[llvm-commits] CVS: llvm/lib/Analysis/IPA/Andersens.cpp
Chris Lattner
lattner at cs.uiuc.edu
Sun May 23 16:03:02 PDT 2004
Changes in directory llvm/lib/Analysis/IPA:
Andersens.cpp added (r1.1)
---
Log message:
Add a simple implementation of Andersen's interprocedural pointer analysis
---
Diffs of the changes: (+1029 -0)
Index: llvm/lib/Analysis/IPA/Andersens.cpp
diff -c /dev/null llvm/lib/Analysis/IPA/Andersens.cpp:1.1
*** /dev/null Sun May 23 16:00:59 2004
--- llvm/lib/Analysis/IPA/Andersens.cpp Sun May 23 16:00:47 2004
***************
*** 0 ****
--- 1,1029 ----
+ //===- Andersens.cpp - Andersen's Interprocedural Alias Analysis -----------==//
+ //
+ // The LLVM Compiler Infrastructure
+ //
+ // This file was developed by the LLVM research group and is distributed under
+ // the University of Illinois Open Source License. See LICENSE.TXT for details.
+ //
+ //===----------------------------------------------------------------------===//
+ //
+ // This file defines a very simple implementation of Andersen's interprocedural
+ // alias analysis. This implementation does not include any of the fancy
+ // features that make Andersen's reasonably efficient (like cycle elimination or
+ // variable substitution), but it should be useful for getting precision
+ // numbers and can be extended in the future.
+ //
+ // In pointer analysis terms, this is a subset-based, flow-insensitive,
+ // field-insensitive, and context-insensitive algorithm pointer algorithm.
+ //
+ // This algorithm is implemented as three stages:
+ // 1. Object identification.
+ // 2. Inclusion constraint identification.
+ // 3. Inclusion constraint solving.
+ //
+ // The object identification stage identifies all of the memory objects in the
+ // program, which includes globals, heap allocated objects, and stack allocated
+ // objects.
+ //
+ // The inclusion constraint identification stage finds all inclusion constraints
+ // in the program by scanning the program, looking for pointer assignments and
+ // other statements that effect the points-to graph. For a statement like "A =
+ // B", this statement is processed to indicate that A can point to anything that
+ // B can point to. Constraints can handle copies, loads, and stores.
+ //
+ // The inclusion constraint solving phase iteratively propagates the inclusion
+ // constraints until a fixed point is reached. This is an O(N^3) algorithm.
+ //
+ // In the initial pass, all indirect function calls are completely ignored. As
+ // the analysis discovers new targets of function pointers, it iteratively
+ // resolves a precise (and conservative) call graph. Also related, this
+ // analysis initially assumes that all internal functions have known incoming
+ // pointers. If we find that an internal function's address escapes outside of
+ // the program, we update this assumption.
+ //
+ //===----------------------------------------------------------------------===//
+
+ #define DEBUG_TYPE "anders-aa"
+ #include "llvm/Constants.h"
+ #include "llvm/DerivedTypes.h"
+ #include "llvm/Instructions.h"
+ #include "llvm/Module.h"
+ #include "llvm/Pass.h"
+ #include "llvm/Support/InstIterator.h"
+ #include "llvm/Support/InstVisitor.h"
+ #include "llvm/Analysis/AliasAnalysis.h"
+ #include "Support/Debug.h"
+ #include "Support/Statistic.h"
+ #include <set>
+ using namespace llvm;
+
+ namespace {
+ Statistic<>
+ NumIters("anders-aa", "Number of iterations to reach convergence");
+ Statistic<>
+ NumConstraints("anders-aa", "Number of constraints");
+ Statistic<>
+ NumNodes("anders-aa", "Number of nodes");
+ Statistic<>
+ NumEscapingFunctions("anders-aa", "Number of internal functions that escape");
+ Statistic<>
+ NumIndirectCallees("anders-aa", "Number of indirect callees found");
+
+ class Andersens : public Pass, public AliasAnalysis,
+ private InstVisitor<Andersens> {
+ /// Node class - This class is used to represent a memory object in the
+ /// program, and is the primitive used to build the points-to graph.
+ class Node {
+ std::vector<Node*> Pointees;
+ Value *Val;
+ public:
+ Node() : Val(0) {}
+ Node *setValue(Value *V) {
+ assert(Val == 0 && "Value already set for this node!");
+ Val = V;
+ return this;
+ }
+
+ /// getValue - Return the LLVM value corresponding to this node.
+ Value *getValue() const { return Val; }
+
+ typedef std::vector<Node*>::const_iterator iterator;
+ iterator begin() const { return Pointees.begin(); }
+ iterator end() const { return Pointees.end(); }
+
+ /// addPointerTo - Add a pointer to the list of pointees of this node,
+ /// returning true if this caused a new pointer to be added, or false if
+ /// we already knew about the points-to relation.
+ bool addPointerTo(Node *N) {
+ std::vector<Node*>::iterator I = std::lower_bound(Pointees.begin(),
+ Pointees.end(),
+ N);
+ if (I != Pointees.end() && *I == N)
+ return false;
+ Pointees.insert(I, N);
+ return true;
+ }
+
+ /// intersects - Return true if the points-to set of this node intersects
+ /// with the points-to set of the specified node.
+ bool intersects(Node *N) const;
+
+ /// intersectsIgnoring - Return true if the points-to set of this node
+ /// intersects with the points-to set of the specified node on any nodes
+ /// except for the specified node to ignore.
+ bool intersectsIgnoring(Node *N, Node *Ignoring) const;
+
+ // Constraint application methods.
+ bool copyFrom(Node *N);
+ bool loadFrom(Node *N);
+ bool storeThrough(Node *N);
+ };
+
+ /// GraphNodes - This vector is populated as part of the object
+ /// identification stage of the analysis, which populates this vector with a
+ /// node for each memory object and fills in the ValueNodes map.
+ std::vector<Node> GraphNodes;
+
+ /// ValueNodes - This map indicates the Node that a particular Value* is
+ /// represented by. This contains entries for all pointers.
+ std::map<Value*, unsigned> ValueNodes;
+
+ /// ObjectNodes - This map contains entries for each memory object in the
+ /// program: globals, alloca's and mallocs.
+ std::map<Value*, unsigned> ObjectNodes;
+
+ /// ReturnNodes - This map contains an entry for each function in the
+ /// program that returns a value.
+ std::map<Function*, unsigned> ReturnNodes;
+
+ /// VarargNodes - This map contains the entry used to represent all pointers
+ /// passed through the varargs portion of a function call for a particular
+ /// function. An entry is not present in this map for functions that do not
+ /// take variable arguments.
+ std::map<Function*, unsigned> VarargNodes;
+
+ /// Constraint - Objects of this structure are used to represent the various
+ /// constraints identified by the algorithm. The constraints are 'copy',
+ /// for statements like "A = B", 'load' for statements like "A = *B", and
+ /// 'store' for statements like "*A = B".
+ struct Constraint {
+ enum ConstraintType { Copy, Load, Store } Type;
+ Node *Dest, *Src;
+
+ Constraint(ConstraintType Ty, Node *D, Node *S)
+ : Type(Ty), Dest(D), Src(S) {}
+ };
+
+ /// Constraints - This vector contains a list of all of the constraints
+ /// identified by the program.
+ std::vector<Constraint> Constraints;
+
+ /// EscapingInternalFunctions - This set contains all of the internal
+ /// functions that are found to escape from the program. If the address of
+ /// an internal function is passed to an external function or otherwise
+ /// escapes from the analyzed portion of the program, we must assume that
+ /// any pointer arguments can alias the universal node. This set keeps
+ /// track of those functions we are assuming to escape so far.
+ std::set<Function*> EscapingInternalFunctions;
+
+ /// IndirectCalls - This contains a list of all of the indirect call sites
+ /// in the program. Since the call graph is iteratively discovered, we may
+ /// need to add constraints to our graph as we find new targets of function
+ /// pointers.
+ std::vector<CallSite> IndirectCalls;
+
+ /// IndirectCallees - For each call site in the indirect calls list, keep
+ /// track of the callees that we have discovered so far. As the analysis
+ /// proceeds, more callees are discovered, until the call graph finally
+ /// stabilizes.
+ std::map<CallSite, std::vector<Function*> > IndirectCallees;
+
+ /// This enum defines the GraphNodes indices that correspond to important
+ /// fixed sets.
+ enum {
+ UniversalSet = 0,
+ NullPtr = 1,
+ NullObject = 2,
+ };
+
+ public:
+ bool run(Module &M) {
+ InitializeAliasAnalysis(this);
+ IdentifyObjects(M);
+ CollectConstraints(M);
+ DEBUG(PrintConstraints());
+ SolveConstraints();
+ DEBUG(PrintPointsToGraph());
+
+ // Free the constraints list, as we don't need it to respond to alias
+ // requests.
+ ObjectNodes.clear();
+ ReturnNodes.clear();
+ VarargNodes.clear();
+ EscapingInternalFunctions.clear();
+ std::vector<Constraint>().swap(Constraints);
+ return false;
+ }
+
+ void releaseMemory() {
+ // FIXME: Until we have transitively required passes working correctly,
+ // this cannot be enabled! Otherwise, using -count-aa with the pass
+ // causes memory to be freed too early. :(
+ #if 0
+ // The memory objects and ValueNodes data structures at the only ones that
+ // are still live after construction.
+ std::vector<Node>().swap(GraphNodes);
+ ValueNodes.clear();
+ #endif
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AliasAnalysis::getAnalysisUsage(AU);
+ AU.setPreservesAll(); // Does not transform code
+ }
+
+ //------------------------------------------------
+ // Implement the AliasAnalysis API
+ //
+ AliasResult alias(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size);
+ void getMustAliases(Value *P, std::vector<Value*> &RetVals);
+ bool pointsToConstantMemory(const Value *P);
+
+ virtual void deleteValue(Value *V) {
+ ValueNodes.erase(V);
+ getAnalysis<AliasAnalysis>().deleteValue(V);
+ }
+
+ virtual void copyValue(Value *From, Value *To) {
+ ValueNodes[To] = ValueNodes[From];
+ getAnalysis<AliasAnalysis>().copyValue(From, To);
+ }
+
+ private:
+ /// getNode - Return the node corresponding to the specified pointer scalar.
+ ///
+ Node *getNode(Value *V) {
+ if (Constant *C = dyn_cast<Constant>(V))
+ return getNodeForConstantPointer(C);
+
+ std::map<Value*, unsigned>::iterator I = ValueNodes.find(V);
+ if (I == ValueNodes.end()) {
+ V->dump();
+ assert(I != ValueNodes.end() &&
+ "Value does not have a node in the points-to graph!");
+ }
+ return &GraphNodes[I->second];
+ }
+
+ /// getObject - Return the node corresponding to the memory object for the
+ /// specified global or allocation instruction.
+ Node *getObject(Value *V) {
+ std::map<Value*, unsigned>::iterator I = ObjectNodes.find(V);
+ assert(I != ObjectNodes.end() &&
+ "Value does not have an object in the points-to graph!");
+ return &GraphNodes[I->second];
+ }
+
+ /// getReturnNode - Return the node representing the return value for the
+ /// specified function.
+ Node *getReturnNode(Function *F) {
+ std::map<Function*, unsigned>::iterator I = ReturnNodes.find(F);
+ assert(I != ReturnNodes.end() && "Function does not return a value!");
+ return &GraphNodes[I->second];
+ }
+
+ /// getVarargNode - Return the node representing the variable arguments
+ /// formal for the specified function.
+ Node *getVarargNode(Function *F) {
+ std::map<Function*, unsigned>::iterator I = VarargNodes.find(F);
+ assert(I != VarargNodes.end() && "Function does not take var args!");
+ return &GraphNodes[I->second];
+ }
+
+ /// getNodeValue - Get the node for the specified LLVM value and set the
+ /// value for it to be the specified value.
+ Node *getNodeValue(Value &V) {
+ return getNode(&V)->setValue(&V);
+ }
+
+ void IdentifyObjects(Module &M);
+ void CollectConstraints(Module &M);
+ void SolveConstraints();
+
+ Node *getNodeForConstantPointer(Constant *C);
+ Node *getNodeForConstantPointerTarget(Constant *C);
+ void AddGlobalInitializerConstraints(Node *N, Constant *C);
+ void AddConstraintsForNonInternalLinkage(Function *F);
+ void AddConstraintsForCall(CallSite CS, Function *F);
+
+
+ void PrintNode(Node *N);
+ void PrintConstraints();
+ void PrintPointsToGraph();
+
+ //===------------------------------------------------------------------===//
+ // Instruction visitation methods for adding constraints
+ //
+ friend class InstVisitor<Andersens>;
+ void visitReturnInst(ReturnInst &RI);
+ void visitInvokeInst(InvokeInst &II) { visitCallSite(CallSite(&II)); }
+ void visitCallInst(CallInst &CI) { visitCallSite(CallSite(&CI)); }
+ void visitCallSite(CallSite CS);
+ void visitAllocationInst(AllocationInst &AI);
+ void visitLoadInst(LoadInst &LI);
+ void visitStoreInst(StoreInst &SI);
+ void visitGetElementPtrInst(GetElementPtrInst &GEP);
+ void visitPHINode(PHINode &PN);
+ void visitCastInst(CastInst &CI);
+ void visitSelectInst(SelectInst &SI);
+ void visitVANext(VANextInst &I);
+ void visitVAArg(VAArgInst &I);
+ void visitInstruction(Instruction &I);
+ };
+
+ RegisterOpt<Andersens> X("anders-aa",
+ "Andersen's Interprocedural Alias Analysis");
+ RegisterAnalysisGroup<AliasAnalysis, Andersens> Y;
+ }
+
+ //===----------------------------------------------------------------------===//
+ // AliasAnalysis Interface Implementation
+ //===----------------------------------------------------------------------===//
+
+ AliasAnalysis::AliasResult Andersens::alias(const Value *V1, unsigned V1Size,
+ const Value *V2, unsigned V2Size) {
+ Node *N1 = getNode((Value*)V1);
+ Node *N2 = getNode((Value*)V2);
+
+ // Check to see if the two pointers are known to not alias. They don't alias
+ // if their points-to sets do not intersect.
+ if (!N1->intersectsIgnoring(N2, &GraphNodes[NullObject]))
+ return NoAlias;
+
+ return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
+ }
+
+ /// getMustAlias - We can provide must alias information if we know that a
+ /// pointer can only point to a specific function or the null pointer.
+ /// Unfortunately we cannot determine must-alias information for global
+ /// variables or any other memory memory objects because we do not track whether
+ /// a pointer points to the beginning of an object or a field of it.
+ void Andersens::getMustAliases(Value *P, std::vector<Value*> &RetVals) {
+ Node *N = getNode(P);
+ Node::iterator I = N->begin();
+ if (I != N->end()) {
+ // If there is exactly one element in the points-to set for the object...
+ ++I;
+ if (I == N->end()) {
+ Node *Pointee = *N->begin();
+
+ // If a function is the only object in the points-to set, then it must be
+ // the destination. Note that we can't handle global variables here,
+ // because we don't know if the pointer is actually pointing to a field of
+ // the global or to the beginning of it.
+ if (Value *V = Pointee->getValue()) {
+ if (Function *F = dyn_cast<Function>(V))
+ RetVals.push_back(F);
+ } else {
+ // If the object in the points-to set is the null object, then the null
+ // pointer is a must alias.
+ if (Pointee == &GraphNodes[NullObject])
+ RetVals.push_back(Constant::getNullValue(P->getType()));
+ }
+ }
+ }
+
+ AliasAnalysis::getMustAliases(P, RetVals);
+ }
+
+ /// pointsToConstantMemory - If we can determine that this pointer only points
+ /// to constant memory, return true. In practice, this means that if the
+ /// pointer can only point to constant globals, functions, or the null pointer,
+ /// return true.
+ ///
+ bool Andersens::pointsToConstantMemory(const Value *P) {
+ Node *N = getNode((Value*)P);
+ for (Node::iterator I = N->begin(), E = N->end(); I != E; ++I) {
+ if (Value *V = (*I)->getValue()) {
+ if (!isa<GlobalValue>(V) || (isa<GlobalVariable>(V) &&
+ !cast<GlobalVariable>(V)->isConstant()))
+ return AliasAnalysis::pointsToConstantMemory(P);
+ } else {
+ if (*I != &GraphNodes[NullObject])
+ return AliasAnalysis::pointsToConstantMemory(P);
+ }
+ }
+
+ return true;
+ }
+
+ //===----------------------------------------------------------------------===//
+ // Object Identification Phase
+ //===----------------------------------------------------------------------===//
+
+ /// IdentifyObjects - This stage scans the program, adding an entry to the
+ /// GraphNodes list for each memory object in the program (global stack or
+ /// heap), and populates the ValueNodes and ObjectNodes maps for these objects.
+ ///
+ void Andersens::IdentifyObjects(Module &M) {
+ unsigned NumObjects = 0;
+
+ // Object #0 is always the universal set: the object that we don't know
+ // anything about.
+ assert(NumObjects == UniversalSet && "Something changed!");
+ ++NumObjects;
+
+ // Object #1 always represents the null pointer.
+ assert(NumObjects == NullPtr && "Something changed!");
+ ++NumObjects;
+
+ // Object #2 always represents the null object (the object pointed to by null)
+ assert(NumObjects == NullObject && "Something changed!");
+ ++NumObjects;
+
+ // Add all the globals first.
+ for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I) {
+ ObjectNodes[I] = NumObjects++;
+ ValueNodes[I] = NumObjects++;
+ }
+
+ // Add nodes for all of the functions and the instructions inside of them.
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+ // The function itself is a memory object.
+ ValueNodes[F] = NumObjects++;
+ ObjectNodes[F] = NumObjects++;
+ if (isa<PointerType>(F->getFunctionType()->getReturnType()))
+ ReturnNodes[F] = NumObjects++;
+ if (F->getFunctionType()->isVarArg())
+ VarargNodes[F] = NumObjects++;
+
+ // Add nodes for all of the incoming pointer arguments.
+ for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
+ if (isa<PointerType>(I->getType()))
+ ValueNodes[I] = NumObjects++;
+
+ // Scan the function body, creating a memory object for each heap/stack
+ // allocation in the body of the function and a node to represent all
+ // pointer values defined by instructions and used as operands.
+ for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) {
+ // If this is an heap or stack allocation, create a node for the memory
+ // object.
+ if (isa<PointerType>(II->getType())) {
+ ValueNodes[&*II] = NumObjects++;
+ if (AllocationInst *AI = dyn_cast<AllocationInst>(&*II))
+ ObjectNodes[AI] = NumObjects++;
+ }
+ }
+ }
+
+ // Now that we know how many objects to create, make them all now!
+ GraphNodes.resize(NumObjects);
+ NumNodes += NumObjects;
+ }
+
+ //===----------------------------------------------------------------------===//
+ // Constraint Identification Phase
+ //===----------------------------------------------------------------------===//
+
+ /// getNodeForConstantPointer - Return the node corresponding to the constant
+ /// pointer itself.
+ Andersens::Node *Andersens::getNodeForConstantPointer(Constant *C) {
+ assert(isa<PointerType>(C->getType()) && "Not a constant pointer!");
+
+ if (isa<ConstantPointerNull>(C))
+ return &GraphNodes[NullPtr];
+ else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(C))
+ return getNode(CPR->getValue());
+ else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
+ switch (CE->getOpcode()) {
+ case Instruction::GetElementPtr:
+ return getNodeForConstantPointer(CE->getOperand(0));
+ case Instruction::Cast:
+ if (isa<PointerType>(CE->getOperand(0)->getType()))
+ return getNodeForConstantPointer(CE->getOperand(0));
+ else
+ return &GraphNodes[UniversalSet];
+ default:
+ std::cerr << "Constant Expr not yet handled: " << *CE << "\n";
+ assert(0);
+ }
+ } else {
+ assert(0 && "Unknown constant pointer!");
+ }
+ }
+
+ /// getNodeForConstantPointerTarget - Return the node POINTED TO by the
+ /// specified constant pointer.
+ Andersens::Node *Andersens::getNodeForConstantPointerTarget(Constant *C) {
+ assert(isa<PointerType>(C->getType()) && "Not a constant pointer!");
+
+ if (isa<ConstantPointerNull>(C))
+ return &GraphNodes[NullObject];
+ else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(C))
+ return getObject(CPR->getValue());
+ else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
+ switch (CE->getOpcode()) {
+ case Instruction::GetElementPtr:
+ return getNodeForConstantPointerTarget(CE->getOperand(0));
+ case Instruction::Cast:
+ if (isa<PointerType>(CE->getOperand(0)->getType()))
+ return getNodeForConstantPointerTarget(CE->getOperand(0));
+ else
+ return &GraphNodes[UniversalSet];
+ default:
+ std::cerr << "Constant Expr not yet handled: " << *CE << "\n";
+ assert(0);
+ }
+ } else {
+ assert(0 && "Unknown constant pointer!");
+ }
+ }
+
+ /// AddGlobalInitializerConstraints - Add inclusion constraints for the memory
+ /// object N, which contains values indicated by C.
+ void Andersens::AddGlobalInitializerConstraints(Node *N, Constant *C) {
+ if (C->getType()->isFirstClassType()) {
+ if (isa<PointerType>(C->getType()))
+ N->addPointerTo(getNodeForConstantPointer(C));
+ } else if (C->isNullValue()) {
+ N->addPointerTo(&GraphNodes[NullObject]);
+ return;
+ } else {
+ // If this is an array or struct, include constraints for each element.
+ assert(isa<ConstantArray>(C) || isa<ConstantStruct>(C));
+ for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
+ AddGlobalInitializerConstraints(N, cast<Constant>(C->getOperand(i)));
+ }
+ }
+
+ void Andersens::AddConstraintsForNonInternalLinkage(Function *F) {
+ for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
+ if (isa<PointerType>(I->getType()))
+ // If this is an argument of an externally accessible function, the
+ // incoming pointer might point to anything.
+ Constraints.push_back(Constraint(Constraint::Copy, getNode(I),
+ &GraphNodes[UniversalSet]));
+ }
+
+
+ /// CollectConstraints - This stage scans the program, adding a constraint to
+ /// the Constraints list for each instruction in the program that induces a
+ /// constraint, and setting up the initial points-to graph.
+ ///
+ void Andersens::CollectConstraints(Module &M) {
+ // First, the universal set points to itself.
+ GraphNodes[UniversalSet].addPointerTo(&GraphNodes[UniversalSet]);
+
+ // Next, the null pointer points to the null object.
+ GraphNodes[NullPtr].addPointerTo(&GraphNodes[NullObject]);
+
+ // Next, add any constraints on global variables and their initializers.
+ for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I) {
+ // Associate the address of the global object as pointing to the memory for
+ // the global: &G = <G memory>
+ Node *Object = getObject(I);
+ Object->setValue(I);
+ getNodeValue(*I)->addPointerTo(Object);
+
+ if (I->hasInitializer()) {
+ AddGlobalInitializerConstraints(Object, I->getInitializer());
+ } else {
+ // If it doesn't have an initializer (i.e. it's defined in another
+ // translation unit), it points to the universal set.
+ Constraints.push_back(Constraint(Constraint::Copy, Object,
+ &GraphNodes[UniversalSet]));
+ }
+ }
+
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+ // Make the function address point to the function object.
+ getNodeValue(*F)->addPointerTo(getObject(F)->setValue(F));
+
+ // Set up the return value node.
+ if (isa<PointerType>(F->getFunctionType()->getReturnType()))
+ getReturnNode(F)->setValue(F);
+ if (F->getFunctionType()->isVarArg())
+ getVarargNode(F)->setValue(F);
+
+ // Set up incoming argument nodes.
+ for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
+ if (isa<PointerType>(I->getType()))
+ getNodeValue(*I);
+
+ if (!F->hasInternalLinkage())
+ AddConstraintsForNonInternalLinkage(F);
+
+ if (!F->isExternal()) {
+ // Scan the function body, creating a memory object for each heap/stack
+ // allocation in the body of the function and a node to represent all
+ // pointer values defined by instructions and used as operands.
+ visit(F);
+ } else {
+ // External functions that return pointers return the universal set.
+ if (isa<PointerType>(F->getFunctionType()->getReturnType()))
+ Constraints.push_back(Constraint(Constraint::Copy,
+ getReturnNode(F),
+ &GraphNodes[UniversalSet]));
+
+ // Any pointers that are passed into the function have the universal set
+ // stored into them.
+ for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
+ if (isa<PointerType>(I->getType())) {
+ // Pointers passed into external functions could have anything stored
+ // through them.
+ Constraints.push_back(Constraint(Constraint::Store, getNode(I),
+ &GraphNodes[UniversalSet]));
+ // Memory objects passed into external function calls can have the
+ // universal set point to them.
+ Constraints.push_back(Constraint(Constraint::Copy,
+ &GraphNodes[UniversalSet],
+ getNode(I)));
+ }
+
+ // If this is an external varargs function, it can also store pointers
+ // into any pointers passed through the varargs section.
+ if (F->getFunctionType()->isVarArg())
+ Constraints.push_back(Constraint(Constraint::Store, getVarargNode(F),
+ &GraphNodes[UniversalSet]));
+ }
+ }
+ NumConstraints += Constraints.size();
+ }
+
+
+ void Andersens::visitInstruction(Instruction &I) {
+ #ifdef NDEBUG
+ return; // This function is just a big assert.
+ #endif
+ if (isa<BinaryOperator>(I))
+ return;
+ // Most instructions don't have any effect on pointer values.
+ switch (I.getOpcode()) {
+ case Instruction::Br:
+ case Instruction::Switch:
+ case Instruction::Unwind:
+ case Instruction::Free:
+ case Instruction::Shl:
+ case Instruction::Shr:
+ return;
+ default:
+ // Is this something we aren't handling yet?
+ std::cerr << "Unknown instruction: " << I;
+ abort();
+ }
+ }
+
+ void Andersens::visitAllocationInst(AllocationInst &AI) {
+ getNodeValue(AI)->addPointerTo(getObject(&AI)->setValue(&AI));
+ }
+
+ void Andersens::visitReturnInst(ReturnInst &RI) {
+ if (RI.getNumOperands() && isa<PointerType>(RI.getOperand(0)->getType()))
+ // return V --> <Copy/retval{F}/v>
+ Constraints.push_back(Constraint(Constraint::Copy,
+ getReturnNode(RI.getParent()->getParent()),
+ getNode(RI.getOperand(0))));
+ }
+
+ void Andersens::visitLoadInst(LoadInst &LI) {
+ if (isa<PointerType>(LI.getType()))
+ // P1 = load P2 --> <Load/P1/P2>
+ Constraints.push_back(Constraint(Constraint::Load, getNodeValue(LI),
+ getNode(LI.getOperand(0))));
+ }
+
+ void Andersens::visitStoreInst(StoreInst &SI) {
+ if (isa<PointerType>(SI.getOperand(0)->getType()))
+ // store P1, P2 --> <Store/P2/P1>
+ Constraints.push_back(Constraint(Constraint::Store,
+ getNode(SI.getOperand(1)),
+ getNode(SI.getOperand(0))));
+ }
+
+ void Andersens::visitGetElementPtrInst(GetElementPtrInst &GEP) {
+ // P1 = getelementptr P2, ... --> <Copy/P1/P2>
+ Constraints.push_back(Constraint(Constraint::Copy, getNodeValue(GEP),
+ getNode(GEP.getOperand(0))));
+ }
+
+ void Andersens::visitPHINode(PHINode &PN) {
+ if (isa<PointerType>(PN.getType())) {
+ Node *PNN = getNodeValue(PN);
+ for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
+ // P1 = phi P2, P3 --> <Copy/P1/P2>, <Copy/P1/P3>, ...
+ Constraints.push_back(Constraint(Constraint::Copy, PNN,
+ getNode(PN.getIncomingValue(i))));
+ }
+ }
+
+ void Andersens::visitCastInst(CastInst &CI) {
+ Value *Op = CI.getOperand(0);
+ if (isa<PointerType>(CI.getType())) {
+ if (isa<PointerType>(Op->getType())) {
+ // P1 = cast P2 --> <Copy/P1/P2>
+ Constraints.push_back(Constraint(Constraint::Copy, getNodeValue(CI),
+ getNode(CI.getOperand(0))));
+ } else {
+ // P1 = cast int --> <Copy/P1/Univ>
+ Constraints.push_back(Constraint(Constraint::Copy, getNodeValue(CI),
+ &GraphNodes[UniversalSet]));
+ }
+ } else if (isa<PointerType>(Op->getType())) {
+ // int = cast P1 --> <Copy/Univ/P1>
+ Constraints.push_back(Constraint(Constraint::Copy,
+ &GraphNodes[UniversalSet],
+ getNode(CI.getOperand(0))));
+ }
+ }
+
+ void Andersens::visitSelectInst(SelectInst &SI) {
+ if (isa<PointerType>(SI.getType())) {
+ Node *SIN = getNodeValue(SI);
+ // P1 = select C, P2, P3 ---> <Copy/P1/P2>, <Copy/P1/P3>
+ Constraints.push_back(Constraint(Constraint::Copy, SIN,
+ getNode(SI.getOperand(1))));
+ Constraints.push_back(Constraint(Constraint::Copy, SIN,
+ getNode(SI.getOperand(2))));
+ }
+ }
+
+ void Andersens::visitVANext(VANextInst &I) {
+ // FIXME: Implement
+ assert(0 && "vanext not handled yet!");
+ }
+ void Andersens::visitVAArg(VAArgInst &I) {
+ assert(0 && "vaarg not handled yet!");
+ }
+
+ /// AddConstraintsForCall - Add constraints for a call with actual arguments
+ /// specified by CS to the function specified by F. Note that the types of
+ /// arguments might not match up in the case where this is an indirect call and
+ /// the function pointer has been casted. If this is the case, do something
+ /// reasonable.
+ void Andersens::AddConstraintsForCall(CallSite CS, Function *F) {
+ if (isa<PointerType>(CS.getType())) {
+ Node *CSN = getNode(CS.getInstruction());
+ if (isa<PointerType>(F->getFunctionType()->getReturnType())) {
+ Constraints.push_back(Constraint(Constraint::Copy, CSN,
+ getReturnNode(F)));
+ } else {
+ // If the function returns a non-pointer value, handle this just like we
+ // treat a nonpointer cast to pointer.
+ Constraints.push_back(Constraint(Constraint::Copy, CSN,
+ &GraphNodes[UniversalSet]));
+ }
+ } else if (isa<PointerType>(F->getFunctionType()->getReturnType())) {
+ Constraints.push_back(Constraint(Constraint::Copy,
+ &GraphNodes[UniversalSet],
+ getReturnNode(F)));
+ }
+
+ Function::aiterator AI = F->abegin(), AE = F->aend();
+ CallSite::arg_iterator ArgI = CS.arg_begin(), ArgE = CS.arg_end();
+ for (; AI != AE && ArgI != ArgE; ++AI, ++ArgI)
+ if (isa<PointerType>(AI->getType())) {
+ if (isa<PointerType>((*ArgI)->getType())) {
+ // Copy the actual argument into the formal argument.
+ Constraints.push_back(Constraint(Constraint::Copy, getNode(AI),
+ getNode(*ArgI)));
+ } else {
+ Constraints.push_back(Constraint(Constraint::Copy, getNode(AI),
+ &GraphNodes[UniversalSet]));
+ }
+ } else if (isa<PointerType>((*ArgI)->getType())) {
+ Constraints.push_back(Constraint(Constraint::Copy,
+ &GraphNodes[UniversalSet],
+ getNode(*ArgI)));
+ }
+
+ // Copy all pointers passed through the varargs section to the varargs node.
+ if (F->getFunctionType()->isVarArg())
+ for (; ArgI != ArgE; ++ArgI)
+ if (isa<PointerType>((*ArgI)->getType()))
+ Constraints.push_back(Constraint(Constraint::Copy, getVarargNode(F),
+ getNode(*ArgI)));
+ // If more arguments are passed in than we track, just drop them on the floor.
+ }
+
+ void Andersens::visitCallSite(CallSite CS) {
+ if (isa<PointerType>(CS.getType()))
+ getNodeValue(*CS.getInstruction());
+
+ if (Function *F = CS.getCalledFunction()) {
+ AddConstraintsForCall(CS, F);
+ } else {
+ // We don't handle indirect call sites yet. Keep track of them for when we
+ // discover the call graph incrementally.
+ IndirectCalls.push_back(CS);
+ }
+ }
+
+ //===----------------------------------------------------------------------===//
+ // Constraint Solving Phase
+ //===----------------------------------------------------------------------===//
+
+ /// intersects - Return true if the points-to set of this node intersects
+ /// with the points-to set of the specified node.
+ bool Andersens::Node::intersects(Node *N) const {
+ iterator I1 = begin(), I2 = N->begin(), E1 = end(), E2 = N->end();
+ while (I1 != E1 && I2 != E2) {
+ if (*I1 == *I2) return true;
+ if (*I1 < *I2)
+ ++I1;
+ else
+ ++I2;
+ }
+ return false;
+ }
+
+ /// intersectsIgnoring - Return true if the points-to set of this node
+ /// intersects with the points-to set of the specified node on any nodes
+ /// except for the specified node to ignore.
+ bool Andersens::Node::intersectsIgnoring(Node *N, Node *Ignoring) const {
+ iterator I1 = begin(), I2 = N->begin(), E1 = end(), E2 = N->end();
+ while (I1 != E1 && I2 != E2) {
+ if (*I1 == *I2) {
+ if (*I1 != Ignoring) return true;
+ ++I1; ++I2;
+ } else if (*I1 < *I2)
+ ++I1;
+ else
+ ++I2;
+ }
+ return false;
+ }
+
+ // Copy constraint: all edges out of the source node get copied to the
+ // destination node. This returns true if a change is made.
+ bool Andersens::Node::copyFrom(Node *N) {
+ // Use a mostly linear-time merge since both of the lists are sorted.
+ bool Changed = false;
+ iterator I = N->begin(), E = N->end();
+ unsigned i = 0;
+ while (I != E && i != Pointees.size()) {
+ if (Pointees[i] < *I) {
+ ++i;
+ } else if (Pointees[i] == *I) {
+ ++i; ++I;
+ } else {
+ // We found a new element to copy over.
+ Changed = true;
+ Pointees.insert(Pointees.begin()+i, *I);
+ ++i; ++I;
+ }
+ }
+
+ if (I != E) {
+ Pointees.insert(Pointees.end(), I, E);
+ Changed = true;
+ }
+
+ return Changed;
+ }
+
+ bool Andersens::Node::loadFrom(Node *N) {
+ bool Changed = false;
+ for (iterator I = N->begin(), E = N->end(); I != E; ++I)
+ Changed |= copyFrom(*I);
+ return Changed;
+ }
+
+ bool Andersens::Node::storeThrough(Node *N) {
+ bool Changed = false;
+ for (iterator I = begin(), E = end(); I != E; ++I)
+ Changed |= (*I)->copyFrom(N);
+ return Changed;
+ }
+
+
+ /// SolveConstraints - This stage iteratively processes the constraints list
+ /// propagating constraints (adding edges to the Nodes in the points-to graph)
+ /// until a fixed point is reached.
+ ///
+ void Andersens::SolveConstraints() {
+ bool Changed = true;
+ unsigned Iteration = 0;
+ while (Changed) {
+ Changed = false;
+ ++NumIters;
+ DEBUG(std::cerr << "Starting iteration #" << Iteration++ << "!\n");
+
+ // Loop over all of the constraints, applying them in turn.
+ for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
+ Constraint &C = Constraints[i];
+ switch (C.Type) {
+ case Constraint::Copy:
+ Changed |= C.Dest->copyFrom(C.Src);
+ break;
+ case Constraint::Load:
+ Changed |= C.Dest->loadFrom(C.Src);
+ break;
+ case Constraint::Store:
+ Changed |= C.Dest->storeThrough(C.Src);
+ break;
+ default:
+ assert(0 && "Unknown constraint!");
+ }
+ }
+
+ if (Changed) {
+ // Check to see if any internal function's addresses have been passed to
+ // external functions. If so, we have to assume that their incoming
+ // arguments could be anything. If there are any internal functions in
+ // the universal node that we don't know about, we must iterate.
+ for (Node::iterator I = GraphNodes[UniversalSet].begin(),
+ E = GraphNodes[UniversalSet].end(); I != E; ++I)
+ if (Function *F = dyn_cast_or_null<Function>((*I)->getValue()))
+ if (F->hasInternalLinkage() &&
+ EscapingInternalFunctions.insert(F).second) {
+ // We found a function that is just now escaping. Mark it as if it
+ // didn't have internal linkage.
+ AddConstraintsForNonInternalLinkage(F);
+ DEBUG(std::cerr << "Found escaping internal function: "
+ << F->getName() << "\n");
+ ++NumEscapingFunctions;
+ }
+
+ // Check to see if we have discovered any new callees of the indirect call
+ // sites. If so, add constraints to the analysis.
+ for (unsigned i = 0, e = IndirectCalls.size(); i != e; ++i) {
+ CallSite CS = IndirectCalls[i];
+ std::vector<Function*> &KnownCallees = IndirectCallees[CS];
+ Node *CN = getNode(CS.getCalledValue());
+
+ for (Node::iterator NI = CN->begin(), E = CN->end(); NI != E; ++NI)
+ if (Function *F = dyn_cast_or_null<Function>((*NI)->getValue())) {
+ std::vector<Function*>::iterator IP =
+ std::lower_bound(KnownCallees.begin(), KnownCallees.end(), F);
+ if (IP == KnownCallees.end() || *IP != F) {
+ // Add the constraints for the call now.
+ AddConstraintsForCall(CS, F);
+ DEBUG(std::cerr << "Found actual callee '"
+ << F->getName() << "' for call: "
+ << *CS.getInstruction() << "\n");
+ ++NumIndirectCallees;
+ KnownCallees.insert(IP, F);
+ }
+ }
+ }
+ }
+ }
+ }
+
+
+
+ //===----------------------------------------------------------------------===//
+ // Debugging Output
+ //===----------------------------------------------------------------------===//
+
+ void Andersens::PrintNode(Node *N) {
+ if (N == &GraphNodes[UniversalSet]) {
+ std::cerr << "<universal>";
+ return;
+ } else if (N == &GraphNodes[NullPtr]) {
+ std::cerr << "<nullptr>";
+ return;
+ } else if (N == &GraphNodes[NullObject]) {
+ std::cerr << "<null>";
+ return;
+ }
+
+ assert(N->getValue() != 0 && "Never set node label!");
+ Value *V = N->getValue();
+ if (Function *F = dyn_cast<Function>(V)) {
+ if (isa<PointerType>(F->getFunctionType()->getReturnType()) &&
+ N == getReturnNode(F)) {
+ std::cerr << F->getName() << ":retval";
+ return;
+ } else if (F->getFunctionType()->isVarArg() && N == getVarargNode(F)) {
+ std::cerr << F->getName() << ":vararg";
+ return;
+ }
+ }
+
+ if (Instruction *I = dyn_cast<Instruction>(V))
+ std::cerr << I->getParent()->getParent()->getName() << ":";
+ else if (Argument *Arg = dyn_cast<Argument>(V))
+ std::cerr << Arg->getParent()->getName() << ":";
+
+ if (V->hasName())
+ std::cerr << V->getName();
+ else
+ std::cerr << "(unnamed)";
+
+ if (isa<GlobalValue>(V) || isa<AllocationInst>(V))
+ if (N == getObject(V))
+ std::cerr << "<mem>";
+ }
+
+ void Andersens::PrintConstraints() {
+ std::cerr << "Constraints:\n";
+ for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
+ std::cerr << " #" << i << ": ";
+ Constraint &C = Constraints[i];
+ if (C.Type == Constraint::Store)
+ std::cerr << "*";
+ PrintNode(C.Dest);
+ std::cerr << " = ";
+ if (C.Type == Constraint::Load)
+ std::cerr << "*";
+ PrintNode(C.Src);
+ std::cerr << "\n";
+ }
+ }
+
+ void Andersens::PrintPointsToGraph() {
+ std::cerr << "Points-to graph:\n";
+ for (unsigned i = 0, e = GraphNodes.size(); i != e; ++i) {
+ Node *N = &GraphNodes[i];
+ std::cerr << "[" << (N->end() - N->begin()) << "] ";
+ PrintNode(N);
+ std::cerr << "\t--> ";
+ for (Node::iterator I = N->begin(), E = N->end(); I != E; ++I) {
+ if (I != N->begin()) std::cerr << ", ";
+ PrintNode(*I);
+ }
+ std::cerr << "\n";
+ }
+ }
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