GlobalsModRef.cpp revision 218893
1193323Sed//===- GlobalsModRef.cpp - Simple Mod/Ref Analysis for Globals ------------===// 2193323Sed// 3193323Sed// The LLVM Compiler Infrastructure 4193323Sed// 5193323Sed// This file is distributed under the University of Illinois Open Source 6193323Sed// License. See LICENSE.TXT for details. 7193323Sed// 8193323Sed//===----------------------------------------------------------------------===// 9193323Sed// 10193323Sed// This simple pass provides alias and mod/ref information for global values 11193323Sed// that do not have their address taken, and keeps track of whether functions 12193323Sed// read or write memory (are "pure"). For this simple (but very common) case, 13193323Sed// we can provide pretty accurate and useful information. 14193323Sed// 15193323Sed//===----------------------------------------------------------------------===// 16193323Sed 17193323Sed#define DEBUG_TYPE "globalsmodref-aa" 18193323Sed#include "llvm/Analysis/Passes.h" 19193323Sed#include "llvm/Module.h" 20193323Sed#include "llvm/Pass.h" 21193323Sed#include "llvm/Instructions.h" 22193323Sed#include "llvm/Constants.h" 23193323Sed#include "llvm/DerivedTypes.h" 24193323Sed#include "llvm/Analysis/AliasAnalysis.h" 25193323Sed#include "llvm/Analysis/CallGraph.h" 26198892Srdivacky#include "llvm/Analysis/MemoryBuiltins.h" 27218893Sdim#include "llvm/Analysis/ValueTracking.h" 28193323Sed#include "llvm/Support/CommandLine.h" 29193323Sed#include "llvm/Support/InstIterator.h" 30193323Sed#include "llvm/ADT/Statistic.h" 31193323Sed#include "llvm/ADT/SCCIterator.h" 32193323Sed#include <set> 33193323Sedusing namespace llvm; 34193323Sed 35193323SedSTATISTIC(NumNonAddrTakenGlobalVars, 36193323Sed "Number of global vars without address taken"); 37193323SedSTATISTIC(NumNonAddrTakenFunctions,"Number of functions without address taken"); 38193323SedSTATISTIC(NumNoMemFunctions, "Number of functions that do not access memory"); 39193323SedSTATISTIC(NumReadMemFunctions, "Number of functions that only read memory"); 40193323SedSTATISTIC(NumIndirectGlobalVars, "Number of indirect global objects"); 41193323Sed 42193323Sednamespace { 43193323Sed /// FunctionRecord - One instance of this structure is stored for every 44193323Sed /// function in the program. Later, the entries for these functions are 45193323Sed /// removed if the function is found to call an external function (in which 46193323Sed /// case we know nothing about it. 47198892Srdivacky struct FunctionRecord { 48193323Sed /// GlobalInfo - Maintain mod/ref info for all of the globals without 49193323Sed /// addresses taken that are read or written (transitively) by this 50193323Sed /// function. 51212904Sdim std::map<const GlobalValue*, unsigned> GlobalInfo; 52193323Sed 53193323Sed /// MayReadAnyGlobal - May read global variables, but it is not known which. 54193323Sed bool MayReadAnyGlobal; 55193323Sed 56212904Sdim unsigned getInfoForGlobal(const GlobalValue *GV) const { 57193323Sed unsigned Effect = MayReadAnyGlobal ? AliasAnalysis::Ref : 0; 58212904Sdim std::map<const GlobalValue*, unsigned>::const_iterator I = 59212904Sdim GlobalInfo.find(GV); 60193323Sed if (I != GlobalInfo.end()) 61193323Sed Effect |= I->second; 62193323Sed return Effect; 63193323Sed } 64193323Sed 65193323Sed /// FunctionEffect - Capture whether or not this function reads or writes to 66193323Sed /// ANY memory. If not, we can do a lot of aggressive analysis on it. 67193323Sed unsigned FunctionEffect; 68193323Sed 69193323Sed FunctionRecord() : MayReadAnyGlobal (false), FunctionEffect(0) {} 70193323Sed }; 71193323Sed 72193323Sed /// GlobalsModRef - The actual analysis pass. 73198892Srdivacky class GlobalsModRef : public ModulePass, public AliasAnalysis { 74193323Sed /// NonAddressTakenGlobals - The globals that do not have their addresses 75193323Sed /// taken. 76212904Sdim std::set<const GlobalValue*> NonAddressTakenGlobals; 77193323Sed 78193323Sed /// IndirectGlobals - The memory pointed to by this global is known to be 79193323Sed /// 'owned' by the global. 80212904Sdim std::set<const GlobalValue*> IndirectGlobals; 81193323Sed 82193323Sed /// AllocsForIndirectGlobals - If an instruction allocates memory for an 83193323Sed /// indirect global, this map indicates which one. 84212904Sdim std::map<const Value*, const GlobalValue*> AllocsForIndirectGlobals; 85193323Sed 86193323Sed /// FunctionInfo - For each function, keep track of what globals are 87193323Sed /// modified or read. 88212904Sdim std::map<const Function*, FunctionRecord> FunctionInfo; 89193323Sed 90193323Sed public: 91193323Sed static char ID; 92218893Sdim GlobalsModRef() : ModulePass(ID) { 93218893Sdim initializeGlobalsModRefPass(*PassRegistry::getPassRegistry()); 94218893Sdim } 95193323Sed 96193323Sed bool runOnModule(Module &M) { 97193323Sed InitializeAliasAnalysis(this); // set up super class 98193323Sed AnalyzeGlobals(M); // find non-addr taken globals 99193323Sed AnalyzeCallGraph(getAnalysis<CallGraph>(), M); // Propagate on CG 100193323Sed return false; 101193323Sed } 102193323Sed 103193323Sed virtual void getAnalysisUsage(AnalysisUsage &AU) const { 104193323Sed AliasAnalysis::getAnalysisUsage(AU); 105193323Sed AU.addRequired<CallGraph>(); 106193323Sed AU.setPreservesAll(); // Does not transform code 107193323Sed } 108193323Sed 109193323Sed //------------------------------------------------ 110193323Sed // Implement the AliasAnalysis API 111193323Sed // 112218893Sdim AliasResult alias(const Location &LocA, const Location &LocB); 113212904Sdim ModRefResult getModRefInfo(ImmutableCallSite CS, 114218893Sdim const Location &Loc); 115212904Sdim ModRefResult getModRefInfo(ImmutableCallSite CS1, 116212904Sdim ImmutableCallSite CS2) { 117212904Sdim return AliasAnalysis::getModRefInfo(CS1, CS2); 118193323Sed } 119193323Sed 120193323Sed /// getModRefBehavior - Return the behavior of the specified function if 121193323Sed /// called from the specified call site. The call site may be null in which 122193323Sed /// case the most generic behavior of this function should be returned. 123212904Sdim ModRefBehavior getModRefBehavior(const Function *F) { 124218893Sdim ModRefBehavior Min = UnknownModRefBehavior; 125218893Sdim 126193323Sed if (FunctionRecord *FR = getFunctionInfo(F)) { 127193323Sed if (FR->FunctionEffect == 0) 128218893Sdim Min = DoesNotAccessMemory; 129193323Sed else if ((FR->FunctionEffect & Mod) == 0) 130218893Sdim Min = OnlyReadsMemory; 131193323Sed } 132218893Sdim 133218893Sdim return ModRefBehavior(AliasAnalysis::getModRefBehavior(F) & Min); 134193323Sed } 135193323Sed 136193323Sed /// getModRefBehavior - Return the behavior of the specified function if 137193323Sed /// called from the specified call site. The call site may be null in which 138193323Sed /// case the most generic behavior of this function should be returned. 139212904Sdim ModRefBehavior getModRefBehavior(ImmutableCallSite CS) { 140218893Sdim ModRefBehavior Min = UnknownModRefBehavior; 141218893Sdim 142218893Sdim if (const Function* F = CS.getCalledFunction()) 143218893Sdim if (FunctionRecord *FR = getFunctionInfo(F)) { 144218893Sdim if (FR->FunctionEffect == 0) 145218893Sdim Min = DoesNotAccessMemory; 146218893Sdim else if ((FR->FunctionEffect & Mod) == 0) 147218893Sdim Min = OnlyReadsMemory; 148218893Sdim } 149218893Sdim 150218893Sdim return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min); 151193323Sed } 152193323Sed 153193323Sed virtual void deleteValue(Value *V); 154193323Sed virtual void copyValue(Value *From, Value *To); 155218893Sdim virtual void addEscapingUse(Use &U); 156193323Sed 157202878Srdivacky /// getAdjustedAnalysisPointer - This method is used when a pass implements 158202878Srdivacky /// an analysis interface through multiple inheritance. If needed, it 159202878Srdivacky /// should override this to adjust the this pointer as needed for the 160202878Srdivacky /// specified pass info. 161212904Sdim virtual void *getAdjustedAnalysisPointer(AnalysisID PI) { 162212904Sdim if (PI == &AliasAnalysis::ID) 163202878Srdivacky return (AliasAnalysis*)this; 164202878Srdivacky return this; 165202878Srdivacky } 166202878Srdivacky 167193323Sed private: 168193323Sed /// getFunctionInfo - Return the function info for the function, or null if 169193323Sed /// we don't have anything useful to say about it. 170212904Sdim FunctionRecord *getFunctionInfo(const Function *F) { 171212904Sdim std::map<const Function*, FunctionRecord>::iterator I = 172212904Sdim FunctionInfo.find(F); 173193323Sed if (I != FunctionInfo.end()) 174193323Sed return &I->second; 175193323Sed return 0; 176193323Sed } 177193323Sed 178193323Sed void AnalyzeGlobals(Module &M); 179193323Sed void AnalyzeCallGraph(CallGraph &CG, Module &M); 180193323Sed bool AnalyzeUsesOfPointer(Value *V, std::vector<Function*> &Readers, 181193323Sed std::vector<Function*> &Writers, 182193323Sed GlobalValue *OkayStoreDest = 0); 183193323Sed bool AnalyzeIndirectGlobalMemory(GlobalValue *GV); 184193323Sed }; 185193323Sed} 186193323Sed 187193323Sedchar GlobalsModRef::ID = 0; 188218893SdimINITIALIZE_AG_PASS_BEGIN(GlobalsModRef, AliasAnalysis, 189212904Sdim "globalsmodref-aa", "Simple mod/ref analysis for globals", 190218893Sdim false, true, false) 191218893SdimINITIALIZE_AG_DEPENDENCY(CallGraph) 192218893SdimINITIALIZE_AG_PASS_END(GlobalsModRef, AliasAnalysis, 193218893Sdim "globalsmodref-aa", "Simple mod/ref analysis for globals", 194218893Sdim false, true, false) 195193323Sed 196193323SedPass *llvm::createGlobalsModRefPass() { return new GlobalsModRef(); } 197193323Sed 198193323Sed/// AnalyzeGlobals - Scan through the users of all of the internal 199193323Sed/// GlobalValue's in the program. If none of them have their "address taken" 200193323Sed/// (really, their address passed to something nontrivial), record this fact, 201193323Sed/// and record the functions that they are used directly in. 202193323Sedvoid GlobalsModRef::AnalyzeGlobals(Module &M) { 203193323Sed std::vector<Function*> Readers, Writers; 204193323Sed for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 205193323Sed if (I->hasLocalLinkage()) { 206193323Sed if (!AnalyzeUsesOfPointer(I, Readers, Writers)) { 207193323Sed // Remember that we are tracking this global. 208193323Sed NonAddressTakenGlobals.insert(I); 209193323Sed ++NumNonAddrTakenFunctions; 210193323Sed } 211193323Sed Readers.clear(); Writers.clear(); 212193323Sed } 213193323Sed 214193323Sed for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 215193323Sed I != E; ++I) 216193323Sed if (I->hasLocalLinkage()) { 217193323Sed if (!AnalyzeUsesOfPointer(I, Readers, Writers)) { 218193323Sed // Remember that we are tracking this global, and the mod/ref fns 219193323Sed NonAddressTakenGlobals.insert(I); 220193323Sed 221193323Sed for (unsigned i = 0, e = Readers.size(); i != e; ++i) 222193323Sed FunctionInfo[Readers[i]].GlobalInfo[I] |= Ref; 223193323Sed 224193323Sed if (!I->isConstant()) // No need to keep track of writers to constants 225193323Sed for (unsigned i = 0, e = Writers.size(); i != e; ++i) 226193323Sed FunctionInfo[Writers[i]].GlobalInfo[I] |= Mod; 227193323Sed ++NumNonAddrTakenGlobalVars; 228193323Sed 229193323Sed // If this global holds a pointer type, see if it is an indirect global. 230204642Srdivacky if (I->getType()->getElementType()->isPointerTy() && 231193323Sed AnalyzeIndirectGlobalMemory(I)) 232193323Sed ++NumIndirectGlobalVars; 233193323Sed } 234193323Sed Readers.clear(); Writers.clear(); 235193323Sed } 236193323Sed} 237193323Sed 238193323Sed/// AnalyzeUsesOfPointer - Look at all of the users of the specified pointer. 239193323Sed/// If this is used by anything complex (i.e., the address escapes), return 240193323Sed/// true. Also, while we are at it, keep track of those functions that read and 241193323Sed/// write to the value. 242193323Sed/// 243193323Sed/// If OkayStoreDest is non-null, stores into this global are allowed. 244193323Sedbool GlobalsModRef::AnalyzeUsesOfPointer(Value *V, 245193323Sed std::vector<Function*> &Readers, 246193323Sed std::vector<Function*> &Writers, 247193323Sed GlobalValue *OkayStoreDest) { 248204642Srdivacky if (!V->getType()->isPointerTy()) return true; 249193323Sed 250210299Sed for (Value::use_iterator UI = V->use_begin(), E=V->use_end(); UI != E; ++UI) { 251210299Sed User *U = *UI; 252210299Sed if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 253193323Sed Readers.push_back(LI->getParent()->getParent()); 254210299Sed } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 255193323Sed if (V == SI->getOperand(1)) { 256193323Sed Writers.push_back(SI->getParent()->getParent()); 257193323Sed } else if (SI->getOperand(1) != OkayStoreDest) { 258193323Sed return true; // Storing the pointer 259193323Sed } 260210299Sed } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 261193323Sed if (AnalyzeUsesOfPointer(GEP, Readers, Writers)) return true; 262210299Sed } else if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { 263198090Srdivacky if (AnalyzeUsesOfPointer(BCI, Readers, Writers, OkayStoreDest)) 264198090Srdivacky return true; 265210299Sed } else if (isFreeCall(U)) { 266210299Sed Writers.push_back(cast<Instruction>(U)->getParent()->getParent()); 267210299Sed } else if (CallInst *CI = dyn_cast<CallInst>(U)) { 268193323Sed // Make sure that this is just the function being called, not that it is 269193323Sed // passing into the function. 270210299Sed for (unsigned i = 0, e = CI->getNumArgOperands(); i != e; ++i) 271210299Sed if (CI->getArgOperand(i) == V) return true; 272210299Sed } else if (InvokeInst *II = dyn_cast<InvokeInst>(U)) { 273193323Sed // Make sure that this is just the function being called, not that it is 274193323Sed // passing into the function. 275210299Sed for (unsigned i = 0, e = II->getNumArgOperands(); i != e; ++i) 276210299Sed if (II->getArgOperand(i) == V) return true; 277210299Sed } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { 278193323Sed if (CE->getOpcode() == Instruction::GetElementPtr || 279193323Sed CE->getOpcode() == Instruction::BitCast) { 280193323Sed if (AnalyzeUsesOfPointer(CE, Readers, Writers)) 281193323Sed return true; 282193323Sed } else { 283193323Sed return true; 284193323Sed } 285210299Sed } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(U)) { 286193323Sed if (!isa<ConstantPointerNull>(ICI->getOperand(1))) 287193323Sed return true; // Allow comparison against null. 288193323Sed } else { 289193323Sed return true; 290193323Sed } 291210299Sed } 292210299Sed 293193323Sed return false; 294193323Sed} 295193323Sed 296193323Sed/// AnalyzeIndirectGlobalMemory - We found an non-address-taken global variable 297193323Sed/// which holds a pointer type. See if the global always points to non-aliased 298193323Sed/// heap memory: that is, all initializers of the globals are allocations, and 299193323Sed/// those allocations have no use other than initialization of the global. 300193323Sed/// Further, all loads out of GV must directly use the memory, not store the 301193323Sed/// pointer somewhere. If this is true, we consider the memory pointed to by 302193323Sed/// GV to be owned by GV and can disambiguate other pointers from it. 303193323Sedbool GlobalsModRef::AnalyzeIndirectGlobalMemory(GlobalValue *GV) { 304193323Sed // Keep track of values related to the allocation of the memory, f.e. the 305193323Sed // value produced by the malloc call and any casts. 306193323Sed std::vector<Value*> AllocRelatedValues; 307193323Sed 308193323Sed // Walk the user list of the global. If we find anything other than a direct 309193323Sed // load or store, bail out. 310193323Sed for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){ 311210299Sed User *U = *I; 312210299Sed if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 313193323Sed // The pointer loaded from the global can only be used in simple ways: 314193323Sed // we allow addressing of it and loading storing to it. We do *not* allow 315193323Sed // storing the loaded pointer somewhere else or passing to a function. 316193323Sed std::vector<Function*> ReadersWriters; 317193323Sed if (AnalyzeUsesOfPointer(LI, ReadersWriters, ReadersWriters)) 318193323Sed return false; // Loaded pointer escapes. 319193323Sed // TODO: Could try some IP mod/ref of the loaded pointer. 320210299Sed } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 321193323Sed // Storing the global itself. 322193323Sed if (SI->getOperand(0) == GV) return false; 323193323Sed 324193323Sed // If storing the null pointer, ignore it. 325193323Sed if (isa<ConstantPointerNull>(SI->getOperand(0))) 326193323Sed continue; 327193323Sed 328193323Sed // Check the value being stored. 329218893Sdim Value *Ptr = GetUnderlyingObject(SI->getOperand(0)); 330193323Sed 331198396Srdivacky if (isMalloc(Ptr)) { 332193323Sed // Okay, easy case. 333193323Sed } else if (CallInst *CI = dyn_cast<CallInst>(Ptr)) { 334193323Sed Function *F = CI->getCalledFunction(); 335193323Sed if (!F || !F->isDeclaration()) return false; // Too hard to analyze. 336193323Sed if (F->getName() != "calloc") return false; // Not calloc. 337193323Sed } else { 338193323Sed return false; // Too hard to analyze. 339193323Sed } 340193323Sed 341193323Sed // Analyze all uses of the allocation. If any of them are used in a 342193323Sed // non-simple way (e.g. stored to another global) bail out. 343193323Sed std::vector<Function*> ReadersWriters; 344193323Sed if (AnalyzeUsesOfPointer(Ptr, ReadersWriters, ReadersWriters, GV)) 345193323Sed return false; // Loaded pointer escapes. 346193323Sed 347193323Sed // Remember that this allocation is related to the indirect global. 348193323Sed AllocRelatedValues.push_back(Ptr); 349193323Sed } else { 350193323Sed // Something complex, bail out. 351193323Sed return false; 352193323Sed } 353193323Sed } 354193323Sed 355193323Sed // Okay, this is an indirect global. Remember all of the allocations for 356193323Sed // this global in AllocsForIndirectGlobals. 357193323Sed while (!AllocRelatedValues.empty()) { 358193323Sed AllocsForIndirectGlobals[AllocRelatedValues.back()] = GV; 359193323Sed AllocRelatedValues.pop_back(); 360193323Sed } 361193323Sed IndirectGlobals.insert(GV); 362193323Sed return true; 363193323Sed} 364193323Sed 365193323Sed/// AnalyzeCallGraph - At this point, we know the functions where globals are 366193323Sed/// immediately stored to and read from. Propagate this information up the call 367193323Sed/// graph to all callers and compute the mod/ref info for all memory for each 368193323Sed/// function. 369193323Sedvoid GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) { 370193323Sed // We do a bottom-up SCC traversal of the call graph. In other words, we 371193323Sed // visit all callees before callers (leaf-first). 372193323Sed for (scc_iterator<CallGraph*> I = scc_begin(&CG), E = scc_end(&CG); I != E; 373193323Sed ++I) { 374193323Sed std::vector<CallGraphNode *> &SCC = *I; 375193323Sed assert(!SCC.empty() && "SCC with no functions?"); 376193323Sed 377193323Sed if (!SCC[0]->getFunction()) { 378193323Sed // Calls externally - can't say anything useful. Remove any existing 379193323Sed // function records (may have been created when scanning globals). 380193323Sed for (unsigned i = 0, e = SCC.size(); i != e; ++i) 381193323Sed FunctionInfo.erase(SCC[i]->getFunction()); 382193323Sed continue; 383193323Sed } 384193323Sed 385193323Sed FunctionRecord &FR = FunctionInfo[SCC[0]->getFunction()]; 386193323Sed 387193323Sed bool KnowNothing = false; 388193323Sed unsigned FunctionEffect = 0; 389193323Sed 390193323Sed // Collect the mod/ref properties due to called functions. We only compute 391193323Sed // one mod-ref set. 392193323Sed for (unsigned i = 0, e = SCC.size(); i != e && !KnowNothing; ++i) { 393193323Sed Function *F = SCC[i]->getFunction(); 394193323Sed if (!F) { 395193323Sed KnowNothing = true; 396193323Sed break; 397193323Sed } 398193323Sed 399193323Sed if (F->isDeclaration()) { 400193323Sed // Try to get mod/ref behaviour from function attributes. 401193323Sed if (F->doesNotAccessMemory()) { 402193323Sed // Can't do better than that! 403193323Sed } else if (F->onlyReadsMemory()) { 404193323Sed FunctionEffect |= Ref; 405193323Sed if (!F->isIntrinsic()) 406193323Sed // This function might call back into the module and read a global - 407193323Sed // consider every global as possibly being read by this function. 408193323Sed FR.MayReadAnyGlobal = true; 409193323Sed } else { 410193323Sed FunctionEffect |= ModRef; 411193323Sed // Can't say anything useful unless it's an intrinsic - they don't 412193323Sed // read or write global variables of the kind considered here. 413193323Sed KnowNothing = !F->isIntrinsic(); 414193323Sed } 415193323Sed continue; 416193323Sed } 417193323Sed 418193323Sed for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end(); 419193323Sed CI != E && !KnowNothing; ++CI) 420193323Sed if (Function *Callee = CI->second->getFunction()) { 421193323Sed if (FunctionRecord *CalleeFR = getFunctionInfo(Callee)) { 422193323Sed // Propagate function effect up. 423193323Sed FunctionEffect |= CalleeFR->FunctionEffect; 424193323Sed 425193323Sed // Incorporate callee's effects on globals into our info. 426212904Sdim for (std::map<const GlobalValue*, unsigned>::iterator GI = 427193323Sed CalleeFR->GlobalInfo.begin(), E = CalleeFR->GlobalInfo.end(); 428193323Sed GI != E; ++GI) 429193323Sed FR.GlobalInfo[GI->first] |= GI->second; 430193323Sed FR.MayReadAnyGlobal |= CalleeFR->MayReadAnyGlobal; 431193323Sed } else { 432193323Sed // Can't say anything about it. However, if it is inside our SCC, 433193323Sed // then nothing needs to be done. 434193323Sed CallGraphNode *CalleeNode = CG[Callee]; 435193323Sed if (std::find(SCC.begin(), SCC.end(), CalleeNode) == SCC.end()) 436193323Sed KnowNothing = true; 437193323Sed } 438193323Sed } else { 439193323Sed KnowNothing = true; 440193323Sed } 441193323Sed } 442193323Sed 443193323Sed // If we can't say anything useful about this SCC, remove all SCC functions 444193323Sed // from the FunctionInfo map. 445193323Sed if (KnowNothing) { 446193323Sed for (unsigned i = 0, e = SCC.size(); i != e; ++i) 447193323Sed FunctionInfo.erase(SCC[i]->getFunction()); 448193323Sed continue; 449193323Sed } 450193323Sed 451193323Sed // Scan the function bodies for explicit loads or stores. 452193323Sed for (unsigned i = 0, e = SCC.size(); i != e && FunctionEffect != ModRef;++i) 453193323Sed for (inst_iterator II = inst_begin(SCC[i]->getFunction()), 454193323Sed E = inst_end(SCC[i]->getFunction()); 455193323Sed II != E && FunctionEffect != ModRef; ++II) 456193323Sed if (isa<LoadInst>(*II)) { 457193323Sed FunctionEffect |= Ref; 458193323Sed if (cast<LoadInst>(*II).isVolatile()) 459193323Sed // Volatile loads may have side-effects, so mark them as writing 460193323Sed // memory (for example, a flag inside the processor). 461193323Sed FunctionEffect |= Mod; 462193323Sed } else if (isa<StoreInst>(*II)) { 463193323Sed FunctionEffect |= Mod; 464193323Sed if (cast<StoreInst>(*II).isVolatile()) 465193323Sed // Treat volatile stores as reading memory somewhere. 466193323Sed FunctionEffect |= Ref; 467198892Srdivacky } else if (isMalloc(&cast<Instruction>(*II)) || 468198892Srdivacky isFreeCall(&cast<Instruction>(*II))) { 469193323Sed FunctionEffect |= ModRef; 470193323Sed } 471193323Sed 472193323Sed if ((FunctionEffect & Mod) == 0) 473193323Sed ++NumReadMemFunctions; 474193323Sed if (FunctionEffect == 0) 475193323Sed ++NumNoMemFunctions; 476193323Sed FR.FunctionEffect = FunctionEffect; 477193323Sed 478193323Sed // Finally, now that we know the full effect on this SCC, clone the 479193323Sed // information to each function in the SCC. 480193323Sed for (unsigned i = 1, e = SCC.size(); i != e; ++i) 481193323Sed FunctionInfo[SCC[i]->getFunction()] = FR; 482193323Sed } 483193323Sed} 484193323Sed 485193323Sed 486193323Sed 487193323Sed/// alias - If one of the pointers is to a global that we are tracking, and the 488193323Sed/// other is some random pointer, we know there cannot be an alias, because the 489193323Sed/// address of the global isn't taken. 490193323SedAliasAnalysis::AliasResult 491218893SdimGlobalsModRef::alias(const Location &LocA, 492218893Sdim const Location &LocB) { 493193323Sed // Get the base object these pointers point to. 494218893Sdim const Value *UV1 = GetUnderlyingObject(LocA.Ptr); 495218893Sdim const Value *UV2 = GetUnderlyingObject(LocB.Ptr); 496193323Sed 497193323Sed // If either of the underlying values is a global, they may be non-addr-taken 498193323Sed // globals, which we can answer queries about. 499212904Sdim const GlobalValue *GV1 = dyn_cast<GlobalValue>(UV1); 500212904Sdim const GlobalValue *GV2 = dyn_cast<GlobalValue>(UV2); 501193323Sed if (GV1 || GV2) { 502193323Sed // If the global's address is taken, pretend we don't know it's a pointer to 503193323Sed // the global. 504193323Sed if (GV1 && !NonAddressTakenGlobals.count(GV1)) GV1 = 0; 505193323Sed if (GV2 && !NonAddressTakenGlobals.count(GV2)) GV2 = 0; 506193323Sed 507203954Srdivacky // If the two pointers are derived from two different non-addr-taken 508193323Sed // globals, or if one is and the other isn't, we know these can't alias. 509193323Sed if ((GV1 || GV2) && GV1 != GV2) 510193323Sed return NoAlias; 511193323Sed 512193323Sed // Otherwise if they are both derived from the same addr-taken global, we 513193323Sed // can't know the two accesses don't overlap. 514193323Sed } 515193323Sed 516193323Sed // These pointers may be based on the memory owned by an indirect global. If 517193323Sed // so, we may be able to handle this. First check to see if the base pointer 518193323Sed // is a direct load from an indirect global. 519193323Sed GV1 = GV2 = 0; 520212904Sdim if (const LoadInst *LI = dyn_cast<LoadInst>(UV1)) 521193323Sed if (GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0))) 522193323Sed if (IndirectGlobals.count(GV)) 523193323Sed GV1 = GV; 524212904Sdim if (const LoadInst *LI = dyn_cast<LoadInst>(UV2)) 525212904Sdim if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0))) 526193323Sed if (IndirectGlobals.count(GV)) 527193323Sed GV2 = GV; 528193323Sed 529193323Sed // These pointers may also be from an allocation for the indirect global. If 530193323Sed // so, also handle them. 531193323Sed if (AllocsForIndirectGlobals.count(UV1)) 532193323Sed GV1 = AllocsForIndirectGlobals[UV1]; 533193323Sed if (AllocsForIndirectGlobals.count(UV2)) 534193323Sed GV2 = AllocsForIndirectGlobals[UV2]; 535193323Sed 536193323Sed // Now that we know whether the two pointers are related to indirect globals, 537193323Sed // use this to disambiguate the pointers. If either pointer is based on an 538193323Sed // indirect global and if they are not both based on the same indirect global, 539193323Sed // they cannot alias. 540193323Sed if ((GV1 || GV2) && GV1 != GV2) 541193323Sed return NoAlias; 542193323Sed 543218893Sdim return AliasAnalysis::alias(LocA, LocB); 544193323Sed} 545193323Sed 546193323SedAliasAnalysis::ModRefResult 547212904SdimGlobalsModRef::getModRefInfo(ImmutableCallSite CS, 548218893Sdim const Location &Loc) { 549193323Sed unsigned Known = ModRef; 550193323Sed 551193323Sed // If we are asking for mod/ref info of a direct call with a pointer to a 552193323Sed // global we are tracking, return information if we have it. 553218893Sdim if (const GlobalValue *GV = 554218893Sdim dyn_cast<GlobalValue>(GetUnderlyingObject(Loc.Ptr))) 555193323Sed if (GV->hasLocalLinkage()) 556212904Sdim if (const Function *F = CS.getCalledFunction()) 557193323Sed if (NonAddressTakenGlobals.count(GV)) 558212904Sdim if (const FunctionRecord *FR = getFunctionInfo(F)) 559193323Sed Known = FR->getInfoForGlobal(GV); 560193323Sed 561193323Sed if (Known == NoModRef) 562193323Sed return NoModRef; // No need to query other mod/ref analyses 563218893Sdim return ModRefResult(Known & AliasAnalysis::getModRefInfo(CS, Loc)); 564193323Sed} 565193323Sed 566193323Sed 567193323Sed//===----------------------------------------------------------------------===// 568193323Sed// Methods to update the analysis as a result of the client transformation. 569193323Sed// 570193323Sedvoid GlobalsModRef::deleteValue(Value *V) { 571193323Sed if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) { 572193323Sed if (NonAddressTakenGlobals.erase(GV)) { 573193323Sed // This global might be an indirect global. If so, remove it and remove 574193323Sed // any AllocRelatedValues for it. 575193323Sed if (IndirectGlobals.erase(GV)) { 576193323Sed // Remove any entries in AllocsForIndirectGlobals for this global. 577212904Sdim for (std::map<const Value*, const GlobalValue*>::iterator 578193323Sed I = AllocsForIndirectGlobals.begin(), 579193323Sed E = AllocsForIndirectGlobals.end(); I != E; ) { 580193323Sed if (I->second == GV) { 581193323Sed AllocsForIndirectGlobals.erase(I++); 582193323Sed } else { 583193323Sed ++I; 584193323Sed } 585193323Sed } 586193323Sed } 587193323Sed } 588193323Sed } 589193323Sed 590193323Sed // Otherwise, if this is an allocation related to an indirect global, remove 591193323Sed // it. 592193323Sed AllocsForIndirectGlobals.erase(V); 593193323Sed 594193323Sed AliasAnalysis::deleteValue(V); 595193323Sed} 596193323Sed 597193323Sedvoid GlobalsModRef::copyValue(Value *From, Value *To) { 598193323Sed AliasAnalysis::copyValue(From, To); 599193323Sed} 600218893Sdim 601218893Sdimvoid GlobalsModRef::addEscapingUse(Use &U) { 602218893Sdim // For the purposes of this analysis, it is conservatively correct to treat 603218893Sdim // a newly escaping value equivalently to a deleted one. We could perhaps 604218893Sdim // be more precise by processing the new use and attempting to update our 605218893Sdim // saved analysis results to accomodate it. 606218893Sdim deleteValue(U); 607218893Sdim 608218893Sdim AliasAnalysis::addEscapingUse(U); 609218893Sdim} 610