1 //===- GlobalsModRef.cpp - Simple Mod/Ref Analysis for Globals ------------===//
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 simple pass provides alias and mod/ref information for global values
11 // that do not have their address taken, and keeps track of whether functions
12 // read or write memory (are "pure"). For this simple (but very common) case,
13 // we can provide pretty accurate and useful information.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Analysis/Passes.h"
18 #include "llvm/ADT/SCCIterator.h"
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include "llvm/ADT/Statistic.h"
21 #include "llvm/Analysis/AliasAnalysis.h"
22 #include "llvm/Analysis/CallGraph.h"
23 #include "llvm/Analysis/MemoryBuiltins.h"
24 #include "llvm/Analysis/ValueTracking.h"
25 #include "llvm/IR/Constants.h"
26 #include "llvm/IR/DerivedTypes.h"
27 #include "llvm/IR/InstIterator.h"
28 #include "llvm/IR/Instructions.h"
29 #include "llvm/IR/IntrinsicInst.h"
30 #include "llvm/IR/Module.h"
31 #include "llvm/Pass.h"
32 #include "llvm/Support/CommandLine.h"
36 #define DEBUG_TYPE "globalsmodref-aa"
38 STATISTIC(NumNonAddrTakenGlobalVars,
39 "Number of global vars without address taken");
40 STATISTIC(NumNonAddrTakenFunctions,"Number of functions without address taken");
41 STATISTIC(NumNoMemFunctions, "Number of functions that do not access memory");
42 STATISTIC(NumReadMemFunctions, "Number of functions that only read memory");
43 STATISTIC(NumIndirectGlobalVars, "Number of indirect global objects");
45 // An option to enable unsafe alias results from the GlobalsModRef analysis.
46 // When enabled, GlobalsModRef will provide no-alias results which in extremely
47 // rare cases may not be conservatively correct. In particular, in the face of
48 // transforms which cause assymetry between how effective GetUnderlyingObject
49 // is for two pointers, it may produce incorrect results.
51 // These unsafe results have been returned by GMR for many years without
52 // causing significant issues in the wild and so we provide a mechanism to
53 // re-enable them for users of LLVM that have a particular performance
54 // sensitivity and no known issues. The option also makes it easy to evaluate
55 // the performance impact of these results.
56 static cl::opt<bool> EnableUnsafeGlobalsModRefAliasResults(
57 "enable-unsafe-globalsmodref-alias-results", cl::init(false), cl::Hidden);
60 /// FunctionRecord - One instance of this structure is stored for every
61 /// function in the program. Later, the entries for these functions are
62 /// removed if the function is found to call an external function (in which
63 /// case we know nothing about it.
64 struct FunctionRecord {
65 /// GlobalInfo - Maintain mod/ref info for all of the globals without
66 /// addresses taken that are read or written (transitively) by this
68 std::map<const GlobalValue *, unsigned> GlobalInfo;
70 /// MayReadAnyGlobal - May read global variables, but it is not known which.
71 bool MayReadAnyGlobal;
73 unsigned getInfoForGlobal(const GlobalValue *GV) const {
74 unsigned Effect = MayReadAnyGlobal ? AliasAnalysis::Ref : 0;
75 std::map<const GlobalValue *, unsigned>::const_iterator I =
77 if (I != GlobalInfo.end())
82 /// FunctionEffect - Capture whether or not this function reads or writes to
83 /// ANY memory. If not, we can do a lot of aggressive analysis on it.
84 unsigned FunctionEffect;
86 FunctionRecord() : MayReadAnyGlobal(false), FunctionEffect(0) {}
89 /// GlobalsModRef - The actual analysis pass.
90 class GlobalsModRef : public ModulePass, public AliasAnalysis {
91 /// The globals that do not have their addresses taken.
92 SmallPtrSet<const GlobalValue *, 8> NonAddressTakenGlobals;
94 /// IndirectGlobals - The memory pointed to by this global is known to be
95 /// 'owned' by the global.
96 SmallPtrSet<const GlobalValue *, 8> IndirectGlobals;
98 /// AllocsForIndirectGlobals - If an instruction allocates memory for an
99 /// indirect global, this map indicates which one.
100 DenseMap<const Value *, const GlobalValue *> AllocsForIndirectGlobals;
102 /// FunctionInfo - For each function, keep track of what globals are
103 /// modified or read.
104 DenseMap<const Function *, FunctionRecord> FunctionInfo;
106 /// Handle to clear this analysis on deletion of values.
107 struct DeletionCallbackHandle final : CallbackVH {
109 std::list<DeletionCallbackHandle>::iterator I;
111 DeletionCallbackHandle(GlobalsModRef &GMR, Value *V)
112 : CallbackVH(V), GMR(GMR) {}
114 void deleted() override {
115 Value *V = getValPtr();
116 if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
117 if (GMR.NonAddressTakenGlobals.erase(GV)) {
118 // This global might be an indirect global. If so, remove it and
120 // any AllocRelatedValues for it.
121 if (GMR.IndirectGlobals.erase(GV)) {
122 // Remove any entries in AllocsForIndirectGlobals for this global.
123 for (auto I = GMR.AllocsForIndirectGlobals.begin(),
124 E = GMR.AllocsForIndirectGlobals.end();
127 GMR.AllocsForIndirectGlobals.erase(I);
132 // If this is an allocation related to an indirect global, remove it.
133 GMR.AllocsForIndirectGlobals.erase(V);
135 // And clear out the handle.
137 GMR.Handles.erase(I);
138 // This object is now destroyed!
142 /// List of callbacks for globals being tracked by this analysis. Note that
143 /// these objects are quite large, but we only anticipate having one per
144 /// global tracked by this analysis. There are numerous optimizations we
145 /// could perform to the memory utilization here if this becomes a problem.
146 std::list<DeletionCallbackHandle> Handles;
150 GlobalsModRef() : ModulePass(ID) {
151 initializeGlobalsModRefPass(*PassRegistry::getPassRegistry());
154 bool runOnModule(Module &M) override {
155 InitializeAliasAnalysis(this, &M.getDataLayout());
157 // Find non-addr taken globals.
161 AnalyzeCallGraph(getAnalysis<CallGraphWrapperPass>().getCallGraph(), M);
165 void getAnalysisUsage(AnalysisUsage &AU) const override {
166 AliasAnalysis::getAnalysisUsage(AU);
167 AU.addRequired<CallGraphWrapperPass>();
168 AU.setPreservesAll(); // Does not transform code
171 //------------------------------------------------
172 // Implement the AliasAnalysis API
174 AliasResult alias(const MemoryLocation &LocA,
175 const MemoryLocation &LocB) override;
176 ModRefResult getModRefInfo(ImmutableCallSite CS,
177 const MemoryLocation &Loc) override;
178 ModRefResult getModRefInfo(ImmutableCallSite CS1,
179 ImmutableCallSite CS2) override {
180 return AliasAnalysis::getModRefInfo(CS1, CS2);
183 /// getModRefBehavior - Return the behavior of the specified function if
184 /// called from the specified call site. The call site may be null in which
185 /// case the most generic behavior of this function should be returned.
186 ModRefBehavior getModRefBehavior(const Function *F) override {
187 ModRefBehavior Min = UnknownModRefBehavior;
189 if (FunctionRecord *FR = getFunctionInfo(F)) {
190 if (FR->FunctionEffect == 0)
191 Min = DoesNotAccessMemory;
192 else if ((FR->FunctionEffect & Mod) == 0)
193 Min = OnlyReadsMemory;
196 return ModRefBehavior(AliasAnalysis::getModRefBehavior(F) & Min);
199 /// getModRefBehavior - Return the behavior of the specified function if
200 /// called from the specified call site. The call site may be null in which
201 /// case the most generic behavior of this function should be returned.
202 ModRefBehavior getModRefBehavior(ImmutableCallSite CS) override {
203 ModRefBehavior Min = UnknownModRefBehavior;
205 if (const Function *F = CS.getCalledFunction())
206 if (FunctionRecord *FR = getFunctionInfo(F)) {
207 if (FR->FunctionEffect == 0)
208 Min = DoesNotAccessMemory;
209 else if ((FR->FunctionEffect & Mod) == 0)
210 Min = OnlyReadsMemory;
213 return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
216 /// getAdjustedAnalysisPointer - This method is used when a pass implements
217 /// an analysis interface through multiple inheritance. If needed, it
218 /// should override this to adjust the this pointer as needed for the
219 /// specified pass info.
220 void *getAdjustedAnalysisPointer(AnalysisID PI) override {
221 if (PI == &AliasAnalysis::ID)
222 return (AliasAnalysis *)this;
227 /// getFunctionInfo - Return the function info for the function, or null if
228 /// we don't have anything useful to say about it.
229 FunctionRecord *getFunctionInfo(const Function *F) {
230 auto I = FunctionInfo.find(F);
231 if (I != FunctionInfo.end())
236 void AnalyzeGlobals(Module &M);
237 void AnalyzeCallGraph(CallGraph &CG, Module &M);
238 bool AnalyzeUsesOfPointer(Value *V,
239 SmallPtrSetImpl<Function *> *Readers = nullptr,
240 SmallPtrSetImpl<Function *> *Writers = nullptr,
241 GlobalValue *OkayStoreDest = nullptr);
242 bool AnalyzeIndirectGlobalMemory(GlobalValue *GV);
246 char GlobalsModRef::ID = 0;
247 INITIALIZE_AG_PASS_BEGIN(GlobalsModRef, AliasAnalysis, "globalsmodref-aa",
248 "Simple mod/ref analysis for globals", false, true,
250 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
251 INITIALIZE_AG_PASS_END(GlobalsModRef, AliasAnalysis, "globalsmodref-aa",
252 "Simple mod/ref analysis for globals", false, true,
255 Pass *llvm::createGlobalsModRefPass() { return new GlobalsModRef(); }
257 /// AnalyzeGlobals - Scan through the users of all of the internal
258 /// GlobalValue's in the program. If none of them have their "address taken"
259 /// (really, their address passed to something nontrivial), record this fact,
260 /// and record the functions that they are used directly in.
261 void GlobalsModRef::AnalyzeGlobals(Module &M) {
262 for (Function &F : M)
263 if (F.hasLocalLinkage())
264 if (!AnalyzeUsesOfPointer(&F)) {
265 // Remember that we are tracking this global.
266 NonAddressTakenGlobals.insert(&F);
267 Handles.emplace_front(*this, &F);
268 Handles.front().I = Handles.begin();
269 ++NumNonAddrTakenFunctions;
272 SmallPtrSet<Function *, 64> Readers, Writers;
273 for (GlobalVariable &GV : M.globals())
274 if (GV.hasLocalLinkage()) {
275 if (!AnalyzeUsesOfPointer(&GV, &Readers,
276 GV.isConstant() ? nullptr : &Writers)) {
277 // Remember that we are tracking this global, and the mod/ref fns
278 NonAddressTakenGlobals.insert(&GV);
279 Handles.emplace_front(*this, &GV);
280 Handles.front().I = Handles.begin();
282 for (Function *Reader : Readers)
283 FunctionInfo[Reader].GlobalInfo[&GV] |= Ref;
285 if (!GV.isConstant()) // No need to keep track of writers to constants
286 for (Function *Writer : Writers)
287 FunctionInfo[Writer].GlobalInfo[&GV] |= Mod;
288 ++NumNonAddrTakenGlobalVars;
290 // If this global holds a pointer type, see if it is an indirect global.
291 if (GV.getType()->getElementType()->isPointerTy() &&
292 AnalyzeIndirectGlobalMemory(&GV))
293 ++NumIndirectGlobalVars;
300 /// AnalyzeUsesOfPointer - Look at all of the users of the specified pointer.
301 /// If this is used by anything complex (i.e., the address escapes), return
302 /// true. Also, while we are at it, keep track of those functions that read and
303 /// write to the value.
305 /// If OkayStoreDest is non-null, stores into this global are allowed.
306 bool GlobalsModRef::AnalyzeUsesOfPointer(Value *V,
307 SmallPtrSetImpl<Function *> *Readers,
308 SmallPtrSetImpl<Function *> *Writers,
309 GlobalValue *OkayStoreDest) {
310 if (!V->getType()->isPointerTy())
313 for (Use &U : V->uses()) {
314 User *I = U.getUser();
315 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
317 Readers->insert(LI->getParent()->getParent());
318 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
319 if (V == SI->getOperand(1)) {
321 Writers->insert(SI->getParent()->getParent());
322 } else if (SI->getOperand(1) != OkayStoreDest) {
323 return true; // Storing the pointer
325 } else if (Operator::getOpcode(I) == Instruction::GetElementPtr) {
326 if (AnalyzeUsesOfPointer(I, Readers, Writers))
328 } else if (Operator::getOpcode(I) == Instruction::BitCast) {
329 if (AnalyzeUsesOfPointer(I, Readers, Writers, OkayStoreDest))
331 } else if (auto CS = CallSite(I)) {
332 // Make sure that this is just the function being called, not that it is
333 // passing into the function.
334 if (!CS.isCallee(&U)) {
335 // Detect calls to free.
336 if (isFreeCall(I, TLI)) {
338 Writers->insert(CS->getParent()->getParent());
340 return true; // Argument of an unknown call.
343 } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) {
344 if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
345 return true; // Allow comparison against null.
354 /// AnalyzeIndirectGlobalMemory - We found an non-address-taken global variable
355 /// which holds a pointer type. See if the global always points to non-aliased
356 /// heap memory: that is, all initializers of the globals are allocations, and
357 /// those allocations have no use other than initialization of the global.
358 /// Further, all loads out of GV must directly use the memory, not store the
359 /// pointer somewhere. If this is true, we consider the memory pointed to by
360 /// GV to be owned by GV and can disambiguate other pointers from it.
361 bool GlobalsModRef::AnalyzeIndirectGlobalMemory(GlobalValue *GV) {
362 // Keep track of values related to the allocation of the memory, f.e. the
363 // value produced by the malloc call and any casts.
364 std::vector<Value *> AllocRelatedValues;
366 // Walk the user list of the global. If we find anything other than a direct
367 // load or store, bail out.
368 for (User *U : GV->users()) {
369 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
370 // The pointer loaded from the global can only be used in simple ways:
371 // we allow addressing of it and loading storing to it. We do *not* allow
372 // storing the loaded pointer somewhere else or passing to a function.
373 if (AnalyzeUsesOfPointer(LI))
374 return false; // Loaded pointer escapes.
375 // TODO: Could try some IP mod/ref of the loaded pointer.
376 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
377 // Storing the global itself.
378 if (SI->getOperand(0) == GV)
381 // If storing the null pointer, ignore it.
382 if (isa<ConstantPointerNull>(SI->getOperand(0)))
385 // Check the value being stored.
386 Value *Ptr = GetUnderlyingObject(SI->getOperand(0),
387 GV->getParent()->getDataLayout());
389 if (!isAllocLikeFn(Ptr, TLI))
390 return false; // Too hard to analyze.
392 // Analyze all uses of the allocation. If any of them are used in a
393 // non-simple way (e.g. stored to another global) bail out.
394 if (AnalyzeUsesOfPointer(Ptr, /*Readers*/ nullptr, /*Writers*/ nullptr,
396 return false; // Loaded pointer escapes.
398 // Remember that this allocation is related to the indirect global.
399 AllocRelatedValues.push_back(Ptr);
401 // Something complex, bail out.
406 // Okay, this is an indirect global. Remember all of the allocations for
407 // this global in AllocsForIndirectGlobals.
408 while (!AllocRelatedValues.empty()) {
409 AllocsForIndirectGlobals[AllocRelatedValues.back()] = GV;
410 Handles.emplace_front(*this, AllocRelatedValues.back());
411 Handles.front().I = Handles.begin();
412 AllocRelatedValues.pop_back();
414 IndirectGlobals.insert(GV);
415 Handles.emplace_front(*this, GV);
416 Handles.front().I = Handles.begin();
420 /// AnalyzeCallGraph - At this point, we know the functions where globals are
421 /// immediately stored to and read from. Propagate this information up the call
422 /// graph to all callers and compute the mod/ref info for all memory for each
424 void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
425 // We do a bottom-up SCC traversal of the call graph. In other words, we
426 // visit all callees before callers (leaf-first).
427 for (scc_iterator<CallGraph *> I = scc_begin(&CG); !I.isAtEnd(); ++I) {
428 const std::vector<CallGraphNode *> &SCC = *I;
429 assert(!SCC.empty() && "SCC with no functions?");
431 if (!SCC[0]->getFunction()) {
432 // Calls externally - can't say anything useful. Remove any existing
433 // function records (may have been created when scanning globals).
434 for (auto *Node : SCC)
435 FunctionInfo.erase(Node->getFunction());
439 FunctionRecord &FR = FunctionInfo[SCC[0]->getFunction()];
441 bool KnowNothing = false;
442 unsigned FunctionEffect = 0;
444 // Collect the mod/ref properties due to called functions. We only compute
446 for (unsigned i = 0, e = SCC.size(); i != e && !KnowNothing; ++i) {
447 Function *F = SCC[i]->getFunction();
453 if (F->isDeclaration()) {
454 // Try to get mod/ref behaviour from function attributes.
455 if (F->doesNotAccessMemory()) {
456 // Can't do better than that!
457 } else if (F->onlyReadsMemory()) {
458 FunctionEffect |= Ref;
459 if (!F->isIntrinsic())
460 // This function might call back into the module and read a global -
461 // consider every global as possibly being read by this function.
462 FR.MayReadAnyGlobal = true;
464 FunctionEffect |= ModRef;
465 // Can't say anything useful unless it's an intrinsic - they don't
466 // read or write global variables of the kind considered here.
467 KnowNothing = !F->isIntrinsic();
472 for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end();
473 CI != E && !KnowNothing; ++CI)
474 if (Function *Callee = CI->second->getFunction()) {
475 if (FunctionRecord *CalleeFR = getFunctionInfo(Callee)) {
476 // Propagate function effect up.
477 FunctionEffect |= CalleeFR->FunctionEffect;
479 // Incorporate callee's effects on globals into our info.
480 for (const auto &G : CalleeFR->GlobalInfo)
481 FR.GlobalInfo[G.first] |= G.second;
482 FR.MayReadAnyGlobal |= CalleeFR->MayReadAnyGlobal;
484 // Can't say anything about it. However, if it is inside our SCC,
485 // then nothing needs to be done.
486 CallGraphNode *CalleeNode = CG[Callee];
487 if (std::find(SCC.begin(), SCC.end(), CalleeNode) == SCC.end())
495 // If we can't say anything useful about this SCC, remove all SCC functions
496 // from the FunctionInfo map.
498 for (auto *Node : SCC)
499 FunctionInfo.erase(Node->getFunction());
503 // Scan the function bodies for explicit loads or stores.
504 for (auto *Node : SCC) {
505 if (FunctionEffect == ModRef)
506 break; // The mod/ref lattice saturates here.
507 for (Instruction &I : inst_range(Node->getFunction())) {
508 if (FunctionEffect == ModRef)
509 break; // The mod/ref lattice saturates here.
511 // We handle calls specially because the graph-relevant aspects are
513 if (auto CS = CallSite(&I)) {
514 if (isAllocationFn(&I, TLI) || isFreeCall(&I, TLI)) {
515 // FIXME: It is completely unclear why this is necessary and not
516 // handled by the above graph code.
517 FunctionEffect |= ModRef;
518 } else if (Function *Callee = CS.getCalledFunction()) {
519 // The callgraph doesn't include intrinsic calls.
520 if (Callee->isIntrinsic()) {
521 ModRefBehavior Behaviour =
522 AliasAnalysis::getModRefBehavior(Callee);
523 FunctionEffect |= (Behaviour & ModRef);
529 // All non-call instructions we use the primary predicates for whether
530 // thay read or write memory.
531 if (I.mayReadFromMemory())
532 FunctionEffect |= Ref;
533 if (I.mayWriteToMemory())
534 FunctionEffect |= Mod;
538 if ((FunctionEffect & Mod) == 0)
539 ++NumReadMemFunctions;
540 if (FunctionEffect == 0)
542 FR.FunctionEffect = FunctionEffect;
544 // Finally, now that we know the full effect on this SCC, clone the
545 // information to each function in the SCC.
546 for (unsigned i = 1, e = SCC.size(); i != e; ++i)
547 FunctionInfo[SCC[i]->getFunction()] = FR;
551 /// alias - If one of the pointers is to a global that we are tracking, and the
552 /// other is some random pointer, we know there cannot be an alias, because the
553 /// address of the global isn't taken.
554 AliasResult GlobalsModRef::alias(const MemoryLocation &LocA,
555 const MemoryLocation &LocB) {
556 // Get the base object these pointers point to.
557 const Value *UV1 = GetUnderlyingObject(LocA.Ptr, *DL);
558 const Value *UV2 = GetUnderlyingObject(LocB.Ptr, *DL);
560 // If either of the underlying values is a global, they may be non-addr-taken
561 // globals, which we can answer queries about.
562 const GlobalValue *GV1 = dyn_cast<GlobalValue>(UV1);
563 const GlobalValue *GV2 = dyn_cast<GlobalValue>(UV2);
565 // If the global's address is taken, pretend we don't know it's a pointer to
567 if (GV1 && !NonAddressTakenGlobals.count(GV1))
569 if (GV2 && !NonAddressTakenGlobals.count(GV2))
572 // If the two pointers are derived from two different non-addr-taken
573 // globals we know these can't alias.
574 if (GV1 && GV2 && GV1 != GV2)
577 // If one is and the other isn't, it isn't strictly safe but we can fake
578 // this result if necessary for performance. This does not appear to be
579 // a common problem in practice.
580 if (EnableUnsafeGlobalsModRefAliasResults)
581 if ((GV1 || GV2) && GV1 != GV2)
584 // Otherwise if they are both derived from the same addr-taken global, we
585 // can't know the two accesses don't overlap.
588 // These pointers may be based on the memory owned by an indirect global. If
589 // so, we may be able to handle this. First check to see if the base pointer
590 // is a direct load from an indirect global.
592 if (const LoadInst *LI = dyn_cast<LoadInst>(UV1))
593 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0)))
594 if (IndirectGlobals.count(GV))
596 if (const LoadInst *LI = dyn_cast<LoadInst>(UV2))
597 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0)))
598 if (IndirectGlobals.count(GV))
601 // These pointers may also be from an allocation for the indirect global. If
602 // so, also handle them.
604 GV1 = AllocsForIndirectGlobals.lookup(UV1);
606 GV2 = AllocsForIndirectGlobals.lookup(UV2);
608 // Now that we know whether the two pointers are related to indirect globals,
609 // use this to disambiguate the pointers. If the pointers are based on
610 // different indirect globals they cannot alias.
611 if (GV1 && GV2 && GV1 != GV2)
614 // If one is based on an indirect global and the other isn't, it isn't
615 // strictly safe but we can fake this result if necessary for performance.
616 // This does not appear to be a common problem in practice.
617 if (EnableUnsafeGlobalsModRefAliasResults)
618 if ((GV1 || GV2) && GV1 != GV2)
621 return AliasAnalysis::alias(LocA, LocB);
624 AliasAnalysis::ModRefResult
625 GlobalsModRef::getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc) {
626 unsigned Known = ModRef;
628 // If we are asking for mod/ref info of a direct call with a pointer to a
629 // global we are tracking, return information if we have it.
630 const DataLayout &DL = CS.getCaller()->getParent()->getDataLayout();
631 if (const GlobalValue *GV =
632 dyn_cast<GlobalValue>(GetUnderlyingObject(Loc.Ptr, DL)))
633 if (GV->hasLocalLinkage())
634 if (const Function *F = CS.getCalledFunction())
635 if (NonAddressTakenGlobals.count(GV))
636 if (const FunctionRecord *FR = getFunctionInfo(F))
637 Known = FR->getInfoForGlobal(GV);
639 if (Known == NoModRef)
640 return NoModRef; // No need to query other mod/ref analyses
641 return ModRefResult(Known & AliasAnalysis::getModRefInfo(CS, Loc));