LLVM API Documentation

FunctionAttrs.cpp
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00001 //===- FunctionAttrs.cpp - Pass which marks functions attributes ----------===//
00002 //
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file is distributed under the University of Illinois Open Source
00006 // License. See LICENSE.TXT for details.
00007 //
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file implements a simple interprocedural pass which walks the
00011 // call-graph, looking for functions which do not access or only read
00012 // non-local memory, and marking them readnone/readonly.  It does the
00013 // same with function arguments independently, marking them readonly/
00014 // readnone/nocapture.  Finally, well-known library call declarations
00015 // are marked with all attributes that are consistent with the
00016 // function's standard definition. This pass is implemented as a
00017 // bottom-up traversal of the call-graph.
00018 //
00019 //===----------------------------------------------------------------------===//
00020 
00021 #include "llvm/Transforms/IPO.h"
00022 #include "llvm/ADT/SCCIterator.h"
00023 #include "llvm/ADT/SetVector.h"
00024 #include "llvm/ADT/SmallSet.h"
00025 #include "llvm/ADT/Statistic.h"
00026 #include "llvm/Analysis/AliasAnalysis.h"
00027 #include "llvm/Analysis/CallGraph.h"
00028 #include "llvm/Analysis/CallGraphSCCPass.h"
00029 #include "llvm/Analysis/CaptureTracking.h"
00030 #include "llvm/IR/GlobalVariable.h"
00031 #include "llvm/IR/InstIterator.h"
00032 #include "llvm/IR/IntrinsicInst.h"
00033 #include "llvm/IR/LLVMContext.h"
00034 #include "llvm/Target/TargetLibraryInfo.h"
00035 using namespace llvm;
00036 
00037 #define DEBUG_TYPE "functionattrs"
00038 
00039 STATISTIC(NumReadNone, "Number of functions marked readnone");
00040 STATISTIC(NumReadOnly, "Number of functions marked readonly");
00041 STATISTIC(NumNoCapture, "Number of arguments marked nocapture");
00042 STATISTIC(NumReadNoneArg, "Number of arguments marked readnone");
00043 STATISTIC(NumReadOnlyArg, "Number of arguments marked readonly");
00044 STATISTIC(NumNoAlias, "Number of function returns marked noalias");
00045 STATISTIC(NumAnnotated, "Number of attributes added to library functions");
00046 
00047 namespace {
00048   struct FunctionAttrs : public CallGraphSCCPass {
00049     static char ID; // Pass identification, replacement for typeid
00050     FunctionAttrs() : CallGraphSCCPass(ID), AA(nullptr) {
00051       initializeFunctionAttrsPass(*PassRegistry::getPassRegistry());
00052     }
00053 
00054     // runOnSCC - Analyze the SCC, performing the transformation if possible.
00055     bool runOnSCC(CallGraphSCC &SCC) override;
00056 
00057     // AddReadAttrs - Deduce readonly/readnone attributes for the SCC.
00058     bool AddReadAttrs(const CallGraphSCC &SCC);
00059 
00060     // AddArgumentAttrs - Deduce nocapture attributes for the SCC.
00061     bool AddArgumentAttrs(const CallGraphSCC &SCC);
00062 
00063     // IsFunctionMallocLike - Does this function allocate new memory?
00064     bool IsFunctionMallocLike(Function *F,
00065                               SmallPtrSet<Function*, 8> &) const;
00066 
00067     // AddNoAliasAttrs - Deduce noalias attributes for the SCC.
00068     bool AddNoAliasAttrs(const CallGraphSCC &SCC);
00069 
00070     // Utility methods used by inferPrototypeAttributes to add attributes
00071     // and maintain annotation statistics.
00072 
00073     void setDoesNotAccessMemory(Function &F) {
00074       if (!F.doesNotAccessMemory()) {
00075         F.setDoesNotAccessMemory();
00076         ++NumAnnotated;
00077       }
00078     }
00079 
00080     void setOnlyReadsMemory(Function &F) {
00081       if (!F.onlyReadsMemory()) {
00082         F.setOnlyReadsMemory();
00083         ++NumAnnotated;
00084       }
00085     }
00086 
00087     void setDoesNotThrow(Function &F) {
00088       if (!F.doesNotThrow()) {
00089         F.setDoesNotThrow();
00090         ++NumAnnotated;
00091       }
00092     }
00093 
00094     void setDoesNotCapture(Function &F, unsigned n) {
00095       if (!F.doesNotCapture(n)) {
00096         F.setDoesNotCapture(n);
00097         ++NumAnnotated;
00098       }
00099     }
00100 
00101     void setOnlyReadsMemory(Function &F, unsigned n) {
00102       if (!F.onlyReadsMemory(n)) {
00103         F.setOnlyReadsMemory(n);
00104         ++NumAnnotated;
00105       }
00106     }
00107 
00108     void setDoesNotAlias(Function &F, unsigned n) {
00109       if (!F.doesNotAlias(n)) {
00110         F.setDoesNotAlias(n);
00111         ++NumAnnotated;
00112       }
00113     }
00114 
00115     // inferPrototypeAttributes - Analyze the name and prototype of the
00116     // given function and set any applicable attributes.  Returns true
00117     // if any attributes were set and false otherwise.
00118     bool inferPrototypeAttributes(Function &F);
00119 
00120     // annotateLibraryCalls - Adds attributes to well-known standard library
00121     // call declarations.
00122     bool annotateLibraryCalls(const CallGraphSCC &SCC);
00123 
00124     void getAnalysisUsage(AnalysisUsage &AU) const override {
00125       AU.setPreservesCFG();
00126       AU.addRequired<AliasAnalysis>();
00127       AU.addRequired<TargetLibraryInfo>();
00128       CallGraphSCCPass::getAnalysisUsage(AU);
00129     }
00130 
00131   private:
00132     AliasAnalysis *AA;
00133     TargetLibraryInfo *TLI;
00134   };
00135 }
00136 
00137 char FunctionAttrs::ID = 0;
00138 INITIALIZE_PASS_BEGIN(FunctionAttrs, "functionattrs",
00139                 "Deduce function attributes", false, false)
00140 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
00141 INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
00142 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
00143 INITIALIZE_PASS_END(FunctionAttrs, "functionattrs",
00144                 "Deduce function attributes", false, false)
00145 
00146 Pass *llvm::createFunctionAttrsPass() { return new FunctionAttrs(); }
00147 
00148 
00149 /// AddReadAttrs - Deduce readonly/readnone attributes for the SCC.
00150 bool FunctionAttrs::AddReadAttrs(const CallGraphSCC &SCC) {
00151   SmallPtrSet<Function*, 8> SCCNodes;
00152 
00153   // Fill SCCNodes with the elements of the SCC.  Used for quickly
00154   // looking up whether a given CallGraphNode is in this SCC.
00155   for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I)
00156     SCCNodes.insert((*I)->getFunction());
00157 
00158   // Check if any of the functions in the SCC read or write memory.  If they
00159   // write memory then they can't be marked readnone or readonly.
00160   bool ReadsMemory = false;
00161   for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
00162     Function *F = (*I)->getFunction();
00163 
00164     if (!F || F->hasFnAttribute(Attribute::OptimizeNone))
00165       // External node or node we don't want to optimize - assume it may write
00166       // memory and give up.
00167       return false;
00168 
00169     AliasAnalysis::ModRefBehavior MRB = AA->getModRefBehavior(F);
00170     if (MRB == AliasAnalysis::DoesNotAccessMemory)
00171       // Already perfect!
00172       continue;
00173 
00174     // Definitions with weak linkage may be overridden at linktime with
00175     // something that writes memory, so treat them like declarations.
00176     if (F->isDeclaration() || F->mayBeOverridden()) {
00177       if (!AliasAnalysis::onlyReadsMemory(MRB))
00178         // May write memory.  Just give up.
00179         return false;
00180 
00181       ReadsMemory = true;
00182       continue;
00183     }
00184 
00185     // Scan the function body for instructions that may read or write memory.
00186     for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) {
00187       Instruction *I = &*II;
00188 
00189       // Some instructions can be ignored even if they read or write memory.
00190       // Detect these now, skipping to the next instruction if one is found.
00191       CallSite CS(cast<Value>(I));
00192       if (CS) {
00193         // Ignore calls to functions in the same SCC.
00194         if (CS.getCalledFunction() && SCCNodes.count(CS.getCalledFunction()))
00195           continue;
00196         AliasAnalysis::ModRefBehavior MRB = AA->getModRefBehavior(CS);
00197         // If the call doesn't access arbitrary memory, we may be able to
00198         // figure out something.
00199         if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
00200           // If the call does access argument pointees, check each argument.
00201           if (AliasAnalysis::doesAccessArgPointees(MRB))
00202             // Check whether all pointer arguments point to local memory, and
00203             // ignore calls that only access local memory.
00204             for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
00205                  CI != CE; ++CI) {
00206               Value *Arg = *CI;
00207               if (Arg->getType()->isPointerTy()) {
00208                 AAMDNodes AAInfo;
00209                 I->getAAMetadata(AAInfo);
00210 
00211                 AliasAnalysis::Location Loc(Arg,
00212                                             AliasAnalysis::UnknownSize, AAInfo);
00213                 if (!AA->pointsToConstantMemory(Loc, /*OrLocal=*/true)) {
00214                   if (MRB & AliasAnalysis::Mod)
00215                     // Writes non-local memory.  Give up.
00216                     return false;
00217                   if (MRB & AliasAnalysis::Ref)
00218                     // Ok, it reads non-local memory.
00219                     ReadsMemory = true;
00220                 }
00221               }
00222             }
00223           continue;
00224         }
00225         // The call could access any memory. If that includes writes, give up.
00226         if (MRB & AliasAnalysis::Mod)
00227           return false;
00228         // If it reads, note it.
00229         if (MRB & AliasAnalysis::Ref)
00230           ReadsMemory = true;
00231         continue;
00232       } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
00233         // Ignore non-volatile loads from local memory. (Atomic is okay here.)
00234         if (!LI->isVolatile()) {
00235           AliasAnalysis::Location Loc = AA->getLocation(LI);
00236           if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
00237             continue;
00238         }
00239       } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
00240         // Ignore non-volatile stores to local memory. (Atomic is okay here.)
00241         if (!SI->isVolatile()) {
00242           AliasAnalysis::Location Loc = AA->getLocation(SI);
00243           if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
00244             continue;
00245         }
00246       } else if (VAArgInst *VI = dyn_cast<VAArgInst>(I)) {
00247         // Ignore vaargs on local memory.
00248         AliasAnalysis::Location Loc = AA->getLocation(VI);
00249         if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
00250           continue;
00251       }
00252 
00253       // Any remaining instructions need to be taken seriously!  Check if they
00254       // read or write memory.
00255       if (I->mayWriteToMemory())
00256         // Writes memory.  Just give up.
00257         return false;
00258 
00259       // If this instruction may read memory, remember that.
00260       ReadsMemory |= I->mayReadFromMemory();
00261     }
00262   }
00263 
00264   // Success!  Functions in this SCC do not access memory, or only read memory.
00265   // Give them the appropriate attribute.
00266   bool MadeChange = false;
00267   for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
00268     Function *F = (*I)->getFunction();
00269 
00270     if (F->doesNotAccessMemory())
00271       // Already perfect!
00272       continue;
00273 
00274     if (F->onlyReadsMemory() && ReadsMemory)
00275       // No change.
00276       continue;
00277 
00278     MadeChange = true;
00279 
00280     // Clear out any existing attributes.
00281     AttrBuilder B;
00282     B.addAttribute(Attribute::ReadOnly)
00283       .addAttribute(Attribute::ReadNone);
00284     F->removeAttributes(AttributeSet::FunctionIndex,
00285                         AttributeSet::get(F->getContext(),
00286                                           AttributeSet::FunctionIndex, B));
00287 
00288     // Add in the new attribute.
00289     F->addAttribute(AttributeSet::FunctionIndex,
00290                     ReadsMemory ? Attribute::ReadOnly : Attribute::ReadNone);
00291 
00292     if (ReadsMemory)
00293       ++NumReadOnly;
00294     else
00295       ++NumReadNone;
00296   }
00297 
00298   return MadeChange;
00299 }
00300 
00301 namespace {
00302   // For a given pointer Argument, this retains a list of Arguments of functions
00303   // in the same SCC that the pointer data flows into. We use this to build an
00304   // SCC of the arguments.
00305   struct ArgumentGraphNode {
00306     Argument *Definition;
00307     SmallVector<ArgumentGraphNode*, 4> Uses;
00308   };
00309 
00310   class ArgumentGraph {
00311     // We store pointers to ArgumentGraphNode objects, so it's important that
00312     // that they not move around upon insert.
00313     typedef std::map<Argument*, ArgumentGraphNode> ArgumentMapTy;
00314 
00315     ArgumentMapTy ArgumentMap;
00316 
00317     // There is no root node for the argument graph, in fact:
00318     //   void f(int *x, int *y) { if (...) f(x, y); }
00319     // is an example where the graph is disconnected. The SCCIterator requires a
00320     // single entry point, so we maintain a fake ("synthetic") root node that
00321     // uses every node. Because the graph is directed and nothing points into
00322     // the root, it will not participate in any SCCs (except for its own).
00323     ArgumentGraphNode SyntheticRoot;
00324 
00325   public:
00326     ArgumentGraph() { SyntheticRoot.Definition = nullptr; }
00327 
00328     typedef SmallVectorImpl<ArgumentGraphNode*>::iterator iterator;
00329 
00330     iterator begin() { return SyntheticRoot.Uses.begin(); }
00331     iterator end() { return SyntheticRoot.Uses.end(); }
00332     ArgumentGraphNode *getEntryNode() { return &SyntheticRoot; }
00333 
00334     ArgumentGraphNode *operator[](Argument *A) {
00335       ArgumentGraphNode &Node = ArgumentMap[A];
00336       Node.Definition = A;
00337       SyntheticRoot.Uses.push_back(&Node);
00338       return &Node;
00339     }
00340   };
00341 
00342   // This tracker checks whether callees are in the SCC, and if so it does not
00343   // consider that a capture, instead adding it to the "Uses" list and
00344   // continuing with the analysis.
00345   struct ArgumentUsesTracker : public CaptureTracker {
00346     ArgumentUsesTracker(const SmallPtrSet<Function*, 8> &SCCNodes)
00347       : Captured(false), SCCNodes(SCCNodes) {}
00348 
00349     void tooManyUses() override { Captured = true; }
00350 
00351     bool captured(const Use *U) override {
00352       CallSite CS(U->getUser());
00353       if (!CS.getInstruction()) { Captured = true; return true; }
00354 
00355       Function *F = CS.getCalledFunction();
00356       if (!F || !SCCNodes.count(F)) { Captured = true; return true; }
00357 
00358       bool Found = false;
00359       Function::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
00360       for (CallSite::arg_iterator PI = CS.arg_begin(), PE = CS.arg_end();
00361            PI != PE; ++PI, ++AI) {
00362         if (AI == AE) {
00363           assert(F->isVarArg() && "More params than args in non-varargs call");
00364           Captured = true;
00365           return true;
00366         }
00367         if (PI == U) {
00368           Uses.push_back(AI);
00369           Found = true;
00370           break;
00371         }
00372       }
00373       assert(Found && "Capturing call-site captured nothing?");
00374       (void)Found;
00375       return false;
00376     }
00377 
00378     bool Captured;  // True only if certainly captured (used outside our SCC).
00379     SmallVector<Argument*, 4> Uses;  // Uses within our SCC.
00380 
00381     const SmallPtrSet<Function*, 8> &SCCNodes;
00382   };
00383 }
00384 
00385 namespace llvm {
00386   template<> struct GraphTraits<ArgumentGraphNode*> {
00387     typedef ArgumentGraphNode NodeType;
00388     typedef SmallVectorImpl<ArgumentGraphNode*>::iterator ChildIteratorType;
00389 
00390     static inline NodeType *getEntryNode(NodeType *A) { return A; }
00391     static inline ChildIteratorType child_begin(NodeType *N) {
00392       return N->Uses.begin();
00393     }
00394     static inline ChildIteratorType child_end(NodeType *N) {
00395       return N->Uses.end();
00396     }
00397   };
00398   template<> struct GraphTraits<ArgumentGraph*>
00399     : public GraphTraits<ArgumentGraphNode*> {
00400     static NodeType *getEntryNode(ArgumentGraph *AG) {
00401       return AG->getEntryNode();
00402     }
00403     static ChildIteratorType nodes_begin(ArgumentGraph *AG) {
00404       return AG->begin();
00405     }
00406     static ChildIteratorType nodes_end(ArgumentGraph *AG) {
00407       return AG->end();
00408     }
00409   };
00410 }
00411 
00412 // Returns Attribute::None, Attribute::ReadOnly or Attribute::ReadNone.
00413 static Attribute::AttrKind
00414 determinePointerReadAttrs(Argument *A,
00415                           const SmallPtrSet<Argument*, 8> &SCCNodes) {
00416                                                        
00417   SmallVector<Use*, 32> Worklist;
00418   SmallSet<Use*, 32> Visited;
00419   int Count = 0;
00420 
00421   // inalloca arguments are always clobbered by the call.
00422   if (A->hasInAllocaAttr())
00423     return Attribute::None;
00424 
00425   bool IsRead = false;
00426   // We don't need to track IsWritten. If A is written to, return immediately.
00427 
00428   for (Use &U : A->uses()) {
00429     if (Count++ >= 20)
00430       return Attribute::None;
00431 
00432     Visited.insert(&U);
00433     Worklist.push_back(&U);
00434   }
00435 
00436   while (!Worklist.empty()) {
00437     Use *U = Worklist.pop_back_val();
00438     Instruction *I = cast<Instruction>(U->getUser());
00439     Value *V = U->get();
00440 
00441     switch (I->getOpcode()) {
00442     case Instruction::BitCast:
00443     case Instruction::GetElementPtr:
00444     case Instruction::PHI:
00445     case Instruction::Select:
00446     case Instruction::AddrSpaceCast:
00447       // The original value is not read/written via this if the new value isn't.
00448       for (Use &UU : I->uses())
00449         if (Visited.insert(&UU).second)
00450           Worklist.push_back(&UU);
00451       break;
00452 
00453     case Instruction::Call:
00454     case Instruction::Invoke: {
00455       bool Captures = true;
00456 
00457       if (I->getType()->isVoidTy())
00458         Captures = false;
00459 
00460       auto AddUsersToWorklistIfCapturing = [&] {
00461         if (Captures)
00462           for (Use &UU : I->uses())
00463             if (Visited.insert(&UU).second)
00464               Worklist.push_back(&UU);
00465       };
00466 
00467       CallSite CS(I);
00468       if (CS.doesNotAccessMemory()) {
00469         AddUsersToWorklistIfCapturing();
00470         continue;
00471       }
00472 
00473       Function *F = CS.getCalledFunction();
00474       if (!F) {
00475         if (CS.onlyReadsMemory()) {
00476           IsRead = true;
00477           AddUsersToWorklistIfCapturing();
00478           continue;
00479         }
00480         return Attribute::None;
00481       }
00482 
00483       Function::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
00484       CallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
00485       for (CallSite::arg_iterator A = B; A != E; ++A, ++AI) {
00486         if (A->get() == V) {
00487           if (AI == AE) {
00488             assert(F->isVarArg() &&
00489                    "More params than args in non-varargs call.");
00490             return Attribute::None;
00491           }
00492           Captures &= !CS.doesNotCapture(A - B);
00493           if (SCCNodes.count(AI))
00494             continue;
00495           if (!CS.onlyReadsMemory() && !CS.onlyReadsMemory(A - B))
00496             return Attribute::None;
00497           if (!CS.doesNotAccessMemory(A - B))
00498             IsRead = true;
00499         }
00500       }
00501       AddUsersToWorklistIfCapturing();
00502       break;
00503     }
00504 
00505     case Instruction::Load:
00506       IsRead = true;
00507       break;
00508 
00509     case Instruction::ICmp:
00510     case Instruction::Ret:
00511       break;
00512 
00513     default:
00514       return Attribute::None;
00515     }
00516   }
00517 
00518   return IsRead ? Attribute::ReadOnly : Attribute::ReadNone;
00519 }
00520 
00521 /// AddArgumentAttrs - Deduce nocapture attributes for the SCC.
00522 bool FunctionAttrs::AddArgumentAttrs(const CallGraphSCC &SCC) {
00523   bool Changed = false;
00524 
00525   SmallPtrSet<Function*, 8> SCCNodes;
00526 
00527   // Fill SCCNodes with the elements of the SCC.  Used for quickly
00528   // looking up whether a given CallGraphNode is in this SCC.
00529   for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
00530     Function *F = (*I)->getFunction();
00531     if (F && !F->isDeclaration() && !F->mayBeOverridden() &&
00532         !F->hasFnAttribute(Attribute::OptimizeNone))
00533       SCCNodes.insert(F);
00534   }
00535 
00536   ArgumentGraph AG;
00537 
00538   AttrBuilder B;
00539   B.addAttribute(Attribute::NoCapture);
00540 
00541   // Check each function in turn, determining which pointer arguments are not
00542   // captured.
00543   for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
00544     Function *F = (*I)->getFunction();
00545 
00546     if (!F || F->hasFnAttribute(Attribute::OptimizeNone))
00547       // External node or function we're trying not to optimize - only a problem
00548       // for arguments that we pass to it.
00549       continue;
00550 
00551     // Definitions with weak linkage may be overridden at linktime with
00552     // something that captures pointers, so treat them like declarations.
00553     if (F->isDeclaration() || F->mayBeOverridden())
00554       continue;
00555 
00556     // Functions that are readonly (or readnone) and nounwind and don't return
00557     // a value can't capture arguments. Don't analyze them.
00558     if (F->onlyReadsMemory() && F->doesNotThrow() &&
00559         F->getReturnType()->isVoidTy()) {
00560       for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end();
00561            A != E; ++A) {
00562         if (A->getType()->isPointerTy() && !A->hasNoCaptureAttr()) {
00563           A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
00564           ++NumNoCapture;
00565           Changed = true;
00566         }
00567       }
00568       continue;
00569     }
00570 
00571     for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end();
00572          A != E; ++A) {
00573       if (!A->getType()->isPointerTy()) continue;
00574       bool HasNonLocalUses = false;
00575       if (!A->hasNoCaptureAttr()) {
00576         ArgumentUsesTracker Tracker(SCCNodes);
00577         PointerMayBeCaptured(A, &Tracker);
00578         if (!Tracker.Captured) {
00579           if (Tracker.Uses.empty()) {
00580             // If it's trivially not captured, mark it nocapture now.
00581             A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo()+1, B));
00582             ++NumNoCapture;
00583             Changed = true;
00584           } else {
00585             // If it's not trivially captured and not trivially not captured,
00586             // then it must be calling into another function in our SCC. Save
00587             // its particulars for Argument-SCC analysis later.
00588             ArgumentGraphNode *Node = AG[A];
00589             for (SmallVectorImpl<Argument*>::iterator UI = Tracker.Uses.begin(),
00590                      UE = Tracker.Uses.end(); UI != UE; ++UI) {
00591               Node->Uses.push_back(AG[*UI]);
00592               if (*UI != A)
00593                 HasNonLocalUses = true;
00594             }
00595           }
00596         }
00597         // Otherwise, it's captured. Don't bother doing SCC analysis on it.
00598       }
00599       if (!HasNonLocalUses && !A->onlyReadsMemory()) {
00600         // Can we determine that it's readonly/readnone without doing an SCC?
00601         // Note that we don't allow any calls at all here, or else our result
00602         // will be dependent on the iteration order through the functions in the
00603         // SCC.
00604         SmallPtrSet<Argument*, 8> Self;
00605         Self.insert(A);
00606         Attribute::AttrKind R = determinePointerReadAttrs(A, Self);
00607         if (R != Attribute::None) {
00608           AttrBuilder B;
00609           B.addAttribute(R);
00610           A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
00611           Changed = true;
00612           R == Attribute::ReadOnly ? ++NumReadOnlyArg : ++NumReadNoneArg;
00613         }
00614       }
00615     }
00616   }
00617 
00618   // The graph we've collected is partial because we stopped scanning for
00619   // argument uses once we solved the argument trivially. These partial nodes
00620   // show up as ArgumentGraphNode objects with an empty Uses list, and for
00621   // these nodes the final decision about whether they capture has already been
00622   // made.  If the definition doesn't have a 'nocapture' attribute by now, it
00623   // captures.
00624 
00625   for (scc_iterator<ArgumentGraph*> I = scc_begin(&AG); !I.isAtEnd(); ++I) {
00626     const std::vector<ArgumentGraphNode *> &ArgumentSCC = *I;
00627     if (ArgumentSCC.size() == 1) {
00628       if (!ArgumentSCC[0]->Definition) continue;  // synthetic root node
00629 
00630       // eg. "void f(int* x) { if (...) f(x); }"
00631       if (ArgumentSCC[0]->Uses.size() == 1 &&
00632           ArgumentSCC[0]->Uses[0] == ArgumentSCC[0]) {
00633         Argument *A = ArgumentSCC[0]->Definition;
00634         A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
00635         ++NumNoCapture;
00636         Changed = true;
00637       }
00638       continue;
00639     }
00640 
00641     bool SCCCaptured = false;
00642     for (auto I = ArgumentSCC.begin(), E = ArgumentSCC.end();
00643          I != E && !SCCCaptured; ++I) {
00644       ArgumentGraphNode *Node = *I;
00645       if (Node->Uses.empty()) {
00646         if (!Node->Definition->hasNoCaptureAttr())
00647           SCCCaptured = true;
00648       }
00649     }
00650     if (SCCCaptured) continue;
00651 
00652     SmallPtrSet<Argument*, 8> ArgumentSCCNodes;
00653     // Fill ArgumentSCCNodes with the elements of the ArgumentSCC.  Used for
00654     // quickly looking up whether a given Argument is in this ArgumentSCC.
00655     for (auto I = ArgumentSCC.begin(), E = ArgumentSCC.end(); I != E; ++I) {
00656       ArgumentSCCNodes.insert((*I)->Definition);
00657     }
00658 
00659     for (auto I = ArgumentSCC.begin(), E = ArgumentSCC.end();
00660          I != E && !SCCCaptured; ++I) {
00661       ArgumentGraphNode *N = *I;
00662       for (SmallVectorImpl<ArgumentGraphNode*>::iterator UI = N->Uses.begin(),
00663              UE = N->Uses.end(); UI != UE; ++UI) {
00664         Argument *A = (*UI)->Definition;
00665         if (A->hasNoCaptureAttr() || ArgumentSCCNodes.count(A))
00666           continue;
00667         SCCCaptured = true;
00668         break;
00669       }
00670     }
00671     if (SCCCaptured) continue;
00672 
00673     for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
00674       Argument *A = ArgumentSCC[i]->Definition;
00675       A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
00676       ++NumNoCapture;
00677       Changed = true;
00678     }
00679 
00680     // We also want to compute readonly/readnone. With a small number of false
00681     // negatives, we can assume that any pointer which is captured isn't going
00682     // to be provably readonly or readnone, since by definition we can't
00683     // analyze all uses of a captured pointer.
00684     //
00685     // The false negatives happen when the pointer is captured by a function
00686     // that promises readonly/readnone behaviour on the pointer, then the
00687     // pointer's lifetime ends before anything that writes to arbitrary memory.
00688     // Also, a readonly/readnone pointer may be returned, but returning a
00689     // pointer is capturing it.
00690 
00691     Attribute::AttrKind ReadAttr = Attribute::ReadNone;
00692     for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
00693       Argument *A = ArgumentSCC[i]->Definition;
00694       Attribute::AttrKind K = determinePointerReadAttrs(A, ArgumentSCCNodes);
00695       if (K == Attribute::ReadNone)
00696         continue;
00697       if (K == Attribute::ReadOnly) {
00698         ReadAttr = Attribute::ReadOnly;
00699         continue;
00700       }
00701       ReadAttr = K;
00702       break;
00703     }
00704 
00705     if (ReadAttr != Attribute::None) {
00706       AttrBuilder B;
00707       B.addAttribute(ReadAttr);
00708       for (unsigned i = 0, e = ArgumentSCC.size(); i != e; ++i) {
00709         Argument *A = ArgumentSCC[i]->Definition;
00710         A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
00711         ReadAttr == Attribute::ReadOnly ? ++NumReadOnlyArg : ++NumReadNoneArg;
00712         Changed = true;
00713       }
00714     }
00715   }
00716 
00717   return Changed;
00718 }
00719 
00720 /// IsFunctionMallocLike - A function is malloc-like if it returns either null
00721 /// or a pointer that doesn't alias any other pointer visible to the caller.
00722 bool FunctionAttrs::IsFunctionMallocLike(Function *F,
00723                               SmallPtrSet<Function*, 8> &SCCNodes) const {
00724   SmallSetVector<Value *, 8> FlowsToReturn;
00725   for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I)
00726     if (ReturnInst *Ret = dyn_cast<ReturnInst>(I->getTerminator()))
00727       FlowsToReturn.insert(Ret->getReturnValue());
00728 
00729   for (unsigned i = 0; i != FlowsToReturn.size(); ++i) {
00730     Value *RetVal = FlowsToReturn[i];
00731 
00732     if (Constant *C = dyn_cast<Constant>(RetVal)) {
00733       if (!C->isNullValue() && !isa<UndefValue>(C))
00734         return false;
00735 
00736       continue;
00737     }
00738 
00739     if (isa<Argument>(RetVal))
00740       return false;
00741 
00742     if (Instruction *RVI = dyn_cast<Instruction>(RetVal))
00743       switch (RVI->getOpcode()) {
00744         // Extend the analysis by looking upwards.
00745         case Instruction::BitCast:
00746         case Instruction::GetElementPtr:
00747         case Instruction::AddrSpaceCast:
00748           FlowsToReturn.insert(RVI->getOperand(0));
00749           continue;
00750         case Instruction::Select: {
00751           SelectInst *SI = cast<SelectInst>(RVI);
00752           FlowsToReturn.insert(SI->getTrueValue());
00753           FlowsToReturn.insert(SI->getFalseValue());
00754           continue;
00755         }
00756         case Instruction::PHI: {
00757           PHINode *PN = cast<PHINode>(RVI);
00758           for (int i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
00759             FlowsToReturn.insert(PN->getIncomingValue(i));
00760           continue;
00761         }
00762 
00763         // Check whether the pointer came from an allocation.
00764         case Instruction::Alloca:
00765           break;
00766         case Instruction::Call:
00767         case Instruction::Invoke: {
00768           CallSite CS(RVI);
00769           if (CS.paramHasAttr(0, Attribute::NoAlias))
00770             break;
00771           if (CS.getCalledFunction() &&
00772               SCCNodes.count(CS.getCalledFunction()))
00773             break;
00774         } // fall-through
00775         default:
00776           return false;  // Did not come from an allocation.
00777       }
00778 
00779     if (PointerMayBeCaptured(RetVal, false, /*StoreCaptures=*/false))
00780       return false;
00781   }
00782 
00783   return true;
00784 }
00785 
00786 /// AddNoAliasAttrs - Deduce noalias attributes for the SCC.
00787 bool FunctionAttrs::AddNoAliasAttrs(const CallGraphSCC &SCC) {
00788   SmallPtrSet<Function*, 8> SCCNodes;
00789 
00790   // Fill SCCNodes with the elements of the SCC.  Used for quickly
00791   // looking up whether a given CallGraphNode is in this SCC.
00792   for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I)
00793     SCCNodes.insert((*I)->getFunction());
00794 
00795   // Check each function in turn, determining which functions return noalias
00796   // pointers.
00797   for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
00798     Function *F = (*I)->getFunction();
00799 
00800     if (!F || F->hasFnAttribute(Attribute::OptimizeNone))
00801       // External node or node we don't want to optimize - skip it;
00802       return false;
00803 
00804     // Already noalias.
00805     if (F->doesNotAlias(0))
00806       continue;
00807 
00808     // Definitions with weak linkage may be overridden at linktime, so
00809     // treat them like declarations.
00810     if (F->isDeclaration() || F->mayBeOverridden())
00811       return false;
00812 
00813     // We annotate noalias return values, which are only applicable to 
00814     // pointer types.
00815     if (!F->getReturnType()->isPointerTy())
00816       continue;
00817 
00818     if (!IsFunctionMallocLike(F, SCCNodes))
00819       return false;
00820   }
00821 
00822   bool MadeChange = false;
00823   for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
00824     Function *F = (*I)->getFunction();
00825     if (F->doesNotAlias(0) || !F->getReturnType()->isPointerTy())
00826       continue;
00827 
00828     F->setDoesNotAlias(0);
00829     ++NumNoAlias;
00830     MadeChange = true;
00831   }
00832 
00833   return MadeChange;
00834 }
00835 
00836 /// inferPrototypeAttributes - Analyze the name and prototype of the
00837 /// given function and set any applicable attributes.  Returns true
00838 /// if any attributes were set and false otherwise.
00839 bool FunctionAttrs::inferPrototypeAttributes(Function &F) {
00840   if (F.hasFnAttribute(Attribute::OptimizeNone))
00841     return false;
00842 
00843   FunctionType *FTy = F.getFunctionType();
00844   LibFunc::Func TheLibFunc;
00845   if (!(TLI->getLibFunc(F.getName(), TheLibFunc) && TLI->has(TheLibFunc)))
00846     return false;
00847 
00848   switch (TheLibFunc) {
00849   case LibFunc::strlen:
00850     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
00851       return false;
00852     setOnlyReadsMemory(F);
00853     setDoesNotThrow(F);
00854     setDoesNotCapture(F, 1);
00855     break;
00856   case LibFunc::strchr:
00857   case LibFunc::strrchr:
00858     if (FTy->getNumParams() != 2 ||
00859         !FTy->getParamType(0)->isPointerTy() ||
00860         !FTy->getParamType(1)->isIntegerTy())
00861       return false;
00862     setOnlyReadsMemory(F);
00863     setDoesNotThrow(F);
00864     break;
00865   case LibFunc::strtol:
00866   case LibFunc::strtod:
00867   case LibFunc::strtof:
00868   case LibFunc::strtoul:
00869   case LibFunc::strtoll:
00870   case LibFunc::strtold:
00871   case LibFunc::strtoull:
00872     if (FTy->getNumParams() < 2 ||
00873         !FTy->getParamType(1)->isPointerTy())
00874       return false;
00875     setDoesNotThrow(F);
00876     setDoesNotCapture(F, 2);
00877     setOnlyReadsMemory(F, 1);
00878     break;
00879   case LibFunc::strcpy:
00880   case LibFunc::stpcpy:
00881   case LibFunc::strcat:
00882   case LibFunc::strncat:
00883   case LibFunc::strncpy:
00884   case LibFunc::stpncpy:
00885     if (FTy->getNumParams() < 2 ||
00886         !FTy->getParamType(1)->isPointerTy())
00887       return false;
00888     setDoesNotThrow(F);
00889     setDoesNotCapture(F, 2);
00890     setOnlyReadsMemory(F, 2);
00891     break;
00892   case LibFunc::strxfrm:
00893     if (FTy->getNumParams() != 3 ||
00894         !FTy->getParamType(0)->isPointerTy() ||
00895         !FTy->getParamType(1)->isPointerTy())
00896       return false;
00897     setDoesNotThrow(F);
00898     setDoesNotCapture(F, 1);
00899     setDoesNotCapture(F, 2);
00900     setOnlyReadsMemory(F, 2);
00901     break;
00902   case LibFunc::strcmp: //0,1
00903     case LibFunc::strspn: // 0,1
00904     case LibFunc::strncmp: // 0,1
00905     case LibFunc::strcspn: //0,1
00906     case LibFunc::strcoll: //0,1
00907     case LibFunc::strcasecmp:  // 0,1
00908     case LibFunc::strncasecmp: // 
00909     if (FTy->getNumParams() < 2 ||
00910         !FTy->getParamType(0)->isPointerTy() ||
00911         !FTy->getParamType(1)->isPointerTy())
00912       return false;
00913     setOnlyReadsMemory(F);
00914     setDoesNotThrow(F);
00915     setDoesNotCapture(F, 1);
00916     setDoesNotCapture(F, 2);
00917     break;
00918   case LibFunc::strstr:
00919   case LibFunc::strpbrk:
00920     if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
00921       return false;
00922     setOnlyReadsMemory(F);
00923     setDoesNotThrow(F);
00924     setDoesNotCapture(F, 2);
00925     break;
00926   case LibFunc::strtok:
00927   case LibFunc::strtok_r:
00928     if (FTy->getNumParams() < 2 || !FTy->getParamType(1)->isPointerTy())
00929       return false;
00930     setDoesNotThrow(F);
00931     setDoesNotCapture(F, 2);
00932     setOnlyReadsMemory(F, 2);
00933     break;
00934   case LibFunc::scanf:
00935     if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
00936       return false;
00937     setDoesNotThrow(F);
00938     setDoesNotCapture(F, 1);
00939     setOnlyReadsMemory(F, 1);
00940     break;
00941   case LibFunc::setbuf:
00942   case LibFunc::setvbuf:
00943     if (FTy->getNumParams() < 1 || !FTy->getParamType(0)->isPointerTy())
00944       return false;
00945     setDoesNotThrow(F);
00946     setDoesNotCapture(F, 1);
00947     break;
00948   case LibFunc::strdup:
00949   case LibFunc::strndup:
00950     if (FTy->getNumParams() < 1 || !FTy->getReturnType()->isPointerTy() ||
00951         !FTy->getParamType(0)->isPointerTy())
00952       return false;
00953     setDoesNotThrow(F);
00954     setDoesNotAlias(F, 0);
00955     setDoesNotCapture(F, 1);
00956     setOnlyReadsMemory(F, 1);
00957     break;
00958   case LibFunc::stat:
00959   case LibFunc::statvfs:
00960     if (FTy->getNumParams() < 2 ||
00961         !FTy->getParamType(0)->isPointerTy() ||
00962         !FTy->getParamType(1)->isPointerTy())
00963       return false;
00964     setDoesNotThrow(F);
00965     setDoesNotCapture(F, 1);
00966     setDoesNotCapture(F, 2);
00967     setOnlyReadsMemory(F, 1);
00968     break;
00969   case LibFunc::sscanf:
00970     if (FTy->getNumParams() < 2 ||
00971         !FTy->getParamType(0)->isPointerTy() ||
00972         !FTy->getParamType(1)->isPointerTy())
00973       return false;
00974     setDoesNotThrow(F);
00975     setDoesNotCapture(F, 1);
00976     setDoesNotCapture(F, 2);
00977     setOnlyReadsMemory(F, 1);
00978     setOnlyReadsMemory(F, 2);
00979     break;
00980   case LibFunc::sprintf:
00981     if (FTy->getNumParams() < 2 ||
00982         !FTy->getParamType(0)->isPointerTy() ||
00983         !FTy->getParamType(1)->isPointerTy())
00984       return false;
00985     setDoesNotThrow(F);
00986     setDoesNotCapture(F, 1);
00987     setDoesNotCapture(F, 2);
00988     setOnlyReadsMemory(F, 2);
00989     break;
00990   case LibFunc::snprintf:
00991     if (FTy->getNumParams() != 3 ||
00992         !FTy->getParamType(0)->isPointerTy() ||
00993         !FTy->getParamType(2)->isPointerTy())
00994       return false;
00995     setDoesNotThrow(F);
00996     setDoesNotCapture(F, 1);
00997     setDoesNotCapture(F, 3);
00998     setOnlyReadsMemory(F, 3);
00999     break;
01000   case LibFunc::setitimer:
01001     if (FTy->getNumParams() != 3 ||
01002         !FTy->getParamType(1)->isPointerTy() ||
01003         !FTy->getParamType(2)->isPointerTy())
01004       return false;
01005     setDoesNotThrow(F);
01006     setDoesNotCapture(F, 2);
01007     setDoesNotCapture(F, 3);
01008     setOnlyReadsMemory(F, 2);
01009     break;
01010   case LibFunc::system:
01011     if (FTy->getNumParams() != 1 ||
01012         !FTy->getParamType(0)->isPointerTy())
01013       return false;
01014     // May throw; "system" is a valid pthread cancellation point.
01015     setDoesNotCapture(F, 1);
01016     setOnlyReadsMemory(F, 1);
01017     break;
01018   case LibFunc::malloc:
01019     if (FTy->getNumParams() != 1 ||
01020         !FTy->getReturnType()->isPointerTy())
01021       return false;
01022     setDoesNotThrow(F);
01023     setDoesNotAlias(F, 0);
01024     break;
01025   case LibFunc::memcmp:
01026     if (FTy->getNumParams() != 3 ||
01027         !FTy->getParamType(0)->isPointerTy() ||
01028         !FTy->getParamType(1)->isPointerTy())
01029       return false;
01030     setOnlyReadsMemory(F);
01031     setDoesNotThrow(F);
01032     setDoesNotCapture(F, 1);
01033     setDoesNotCapture(F, 2);
01034     break;
01035   case LibFunc::memchr:
01036   case LibFunc::memrchr:
01037     if (FTy->getNumParams() != 3)
01038       return false;
01039     setOnlyReadsMemory(F);
01040     setDoesNotThrow(F);
01041     break;
01042   case LibFunc::modf:
01043   case LibFunc::modff:
01044   case LibFunc::modfl:
01045     if (FTy->getNumParams() < 2 ||
01046         !FTy->getParamType(1)->isPointerTy())
01047       return false;
01048     setDoesNotThrow(F);
01049     setDoesNotCapture(F, 2);
01050     break;
01051   case LibFunc::memcpy:
01052   case LibFunc::memccpy:
01053   case LibFunc::memmove:
01054     if (FTy->getNumParams() < 2 ||
01055         !FTy->getParamType(1)->isPointerTy())
01056       return false;
01057     setDoesNotThrow(F);
01058     setDoesNotCapture(F, 2);
01059     setOnlyReadsMemory(F, 2);
01060     break;
01061   case LibFunc::memalign:
01062     if (!FTy->getReturnType()->isPointerTy())
01063       return false;
01064     setDoesNotAlias(F, 0);
01065     break;
01066   case LibFunc::mkdir:
01067     if (FTy->getNumParams() == 0 ||
01068         !FTy->getParamType(0)->isPointerTy())
01069       return false;
01070     setDoesNotThrow(F);
01071     setDoesNotCapture(F, 1);
01072     setOnlyReadsMemory(F, 1);
01073     break;
01074   case LibFunc::mktime:
01075     if (FTy->getNumParams() == 0 ||
01076         !FTy->getParamType(0)->isPointerTy())
01077       return false;
01078     setDoesNotThrow(F);
01079     setDoesNotCapture(F, 1);
01080     break;
01081   case LibFunc::realloc:
01082     if (FTy->getNumParams() != 2 ||
01083         !FTy->getParamType(0)->isPointerTy() ||
01084         !FTy->getReturnType()->isPointerTy())
01085       return false;
01086     setDoesNotThrow(F);
01087     setDoesNotAlias(F, 0);
01088     setDoesNotCapture(F, 1);
01089     break;
01090   case LibFunc::read:
01091     if (FTy->getNumParams() != 3 ||
01092         !FTy->getParamType(1)->isPointerTy())
01093       return false;
01094     // May throw; "read" is a valid pthread cancellation point.
01095     setDoesNotCapture(F, 2);
01096     break;
01097   case LibFunc::rewind:
01098     if (FTy->getNumParams() < 1 ||
01099         !FTy->getParamType(0)->isPointerTy())
01100       return false;
01101     setDoesNotThrow(F);
01102     setDoesNotCapture(F, 1);
01103     break;
01104   case LibFunc::rmdir:
01105   case LibFunc::remove:
01106   case LibFunc::realpath:
01107     if (FTy->getNumParams() < 1 ||
01108         !FTy->getParamType(0)->isPointerTy())
01109       return false;
01110     setDoesNotThrow(F);
01111     setDoesNotCapture(F, 1);
01112     setOnlyReadsMemory(F, 1);
01113     break;
01114   case LibFunc::rename:
01115     if (FTy->getNumParams() < 2 ||
01116         !FTy->getParamType(0)->isPointerTy() ||
01117         !FTy->getParamType(1)->isPointerTy())
01118       return false;
01119     setDoesNotThrow(F);
01120     setDoesNotCapture(F, 1);
01121     setDoesNotCapture(F, 2);
01122     setOnlyReadsMemory(F, 1);
01123     setOnlyReadsMemory(F, 2);
01124     break;
01125   case LibFunc::readlink:
01126     if (FTy->getNumParams() < 2 ||
01127         !FTy->getParamType(0)->isPointerTy() ||
01128         !FTy->getParamType(1)->isPointerTy())
01129       return false;
01130     setDoesNotThrow(F);
01131     setDoesNotCapture(F, 1);
01132     setDoesNotCapture(F, 2);
01133     setOnlyReadsMemory(F, 1);
01134     break;
01135   case LibFunc::write:
01136     if (FTy->getNumParams() != 3 || !FTy->getParamType(1)->isPointerTy())
01137       return false;
01138     // May throw; "write" is a valid pthread cancellation point.
01139     setDoesNotCapture(F, 2);
01140     setOnlyReadsMemory(F, 2);
01141     break;
01142   case LibFunc::bcopy:
01143     if (FTy->getNumParams() != 3 ||
01144         !FTy->getParamType(0)->isPointerTy() ||
01145         !FTy->getParamType(1)->isPointerTy())
01146       return false;
01147     setDoesNotThrow(F);
01148     setDoesNotCapture(F, 1);
01149     setDoesNotCapture(F, 2);
01150     setOnlyReadsMemory(F, 1);
01151     break;
01152   case LibFunc::bcmp:
01153     if (FTy->getNumParams() != 3 ||
01154         !FTy->getParamType(0)->isPointerTy() ||
01155         !FTy->getParamType(1)->isPointerTy())
01156       return false;
01157     setDoesNotThrow(F);
01158     setOnlyReadsMemory(F);
01159     setDoesNotCapture(F, 1);
01160     setDoesNotCapture(F, 2);
01161     break;
01162   case LibFunc::bzero:
01163     if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
01164       return false;
01165     setDoesNotThrow(F);
01166     setDoesNotCapture(F, 1);
01167     break;
01168   case LibFunc::calloc:
01169     if (FTy->getNumParams() != 2 ||
01170         !FTy->getReturnType()->isPointerTy())
01171       return false;
01172     setDoesNotThrow(F);
01173     setDoesNotAlias(F, 0);
01174     break;
01175   case LibFunc::chmod:
01176   case LibFunc::chown:
01177     if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
01178       return false;
01179     setDoesNotThrow(F);
01180     setDoesNotCapture(F, 1);
01181     setOnlyReadsMemory(F, 1);
01182     break;
01183   case LibFunc::ctermid:
01184   case LibFunc::clearerr:
01185   case LibFunc::closedir:
01186     if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
01187       return false;
01188     setDoesNotThrow(F);
01189     setDoesNotCapture(F, 1);
01190     break;
01191   case LibFunc::atoi:
01192   case LibFunc::atol:
01193   case LibFunc::atof:
01194   case LibFunc::atoll:
01195     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01196       return false;
01197     setDoesNotThrow(F);
01198     setOnlyReadsMemory(F);
01199     setDoesNotCapture(F, 1);
01200     break;
01201   case LibFunc::access:
01202     if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
01203       return false;
01204     setDoesNotThrow(F);
01205     setDoesNotCapture(F, 1);
01206     setOnlyReadsMemory(F, 1);
01207     break;
01208   case LibFunc::fopen:
01209     if (FTy->getNumParams() != 2 ||
01210         !FTy->getReturnType()->isPointerTy() ||
01211         !FTy->getParamType(0)->isPointerTy() ||
01212         !FTy->getParamType(1)->isPointerTy())
01213       return false;
01214     setDoesNotThrow(F);
01215     setDoesNotAlias(F, 0);
01216     setDoesNotCapture(F, 1);
01217     setDoesNotCapture(F, 2);
01218     setOnlyReadsMemory(F, 1);
01219     setOnlyReadsMemory(F, 2);
01220     break;
01221   case LibFunc::fdopen:
01222     if (FTy->getNumParams() != 2 ||
01223         !FTy->getReturnType()->isPointerTy() ||
01224         !FTy->getParamType(1)->isPointerTy())
01225       return false;
01226     setDoesNotThrow(F);
01227     setDoesNotAlias(F, 0);
01228     setDoesNotCapture(F, 2);
01229     setOnlyReadsMemory(F, 2);
01230     break;
01231   case LibFunc::feof:
01232   case LibFunc::free:
01233   case LibFunc::fseek:
01234   case LibFunc::ftell:
01235   case LibFunc::fgetc:
01236   case LibFunc::fseeko:
01237   case LibFunc::ftello:
01238   case LibFunc::fileno:
01239   case LibFunc::fflush:
01240   case LibFunc::fclose:
01241   case LibFunc::fsetpos:
01242   case LibFunc::flockfile:
01243   case LibFunc::funlockfile:
01244   case LibFunc::ftrylockfile:
01245     if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
01246       return false;
01247     setDoesNotThrow(F);
01248     setDoesNotCapture(F, 1);
01249     break;
01250   case LibFunc::ferror:
01251     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01252       return false;
01253     setDoesNotThrow(F);
01254     setDoesNotCapture(F, 1);
01255     setOnlyReadsMemory(F);
01256     break;
01257   case LibFunc::fputc:
01258   case LibFunc::fstat:
01259   case LibFunc::frexp:
01260   case LibFunc::frexpf:
01261   case LibFunc::frexpl:
01262   case LibFunc::fstatvfs:
01263     if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
01264       return false;
01265     setDoesNotThrow(F);
01266     setDoesNotCapture(F, 2);
01267     break;
01268   case LibFunc::fgets:
01269     if (FTy->getNumParams() != 3 ||
01270         !FTy->getParamType(0)->isPointerTy() ||
01271         !FTy->getParamType(2)->isPointerTy())
01272       return false;
01273     setDoesNotThrow(F);
01274     setDoesNotCapture(F, 3);
01275     break;
01276   case LibFunc::fread:
01277     if (FTy->getNumParams() != 4 ||
01278         !FTy->getParamType(0)->isPointerTy() ||
01279         !FTy->getParamType(3)->isPointerTy())
01280       return false;
01281     setDoesNotThrow(F);
01282     setDoesNotCapture(F, 1);
01283     setDoesNotCapture(F, 4);
01284     break;
01285   case LibFunc::fwrite:
01286     if (FTy->getNumParams() != 4 ||
01287         !FTy->getParamType(0)->isPointerTy() ||
01288         !FTy->getParamType(3)->isPointerTy())
01289       return false;
01290     setDoesNotThrow(F);
01291     setDoesNotCapture(F, 1);
01292     setDoesNotCapture(F, 4);
01293     break;
01294   case LibFunc::fputs:
01295     if (FTy->getNumParams() < 2 ||
01296         !FTy->getParamType(0)->isPointerTy() ||
01297         !FTy->getParamType(1)->isPointerTy())
01298       return false;
01299     setDoesNotThrow(F);
01300     setDoesNotCapture(F, 1);
01301     setDoesNotCapture(F, 2);
01302     setOnlyReadsMemory(F, 1);
01303     break;
01304   case LibFunc::fscanf:
01305   case LibFunc::fprintf:
01306     if (FTy->getNumParams() < 2 ||
01307         !FTy->getParamType(0)->isPointerTy() ||
01308         !FTy->getParamType(1)->isPointerTy())
01309       return false;
01310     setDoesNotThrow(F);
01311     setDoesNotCapture(F, 1);
01312     setDoesNotCapture(F, 2);
01313     setOnlyReadsMemory(F, 2);
01314     break;
01315   case LibFunc::fgetpos:
01316     if (FTy->getNumParams() < 2 ||
01317         !FTy->getParamType(0)->isPointerTy() ||
01318         !FTy->getParamType(1)->isPointerTy())
01319       return false;
01320     setDoesNotThrow(F);
01321     setDoesNotCapture(F, 1);
01322     setDoesNotCapture(F, 2);
01323     break;
01324   case LibFunc::getc:
01325   case LibFunc::getlogin_r:
01326   case LibFunc::getc_unlocked:
01327     if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
01328       return false;
01329     setDoesNotThrow(F);
01330     setDoesNotCapture(F, 1);
01331     break;
01332   case LibFunc::getenv:
01333     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01334       return false;
01335     setDoesNotThrow(F);
01336     setOnlyReadsMemory(F);
01337     setDoesNotCapture(F, 1);
01338     break;
01339   case LibFunc::gets:
01340   case LibFunc::getchar:
01341     setDoesNotThrow(F);
01342     break;
01343   case LibFunc::getitimer:
01344     if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
01345       return false;
01346     setDoesNotThrow(F);
01347     setDoesNotCapture(F, 2);
01348     break;
01349   case LibFunc::getpwnam:
01350     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01351       return false;
01352     setDoesNotThrow(F);
01353     setDoesNotCapture(F, 1);
01354     setOnlyReadsMemory(F, 1);
01355     break;
01356   case LibFunc::ungetc:
01357     if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
01358       return false;
01359     setDoesNotThrow(F);
01360     setDoesNotCapture(F, 2);
01361     break;
01362   case LibFunc::uname:
01363     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01364       return false;
01365     setDoesNotThrow(F);
01366     setDoesNotCapture(F, 1);
01367     break;
01368   case LibFunc::unlink:
01369     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01370       return false;
01371     setDoesNotThrow(F);
01372     setDoesNotCapture(F, 1);
01373     setOnlyReadsMemory(F, 1);
01374     break;
01375   case LibFunc::unsetenv:
01376     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01377       return false;
01378     setDoesNotThrow(F);
01379     setDoesNotCapture(F, 1);
01380     setOnlyReadsMemory(F, 1);
01381     break;
01382   case LibFunc::utime:
01383   case LibFunc::utimes:
01384     if (FTy->getNumParams() != 2 ||
01385         !FTy->getParamType(0)->isPointerTy() ||
01386         !FTy->getParamType(1)->isPointerTy())
01387       return false;
01388     setDoesNotThrow(F);
01389     setDoesNotCapture(F, 1);
01390     setDoesNotCapture(F, 2);
01391     setOnlyReadsMemory(F, 1);
01392     setOnlyReadsMemory(F, 2);
01393     break;
01394   case LibFunc::putc:
01395     if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
01396       return false;
01397     setDoesNotThrow(F);
01398     setDoesNotCapture(F, 2);
01399     break;
01400   case LibFunc::puts:
01401   case LibFunc::printf:
01402   case LibFunc::perror:
01403     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01404       return false;
01405     setDoesNotThrow(F);
01406     setDoesNotCapture(F, 1);
01407     setOnlyReadsMemory(F, 1);
01408     break;
01409   case LibFunc::pread:
01410     if (FTy->getNumParams() != 4 || !FTy->getParamType(1)->isPointerTy())
01411       return false;
01412     // May throw; "pread" is a valid pthread cancellation point.
01413     setDoesNotCapture(F, 2);
01414     break;
01415   case LibFunc::pwrite:
01416     if (FTy->getNumParams() != 4 || !FTy->getParamType(1)->isPointerTy())
01417       return false;
01418     // May throw; "pwrite" is a valid pthread cancellation point.
01419     setDoesNotCapture(F, 2);
01420     setOnlyReadsMemory(F, 2);
01421     break;
01422   case LibFunc::putchar:
01423     setDoesNotThrow(F);
01424     break;
01425   case LibFunc::popen:
01426     if (FTy->getNumParams() != 2 ||
01427         !FTy->getReturnType()->isPointerTy() ||
01428         !FTy->getParamType(0)->isPointerTy() ||
01429         !FTy->getParamType(1)->isPointerTy())
01430       return false;
01431     setDoesNotThrow(F);
01432     setDoesNotAlias(F, 0);
01433     setDoesNotCapture(F, 1);
01434     setDoesNotCapture(F, 2);
01435     setOnlyReadsMemory(F, 1);
01436     setOnlyReadsMemory(F, 2);
01437     break;
01438   case LibFunc::pclose:
01439     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01440       return false;
01441     setDoesNotThrow(F);
01442     setDoesNotCapture(F, 1);
01443     break;
01444   case LibFunc::vscanf:
01445     if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
01446       return false;
01447     setDoesNotThrow(F);
01448     setDoesNotCapture(F, 1);
01449     setOnlyReadsMemory(F, 1);
01450     break;
01451   case LibFunc::vsscanf:
01452     if (FTy->getNumParams() != 3 ||
01453         !FTy->getParamType(1)->isPointerTy() ||
01454         !FTy->getParamType(2)->isPointerTy())
01455       return false;
01456     setDoesNotThrow(F);
01457     setDoesNotCapture(F, 1);
01458     setDoesNotCapture(F, 2);
01459     setOnlyReadsMemory(F, 1);
01460     setOnlyReadsMemory(F, 2);
01461     break;
01462   case LibFunc::vfscanf:
01463     if (FTy->getNumParams() != 3 ||
01464         !FTy->getParamType(1)->isPointerTy() ||
01465         !FTy->getParamType(2)->isPointerTy())
01466       return false;
01467     setDoesNotThrow(F);
01468     setDoesNotCapture(F, 1);
01469     setDoesNotCapture(F, 2);
01470     setOnlyReadsMemory(F, 2);
01471     break;
01472   case LibFunc::valloc:
01473     if (!FTy->getReturnType()->isPointerTy())
01474       return false;
01475     setDoesNotThrow(F);
01476     setDoesNotAlias(F, 0);
01477     break;
01478   case LibFunc::vprintf:
01479     if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy())
01480       return false;
01481     setDoesNotThrow(F);
01482     setDoesNotCapture(F, 1);
01483     setOnlyReadsMemory(F, 1);
01484     break;
01485   case LibFunc::vfprintf:
01486   case LibFunc::vsprintf:
01487     if (FTy->getNumParams() != 3 ||
01488         !FTy->getParamType(0)->isPointerTy() ||
01489         !FTy->getParamType(1)->isPointerTy())
01490       return false;
01491     setDoesNotThrow(F);
01492     setDoesNotCapture(F, 1);
01493     setDoesNotCapture(F, 2);
01494     setOnlyReadsMemory(F, 2);
01495     break;
01496   case LibFunc::vsnprintf:
01497     if (FTy->getNumParams() != 4 ||
01498         !FTy->getParamType(0)->isPointerTy() ||
01499         !FTy->getParamType(2)->isPointerTy())
01500       return false;
01501     setDoesNotThrow(F);
01502     setDoesNotCapture(F, 1);
01503     setDoesNotCapture(F, 3);
01504     setOnlyReadsMemory(F, 3);
01505     break;
01506   case LibFunc::open:
01507     if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy())
01508       return false;
01509     // May throw; "open" is a valid pthread cancellation point.
01510     setDoesNotCapture(F, 1);
01511     setOnlyReadsMemory(F, 1);
01512     break;
01513   case LibFunc::opendir:
01514     if (FTy->getNumParams() != 1 ||
01515         !FTy->getReturnType()->isPointerTy() ||
01516         !FTy->getParamType(0)->isPointerTy())
01517       return false;
01518     setDoesNotThrow(F);
01519     setDoesNotAlias(F, 0);
01520     setDoesNotCapture(F, 1);
01521     setOnlyReadsMemory(F, 1);
01522     break;
01523   case LibFunc::tmpfile:
01524     if (!FTy->getReturnType()->isPointerTy())
01525       return false;
01526     setDoesNotThrow(F);
01527     setDoesNotAlias(F, 0);
01528     break;
01529   case LibFunc::times:
01530     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01531       return false;
01532     setDoesNotThrow(F);
01533     setDoesNotCapture(F, 1);
01534     break;
01535   case LibFunc::htonl:
01536   case LibFunc::htons:
01537   case LibFunc::ntohl:
01538   case LibFunc::ntohs:
01539     setDoesNotThrow(F);
01540     setDoesNotAccessMemory(F);
01541     break;
01542   case LibFunc::lstat:
01543     if (FTy->getNumParams() != 2 ||
01544         !FTy->getParamType(0)->isPointerTy() ||
01545         !FTy->getParamType(1)->isPointerTy())
01546       return false;
01547     setDoesNotThrow(F);
01548     setDoesNotCapture(F, 1);
01549     setDoesNotCapture(F, 2);
01550     setOnlyReadsMemory(F, 1);
01551     break;
01552   case LibFunc::lchown:
01553     if (FTy->getNumParams() != 3 || !FTy->getParamType(0)->isPointerTy())
01554       return false;
01555     setDoesNotThrow(F);
01556     setDoesNotCapture(F, 1);
01557     setOnlyReadsMemory(F, 1);
01558     break;
01559   case LibFunc::qsort:
01560     if (FTy->getNumParams() != 4 || !FTy->getParamType(3)->isPointerTy())
01561       return false;
01562     // May throw; places call through function pointer.
01563     setDoesNotCapture(F, 4);
01564     break;
01565   case LibFunc::dunder_strdup:
01566   case LibFunc::dunder_strndup:
01567     if (FTy->getNumParams() < 1 ||
01568         !FTy->getReturnType()->isPointerTy() ||
01569         !FTy->getParamType(0)->isPointerTy())
01570       return false;
01571     setDoesNotThrow(F);
01572     setDoesNotAlias(F, 0);
01573     setDoesNotCapture(F, 1);
01574     setOnlyReadsMemory(F, 1);
01575     break;
01576   case LibFunc::dunder_strtok_r:
01577     if (FTy->getNumParams() != 3 ||
01578         !FTy->getParamType(1)->isPointerTy())
01579       return false;
01580     setDoesNotThrow(F);
01581     setDoesNotCapture(F, 2);
01582     setOnlyReadsMemory(F, 2);
01583     break;
01584   case LibFunc::under_IO_getc:
01585     if (FTy->getNumParams() != 1 || !FTy->getParamType(0)->isPointerTy())
01586       return false;
01587     setDoesNotThrow(F);
01588     setDoesNotCapture(F, 1);
01589     break;
01590   case LibFunc::under_IO_putc:
01591     if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
01592       return false;
01593     setDoesNotThrow(F);
01594     setDoesNotCapture(F, 2);
01595     break;
01596   case LibFunc::dunder_isoc99_scanf:
01597     if (FTy->getNumParams() < 1 ||
01598         !FTy->getParamType(0)->isPointerTy())
01599       return false;
01600     setDoesNotThrow(F);
01601     setDoesNotCapture(F, 1);
01602     setOnlyReadsMemory(F, 1);
01603     break;
01604   case LibFunc::stat64:
01605   case LibFunc::lstat64:
01606   case LibFunc::statvfs64:
01607     if (FTy->getNumParams() < 1 ||
01608         !FTy->getParamType(0)->isPointerTy() ||
01609         !FTy->getParamType(1)->isPointerTy())
01610       return false;
01611     setDoesNotThrow(F);
01612     setDoesNotCapture(F, 1);
01613     setDoesNotCapture(F, 2);
01614     setOnlyReadsMemory(F, 1);
01615     break;
01616   case LibFunc::dunder_isoc99_sscanf:
01617     if (FTy->getNumParams() < 1 ||
01618         !FTy->getParamType(0)->isPointerTy() ||
01619         !FTy->getParamType(1)->isPointerTy())
01620       return false;
01621     setDoesNotThrow(F);
01622     setDoesNotCapture(F, 1);
01623     setDoesNotCapture(F, 2);
01624     setOnlyReadsMemory(F, 1);
01625     setOnlyReadsMemory(F, 2);
01626     break;
01627   case LibFunc::fopen64:
01628     if (FTy->getNumParams() != 2 ||
01629         !FTy->getReturnType()->isPointerTy() ||
01630         !FTy->getParamType(0)->isPointerTy() ||
01631         !FTy->getParamType(1)->isPointerTy())
01632       return false;
01633     setDoesNotThrow(F);
01634     setDoesNotAlias(F, 0);
01635     setDoesNotCapture(F, 1);
01636     setDoesNotCapture(F, 2);
01637     setOnlyReadsMemory(F, 1);
01638     setOnlyReadsMemory(F, 2);
01639     break;
01640   case LibFunc::fseeko64:
01641   case LibFunc::ftello64:
01642     if (FTy->getNumParams() == 0 || !FTy->getParamType(0)->isPointerTy())
01643       return false;
01644     setDoesNotThrow(F);
01645     setDoesNotCapture(F, 1);
01646     break;
01647   case LibFunc::tmpfile64:
01648     if (!FTy->getReturnType()->isPointerTy())
01649       return false;
01650     setDoesNotThrow(F);
01651     setDoesNotAlias(F, 0);
01652     break;
01653   case LibFunc::fstat64:
01654   case LibFunc::fstatvfs64:
01655     if (FTy->getNumParams() != 2 || !FTy->getParamType(1)->isPointerTy())
01656       return false;
01657     setDoesNotThrow(F);
01658     setDoesNotCapture(F, 2);
01659     break;
01660   case LibFunc::open64:
01661     if (FTy->getNumParams() < 2 || !FTy->getParamType(0)->isPointerTy())
01662       return false;
01663     // May throw; "open" is a valid pthread cancellation point.
01664     setDoesNotCapture(F, 1);
01665     setOnlyReadsMemory(F, 1);
01666     break;
01667   case LibFunc::gettimeofday:
01668     if (FTy->getNumParams() != 2 || !FTy->getParamType(0)->isPointerTy() ||
01669         !FTy->getParamType(1)->isPointerTy())
01670       return false;
01671     // Currently some platforms have the restrict keyword on the arguments to
01672     // gettimeofday. To be conservative, do not add noalias to gettimeofday's
01673     // arguments.
01674     setDoesNotThrow(F);
01675     setDoesNotCapture(F, 1);
01676     setDoesNotCapture(F, 2);
01677     break;
01678   default:
01679     // Didn't mark any attributes.
01680     return false;
01681   }
01682 
01683   return true;
01684 }
01685 
01686 /// annotateLibraryCalls - Adds attributes to well-known standard library
01687 /// call declarations.
01688 bool FunctionAttrs::annotateLibraryCalls(const CallGraphSCC &SCC) {
01689   bool MadeChange = false;
01690 
01691   // Check each function in turn annotating well-known library function
01692   // declarations with attributes.
01693   for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
01694     Function *F = (*I)->getFunction();
01695 
01696     if (F && F->isDeclaration())
01697       MadeChange |= inferPrototypeAttributes(*F);
01698   }
01699 
01700   return MadeChange;
01701 }
01702 
01703 bool FunctionAttrs::runOnSCC(CallGraphSCC &SCC) {
01704   AA = &getAnalysis<AliasAnalysis>();
01705   TLI = &getAnalysis<TargetLibraryInfo>();
01706 
01707   bool Changed = annotateLibraryCalls(SCC);
01708   Changed |= AddReadAttrs(SCC);
01709   Changed |= AddArgumentAttrs(SCC);
01710   Changed |= AddNoAliasAttrs(SCC);
01711   return Changed;
01712 }