LLVM  6.0.0svn
GlobalsModRef.cpp
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1 //===- GlobalsModRef.cpp - Simple Mod/Ref Analysis for Globals ------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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.
14 //
15 //===----------------------------------------------------------------------===//
16 
18 #include "llvm/ADT/SCCIterator.h"
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include "llvm/ADT/Statistic.h"
24 #include "llvm/IR/DerivedTypes.h"
25 #include "llvm/IR/InstIterator.h"
26 #include "llvm/IR/Instructions.h"
27 #include "llvm/IR/IntrinsicInst.h"
28 #include "llvm/IR/Module.h"
29 #include "llvm/Pass.h"
31 using namespace llvm;
32 
33 #define DEBUG_TYPE "globalsmodref-aa"
34 
35 STATISTIC(NumNonAddrTakenGlobalVars,
36  "Number of global vars without address taken");
37 STATISTIC(NumNonAddrTakenFunctions,"Number of functions without address taken");
38 STATISTIC(NumNoMemFunctions, "Number of functions that do not access memory");
39 STATISTIC(NumReadMemFunctions, "Number of functions that only read memory");
40 STATISTIC(NumIndirectGlobalVars, "Number of indirect global objects");
41 
42 // An option to enable unsafe alias results from the GlobalsModRef analysis.
43 // When enabled, GlobalsModRef will provide no-alias results which in extremely
44 // rare cases may not be conservatively correct. In particular, in the face of
45 // transforms which cause assymetry between how effective GetUnderlyingObject
46 // is for two pointers, it may produce incorrect results.
47 //
48 // These unsafe results have been returned by GMR for many years without
49 // causing significant issues in the wild and so we provide a mechanism to
50 // re-enable them for users of LLVM that have a particular performance
51 // sensitivity and no known issues. The option also makes it easy to evaluate
52 // the performance impact of these results.
54  "enable-unsafe-globalsmodref-alias-results", cl::init(false), cl::Hidden);
55 
56 /// The mod/ref information collected for a particular function.
57 ///
58 /// We collect information about mod/ref behavior of a function here, both in
59 /// general and as pertains to specific globals. We only have this detailed
60 /// information when we know *something* useful about the behavior. If we
61 /// saturate to fully general mod/ref, we remove the info for the function.
64 
65  /// Build a wrapper struct that has 8-byte alignment. All heap allocations
66  /// should provide this much alignment at least, but this makes it clear we
67  /// specifically rely on this amount of alignment.
68  struct LLVM_ALIGNAS(8) AlignedMap {
69  AlignedMap() {}
70  AlignedMap(const AlignedMap &Arg) : Map(Arg.Map) {}
71  GlobalInfoMapType Map;
72  };
73 
74  /// Pointer traits for our aligned map.
75  struct AlignedMapPointerTraits {
76  static inline void *getAsVoidPointer(AlignedMap *P) { return P; }
77  static inline AlignedMap *getFromVoidPointer(void *P) {
78  return (AlignedMap *)P;
79  }
80  enum { NumLowBitsAvailable = 3 };
81  static_assert(alignof(AlignedMap) >= (1 << NumLowBitsAvailable),
82  "AlignedMap insufficiently aligned to have enough low bits.");
83  };
84 
85  /// The bit that flags that this function may read any global. This is
86  /// chosen to mix together with ModRefInfo bits.
87  enum { MayReadAnyGlobal = 4 };
88 
89  /// Checks to document the invariants of the bit packing here.
90  static_assert((MayReadAnyGlobal & MRI_ModRef) == 0,
91  "ModRef and the MayReadAnyGlobal flag bits overlap.");
92  static_assert(((MayReadAnyGlobal | MRI_ModRef) >>
93  AlignedMapPointerTraits::NumLowBitsAvailable) == 0,
94  "Insufficient low bits to store our flag and ModRef info.");
95 
96 public:
97  FunctionInfo() : Info() {}
99  delete Info.getPointer();
100  }
101  // Spell out the copy ond move constructors and assignment operators to get
102  // deep copy semantics and correct move semantics in the face of the
103  // pointer-int pair.
105  : Info(nullptr, Arg.Info.getInt()) {
106  if (const auto *ArgPtr = Arg.Info.getPointer())
107  Info.setPointer(new AlignedMap(*ArgPtr));
108  }
110  : Info(Arg.Info.getPointer(), Arg.Info.getInt()) {
111  Arg.Info.setPointerAndInt(nullptr, 0);
112  }
114  delete Info.getPointer();
115  Info.setPointerAndInt(nullptr, RHS.Info.getInt());
116  if (const auto *RHSPtr = RHS.Info.getPointer())
117  Info.setPointer(new AlignedMap(*RHSPtr));
118  return *this;
119  }
121  delete Info.getPointer();
122  Info.setPointerAndInt(RHS.Info.getPointer(), RHS.Info.getInt());
123  RHS.Info.setPointerAndInt(nullptr, 0);
124  return *this;
125  }
126 
127  /// Returns the \c ModRefInfo info for this function.
129  return ModRefInfo(Info.getInt() & MRI_ModRef);
130  }
131 
132  /// Adds new \c ModRefInfo for this function to its state.
133  void addModRefInfo(ModRefInfo NewMRI) {
134  Info.setInt(Info.getInt() | NewMRI);
135  }
136 
137  /// Returns whether this function may read any global variable, and we don't
138  /// know which global.
139  bool mayReadAnyGlobal() const { return Info.getInt() & MayReadAnyGlobal; }
140 
141  /// Sets this function as potentially reading from any global.
142  void setMayReadAnyGlobal() { Info.setInt(Info.getInt() | MayReadAnyGlobal); }
143 
144  /// Returns the \c ModRefInfo info for this function w.r.t. a particular
145  /// global, which may be more precise than the general information above.
148  if (AlignedMap *P = Info.getPointer()) {
149  auto I = P->Map.find(&GV);
150  if (I != P->Map.end())
151  GlobalMRI = ModRefInfo(GlobalMRI | I->second);
152  }
153  return GlobalMRI;
154  }
155 
156  /// Add mod/ref info from another function into ours, saturating towards
157  /// MRI_ModRef.
158  void addFunctionInfo(const FunctionInfo &FI) {
160 
161  if (FI.mayReadAnyGlobal())
163 
164  if (AlignedMap *P = FI.Info.getPointer())
165  for (const auto &G : P->Map)
166  addModRefInfoForGlobal(*G.first, G.second);
167  }
168 
170  AlignedMap *P = Info.getPointer();
171  if (!P) {
172  P = new AlignedMap();
173  Info.setPointer(P);
174  }
175  auto &GlobalMRI = P->Map[&GV];
176  GlobalMRI = ModRefInfo(GlobalMRI | NewMRI);
177  }
178 
179  /// Clear a global's ModRef info. Should be used when a global is being
180  /// deleted.
182  if (AlignedMap *P = Info.getPointer())
183  P->Map.erase(&GV);
184  }
185 
186 private:
187  /// All of the information is encoded into a single pointer, with a three bit
188  /// integer in the low three bits. The high bit provides a flag for when this
189  /// function may read any global. The low two bits are the ModRefInfo. And
190  /// the pointer, when non-null, points to a map from GlobalValue to
191  /// ModRefInfo specific to that GlobalValue.
193 };
194 
195 void GlobalsAAResult::DeletionCallbackHandle::deleted() {
196  Value *V = getValPtr();
197  if (auto *F = dyn_cast<Function>(V))
198  GAR->FunctionInfos.erase(F);
199 
200  if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
201  if (GAR->NonAddressTakenGlobals.erase(GV)) {
202  // This global might be an indirect global. If so, remove it and
203  // remove any AllocRelatedValues for it.
204  if (GAR->IndirectGlobals.erase(GV)) {
205  // Remove any entries in AllocsForIndirectGlobals for this global.
206  for (auto I = GAR->AllocsForIndirectGlobals.begin(),
207  E = GAR->AllocsForIndirectGlobals.end();
208  I != E; ++I)
209  if (I->second == GV)
210  GAR->AllocsForIndirectGlobals.erase(I);
211  }
212 
213  // Scan the function info we have collected and remove this global
214  // from all of them.
215  for (auto &FIPair : GAR->FunctionInfos)
216  FIPair.second.eraseModRefInfoForGlobal(*GV);
217  }
218  }
219 
220  // If this is an allocation related to an indirect global, remove it.
221  GAR->AllocsForIndirectGlobals.erase(V);
222 
223  // And clear out the handle.
224  setValPtr(nullptr);
225  GAR->Handles.erase(I);
226  // This object is now destroyed!
227 }
228 
231 
232  if (FunctionInfo *FI = getFunctionInfo(F)) {
233  if (FI->getModRefInfo() == MRI_NoModRef)
235  else if ((FI->getModRefInfo() & MRI_Mod) == 0)
236  Min = FMRB_OnlyReadsMemory;
237  }
238 
240 }
241 
245 
246  if (!CS.hasOperandBundles())
247  if (const Function *F = CS.getCalledFunction())
248  if (FunctionInfo *FI = getFunctionInfo(F)) {
249  if (FI->getModRefInfo() == MRI_NoModRef)
251  else if ((FI->getModRefInfo() & MRI_Mod) == 0)
252  Min = FMRB_OnlyReadsMemory;
253  }
254 
256 }
257 
258 /// Returns the function info for the function, or null if we don't have
259 /// anything useful to say about it.
261 GlobalsAAResult::getFunctionInfo(const Function *F) {
262  auto I = FunctionInfos.find(F);
263  if (I != FunctionInfos.end())
264  return &I->second;
265  return nullptr;
266 }
267 
268 /// AnalyzeGlobals - Scan through the users of all of the internal
269 /// GlobalValue's in the program. If none of them have their "address taken"
270 /// (really, their address passed to something nontrivial), record this fact,
271 /// and record the functions that they are used directly in.
272 void GlobalsAAResult::AnalyzeGlobals(Module &M) {
273  SmallPtrSet<Function *, 32> TrackedFunctions;
274  for (Function &F : M)
275  if (F.hasLocalLinkage())
276  if (!AnalyzeUsesOfPointer(&F)) {
277  // Remember that we are tracking this global.
278  NonAddressTakenGlobals.insert(&F);
279  TrackedFunctions.insert(&F);
280  Handles.emplace_front(*this, &F);
281  Handles.front().I = Handles.begin();
282  ++NumNonAddrTakenFunctions;
283  }
284 
285  SmallPtrSet<Function *, 16> Readers, Writers;
286  for (GlobalVariable &GV : M.globals())
287  if (GV.hasLocalLinkage()) {
288  if (!AnalyzeUsesOfPointer(&GV, &Readers,
289  GV.isConstant() ? nullptr : &Writers)) {
290  // Remember that we are tracking this global, and the mod/ref fns
291  NonAddressTakenGlobals.insert(&GV);
292  Handles.emplace_front(*this, &GV);
293  Handles.front().I = Handles.begin();
294 
295  for (Function *Reader : Readers) {
296  if (TrackedFunctions.insert(Reader).second) {
297  Handles.emplace_front(*this, Reader);
298  Handles.front().I = Handles.begin();
299  }
300  FunctionInfos[Reader].addModRefInfoForGlobal(GV, MRI_Ref);
301  }
302 
303  if (!GV.isConstant()) // No need to keep track of writers to constants
304  for (Function *Writer : Writers) {
305  if (TrackedFunctions.insert(Writer).second) {
306  Handles.emplace_front(*this, Writer);
307  Handles.front().I = Handles.begin();
308  }
309  FunctionInfos[Writer].addModRefInfoForGlobal(GV, MRI_Mod);
310  }
311  ++NumNonAddrTakenGlobalVars;
312 
313  // If this global holds a pointer type, see if it is an indirect global.
314  if (GV.getValueType()->isPointerTy() &&
315  AnalyzeIndirectGlobalMemory(&GV))
316  ++NumIndirectGlobalVars;
317  }
318  Readers.clear();
319  Writers.clear();
320  }
321 }
322 
323 /// AnalyzeUsesOfPointer - Look at all of the users of the specified pointer.
324 /// If this is used by anything complex (i.e., the address escapes), return
325 /// true. Also, while we are at it, keep track of those functions that read and
326 /// write to the value.
327 ///
328 /// If OkayStoreDest is non-null, stores into this global are allowed.
329 bool GlobalsAAResult::AnalyzeUsesOfPointer(Value *V,
332  GlobalValue *OkayStoreDest) {
333  if (!V->getType()->isPointerTy())
334  return true;
335 
336  for (Use &U : V->uses()) {
337  User *I = U.getUser();
338  if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
339  if (Readers)
340  Readers->insert(LI->getParent()->getParent());
341  } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
342  if (V == SI->getOperand(1)) {
343  if (Writers)
344  Writers->insert(SI->getParent()->getParent());
345  } else if (SI->getOperand(1) != OkayStoreDest) {
346  return true; // Storing the pointer
347  }
348  } else if (Operator::getOpcode(I) == Instruction::GetElementPtr) {
349  if (AnalyzeUsesOfPointer(I, Readers, Writers))
350  return true;
351  } else if (Operator::getOpcode(I) == Instruction::BitCast) {
352  if (AnalyzeUsesOfPointer(I, Readers, Writers, OkayStoreDest))
353  return true;
354  } else if (auto CS = CallSite(I)) {
355  // Make sure that this is just the function being called, not that it is
356  // passing into the function.
357  if (CS.isDataOperand(&U)) {
358  // Detect calls to free.
359  if (CS.isArgOperand(&U) && isFreeCall(I, &TLI)) {
360  if (Writers)
361  Writers->insert(CS->getParent()->getParent());
362  } else {
363  return true; // Argument of an unknown call.
364  }
365  }
366  } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) {
367  if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
368  return true; // Allow comparison against null.
369  } else if (Constant *C = dyn_cast<Constant>(I)) {
370  // Ignore constants which don't have any live uses.
371  if (isa<GlobalValue>(C) || C->isConstantUsed())
372  return true;
373  } else {
374  return true;
375  }
376  }
377 
378  return false;
379 }
380 
381 /// AnalyzeIndirectGlobalMemory - We found an non-address-taken global variable
382 /// which holds a pointer type. See if the global always points to non-aliased
383 /// heap memory: that is, all initializers of the globals are allocations, and
384 /// those allocations have no use other than initialization of the global.
385 /// Further, all loads out of GV must directly use the memory, not store the
386 /// pointer somewhere. If this is true, we consider the memory pointed to by
387 /// GV to be owned by GV and can disambiguate other pointers from it.
388 bool GlobalsAAResult::AnalyzeIndirectGlobalMemory(GlobalVariable *GV) {
389  // Keep track of values related to the allocation of the memory, f.e. the
390  // value produced by the malloc call and any casts.
391  std::vector<Value *> AllocRelatedValues;
392 
393  // If the initializer is a valid pointer, bail.
394  if (Constant *C = GV->getInitializer())
395  if (!C->isNullValue())
396  return false;
397 
398  // Walk the user list of the global. If we find anything other than a direct
399  // load or store, bail out.
400  for (User *U : GV->users()) {
401  if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
402  // The pointer loaded from the global can only be used in simple ways:
403  // we allow addressing of it and loading storing to it. We do *not* allow
404  // storing the loaded pointer somewhere else or passing to a function.
405  if (AnalyzeUsesOfPointer(LI))
406  return false; // Loaded pointer escapes.
407  // TODO: Could try some IP mod/ref of the loaded pointer.
408  } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
409  // Storing the global itself.
410  if (SI->getOperand(0) == GV)
411  return false;
412 
413  // If storing the null pointer, ignore it.
414  if (isa<ConstantPointerNull>(SI->getOperand(0)))
415  continue;
416 
417  // Check the value being stored.
418  Value *Ptr = GetUnderlyingObject(SI->getOperand(0),
419  GV->getParent()->getDataLayout());
420 
421  if (!isAllocLikeFn(Ptr, &TLI))
422  return false; // Too hard to analyze.
423 
424  // Analyze all uses of the allocation. If any of them are used in a
425  // non-simple way (e.g. stored to another global) bail out.
426  if (AnalyzeUsesOfPointer(Ptr, /*Readers*/ nullptr, /*Writers*/ nullptr,
427  GV))
428  return false; // Loaded pointer escapes.
429 
430  // Remember that this allocation is related to the indirect global.
431  AllocRelatedValues.push_back(Ptr);
432  } else {
433  // Something complex, bail out.
434  return false;
435  }
436  }
437 
438  // Okay, this is an indirect global. Remember all of the allocations for
439  // this global in AllocsForIndirectGlobals.
440  while (!AllocRelatedValues.empty()) {
441  AllocsForIndirectGlobals[AllocRelatedValues.back()] = GV;
442  Handles.emplace_front(*this, AllocRelatedValues.back());
443  Handles.front().I = Handles.begin();
444  AllocRelatedValues.pop_back();
445  }
446  IndirectGlobals.insert(GV);
447  Handles.emplace_front(*this, GV);
448  Handles.front().I = Handles.begin();
449  return true;
450 }
451 
452 void GlobalsAAResult::CollectSCCMembership(CallGraph &CG) {
453  // We do a bottom-up SCC traversal of the call graph. In other words, we
454  // visit all callees before callers (leaf-first).
455  unsigned SCCID = 0;
456  for (scc_iterator<CallGraph *> I = scc_begin(&CG); !I.isAtEnd(); ++I) {
457  const std::vector<CallGraphNode *> &SCC = *I;
458  assert(!SCC.empty() && "SCC with no functions?");
459 
460  for (auto *CGN : SCC)
461  if (Function *F = CGN->getFunction())
462  FunctionToSCCMap[F] = SCCID;
463  ++SCCID;
464  }
465 }
466 
467 /// AnalyzeCallGraph - At this point, we know the functions where globals are
468 /// immediately stored to and read from. Propagate this information up the call
469 /// graph to all callers and compute the mod/ref info for all memory for each
470 /// function.
471 void GlobalsAAResult::AnalyzeCallGraph(CallGraph &CG, Module &M) {
472  // We do a bottom-up SCC traversal of the call graph. In other words, we
473  // visit all callees before callers (leaf-first).
474  for (scc_iterator<CallGraph *> I = scc_begin(&CG); !I.isAtEnd(); ++I) {
475  const std::vector<CallGraphNode *> &SCC = *I;
476  assert(!SCC.empty() && "SCC with no functions?");
477 
478  Function *F = SCC[0]->getFunction();
479 
480  if (!F || !F->isDefinitionExact()) {
481  // Calls externally or not exact - can't say anything useful. Remove any
482  // existing function records (may have been created when scanning
483  // globals).
484  for (auto *Node : SCC)
485  FunctionInfos.erase(Node->getFunction());
486  continue;
487  }
488 
489  FunctionInfo &FI = FunctionInfos[F];
490  bool KnowNothing = false;
491 
492  // Collect the mod/ref properties due to called functions. We only compute
493  // one mod-ref set.
494  for (unsigned i = 0, e = SCC.size(); i != e && !KnowNothing; ++i) {
495  if (!F) {
496  KnowNothing = true;
497  break;
498  }
499 
500  if (F->isDeclaration() || F->hasFnAttribute(Attribute::OptimizeNone)) {
501  // Try to get mod/ref behaviour from function attributes.
502  if (F->doesNotAccessMemory()) {
503  // Can't do better than that!
504  } else if (F->onlyReadsMemory()) {
506  if (!F->isIntrinsic() && !F->onlyAccessesArgMemory())
507  // This function might call back into the module and read a global -
508  // consider every global as possibly being read by this function.
509  FI.setMayReadAnyGlobal();
510  } else {
512  // Can't say anything useful unless it's an intrinsic - they don't
513  // read or write global variables of the kind considered here.
514  KnowNothing = !F->isIntrinsic();
515  }
516  continue;
517  }
518 
519  for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end();
520  CI != E && !KnowNothing; ++CI)
521  if (Function *Callee = CI->second->getFunction()) {
522  if (FunctionInfo *CalleeFI = getFunctionInfo(Callee)) {
523  // Propagate function effect up.
524  FI.addFunctionInfo(*CalleeFI);
525  } else {
526  // Can't say anything about it. However, if it is inside our SCC,
527  // then nothing needs to be done.
528  CallGraphNode *CalleeNode = CG[Callee];
529  if (!is_contained(SCC, CalleeNode))
530  KnowNothing = true;
531  }
532  } else {
533  KnowNothing = true;
534  }
535  }
536 
537  // If we can't say anything useful about this SCC, remove all SCC functions
538  // from the FunctionInfos map.
539  if (KnowNothing) {
540  for (auto *Node : SCC)
541  FunctionInfos.erase(Node->getFunction());
542  continue;
543  }
544 
545  // Scan the function bodies for explicit loads or stores.
546  for (auto *Node : SCC) {
547  if (FI.getModRefInfo() == MRI_ModRef)
548  break; // The mod/ref lattice saturates here.
549 
550  // Don't prove any properties based on the implementation of an optnone
551  // function. Function attributes were already used as a best approximation
552  // above.
553  if (Node->getFunction()->hasFnAttribute(Attribute::OptimizeNone))
554  continue;
555 
556  for (Instruction &I : instructions(Node->getFunction())) {
557  if (FI.getModRefInfo() == MRI_ModRef)
558  break; // The mod/ref lattice saturates here.
559 
560  // We handle calls specially because the graph-relevant aspects are
561  // handled above.
562  if (auto CS = CallSite(&I)) {
563  if (isAllocationFn(&I, &TLI) || isFreeCall(&I, &TLI)) {
564  // FIXME: It is completely unclear why this is necessary and not
565  // handled by the above graph code.
567  } else if (Function *Callee = CS.getCalledFunction()) {
568  // The callgraph doesn't include intrinsic calls.
569  if (Callee->isIntrinsic()) {
570  FunctionModRefBehavior Behaviour =
572  FI.addModRefInfo(ModRefInfo(Behaviour & MRI_ModRef));
573  }
574  }
575  continue;
576  }
577 
578  // All non-call instructions we use the primary predicates for whether
579  // thay read or write memory.
580  if (I.mayReadFromMemory())
582  if (I.mayWriteToMemory())
584  }
585  }
586 
587  if ((FI.getModRefInfo() & MRI_Mod) == 0)
588  ++NumReadMemFunctions;
589  if (FI.getModRefInfo() == MRI_NoModRef)
590  ++NumNoMemFunctions;
591 
592  // Finally, now that we know the full effect on this SCC, clone the
593  // information to each function in the SCC.
594  // FI is a reference into FunctionInfos, so copy it now so that it doesn't
595  // get invalidated if DenseMap decides to re-hash.
596  FunctionInfo CachedFI = FI;
597  for (unsigned i = 1, e = SCC.size(); i != e; ++i)
598  FunctionInfos[SCC[i]->getFunction()] = CachedFI;
599  }
600 }
601 
602 // GV is a non-escaping global. V is a pointer address that has been loaded from.
603 // If we can prove that V must escape, we can conclude that a load from V cannot
604 // alias GV.
606  const Value *V,
607  int &Depth,
608  const DataLayout &DL) {
611  Visited.insert(V);
612  Inputs.push_back(V);
613  do {
614  const Value *Input = Inputs.pop_back_val();
615 
616  if (isa<GlobalValue>(Input) || isa<Argument>(Input) || isa<CallInst>(Input) ||
617  isa<InvokeInst>(Input))
618  // Arguments to functions or returns from functions are inherently
619  // escaping, so we can immediately classify those as not aliasing any
620  // non-addr-taken globals.
621  //
622  // (Transitive) loads from a global are also safe - if this aliased
623  // another global, its address would escape, so no alias.
624  continue;
625 
626  // Recurse through a limited number of selects, loads and PHIs. This is an
627  // arbitrary depth of 4, lower numbers could be used to fix compile time
628  // issues if needed, but this is generally expected to be only be important
629  // for small depths.
630  if (++Depth > 4)
631  return false;
632 
633  if (auto *LI = dyn_cast<LoadInst>(Input)) {
634  Inputs.push_back(GetUnderlyingObject(LI->getPointerOperand(), DL));
635  continue;
636  }
637  if (auto *SI = dyn_cast<SelectInst>(Input)) {
638  const Value *LHS = GetUnderlyingObject(SI->getTrueValue(), DL);
639  const Value *RHS = GetUnderlyingObject(SI->getFalseValue(), DL);
640  if (Visited.insert(LHS).second)
641  Inputs.push_back(LHS);
642  if (Visited.insert(RHS).second)
643  Inputs.push_back(RHS);
644  continue;
645  }
646  if (auto *PN = dyn_cast<PHINode>(Input)) {
647  for (const Value *Op : PN->incoming_values()) {
648  Op = GetUnderlyingObject(Op, DL);
649  if (Visited.insert(Op).second)
650  Inputs.push_back(Op);
651  }
652  continue;
653  }
654 
655  return false;
656  } while (!Inputs.empty());
657 
658  // All inputs were known to be no-alias.
659  return true;
660 }
661 
662 // There are particular cases where we can conclude no-alias between
663 // a non-addr-taken global and some other underlying object. Specifically,
664 // a non-addr-taken global is known to not be escaped from any function. It is
665 // also incorrect for a transformation to introduce an escape of a global in
666 // a way that is observable when it was not there previously. One function
667 // being transformed to introduce an escape which could possibly be observed
668 // (via loading from a global or the return value for example) within another
669 // function is never safe. If the observation is made through non-atomic
670 // operations on different threads, it is a data-race and UB. If the
671 // observation is well defined, by being observed the transformation would have
672 // changed program behavior by introducing the observed escape, making it an
673 // invalid transform.
674 //
675 // This property does require that transformations which *temporarily* escape
676 // a global that was not previously escaped, prior to restoring it, cannot rely
677 // on the results of GMR::alias. This seems a reasonable restriction, although
678 // currently there is no way to enforce it. There is also no realistic
679 // optimization pass that would make this mistake. The closest example is
680 // a transformation pass which does reg2mem of SSA values but stores them into
681 // global variables temporarily before restoring the global variable's value.
682 // This could be useful to expose "benign" races for example. However, it seems
683 // reasonable to require that a pass which introduces escapes of global
684 // variables in this way to either not trust AA results while the escape is
685 // active, or to be forced to operate as a module pass that cannot co-exist
686 // with an alias analysis such as GMR.
687 bool GlobalsAAResult::isNonEscapingGlobalNoAlias(const GlobalValue *GV,
688  const Value *V) {
689  // In order to know that the underlying object cannot alias the
690  // non-addr-taken global, we must know that it would have to be an escape.
691  // Thus if the underlying object is a function argument, a load from
692  // a global, or the return of a function, it cannot alias. We can also
693  // recurse through PHI nodes and select nodes provided all of their inputs
694  // resolve to one of these known-escaping roots.
697  Visited.insert(V);
698  Inputs.push_back(V);
699  int Depth = 0;
700  do {
701  const Value *Input = Inputs.pop_back_val();
702 
703  if (auto *InputGV = dyn_cast<GlobalValue>(Input)) {
704  // If one input is the very global we're querying against, then we can't
705  // conclude no-alias.
706  if (InputGV == GV)
707  return false;
708 
709  // Distinct GlobalVariables never alias, unless overriden or zero-sized.
710  // FIXME: The condition can be refined, but be conservative for now.
711  auto *GVar = dyn_cast<GlobalVariable>(GV);
712  auto *InputGVar = dyn_cast<GlobalVariable>(InputGV);
713  if (GVar && InputGVar &&
714  !GVar->isDeclaration() && !InputGVar->isDeclaration() &&
715  !GVar->isInterposable() && !InputGVar->isInterposable()) {
716  Type *GVType = GVar->getInitializer()->getType();
717  Type *InputGVType = InputGVar->getInitializer()->getType();
718  if (GVType->isSized() && InputGVType->isSized() &&
719  (DL.getTypeAllocSize(GVType) > 0) &&
720  (DL.getTypeAllocSize(InputGVType) > 0))
721  continue;
722  }
723 
724  // Conservatively return false, even though we could be smarter
725  // (e.g. look through GlobalAliases).
726  return false;
727  }
728 
729  if (isa<Argument>(Input) || isa<CallInst>(Input) ||
730  isa<InvokeInst>(Input)) {
731  // Arguments to functions or returns from functions are inherently
732  // escaping, so we can immediately classify those as not aliasing any
733  // non-addr-taken globals.
734  continue;
735  }
736 
737  // Recurse through a limited number of selects, loads and PHIs. This is an
738  // arbitrary depth of 4, lower numbers could be used to fix compile time
739  // issues if needed, but this is generally expected to be only be important
740  // for small depths.
741  if (++Depth > 4)
742  return false;
743 
744  if (auto *LI = dyn_cast<LoadInst>(Input)) {
745  // A pointer loaded from a global would have been captured, and we know
746  // that the global is non-escaping, so no alias.
747  const Value *Ptr = GetUnderlyingObject(LI->getPointerOperand(), DL);
748  if (isNonEscapingGlobalNoAliasWithLoad(GV, Ptr, Depth, DL))
749  // The load does not alias with GV.
750  continue;
751  // Otherwise, a load could come from anywhere, so bail.
752  return false;
753  }
754  if (auto *SI = dyn_cast<SelectInst>(Input)) {
755  const Value *LHS = GetUnderlyingObject(SI->getTrueValue(), DL);
756  const Value *RHS = GetUnderlyingObject(SI->getFalseValue(), DL);
757  if (Visited.insert(LHS).second)
758  Inputs.push_back(LHS);
759  if (Visited.insert(RHS).second)
760  Inputs.push_back(RHS);
761  continue;
762  }
763  if (auto *PN = dyn_cast<PHINode>(Input)) {
764  for (const Value *Op : PN->incoming_values()) {
765  Op = GetUnderlyingObject(Op, DL);
766  if (Visited.insert(Op).second)
767  Inputs.push_back(Op);
768  }
769  continue;
770  }
771 
772  // FIXME: It would be good to handle other obvious no-alias cases here, but
773  // it isn't clear how to do so reasonbly without building a small version
774  // of BasicAA into this code. We could recurse into AAResultBase::alias
775  // here but that seems likely to go poorly as we're inside the
776  // implementation of such a query. Until then, just conservatievly retun
777  // false.
778  return false;
779  } while (!Inputs.empty());
780 
781  // If all the inputs to V were definitively no-alias, then V is no-alias.
782  return true;
783 }
784 
785 /// alias - If one of the pointers is to a global that we are tracking, and the
786 /// other is some random pointer, we know there cannot be an alias, because the
787 /// address of the global isn't taken.
789  const MemoryLocation &LocB) {
790  // Get the base object these pointers point to.
791  const Value *UV1 = GetUnderlyingObject(LocA.Ptr, DL);
792  const Value *UV2 = GetUnderlyingObject(LocB.Ptr, DL);
793 
794  // If either of the underlying values is a global, they may be non-addr-taken
795  // globals, which we can answer queries about.
796  const GlobalValue *GV1 = dyn_cast<GlobalValue>(UV1);
797  const GlobalValue *GV2 = dyn_cast<GlobalValue>(UV2);
798  if (GV1 || GV2) {
799  // If the global's address is taken, pretend we don't know it's a pointer to
800  // the global.
801  if (GV1 && !NonAddressTakenGlobals.count(GV1))
802  GV1 = nullptr;
803  if (GV2 && !NonAddressTakenGlobals.count(GV2))
804  GV2 = nullptr;
805 
806  // If the two pointers are derived from two different non-addr-taken
807  // globals we know these can't alias.
808  if (GV1 && GV2 && GV1 != GV2)
809  return NoAlias;
810 
811  // If one is and the other isn't, it isn't strictly safe but we can fake
812  // this result if necessary for performance. This does not appear to be
813  // a common problem in practice.
815  if ((GV1 || GV2) && GV1 != GV2)
816  return NoAlias;
817 
818  // Check for a special case where a non-escaping global can be used to
819  // conclude no-alias.
820  if ((GV1 || GV2) && GV1 != GV2) {
821  const GlobalValue *GV = GV1 ? GV1 : GV2;
822  const Value *UV = GV1 ? UV2 : UV1;
823  if (isNonEscapingGlobalNoAlias(GV, UV))
824  return NoAlias;
825  }
826 
827  // Otherwise if they are both derived from the same addr-taken global, we
828  // can't know the two accesses don't overlap.
829  }
830 
831  // These pointers may be based on the memory owned by an indirect global. If
832  // so, we may be able to handle this. First check to see if the base pointer
833  // is a direct load from an indirect global.
834  GV1 = GV2 = nullptr;
835  if (const LoadInst *LI = dyn_cast<LoadInst>(UV1))
836  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0)))
837  if (IndirectGlobals.count(GV))
838  GV1 = GV;
839  if (const LoadInst *LI = dyn_cast<LoadInst>(UV2))
840  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0)))
841  if (IndirectGlobals.count(GV))
842  GV2 = GV;
843 
844  // These pointers may also be from an allocation for the indirect global. If
845  // so, also handle them.
846  if (!GV1)
847  GV1 = AllocsForIndirectGlobals.lookup(UV1);
848  if (!GV2)
849  GV2 = AllocsForIndirectGlobals.lookup(UV2);
850 
851  // Now that we know whether the two pointers are related to indirect globals,
852  // use this to disambiguate the pointers. If the pointers are based on
853  // different indirect globals they cannot alias.
854  if (GV1 && GV2 && GV1 != GV2)
855  return NoAlias;
856 
857  // If one is based on an indirect global and the other isn't, it isn't
858  // strictly safe but we can fake this result if necessary for performance.
859  // This does not appear to be a common problem in practice.
861  if ((GV1 || GV2) && GV1 != GV2)
862  return NoAlias;
863 
864  return AAResultBase::alias(LocA, LocB);
865 }
866 
867 ModRefInfo GlobalsAAResult::getModRefInfoForArgument(ImmutableCallSite CS,
868  const GlobalValue *GV) {
869  if (CS.doesNotAccessMemory())
870  return MRI_NoModRef;
871  ModRefInfo ConservativeResult = CS.onlyReadsMemory() ? MRI_Ref : MRI_ModRef;
872 
873  // Iterate through all the arguments to the called function. If any argument
874  // is based on GV, return the conservative result.
875  for (auto &A : CS.args()) {
876  SmallVector<Value*, 4> Objects;
877  GetUnderlyingObjects(A, Objects, DL);
878 
879  // All objects must be identified.
880  if (!all_of(Objects, isIdentifiedObject) &&
881  // Try ::alias to see if all objects are known not to alias GV.
882  !all_of(Objects, [&](Value *V) {
883  return this->alias(MemoryLocation(V), MemoryLocation(GV)) == NoAlias;
884  }))
885  return ConservativeResult;
886 
887  if (is_contained(Objects, GV))
888  return ConservativeResult;
889  }
890 
891  // We identified all objects in the argument list, and none of them were GV.
892  return MRI_NoModRef;
893 }
894 
896  const MemoryLocation &Loc) {
897  unsigned Known = MRI_ModRef;
898 
899  // If we are asking for mod/ref info of a direct call with a pointer to a
900  // global we are tracking, return information if we have it.
901  if (const GlobalValue *GV =
902  dyn_cast<GlobalValue>(GetUnderlyingObject(Loc.Ptr, DL)))
903  if (GV->hasLocalLinkage())
904  if (const Function *F = CS.getCalledFunction())
905  if (NonAddressTakenGlobals.count(GV))
906  if (const FunctionInfo *FI = getFunctionInfo(F))
907  Known = FI->getModRefInfoForGlobal(*GV) |
908  getModRefInfoForArgument(CS, GV);
909 
910  if (Known == MRI_NoModRef)
911  return MRI_NoModRef; // No need to query other mod/ref analyses
912  return ModRefInfo(Known & AAResultBase::getModRefInfo(CS, Loc));
913 }
914 
915 GlobalsAAResult::GlobalsAAResult(const DataLayout &DL,
916  const TargetLibraryInfo &TLI)
917  : AAResultBase(), DL(DL), TLI(TLI) {}
918 
919 GlobalsAAResult::GlobalsAAResult(GlobalsAAResult &&Arg)
920  : AAResultBase(std::move(Arg)), DL(Arg.DL), TLI(Arg.TLI),
921  NonAddressTakenGlobals(std::move(Arg.NonAddressTakenGlobals)),
922  IndirectGlobals(std::move(Arg.IndirectGlobals)),
923  AllocsForIndirectGlobals(std::move(Arg.AllocsForIndirectGlobals)),
924  FunctionInfos(std::move(Arg.FunctionInfos)),
925  Handles(std::move(Arg.Handles)) {
926  // Update the parent for each DeletionCallbackHandle.
927  for (auto &H : Handles) {
928  assert(H.GAR == &Arg);
929  H.GAR = this;
930  }
931 }
932 
934 
935 /*static*/ GlobalsAAResult
937  CallGraph &CG) {
938  GlobalsAAResult Result(M.getDataLayout(), TLI);
939 
940  // Discover which functions aren't recursive, to feed into AnalyzeGlobals.
941  Result.CollectSCCMembership(CG);
942 
943  // Find non-addr taken globals.
944  Result.AnalyzeGlobals(M);
945 
946  // Propagate on CG.
947  Result.AnalyzeCallGraph(CG, M);
948 
949  return Result;
950 }
951 
952 AnalysisKey GlobalsAA::Key;
953 
958 }
959 
960 char GlobalsAAWrapperPass::ID = 0;
962  "Globals Alias Analysis", false, true)
966  "Globals Alias Analysis", false, true)
967 
969  return new GlobalsAAWrapperPass();
970 }
971 
974 }
975 
978  M, getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
979  getAnalysis<CallGraphWrapperPass>().getCallGraph())));
980  return false;
981 }
982 
984  Result.reset();
985  return false;
986 }
987 
989  AU.setPreservesAll();
992 }
Legacy wrapper pass to provide the GlobalsAAResult object.
uint64_t CallInst * C
bool isAllocationFn(const Value *V, const TargetLibraryInfo *TLI, bool LookThroughBitCast=false)
Tests if a value is a call or invoke to a library function that allocates or reallocates memory (eith...
This builds on the llvm/ADT/GraphTraits.h file to find the strongly connected components (SCCs) of a ...
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:109
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:244
bool doFinalization(Module &M) override
doFinalization - Virtual method overriden by subclasses to do any necessary clean up after all passes...
iterator_range< use_iterator > uses()
Definition: Value.h:356
bool hasLocalLinkage() const
Definition: GlobalValue.h:427
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
const_iterator begin(StringRef path, Style style=Style::native)
Get begin iterator over path.
Definition: Path.cpp:235
void addFunctionInfo(const FunctionInfo &FI)
Add mod/ref info from another function into ours, saturating towards MRI_ModRef.
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:687
void setMayReadAnyGlobal()
Sets this function as potentially reading from any global.
const Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
globals Globals Alias Analysis
PointerTy getPointer() const
static cl::opt< bool > EnableUnsafeGlobalsModRefAliasResults("enable-unsafe-globalsmodref-alias-results", cl::init(false), cl::Hidden)
FunctionInfo & operator=(const FunctionInfo &RHS)
ModRefInfo getModRefInfoForGlobal(const GlobalValue &GV) const
Returns the ModRefInfo info for this function w.r.t.
This is the interface for a simple mod/ref and alias analysis over globals.
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:63
bool isSized(SmallPtrSetImpl< Type *> *Visited=nullptr) const
Return true if it makes sense to take the size of this type.
Definition: Type.h:262
iterator_range< IterTy > args() const
Definition: CallSite.h:215
FunctionInfo & operator=(FunctionInfo &&RHS)
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:767
STATISTIC(NumFunctions, "Total number of functions")
The two locations do not alias at all.
Definition: AliasAnalysis.h:85
F(f)
An instruction for reading from memory.
Definition: Instructions.h:164
A node in the call graph for a module.
Definition: CallGraph.h:165
The mod/ref information collected for a particular function.
The access modifies the value stored in memory.
void addModRefInfoForGlobal(const GlobalValue &GV, ModRefInfo NewMRI)
const CallInst * isFreeCall(const Value *I, const TargetLibraryInfo *TLI)
isFreeCall - Returns non-null if the value is a call to the builtin free()
This indicates that the function could not be classified into one of the behaviors above...
A templated base class for SmallPtrSet which provides the typesafe interface that is common across al...
Definition: SmallPtrSet.h:344
bool onlyReadsMemory() const
Determine if the call does not access or only reads memory.
Definition: CallSite.h:454
AnalysisUsage & addRequired()
bool mayReadAnyGlobal() const
Returns whether this function may read any global variable, and we don&#39;t know which global...
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:51
Definition: BitVector.h:920
ModRefInfo
Flags indicating whether a memory access modifies or references memory.
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:361
static unsigned getInt(StringRef R)
Get an unsigned integer, including error checks.
Definition: DataLayout.cpp:209
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
The access references the value stored in memory.
bool isIdentifiedObject(const Value *V)
Return true if this pointer refers to a distinct and identifiable object.
A CRTP-driven "mixin" base class to help implement the function alias analysis results concept...
scc_iterator< T > scc_begin(const T &G)
Construct the begin iterator for a deduced graph type T.
Definition: SCCIterator.h:226
static GlobalsAAResult analyzeModule(Module &M, const TargetLibraryInfo &TLI, CallGraph &CG)
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:245
bool runOnModule(Module &M) override
runOnModule - Virtual method overriden by subclasses to process the module being operated on...
IntType getInt() const
GlobalsAAResult run(Module &M, ModuleAnalysisManager &AM)
FunctionModRefBehavior
Summary of how a function affects memory in the program.
An instruction for storing to memory.
Definition: Instructions.h:306
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB)
FunctionInfo(const FunctionInfo &Arg)
ModRefInfo getModRefInfo() const
Returns the ModRefInfo info for this function.
amdgpu Simplify well known AMD library false Value * Callee
FunctionModRefBehavior getModRefBehavior(ImmutableCallSite CS)
The access neither references nor modifies the value stored in memory.
#define P(N)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:406
The ModulePass which wraps up a CallGraph and the logic to build it.
Definition: CallGraph.h:324
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:46
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB)
alias - If one of the pointers is to a global that we are tracking, and the other is some random poin...
An alias analysis result set for globals.
Definition: GlobalsModRef.h:32
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
This is an important base class in LLVM.
Definition: Constant.h:42
bool isPointerTy() const
True if this is an instance of PointerType.
Definition: Type.h:221
#define H(x, y, z)
Definition: MD5.cpp:57
FunctionModRefBehavior getModRefBehavior(const Function *F)
getModRefBehavior - Return the behavior of the specified function if called from the specified call s...
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:371
AliasResult
The possible results of an alias query.
Definition: AliasAnalysis.h:79
Represent the analysis usage information of a pass.
bool hasOperandBundles() const
Definition: CallSite.h:535
This instruction compares its operands according to the predicate given to the constructor.
Value * GetUnderlyingObject(Value *V, const DataLayout &DL, unsigned MaxLookup=6)
This method strips off any GEP address adjustments and pointer casts from the specified value...
name anon globals
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE, "Assign register bank of generic virtual registers", false, false) RegBankSelect
This function does not perform any non-local loads or stores to memory.
void initializeGlobalsAAWrapperPassPass(PassRegistry &)
const Value * Ptr
The address of the start of the location.
Representation for a specific memory location.
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:864
Module.h This file contains the declarations for the Module class.
Provides information about what library functions are available for the current target.
void eraseModRefInfoForGlobal(const GlobalValue &GV)
Clear a global&#39;s ModRef info.
const DataFlowGraph & G
Definition: RDFGraph.cpp:211
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:385
void addModRefInfo(ModRefInfo NewMRI)
Adds new ModRefInfo for this function to its state.
This function does not perform any non-local stores or volatile loads, but may read from any memory l...
void setPreservesAll()
Set by analyses that do not transform their input at all.
iterator_range< user_iterator > users()
Definition: Value.h:401
void setPointerAndInt(PointerTy PtrVal, IntType IntVal)
bool doesNotAccessMemory() const
Determine if the call does not access memory.
Definition: CallSite.h:446
amdgpu Simplify well known AMD library false Value Value * Arg
An analysis pass to compute the CallGraph for a Module.
Definition: CallGraph.h:292
Basic Alias true
The basic data container for the call graph of a Module of IR.
Definition: CallGraph.h:74
#define LLVM_ALIGNAS(x)
LLVM_ALIGNAS
Definition: Compiler.h:322
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:61
FunctionInfo()
Checks to document the invariants of the bit packing here.
Establish a view to a call site for examination.
Definition: CallSite.h:713
ModulePass * createGlobalsAAWrapperPass()
The access both references and modifies the value stored in memory.
#define I(x, y, z)
Definition: MD5.cpp:58
ModulePass class - This class is used to implement unstructured interprocedural optimizations and ana...
Definition: Pass.h:225
bool isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI, bool LookThroughBitCast=false)
Tests if a value is a call or invoke to a library function that allocates memory (either malloc...
INITIALIZE_PASS_BEGIN(GlobalsAAWrapperPass, "globals-aa", "Globals Alias Analysis", false, true) INITIALIZE_PASS_END(GlobalsAAWrapperPass
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
globals aa
std::vector< CallRecord >::iterator iterator
Definition: CallGraph.h:184
ModRefInfo getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc)
FunTy * getCalledFunction() const
Return the function being called if this is a direct call, otherwise return null (if it&#39;s an indirect...
Definition: CallSite.h:107
Analysis pass providing the TargetLibraryInfo.
void GetUnderlyingObjects(Value *V, SmallVectorImpl< Value *> &Objects, const DataLayout &DL, LoopInfo *LI=nullptr, unsigned MaxLookup=6)
This method is similar to GetUnderlyingObject except that it can look through phi and select instruct...
const Function * getFunction() const
Definition: Function.h:134
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:556
LLVM Value Representation.
Definition: Value.h:73
unsigned getOpcode() const
Return the opcode for this Instruction or ConstantExpr.
Definition: Operator.h:41
inst_range instructions(Function *F)
Definition: InstIterator.h:134
A container for analyses that lazily runs them and caches their results.
A special type used by analysis passes to provide an address that identifies that particular analysis...
Definition: PassManager.h:70
ModRefInfo getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc)
static bool isNonEscapingGlobalNoAliasWithLoad(const GlobalValue *GV, const Value *V, int &Depth, const DataLayout &DL)
Enumerate the SCCs of a directed graph in reverse topological order of the SCC DAG.
Definition: SCCIterator.h:43
bool is_contained(R &&Range, const E &Element)
Wrapper function around std::find to detect if an element exists in a container.
Definition: STLExtras.h:821
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...