1 //===- MemoryDependenceAnalysis.cpp - Mem Deps Implementation -------------===//
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/ADT/STLExtras.h"
20 #include "llvm/ADT/Statistic.h"
21 #include "llvm/Analysis/AliasAnalysis.h"
22 #include "llvm/Analysis/InstructionSimplify.h"
23 #include "llvm/Analysis/MemoryBuiltins.h"
24 #include "llvm/Analysis/PHITransAddr.h"
25 #include "llvm/Analysis/ValueTracking.h"
26 #include "llvm/IR/DataLayout.h"
27 #include "llvm/IR/Dominators.h"
28 #include "llvm/IR/Function.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/IntrinsicInst.h"
31 #include "llvm/IR/LLVMContext.h"
32 #include "llvm/IR/PredIteratorCache.h"
33 #include "llvm/Support/Debug.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 static const int BlockScanLimit = 100;
52 char MemoryDependenceAnalysis::ID = 0;
54 // Register this pass...
55 INITIALIZE_PASS_BEGIN(MemoryDependenceAnalysis, "memdep",
56 "Memory Dependence Analysis", false, true)
57 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
58 INITIALIZE_PASS_END(MemoryDependenceAnalysis, "memdep",
59 "Memory Dependence Analysis", false, true)
61 MemoryDependenceAnalysis::MemoryDependenceAnalysis()
62 : FunctionPass(ID), PredCache() {
63 initializeMemoryDependenceAnalysisPass(*PassRegistry::getPassRegistry());
65 MemoryDependenceAnalysis::~MemoryDependenceAnalysis() {
68 /// Clean up memory in between runs
69 void MemoryDependenceAnalysis::releaseMemory() {
72 NonLocalPointerDeps.clear();
73 ReverseLocalDeps.clear();
74 ReverseNonLocalDeps.clear();
75 ReverseNonLocalPtrDeps.clear();
81 /// getAnalysisUsage - Does not modify anything. It uses Alias Analysis.
83 void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
85 AU.addRequiredTransitive<AliasAnalysis>();
88 bool MemoryDependenceAnalysis::runOnFunction(Function &) {
89 AA = &getAnalysis<AliasAnalysis>();
90 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
91 DL = DLP ? &DLP->getDataLayout() : 0;
92 DominatorTreeWrapperPass *DTWP =
93 getAnalysisIfAvailable<DominatorTreeWrapperPass>();
94 DT = DTWP ? &DTWP->getDomTree() : 0;
96 PredCache.reset(new PredIteratorCache());
100 /// RemoveFromReverseMap - This is a helper function that removes Val from
101 /// 'Inst's set in ReverseMap. If the set becomes empty, remove Inst's entry.
102 template <typename KeyTy>
103 static void RemoveFromReverseMap(DenseMap<Instruction*,
104 SmallPtrSet<KeyTy, 4> > &ReverseMap,
105 Instruction *Inst, KeyTy Val) {
106 typename DenseMap<Instruction*, SmallPtrSet<KeyTy, 4> >::iterator
107 InstIt = ReverseMap.find(Inst);
108 assert(InstIt != ReverseMap.end() && "Reverse map out of sync?");
109 bool Found = InstIt->second.erase(Val);
110 assert(Found && "Invalid reverse map!"); (void)Found;
111 if (InstIt->second.empty())
112 ReverseMap.erase(InstIt);
115 /// GetLocation - If the given instruction references a specific memory
116 /// location, fill in Loc with the details, otherwise set Loc.Ptr to null.
117 /// Return a ModRefInfo value describing the general behavior of the
120 AliasAnalysis::ModRefResult GetLocation(const Instruction *Inst,
121 AliasAnalysis::Location &Loc,
123 if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
124 if (LI->isUnordered()) {
125 Loc = AA->getLocation(LI);
126 return AliasAnalysis::Ref;
128 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;
141 if (SI->getOrdering() == Monotonic) {
142 Loc = AA->getLocation(SI);
143 return AliasAnalysis::ModRef;
145 Loc = AliasAnalysis::Location();
146 return AliasAnalysis::ModRef;
149 if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
150 Loc = AA->getLocation(V);
151 return AliasAnalysis::ModRef;
154 if (const CallInst *CI = isFreeCall(Inst, AA->getTargetLibraryInfo())) {
155 // calls to free() deallocate the entire structure
156 Loc = AliasAnalysis::Location(CI->getArgOperand(0));
157 return AliasAnalysis::Mod;
160 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst))
161 switch (II->getIntrinsicID()) {
162 case Intrinsic::lifetime_start:
163 case Intrinsic::lifetime_end:
164 case Intrinsic::invariant_start:
165 Loc = AliasAnalysis::Location(II->getArgOperand(1),
166 cast<ConstantInt>(II->getArgOperand(0))
168 II->getMetadata(LLVMContext::MD_tbaa));
169 // These intrinsics don't really modify the memory, but returning Mod
170 // will allow them to be handled conservatively.
171 return AliasAnalysis::Mod;
172 case Intrinsic::invariant_end:
173 Loc = AliasAnalysis::Location(II->getArgOperand(2),
174 cast<ConstantInt>(II->getArgOperand(1))
176 II->getMetadata(LLVMContext::MD_tbaa));
177 // These intrinsics don't really modify the memory, but returning Mod
178 // will allow them to be handled conservatively.
179 return AliasAnalysis::Mod;
184 // Otherwise, just do the coarse-grained thing that always works.
185 if (Inst->mayWriteToMemory())
186 return AliasAnalysis::ModRef;
187 if (Inst->mayReadFromMemory())
188 return AliasAnalysis::Ref;
189 return AliasAnalysis::NoModRef;
192 /// getCallSiteDependencyFrom - Private helper for finding the local
193 /// dependencies of a call site.
194 MemDepResult MemoryDependenceAnalysis::
195 getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
196 BasicBlock::iterator ScanIt, BasicBlock *BB) {
197 unsigned Limit = BlockScanLimit;
199 // Walk backwards through the block, looking for dependencies
200 while (ScanIt != BB->begin()) {
201 // Limit the amount of scanning we do so we don't end up with quadratic
202 // running time on extreme testcases.
205 return MemDepResult::getUnknown();
207 Instruction *Inst = --ScanIt;
209 // If this inst is a memory op, get the pointer it accessed
210 AliasAnalysis::Location Loc;
211 AliasAnalysis::ModRefResult MR = GetLocation(Inst, Loc, AA);
213 // A simple instruction.
214 if (AA->getModRefInfo(CS, Loc) != AliasAnalysis::NoModRef)
215 return MemDepResult::getClobber(Inst);
219 if (CallSite InstCS = cast<Value>(Inst)) {
220 // Debug intrinsics don't cause dependences.
221 if (isa<DbgInfoIntrinsic>(Inst)) continue;
222 // If these two calls do not interfere, look past it.
223 switch (AA->getModRefInfo(CS, InstCS)) {
224 case AliasAnalysis::NoModRef:
225 // If the two calls are the same, return InstCS as a Def, so that
226 // CS can be found redundant and eliminated.
227 if (isReadOnlyCall && !(MR & AliasAnalysis::Mod) &&
228 CS.getInstruction()->isIdenticalToWhenDefined(Inst))
229 return MemDepResult::getDef(Inst);
231 // Otherwise if the two calls don't interact (e.g. InstCS is readnone)
235 return MemDepResult::getClobber(Inst);
239 // If we could not obtain a pointer for the instruction and the instruction
240 // touches memory then assume that this is a dependency.
241 if (MR != AliasAnalysis::NoModRef)
242 return MemDepResult::getClobber(Inst);
245 // No dependence found. If this is the entry block of the function, it is
246 // unknown, otherwise it is non-local.
247 if (BB != &BB->getParent()->getEntryBlock())
248 return MemDepResult::getNonLocal();
249 return MemDepResult::getNonFuncLocal();
252 /// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
253 /// would fully overlap MemLoc if done as a wider legal integer load.
255 /// MemLocBase, MemLocOffset are lazily computed here the first time the
256 /// base/offs of memloc is needed.
258 isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc,
259 const Value *&MemLocBase,
262 const DataLayout *DL) {
263 // If we have no target data, we can't do this.
264 if (DL == 0) return false;
266 // If we haven't already computed the base/offset of MemLoc, do so now.
268 MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, DL);
270 unsigned Size = MemoryDependenceAnalysis::
271 getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size,
276 /// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that
277 /// looks at a memory location for a load (specified by MemLocBase, Offs,
278 /// and Size) and compares it against a load. If the specified load could
279 /// be safely widened to a larger integer load that is 1) still efficient,
280 /// 2) safe for the target, and 3) would provide the specified memory
281 /// location value, then this function returns the size in bytes of the
282 /// load width to use. If not, this returns zero.
283 unsigned MemoryDependenceAnalysis::
284 getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
285 unsigned MemLocSize, const LoadInst *LI,
286 const DataLayout &DL) {
287 // We can only extend simple integer loads.
288 if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0;
290 // Load widening is hostile to ThreadSanitizer: it may cause false positives
291 // or make the reports more cryptic (access sizes are wrong).
292 if (LI->getParent()->getParent()->getAttributes().
293 hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeThread))
296 // Get the base of this load.
298 const Value *LIBase =
299 GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, &DL);
301 // If the two pointers are not based on the same pointer, we can't tell that
303 if (LIBase != MemLocBase) return 0;
305 // Okay, the two values are based on the same pointer, but returned as
306 // no-alias. This happens when we have things like two byte loads at "P+1"
307 // and "P+3". Check to see if increasing the size of the "LI" load up to its
308 // alignment (or the largest native integer type) will allow us to load all
309 // the bits required by MemLoc.
311 // If MemLoc is before LI, then no widening of LI will help us out.
312 if (MemLocOffs < LIOffs) return 0;
314 // Get the alignment of the load in bytes. We assume that it is safe to load
315 // any legal integer up to this size without a problem. For example, if we're
316 // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can
317 // widen it up to an i32 load. If it is known 2-byte aligned, we can widen it
319 unsigned LoadAlign = LI->getAlignment();
321 int64_t MemLocEnd = MemLocOffs+MemLocSize;
323 // If no amount of rounding up will let MemLoc fit into LI, then bail out.
324 if (LIOffs+LoadAlign < MemLocEnd) return 0;
326 // This is the size of the load to try. Start with the next larger power of
328 unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U;
329 NewLoadByteSize = NextPowerOf2(NewLoadByteSize);
332 // If this load size is bigger than our known alignment or would not fit
333 // into a native integer register, then we fail.
334 if (NewLoadByteSize > LoadAlign ||
335 !DL.fitsInLegalInteger(NewLoadByteSize*8))
338 if (LIOffs+NewLoadByteSize > MemLocEnd &&
339 LI->getParent()->getParent()->getAttributes().
340 hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeAddress))
341 // We will be reading past the location accessed by the original program.
342 // While this is safe in a regular build, Address Safety analysis tools
343 // may start reporting false warnings. So, don't do widening.
346 // If a load of this width would include all of MemLoc, then we succeed.
347 if (LIOffs+NewLoadByteSize >= MemLocEnd)
348 return NewLoadByteSize;
350 NewLoadByteSize <<= 1;
354 /// getPointerDependencyFrom - Return the instruction on which a memory
355 /// location depends. If isLoad is true, this routine ignores may-aliases with
356 /// read-only operations. If isLoad is false, this routine ignores may-aliases
357 /// with reads from read-only locations. If possible, pass the query
358 /// instruction as well; this function may take advantage of the metadata
359 /// annotated to the query instruction to refine the result.
360 MemDepResult MemoryDependenceAnalysis::
361 getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
362 BasicBlock::iterator ScanIt, BasicBlock *BB,
363 Instruction *QueryInst) {
365 const Value *MemLocBase = 0;
366 int64_t MemLocOffset = 0;
367 unsigned Limit = BlockScanLimit;
368 bool isInvariantLoad = false;
369 if (isLoad && QueryInst) {
370 LoadInst *LI = dyn_cast<LoadInst>(QueryInst);
371 if (LI && LI->getMetadata(LLVMContext::MD_invariant_load) != 0)
372 isInvariantLoad = true;
375 // Walk backwards through the basic block, looking for dependencies.
376 while (ScanIt != BB->begin()) {
377 Instruction *Inst = --ScanIt;
379 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst))
380 // Debug intrinsics don't (and can't) cause dependencies.
381 if (isa<DbgInfoIntrinsic>(II)) continue;
383 // Limit the amount of scanning we do so we don't end up with quadratic
384 // running time on extreme testcases.
387 return MemDepResult::getUnknown();
389 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
390 // If we reach a lifetime begin or end marker, then the query ends here
391 // because the value is undefined.
392 if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
393 // FIXME: This only considers queries directly on the invariant-tagged
394 // pointer, not on query pointers that are indexed off of them. It'd
395 // be nice to handle that at some point (the right approach is to use
396 // GetPointerBaseWithConstantOffset).
397 if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)),
399 return MemDepResult::getDef(II);
404 // Values depend on loads if the pointers are must aliased. This means that
405 // a load depends on another must aliased load from the same value.
406 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
407 // Atomic loads have complications involved.
408 // FIXME: This is overly conservative.
409 if (!LI->isUnordered())
410 return MemDepResult::getClobber(LI);
412 AliasAnalysis::Location LoadLoc = AA->getLocation(LI);
414 // If we found a pointer, check if it could be the same as our pointer.
415 AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc);
418 if (R == AliasAnalysis::NoAlias) {
419 // If this is an over-aligned integer load (for example,
420 // "load i8* %P, align 4") see if it would obviously overlap with the
421 // queried location if widened to a larger load (e.g. if the queried
422 // location is 1 byte at P+1). If so, return it as a load/load
423 // clobber result, allowing the client to decide to widen the load if
425 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
426 if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() &&
427 isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase,
428 MemLocOffset, LI, DL))
429 return MemDepResult::getClobber(Inst);
434 // Must aliased loads are defs of each other.
435 if (R == AliasAnalysis::MustAlias)
436 return MemDepResult::getDef(Inst);
438 #if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads
439 // in terms of clobbering loads, but since it does this by looking
440 // at the clobbering load directly, it doesn't know about any
441 // phi translation that may have happened along the way.
443 // If we have a partial alias, then return this as a clobber for the
445 if (R == AliasAnalysis::PartialAlias)
446 return MemDepResult::getClobber(Inst);
449 // Random may-alias loads don't depend on each other without a
454 // Stores don't depend on other no-aliased accesses.
455 if (R == AliasAnalysis::NoAlias)
458 // Stores don't alias loads from read-only memory.
459 if (AA->pointsToConstantMemory(LoadLoc))
462 // Stores depend on may/must aliased loads.
463 return MemDepResult::getDef(Inst);
466 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
467 // Atomic stores have complications involved.
468 // FIXME: This is overly conservative.
469 if (!SI->isUnordered())
470 return MemDepResult::getClobber(SI);
472 // If alias analysis can tell that this store is guaranteed to not modify
473 // the query pointer, ignore it. Use getModRefInfo to handle cases where
474 // the query pointer points to constant memory etc.
475 if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef)
478 // Ok, this store might clobber the query pointer. Check to see if it is
479 // a must alias: in this case, we want to return this as a def.
480 AliasAnalysis::Location StoreLoc = AA->getLocation(SI);
482 // If we found a pointer, check if it could be the same as our pointer.
483 AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc);
485 if (R == AliasAnalysis::NoAlias)
487 if (R == AliasAnalysis::MustAlias)
488 return MemDepResult::getDef(Inst);
491 return MemDepResult::getClobber(Inst);
494 // If this is an allocation, and if we know that the accessed pointer is to
495 // the allocation, return Def. This means that there is no dependence and
496 // the access can be optimized based on that. For example, a load could
498 // Note: Only determine this to be a malloc if Inst is the malloc call, not
499 // a subsequent bitcast of the malloc call result. There can be stores to
500 // the malloced memory between the malloc call and its bitcast uses, and we
501 // need to continue scanning until the malloc call.
502 const TargetLibraryInfo *TLI = AA->getTargetLibraryInfo();
503 if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, TLI)) {
504 const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, DL);
506 if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
507 return MemDepResult::getDef(Inst);
508 // Be conservative if the accessed pointer may alias the allocation.
509 if (AA->alias(Inst, AccessPtr) != AliasAnalysis::NoAlias)
510 return MemDepResult::getClobber(Inst);
511 // If the allocation is not aliased and does not read memory (like
512 // strdup), it is safe to ignore.
513 if (isa<AllocaInst>(Inst) ||
514 isMallocLikeFn(Inst, TLI) || isCallocLikeFn(Inst, TLI))
518 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
519 AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc);
520 // If necessary, perform additional analysis.
521 if (MR == AliasAnalysis::ModRef)
522 MR = AA->callCapturesBefore(Inst, MemLoc, DT);
524 case AliasAnalysis::NoModRef:
525 // If the call has no effect on the queried pointer, just ignore it.
527 case AliasAnalysis::Mod:
528 return MemDepResult::getClobber(Inst);
529 case AliasAnalysis::Ref:
530 // If the call is known to never store to the pointer, and if this is a
531 // load query, we can safely ignore it (scan past it).
535 // Otherwise, there is a potential dependence. Return a clobber.
536 return MemDepResult::getClobber(Inst);
540 // No dependence found. If this is the entry block of the function, it is
541 // unknown, otherwise it is non-local.
542 if (BB != &BB->getParent()->getEntryBlock())
543 return MemDepResult::getNonLocal();
544 return MemDepResult::getNonFuncLocal();
547 /// getDependency - Return the instruction on which a memory operation
549 MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
550 Instruction *ScanPos = QueryInst;
552 // Check for a cached result
553 MemDepResult &LocalCache = LocalDeps[QueryInst];
555 // If the cached entry is non-dirty, just return it. Note that this depends
556 // on MemDepResult's default constructing to 'dirty'.
557 if (!LocalCache.isDirty())
560 // Otherwise, if we have a dirty entry, we know we can start the scan at that
561 // instruction, which may save us some work.
562 if (Instruction *Inst = LocalCache.getInst()) {
565 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst);
568 BasicBlock *QueryParent = QueryInst->getParent();
571 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
572 // No dependence found. If this is the entry block of the function, it is
573 // unknown, otherwise it is non-local.
574 if (QueryParent != &QueryParent->getParent()->getEntryBlock())
575 LocalCache = MemDepResult::getNonLocal();
577 LocalCache = MemDepResult::getNonFuncLocal();
579 AliasAnalysis::Location MemLoc;
580 AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
582 // If we can do a pointer scan, make it happen.
583 bool isLoad = !(MR & AliasAnalysis::Mod);
584 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst))
585 isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start;
587 LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos,
588 QueryParent, QueryInst);
589 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
590 CallSite QueryCS(QueryInst);
591 bool isReadOnly = AA->onlyReadsMemory(QueryCS);
592 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos,
595 // Non-memory instruction.
596 LocalCache = MemDepResult::getUnknown();
599 // Remember the result!
600 if (Instruction *I = LocalCache.getInst())
601 ReverseLocalDeps[I].insert(QueryInst);
607 /// AssertSorted - This method is used when -debug is specified to verify that
608 /// cache arrays are properly kept sorted.
609 static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
611 if (Count == -1) Count = Cache.size();
612 if (Count == 0) return;
614 for (unsigned i = 1; i != unsigned(Count); ++i)
615 assert(!(Cache[i] < Cache[i-1]) && "Cache isn't sorted!");
619 /// getNonLocalCallDependency - Perform a full dependency query for the
620 /// specified call, returning the set of blocks that the value is
621 /// potentially live across. The returned set of results will include a
622 /// "NonLocal" result for all blocks where the value is live across.
624 /// This method assumes the instruction returns a "NonLocal" dependency
625 /// within its own block.
627 /// This returns a reference to an internal data structure that may be
628 /// invalidated on the next non-local query or when an instruction is
629 /// removed. Clients must copy this data if they want it around longer than
631 const MemoryDependenceAnalysis::NonLocalDepInfo &
632 MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
633 assert(getDependency(QueryCS.getInstruction()).isNonLocal() &&
634 "getNonLocalCallDependency should only be used on calls with non-local deps!");
635 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()];
636 NonLocalDepInfo &Cache = CacheP.first;
638 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In
639 /// the cached case, this can happen due to instructions being deleted etc. In
640 /// the uncached case, this starts out as the set of predecessors we care
642 SmallVector<BasicBlock*, 32> DirtyBlocks;
644 if (!Cache.empty()) {
645 // Okay, we have a cache entry. If we know it is not dirty, just return it
646 // with no computation.
647 if (!CacheP.second) {
652 // If we already have a partially computed set of results, scan them to
653 // determine what is dirty, seeding our initial DirtyBlocks worklist.
654 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end();
656 if (I->getResult().isDirty())
657 DirtyBlocks.push_back(I->getBB());
659 // Sort the cache so that we can do fast binary search lookups below.
660 std::sort(Cache.begin(), Cache.end());
662 ++NumCacheDirtyNonLocal;
663 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: "
664 // << Cache.size() << " cached: " << *QueryInst;
666 // Seed DirtyBlocks with each of the preds of QueryInst's block.
667 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent();
668 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI)
669 DirtyBlocks.push_back(*PI);
670 ++NumUncacheNonLocal;
673 // isReadonlyCall - If this is a read-only call, we can be more aggressive.
674 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS);
676 SmallPtrSet<BasicBlock*, 64> Visited;
678 unsigned NumSortedEntries = Cache.size();
679 DEBUG(AssertSorted(Cache));
681 // Iterate while we still have blocks to update.
682 while (!DirtyBlocks.empty()) {
683 BasicBlock *DirtyBB = DirtyBlocks.back();
684 DirtyBlocks.pop_back();
686 // Already processed this block?
687 if (!Visited.insert(DirtyBB))
690 // Do a binary search to see if we already have an entry for this block in
691 // the cache set. If so, find it.
692 DEBUG(AssertSorted(Cache, NumSortedEntries));
693 NonLocalDepInfo::iterator Entry =
694 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries,
695 NonLocalDepEntry(DirtyBB));
696 if (Entry != Cache.begin() && std::prev(Entry)->getBB() == DirtyBB)
699 NonLocalDepEntry *ExistingResult = 0;
700 if (Entry != Cache.begin()+NumSortedEntries &&
701 Entry->getBB() == DirtyBB) {
702 // If we already have an entry, and if it isn't already dirty, the block
704 if (!Entry->getResult().isDirty())
707 // Otherwise, remember this slot so we can update the value.
708 ExistingResult = &*Entry;
711 // If the dirty entry has a pointer, start scanning from it so we don't have
712 // to rescan the entire block.
713 BasicBlock::iterator ScanPos = DirtyBB->end();
714 if (ExistingResult) {
715 if (Instruction *Inst = ExistingResult->getResult().getInst()) {
717 // We're removing QueryInst's use of Inst.
718 RemoveFromReverseMap(ReverseNonLocalDeps, Inst,
719 QueryCS.getInstruction());
723 // Find out if this block has a local dependency for QueryInst.
726 if (ScanPos != DirtyBB->begin()) {
727 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
728 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
729 // No dependence found. If this is the entry block of the function, it is
730 // a clobber, otherwise it is unknown.
731 Dep = MemDepResult::getNonLocal();
733 Dep = MemDepResult::getNonFuncLocal();
736 // If we had a dirty entry for the block, update it. Otherwise, just add
739 ExistingResult->setResult(Dep);
741 Cache.push_back(NonLocalDepEntry(DirtyBB, Dep));
743 // If the block has a dependency (i.e. it isn't completely transparent to
744 // the value), remember the association!
745 if (!Dep.isNonLocal()) {
746 // Keep the ReverseNonLocalDeps map up to date so we can efficiently
747 // update this when we remove instructions.
748 if (Instruction *Inst = Dep.getInst())
749 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction());
752 // If the block *is* completely transparent to the load, we need to check
753 // the predecessors of this block. Add them to our worklist.
754 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI)
755 DirtyBlocks.push_back(*PI);
762 /// getNonLocalPointerDependency - Perform a full dependency query for an
763 /// access to the specified (non-volatile) memory location, returning the
764 /// set of instructions that either define or clobber the value.
766 /// This method assumes the pointer has a "NonLocal" dependency within its
769 void MemoryDependenceAnalysis::
770 getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad,
772 SmallVectorImpl<NonLocalDepResult> &Result) {
773 assert(Loc.Ptr->getType()->isPointerTy() &&
774 "Can't get pointer deps of a non-pointer!");
777 PHITransAddr Address(const_cast<Value *>(Loc.Ptr), DL);
779 // This is the set of blocks we've inspected, and the pointer we consider in
780 // each block. Because of critical edges, we currently bail out if querying
781 // a block with multiple different pointers. This can happen during PHI
783 DenseMap<BasicBlock*, Value*> Visited;
784 if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB,
785 Result, Visited, true))
788 Result.push_back(NonLocalDepResult(FromBB,
789 MemDepResult::getUnknown(),
790 const_cast<Value *>(Loc.Ptr)));
793 /// GetNonLocalInfoForBlock - Compute the memdep value for BB with
794 /// Pointer/PointeeSize using either cached information in Cache or by doing a
795 /// lookup (which may use dirty cache info if available). If we do a lookup,
796 /// add the result to the cache.
797 MemDepResult MemoryDependenceAnalysis::
798 GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
799 bool isLoad, BasicBlock *BB,
800 NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
802 // Do a binary search to see if we already have an entry for this block in
803 // the cache set. If so, find it.
804 NonLocalDepInfo::iterator Entry =
805 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries,
806 NonLocalDepEntry(BB));
807 if (Entry != Cache->begin() && (Entry-1)->getBB() == BB)
810 NonLocalDepEntry *ExistingResult = 0;
811 if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB)
812 ExistingResult = &*Entry;
814 // If we have a cached entry, and it is non-dirty, use it as the value for
816 if (ExistingResult && !ExistingResult->getResult().isDirty()) {
817 ++NumCacheNonLocalPtr;
818 return ExistingResult->getResult();
821 // Otherwise, we have to scan for the value. If we have a dirty cache
822 // entry, start scanning from its position, otherwise we scan from the end
824 BasicBlock::iterator ScanPos = BB->end();
825 if (ExistingResult && ExistingResult->getResult().getInst()) {
826 assert(ExistingResult->getResult().getInst()->getParent() == BB &&
827 "Instruction invalidated?");
828 ++NumCacheDirtyNonLocalPtr;
829 ScanPos = ExistingResult->getResult().getInst();
831 // Eliminating the dirty entry from 'Cache', so update the reverse info.
832 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
833 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey);
835 ++NumUncacheNonLocalPtr;
838 // Scan the block for the dependency.
839 MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB);
841 // If we had a dirty entry for the block, update it. Otherwise, just add
844 ExistingResult->setResult(Dep);
846 Cache->push_back(NonLocalDepEntry(BB, Dep));
848 // If the block has a dependency (i.e. it isn't completely transparent to
849 // the value), remember the reverse association because we just added it
851 if (!Dep.isDef() && !Dep.isClobber())
854 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
855 // update MemDep when we remove instructions.
856 Instruction *Inst = Dep.getInst();
857 assert(Inst && "Didn't depend on anything?");
858 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
859 ReverseNonLocalPtrDeps[Inst].insert(CacheKey);
863 /// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain
864 /// number of elements in the array that are already properly ordered. This is
865 /// optimized for the case when only a few entries are added.
867 SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
868 unsigned NumSortedEntries) {
869 switch (Cache.size() - NumSortedEntries) {
871 // done, no new entries.
874 // Two new entries, insert the last one into place.
875 NonLocalDepEntry Val = Cache.back();
877 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
878 std::upper_bound(Cache.begin(), Cache.end()-1, Val);
879 Cache.insert(Entry, Val);
883 // One new entry, Just insert the new value at the appropriate position.
884 if (Cache.size() != 1) {
885 NonLocalDepEntry Val = Cache.back();
887 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
888 std::upper_bound(Cache.begin(), Cache.end(), Val);
889 Cache.insert(Entry, Val);
893 // Added many values, do a full scale sort.
894 std::sort(Cache.begin(), Cache.end());
899 /// getNonLocalPointerDepFromBB - Perform a dependency query based on
900 /// pointer/pointeesize starting at the end of StartBB. Add any clobber/def
901 /// results to the results vector and keep track of which blocks are visited in
904 /// This has special behavior for the first block queries (when SkipFirstBlock
905 /// is true). In this special case, it ignores the contents of the specified
906 /// block and starts returning dependence info for its predecessors.
908 /// This function returns false on success, or true to indicate that it could
909 /// not compute dependence information for some reason. This should be treated
910 /// as a clobber dependence on the first instruction in the predecessor block.
911 bool MemoryDependenceAnalysis::
912 getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
913 const AliasAnalysis::Location &Loc,
914 bool isLoad, BasicBlock *StartBB,
915 SmallVectorImpl<NonLocalDepResult> &Result,
916 DenseMap<BasicBlock*, Value*> &Visited,
917 bool SkipFirstBlock) {
918 // Look up the cached info for Pointer.
919 ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad);
921 // Set up a temporary NLPI value. If the map doesn't yet have an entry for
922 // CacheKey, this value will be inserted as the associated value. Otherwise,
923 // it'll be ignored, and we'll have to check to see if the cached size and
924 // tbaa tag are consistent with the current query.
925 NonLocalPointerInfo InitialNLPI;
926 InitialNLPI.Size = Loc.Size;
927 InitialNLPI.TBAATag = Loc.TBAATag;
929 // Get the NLPI for CacheKey, inserting one into the map if it doesn't
931 std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair =
932 NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI));
933 NonLocalPointerInfo *CacheInfo = &Pair.first->second;
935 // If we already have a cache entry for this CacheKey, we may need to do some
936 // work to reconcile the cache entry and the current query.
938 if (CacheInfo->Size < Loc.Size) {
939 // The query's Size is greater than the cached one. Throw out the
940 // cached data and proceed with the query at the greater size.
941 CacheInfo->Pair = BBSkipFirstBlockPair();
942 CacheInfo->Size = Loc.Size;
943 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
944 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
945 if (Instruction *Inst = DI->getResult().getInst())
946 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
947 CacheInfo->NonLocalDeps.clear();
948 } else if (CacheInfo->Size > Loc.Size) {
949 // This query's Size is less than the cached one. Conservatively restart
950 // the query using the greater size.
951 return getNonLocalPointerDepFromBB(Pointer,
952 Loc.getWithNewSize(CacheInfo->Size),
953 isLoad, StartBB, Result, Visited,
957 // If the query's TBAATag is inconsistent with the cached one,
958 // conservatively throw out the cached data and restart the query with
960 if (CacheInfo->TBAATag != Loc.TBAATag) {
961 if (CacheInfo->TBAATag) {
962 CacheInfo->Pair = BBSkipFirstBlockPair();
963 CacheInfo->TBAATag = 0;
964 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
965 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
966 if (Instruction *Inst = DI->getResult().getInst())
967 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
968 CacheInfo->NonLocalDeps.clear();
971 return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutTBAATag(),
972 isLoad, StartBB, Result, Visited,
977 NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps;
979 // If we have valid cached information for exactly the block we are
980 // investigating, just return it with no recomputation.
981 if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
982 // We have a fully cached result for this query then we can just return the
983 // cached results and populate the visited set. However, we have to verify
984 // that we don't already have conflicting results for these blocks. Check
985 // to ensure that if a block in the results set is in the visited set that
986 // it was for the same pointer query.
987 if (!Visited.empty()) {
988 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
990 DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->getBB());
991 if (VI == Visited.end() || VI->second == Pointer.getAddr())
994 // We have a pointer mismatch in a block. Just return clobber, saying
995 // that something was clobbered in this result. We could also do a
996 // non-fully cached query, but there is little point in doing this.
1001 Value *Addr = Pointer.getAddr();
1002 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
1004 Visited.insert(std::make_pair(I->getBB(), Addr));
1005 if (I->getResult().isNonLocal()) {
1010 Result.push_back(NonLocalDepResult(I->getBB(),
1011 MemDepResult::getUnknown(),
1013 } else if (DT->isReachableFromEntry(I->getBB())) {
1014 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr));
1017 ++NumCacheCompleteNonLocalPtr;
1021 // Otherwise, either this is a new block, a block with an invalid cache
1022 // pointer or one that we're about to invalidate by putting more info into it
1023 // than its valid cache info. If empty, the result will be valid cache info,
1024 // otherwise it isn't.
1026 CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
1028 CacheInfo->Pair = BBSkipFirstBlockPair();
1030 SmallVector<BasicBlock*, 32> Worklist;
1031 Worklist.push_back(StartBB);
1033 // PredList used inside loop.
1034 SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList;
1036 // Keep track of the entries that we know are sorted. Previously cached
1037 // entries will all be sorted. The entries we add we only sort on demand (we
1038 // don't insert every element into its sorted position). We know that we
1039 // won't get any reuse from currently inserted values, because we don't
1040 // revisit blocks after we insert info for them.
1041 unsigned NumSortedEntries = Cache->size();
1042 DEBUG(AssertSorted(*Cache));
1044 while (!Worklist.empty()) {
1045 BasicBlock *BB = Worklist.pop_back_val();
1047 // Skip the first block if we have it.
1048 if (!SkipFirstBlock) {
1049 // Analyze the dependency of *Pointer in FromBB. See if we already have
1051 assert(Visited.count(BB) && "Should check 'visited' before adding to WL");
1053 // Get the dependency info for Pointer in BB. If we have cached
1054 // information, we will use it, otherwise we compute it.
1055 DEBUG(AssertSorted(*Cache, NumSortedEntries));
1056 MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache,
1059 // If we got a Def or Clobber, add this to the list of results.
1060 if (!Dep.isNonLocal()) {
1062 Result.push_back(NonLocalDepResult(BB,
1063 MemDepResult::getUnknown(),
1064 Pointer.getAddr()));
1066 } else if (DT->isReachableFromEntry(BB)) {
1067 Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr()));
1073 // If 'Pointer' is an instruction defined in this block, then we need to do
1074 // phi translation to change it into a value live in the predecessor block.
1075 // If not, we just add the predecessors to the worklist and scan them with
1076 // the same Pointer.
1077 if (!Pointer.NeedsPHITranslationFromBlock(BB)) {
1078 SkipFirstBlock = false;
1079 SmallVector<BasicBlock*, 16> NewBlocks;
1080 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1081 // Verify that we haven't looked at this block yet.
1082 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1083 InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr()));
1084 if (InsertRes.second) {
1085 // First time we've looked at *PI.
1086 NewBlocks.push_back(*PI);
1090 // If we have seen this block before, but it was with a different
1091 // pointer then we have a phi translation failure and we have to treat
1092 // this as a clobber.
1093 if (InsertRes.first->second != Pointer.getAddr()) {
1094 // Make sure to clean up the Visited map before continuing on to
1095 // PredTranslationFailure.
1096 for (unsigned i = 0; i < NewBlocks.size(); i++)
1097 Visited.erase(NewBlocks[i]);
1098 goto PredTranslationFailure;
1101 Worklist.append(NewBlocks.begin(), NewBlocks.end());
1105 // We do need to do phi translation, if we know ahead of time we can't phi
1106 // translate this value, don't even try.
1107 if (!Pointer.IsPotentiallyPHITranslatable())
1108 goto PredTranslationFailure;
1110 // We may have added values to the cache list before this PHI translation.
1111 // If so, we haven't done anything to ensure that the cache remains sorted.
1112 // Sort it now (if needed) so that recursive invocations of
1113 // getNonLocalPointerDepFromBB and other routines that could reuse the cache
1114 // value will only see properly sorted cache arrays.
1115 if (Cache && NumSortedEntries != Cache->size()) {
1116 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1117 NumSortedEntries = Cache->size();
1122 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1123 BasicBlock *Pred = *PI;
1124 PredList.push_back(std::make_pair(Pred, Pointer));
1126 // Get the PHI translated pointer in this predecessor. This can fail if
1127 // not translatable, in which case the getAddr() returns null.
1128 PHITransAddr &PredPointer = PredList.back().second;
1129 PredPointer.PHITranslateValue(BB, Pred, 0);
1131 Value *PredPtrVal = PredPointer.getAddr();
1133 // Check to see if we have already visited this pred block with another
1134 // pointer. If so, we can't do this lookup. This failure can occur
1135 // with PHI translation when a critical edge exists and the PHI node in
1136 // the successor translates to a pointer value different than the
1137 // pointer the block was first analyzed with.
1138 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1139 InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal));
1141 if (!InsertRes.second) {
1142 // We found the pred; take it off the list of preds to visit.
1143 PredList.pop_back();
1145 // If the predecessor was visited with PredPtr, then we already did
1146 // the analysis and can ignore it.
1147 if (InsertRes.first->second == PredPtrVal)
1150 // Otherwise, the block was previously analyzed with a different
1151 // pointer. We can't represent the result of this case, so we just
1152 // treat this as a phi translation failure.
1154 // Make sure to clean up the Visited map before continuing on to
1155 // PredTranslationFailure.
1156 for (unsigned i = 0, n = PredList.size(); i < n; ++i)
1157 Visited.erase(PredList[i].first);
1159 goto PredTranslationFailure;
1163 // Actually process results here; this need to be a separate loop to avoid
1164 // calling getNonLocalPointerDepFromBB for blocks we don't want to return
1165 // any results for. (getNonLocalPointerDepFromBB will modify our
1166 // datastructures in ways the code after the PredTranslationFailure label
1168 for (unsigned i = 0, n = PredList.size(); i < n; ++i) {
1169 BasicBlock *Pred = PredList[i].first;
1170 PHITransAddr &PredPointer = PredList[i].second;
1171 Value *PredPtrVal = PredPointer.getAddr();
1173 bool CanTranslate = true;
1174 // If PHI translation was unable to find an available pointer in this
1175 // predecessor, then we have to assume that the pointer is clobbered in
1176 // that predecessor. We can still do PRE of the load, which would insert
1177 // a computation of the pointer in this predecessor.
1178 if (PredPtrVal == 0)
1179 CanTranslate = false;
1181 // FIXME: it is entirely possible that PHI translating will end up with
1182 // the same value. Consider PHI translating something like:
1183 // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need*
1184 // to recurse here, pedantically speaking.
1186 // If getNonLocalPointerDepFromBB fails here, that means the cached
1187 // result conflicted with the Visited list; we have to conservatively
1188 // assume it is unknown, but this also does not block PRE of the load.
1189 if (!CanTranslate ||
1190 getNonLocalPointerDepFromBB(PredPointer,
1191 Loc.getWithNewPtr(PredPtrVal),
1194 // Add the entry to the Result list.
1195 NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal);
1196 Result.push_back(Entry);
1198 // Since we had a phi translation failure, the cache for CacheKey won't
1199 // include all of the entries that we need to immediately satisfy future
1200 // queries. Mark this in NonLocalPointerDeps by setting the
1201 // BBSkipFirstBlockPair pointer to null. This requires reuse of the
1202 // cached value to do more work but not miss the phi trans failure.
1203 NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey];
1204 NLPI.Pair = BBSkipFirstBlockPair();
1209 // Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
1210 CacheInfo = &NonLocalPointerDeps[CacheKey];
1211 Cache = &CacheInfo->NonLocalDeps;
1212 NumSortedEntries = Cache->size();
1214 // Since we did phi translation, the "Cache" set won't contain all of the
1215 // results for the query. This is ok (we can still use it to accelerate
1216 // specific block queries) but we can't do the fastpath "return all
1217 // results from the set" Clear out the indicator for this.
1218 CacheInfo->Pair = BBSkipFirstBlockPair();
1219 SkipFirstBlock = false;
1222 PredTranslationFailure:
1223 // The following code is "failure"; we can't produce a sane translation
1224 // for the given block. It assumes that we haven't modified any of
1225 // our datastructures while processing the current block.
1228 // Refresh the CacheInfo/Cache pointer if it got invalidated.
1229 CacheInfo = &NonLocalPointerDeps[CacheKey];
1230 Cache = &CacheInfo->NonLocalDeps;
1231 NumSortedEntries = Cache->size();
1234 // Since we failed 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();
1240 // If *nothing* works, mark the pointer as unknown.
1242 // If this is the magic first block, return this as a clobber of the whole
1243 // incoming value. Since we can't phi translate to one of the predecessors,
1244 // we have to bail out.
1248 for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) {
1249 assert(I != Cache->rend() && "Didn't find current block??");
1250 if (I->getBB() != BB)
1253 assert(I->getResult().isNonLocal() &&
1254 "Should only be here with transparent block");
1255 I->setResult(MemDepResult::getUnknown());
1256 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(),
1257 Pointer.getAddr()));
1262 // Okay, we're done now. If we added new values to the cache, re-sort it.
1263 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1264 DEBUG(AssertSorted(*Cache));
1268 /// RemoveCachedNonLocalPointerDependencies - If P exists in
1269 /// CachedNonLocalPointerInfo, remove it.
1270 void MemoryDependenceAnalysis::
1271 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) {
1272 CachedNonLocalPointerInfo::iterator It =
1273 NonLocalPointerDeps.find(P);
1274 if (It == NonLocalPointerDeps.end()) return;
1276 // Remove all of the entries in the BB->val map. This involves removing
1277 // instructions from the reverse map.
1278 NonLocalDepInfo &PInfo = It->second.NonLocalDeps;
1280 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
1281 Instruction *Target = PInfo[i].getResult().getInst();
1282 if (Target == 0) continue; // Ignore non-local dep results.
1283 assert(Target->getParent() == PInfo[i].getBB());
1285 // Eliminating the dirty entry from 'Cache', so update the reverse info.
1286 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P);
1289 // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo).
1290 NonLocalPointerDeps.erase(It);
1294 /// invalidateCachedPointerInfo - This method is used to invalidate cached
1295 /// information about the specified pointer, because it may be too
1296 /// conservative in memdep. This is an optional call that can be used when
1297 /// the client detects an equivalence between the pointer and some other
1298 /// value and replaces the other value with ptr. This can make Ptr available
1299 /// in more places that cached info does not necessarily keep.
1300 void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) {
1301 // If Ptr isn't really a pointer, just ignore it.
1302 if (!Ptr->getType()->isPointerTy()) return;
1303 // Flush store info for the pointer.
1304 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false));
1305 // Flush load info for the pointer.
1306 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true));
1309 /// invalidateCachedPredecessors - Clear the PredIteratorCache info.
1310 /// This needs to be done when the CFG changes, e.g., due to splitting
1312 void MemoryDependenceAnalysis::invalidateCachedPredecessors() {
1316 /// removeInstruction - Remove an instruction from the dependence analysis,
1317 /// updating the dependence of instructions that previously depended on it.
1318 /// This method attempts to keep the cache coherent using the reverse map.
1319 void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) {
1320 // Walk through the Non-local dependencies, removing this one as the value
1321 // for any cached queries.
1322 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst);
1323 if (NLDI != NonLocalDeps.end()) {
1324 NonLocalDepInfo &BlockMap = NLDI->second.first;
1325 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end();
1327 if (Instruction *Inst = DI->getResult().getInst())
1328 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst);
1329 NonLocalDeps.erase(NLDI);
1332 // If we have a cached local dependence query for this instruction, remove it.
1334 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst);
1335 if (LocalDepEntry != LocalDeps.end()) {
1336 // Remove us from DepInst's reverse set now that the local dep info is gone.
1337 if (Instruction *Inst = LocalDepEntry->second.getInst())
1338 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst);
1340 // Remove this local dependency info.
1341 LocalDeps.erase(LocalDepEntry);
1344 // If we have any cached pointer dependencies on this instruction, remove
1345 // them. If the instruction has non-pointer type, then it can't be a pointer
1348 // Remove it from both the load info and the store info. The instruction
1349 // can't be in either of these maps if it is non-pointer.
1350 if (RemInst->getType()->isPointerTy()) {
1351 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false));
1352 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true));
1355 // Loop over all of the things that depend on the instruction we're removing.
1357 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd;
1359 // If we find RemInst as a clobber or Def in any of the maps for other values,
1360 // we need to replace its entry with a dirty version of the instruction after
1361 // it. If RemInst is a terminator, we use a null dirty value.
1363 // Using a dirty version of the instruction after RemInst saves having to scan
1364 // the entire block to get to this point.
1365 MemDepResult NewDirtyVal;
1366 if (!RemInst->isTerminator())
1367 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst));
1369 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst);
1370 if (ReverseDepIt != ReverseLocalDeps.end()) {
1371 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second;
1372 // RemInst can't be the terminator if it has local stuff depending on it.
1373 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) &&
1374 "Nothing can locally depend on a terminator");
1376 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(),
1377 E = ReverseDeps.end(); I != E; ++I) {
1378 Instruction *InstDependingOnRemInst = *I;
1379 assert(InstDependingOnRemInst != RemInst &&
1380 "Already removed our local dep info");
1382 LocalDeps[InstDependingOnRemInst] = NewDirtyVal;
1384 // Make sure to remember that new things depend on NewDepInst.
1385 assert(NewDirtyVal.getInst() && "There is no way something else can have "
1386 "a local dep on this if it is a terminator!");
1387 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(),
1388 InstDependingOnRemInst));
1391 ReverseLocalDeps.erase(ReverseDepIt);
1393 // Add new reverse deps after scanning the set, to avoid invalidating the
1394 // 'ReverseDeps' reference.
1395 while (!ReverseDepsToAdd.empty()) {
1396 ReverseLocalDeps[ReverseDepsToAdd.back().first]
1397 .insert(ReverseDepsToAdd.back().second);
1398 ReverseDepsToAdd.pop_back();
1402 ReverseDepIt = ReverseNonLocalDeps.find(RemInst);
1403 if (ReverseDepIt != ReverseNonLocalDeps.end()) {
1404 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second;
1405 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end();
1407 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst");
1409 PerInstNLInfo &INLD = NonLocalDeps[*I];
1410 // The information is now dirty!
1413 for (NonLocalDepInfo::iterator DI = INLD.first.begin(),
1414 DE = INLD.first.end(); DI != DE; ++DI) {
1415 if (DI->getResult().getInst() != RemInst) continue;
1417 // Convert to a dirty entry for the subsequent instruction.
1418 DI->setResult(NewDirtyVal);
1420 if (Instruction *NextI = NewDirtyVal.getInst())
1421 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I));
1425 ReverseNonLocalDeps.erase(ReverseDepIt);
1427 // Add new reverse deps after scanning the set, to avoid invalidating 'Set'
1428 while (!ReverseDepsToAdd.empty()) {
1429 ReverseNonLocalDeps[ReverseDepsToAdd.back().first]
1430 .insert(ReverseDepsToAdd.back().second);
1431 ReverseDepsToAdd.pop_back();
1435 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a
1436 // value in the NonLocalPointerDeps info.
1437 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt =
1438 ReverseNonLocalPtrDeps.find(RemInst);
1439 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) {
1440 SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second;
1441 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd;
1443 for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(),
1444 E = Set.end(); I != E; ++I) {
1445 ValueIsLoadPair P = *I;
1446 assert(P.getPointer() != RemInst &&
1447 "Already removed NonLocalPointerDeps info for RemInst");
1449 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps;
1451 // The cache is not valid for any specific block anymore.
1452 NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair();
1454 // Update any entries for RemInst to use the instruction after it.
1455 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
1457 if (DI->getResult().getInst() != RemInst) continue;
1459 // Convert to a dirty entry for the subsequent instruction.
1460 DI->setResult(NewDirtyVal);
1462 if (Instruction *NewDirtyInst = NewDirtyVal.getInst())
1463 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P));
1466 // Re-sort the NonLocalDepInfo. Changing the dirty entry to its
1467 // subsequent value may invalidate the sortedness.
1468 std::sort(NLPDI.begin(), NLPDI.end());
1471 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt);
1473 while (!ReversePtrDepsToAdd.empty()) {
1474 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first]
1475 .insert(ReversePtrDepsToAdd.back().second);
1476 ReversePtrDepsToAdd.pop_back();
1481 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?");
1482 AA->deleteValue(RemInst);
1483 DEBUG(verifyRemoved(RemInst));
1485 /// verifyRemoved - Verify that the specified instruction does not occur
1486 /// in our internal data structures.
1487 void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const {
1488 for (LocalDepMapType::const_iterator I = LocalDeps.begin(),
1489 E = LocalDeps.end(); I != E; ++I) {
1490 assert(I->first != D && "Inst occurs in data structures");
1491 assert(I->second.getInst() != D &&
1492 "Inst occurs in data structures");
1495 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(),
1496 E = NonLocalPointerDeps.end(); I != E; ++I) {
1497 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key");
1498 const NonLocalDepInfo &Val = I->second.NonLocalDeps;
1499 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end();
1501 assert(II->getResult().getInst() != D && "Inst occurs as NLPD value");
1504 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(),
1505 E = NonLocalDeps.end(); I != E; ++I) {
1506 assert(I->first != D && "Inst occurs in data structures");
1507 const PerInstNLInfo &INLD = I->second;
1508 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(),
1509 EE = INLD.first.end(); II != EE; ++II)
1510 assert(II->getResult().getInst() != D && "Inst occurs in data structures");
1513 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(),
1514 E = ReverseLocalDeps.end(); I != E; ++I) {
1515 assert(I->first != D && "Inst occurs in data structures");
1516 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1517 EE = I->second.end(); II != EE; ++II)
1518 assert(*II != D && "Inst occurs in data structures");
1521 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(),
1522 E = ReverseNonLocalDeps.end();
1524 assert(I->first != D && "Inst occurs in data structures");
1525 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1526 EE = I->second.end(); II != EE; ++II)
1527 assert(*II != D && "Inst occurs in data structures");
1530 for (ReverseNonLocalPtrDepTy::const_iterator
1531 I = ReverseNonLocalPtrDeps.begin(),
1532 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) {
1533 assert(I->first != D && "Inst occurs in rev NLPD map");
1535 for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(),
1536 E = I->second.end(); II != E; ++II)
1537 assert(*II != ValueIsLoadPair(D, false) &&
1538 *II != ValueIsLoadPair(D, true) &&
1539 "Inst occurs in ReverseNonLocalPtrDeps map");