| //===- GlobalsModRef.cpp - Simple Mod/Ref Analysis for Globals ------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This simple pass provides alias and mod/ref information for global values |
| // that do not have their address taken, and keeps track of whether functions |
| // read or write memory (are "pure"). For this simple (but very common) case, |
| // we can provide pretty accurate and useful information. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "globalsmodref-aa" |
| #include "llvm/Analysis/Passes.h" |
| #include "llvm/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Constants.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/Analysis/CallGraph.h" |
| #include "llvm/Analysis/MemoryBuiltins.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/InstIterator.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/SCCIterator.h" |
| #include <set> |
| using namespace llvm; |
| |
| STATISTIC(NumNonAddrTakenGlobalVars, |
| "Number of global vars without address taken"); |
| STATISTIC(NumNonAddrTakenFunctions,"Number of functions without address taken"); |
| STATISTIC(NumNoMemFunctions, "Number of functions that do not access memory"); |
| STATISTIC(NumReadMemFunctions, "Number of functions that only read memory"); |
| STATISTIC(NumIndirectGlobalVars, "Number of indirect global objects"); |
| |
| namespace { |
| /// FunctionRecord - One instance of this structure is stored for every |
| /// function in the program. Later, the entries for these functions are |
| /// removed if the function is found to call an external function (in which |
| /// case we know nothing about it. |
| struct FunctionRecord { |
| /// GlobalInfo - Maintain mod/ref info for all of the globals without |
| /// addresses taken that are read or written (transitively) by this |
| /// function. |
| std::map<const GlobalValue*, unsigned> GlobalInfo; |
| |
| /// MayReadAnyGlobal - May read global variables, but it is not known which. |
| bool MayReadAnyGlobal; |
| |
| unsigned getInfoForGlobal(const GlobalValue *GV) const { |
| unsigned Effect = MayReadAnyGlobal ? AliasAnalysis::Ref : 0; |
| std::map<const GlobalValue*, unsigned>::const_iterator I = |
| GlobalInfo.find(GV); |
| if (I != GlobalInfo.end()) |
| Effect |= I->second; |
| return Effect; |
| } |
| |
| /// FunctionEffect - Capture whether or not this function reads or writes to |
| /// ANY memory. If not, we can do a lot of aggressive analysis on it. |
| unsigned FunctionEffect; |
| |
| FunctionRecord() : MayReadAnyGlobal (false), FunctionEffect(0) {} |
| }; |
| |
| /// GlobalsModRef - The actual analysis pass. |
| class GlobalsModRef : public ModulePass, public AliasAnalysis { |
| /// NonAddressTakenGlobals - The globals that do not have their addresses |
| /// taken. |
| std::set<const GlobalValue*> NonAddressTakenGlobals; |
| |
| /// IndirectGlobals - The memory pointed to by this global is known to be |
| /// 'owned' by the global. |
| std::set<const GlobalValue*> IndirectGlobals; |
| |
| /// AllocsForIndirectGlobals - If an instruction allocates memory for an |
| /// indirect global, this map indicates which one. |
| std::map<const Value*, const GlobalValue*> AllocsForIndirectGlobals; |
| |
| /// FunctionInfo - For each function, keep track of what globals are |
| /// modified or read. |
| std::map<const Function*, FunctionRecord> FunctionInfo; |
| |
| public: |
| static char ID; |
| GlobalsModRef() : ModulePass(ID) { |
| initializeGlobalsModRefPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| bool runOnModule(Module &M) { |
| InitializeAliasAnalysis(this); // set up super class |
| AnalyzeGlobals(M); // find non-addr taken globals |
| AnalyzeCallGraph(getAnalysis<CallGraph>(), M); // Propagate on CG |
| return false; |
| } |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AliasAnalysis::getAnalysisUsage(AU); |
| AU.addRequired<CallGraph>(); |
| AU.setPreservesAll(); // Does not transform code |
| } |
| |
| //------------------------------------------------ |
| // Implement the AliasAnalysis API |
| // |
| AliasResult alias(const Location &LocA, const Location &LocB); |
| ModRefResult getModRefInfo(ImmutableCallSite CS, |
| const Location &Loc); |
| ModRefResult getModRefInfo(ImmutableCallSite CS1, |
| ImmutableCallSite CS2) { |
| return AliasAnalysis::getModRefInfo(CS1, CS2); |
| } |
| |
| /// getModRefBehavior - Return the behavior of the specified function if |
| /// called from the specified call site. The call site may be null in which |
| /// case the most generic behavior of this function should be returned. |
| ModRefBehavior getModRefBehavior(const Function *F) { |
| ModRefBehavior Min = UnknownModRefBehavior; |
| |
| if (FunctionRecord *FR = getFunctionInfo(F)) { |
| if (FR->FunctionEffect == 0) |
| Min = DoesNotAccessMemory; |
| else if ((FR->FunctionEffect & Mod) == 0) |
| Min = OnlyReadsMemory; |
| } |
| |
| return ModRefBehavior(AliasAnalysis::getModRefBehavior(F) & Min); |
| } |
| |
| /// getModRefBehavior - Return the behavior of the specified function if |
| /// called from the specified call site. The call site may be null in which |
| /// case the most generic behavior of this function should be returned. |
| ModRefBehavior getModRefBehavior(ImmutableCallSite CS) { |
| ModRefBehavior Min = UnknownModRefBehavior; |
| |
| if (const Function* F = CS.getCalledFunction()) |
| if (FunctionRecord *FR = getFunctionInfo(F)) { |
| if (FR->FunctionEffect == 0) |
| Min = DoesNotAccessMemory; |
| else if ((FR->FunctionEffect & Mod) == 0) |
| Min = OnlyReadsMemory; |
| } |
| |
| return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min); |
| } |
| |
| virtual void deleteValue(Value *V); |
| virtual void copyValue(Value *From, Value *To); |
| virtual void addEscapingUse(Use &U); |
| |
| /// getAdjustedAnalysisPointer - This method is used when a pass implements |
| /// an analysis interface through multiple inheritance. If needed, it |
| /// should override this to adjust the this pointer as needed for the |
| /// specified pass info. |
| virtual void *getAdjustedAnalysisPointer(AnalysisID PI) { |
| if (PI == &AliasAnalysis::ID) |
| return (AliasAnalysis*)this; |
| return this; |
| } |
| |
| private: |
| /// getFunctionInfo - Return the function info for the function, or null if |
| /// we don't have anything useful to say about it. |
| FunctionRecord *getFunctionInfo(const Function *F) { |
| std::map<const Function*, FunctionRecord>::iterator I = |
| FunctionInfo.find(F); |
| if (I != FunctionInfo.end()) |
| return &I->second; |
| return 0; |
| } |
| |
| void AnalyzeGlobals(Module &M); |
| void AnalyzeCallGraph(CallGraph &CG, Module &M); |
| bool AnalyzeUsesOfPointer(Value *V, std::vector<Function*> &Readers, |
| std::vector<Function*> &Writers, |
| GlobalValue *OkayStoreDest = 0); |
| bool AnalyzeIndirectGlobalMemory(GlobalValue *GV); |
| }; |
| } |
| |
| char GlobalsModRef::ID = 0; |
| INITIALIZE_AG_PASS_BEGIN(GlobalsModRef, AliasAnalysis, |
| "globalsmodref-aa", "Simple mod/ref analysis for globals", |
| false, true, false) |
| INITIALIZE_AG_DEPENDENCY(CallGraph) |
| INITIALIZE_AG_PASS_END(GlobalsModRef, AliasAnalysis, |
| "globalsmodref-aa", "Simple mod/ref analysis for globals", |
| false, true, false) |
| |
| Pass *llvm::createGlobalsModRefPass() { return new GlobalsModRef(); } |
| |
| /// AnalyzeGlobals - Scan through the users of all of the internal |
| /// GlobalValue's in the program. If none of them have their "address taken" |
| /// (really, their address passed to something nontrivial), record this fact, |
| /// and record the functions that they are used directly in. |
| void GlobalsModRef::AnalyzeGlobals(Module &M) { |
| std::vector<Function*> Readers, Writers; |
| for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) |
| if (I->hasLocalLinkage()) { |
| if (!AnalyzeUsesOfPointer(I, Readers, Writers)) { |
| // Remember that we are tracking this global. |
| NonAddressTakenGlobals.insert(I); |
| ++NumNonAddrTakenFunctions; |
| } |
| Readers.clear(); Writers.clear(); |
| } |
| |
| for (Module::global_iterator I = M.global_begin(), E = M.global_end(); |
| I != E; ++I) |
| if (I->hasLocalLinkage()) { |
| if (!AnalyzeUsesOfPointer(I, Readers, Writers)) { |
| // Remember that we are tracking this global, and the mod/ref fns |
| NonAddressTakenGlobals.insert(I); |
| |
| for (unsigned i = 0, e = Readers.size(); i != e; ++i) |
| FunctionInfo[Readers[i]].GlobalInfo[I] |= Ref; |
| |
| if (!I->isConstant()) // No need to keep track of writers to constants |
| for (unsigned i = 0, e = Writers.size(); i != e; ++i) |
| FunctionInfo[Writers[i]].GlobalInfo[I] |= Mod; |
| ++NumNonAddrTakenGlobalVars; |
| |
| // If this global holds a pointer type, see if it is an indirect global. |
| if (I->getType()->getElementType()->isPointerTy() && |
| AnalyzeIndirectGlobalMemory(I)) |
| ++NumIndirectGlobalVars; |
| } |
| Readers.clear(); Writers.clear(); |
| } |
| } |
| |
| /// AnalyzeUsesOfPointer - Look at all of the users of the specified pointer. |
| /// If this is used by anything complex (i.e., the address escapes), return |
| /// true. Also, while we are at it, keep track of those functions that read and |
| /// write to the value. |
| /// |
| /// If OkayStoreDest is non-null, stores into this global are allowed. |
| bool GlobalsModRef::AnalyzeUsesOfPointer(Value *V, |
| std::vector<Function*> &Readers, |
| std::vector<Function*> &Writers, |
| GlobalValue *OkayStoreDest) { |
| if (!V->getType()->isPointerTy()) return true; |
| |
| for (Value::use_iterator UI = V->use_begin(), E=V->use_end(); UI != E; ++UI) { |
| User *U = *UI; |
| if (LoadInst *LI = dyn_cast<LoadInst>(U)) { |
| Readers.push_back(LI->getParent()->getParent()); |
| } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { |
| if (V == SI->getOperand(1)) { |
| Writers.push_back(SI->getParent()->getParent()); |
| } else if (SI->getOperand(1) != OkayStoreDest) { |
| return true; // Storing the pointer |
| } |
| } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { |
| if (AnalyzeUsesOfPointer(GEP, Readers, Writers)) return true; |
| } else if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { |
| if (AnalyzeUsesOfPointer(BCI, Readers, Writers, OkayStoreDest)) |
| return true; |
| } else if (isFreeCall(U)) { |
| Writers.push_back(cast<Instruction>(U)->getParent()->getParent()); |
| } else if (CallInst *CI = dyn_cast<CallInst>(U)) { |
| // Make sure that this is just the function being called, not that it is |
| // passing into the function. |
| for (unsigned i = 0, e = CI->getNumArgOperands(); i != e; ++i) |
| if (CI->getArgOperand(i) == V) return true; |
| } else if (InvokeInst *II = dyn_cast<InvokeInst>(U)) { |
| // Make sure that this is just the function being called, not that it is |
| // passing into the function. |
| for (unsigned i = 0, e = II->getNumArgOperands(); i != e; ++i) |
| if (II->getArgOperand(i) == V) return true; |
| } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { |
| if (CE->getOpcode() == Instruction::GetElementPtr || |
| CE->getOpcode() == Instruction::BitCast) { |
| if (AnalyzeUsesOfPointer(CE, Readers, Writers)) |
| return true; |
| } else { |
| return true; |
| } |
| } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(U)) { |
| if (!isa<ConstantPointerNull>(ICI->getOperand(1))) |
| return true; // Allow comparison against null. |
| } else { |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /// AnalyzeIndirectGlobalMemory - We found an non-address-taken global variable |
| /// which holds a pointer type. See if the global always points to non-aliased |
| /// heap memory: that is, all initializers of the globals are allocations, and |
| /// those allocations have no use other than initialization of the global. |
| /// Further, all loads out of GV must directly use the memory, not store the |
| /// pointer somewhere. If this is true, we consider the memory pointed to by |
| /// GV to be owned by GV and can disambiguate other pointers from it. |
| bool GlobalsModRef::AnalyzeIndirectGlobalMemory(GlobalValue *GV) { |
| // Keep track of values related to the allocation of the memory, f.e. the |
| // value produced by the malloc call and any casts. |
| std::vector<Value*> AllocRelatedValues; |
| |
| // Walk the user list of the global. If we find anything other than a direct |
| // load or store, bail out. |
| for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){ |
| User *U = *I; |
| if (LoadInst *LI = dyn_cast<LoadInst>(U)) { |
| // The pointer loaded from the global can only be used in simple ways: |
| // we allow addressing of it and loading storing to it. We do *not* allow |
| // storing the loaded pointer somewhere else or passing to a function. |
| std::vector<Function*> ReadersWriters; |
| if (AnalyzeUsesOfPointer(LI, ReadersWriters, ReadersWriters)) |
| return false; // Loaded pointer escapes. |
| // TODO: Could try some IP mod/ref of the loaded pointer. |
| } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { |
| // Storing the global itself. |
| if (SI->getOperand(0) == GV) return false; |
| |
| // If storing the null pointer, ignore it. |
| if (isa<ConstantPointerNull>(SI->getOperand(0))) |
| continue; |
| |
| // Check the value being stored. |
| Value *Ptr = GetUnderlyingObject(SI->getOperand(0)); |
| |
| if (isMalloc(Ptr)) { |
| // Okay, easy case. |
| } else if (CallInst *CI = dyn_cast<CallInst>(Ptr)) { |
| Function *F = CI->getCalledFunction(); |
| if (!F || !F->isDeclaration()) return false; // Too hard to analyze. |
| if (F->getName() != "calloc") return false; // Not calloc. |
| } else { |
| return false; // Too hard to analyze. |
| } |
| |
| // Analyze all uses of the allocation. If any of them are used in a |
| // non-simple way (e.g. stored to another global) bail out. |
| std::vector<Function*> ReadersWriters; |
| if (AnalyzeUsesOfPointer(Ptr, ReadersWriters, ReadersWriters, GV)) |
| return false; // Loaded pointer escapes. |
| |
| // Remember that this allocation is related to the indirect global. |
| AllocRelatedValues.push_back(Ptr); |
| } else { |
| // Something complex, bail out. |
| return false; |
| } |
| } |
| |
| // Okay, this is an indirect global. Remember all of the allocations for |
| // this global in AllocsForIndirectGlobals. |
| while (!AllocRelatedValues.empty()) { |
| AllocsForIndirectGlobals[AllocRelatedValues.back()] = GV; |
| AllocRelatedValues.pop_back(); |
| } |
| IndirectGlobals.insert(GV); |
| return true; |
| } |
| |
| /// AnalyzeCallGraph - At this point, we know the functions where globals are |
| /// immediately stored to and read from. Propagate this information up the call |
| /// graph to all callers and compute the mod/ref info for all memory for each |
| /// function. |
| void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) { |
| // We do a bottom-up SCC traversal of the call graph. In other words, we |
| // visit all callees before callers (leaf-first). |
| for (scc_iterator<CallGraph*> I = scc_begin(&CG), E = scc_end(&CG); I != E; |
| ++I) { |
| std::vector<CallGraphNode *> &SCC = *I; |
| assert(!SCC.empty() && "SCC with no functions?"); |
| |
| if (!SCC[0]->getFunction()) { |
| // Calls externally - can't say anything useful. Remove any existing |
| // function records (may have been created when scanning globals). |
| for (unsigned i = 0, e = SCC.size(); i != e; ++i) |
| FunctionInfo.erase(SCC[i]->getFunction()); |
| continue; |
| } |
| |
| FunctionRecord &FR = FunctionInfo[SCC[0]->getFunction()]; |
| |
| bool KnowNothing = false; |
| unsigned FunctionEffect = 0; |
| |
| // Collect the mod/ref properties due to called functions. We only compute |
| // one mod-ref set. |
| for (unsigned i = 0, e = SCC.size(); i != e && !KnowNothing; ++i) { |
| Function *F = SCC[i]->getFunction(); |
| if (!F) { |
| KnowNothing = true; |
| break; |
| } |
| |
| if (F->isDeclaration()) { |
| // Try to get mod/ref behaviour from function attributes. |
| if (F->doesNotAccessMemory()) { |
| // Can't do better than that! |
| } else if (F->onlyReadsMemory()) { |
| FunctionEffect |= Ref; |
| if (!F->isIntrinsic()) |
| // This function might call back into the module and read a global - |
| // consider every global as possibly being read by this function. |
| FR.MayReadAnyGlobal = true; |
| } else { |
| FunctionEffect |= ModRef; |
| // Can't say anything useful unless it's an intrinsic - they don't |
| // read or write global variables of the kind considered here. |
| KnowNothing = !F->isIntrinsic(); |
| } |
| continue; |
| } |
| |
| for (CallGraphNode::iterator CI = SCC[i]->begin(), E = SCC[i]->end(); |
| CI != E && !KnowNothing; ++CI) |
| if (Function *Callee = CI->second->getFunction()) { |
| if (FunctionRecord *CalleeFR = getFunctionInfo(Callee)) { |
| // Propagate function effect up. |
| FunctionEffect |= CalleeFR->FunctionEffect; |
| |
| // Incorporate callee's effects on globals into our info. |
| for (std::map<const GlobalValue*, unsigned>::iterator GI = |
| CalleeFR->GlobalInfo.begin(), E = CalleeFR->GlobalInfo.end(); |
| GI != E; ++GI) |
| FR.GlobalInfo[GI->first] |= GI->second; |
| FR.MayReadAnyGlobal |= CalleeFR->MayReadAnyGlobal; |
| } else { |
| // Can't say anything about it. However, if it is inside our SCC, |
| // then nothing needs to be done. |
| CallGraphNode *CalleeNode = CG[Callee]; |
| if (std::find(SCC.begin(), SCC.end(), CalleeNode) == SCC.end()) |
| KnowNothing = true; |
| } |
| } else { |
| KnowNothing = true; |
| } |
| } |
| |
| // If we can't say anything useful about this SCC, remove all SCC functions |
| // from the FunctionInfo map. |
| if (KnowNothing) { |
| for (unsigned i = 0, e = SCC.size(); i != e; ++i) |
| FunctionInfo.erase(SCC[i]->getFunction()); |
| continue; |
| } |
| |
| // Scan the function bodies for explicit loads or stores. |
| for (unsigned i = 0, e = SCC.size(); i != e && FunctionEffect != ModRef;++i) |
| for (inst_iterator II = inst_begin(SCC[i]->getFunction()), |
| E = inst_end(SCC[i]->getFunction()); |
| II != E && FunctionEffect != ModRef; ++II) |
| if (isa<LoadInst>(*II)) { |
| FunctionEffect |= Ref; |
| if (cast<LoadInst>(*II).isVolatile()) |
| // Volatile loads may have side-effects, so mark them as writing |
| // memory (for example, a flag inside the processor). |
| FunctionEffect |= Mod; |
| } else if (isa<StoreInst>(*II)) { |
| FunctionEffect |= Mod; |
| if (cast<StoreInst>(*II).isVolatile()) |
| // Treat volatile stores as reading memory somewhere. |
| FunctionEffect |= Ref; |
| } else if (isMalloc(&cast<Instruction>(*II)) || |
| isFreeCall(&cast<Instruction>(*II))) { |
| FunctionEffect |= ModRef; |
| } else if (IntrinsicInst *Intrinsic = dyn_cast<IntrinsicInst>(&*II)) { |
| // The callgraph doesn't include intrinsic calls. |
| Function *Callee = Intrinsic->getCalledFunction(); |
| ModRefBehavior Behaviour = AliasAnalysis::getModRefBehavior(Callee); |
| FunctionEffect |= (Behaviour & ModRef); |
| } |
| |
| if ((FunctionEffect & Mod) == 0) |
| ++NumReadMemFunctions; |
| if (FunctionEffect == 0) |
| ++NumNoMemFunctions; |
| FR.FunctionEffect = FunctionEffect; |
| |
| // Finally, now that we know the full effect on this SCC, clone the |
| // information to each function in the SCC. |
| for (unsigned i = 1, e = SCC.size(); i != e; ++i) |
| FunctionInfo[SCC[i]->getFunction()] = FR; |
| } |
| } |
| |
| |
| |
| /// alias - If one of the pointers is to a global that we are tracking, and the |
| /// other is some random pointer, we know there cannot be an alias, because the |
| /// address of the global isn't taken. |
| AliasAnalysis::AliasResult |
| GlobalsModRef::alias(const Location &LocA, |
| const Location &LocB) { |
| // Get the base object these pointers point to. |
| const Value *UV1 = GetUnderlyingObject(LocA.Ptr); |
| const Value *UV2 = GetUnderlyingObject(LocB.Ptr); |
| |
| // If either of the underlying values is a global, they may be non-addr-taken |
| // globals, which we can answer queries about. |
| const GlobalValue *GV1 = dyn_cast<GlobalValue>(UV1); |
| const GlobalValue *GV2 = dyn_cast<GlobalValue>(UV2); |
| if (GV1 || GV2) { |
| // If the global's address is taken, pretend we don't know it's a pointer to |
| // the global. |
| if (GV1 && !NonAddressTakenGlobals.count(GV1)) GV1 = 0; |
| if (GV2 && !NonAddressTakenGlobals.count(GV2)) GV2 = 0; |
| |
| // If the two pointers are derived from two different non-addr-taken |
| // globals, or if one is and the other isn't, we know these can't alias. |
| if ((GV1 || GV2) && GV1 != GV2) |
| return NoAlias; |
| |
| // Otherwise if they are both derived from the same addr-taken global, we |
| // can't know the two accesses don't overlap. |
| } |
| |
| // These pointers may be based on the memory owned by an indirect global. If |
| // so, we may be able to handle this. First check to see if the base pointer |
| // is a direct load from an indirect global. |
| GV1 = GV2 = 0; |
| if (const LoadInst *LI = dyn_cast<LoadInst>(UV1)) |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0))) |
| if (IndirectGlobals.count(GV)) |
| GV1 = GV; |
| if (const LoadInst *LI = dyn_cast<LoadInst>(UV2)) |
| if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(LI->getOperand(0))) |
| if (IndirectGlobals.count(GV)) |
| GV2 = GV; |
| |
| // These pointers may also be from an allocation for the indirect global. If |
| // so, also handle them. |
| if (AllocsForIndirectGlobals.count(UV1)) |
| GV1 = AllocsForIndirectGlobals[UV1]; |
| if (AllocsForIndirectGlobals.count(UV2)) |
| GV2 = AllocsForIndirectGlobals[UV2]; |
| |
| // Now that we know whether the two pointers are related to indirect globals, |
| // use this to disambiguate the pointers. If either pointer is based on an |
| // indirect global and if they are not both based on the same indirect global, |
| // they cannot alias. |
| if ((GV1 || GV2) && GV1 != GV2) |
| return NoAlias; |
| |
| return AliasAnalysis::alias(LocA, LocB); |
| } |
| |
| AliasAnalysis::ModRefResult |
| GlobalsModRef::getModRefInfo(ImmutableCallSite CS, |
| const Location &Loc) { |
| unsigned Known = ModRef; |
| |
| // If we are asking for mod/ref info of a direct call with a pointer to a |
| // global we are tracking, return information if we have it. |
| if (const GlobalValue *GV = |
| dyn_cast<GlobalValue>(GetUnderlyingObject(Loc.Ptr))) |
| if (GV->hasLocalLinkage()) |
| if (const Function *F = CS.getCalledFunction()) |
| if (NonAddressTakenGlobals.count(GV)) |
| if (const FunctionRecord *FR = getFunctionInfo(F)) |
| Known = FR->getInfoForGlobal(GV); |
| |
| if (Known == NoModRef) |
| return NoModRef; // No need to query other mod/ref analyses |
| return ModRefResult(Known & AliasAnalysis::getModRefInfo(CS, Loc)); |
| } |
| |
| |
| //===----------------------------------------------------------------------===// |
| // Methods to update the analysis as a result of the client transformation. |
| // |
| void GlobalsModRef::deleteValue(Value *V) { |
| if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) { |
| if (NonAddressTakenGlobals.erase(GV)) { |
| // This global might be an indirect global. If so, remove it and remove |
| // any AllocRelatedValues for it. |
| if (IndirectGlobals.erase(GV)) { |
| // Remove any entries in AllocsForIndirectGlobals for this global. |
| for (std::map<const Value*, const GlobalValue*>::iterator |
| I = AllocsForIndirectGlobals.begin(), |
| E = AllocsForIndirectGlobals.end(); I != E; ) { |
| if (I->second == GV) { |
| AllocsForIndirectGlobals.erase(I++); |
| } else { |
| ++I; |
| } |
| } |
| } |
| } |
| } |
| |
| // Otherwise, if this is an allocation related to an indirect global, remove |
| // it. |
| AllocsForIndirectGlobals.erase(V); |
| |
| AliasAnalysis::deleteValue(V); |
| } |
| |
| void GlobalsModRef::copyValue(Value *From, Value *To) { |
| AliasAnalysis::copyValue(From, To); |
| } |
| |
| void GlobalsModRef::addEscapingUse(Use &U) { |
| // For the purposes of this analysis, it is conservatively correct to treat |
| // a newly escaping value equivalently to a deleted one. We could perhaps |
| // be more precise by processing the new use and attempting to update our |
| // saved analysis results to accommodate it. |
| deleteValue(U); |
| |
| AliasAnalysis::addEscapingUse(U); |
| } |
