LLVM  4.0.0
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) {}
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  if (!SCC[0]->getFunction() || !SCC[0]->getFunction()->isDefinitionExact()) {
479  // Calls externally or not exact - can't say anything useful. Remove any
480  // existing function records (may have been created when scanning
481  // globals).
482  for (auto *Node : SCC)
483  FunctionInfos.erase(Node->getFunction());
484  continue;
485  }
486 
487  FunctionInfo &FI = FunctionInfos[SCC[0]->getFunction()];
488  bool KnowNothing = false;
489 
490  // Collect the mod/ref properties due to called functions. We only compute
491  // one mod-ref set.
492  for (unsigned i = 0, e = SCC.size(); i != e && !KnowNothing; ++i) {
493  Function *F = SCC[i]->getFunction();
494  if (!F) {
495  KnowNothing = true;
496  break;
497  }
498 
499  if (F->isDeclaration()) {
500  // Try to get mod/ref behaviour from function attributes.
501  if (F->doesNotAccessMemory()) {
502  // Can't do better than that!
503  } else if (F->onlyReadsMemory()) {
504  FI.addModRefInfo(MRI_Ref);
505  if (!F->isIntrinsic() && !F->onlyAccessesArgMemory())
506  // This function might call back into the module and read a global -
507  // consider every global as possibly being read by this function.
508  FI.setMayReadAnyGlobal();
509  } else {
510  FI.addModRefInfo(MRI_ModRef);
511  // Can't say anything useful unless it's an intrinsic - they don't
512  // read or write global variables of the kind considered here.
513  KnowNothing = !F->isIntrinsic();
514  }
515  continue;
516  }
517 
518  for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end();
519  CI != E && !KnowNothing; ++CI)
520  if (Function *Callee = CI->second->getFunction()) {
521  if (FunctionInfo *CalleeFI = getFunctionInfo(Callee)) {
522  // Propagate function effect up.
523  FI.addFunctionInfo(*CalleeFI);
524  } else {
525  // Can't say anything about it. However, if it is inside our SCC,
526  // then nothing needs to be done.
527  CallGraphNode *CalleeNode = CG[Callee];
528  if (!is_contained(SCC, CalleeNode))
529  KnowNothing = true;
530  }
531  } else {
532  KnowNothing = true;
533  }
534  }
535 
536  // If we can't say anything useful about this SCC, remove all SCC functions
537  // from the FunctionInfos map.
538  if (KnowNothing) {
539  for (auto *Node : SCC)
540  FunctionInfos.erase(Node->getFunction());
541  continue;
542  }
543 
544  // Scan the function bodies for explicit loads or stores.
545  for (auto *Node : SCC) {
546  if (FI.getModRefInfo() == MRI_ModRef)
547  break; // The mod/ref lattice saturates here.
548  for (Instruction &I : instructions(Node->getFunction())) {
549  if (FI.getModRefInfo() == MRI_ModRef)
550  break; // The mod/ref lattice saturates here.
551 
552  // We handle calls specially because the graph-relevant aspects are
553  // handled above.
554  if (auto CS = CallSite(&I)) {
555  if (isAllocationFn(&I, &TLI) || isFreeCall(&I, &TLI)) {
556  // FIXME: It is completely unclear why this is necessary and not
557  // handled by the above graph code.
558  FI.addModRefInfo(MRI_ModRef);
559  } else if (Function *Callee = CS.getCalledFunction()) {
560  // The callgraph doesn't include intrinsic calls.
561  if (Callee->isIntrinsic()) {
562  FunctionModRefBehavior Behaviour =
564  FI.addModRefInfo(ModRefInfo(Behaviour & MRI_ModRef));
565  }
566  }
567  continue;
568  }
569 
570  // All non-call instructions we use the primary predicates for whether
571  // thay read or write memory.
572  if (I.mayReadFromMemory())
573  FI.addModRefInfo(MRI_Ref);
574  if (I.mayWriteToMemory())
575  FI.addModRefInfo(MRI_Mod);
576  }
577  }
578 
579  if ((FI.getModRefInfo() & MRI_Mod) == 0)
580  ++NumReadMemFunctions;
581  if (FI.getModRefInfo() == MRI_NoModRef)
582  ++NumNoMemFunctions;
583 
584  // Finally, now that we know the full effect on this SCC, clone the
585  // information to each function in the SCC.
586  // FI is a reference into FunctionInfos, so copy it now so that it doesn't
587  // get invalidated if DenseMap decides to re-hash.
588  FunctionInfo CachedFI = FI;
589  for (unsigned i = 1, e = SCC.size(); i != e; ++i)
590  FunctionInfos[SCC[i]->getFunction()] = CachedFI;
591  }
592 }
593 
594 // GV is a non-escaping global. V is a pointer address that has been loaded from.
595 // If we can prove that V must escape, we can conclude that a load from V cannot
596 // alias GV.
598  const Value *V,
599  int &Depth,
600  const DataLayout &DL) {
603  Visited.insert(V);
604  Inputs.push_back(V);
605  do {
606  const Value *Input = Inputs.pop_back_val();
607 
608  if (isa<GlobalValue>(Input) || isa<Argument>(Input) || isa<CallInst>(Input) ||
609  isa<InvokeInst>(Input))
610  // Arguments to functions or returns from functions are inherently
611  // escaping, so we can immediately classify those as not aliasing any
612  // non-addr-taken globals.
613  //
614  // (Transitive) loads from a global are also safe - if this aliased
615  // another global, its address would escape, so no alias.
616  continue;
617 
618  // Recurse through a limited number of selects, loads and PHIs. This is an
619  // arbitrary depth of 4, lower numbers could be used to fix compile time
620  // issues if needed, but this is generally expected to be only be important
621  // for small depths.
622  if (++Depth > 4)
623  return false;
624 
625  if (auto *LI = dyn_cast<LoadInst>(Input)) {
626  Inputs.push_back(GetUnderlyingObject(LI->getPointerOperand(), DL));
627  continue;
628  }
629  if (auto *SI = dyn_cast<SelectInst>(Input)) {
630  const Value *LHS = GetUnderlyingObject(SI->getTrueValue(), DL);
631  const Value *RHS = GetUnderlyingObject(SI->getFalseValue(), DL);
632  if (Visited.insert(LHS).second)
633  Inputs.push_back(LHS);
634  if (Visited.insert(RHS).second)
635  Inputs.push_back(RHS);
636  continue;
637  }
638  if (auto *PN = dyn_cast<PHINode>(Input)) {
639  for (const Value *Op : PN->incoming_values()) {
640  Op = GetUnderlyingObject(Op, DL);
641  if (Visited.insert(Op).second)
642  Inputs.push_back(Op);
643  }
644  continue;
645  }
646 
647  return false;
648  } while (!Inputs.empty());
649 
650  // All inputs were known to be no-alias.
651  return true;
652 }
653 
654 // There are particular cases where we can conclude no-alias between
655 // a non-addr-taken global and some other underlying object. Specifically,
656 // a non-addr-taken global is known to not be escaped from any function. It is
657 // also incorrect for a transformation to introduce an escape of a global in
658 // a way that is observable when it was not there previously. One function
659 // being transformed to introduce an escape which could possibly be observed
660 // (via loading from a global or the return value for example) within another
661 // function is never safe. If the observation is made through non-atomic
662 // operations on different threads, it is a data-race and UB. If the
663 // observation is well defined, by being observed the transformation would have
664 // changed program behavior by introducing the observed escape, making it an
665 // invalid transform.
666 //
667 // This property does require that transformations which *temporarily* escape
668 // a global that was not previously escaped, prior to restoring it, cannot rely
669 // on the results of GMR::alias. This seems a reasonable restriction, although
670 // currently there is no way to enforce it. There is also no realistic
671 // optimization pass that would make this mistake. The closest example is
672 // a transformation pass which does reg2mem of SSA values but stores them into
673 // global variables temporarily before restoring the global variable's value.
674 // This could be useful to expose "benign" races for example. However, it seems
675 // reasonable to require that a pass which introduces escapes of global
676 // variables in this way to either not trust AA results while the escape is
677 // active, or to be forced to operate as a module pass that cannot co-exist
678 // with an alias analysis such as GMR.
679 bool GlobalsAAResult::isNonEscapingGlobalNoAlias(const GlobalValue *GV,
680  const Value *V) {
681  // In order to know that the underlying object cannot alias the
682  // non-addr-taken global, we must know that it would have to be an escape.
683  // Thus if the underlying object is a function argument, a load from
684  // a global, or the return of a function, it cannot alias. We can also
685  // recurse through PHI nodes and select nodes provided all of their inputs
686  // resolve to one of these known-escaping roots.
689  Visited.insert(V);
690  Inputs.push_back(V);
691  int Depth = 0;
692  do {
693  const Value *Input = Inputs.pop_back_val();
694 
695  if (auto *InputGV = dyn_cast<GlobalValue>(Input)) {
696  // If one input is the very global we're querying against, then we can't
697  // conclude no-alias.
698  if (InputGV == GV)
699  return false;
700 
701  // Distinct GlobalVariables never alias, unless overriden or zero-sized.
702  // FIXME: The condition can be refined, but be conservative for now.
703  auto *GVar = dyn_cast<GlobalVariable>(GV);
704  auto *InputGVar = dyn_cast<GlobalVariable>(InputGV);
705  if (GVar && InputGVar &&
706  !GVar->isDeclaration() && !InputGVar->isDeclaration() &&
707  !GVar->isInterposable() && !InputGVar->isInterposable()) {
708  Type *GVType = GVar->getInitializer()->getType();
709  Type *InputGVType = InputGVar->getInitializer()->getType();
710  if (GVType->isSized() && InputGVType->isSized() &&
711  (DL.getTypeAllocSize(GVType) > 0) &&
712  (DL.getTypeAllocSize(InputGVType) > 0))
713  continue;
714  }
715 
716  // Conservatively return false, even though we could be smarter
717  // (e.g. look through GlobalAliases).
718  return false;
719  }
720 
721  if (isa<Argument>(Input) || isa<CallInst>(Input) ||
722  isa<InvokeInst>(Input)) {
723  // Arguments to functions or returns from functions are inherently
724  // escaping, so we can immediately classify those as not aliasing any
725  // non-addr-taken globals.
726  continue;
727  }
728 
729  // Recurse through a limited number of selects, loads and PHIs. This is an
730  // arbitrary depth of 4, lower numbers could be used to fix compile time
731  // issues if needed, but this is generally expected to be only be important
732  // for small depths.
733  if (++Depth > 4)
734  return false;
735 
736  if (auto *LI = dyn_cast<LoadInst>(Input)) {
737  // A pointer loaded from a global would have been captured, and we know
738  // that the global is non-escaping, so no alias.
739  const Value *Ptr = GetUnderlyingObject(LI->getPointerOperand(), DL);
740  if (isNonEscapingGlobalNoAliasWithLoad(GV, Ptr, Depth, DL))
741  // The load does not alias with GV.
742  continue;
743  // Otherwise, a load could come from anywhere, so bail.
744  return false;
745  }
746  if (auto *SI = dyn_cast<SelectInst>(Input)) {
747  const Value *LHS = GetUnderlyingObject(SI->getTrueValue(), DL);
748  const Value *RHS = GetUnderlyingObject(SI->getFalseValue(), DL);
749  if (Visited.insert(LHS).second)
750  Inputs.push_back(LHS);
751  if (Visited.insert(RHS).second)
752  Inputs.push_back(RHS);
753  continue;
754  }
755  if (auto *PN = dyn_cast<PHINode>(Input)) {
756  for (const Value *Op : PN->incoming_values()) {
757  Op = GetUnderlyingObject(Op, DL);
758  if (Visited.insert(Op).second)
759  Inputs.push_back(Op);
760  }
761  continue;
762  }
763 
764  // FIXME: It would be good to handle other obvious no-alias cases here, but
765  // it isn't clear how to do so reasonbly without building a small version
766  // of BasicAA into this code. We could recurse into AAResultBase::alias
767  // here but that seems likely to go poorly as we're inside the
768  // implementation of such a query. Until then, just conservatievly retun
769  // false.
770  return false;
771  } while (!Inputs.empty());
772 
773  // If all the inputs to V were definitively no-alias, then V is no-alias.
774  return true;
775 }
776 
777 /// alias - If one of the pointers is to a global that we are tracking, and the
778 /// other is some random pointer, we know there cannot be an alias, because the
779 /// address of the global isn't taken.
781  const MemoryLocation &LocB) {
782  // Get the base object these pointers point to.
783  const Value *UV1 = GetUnderlyingObject(LocA.Ptr, DL);
784  const Value *UV2 = GetUnderlyingObject(LocB.Ptr, DL);
785 
786  // If either of the underlying values is a global, they may be non-addr-taken
787  // globals, which we can answer queries about.
788  const GlobalValue *GV1 = dyn_cast<GlobalValue>(UV1);
789  const GlobalValue *GV2 = dyn_cast<GlobalValue>(UV2);
790  if (GV1 || GV2) {
791  // If the global's address is taken, pretend we don't know it's a pointer to
792  // the global.
793  if (GV1 && !NonAddressTakenGlobals.count(GV1))
794  GV1 = nullptr;
795  if (GV2 && !NonAddressTakenGlobals.count(GV2))
796  GV2 = nullptr;
797 
798  // If the two pointers are derived from two different non-addr-taken
799  // globals we know these can't alias.
800  if (GV1 && GV2 && GV1 != GV2)
801  return NoAlias;
802 
803  // If one is and the other isn't, it isn't strictly safe but we can fake
804  // this result if necessary for performance. This does not appear to be
805  // a common problem in practice.
807  if ((GV1 || GV2) && GV1 != GV2)
808  return NoAlias;
809 
810  // Check for a special case where a non-escaping global can be used to
811  // conclude no-alias.
812  if ((GV1 || GV2) && GV1 != GV2) {
813  const GlobalValue *GV = GV1 ? GV1 : GV2;
814  const Value *UV = GV1 ? UV2 : UV1;
815  if (isNonEscapingGlobalNoAlias(GV, UV))
816  return NoAlias;
817  }
818 
819  // Otherwise if they are both derived from the same addr-taken global, we
820  // can't know the two accesses don't overlap.
821  }
822 
823  // These pointers may be based on the memory owned by an indirect global. If
824  // so, we may be able to handle this. First check to see if the base pointer
825  // is a direct load from an indirect global.
826  GV1 = GV2 = nullptr;
827  if (const LoadInst *LI = dyn_cast<LoadInst>(UV1))
828  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0)))
829  if (IndirectGlobals.count(GV))
830  GV1 = GV;
831  if (const LoadInst *LI = dyn_cast<LoadInst>(UV2))
832  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0)))
833  if (IndirectGlobals.count(GV))
834  GV2 = GV;
835 
836  // These pointers may also be from an allocation for the indirect global. If
837  // so, also handle them.
838  if (!GV1)
839  GV1 = AllocsForIndirectGlobals.lookup(UV1);
840  if (!GV2)
841  GV2 = AllocsForIndirectGlobals.lookup(UV2);
842 
843  // Now that we know whether the two pointers are related to indirect globals,
844  // use this to disambiguate the pointers. If the pointers are based on
845  // different indirect globals they cannot alias.
846  if (GV1 && GV2 && GV1 != GV2)
847  return NoAlias;
848 
849  // If one is based on an indirect global and the other isn't, it isn't
850  // strictly safe but we can fake this result if necessary for performance.
851  // This does not appear to be a common problem in practice.
853  if ((GV1 || GV2) && GV1 != GV2)
854  return NoAlias;
855 
856  return AAResultBase::alias(LocA, LocB);
857 }
858 
859 ModRefInfo GlobalsAAResult::getModRefInfoForArgument(ImmutableCallSite CS,
860  const GlobalValue *GV) {
861  if (CS.doesNotAccessMemory())
862  return MRI_NoModRef;
863  ModRefInfo ConservativeResult = CS.onlyReadsMemory() ? MRI_Ref : MRI_ModRef;
864 
865  // Iterate through all the arguments to the called function. If any argument
866  // is based on GV, return the conservative result.
867  for (auto &A : CS.args()) {
868  SmallVector<Value*, 4> Objects;
869  GetUnderlyingObjects(A, Objects, DL);
870 
871  // All objects must be identified.
872  if (!all_of(Objects, isIdentifiedObject) &&
873  // Try ::alias to see if all objects are known not to alias GV.
874  !all_of(Objects, [&](Value *V) {
875  return this->alias(MemoryLocation(V), MemoryLocation(GV)) == NoAlias;
876  }))
877  return ConservativeResult;
878 
879  if (is_contained(Objects, GV))
880  return ConservativeResult;
881  }
882 
883  // We identified all objects in the argument list, and none of them were GV.
884  return MRI_NoModRef;
885 }
886 
888  const MemoryLocation &Loc) {
889  unsigned Known = MRI_ModRef;
890 
891  // If we are asking for mod/ref info of a direct call with a pointer to a
892  // global we are tracking, return information if we have it.
893  if (const GlobalValue *GV =
894  dyn_cast<GlobalValue>(GetUnderlyingObject(Loc.Ptr, DL)))
895  if (GV->hasLocalLinkage())
896  if (const Function *F = CS.getCalledFunction())
897  if (NonAddressTakenGlobals.count(GV))
898  if (const FunctionInfo *FI = getFunctionInfo(F))
899  Known = FI->getModRefInfoForGlobal(*GV) |
900  getModRefInfoForArgument(CS, GV);
901 
902  if (Known == MRI_NoModRef)
903  return MRI_NoModRef; // No need to query other mod/ref analyses
904  return ModRefInfo(Known & AAResultBase::getModRefInfo(CS, Loc));
905 }
906 
907 GlobalsAAResult::GlobalsAAResult(const DataLayout &DL,
908  const TargetLibraryInfo &TLI)
909  : AAResultBase(), DL(DL), TLI(TLI) {}
910 
911 GlobalsAAResult::GlobalsAAResult(GlobalsAAResult &&Arg)
912  : AAResultBase(std::move(Arg)), DL(Arg.DL), TLI(Arg.TLI),
913  NonAddressTakenGlobals(std::move(Arg.NonAddressTakenGlobals)),
914  IndirectGlobals(std::move(Arg.IndirectGlobals)),
915  AllocsForIndirectGlobals(std::move(Arg.AllocsForIndirectGlobals)),
916  FunctionInfos(std::move(Arg.FunctionInfos)),
917  Handles(std::move(Arg.Handles)) {
918  // Update the parent for each DeletionCallbackHandle.
919  for (auto &H : Handles) {
920  assert(H.GAR == &Arg);
921  H.GAR = this;
922  }
923 }
924 
926 
927 /*static*/ GlobalsAAResult
929  CallGraph &CG) {
930  GlobalsAAResult Result(M.getDataLayout(), TLI);
931 
932  // Discover which functions aren't recursive, to feed into AnalyzeGlobals.
933  Result.CollectSCCMembership(CG);
934 
935  // Find non-addr taken globals.
936  Result.AnalyzeGlobals(M);
937 
938  // Propagate on CG.
939  Result.AnalyzeCallGraph(CG, M);
940 
941  return Result;
942 }
943 
944 AnalysisKey GlobalsAA::Key;
945 
950 }
951 
952 char GlobalsAAWrapperPass::ID = 0;
954  "Globals Alias Analysis", false, true)
958  "Globals Alias Analysis", false, true)
959 
961  return new GlobalsAAWrapperPass();
962 }
963 
966 }
967 
970  M, getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
971  getAnalysis<CallGraphWrapperPass>().getCallGraph())));
972  return false;
973 }
974 
976  Result.reset();
977  return false;
978 }
979 
981  AU.setPreservesAll();
984 }
Legacy wrapper pass to provide the GlobalsAAResult object.
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:102
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:241
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:326
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
void addFunctionInfo(const FunctionInfo &FI)
Add mod/ref info from another function into ours, saturating towards MRI_ModRef.
STATISTIC(NumFunctions,"Total number of functions")
void setMayReadAnyGlobal()
Sets this function as potentially reading from any global.
size_t i
globals Globals Alias Analysis
static cl::opt< bool > EnableUnsafeGlobalsModRefAliasResults("enable-unsafe-globalsmodref-alias-results", cl::init(false), cl::Hidden)
FunctionInfo & operator=(const FunctionInfo &RHS)
This is the interface for a simple mod/ref and alias analysis over globals.
bool onlyReadsMemory() const
Determine if the function does not access or only reads memory.
Definition: Function.h:321
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:52
bool isIntrinsic() const
isIntrinsic - Returns true if the function's name starts with "llvm.".
Definition: Function.h:151
FunctionInfo & operator=(FunctionInfo &&RHS)
bool onlyReadsMemory() const
Determine if the call does not access or only reads memory.
Definition: CallSite.h:429
const_iterator begin(StringRef path)
Get begin iterator over path.
Definition: Path.cpp:233
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:736
The two locations do not alias at all.
Definition: AliasAnalysis.h:79
An instruction for reading from memory.
Definition: Instructions.h:164
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 Constant * getInitializer() const
getInitializer - Return the initializer for this global variable.
ModRefInfo getModRefInfo() const
Returns the ModRefInfo info for this function.
A node in the call graph for a module.
Definition: CallGraph.h:171
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:345
std::vector< CallRecord >::iterator iterator
Definition: CallGraph.h:187
AnalysisUsage & addRequired()
bool mayReadAnyGlobal() const
Returns whether this function may read any global variable, and we don't know which global...
#define INITIALIZE_PASS_DEPENDENCY(depName)
Definition: PassSupport.h:53
ModRefInfo
Flags indicating whether a memory access modifies or references memory.
Definition: AliasAnalysis.h:94
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.
Definition: AliasAnalysis.h:98
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:60
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)
#define F(x, y, z)
Definition: MD5.cpp:51
PointerTy getPointer() const
bool runOnModule(Module &M) override
runOnModule - Virtual method overriden by subclasses to process the module being operated on...
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:300
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB)
FunctionInfo(const FunctionInfo &Arg)
IntType getInt() const
bool doesNotAccessMemory() const
Determine if the function does not access memory.
Definition: Function.h:313
static GCRegistry::Add< CoreCLRGC > E("coreclr","CoreCLR-compatible GC")
bool hasOperandBundles() const
Definition: CallSite.h:492
INITIALIZE_PASS_BEGIN(GlobalsAAWrapperPass,"globals-aa","Globals Alias Analysis", false, true) INITIALIZE_PASS_END(GlobalsAAWrapperPass
FunctionModRefBehavior getModRefBehavior(ImmutableCallSite CS)
bool isSized(SmallPtrSetImpl< Type * > *Visited=nullptr) const
Return true if it makes sense to take the size of this type.
Definition: Type.h:254
The access neither references nor modifies the value stored in memory.
Definition: AliasAnalysis.h:96
#define P(N)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:395
iterator_range< IterTy > args() const
Definition: CallSite.h:207
The ModulePass which wraps up a CallGraph and the logic to build it.
Definition: CallGraph.h:328
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs...ExtraArgs)
Get the result of an analysis pass for a given IR unit.
Definition: PassManager.h:653
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
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
This is an important base class in LLVM.
Definition: Constant.h:42
#define H(x, y, z)
Definition: MD5.cpp:53
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:368
AliasResult
The possible results of an alias query.
Definition: AliasAnalysis.h:73
Represent the analysis usage information of a pass.
This instruction compares its operands according to the predicate given to the constructor.
INITIALIZE_PASS_END(RegBankSelect, DEBUG_TYPE,"Assign register bank of generic virtual registers", false, false) RegBankSelect
bool isPointerTy() const
True if this is an instance of PointerType.
Definition: Type.h:213
bool onlyAccessesArgMemory() const
Determine if the call can access memmory only using pointers based on its arguments.
Definition: Function.h:338
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
This function does not perform any non-local loads or stores to memory.
void initializeGlobalsAAWrapperPassPass(PassRegistry &)
bool doesNotAccessMemory() const
Determine if the call does not access memory.
Definition: CallSite.h:421
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:425
uint64_t getTypeAllocSize(Type *Ty) const
Returns the offset in bytes between successive objects of the specified type, including alignment pad...
Definition: DataLayout.h:408
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:843
Module.h This file contains the declarations for the Module class.
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:230
Provides information about what library functions are available for the current target.
void eraseModRefInfoForGlobal(const GlobalValue &GV)
Clear a global's ModRef info.
const DataFlowGraph & G
Definition: RDFGraph.cpp:206
LLVM_NODISCARD T pop_back_val()
Definition: SmallVector.h:382
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...
static GCRegistry::Add< ShadowStackGC > C("shadow-stack","Very portable GC for uncooperative code generators")
ModRefInfo getModRefInfoForGlobal(const GlobalValue &GV) const
Returns the ModRefInfo info for this function w.r.t.
void setPreservesAll()
Set by analyses that do not transform their input at all.
iterator_range< user_iterator > users()
Definition: Value.h:370
void setPointerAndInt(PointerTy PtrVal, IntType IntVal)
unsigned getOpcode() const
Return the opcode for this Instruction or ConstantExpr.
Definition: Operator.h:49
An analysis pass to compute the CallGraph for a Module.
Definition: CallGraph.h:298
Basic Alias true
const DataLayout & getDataLayout() const
Get the data layout for the module's target platform.
Definition: Module.cpp:384
The basic data container for the call graph of a Module of IR.
Definition: CallGraph.h:76
#define LLVM_ALIGNAS(x)
LLVM_ALIGNAS
Definition: Compiler.h:326
bool isDeclaration() const
Return true if the primary definition of this global value is outside of the current translation unit...
Definition: Globals.cpp:188
FunctionInfo()
Checks to document the invariants of the bit packing here.
ImmutableCallSite - establish a view to a call site for examination.
Definition: CallSite.h:665
ModulePass * createGlobalsAAWrapperPass()
The access both references and modifies the value stored in memory.
#define I(x, y, z)
Definition: MD5.cpp:54
ModulePass class - This class is used to implement unstructured interprocedural optimizations and ana...
Definition: Pass.h:235
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...
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:287
globals aa
bool hasLocalLinkage() const
Definition: GlobalValue.h:415
ModRefInfo getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc)
Analysis pass providing the TargetLibraryInfo.
globals Globals Alias false
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
FunTy * getCalledFunction() const
getCalledFunction - Return the function being called if this is a direct call, otherwise return null ...
Definition: CallSite.h:110
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:537
LLVM Value Representation.
Definition: Value.h:71
inst_range instructions(Function *F)
Definition: InstIterator.h:132
A container for analyses that lazily runs them and caches their results.
int * Ptr
static GCRegistry::Add< ErlangGC > A("erlang","erlang-compatible garbage collector")
A special type used by analysis passes to provide an address that identifies that particular analysis...
Definition: PassManager.h:64
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:783
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...