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 17 #include "llvm/Analysis/Passes.h" 18 #include "llvm/ADT/SCCIterator.h" 19 #include "llvm/ADT/Statistic.h" 20 #include "llvm/Analysis/AliasAnalysis.h" 21 #include "llvm/Analysis/CallGraph.h" 22 #include "llvm/Analysis/MemoryBuiltins.h" 23 #include "llvm/Analysis/ValueTracking.h" 24 #include "llvm/IR/Constants.h" 25 #include "llvm/IR/DerivedTypes.h" 26 #include "llvm/IR/InstIterator.h" 27 #include "llvm/IR/Instructions.h" 28 #include "llvm/IR/IntrinsicInst.h" 29 #include "llvm/IR/Module.h" 30 #include "llvm/Pass.h" 31 #include "llvm/Support/CommandLine.h" 32 #include <set> 33 using namespace llvm; 34 35 #define DEBUG_TYPE "globalsmodref-aa" 36 37 STATISTIC(NumNonAddrTakenGlobalVars, 38 "Number of global vars without address taken"); 39 STATISTIC(NumNonAddrTakenFunctions,"Number of functions without address taken"); 40 STATISTIC(NumNoMemFunctions, "Number of functions that do not access memory"); 41 STATISTIC(NumReadMemFunctions, "Number of functions that only read memory"); 42 STATISTIC(NumIndirectGlobalVars, "Number of indirect global objects"); 43 44 namespace { 45 /// FunctionRecord - One instance of this structure is stored for every 46 /// function in the program. Later, the entries for these functions are 47 /// removed if the function is found to call an external function (in which 48 /// case we know nothing about it. 49 struct FunctionRecord { 50 /// GlobalInfo - Maintain mod/ref info for all of the globals without 51 /// addresses taken that are read or written (transitively) by this 52 /// function. 53 std::map<const GlobalValue*, unsigned> GlobalInfo; 54 55 /// MayReadAnyGlobal - May read global variables, but it is not known which. 56 bool MayReadAnyGlobal; 57 58 unsigned getInfoForGlobal(const GlobalValue *GV) const { 59 unsigned Effect = MayReadAnyGlobal ? AliasAnalysis::Ref : 0; 60 std::map<const GlobalValue*, unsigned>::const_iterator I = 61 GlobalInfo.find(GV); 62 if (I != GlobalInfo.end()) 63 Effect |= I->second; 64 return Effect; 65 } 66 67 /// FunctionEffect - Capture whether or not this function reads or writes to 68 /// ANY memory. If not, we can do a lot of aggressive analysis on it. 69 unsigned FunctionEffect; 70 71 FunctionRecord() : MayReadAnyGlobal (false), FunctionEffect(0) {} 72 }; 73 74 /// GlobalsModRef - The actual analysis pass. 75 class GlobalsModRef : public ModulePass, public AliasAnalysis { 76 /// NonAddressTakenGlobals - The globals that do not have their addresses 77 /// taken. 78 std::set<const GlobalValue*> NonAddressTakenGlobals; 79 80 /// IndirectGlobals - The memory pointed to by this global is known to be 81 /// 'owned' by the global. 82 std::set<const GlobalValue*> IndirectGlobals; 83 84 /// AllocsForIndirectGlobals - If an instruction allocates memory for an 85 /// indirect global, this map indicates which one. 86 std::map<const Value*, const GlobalValue*> AllocsForIndirectGlobals; 87 88 /// FunctionInfo - For each function, keep track of what globals are 89 /// modified or read. 90 std::map<const Function*, FunctionRecord> FunctionInfo; 91 92 public: 93 static char ID; 94 GlobalsModRef() : ModulePass(ID) { 95 initializeGlobalsModRefPass(*PassRegistry::getPassRegistry()); 96 } 97 98 bool runOnModule(Module &M) override { 99 InitializeAliasAnalysis(this, &M.getDataLayout()); 100 101 // Find non-addr taken globals. 102 AnalyzeGlobals(M); 103 104 // Propagate on CG. 105 AnalyzeCallGraph(getAnalysis<CallGraphWrapperPass>().getCallGraph(), M); 106 return false; 107 } 108 109 void getAnalysisUsage(AnalysisUsage &AU) const override { 110 AliasAnalysis::getAnalysisUsage(AU); 111 AU.addRequired<CallGraphWrapperPass>(); 112 AU.setPreservesAll(); // Does not transform code 113 } 114 115 //------------------------------------------------ 116 // Implement the AliasAnalysis API 117 // 118 AliasResult alias(const Location &LocA, const Location &LocB) override; 119 ModRefResult getModRefInfo(ImmutableCallSite CS, 120 const Location &Loc) override; 121 ModRefResult getModRefInfo(ImmutableCallSite CS1, 122 ImmutableCallSite CS2) override { 123 return AliasAnalysis::getModRefInfo(CS1, CS2); 124 } 125 126 /// getModRefBehavior - Return the behavior of the specified function if 127 /// called from the specified call site. The call site may be null in which 128 /// case the most generic behavior of this function should be returned. 129 ModRefBehavior getModRefBehavior(const Function *F) override { 130 ModRefBehavior Min = UnknownModRefBehavior; 131 132 if (FunctionRecord *FR = getFunctionInfo(F)) { 133 if (FR->FunctionEffect == 0) 134 Min = DoesNotAccessMemory; 135 else if ((FR->FunctionEffect & Mod) == 0) 136 Min = OnlyReadsMemory; 137 } 138 139 return ModRefBehavior(AliasAnalysis::getModRefBehavior(F) & Min); 140 } 141 142 /// getModRefBehavior - Return the behavior of the specified function if 143 /// called from the specified call site. The call site may be null in which 144 /// case the most generic behavior of this function should be returned. 145 ModRefBehavior getModRefBehavior(ImmutableCallSite CS) override { 146 ModRefBehavior Min = UnknownModRefBehavior; 147 148 if (const Function* F = CS.getCalledFunction()) 149 if (FunctionRecord *FR = getFunctionInfo(F)) { 150 if (FR->FunctionEffect == 0) 151 Min = DoesNotAccessMemory; 152 else if ((FR->FunctionEffect & Mod) == 0) 153 Min = OnlyReadsMemory; 154 } 155 156 return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min); 157 } 158 159 void deleteValue(Value *V) override; 160 void copyValue(Value *From, Value *To) override; 161 void addEscapingUse(Use &U) override; 162 163 /// getAdjustedAnalysisPointer - This method is used when a pass implements 164 /// an analysis interface through multiple inheritance. If needed, it 165 /// should override this to adjust the this pointer as needed for the 166 /// specified pass info. 167 void *getAdjustedAnalysisPointer(AnalysisID PI) override { 168 if (PI == &AliasAnalysis::ID) 169 return (AliasAnalysis*)this; 170 return this; 171 } 172 173 private: 174 /// getFunctionInfo - Return the function info for the function, or null if 175 /// we don't have anything useful to say about it. 176 FunctionRecord *getFunctionInfo(const Function *F) { 177 std::map<const Function*, FunctionRecord>::iterator I = 178 FunctionInfo.find(F); 179 if (I != FunctionInfo.end()) 180 return &I->second; 181 return nullptr; 182 } 183 184 void AnalyzeGlobals(Module &M); 185 void AnalyzeCallGraph(CallGraph &CG, Module &M); 186 bool AnalyzeUsesOfPointer(Value *V, std::vector<Function*> &Readers, 187 std::vector<Function*> &Writers, 188 GlobalValue *OkayStoreDest = nullptr); 189 bool AnalyzeIndirectGlobalMemory(GlobalValue *GV); 190 }; 191 } 192 193 char GlobalsModRef::ID = 0; 194 INITIALIZE_AG_PASS_BEGIN(GlobalsModRef, AliasAnalysis, 195 "globalsmodref-aa", "Simple mod/ref analysis for globals", 196 false, true, false) 197 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass) 198 INITIALIZE_AG_PASS_END(GlobalsModRef, AliasAnalysis, 199 "globalsmodref-aa", "Simple mod/ref analysis for globals", 200 false, true, false) 201 202 Pass *llvm::createGlobalsModRefPass() { return new GlobalsModRef(); } 203 204 /// AnalyzeGlobals - Scan through the users of all of the internal 205 /// GlobalValue's in the program. If none of them have their "address taken" 206 /// (really, their address passed to something nontrivial), record this fact, 207 /// and record the functions that they are used directly in. 208 void GlobalsModRef::AnalyzeGlobals(Module &M) { 209 std::vector<Function*> Readers, Writers; 210 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 211 if (I->hasLocalLinkage()) { 212 if (!AnalyzeUsesOfPointer(I, Readers, Writers)) { 213 // Remember that we are tracking this global. 214 NonAddressTakenGlobals.insert(I); 215 ++NumNonAddrTakenFunctions; 216 } 217 Readers.clear(); Writers.clear(); 218 } 219 220 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 221 I != E; ++I) 222 if (I->hasLocalLinkage()) { 223 if (!AnalyzeUsesOfPointer(I, Readers, Writers)) { 224 // Remember that we are tracking this global, and the mod/ref fns 225 NonAddressTakenGlobals.insert(I); 226 227 for (unsigned i = 0, e = Readers.size(); i != e; ++i) 228 FunctionInfo[Readers[i]].GlobalInfo[I] |= Ref; 229 230 if (!I->isConstant()) // No need to keep track of writers to constants 231 for (unsigned i = 0, e = Writers.size(); i != e; ++i) 232 FunctionInfo[Writers[i]].GlobalInfo[I] |= Mod; 233 ++NumNonAddrTakenGlobalVars; 234 235 // If this global holds a pointer type, see if it is an indirect global. 236 if (I->getType()->getElementType()->isPointerTy() && 237 AnalyzeIndirectGlobalMemory(I)) 238 ++NumIndirectGlobalVars; 239 } 240 Readers.clear(); Writers.clear(); 241 } 242 } 243 244 /// AnalyzeUsesOfPointer - Look at all of the users of the specified pointer. 245 /// If this is used by anything complex (i.e., the address escapes), return 246 /// true. Also, while we are at it, keep track of those functions that read and 247 /// write to the value. 248 /// 249 /// If OkayStoreDest is non-null, stores into this global are allowed. 250 bool GlobalsModRef::AnalyzeUsesOfPointer(Value *V, 251 std::vector<Function*> &Readers, 252 std::vector<Function*> &Writers, 253 GlobalValue *OkayStoreDest) { 254 if (!V->getType()->isPointerTy()) return true; 255 256 for (Use &U : V->uses()) { 257 User *I = U.getUser(); 258 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 259 Readers.push_back(LI->getParent()->getParent()); 260 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 261 if (V == SI->getOperand(1)) { 262 Writers.push_back(SI->getParent()->getParent()); 263 } else if (SI->getOperand(1) != OkayStoreDest) { 264 return true; // Storing the pointer 265 } 266 } else if (Operator::getOpcode(I) == Instruction::GetElementPtr) { 267 if (AnalyzeUsesOfPointer(I, Readers, Writers)) 268 return true; 269 } else if (Operator::getOpcode(I) == Instruction::BitCast) { 270 if (AnalyzeUsesOfPointer(I, Readers, Writers, OkayStoreDest)) 271 return true; 272 } else if (auto CS = CallSite(I)) { 273 // Make sure that this is just the function being called, not that it is 274 // passing into the function. 275 if (!CS.isCallee(&U)) { 276 // Detect calls to free. 277 if (isFreeCall(I, TLI)) 278 Writers.push_back(CS->getParent()->getParent()); 279 else 280 return true; // Argument of an unknown call. 281 } 282 } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) { 283 if (!isa<ConstantPointerNull>(ICI->getOperand(1))) 284 return true; // Allow comparison against null. 285 } else { 286 return true; 287 } 288 } 289 290 return false; 291 } 292 293 /// AnalyzeIndirectGlobalMemory - We found an non-address-taken global variable 294 /// which holds a pointer type. See if the global always points to non-aliased 295 /// heap memory: that is, all initializers of the globals are allocations, and 296 /// those allocations have no use other than initialization of the global. 297 /// Further, all loads out of GV must directly use the memory, not store the 298 /// pointer somewhere. If this is true, we consider the memory pointed to by 299 /// GV to be owned by GV and can disambiguate other pointers from it. 300 bool GlobalsModRef::AnalyzeIndirectGlobalMemory(GlobalValue *GV) { 301 // Keep track of values related to the allocation of the memory, f.e. the 302 // value produced by the malloc call and any casts. 303 std::vector<Value*> AllocRelatedValues; 304 305 // Walk the user list of the global. If we find anything other than a direct 306 // load or store, bail out. 307 for (User *U : GV->users()) { 308 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 309 // The pointer loaded from the global can only be used in simple ways: 310 // we allow addressing of it and loading storing to it. We do *not* allow 311 // storing the loaded pointer somewhere else or passing to a function. 312 std::vector<Function*> ReadersWriters; 313 if (AnalyzeUsesOfPointer(LI, ReadersWriters, ReadersWriters)) 314 return false; // Loaded pointer escapes. 315 // TODO: Could try some IP mod/ref of the loaded pointer. 316 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 317 // Storing the global itself. 318 if (SI->getOperand(0) == GV) return false; 319 320 // If storing the null pointer, ignore it. 321 if (isa<ConstantPointerNull>(SI->getOperand(0))) 322 continue; 323 324 // Check the value being stored. 325 Value *Ptr = GetUnderlyingObject(SI->getOperand(0), 326 GV->getParent()->getDataLayout()); 327 328 if (!isAllocLikeFn(Ptr, TLI)) 329 return false; // Too hard to analyze. 330 331 // Analyze all uses of the allocation. If any of them are used in a 332 // non-simple way (e.g. stored to another global) bail out. 333 std::vector<Function*> ReadersWriters; 334 if (AnalyzeUsesOfPointer(Ptr, ReadersWriters, ReadersWriters, GV)) 335 return false; // Loaded pointer escapes. 336 337 // Remember that this allocation is related to the indirect global. 338 AllocRelatedValues.push_back(Ptr); 339 } else { 340 // Something complex, bail out. 341 return false; 342 } 343 } 344 345 // Okay, this is an indirect global. Remember all of the allocations for 346 // this global in AllocsForIndirectGlobals. 347 while (!AllocRelatedValues.empty()) { 348 AllocsForIndirectGlobals[AllocRelatedValues.back()] = GV; 349 AllocRelatedValues.pop_back(); 350 } 351 IndirectGlobals.insert(GV); 352 return true; 353 } 354 355 /// AnalyzeCallGraph - At this point, we know the functions where globals are 356 /// immediately stored to and read from. Propagate this information up the call 357 /// graph to all callers and compute the mod/ref info for all memory for each 358 /// function. 359 void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) { 360 // We do a bottom-up SCC traversal of the call graph. In other words, we 361 // visit all callees before callers (leaf-first). 362 for (scc_iterator<CallGraph*> I = scc_begin(&CG); !I.isAtEnd(); ++I) { 363 const std::vector<CallGraphNode *> &SCC = *I; 364 assert(!SCC.empty() && "SCC with no functions?"); 365 366 if (!SCC[0]->getFunction()) { 367 // Calls externally - can't say anything useful. Remove any existing 368 // function records (may have been created when scanning globals). 369 for (unsigned i = 0, e = SCC.size(); i != e; ++i) 370 FunctionInfo.erase(SCC[i]->getFunction()); 371 continue; 372 } 373 374 FunctionRecord &FR = FunctionInfo[SCC[0]->getFunction()]; 375 376 bool KnowNothing = false; 377 unsigned FunctionEffect = 0; 378 379 // Collect the mod/ref properties due to called functions. We only compute 380 // one mod-ref set. 381 for (unsigned i = 0, e = SCC.size(); i != e && !KnowNothing; ++i) { 382 Function *F = SCC[i]->getFunction(); 383 if (!F) { 384 KnowNothing = true; 385 break; 386 } 387 388 if (F->isDeclaration()) { 389 // Try to get mod/ref behaviour from function attributes. 390 if (F->doesNotAccessMemory()) { 391 // Can't do better than that! 392 } else if (F->onlyReadsMemory()) { 393 FunctionEffect |= Ref; 394 if (!F->isIntrinsic()) 395 // This function might call back into the module and read a global - 396 // consider every global as possibly being read by this function. 397 FR.MayReadAnyGlobal = true; 398 } else { 399 FunctionEffect |= ModRef; 400 // Can't say anything useful unless it's an intrinsic - they don't 401 // read or write global variables of the kind considered here. 402 KnowNothing = !F->isIntrinsic(); 403 } 404 continue; 405 } 406 407 for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end(); 408 CI != E && !KnowNothing; ++CI) 409 if (Function *Callee = CI->second->getFunction()) { 410 if (FunctionRecord *CalleeFR = getFunctionInfo(Callee)) { 411 // Propagate function effect up. 412 FunctionEffect |= CalleeFR->FunctionEffect; 413 414 // Incorporate callee's effects on globals into our info. 415 for (const auto &G : CalleeFR->GlobalInfo) 416 FR.GlobalInfo[G.first] |= G.second; 417 FR.MayReadAnyGlobal |= CalleeFR->MayReadAnyGlobal; 418 } else { 419 // Can't say anything about it. However, if it is inside our SCC, 420 // then nothing needs to be done. 421 CallGraphNode *CalleeNode = CG[Callee]; 422 if (std::find(SCC.begin(), SCC.end(), CalleeNode) == SCC.end()) 423 KnowNothing = true; 424 } 425 } else { 426 KnowNothing = true; 427 } 428 } 429 430 // If we can't say anything useful about this SCC, remove all SCC functions 431 // from the FunctionInfo map. 432 if (KnowNothing) { 433 for (unsigned i = 0, e = SCC.size(); i != e; ++i) 434 FunctionInfo.erase(SCC[i]->getFunction()); 435 continue; 436 } 437 438 // Scan the function bodies for explicit loads or stores. 439 for (unsigned i = 0, e = SCC.size(); i != e && FunctionEffect != ModRef;++i) 440 for (inst_iterator II = inst_begin(SCC[i]->getFunction()), 441 E = inst_end(SCC[i]->getFunction()); 442 II != E && FunctionEffect != ModRef; ++II) 443 if (LoadInst *LI = dyn_cast<LoadInst>(&*II)) { 444 FunctionEffect |= Ref; 445 if (LI->isVolatile()) 446 // Volatile loads may have side-effects, so mark them as writing 447 // memory (for example, a flag inside the processor). 448 FunctionEffect |= Mod; 449 } else if (StoreInst *SI = dyn_cast<StoreInst>(&*II)) { 450 FunctionEffect |= Mod; 451 if (SI->isVolatile()) 452 // Treat volatile stores as reading memory somewhere. 453 FunctionEffect |= Ref; 454 } else if (isAllocationFn(&*II, TLI) || isFreeCall(&*II, TLI)) { 455 FunctionEffect |= ModRef; 456 } else if (IntrinsicInst *Intrinsic = dyn_cast<IntrinsicInst>(&*II)) { 457 // The callgraph doesn't include intrinsic calls. 458 Function *Callee = Intrinsic->getCalledFunction(); 459 ModRefBehavior Behaviour = AliasAnalysis::getModRefBehavior(Callee); 460 FunctionEffect |= (Behaviour & ModRef); 461 } 462 463 if ((FunctionEffect & Mod) == 0) 464 ++NumReadMemFunctions; 465 if (FunctionEffect == 0) 466 ++NumNoMemFunctions; 467 FR.FunctionEffect = FunctionEffect; 468 469 // Finally, now that we know the full effect on this SCC, clone the 470 // information to each function in the SCC. 471 for (unsigned i = 1, e = SCC.size(); i != e; ++i) 472 FunctionInfo[SCC[i]->getFunction()] = FR; 473 } 474 } 475 476 477 478 /// alias - If one of the pointers is to a global that we are tracking, and the 479 /// other is some random pointer, we know there cannot be an alias, because the 480 /// address of the global isn't taken. 481 AliasAnalysis::AliasResult 482 GlobalsModRef::alias(const Location &LocA, 483 const Location &LocB) { 484 // Get the base object these pointers point to. 485 const Value *UV1 = GetUnderlyingObject(LocA.Ptr, *DL); 486 const Value *UV2 = GetUnderlyingObject(LocB.Ptr, *DL); 487 488 // If either of the underlying values is a global, they may be non-addr-taken 489 // globals, which we can answer queries about. 490 const GlobalValue *GV1 = dyn_cast<GlobalValue>(UV1); 491 const GlobalValue *GV2 = dyn_cast<GlobalValue>(UV2); 492 if (GV1 || GV2) { 493 // If the global's address is taken, pretend we don't know it's a pointer to 494 // the global. 495 if (GV1 && !NonAddressTakenGlobals.count(GV1)) GV1 = nullptr; 496 if (GV2 && !NonAddressTakenGlobals.count(GV2)) GV2 = nullptr; 497 498 // If the two pointers are derived from two different non-addr-taken 499 // globals, or if one is and the other isn't, we know these can't alias. 500 if ((GV1 || GV2) && GV1 != GV2) 501 return NoAlias; 502 503 // Otherwise if they are both derived from the same addr-taken global, we 504 // can't know the two accesses don't overlap. 505 } 506 507 // These pointers may be based on the memory owned by an indirect global. If 508 // so, we may be able to handle this. First check to see if the base pointer 509 // is a direct load from an indirect global. 510 GV1 = GV2 = nullptr; 511 if (const LoadInst *LI = dyn_cast<LoadInst>(UV1)) 512 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0))) 513 if (IndirectGlobals.count(GV)) 514 GV1 = GV; 515 if (const LoadInst *LI = dyn_cast<LoadInst>(UV2)) 516 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0))) 517 if (IndirectGlobals.count(GV)) 518 GV2 = GV; 519 520 // These pointers may also be from an allocation for the indirect global. If 521 // so, also handle them. 522 if (AllocsForIndirectGlobals.count(UV1)) 523 GV1 = AllocsForIndirectGlobals[UV1]; 524 if (AllocsForIndirectGlobals.count(UV2)) 525 GV2 = AllocsForIndirectGlobals[UV2]; 526 527 // Now that we know whether the two pointers are related to indirect globals, 528 // use this to disambiguate the pointers. If either pointer is based on an 529 // indirect global and if they are not both based on the same indirect global, 530 // they cannot alias. 531 if ((GV1 || GV2) && GV1 != GV2) 532 return NoAlias; 533 534 return AliasAnalysis::alias(LocA, LocB); 535 } 536 537 AliasAnalysis::ModRefResult 538 GlobalsModRef::getModRefInfo(ImmutableCallSite CS, 539 const Location &Loc) { 540 unsigned Known = ModRef; 541 542 // If we are asking for mod/ref info of a direct call with a pointer to a 543 // global we are tracking, return information if we have it. 544 const DataLayout &DL = CS.getCaller()->getParent()->getDataLayout(); 545 if (const GlobalValue *GV = 546 dyn_cast<GlobalValue>(GetUnderlyingObject(Loc.Ptr, DL))) 547 if (GV->hasLocalLinkage()) 548 if (const Function *F = CS.getCalledFunction()) 549 if (NonAddressTakenGlobals.count(GV)) 550 if (const FunctionRecord *FR = getFunctionInfo(F)) 551 Known = FR->getInfoForGlobal(GV); 552 553 if (Known == NoModRef) 554 return NoModRef; // No need to query other mod/ref analyses 555 return ModRefResult(Known & AliasAnalysis::getModRefInfo(CS, Loc)); 556 } 557 558 559 //===----------------------------------------------------------------------===// 560 // Methods to update the analysis as a result of the client transformation. 561 // 562 void GlobalsModRef::deleteValue(Value *V) { 563 if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) { 564 if (NonAddressTakenGlobals.erase(GV)) { 565 // This global might be an indirect global. If so, remove it and remove 566 // any AllocRelatedValues for it. 567 if (IndirectGlobals.erase(GV)) { 568 // Remove any entries in AllocsForIndirectGlobals for this global. 569 for (std::map<const Value*, const GlobalValue*>::iterator 570 I = AllocsForIndirectGlobals.begin(), 571 E = AllocsForIndirectGlobals.end(); I != E; ) { 572 if (I->second == GV) { 573 AllocsForIndirectGlobals.erase(I++); 574 } else { 575 ++I; 576 } 577 } 578 } 579 } 580 } 581 582 // Otherwise, if this is an allocation related to an indirect global, remove 583 // it. 584 AllocsForIndirectGlobals.erase(V); 585 586 AliasAnalysis::deleteValue(V); 587 } 588 589 void GlobalsModRef::copyValue(Value *From, Value *To) { 590 AliasAnalysis::copyValue(From, To); 591 } 592 593 void GlobalsModRef::addEscapingUse(Use &U) { 594 // For the purposes of this analysis, it is conservatively correct to treat 595 // a newly escaping value equivalently to a deleted one. We could perhaps 596 // be more precise by processing the new use and attempting to update our 597 // saved analysis results to accommodate it. 598 deleteValue(U); 599 600 AliasAnalysis::addEscapingUse(U); 601 } 602