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 #include "llvm/Analysis/MemoryDependenceAnalysis.h"
18 #include "llvm/ADT/STLExtras.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/Analysis/AliasAnalysis.h"
21 #include "llvm/Analysis/InstructionSimplify.h"
22 #include "llvm/Analysis/MemoryBuiltins.h"
23 #include "llvm/Analysis/PHITransAddr.h"
24 #include "llvm/Analysis/ValueTracking.h"
25 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/Dominators.h"
27 #include "llvm/IR/Function.h"
28 #include "llvm/IR/Instructions.h"
29 #include "llvm/IR/IntrinsicInst.h"
30 #include "llvm/IR/LLVMContext.h"
31 #include "llvm/IR/PredIteratorCache.h"
32 #include "llvm/Support/Debug.h"
35 #define DEBUG_TYPE "memdep"
37 STATISTIC(NumCacheNonLocal, "Number of fully cached non-local responses");
38 STATISTIC(NumCacheDirtyNonLocal, "Number of dirty cached non-local responses");
39 STATISTIC(NumUncacheNonLocal, "Number of uncached non-local responses");
41 STATISTIC(NumCacheNonLocalPtr,
42 "Number of fully cached non-local ptr responses");
43 STATISTIC(NumCacheDirtyNonLocalPtr,
44 "Number of cached, but dirty, non-local ptr responses");
45 STATISTIC(NumUncacheNonLocalPtr,
46 "Number of uncached non-local ptr responses");
47 STATISTIC(NumCacheCompleteNonLocalPtr,
48 "Number of block queries that were completely cached");
50 // Limit for the number of instructions to scan in a block.
51 static const int BlockScanLimit = 100;
53 char MemoryDependenceAnalysis::ID = 0;
55 // Register this pass...
56 INITIALIZE_PASS_BEGIN(MemoryDependenceAnalysis, "memdep",
57 "Memory Dependence Analysis", false, true)
58 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
59 INITIALIZE_PASS_END(MemoryDependenceAnalysis, "memdep",
60 "Memory Dependence Analysis", false, true)
62 MemoryDependenceAnalysis::MemoryDependenceAnalysis()
63 : FunctionPass(ID), PredCache() {
64 initializeMemoryDependenceAnalysisPass(*PassRegistry::getPassRegistry());
66 MemoryDependenceAnalysis::~MemoryDependenceAnalysis() {
69 /// Clean up memory in between runs
70 void MemoryDependenceAnalysis::releaseMemory() {
73 NonLocalPointerDeps.clear();
74 ReverseLocalDeps.clear();
75 ReverseNonLocalDeps.clear();
76 ReverseNonLocalPtrDeps.clear();
82 /// getAnalysisUsage - Does not modify anything. It uses Alias Analysis.
84 void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
86 AU.addRequiredTransitive<AliasAnalysis>();
89 bool MemoryDependenceAnalysis::runOnFunction(Function &) {
90 AA = &getAnalysis<AliasAnalysis>();
91 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
92 DL = DLP ? &DLP->getDataLayout() : nullptr;
93 DominatorTreeWrapperPass *DTWP =
94 getAnalysisIfAvailable<DominatorTreeWrapperPass>();
95 DT = DTWP ? &DTWP->getDomTree() : nullptr;
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;
129 if (LI->getOrdering() == Monotonic) {
130 Loc = AA->getLocation(LI);
131 return AliasAnalysis::ModRef;
133 Loc = AliasAnalysis::Location();
134 return AliasAnalysis::ModRef;
137 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
138 if (SI->isUnordered()) {
139 Loc = AA->getLocation(SI);
140 return AliasAnalysis::Mod;
142 if (SI->getOrdering() == Monotonic) {
143 Loc = AA->getLocation(SI);
144 return AliasAnalysis::ModRef;
146 Loc = AliasAnalysis::Location();
147 return AliasAnalysis::ModRef;
150 if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
151 Loc = AA->getLocation(V);
152 return AliasAnalysis::ModRef;
155 if (const CallInst *CI = isFreeCall(Inst, AA->getTargetLibraryInfo())) {
156 // calls to free() deallocate the entire structure
157 Loc = AliasAnalysis::Location(CI->getArgOperand(0));
158 return AliasAnalysis::Mod;
161 if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
164 switch (II->getIntrinsicID()) {
165 case Intrinsic::lifetime_start:
166 case Intrinsic::lifetime_end:
167 case Intrinsic::invariant_start:
168 II->getAAMetadata(AAInfo);
169 Loc = AliasAnalysis::Location(II->getArgOperand(1),
170 cast<ConstantInt>(II->getArgOperand(0))
171 ->getZExtValue(), AAInfo);
172 // These intrinsics don't really modify the memory, but returning Mod
173 // will allow them to be handled conservatively.
174 return AliasAnalysis::Mod;
175 case Intrinsic::invariant_end:
176 II->getAAMetadata(AAInfo);
177 Loc = AliasAnalysis::Location(II->getArgOperand(2),
178 cast<ConstantInt>(II->getArgOperand(1))
179 ->getZExtValue(), AAInfo);
180 // These intrinsics don't really modify the memory, but returning Mod
181 // will allow them to be handled conservatively.
182 return AliasAnalysis::Mod;
188 // Otherwise, just do the coarse-grained thing that always works.
189 if (Inst->mayWriteToMemory())
190 return AliasAnalysis::ModRef;
191 if (Inst->mayReadFromMemory())
192 return AliasAnalysis::Ref;
193 return AliasAnalysis::NoModRef;
196 /// getCallSiteDependencyFrom - Private helper for finding the local
197 /// dependencies of a call site.
198 MemDepResult MemoryDependenceAnalysis::
199 getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
200 BasicBlock::iterator ScanIt, BasicBlock *BB) {
201 unsigned Limit = BlockScanLimit;
203 // Walk backwards through the block, looking for dependencies
204 while (ScanIt != BB->begin()) {
205 // Limit the amount of scanning we do so we don't end up with quadratic
206 // running time on extreme testcases.
209 return MemDepResult::getUnknown();
211 Instruction *Inst = --ScanIt;
213 // If this inst is a memory op, get the pointer it accessed
214 AliasAnalysis::Location Loc;
215 AliasAnalysis::ModRefResult MR = GetLocation(Inst, Loc, AA);
217 // A simple instruction.
218 if (AA->getModRefInfo(CS, Loc) != AliasAnalysis::NoModRef)
219 return MemDepResult::getClobber(Inst);
223 if (CallSite InstCS = cast<Value>(Inst)) {
224 // Debug intrinsics don't cause dependences.
225 if (isa<DbgInfoIntrinsic>(Inst)) continue;
226 // If these two calls do not interfere, look past it.
227 switch (AA->getModRefInfo(CS, InstCS)) {
228 case AliasAnalysis::NoModRef:
229 // If the two calls are the same, return InstCS as a Def, so that
230 // CS can be found redundant and eliminated.
231 if (isReadOnlyCall && !(MR & AliasAnalysis::Mod) &&
232 CS.getInstruction()->isIdenticalToWhenDefined(Inst))
233 return MemDepResult::getDef(Inst);
235 // Otherwise if the two calls don't interact (e.g. InstCS is readnone)
239 return MemDepResult::getClobber(Inst);
243 // If we could not obtain a pointer for the instruction and the instruction
244 // touches memory then assume that this is a dependency.
245 if (MR != AliasAnalysis::NoModRef)
246 return MemDepResult::getClobber(Inst);
249 // No dependence found. If this is the entry block of the function, it is
250 // unknown, otherwise it is non-local.
251 if (BB != &BB->getParent()->getEntryBlock())
252 return MemDepResult::getNonLocal();
253 return MemDepResult::getNonFuncLocal();
256 /// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
257 /// would fully overlap MemLoc if done as a wider legal integer load.
259 /// MemLocBase, MemLocOffset are lazily computed here the first time the
260 /// base/offs of memloc is needed.
262 isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc,
263 const Value *&MemLocBase,
266 const DataLayout *DL) {
267 // If we have no target data, we can't do this.
268 if (!DL) return false;
270 // If we haven't already computed the base/offset of MemLoc, do so now.
272 MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, DL);
274 unsigned Size = MemoryDependenceAnalysis::
275 getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size,
280 /// getLoadLoadClobberFullWidthSize - This is a little bit of analysis that
281 /// looks at a memory location for a load (specified by MemLocBase, Offs,
282 /// and Size) and compares it against a load. If the specified load could
283 /// be safely widened to a larger integer load that is 1) still efficient,
284 /// 2) safe for the target, and 3) would provide the specified memory
285 /// location value, then this function returns the size in bytes of the
286 /// load width to use. If not, this returns zero.
287 unsigned MemoryDependenceAnalysis::
288 getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
289 unsigned MemLocSize, const LoadInst *LI,
290 const DataLayout &DL) {
291 // We can only extend simple integer loads.
292 if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0;
294 // Load widening is hostile to ThreadSanitizer: it may cause false positives
295 // or make the reports more cryptic (access sizes are wrong).
296 if (LI->getParent()->getParent()->getAttributes().
297 hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeThread))
300 // Get the base of this load.
302 const Value *LIBase =
303 GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, &DL);
305 // If the two pointers are not based on the same pointer, we can't tell that
307 if (LIBase != MemLocBase) return 0;
309 // Okay, the two values are based on the same pointer, but returned as
310 // no-alias. This happens when we have things like two byte loads at "P+1"
311 // and "P+3". Check to see if increasing the size of the "LI" load up to its
312 // alignment (or the largest native integer type) will allow us to load all
313 // the bits required by MemLoc.
315 // If MemLoc is before LI, then no widening of LI will help us out.
316 if (MemLocOffs < LIOffs) return 0;
318 // Get the alignment of the load in bytes. We assume that it is safe to load
319 // any legal integer up to this size without a problem. For example, if we're
320 // looking at an i8 load on x86-32 that is known 1024 byte aligned, we can
321 // widen it up to an i32 load. If it is known 2-byte aligned, we can widen it
323 unsigned LoadAlign = LI->getAlignment();
325 int64_t MemLocEnd = MemLocOffs+MemLocSize;
327 // If no amount of rounding up will let MemLoc fit into LI, then bail out.
328 if (LIOffs+LoadAlign < MemLocEnd) return 0;
330 // This is the size of the load to try. Start with the next larger power of
332 unsigned NewLoadByteSize = LI->getType()->getPrimitiveSizeInBits()/8U;
333 NewLoadByteSize = NextPowerOf2(NewLoadByteSize);
336 // If this load size is bigger than our known alignment or would not fit
337 // into a native integer register, then we fail.
338 if (NewLoadByteSize > LoadAlign ||
339 !DL.fitsInLegalInteger(NewLoadByteSize*8))
342 if (LIOffs+NewLoadByteSize > MemLocEnd &&
343 LI->getParent()->getParent()->getAttributes().
344 hasAttribute(AttributeSet::FunctionIndex, Attribute::SanitizeAddress))
345 // We will be reading past the location accessed by the original program.
346 // While this is safe in a regular build, Address Safety analysis tools
347 // may start reporting false warnings. So, don't do widening.
350 // If a load of this width would include all of MemLoc, then we succeed.
351 if (LIOffs+NewLoadByteSize >= MemLocEnd)
352 return NewLoadByteSize;
354 NewLoadByteSize <<= 1;
358 /// getPointerDependencyFrom - Return the instruction on which a memory
359 /// location depends. If isLoad is true, this routine ignores may-aliases with
360 /// read-only operations. If isLoad is false, this routine ignores may-aliases
361 /// with reads from read-only locations. If possible, pass the query
362 /// instruction as well; this function may take advantage of the metadata
363 /// annotated to the query instruction to refine the result.
364 MemDepResult MemoryDependenceAnalysis::
365 getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
366 BasicBlock::iterator ScanIt, BasicBlock *BB,
367 Instruction *QueryInst) {
369 const Value *MemLocBase = nullptr;
370 int64_t MemLocOffset = 0;
371 unsigned Limit = BlockScanLimit;
372 bool isInvariantLoad = false;
373 if (isLoad && QueryInst) {
374 LoadInst *LI = dyn_cast<LoadInst>(QueryInst);
375 if (LI && LI->getMetadata(LLVMContext::MD_invariant_load) != nullptr)
376 isInvariantLoad = true;
379 // Walk backwards through the basic block, looking for dependencies.
380 while (ScanIt != BB->begin()) {
381 Instruction *Inst = --ScanIt;
383 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst))
384 // Debug intrinsics don't (and can't) cause dependencies.
385 if (isa<DbgInfoIntrinsic>(II)) continue;
387 // Limit the amount of scanning we do so we don't end up with quadratic
388 // running time on extreme testcases.
391 return MemDepResult::getUnknown();
393 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
394 // If we reach a lifetime begin or end marker, then the query ends here
395 // because the value is undefined.
396 if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
397 // FIXME: This only considers queries directly on the invariant-tagged
398 // pointer, not on query pointers that are indexed off of them. It'd
399 // be nice to handle that at some point (the right approach is to use
400 // GetPointerBaseWithConstantOffset).
401 if (AA->isMustAlias(AliasAnalysis::Location(II->getArgOperand(1)),
403 return MemDepResult::getDef(II);
408 // Values depend on loads if the pointers are must aliased. This means that
409 // a load depends on another must aliased load from the same value.
410 // One exception is atomic loads: a value can depend on an atomic load that it
411 // does not alias with when this atomic load indicates that another thread may
412 // be accessing the location.
413 if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
414 // Atomic loads have complications involved.
415 // A monotonic load is OK if the query inst is itself not atomic.
416 // FIXME: This is overly conservative.
417 if (!LI->isUnordered()) {
419 return MemDepResult::getClobber(LI);
420 if (LI->getOrdering() != Monotonic)
421 return MemDepResult::getClobber(LI);
422 if (auto *QueryLI = dyn_cast<LoadInst>(QueryInst))
423 if (!QueryLI->isSimple())
424 return MemDepResult::getClobber(LI);
425 if (auto *QuerySI = dyn_cast<StoreInst>(QueryInst))
426 if (!QuerySI->isSimple())
427 return MemDepResult::getClobber(LI);
430 // FIXME: this is overly conservative.
431 // While volatile access cannot be eliminated, they do not have to clobber
432 // non-aliasing locations, as normal accesses can for example be reordered
433 // with volatile accesses.
434 if (LI->isVolatile())
435 return MemDepResult::getClobber(LI);
437 AliasAnalysis::Location LoadLoc = AA->getLocation(LI);
439 // If we found a pointer, check if it could be the same as our pointer.
440 AliasAnalysis::AliasResult R = AA->alias(LoadLoc, MemLoc);
443 if (R == AliasAnalysis::NoAlias) {
444 // If this is an over-aligned integer load (for example,
445 // "load i8* %P, align 4") see if it would obviously overlap with the
446 // queried location if widened to a larger load (e.g. if the queried
447 // location is 1 byte at P+1). If so, return it as a load/load
448 // clobber result, allowing the client to decide to widen the load if
450 if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
451 if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() &&
452 isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase,
453 MemLocOffset, LI, DL))
454 return MemDepResult::getClobber(Inst);
459 // Must aliased loads are defs of each other.
460 if (R == AliasAnalysis::MustAlias)
461 return MemDepResult::getDef(Inst);
463 #if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads
464 // in terms of clobbering loads, but since it does this by looking
465 // at the clobbering load directly, it doesn't know about any
466 // phi translation that may have happened along the way.
468 // If we have a partial alias, then return this as a clobber for the
470 if (R == AliasAnalysis::PartialAlias)
471 return MemDepResult::getClobber(Inst);
474 // Random may-alias loads don't depend on each other without a
479 // Stores don't depend on other no-aliased accesses.
480 if (R == AliasAnalysis::NoAlias)
483 // Stores don't alias loads from read-only memory.
484 if (AA->pointsToConstantMemory(LoadLoc))
487 // Stores depend on may/must aliased loads.
488 return MemDepResult::getDef(Inst);
491 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
492 // Atomic stores have complications involved.
493 // A monotonic store is OK if the query inst is itself not atomic.
494 // FIXME: This is overly conservative.
495 if (!SI->isUnordered()) {
497 return MemDepResult::getClobber(SI);
498 if (SI->getOrdering() != Monotonic)
499 return MemDepResult::getClobber(SI);
500 if (auto *QueryLI = dyn_cast<LoadInst>(QueryInst))
501 if (!QueryLI->isSimple())
502 return MemDepResult::getClobber(SI);
503 if (auto *QuerySI = dyn_cast<StoreInst>(QueryInst))
504 if (!QuerySI->isSimple())
505 return MemDepResult::getClobber(SI);
508 // FIXME: this is overly conservative.
509 // While volatile access cannot be eliminated, they do not have to clobber
510 // non-aliasing locations, as normal accesses can for example be reordered
511 // with volatile accesses.
512 if (SI->isVolatile())
513 return MemDepResult::getClobber(SI);
515 // If alias analysis can tell that this store is guaranteed to not modify
516 // the query pointer, ignore it. Use getModRefInfo to handle cases where
517 // the query pointer points to constant memory etc.
518 if (AA->getModRefInfo(SI, MemLoc) == AliasAnalysis::NoModRef)
521 // Ok, this store might clobber the query pointer. Check to see if it is
522 // a must alias: in this case, we want to return this as a def.
523 AliasAnalysis::Location StoreLoc = AA->getLocation(SI);
525 // If we found a pointer, check if it could be the same as our pointer.
526 AliasAnalysis::AliasResult R = AA->alias(StoreLoc, MemLoc);
528 if (R == AliasAnalysis::NoAlias)
530 if (R == AliasAnalysis::MustAlias)
531 return MemDepResult::getDef(Inst);
534 return MemDepResult::getClobber(Inst);
537 // If this is an allocation, and if we know that the accessed pointer is to
538 // the allocation, return Def. This means that there is no dependence and
539 // the access can be optimized based on that. For example, a load could
541 // Note: Only determine this to be a malloc if Inst is the malloc call, not
542 // a subsequent bitcast of the malloc call result. There can be stores to
543 // the malloced memory between the malloc call and its bitcast uses, and we
544 // need to continue scanning until the malloc call.
545 const TargetLibraryInfo *TLI = AA->getTargetLibraryInfo();
546 if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, TLI)) {
547 const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, DL);
549 if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
550 return MemDepResult::getDef(Inst);
551 // Be conservative if the accessed pointer may alias the allocation.
552 if (AA->alias(Inst, AccessPtr) != AliasAnalysis::NoAlias)
553 return MemDepResult::getClobber(Inst);
554 // If the allocation is not aliased and does not read memory (like
555 // strdup), it is safe to ignore.
556 if (isa<AllocaInst>(Inst) ||
557 isMallocLikeFn(Inst, TLI) || isCallocLikeFn(Inst, TLI))
561 // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
562 AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc);
563 // If necessary, perform additional analysis.
564 if (MR == AliasAnalysis::ModRef)
565 MR = AA->callCapturesBefore(Inst, MemLoc, DT);
567 case AliasAnalysis::NoModRef:
568 // If the call has no effect on the queried pointer, just ignore it.
570 case AliasAnalysis::Mod:
571 return MemDepResult::getClobber(Inst);
572 case AliasAnalysis::Ref:
573 // If the call is known to never store to the pointer, and if this is a
574 // load query, we can safely ignore it (scan past it).
578 // Otherwise, there is a potential dependence. Return a clobber.
579 return MemDepResult::getClobber(Inst);
583 // No dependence found. If this is the entry block of the function, it is
584 // unknown, otherwise it is non-local.
585 if (BB != &BB->getParent()->getEntryBlock())
586 return MemDepResult::getNonLocal();
587 return MemDepResult::getNonFuncLocal();
590 /// getDependency - Return the instruction on which a memory operation
592 MemDepResult MemoryDependenceAnalysis::getDependency(Instruction *QueryInst) {
593 Instruction *ScanPos = QueryInst;
595 // Check for a cached result
596 MemDepResult &LocalCache = LocalDeps[QueryInst];
598 // If the cached entry is non-dirty, just return it. Note that this depends
599 // on MemDepResult's default constructing to 'dirty'.
600 if (!LocalCache.isDirty())
603 // Otherwise, if we have a dirty entry, we know we can start the scan at that
604 // instruction, which may save us some work.
605 if (Instruction *Inst = LocalCache.getInst()) {
608 RemoveFromReverseMap(ReverseLocalDeps, Inst, QueryInst);
611 BasicBlock *QueryParent = QueryInst->getParent();
614 if (BasicBlock::iterator(QueryInst) == QueryParent->begin()) {
615 // No dependence found. If this is the entry block of the function, it is
616 // unknown, otherwise it is non-local.
617 if (QueryParent != &QueryParent->getParent()->getEntryBlock())
618 LocalCache = MemDepResult::getNonLocal();
620 LocalCache = MemDepResult::getNonFuncLocal();
622 AliasAnalysis::Location MemLoc;
623 AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
625 // If we can do a pointer scan, make it happen.
626 bool isLoad = !(MR & AliasAnalysis::Mod);
627 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(QueryInst))
628 isLoad |= II->getIntrinsicID() == Intrinsic::lifetime_start;
630 LocalCache = getPointerDependencyFrom(MemLoc, isLoad, ScanPos,
631 QueryParent, QueryInst);
632 } else if (isa<CallInst>(QueryInst) || isa<InvokeInst>(QueryInst)) {
633 CallSite QueryCS(QueryInst);
634 bool isReadOnly = AA->onlyReadsMemory(QueryCS);
635 LocalCache = getCallSiteDependencyFrom(QueryCS, isReadOnly, ScanPos,
638 // Non-memory instruction.
639 LocalCache = MemDepResult::getUnknown();
642 // Remember the result!
643 if (Instruction *I = LocalCache.getInst())
644 ReverseLocalDeps[I].insert(QueryInst);
650 /// AssertSorted - This method is used when -debug is specified to verify that
651 /// cache arrays are properly kept sorted.
652 static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
654 if (Count == -1) Count = Cache.size();
655 if (Count == 0) return;
657 for (unsigned i = 1; i != unsigned(Count); ++i)
658 assert(!(Cache[i] < Cache[i-1]) && "Cache isn't sorted!");
662 /// getNonLocalCallDependency - Perform a full dependency query for the
663 /// specified call, returning the set of blocks that the value is
664 /// potentially live across. The returned set of results will include a
665 /// "NonLocal" result for all blocks where the value is live across.
667 /// This method assumes the instruction returns a "NonLocal" dependency
668 /// within its own block.
670 /// This returns a reference to an internal data structure that may be
671 /// invalidated on the next non-local query or when an instruction is
672 /// removed. Clients must copy this data if they want it around longer than
674 const MemoryDependenceAnalysis::NonLocalDepInfo &
675 MemoryDependenceAnalysis::getNonLocalCallDependency(CallSite QueryCS) {
676 assert(getDependency(QueryCS.getInstruction()).isNonLocal() &&
677 "getNonLocalCallDependency should only be used on calls with non-local deps!");
678 PerInstNLInfo &CacheP = NonLocalDeps[QueryCS.getInstruction()];
679 NonLocalDepInfo &Cache = CacheP.first;
681 /// DirtyBlocks - This is the set of blocks that need to be recomputed. In
682 /// the cached case, this can happen due to instructions being deleted etc. In
683 /// the uncached case, this starts out as the set of predecessors we care
685 SmallVector<BasicBlock*, 32> DirtyBlocks;
687 if (!Cache.empty()) {
688 // Okay, we have a cache entry. If we know it is not dirty, just return it
689 // with no computation.
690 if (!CacheP.second) {
695 // If we already have a partially computed set of results, scan them to
696 // determine what is dirty, seeding our initial DirtyBlocks worklist.
697 for (NonLocalDepInfo::iterator I = Cache.begin(), E = Cache.end();
699 if (I->getResult().isDirty())
700 DirtyBlocks.push_back(I->getBB());
702 // Sort the cache so that we can do fast binary search lookups below.
703 std::sort(Cache.begin(), Cache.end());
705 ++NumCacheDirtyNonLocal;
706 //cerr << "CACHED CASE: " << DirtyBlocks.size() << " dirty: "
707 // << Cache.size() << " cached: " << *QueryInst;
709 // Seed DirtyBlocks with each of the preds of QueryInst's block.
710 BasicBlock *QueryBB = QueryCS.getInstruction()->getParent();
711 for (BasicBlock **PI = PredCache->GetPreds(QueryBB); *PI; ++PI)
712 DirtyBlocks.push_back(*PI);
713 ++NumUncacheNonLocal;
716 // isReadonlyCall - If this is a read-only call, we can be more aggressive.
717 bool isReadonlyCall = AA->onlyReadsMemory(QueryCS);
719 SmallPtrSet<BasicBlock*, 64> Visited;
721 unsigned NumSortedEntries = Cache.size();
722 DEBUG(AssertSorted(Cache));
724 // Iterate while we still have blocks to update.
725 while (!DirtyBlocks.empty()) {
726 BasicBlock *DirtyBB = DirtyBlocks.back();
727 DirtyBlocks.pop_back();
729 // Already processed this block?
730 if (!Visited.insert(DirtyBB))
733 // Do a binary search to see if we already have an entry for this block in
734 // the cache set. If so, find it.
735 DEBUG(AssertSorted(Cache, NumSortedEntries));
736 NonLocalDepInfo::iterator Entry =
737 std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries,
738 NonLocalDepEntry(DirtyBB));
739 if (Entry != Cache.begin() && std::prev(Entry)->getBB() == DirtyBB)
742 NonLocalDepEntry *ExistingResult = nullptr;
743 if (Entry != Cache.begin()+NumSortedEntries &&
744 Entry->getBB() == DirtyBB) {
745 // If we already have an entry, and if it isn't already dirty, the block
747 if (!Entry->getResult().isDirty())
750 // Otherwise, remember this slot so we can update the value.
751 ExistingResult = &*Entry;
754 // If the dirty entry has a pointer, start scanning from it so we don't have
755 // to rescan the entire block.
756 BasicBlock::iterator ScanPos = DirtyBB->end();
757 if (ExistingResult) {
758 if (Instruction *Inst = ExistingResult->getResult().getInst()) {
760 // We're removing QueryInst's use of Inst.
761 RemoveFromReverseMap(ReverseNonLocalDeps, Inst,
762 QueryCS.getInstruction());
766 // Find out if this block has a local dependency for QueryInst.
769 if (ScanPos != DirtyBB->begin()) {
770 Dep = getCallSiteDependencyFrom(QueryCS, isReadonlyCall,ScanPos, DirtyBB);
771 } else if (DirtyBB != &DirtyBB->getParent()->getEntryBlock()) {
772 // No dependence found. If this is the entry block of the function, it is
773 // a clobber, otherwise it is unknown.
774 Dep = MemDepResult::getNonLocal();
776 Dep = MemDepResult::getNonFuncLocal();
779 // If we had a dirty entry for the block, update it. Otherwise, just add
782 ExistingResult->setResult(Dep);
784 Cache.push_back(NonLocalDepEntry(DirtyBB, Dep));
786 // If the block has a dependency (i.e. it isn't completely transparent to
787 // the value), remember the association!
788 if (!Dep.isNonLocal()) {
789 // Keep the ReverseNonLocalDeps map up to date so we can efficiently
790 // update this when we remove instructions.
791 if (Instruction *Inst = Dep.getInst())
792 ReverseNonLocalDeps[Inst].insert(QueryCS.getInstruction());
795 // If the block *is* completely transparent to the load, we need to check
796 // the predecessors of this block. Add them to our worklist.
797 for (BasicBlock **PI = PredCache->GetPreds(DirtyBB); *PI; ++PI)
798 DirtyBlocks.push_back(*PI);
805 /// getNonLocalPointerDependency - Perform a full dependency query for an
806 /// access to the specified (non-volatile) memory location, returning the
807 /// set of instructions that either define or clobber the value.
809 /// This method assumes the pointer has a "NonLocal" dependency within its
812 void MemoryDependenceAnalysis::
813 getNonLocalPointerDependency(const AliasAnalysis::Location &Loc, bool isLoad,
815 SmallVectorImpl<NonLocalDepResult> &Result) {
816 assert(Loc.Ptr->getType()->isPointerTy() &&
817 "Can't get pointer deps of a non-pointer!");
820 PHITransAddr Address(const_cast<Value *>(Loc.Ptr), DL);
822 // This is the set of blocks we've inspected, and the pointer we consider in
823 // each block. Because of critical edges, we currently bail out if querying
824 // a block with multiple different pointers. This can happen during PHI
826 DenseMap<BasicBlock*, Value*> Visited;
827 if (!getNonLocalPointerDepFromBB(Address, Loc, isLoad, FromBB,
828 Result, Visited, true))
831 Result.push_back(NonLocalDepResult(FromBB,
832 MemDepResult::getUnknown(),
833 const_cast<Value *>(Loc.Ptr)));
836 /// GetNonLocalInfoForBlock - Compute the memdep value for BB with
837 /// Pointer/PointeeSize using either cached information in Cache or by doing a
838 /// lookup (which may use dirty cache info if available). If we do a lookup,
839 /// add the result to the cache.
840 MemDepResult MemoryDependenceAnalysis::
841 GetNonLocalInfoForBlock(const AliasAnalysis::Location &Loc,
842 bool isLoad, BasicBlock *BB,
843 NonLocalDepInfo *Cache, unsigned NumSortedEntries) {
845 // Do a binary search to see if we already have an entry for this block in
846 // the cache set. If so, find it.
847 NonLocalDepInfo::iterator Entry =
848 std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries,
849 NonLocalDepEntry(BB));
850 if (Entry != Cache->begin() && (Entry-1)->getBB() == BB)
853 NonLocalDepEntry *ExistingResult = nullptr;
854 if (Entry != Cache->begin()+NumSortedEntries && Entry->getBB() == BB)
855 ExistingResult = &*Entry;
857 // If we have a cached entry, and it is non-dirty, use it as the value for
859 if (ExistingResult && !ExistingResult->getResult().isDirty()) {
860 ++NumCacheNonLocalPtr;
861 return ExistingResult->getResult();
864 // Otherwise, we have to scan for the value. If we have a dirty cache
865 // entry, start scanning from its position, otherwise we scan from the end
867 BasicBlock::iterator ScanPos = BB->end();
868 if (ExistingResult && ExistingResult->getResult().getInst()) {
869 assert(ExistingResult->getResult().getInst()->getParent() == BB &&
870 "Instruction invalidated?");
871 ++NumCacheDirtyNonLocalPtr;
872 ScanPos = ExistingResult->getResult().getInst();
874 // Eliminating the dirty entry from 'Cache', so update the reverse info.
875 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
876 RemoveFromReverseMap(ReverseNonLocalPtrDeps, ScanPos, CacheKey);
878 ++NumUncacheNonLocalPtr;
881 // Scan the block for the dependency.
882 MemDepResult Dep = getPointerDependencyFrom(Loc, isLoad, ScanPos, BB);
884 // If we had a dirty entry for the block, update it. Otherwise, just add
887 ExistingResult->setResult(Dep);
889 Cache->push_back(NonLocalDepEntry(BB, Dep));
891 // If the block has a dependency (i.e. it isn't completely transparent to
892 // the value), remember the reverse association because we just added it
894 if (!Dep.isDef() && !Dep.isClobber())
897 // Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
898 // update MemDep when we remove instructions.
899 Instruction *Inst = Dep.getInst();
900 assert(Inst && "Didn't depend on anything?");
901 ValueIsLoadPair CacheKey(Loc.Ptr, isLoad);
902 ReverseNonLocalPtrDeps[Inst].insert(CacheKey);
906 /// SortNonLocalDepInfoCache - Sort the a NonLocalDepInfo cache, given a certain
907 /// number of elements in the array that are already properly ordered. This is
908 /// optimized for the case when only a few entries are added.
910 SortNonLocalDepInfoCache(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
911 unsigned NumSortedEntries) {
912 switch (Cache.size() - NumSortedEntries) {
914 // done, no new entries.
917 // Two new entries, insert the last one into place.
918 NonLocalDepEntry Val = Cache.back();
920 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
921 std::upper_bound(Cache.begin(), Cache.end()-1, Val);
922 Cache.insert(Entry, Val);
926 // One new entry, Just insert the new value at the appropriate position.
927 if (Cache.size() != 1) {
928 NonLocalDepEntry Val = Cache.back();
930 MemoryDependenceAnalysis::NonLocalDepInfo::iterator Entry =
931 std::upper_bound(Cache.begin(), Cache.end(), Val);
932 Cache.insert(Entry, Val);
936 // Added many values, do a full scale sort.
937 std::sort(Cache.begin(), Cache.end());
942 /// getNonLocalPointerDepFromBB - Perform a dependency query based on
943 /// pointer/pointeesize starting at the end of StartBB. Add any clobber/def
944 /// results to the results vector and keep track of which blocks are visited in
947 /// This has special behavior for the first block queries (when SkipFirstBlock
948 /// is true). In this special case, it ignores the contents of the specified
949 /// block and starts returning dependence info for its predecessors.
951 /// This function returns false on success, or true to indicate that it could
952 /// not compute dependence information for some reason. This should be treated
953 /// as a clobber dependence on the first instruction in the predecessor block.
954 bool MemoryDependenceAnalysis::
955 getNonLocalPointerDepFromBB(const PHITransAddr &Pointer,
956 const AliasAnalysis::Location &Loc,
957 bool isLoad, BasicBlock *StartBB,
958 SmallVectorImpl<NonLocalDepResult> &Result,
959 DenseMap<BasicBlock*, Value*> &Visited,
960 bool SkipFirstBlock) {
961 // Look up the cached info for Pointer.
962 ValueIsLoadPair CacheKey(Pointer.getAddr(), isLoad);
964 // Set up a temporary NLPI value. If the map doesn't yet have an entry for
965 // CacheKey, this value will be inserted as the associated value. Otherwise,
966 // it'll be ignored, and we'll have to check to see if the cached size and
967 // aa tags are consistent with the current query.
968 NonLocalPointerInfo InitialNLPI;
969 InitialNLPI.Size = Loc.Size;
970 InitialNLPI.AATags = Loc.AATags;
972 // Get the NLPI for CacheKey, inserting one into the map if it doesn't
974 std::pair<CachedNonLocalPointerInfo::iterator, bool> Pair =
975 NonLocalPointerDeps.insert(std::make_pair(CacheKey, InitialNLPI));
976 NonLocalPointerInfo *CacheInfo = &Pair.first->second;
978 // If we already have a cache entry for this CacheKey, we may need to do some
979 // work to reconcile the cache entry and the current query.
981 if (CacheInfo->Size < Loc.Size) {
982 // The query's Size is greater than the cached one. Throw out the
983 // cached data and proceed with the query at the greater size.
984 CacheInfo->Pair = BBSkipFirstBlockPair();
985 CacheInfo->Size = Loc.Size;
986 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
987 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
988 if (Instruction *Inst = DI->getResult().getInst())
989 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
990 CacheInfo->NonLocalDeps.clear();
991 } else if (CacheInfo->Size > Loc.Size) {
992 // This query's Size is less than the cached one. Conservatively restart
993 // the query using the greater size.
994 return getNonLocalPointerDepFromBB(Pointer,
995 Loc.getWithNewSize(CacheInfo->Size),
996 isLoad, StartBB, Result, Visited,
1000 // If the query's AATags are inconsistent with the cached one,
1001 // conservatively throw out the cached data and restart the query with
1002 // no tag if needed.
1003 if (CacheInfo->AATags != Loc.AATags) {
1004 if (CacheInfo->AATags) {
1005 CacheInfo->Pair = BBSkipFirstBlockPair();
1006 CacheInfo->AATags = AAMDNodes();
1007 for (NonLocalDepInfo::iterator DI = CacheInfo->NonLocalDeps.begin(),
1008 DE = CacheInfo->NonLocalDeps.end(); DI != DE; ++DI)
1009 if (Instruction *Inst = DI->getResult().getInst())
1010 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Inst, CacheKey);
1011 CacheInfo->NonLocalDeps.clear();
1014 return getNonLocalPointerDepFromBB(Pointer, Loc.getWithoutAATags(),
1015 isLoad, StartBB, Result, Visited,
1020 NonLocalDepInfo *Cache = &CacheInfo->NonLocalDeps;
1022 // If we have valid cached information for exactly the block we are
1023 // investigating, just return it with no recomputation.
1024 if (CacheInfo->Pair == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
1025 // We have a fully cached result for this query then we can just return the
1026 // cached results and populate the visited set. However, we have to verify
1027 // that we don't already have conflicting results for these blocks. Check
1028 // to ensure that if a block in the results set is in the visited set that
1029 // it was for the same pointer query.
1030 if (!Visited.empty()) {
1031 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
1033 DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->getBB());
1034 if (VI == Visited.end() || VI->second == Pointer.getAddr())
1037 // We have a pointer mismatch in a block. Just return clobber, saying
1038 // that something was clobbered in this result. We could also do a
1039 // non-fully cached query, but there is little point in doing this.
1044 Value *Addr = Pointer.getAddr();
1045 for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
1047 Visited.insert(std::make_pair(I->getBB(), Addr));
1048 if (I->getResult().isNonLocal()) {
1053 Result.push_back(NonLocalDepResult(I->getBB(),
1054 MemDepResult::getUnknown(),
1056 } else if (DT->isReachableFromEntry(I->getBB())) {
1057 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(), Addr));
1060 ++NumCacheCompleteNonLocalPtr;
1064 // Otherwise, either this is a new block, a block with an invalid cache
1065 // pointer or one that we're about to invalidate by putting more info into it
1066 // than its valid cache info. If empty, the result will be valid cache info,
1067 // otherwise it isn't.
1069 CacheInfo->Pair = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
1071 CacheInfo->Pair = BBSkipFirstBlockPair();
1073 SmallVector<BasicBlock*, 32> Worklist;
1074 Worklist.push_back(StartBB);
1076 // PredList used inside loop.
1077 SmallVector<std::pair<BasicBlock*, PHITransAddr>, 16> PredList;
1079 // Keep track of the entries that we know are sorted. Previously cached
1080 // entries will all be sorted. The entries we add we only sort on demand (we
1081 // don't insert every element into its sorted position). We know that we
1082 // won't get any reuse from currently inserted values, because we don't
1083 // revisit blocks after we insert info for them.
1084 unsigned NumSortedEntries = Cache->size();
1085 DEBUG(AssertSorted(*Cache));
1087 while (!Worklist.empty()) {
1088 BasicBlock *BB = Worklist.pop_back_val();
1090 // Skip the first block if we have it.
1091 if (!SkipFirstBlock) {
1092 // Analyze the dependency of *Pointer in FromBB. See if we already have
1094 assert(Visited.count(BB) && "Should check 'visited' before adding to WL");
1096 // Get the dependency info for Pointer in BB. If we have cached
1097 // information, we will use it, otherwise we compute it.
1098 DEBUG(AssertSorted(*Cache, NumSortedEntries));
1099 MemDepResult Dep = GetNonLocalInfoForBlock(Loc, isLoad, BB, Cache,
1102 // If we got a Def or Clobber, add this to the list of results.
1103 if (!Dep.isNonLocal()) {
1105 Result.push_back(NonLocalDepResult(BB,
1106 MemDepResult::getUnknown(),
1107 Pointer.getAddr()));
1109 } else if (DT->isReachableFromEntry(BB)) {
1110 Result.push_back(NonLocalDepResult(BB, Dep, Pointer.getAddr()));
1116 // If 'Pointer' is an instruction defined in this block, then we need to do
1117 // phi translation to change it into a value live in the predecessor block.
1118 // If not, we just add the predecessors to the worklist and scan them with
1119 // the same Pointer.
1120 if (!Pointer.NeedsPHITranslationFromBlock(BB)) {
1121 SkipFirstBlock = false;
1122 SmallVector<BasicBlock*, 16> NewBlocks;
1123 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1124 // Verify that we haven't looked at this block yet.
1125 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1126 InsertRes = Visited.insert(std::make_pair(*PI, Pointer.getAddr()));
1127 if (InsertRes.second) {
1128 // First time we've looked at *PI.
1129 NewBlocks.push_back(*PI);
1133 // If we have seen this block before, but it was with a different
1134 // pointer then we have a phi translation failure and we have to treat
1135 // this as a clobber.
1136 if (InsertRes.first->second != Pointer.getAddr()) {
1137 // Make sure to clean up the Visited map before continuing on to
1138 // PredTranslationFailure.
1139 for (unsigned i = 0; i < NewBlocks.size(); i++)
1140 Visited.erase(NewBlocks[i]);
1141 goto PredTranslationFailure;
1144 Worklist.append(NewBlocks.begin(), NewBlocks.end());
1148 // We do need to do phi translation, if we know ahead of time we can't phi
1149 // translate this value, don't even try.
1150 if (!Pointer.IsPotentiallyPHITranslatable())
1151 goto PredTranslationFailure;
1153 // We may have added values to the cache list before this PHI translation.
1154 // If so, we haven't done anything to ensure that the cache remains sorted.
1155 // Sort it now (if needed) so that recursive invocations of
1156 // getNonLocalPointerDepFromBB and other routines that could reuse the cache
1157 // value will only see properly sorted cache arrays.
1158 if (Cache && NumSortedEntries != Cache->size()) {
1159 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1160 NumSortedEntries = Cache->size();
1165 for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
1166 BasicBlock *Pred = *PI;
1167 PredList.push_back(std::make_pair(Pred, Pointer));
1169 // Get the PHI translated pointer in this predecessor. This can fail if
1170 // not translatable, in which case the getAddr() returns null.
1171 PHITransAddr &PredPointer = PredList.back().second;
1172 PredPointer.PHITranslateValue(BB, Pred, nullptr);
1174 Value *PredPtrVal = PredPointer.getAddr();
1176 // Check to see if we have already visited this pred block with another
1177 // pointer. If so, we can't do this lookup. This failure can occur
1178 // with PHI translation when a critical edge exists and the PHI node in
1179 // the successor translates to a pointer value different than the
1180 // pointer the block was first analyzed with.
1181 std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
1182 InsertRes = Visited.insert(std::make_pair(Pred, PredPtrVal));
1184 if (!InsertRes.second) {
1185 // We found the pred; take it off the list of preds to visit.
1186 PredList.pop_back();
1188 // If the predecessor was visited with PredPtr, then we already did
1189 // the analysis and can ignore it.
1190 if (InsertRes.first->second == PredPtrVal)
1193 // Otherwise, the block was previously analyzed with a different
1194 // pointer. We can't represent the result of this case, so we just
1195 // treat this as a phi translation failure.
1197 // Make sure to clean up the Visited map before continuing on to
1198 // PredTranslationFailure.
1199 for (unsigned i = 0, n = PredList.size(); i < n; ++i)
1200 Visited.erase(PredList[i].first);
1202 goto PredTranslationFailure;
1206 // Actually process results here; this need to be a separate loop to avoid
1207 // calling getNonLocalPointerDepFromBB for blocks we don't want to return
1208 // any results for. (getNonLocalPointerDepFromBB will modify our
1209 // datastructures in ways the code after the PredTranslationFailure label
1211 for (unsigned i = 0, n = PredList.size(); i < n; ++i) {
1212 BasicBlock *Pred = PredList[i].first;
1213 PHITransAddr &PredPointer = PredList[i].second;
1214 Value *PredPtrVal = PredPointer.getAddr();
1216 bool CanTranslate = true;
1217 // If PHI translation was unable to find an available pointer in this
1218 // predecessor, then we have to assume that the pointer is clobbered in
1219 // that predecessor. We can still do PRE of the load, which would insert
1220 // a computation of the pointer in this predecessor.
1222 CanTranslate = false;
1224 // FIXME: it is entirely possible that PHI translating will end up with
1225 // the same value. Consider PHI translating something like:
1226 // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need*
1227 // to recurse here, pedantically speaking.
1229 // If getNonLocalPointerDepFromBB fails here, that means the cached
1230 // result conflicted with the Visited list; we have to conservatively
1231 // assume it is unknown, but this also does not block PRE of the load.
1232 if (!CanTranslate ||
1233 getNonLocalPointerDepFromBB(PredPointer,
1234 Loc.getWithNewPtr(PredPtrVal),
1237 // Add the entry to the Result list.
1238 NonLocalDepResult Entry(Pred, MemDepResult::getUnknown(), PredPtrVal);
1239 Result.push_back(Entry);
1241 // Since we had a phi translation failure, the cache for CacheKey won't
1242 // include all of the entries that we need to immediately satisfy future
1243 // queries. Mark this in NonLocalPointerDeps by setting the
1244 // BBSkipFirstBlockPair pointer to null. This requires reuse of the
1245 // cached value to do more work but not miss the phi trans failure.
1246 NonLocalPointerInfo &NLPI = NonLocalPointerDeps[CacheKey];
1247 NLPI.Pair = BBSkipFirstBlockPair();
1252 // Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
1253 CacheInfo = &NonLocalPointerDeps[CacheKey];
1254 Cache = &CacheInfo->NonLocalDeps;
1255 NumSortedEntries = Cache->size();
1257 // Since we did phi translation, the "Cache" set won't contain all of the
1258 // results for the query. This is ok (we can still use it to accelerate
1259 // specific block queries) but we can't do the fastpath "return all
1260 // results from the set" Clear out the indicator for this.
1261 CacheInfo->Pair = BBSkipFirstBlockPair();
1262 SkipFirstBlock = false;
1265 PredTranslationFailure:
1266 // The following code is "failure"; we can't produce a sane translation
1267 // for the given block. It assumes that we haven't modified any of
1268 // our datastructures while processing the current block.
1271 // Refresh the CacheInfo/Cache pointer if it got invalidated.
1272 CacheInfo = &NonLocalPointerDeps[CacheKey];
1273 Cache = &CacheInfo->NonLocalDeps;
1274 NumSortedEntries = Cache->size();
1277 // Since we failed phi translation, the "Cache" set won't contain all of the
1278 // results for the query. This is ok (we can still use it to accelerate
1279 // specific block queries) but we can't do the fastpath "return all
1280 // results from the set". Clear out the indicator for this.
1281 CacheInfo->Pair = BBSkipFirstBlockPair();
1283 // If *nothing* works, mark the pointer as unknown.
1285 // If this is the magic first block, return this as a clobber of the whole
1286 // incoming value. Since we can't phi translate to one of the predecessors,
1287 // we have to bail out.
1291 for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) {
1292 assert(I != Cache->rend() && "Didn't find current block??");
1293 if (I->getBB() != BB)
1296 assert(I->getResult().isNonLocal() &&
1297 "Should only be here with transparent block");
1298 I->setResult(MemDepResult::getUnknown());
1299 Result.push_back(NonLocalDepResult(I->getBB(), I->getResult(),
1300 Pointer.getAddr()));
1305 // Okay, we're done now. If we added new values to the cache, re-sort it.
1306 SortNonLocalDepInfoCache(*Cache, NumSortedEntries);
1307 DEBUG(AssertSorted(*Cache));
1311 /// RemoveCachedNonLocalPointerDependencies - If P exists in
1312 /// CachedNonLocalPointerInfo, remove it.
1313 void MemoryDependenceAnalysis::
1314 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair P) {
1315 CachedNonLocalPointerInfo::iterator It =
1316 NonLocalPointerDeps.find(P);
1317 if (It == NonLocalPointerDeps.end()) return;
1319 // Remove all of the entries in the BB->val map. This involves removing
1320 // instructions from the reverse map.
1321 NonLocalDepInfo &PInfo = It->second.NonLocalDeps;
1323 for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
1324 Instruction *Target = PInfo[i].getResult().getInst();
1325 if (!Target) continue; // Ignore non-local dep results.
1326 assert(Target->getParent() == PInfo[i].getBB());
1328 // Eliminating the dirty entry from 'Cache', so update the reverse info.
1329 RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P);
1332 // Remove P from NonLocalPointerDeps (which deletes NonLocalDepInfo).
1333 NonLocalPointerDeps.erase(It);
1337 /// invalidateCachedPointerInfo - This method is used to invalidate cached
1338 /// information about the specified pointer, because it may be too
1339 /// conservative in memdep. This is an optional call that can be used when
1340 /// the client detects an equivalence between the pointer and some other
1341 /// value and replaces the other value with ptr. This can make Ptr available
1342 /// in more places that cached info does not necessarily keep.
1343 void MemoryDependenceAnalysis::invalidateCachedPointerInfo(Value *Ptr) {
1344 // If Ptr isn't really a pointer, just ignore it.
1345 if (!Ptr->getType()->isPointerTy()) return;
1346 // Flush store info for the pointer.
1347 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, false));
1348 // Flush load info for the pointer.
1349 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(Ptr, true));
1352 /// invalidateCachedPredecessors - Clear the PredIteratorCache info.
1353 /// This needs to be done when the CFG changes, e.g., due to splitting
1355 void MemoryDependenceAnalysis::invalidateCachedPredecessors() {
1359 /// removeInstruction - Remove an instruction from the dependence analysis,
1360 /// updating the dependence of instructions that previously depended on it.
1361 /// This method attempts to keep the cache coherent using the reverse map.
1362 void MemoryDependenceAnalysis::removeInstruction(Instruction *RemInst) {
1363 // Walk through the Non-local dependencies, removing this one as the value
1364 // for any cached queries.
1365 NonLocalDepMapType::iterator NLDI = NonLocalDeps.find(RemInst);
1366 if (NLDI != NonLocalDeps.end()) {
1367 NonLocalDepInfo &BlockMap = NLDI->second.first;
1368 for (NonLocalDepInfo::iterator DI = BlockMap.begin(), DE = BlockMap.end();
1370 if (Instruction *Inst = DI->getResult().getInst())
1371 RemoveFromReverseMap(ReverseNonLocalDeps, Inst, RemInst);
1372 NonLocalDeps.erase(NLDI);
1375 // If we have a cached local dependence query for this instruction, remove it.
1377 LocalDepMapType::iterator LocalDepEntry = LocalDeps.find(RemInst);
1378 if (LocalDepEntry != LocalDeps.end()) {
1379 // Remove us from DepInst's reverse set now that the local dep info is gone.
1380 if (Instruction *Inst = LocalDepEntry->second.getInst())
1381 RemoveFromReverseMap(ReverseLocalDeps, Inst, RemInst);
1383 // Remove this local dependency info.
1384 LocalDeps.erase(LocalDepEntry);
1387 // If we have any cached pointer dependencies on this instruction, remove
1388 // them. If the instruction has non-pointer type, then it can't be a pointer
1391 // Remove it from both the load info and the store info. The instruction
1392 // can't be in either of these maps if it is non-pointer.
1393 if (RemInst->getType()->isPointerTy()) {
1394 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, false));
1395 RemoveCachedNonLocalPointerDependencies(ValueIsLoadPair(RemInst, true));
1398 // Loop over all of the things that depend on the instruction we're removing.
1400 SmallVector<std::pair<Instruction*, Instruction*>, 8> ReverseDepsToAdd;
1402 // If we find RemInst as a clobber or Def in any of the maps for other values,
1403 // we need to replace its entry with a dirty version of the instruction after
1404 // it. If RemInst is a terminator, we use a null dirty value.
1406 // Using a dirty version of the instruction after RemInst saves having to scan
1407 // the entire block to get to this point.
1408 MemDepResult NewDirtyVal;
1409 if (!RemInst->isTerminator())
1410 NewDirtyVal = MemDepResult::getDirty(++BasicBlock::iterator(RemInst));
1412 ReverseDepMapType::iterator ReverseDepIt = ReverseLocalDeps.find(RemInst);
1413 if (ReverseDepIt != ReverseLocalDeps.end()) {
1414 SmallPtrSet<Instruction*, 4> &ReverseDeps = ReverseDepIt->second;
1415 // RemInst can't be the terminator if it has local stuff depending on it.
1416 assert(!ReverseDeps.empty() && !isa<TerminatorInst>(RemInst) &&
1417 "Nothing can locally depend on a terminator");
1419 for (SmallPtrSet<Instruction*, 4>::iterator I = ReverseDeps.begin(),
1420 E = ReverseDeps.end(); I != E; ++I) {
1421 Instruction *InstDependingOnRemInst = *I;
1422 assert(InstDependingOnRemInst != RemInst &&
1423 "Already removed our local dep info");
1425 LocalDeps[InstDependingOnRemInst] = NewDirtyVal;
1427 // Make sure to remember that new things depend on NewDepInst.
1428 assert(NewDirtyVal.getInst() && "There is no way something else can have "
1429 "a local dep on this if it is a terminator!");
1430 ReverseDepsToAdd.push_back(std::make_pair(NewDirtyVal.getInst(),
1431 InstDependingOnRemInst));
1434 ReverseLocalDeps.erase(ReverseDepIt);
1436 // Add new reverse deps after scanning the set, to avoid invalidating the
1437 // 'ReverseDeps' reference.
1438 while (!ReverseDepsToAdd.empty()) {
1439 ReverseLocalDeps[ReverseDepsToAdd.back().first]
1440 .insert(ReverseDepsToAdd.back().second);
1441 ReverseDepsToAdd.pop_back();
1445 ReverseDepIt = ReverseNonLocalDeps.find(RemInst);
1446 if (ReverseDepIt != ReverseNonLocalDeps.end()) {
1447 SmallPtrSet<Instruction*, 4> &Set = ReverseDepIt->second;
1448 for (SmallPtrSet<Instruction*, 4>::iterator I = Set.begin(), E = Set.end();
1450 assert(*I != RemInst && "Already removed NonLocalDep info for RemInst");
1452 PerInstNLInfo &INLD = NonLocalDeps[*I];
1453 // The information is now dirty!
1456 for (NonLocalDepInfo::iterator DI = INLD.first.begin(),
1457 DE = INLD.first.end(); DI != DE; ++DI) {
1458 if (DI->getResult().getInst() != RemInst) continue;
1460 // Convert to a dirty entry for the subsequent instruction.
1461 DI->setResult(NewDirtyVal);
1463 if (Instruction *NextI = NewDirtyVal.getInst())
1464 ReverseDepsToAdd.push_back(std::make_pair(NextI, *I));
1468 ReverseNonLocalDeps.erase(ReverseDepIt);
1470 // Add new reverse deps after scanning the set, to avoid invalidating 'Set'
1471 while (!ReverseDepsToAdd.empty()) {
1472 ReverseNonLocalDeps[ReverseDepsToAdd.back().first]
1473 .insert(ReverseDepsToAdd.back().second);
1474 ReverseDepsToAdd.pop_back();
1478 // If the instruction is in ReverseNonLocalPtrDeps then it appears as a
1479 // value in the NonLocalPointerDeps info.
1480 ReverseNonLocalPtrDepTy::iterator ReversePtrDepIt =
1481 ReverseNonLocalPtrDeps.find(RemInst);
1482 if (ReversePtrDepIt != ReverseNonLocalPtrDeps.end()) {
1483 SmallPtrSet<ValueIsLoadPair, 4> &Set = ReversePtrDepIt->second;
1484 SmallVector<std::pair<Instruction*, ValueIsLoadPair>,8> ReversePtrDepsToAdd;
1486 for (SmallPtrSet<ValueIsLoadPair, 4>::iterator I = Set.begin(),
1487 E = Set.end(); I != E; ++I) {
1488 ValueIsLoadPair P = *I;
1489 assert(P.getPointer() != RemInst &&
1490 "Already removed NonLocalPointerDeps info for RemInst");
1492 NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].NonLocalDeps;
1494 // The cache is not valid for any specific block anymore.
1495 NonLocalPointerDeps[P].Pair = BBSkipFirstBlockPair();
1497 // Update any entries for RemInst to use the instruction after it.
1498 for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
1500 if (DI->getResult().getInst() != RemInst) continue;
1502 // Convert to a dirty entry for the subsequent instruction.
1503 DI->setResult(NewDirtyVal);
1505 if (Instruction *NewDirtyInst = NewDirtyVal.getInst())
1506 ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P));
1509 // Re-sort the NonLocalDepInfo. Changing the dirty entry to its
1510 // subsequent value may invalidate the sortedness.
1511 std::sort(NLPDI.begin(), NLPDI.end());
1514 ReverseNonLocalPtrDeps.erase(ReversePtrDepIt);
1516 while (!ReversePtrDepsToAdd.empty()) {
1517 ReverseNonLocalPtrDeps[ReversePtrDepsToAdd.back().first]
1518 .insert(ReversePtrDepsToAdd.back().second);
1519 ReversePtrDepsToAdd.pop_back();
1524 assert(!NonLocalDeps.count(RemInst) && "RemInst got reinserted?");
1525 AA->deleteValue(RemInst);
1526 DEBUG(verifyRemoved(RemInst));
1528 /// verifyRemoved - Verify that the specified instruction does not occur
1529 /// in our internal data structures.
1530 void MemoryDependenceAnalysis::verifyRemoved(Instruction *D) const {
1531 for (LocalDepMapType::const_iterator I = LocalDeps.begin(),
1532 E = LocalDeps.end(); I != E; ++I) {
1533 assert(I->first != D && "Inst occurs in data structures");
1534 assert(I->second.getInst() != D &&
1535 "Inst occurs in data structures");
1538 for (CachedNonLocalPointerInfo::const_iterator I =NonLocalPointerDeps.begin(),
1539 E = NonLocalPointerDeps.end(); I != E; ++I) {
1540 assert(I->first.getPointer() != D && "Inst occurs in NLPD map key");
1541 const NonLocalDepInfo &Val = I->second.NonLocalDeps;
1542 for (NonLocalDepInfo::const_iterator II = Val.begin(), E = Val.end();
1544 assert(II->getResult().getInst() != D && "Inst occurs as NLPD value");
1547 for (NonLocalDepMapType::const_iterator I = NonLocalDeps.begin(),
1548 E = NonLocalDeps.end(); I != E; ++I) {
1549 assert(I->first != D && "Inst occurs in data structures");
1550 const PerInstNLInfo &INLD = I->second;
1551 for (NonLocalDepInfo::const_iterator II = INLD.first.begin(),
1552 EE = INLD.first.end(); II != EE; ++II)
1553 assert(II->getResult().getInst() != D && "Inst occurs in data structures");
1556 for (ReverseDepMapType::const_iterator I = ReverseLocalDeps.begin(),
1557 E = ReverseLocalDeps.end(); I != E; ++I) {
1558 assert(I->first != D && "Inst occurs in data structures");
1559 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1560 EE = I->second.end(); II != EE; ++II)
1561 assert(*II != D && "Inst occurs in data structures");
1564 for (ReverseDepMapType::const_iterator I = ReverseNonLocalDeps.begin(),
1565 E = ReverseNonLocalDeps.end();
1567 assert(I->first != D && "Inst occurs in data structures");
1568 for (SmallPtrSet<Instruction*, 4>::const_iterator II = I->second.begin(),
1569 EE = I->second.end(); II != EE; ++II)
1570 assert(*II != D && "Inst occurs in data structures");
1573 for (ReverseNonLocalPtrDepTy::const_iterator
1574 I = ReverseNonLocalPtrDeps.begin(),
1575 E = ReverseNonLocalPtrDeps.end(); I != E; ++I) {
1576 assert(I->first != D && "Inst occurs in rev NLPD map");
1578 for (SmallPtrSet<ValueIsLoadPair, 4>::const_iterator II = I->second.begin(),
1579 E = I->second.end(); II != E; ++II)
1580 assert(*II != ValueIsLoadPair(D, false) &&
1581 *II != ValueIsLoadPair(D, true) &&
1582 "Inst occurs in ReverseNonLocalPtrDeps map");