(LoadLoc))
510 // Stores depend on may/must aliased loads.
511 return MemDepResult::getDef(Inst);
514 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
515 // Atomic stores have complications involved.
516 // FIXME: This is overly conservative.
517 if (!SI->isUnordered())
518 return MemDepResult::getClobber(SI);
520 // If alias analysis can tell that this store is guaranteed to not modify
521 // the query pointer, ignore it. Use getModRefInfo to handle cases where
522 // the query pointer points to constant memory etc.
523 if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef)
526 // Ok, this store might clobber the query pointer. Check to see if it is
527 // a must alias: in this case, we want to return this as a def.
528 AliasAnalysis::Location StoreLoc = AA->getLocation(SI);
530 // If we found a pointer, check if it could be the same as our pointer.
531 AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc);
533 if (R == AliasAnalysis::NoAlias)
535 if (R == AliasAnalysis::MustAlias)
536 return MemDepResult::getDef(Inst);
537 return MemDepResult::getClobber(Inst);
540 // If this is an allocation, and if we know that the accessed pointer is to
541 // the allocation, return Def. This means that there is no dependence and
542 // the access can be optimized based on that. For example, a load could
544 // Note: Only determine this to be a malloc if Inst is the malloc call, not
545 // a subsequent bitcast of the malloc call result. There can be stores to
546 // the malloced memory between the malloc call and its bitcast uses, and we
547 // need to continue scanning until the malloc call.
548 if (isa<AllocaInst>(Inst) ||
549 (isa<CallInst>(Inst) && extractMallocCall(Inst))) {
550 const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, TD);
552 if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
553 return MemDepResult::getDef(Inst);
557 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
558 switch (getModRefInfo(Inst, MemLoc)) {
559 case AliasAnalysis::NoModRef:
560 // If the call has no effect on the queried pointer, just ignore it.
562 case AliasAnalysis::Mod:
563 return MemDepResult::getClobber(Inst);
564 case AliasAnalysis::Ref:
565 // If the call is known to never store to the pointer, and if this is a
566 // load query, we can safely ignore it (scan past it).
570 // Otherwise, there is a potential dependence. Return a clobber.
571 return MemDepResult::getClobber(Inst);
575 // No dependence found. If this is the entry block of the function, it is
576 // unknown, otherwise it is non-local.
577 if (BB != &BB->getParent()->getEntryBlock())
578 return MemDepResult::getNonLocal();
579 return MemDepResult::getNonFuncLocal();
582 /// getDependency - Return the instruction on which a memory operation
584 MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
585 Instruction *ScanPos = QueryInst;
587 // Check for a cached result
588 MemDepResult &LocalCache = LocalDeps[QueryInst];
590 // If the cached entry is non-dirty, just return it. Note that this depends
591 // on MemDepResult's default constructing to 'dirty'.
592 if (!LocalCache.isDirty())
595 // Otherwise, if we have a dirty entry, we know we can start the scan at that
596 // instruction, which may save us some work.
597 if (Instruction *Inst = LocalCache.getInst()) {
600 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst);
603 BasicBlock *QueryParent = QueryInst->getParent();
606 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
607 // No dependence found. If this is the entry block of the function, it is
608 // unknown, otherwise it is non-local.
609 if (QueryParent != &QueryParent->getParent()->getEntryBlock())
610 LocalCache = MemDepResult::getNonLocal();
612 LocalCache = MemDepResult::getNonFuncLocal();
614 AliasAnalysis::Location MemLoc;
615 AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
617 // If we can do a pointer scan, make it happen.
618 bool isLoad = !(MR & AliasAnalysis::Mod);
619 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst))
620 isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start;
622 LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos,
624 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
625 CallSite QueryCS(QueryInst);
626 bool isReadOnly = AA->onlyReadsMemory(QueryCS);
627 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos,
630 // Non-memory instruction.
631 LocalCache = MemDepResult::getUnknown();
634 // Remember the result!
635 if (Instruction *I = LocalCache.getInst())
636 ReverseLocalDeps[I].insert(QueryInst);
642 /// AssertSorted - This method is used when -debug is specified to verify that
643 /// cache arrays are properly kept sorted.
644 static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
646 if (Count == -1) Count = Cache.size();
647 if (Count == 0) return;
649 for (unsigned i = 1; i != unsigned(Count); ++i)
650 assert(!(Cache[i] < Cache[i-1]) && "Cache isn't sorted!");
654 /// getNonLocalCallDependency - Perform a full dependency query for the
655 /// specified call, returning the set of blocks that the value is
656 /// potentially live across. The returned set of results will include a
657 /// "NonLocal" result for all blocks where the value is live across.
659 /// This method assumes the instruction returns a "NonLocal" dependency
660 /// within its own block.
662 /// This returns a reference to an internal data structure that may be
663 /// invalidated on the next non-local query or when an instruction is
664 /// removed. Clients must copy this data if they want it around longer than
666 const MemoryDependenceAnalysis::NonLocalDepInfo &
667 MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
668 assert(getDependency(QueryCS.getInstruction()).isNonLocal() &&
669 "getNonLocalCallDependency should only be used on calls with non-local deps!");
670 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()];
671 NonLocalDepInfo &Cache = CacheP.first;
673 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In
674 /// the cached case, this can happen due to instructions being deleted etc. In
675 /// the uncached case, this starts out as the set of predecessors we care
677 SmallVector<BasicBlock*, 32> DirtyBlocks;
679 if (!Cache.empty()) {
680 // Okay, we have a cache entry. If we know it is not dirty, just return it
681 // with no computation.
682 if (!CacheP.second) {
687 // If we already have a partially computed set of results, scan them to
688 // determine what is dirty, seeding our initial DirtyBlocks worklist.
689 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end();
691 if (I->getResult().isDirty())
692 DirtyBlocks.push_back(I->getBB());
694 // Sort the cache so that we can do fast binary search lookups below.
695 std::sort(Cache.begin(), Cache.end());
697 ++NumCacheDirtyNonLocal;
698 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: "
699 // << Cache.size() << " cached: " << *QueryInst;
701 // Seed DirtyBlocks with each of the preds of QueryInst's block.
702 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent();
703 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI)
704 DirtyBlocks.push_back(*PI);
705 ++NumUncacheNonLocal;
708 // isReadonlyCall - If this is a read-only call, we can be more aggressive.
709 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS);
711 SmallPtrSet<BasicBlock*, 64> Visited;
713 unsigned NumSortedEntries = Cache.size();
714 DEBUG(AssertSorted(Cache));
716 // Iterate while we still have blocks to update.
717 while (!DirtyBlocks.empty()) {
718 BasicBlock *DirtyBB = DirtyBlocks.back();
719 DirtyBlocks.pop_back();
721 // Already processed this block?
722 if (!Visited.insert(DirtyBB))
725 // Do a binary search to see if we already have an entry for this block in
726 // the cache set. If so, find it.
727 DEBUG(AssertSorted(Cache, NumSortedEntries));
728 NonLocalDepInfo::iterator Entry =
729 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries,
730 NonLocalDepEntry(DirtyBB));
731 if (Entry != Cache.begin() && prior(Entry)->getBB() == DirtyBB)
734 NonLocalDepEntry *ExistingResult = 0;
735 if (Entry != Cache.begin()+NumSortedEntries &&
736 Entry->getBB() == DirtyBB) {
737 // If we already have an entry, and if it isn't already dirty, the block
739 if (!Entry->getResult().isDirty())
742 // Otherwise, remember this slot so we can update the value.
743 ExistingResult = &*Entry;
746 // If the dirty entry has a pointer, start scanning from it so we don't have
747 // to rescan the entire block.
748 BasicBlock::iterator ScanPos = DirtyBB->end();
749 if (ExistingResult) {
750 if (Instruction *Inst = ExistingResult->getResult().getInst()) {
752 // We're removing QueryInst's use of Inst.
753 RemoveFromReverseMap(ReverseNonLocalDeps, Inst,
754 QueryCS.getInstruction());
758 // Find out if this block has a local dependency for QueryInst.
761 if (ScanPos != DirtyBB->begin()) {
762 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
763 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
764 // No dependence found. If this is the entry block of the function, it is
765 // a clobber, otherwise it is unknown.
766 Dep = MemDepResult::getNonLocal();
768 Dep = MemDepResult::getNonFuncLocal();
771 // If we had a dirty entry for the block, update it. Otherwise, just add
774 ExistingResult->setResult(Dep);
776 Cache.push_back(NonLocalDepEntry(DirtyBB, Dep));
778 // If the block has a dependency (i.e. it isn't completely transparent to
779 // the value), remember the association!
780 if (!Dep.isNonLocal()) {
781 // Keep the ReverseNonLocalDeps map up to date so we can efficiently
782 // update this when we remove instructions.
783 if (Instruction *Inst = Dep.getInst())
784 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction());
787 // If the block *is* completely transparent to the load, we need to check
788 // the predecessors of this block. Add them to our worklist.
789 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI)
790 DirtyBlocks.push_back(*PI);
797 /// getNonLocalPointerDependency - Perform a full dependency query for an
798 /// access to the specified (non-volatile) memory location, returning the
799 /// set of instructions that either define or clobber the value.
801 /// This method assumes the pointer has a "NonLocal" dependency within its
804 void MemoryDependenceAnalysis::
805 getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad,
807 SmallVectorImpl<NonLocalDepResult> &Result) {
808 assert(Loc.Ptr->getType()->isPointerTy() &&
809 "Can't get pointer deps of a non-pointer!");
812 PHITransAddr Address(const_cast<Value *>(Loc.Ptr), TD);
814 // This is the set of blocks we've inspected, and the pointer we consider in
815 // each block. Because of critical edges, we currently bail out if querying
816 // a block with multiple different pointers. This can happen during PHI
818 DenseMap<BasicBlock*, Value*> Visited;
819 if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB,
820 Result, Visited, true))
823 Result.push_back(NonLocalDepResult(FromBB,
824 MemDepResult::getUnknown(),
825 const_cast<Value *>(Loc.Ptr)));
828 /// GetNonLocalInfoForBlock - Compute the memdep value for BB with
829 /// Pointer/PointeeSize using either cached information in Cache or by doing a
830 /// lookup (which may use dirty cache info if available). If we do a lookup,
831 /// add the result to the cache.
832 MemDepResult MemoryDependenceAnalysis::
833 GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
834 bool isLoad, BasicBlock *BB,
835 NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
837 // Do a binary search to see if we already have an entry for this block in
838 // the cache set. If so, find it.
839 NonLocalDepInfo::iterator Entry =
840 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries,
841 NonLocalDepEntry(BB));
842 if (Entry != Cache->begin() && (Entry-1)->getBB() == BB)
845 NonLocalDepEntry *ExistingResult = 0;
846 if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB)
847 ExistingResult = &*Entry;
849 // If we have a cached entry, and it is non-dirty, use it as the value for
851 if (ExistingResult && !ExistingResult->getResult().isDirty()) {
852 ++NumCacheNonLocalPtr;
853 return ExistingResult->getResult();
856 // Otherwise, we have to scan for the value. If we have a dirty cache
857 // entry, start scanning from its position, otherwise we scan from the end
859 BasicBlock::iterator ScanPos = BB->end();
860 if (ExistingResult && ExistingResult->getResult().getInst()) {
861 assert(ExistingResult->getResult().getInst()->getParent() == BB &&
862 "Instruction invalidated?");
863 ++NumCacheDirtyNonLocalPtr;
864 ScanPos = ExistingResult->getResult().getInst();
866 // Eliminating the dirty entry from 'Cache', so update the reverse info.
867 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
868 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey);
870 ++NumUncacheNonLocalPtr;
873 // Scan the block for the dependency.
874 MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB);
876 // If we had a dirty entry for the block, update it. Otherwise, just add
879 ExistingResult->setResult(Dep);
881 Cache->push_back(NonLocalDepEntry(BB, Dep));
883 // If the block has a dependency (i.e. it isn't completely transparent to
884 // the value), remember the reverse association because we just added it
886 if (!Dep.isDef() && !Dep.isClobber())
889 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
890 // update MemDep when we remove instructions.
891 Instruction *Inst = Dep.getInst();
892 assert(Inst && "Didn't depend on anything?");
893 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
894 ReverseNonLocalPtrDeps[Inst].insert(CacheKey);
898 /// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain
899 /// number of elements in the array that are already properly ordered. This is
900 /// optimized for the case when only a few entries are added.
902 SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
903 unsigned NumSortedEntries) {
904 switch (Cache.size() - NumSortedEntries) {
906 // done, no new entries.
909 // Two new entries, insert the last one into place.
910 NonLocalDepEntry Val = Cache.back();
912 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
913 std::upper_bound(Cache.begin(), Cache.end()-1, Val);
914 Cache.insert(Entry, Val);
918 // One new entry, Just insert the new value at the appropriate position.
919 if (Cache.size() != 1) {
920 NonLocalDepEntry Val = Cache.back();
922 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
923 std::upper_bound(Cache.begin(), Cache.end(), Val);
924 Cache.insert(Entry, Val);
928 // Added many values, do a full scale sort.
929 std::sort(Cache.begin(), Cache.end());
934 /// getNonLocalPointerDepFromBB - Perform a dependency query based on
935 /// pointer/pointeesize starting at the end of StartBB. Add any clobber/def
936 /// results to the results vector and keep track of which blocks are visited in
939 /// This has special behavior for the first block queries (when SkipFirstBlock
940 /// is true). In this special case, it ignores the contents of the specified
941 /// block and starts returning dependence info for its predecessors.
943 /// This function returns false on success, or true to indicate that it could
944 /// not compute dependence information for some reason. This should be treated
945 /// as a clobber dependence on the first instruction in the predecessor block.
946 bool MemoryDependenceAnalysis::
947 getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
948 const AliasAnalysis::Location &Loc,
949 bool isLoad, BasicBlock *StartBB,
950 SmallVectorImpl<NonLocalDepResult> &Result,
951 DenseMap<BasicBlock*, Value*> &Visited,
952 bool SkipFirstBlock) {
954 // Look up the cached info for Pointer.
955 ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad);
957 // Set up a temporary NLPI value. If the map doesn't yet have an entry for
958 // CacheKey, this value will be inserted as the associated value. Otherwise,
959 // it'll be ignored, and we'll have to check to see if the cached size and
960 // tbaa tag are consistent with the current query.
961 NonLocalPointerInfo InitialNLPI;
962 InitialNLPI.Size = Loc.Size;
963 InitialNLPI.TBAATag = Loc.TBAATag;
965 // Get the NLPI for CacheKey, inserting one into the map if it doesn't
967 std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair =
968 NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI));
969 NonLocalPointerInfo *CacheInfo = &Pair.first->second;
971 // If we already have a cache entry for this CacheKey, we may need to do some
972 // work to reconcile the cache entry and the current query.
974 if (CacheInfo->Size < Loc.Size) {
975 // The query's Size is greater than the cached one. Throw out the
976 // cached data and procede with the query at the greater size.
977 CacheInfo->Pair = BBSkipFirstBlockPair();
978 CacheInfo->Size = Loc.Size;
979 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
980 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
981 if (Instruction *Inst = DI->getResult().getInst())
982 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
983 CacheInfo->NonLocalDeps.clear();
984 } else if (CacheInfo->Size > Loc.Size) {
985 // This query's Size is less than the cached one. Conservatively restart
986 // the query using the greater size.
987 return getNonLocalPointerDepFromBB(Pointer,
988 Loc.getWithNewSize(CacheInfo->Size),
989 isLoad, StartBB, Result, Visited,
993 // If the query's TBAATag is inconsistent with the cached one,
994 // conservatively throw out the cached data and restart the query with
996 if (CacheInfo->TBAATag != Loc.TBAATag) {
997 if (CacheInfo->TBAATag) {
998 CacheInfo->Pair = BBSkipFirstBlockPair();
999 CacheInfo->TBAATag = 0;
1000 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
1001 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
1002 if (Instruction *Inst = DI->getResult().getInst())
1003 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
1004 CacheInfo->NonLocalDeps.clear();
1007 return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(),
1008 isLoad, StartBB, Result, Visited,
1013 NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps;
1015 // If we have valid cached information for exactly the block we are
1016 // investigating, just return it with no recomputation.
1017 if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
1018 // We have a fully cached result for this query then we can just return the
1019 // cached results and populate the visited set. However, we have to verify
1020 // that we don't already have conflicting results for these blocks. Check
1021 // to ensure that if a block in the results set is in the visited set that
1022 // it was for the same pointer query.
1023 if (!Visited.empty()) {
1024 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
1026 DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->getBB());
1027 if (VI == Visited.end() || VI->second == Pointer.getAddr())
1030 // We have a pointer mismatch in a block. Just return clobber, saying
1031 // that something was clobbered in this result. We could also do a
1032 // non-fully cached query, but there is little point in doing this.
1037 Value *Addr = Pointer.getAddr();
1038 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
1040 Visited.insert(std::make_pair(I->getBB(), Addr));
1041 if (!I->getResult().isNonLocal())
1042 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr));
1044 ++NumCacheCompleteNonLocalPtr;
1048 // Otherwise, either this is a new block, a block with an invalid cache
1049 // pointer or one that we're about to invalidate by putting more info into it
1050 // than its valid cache info. If empty, the result will be valid cache info,
1051 // otherwise it isn't.
1053 CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
1055 CacheInfo->Pair = BBSkipFirstBlockPair();
1057 SmallVector<BasicBlock*, 32> Worklist;
1058 Worklist.push_back(StartBB);
1060 // PredList used inside loop.
1061 SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList;
1063 // Keep track of the entries that we know are sorted. Previously cached
1064 // entries will all be sorted. The entries we add we only sort on demand (we
1065 // don't insert every element into its sorted position). We know that we
1066 // won't get any reuse from currently inserted values, because we don't
1067 // revisit blocks after we insert info for them.
1068 unsigned NumSortedEntries = Cache->size();
1069 DEBUG(AssertSorted(*Cache));
1071 while (!Worklist.empty()) {
1072 BasicBlock *BB = Worklist.pop_back_val();
1074 // Skip the first block if we have it.
1075 if (!SkipFirstBlock) {
1076 // Analyze the dependency of *Pointer in FromBB. See if we already have
1078 assert(Visited.count(BB) && "Should check 'visited' before adding to WL");
1080 // Get the dependency info for Pointer in BB. If we have cached
1081 // information, we will use it, otherwise we compute it.
1082 DEBUG(AssertSorted(*Cache, NumSortedEntries));
1083 MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache,
1086 // If we got a Def or Clobber, add this to the list of results.
1087 if (!Dep.isNonLocal()) {
1088 Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr()));
1093 // If 'Pointer' is an instruction defined in this block, then we need to do
1094 // phi translation to change it into a value live in the predecessor block.
1095 // If not, we just add the predecessors to the worklist and scan them with
1096 // the same Pointer.
1097 if (!Pointer.NeedsPHITranslationFromBlock(BB)) {
1098 SkipFirstBlock = false;
1099 SmallVector<BasicBlock*, 16> NewBlocks;
1100 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1101 // Verify that we haven't looked at this block yet.
1102 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1103 InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr()));
1104 if (InsertRes.second) {
1105 // First time we've looked at *PI.
1106 NewBlocks.push_back(*PI);
1110 // If we have seen this block before, but it was with a different
1111 // pointer then we have a phi translation failure and we have to treat
1112 // this as a clobber.
1113 if (InsertRes.first->second != Pointer.getAddr()) {
1114 // Make sure to clean up the Visited map before continuing on to
1115 // PredTranslationFailure.
1116 for (unsigned i = 0; i < NewBlocks.size(); i++)
1117 Visited.erase(NewBlocks[i]);
1118 goto PredTranslationFailure;
1121 Worklist.append(NewBlocks.begin(), NewBlocks.end());
1125 // We do need to do phi translation, if we know ahead of time we can't phi
1126 // translate this value, don't even try.
1127 if (!Pointer.IsPotentiallyPHITranslatable())
1128 goto PredTranslationFailure;
1130 // We may have added values to the cache list before this PHI translation.
1131 // If so, we haven't done anything to ensure that the cache remains sorted.
1132 // Sort it now (if needed) so that recursive invocations of
1133 // getNonLocalPointerDepFromBB and other routines that could reuse the cache
1134 // value will only see properly sorted cache arrays.
1135 if (Cache && NumSortedEntries != Cache->size()) {
1136 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1137 NumSortedEntries = Cache->size();
1142 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1143 BasicBlock *Pred = *PI;
1144 PredList.push_back(std::make_pair(Pred, Pointer));
1146 // Get the PHI translated pointer in this predecessor. This can fail if
1147 // not translatable, in which case the getAddr() returns null.
1148 PHITransAddr &PredPointer = PredList.back().second;
1149 PredPointer.PHITranslateValue(BB, Pred, 0);
1151 Value *PredPtrVal = PredPointer.getAddr();
1153 // Check to see if we have already visited this pred block with another
1154 // pointer. If so, we can't do this lookup. This failure can occur
1155 // with PHI translation when a critical edge exists and the PHI node in
1156 // the successor translates to a pointer value different than the
1157 // pointer the block was first analyzed with.
1158 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1159 InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal));
1161 if (!InsertRes.second) {
1162 // We found the pred; take it off the list of preds to visit.
1163 PredList.pop_back();
1165 // If the predecessor was visited with PredPtr, then we already did
1166 // the analysis and can ignore it.
1167 if (InsertRes.first->second == PredPtrVal)
1170 // Otherwise, the block was previously analyzed with a different
1171 // pointer. We can't represent the result of this case, so we just
1172 // treat this as a phi translation failure.
1174 // Make sure to clean up the Visited map before continuing on to
1175 // PredTranslationFailure.
1176 for (unsigned i = 0; i < PredList.size(); i++)
1177 Visited.erase(PredList[i].first);
1179 goto PredTranslationFailure;
1183 // Actually process results here; this need to be a separate loop to avoid
1184 // calling getNonLocalPointerDepFromBB for blocks we don't want to return
1185 // any results for. (getNonLocalPointerDepFromBB will modify our
1186 // datastructures in ways the code after the PredTranslationFailure label
1188 for (unsigned i = 0; i < PredList.size(); i++) {
1189 BasicBlock *Pred = PredList[i].first;
1190 PHITransAddr &PredPointer = PredList[i].second;
1191 Value *PredPtrVal = PredPointer.getAddr();
1193 bool CanTranslate = true;
1194 // If PHI translation was unable to find an available pointer in this
1195 // predecessor, then we have to assume that the pointer is clobbered in
1196 // that predecessor. We can still do PRE of the load, which would insert
1197 // a computation of the pointer in this predecessor.
1198 if (PredPtrVal == 0)
1199 CanTranslate = false;
1201 // FIXME: it is entirely possible that PHI translating will end up with
1202 // the same value. Consider PHI translating something like:
1203 // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need*
1204 // to recurse here, pedantically speaking.
1206 // If getNonLocalPointerDepFromBB fails here, that means the cached
1207 // result conflicted with the Visited list; we have to conservatively
1208 // assume it is unknown, but this also does not block PRE of the load.
1209 if (!CanTranslate ||
1210 getNonLocalPointerDepFromBB(PredPointer,
1211 Loc.getWithNewPtr(PredPtrVal),
1214 // Add the entry to the Result list.
1215 NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal);
1216 Result.push_back(Entry);
1218 // Since we had a phi translation failure, the cache for CacheKey won't
1219 // include all of the entries that we need to immediately satisfy future
1220 // queries. Mark this in NonLocalPointerDeps by setting the
1221 // BBSkipFirstBlockPair pointer to null. This requires reuse of the
1222 // cached value to do more work but not miss the phi trans failure.
1223 NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey];
1224 NLPI.Pair = BBSkipFirstBlockPair();
1229 // Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
1230 CacheInfo = &NonLocalPointerDeps[CacheKey];
1231 Cache = &CacheInfo->NonLocalDeps;
1232 NumSortedEntries = Cache->size();
1234 // Since we did phi translation, the "Cache" set won't contain all of the
1235 // results for the query. This is ok (we can still use it to accelerate
1236 // specific block queries) but we can't do the fastpath "return all
1237 // results from the set" Clear out the indicator for this.
1238 CacheInfo->Pair = BBSkipFirstBlockPair();
1239 SkipFirstBlock = false;
1242 PredTranslationFailure:
1243 // The following code is "failure"; we can't produce a sane translation
1244 // for the given block. It assumes that we haven't modified any of
1245 // our datastructures while processing the current block.
1248 // Refresh the CacheInfo/Cache pointer if it got invalidated.
1249 CacheInfo = &NonLocalPointerDeps[CacheKey];
1250 Cache = &CacheInfo->NonLocalDeps;
1251 NumSortedEntries = Cache->size();
1254 // Since we failed phi translation, the "Cache" set won't contain all of the
1255 // results for the query. This is ok (we can still use it to accelerate
1256 // specific block queries) but we can't do the fastpath "return all
1257 // results from the set". Clear out the indicator for this.
1258 CacheInfo->Pair = BBSkipFirstBlockPair();
1260 // If *nothing* works, mark the pointer as unknown.
1262 // If this is the magic first block, return this as a clobber of the whole
1263 // incoming value. Since we can't phi translate to one of the predecessors,
1264 // we have to bail out.
1268 for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) {
1269 assert(I != Cache->rend() && "Didn't find current block??");
1270 if (I->getBB() != BB)
1273 assert(I->getResult().isNonLocal() &&
1274 "Should only be here with transparent block");
1275 I->setResult(MemDepResult::getUnknown());
1276 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(),
1277 Pointer.getAddr()));
1282 // Okay, we're done now. If we added new values to the cache, re-sort it.
1283 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1284 DEBUG(AssertSorted(*Cache));
1288 /// RemoveCachedNonLocalPointerDependencies - If P exists in
1289 /// CachedNonLocalPointerInfo, remove it.
1290 void MemoryDependenceAnalysis::
1291 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) {
1292 CachedNonLocalPointerInfo::iterator It =
1293 NonLocalPointerDeps.find(P);
1294 if (It == NonLocalPointerDeps.end()) return;
1296 // Remove all of the entries in the BB->val map. This involves removing
1297 // instructions from the reverse map.
1298 NonLocalDepInfo &PInfo = It->second.NonLocalDeps;
1300 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
1301 Instruction *Target = PInfo[i].getResult().getInst();
1302 if (Target == 0) continue; // Ignore non-local dep results.
1303 assert(Target->getParent() == PInfo[i].getBB());
1305 // Eliminating the dirty entry from 'Cache', so update the reverse info.
1306 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P);
1309 // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo).
1310 NonLocalPointerDeps.erase(It);
1314 /// invalidateCachedPointerInfo - This method is used to invalidate cached
1315 /// information about the specified pointer, because it may be too
1316 /// conservative in memdep. This is an optional call that can be used when
1317 /// the client detects an equivalence between the pointer and some other
1318 /// value and replaces the other value with ptr. This can make Ptr available
1319 /// in more places that cached info does not necessarily keep.
1320 void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) {
1321 // If Ptr isn't really a pointer, just ignore it.
1322 if (!Ptr->getType()->isPointerTy()) return;
1323 // Flush store info for the pointer.
1324 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false));
1325 // Flush load info for the pointer.
1326 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true));
1329 /// invalidateCachedPredecessors - Clear the PredIteratorCache info.
1330 /// This needs to be done when the CFG changes, e.g., due to splitting
1332 void MemoryDependenceAnalysis::invalidateCachedPredecessors() {
1336 /// removeInstruction - Remove an instruction from the dependence analysis,
1337 /// updating the dependence of instructions that previously depended on it.
1338 /// This method attempts to keep the cache coherent using the reverse map.
1339 void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) {
1340 // Walk through the Non-local dependencies, removing this one as the value
1341 // for any cached queries.
1342 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst);
1343 if (NLDI != NonLocalDeps.end()) {
1344 NonLocalDepInfo &BlockMap = NLDI->second.first;
1345 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end();
1347 if (Instruction *Inst = DI->getResult().getInst())
1348 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst);
1349 NonLocalDeps.erase(NLDI);
1352 // If we have a cached local dependence query for this instruction, remove it.
1354 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst);
1355 if (LocalDepEntry != LocalDeps.end()) {
1356 // Remove us from DepInst's reverse set now that the local dep info is gone.
1357 if (Instruction *Inst = LocalDepEntry->second.getInst())
1358 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst);
1360 // Remove this local dependency info.
1361 LocalDeps.erase(LocalDepEntry);
1364 // If we have any cached pointer dependencies on this instruction, remove
1365 // them. If the instruction has non-pointer type, then it can't be a pointer
1368 // Remove it from both the load info and the store info. The instruction
1369 // can't be in either of these maps if it is non-pointer.
1370 if (RemInst->getType()->isPointerTy()) {
1371 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false));
1372 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true));
1375 // Loop over all of the things that depend on the instruction we're removing.
1377 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd;
1379 // If we find RemInst as a clobber or Def in any of the maps for other values,
1380 // we need to replace its entry with a dirty version of the instruction after
1381 // it. If RemInst is a terminator, we use a null dirty value.
1383 // Using a dirty version of the instruction after RemInst saves having to scan
1384 // the entire block to get to this point.
1385 MemDepResult NewDirtyVal;
1386 if (!RemInst->isTerminator())
1387 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst));
1389 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst);
1390 if (ReverseDepIt != ReverseLocalDeps.end()) {
1391 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second;
1392 // RemInst can't be the terminator if it has local stuff depending on it.
1393 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) &&
1394 "Nothing can locally depend on a terminator");
1396 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(),
1397 E = ReverseDeps.end(); I != E; ++I) {
1398 Instruction *InstDependingOnRemInst = *I;
1399 assert(InstDependingOnRemInst != RemInst &&
1400 "Already removed our local dep info");
1402 LocalDeps[InstDependingOnRemInst] = NewDirtyVal;
1404 // Make sure to remember that new things depend on NewDepInst.
1405 assert(NewDirtyVal.getInst() && "There is no way something else can have "
1406 "a local dep on this if it is a terminator!");
1407 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(),
1408 InstDependingOnRemInst));
1411 ReverseLocalDeps.erase(ReverseDepIt);
1413 // Add new reverse deps after scanning the set, to avoid invalidating the
1414 // 'ReverseDeps' reference.
1415 while (!ReverseDepsToAdd.empty()) {
1416 ReverseLocalDeps[ReverseDepsToAdd.back().first]
1417 .insert(ReverseDepsToAdd.back().second);
1418 ReverseDepsToAdd.pop_back();
1422 ReverseDepIt = ReverseNonLocalDeps.find(RemInst);
1423 if (ReverseDepIt != ReverseNonLocalDeps.end()) {
1424 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second;
1425 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end();
1427 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst");
1429 PerInstNLInfo &INLD = NonLocalDeps[*I];
1430 // The information is now dirty!
1433 for (NonLocalDepInfo::iterator DI = INLD.first.begin(),
1434 DE = INLD.first.end(); DI != DE; ++DI) {
1435 if (DI->getResult().getInst() != RemInst) continue;
1437 // Convert to a dirty entry for the subsequent instruction.
1438 DI->setResult(NewDirtyVal);
1440 if (Instruction *NextI = NewDirtyVal.getInst())
1441 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I));
1445 ReverseNonLocalDeps.erase(ReverseDepIt);
1447 // Add new reverse deps after scanning the set, to avoid invalidating 'Set'
1448 while (!ReverseDepsToAdd.empty()) {
1449 ReverseNonLocalDeps[ReverseDepsToAdd.back().first]
1450 .insert(ReverseDepsToAdd.back().second);
1451 ReverseDepsToAdd.pop_back();
1455 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a
1456 // value in the NonLocalPointerDeps info.
1457 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt =
1458 ReverseNonLocalPtrDeps.find(RemInst);
1459 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) {
1460 SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second;
1461 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd;
1463 for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(),
1464 E = Set.end(); I != E; ++I) {
1465 ValueIsLoadPair P = *I;
1466 assert(P.getPointer() != RemInst &&
1467 "Already removed NonLocalPointerDeps info for RemInst");
1469 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps;
1471 // The cache is not valid for any specific block anymore.
1472 NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair();
1474 // Update any entries for RemInst to use the instruction after it.
1475 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
1477 if (DI->getResult().getInst() != RemInst) continue;
1479 // Convert to a dirty entry for the subsequent instruction.
1480 DI->setResult(NewDirtyVal);
1482 if (Instruction *NewDirtyInst = NewDirtyVal.getInst())
1483 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P));
1486 // Re-sort the NonLocalDepInfo. Changing the dirty entry to its
1487 // subsequent value may invalidate the sortedness.
1488 std::sort(NLPDI.begin(), NLPDI.end());
1491 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt);
1493 while (!ReversePtrDepsToAdd.empty()) {
1494 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first]
1495 .insert(ReversePtrDepsToAdd.back().second);
1496 ReversePtrDepsToAdd.pop_back();
1501 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?");
1502 AA->deleteValue(RemInst);
1503 DEBUG(verifyRemoved(RemInst));
1505 /// verifyRemoved - Verify that the specified instruction does not occur
1506 /// in our internal data structures.
1507 void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const {
1508 for (LocalDepMapType::const_iterator I = LocalDeps.begin(),
1509 E = LocalDeps.end(); I != E; ++I) {
1510 assert(I->first != D && "Inst occurs in data structures");
1511 assert(I->second.getInst() != D &&
1512 "Inst occurs in data structures");
1515 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(),
1516 E = NonLocalPointerDeps.end(); I != E; ++I) {
1517 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key");
1518 const NonLocalDepInfo &Val = I->second.NonLocalDeps;
1519 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end();
1521 assert(II->getResult().getInst() != D && "Inst occurs as NLPD value");
1524 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(),
1525 E = NonLocalDeps.end(); I != E; ++I) {
1526 assert(I->first != D && "Inst occurs in data structures");
1527 const PerInstNLInfo &INLD = I->second;
1528 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(),
1529 EE = INLD.first.end(); II != EE; ++II)
1530 assert(II->getResult().getInst() != D && "Inst occurs in data structures");
1533 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(),
1534 E = ReverseLocalDeps.end(); I != E; ++I) {
1535 assert(I->first != D && "Inst occurs in data structures");
1536 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1537 EE = I->second.end(); II != EE; ++II)
1538 assert(*II != D && "Inst occurs in data structures");
1541 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(),
1542 E = ReverseNonLocalDeps.end();
1544 assert(I->first != D && "Inst occurs in data structures");
1545 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1546 EE = I->second.end(); II != EE; ++II)
1547 assert(*II != D && "Inst occurs in data structures");
1550 for (ReverseNonLocalPtrDepTy::const_iterator
1551 I = ReverseNonLocalPtrDeps.begin(),
1552 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) {
1553 assert(I->first != D && "Inst occurs in rev NLPD map");
1555 for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(),
1556 E = I->second.end(); II != E; ++II)
1557 assert(*II != ValueIsLoadPair(D, false) &&
1558 *II != ValueIsLoadPair(D, true) &&
1559 "Inst occurs in ReverseNonLocalPtrDeps map");