//===- 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.
+// This file defines an implementation of Andersen's interprocedural alias
+// analysis
//
// In pointer analysis terms, this is a subset-based, flow-insensitive,
-// field-insensitive, and context-insensitive algorithm pointer algorithm.
+// field-sensitive, and context-insensitive algorithm pointer algorithm.
//
// This algorithm is implemented as three stages:
// 1. Object identification.
// 2. Inclusion constraint identification.
-// 3. Inclusion constraint solving.
+// 3. Offline constraint graph optimization
+// 4. 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
// 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.
+// B can point to. Constraints can handle copies, loads, and stores, and
+// address taking.
+//
+// The offline constraint graph optimization portion includes offline variable
+// substitution algorithms intended to computer pointer and location
+// equivalences. Pointer equivalences are those pointers that will have the
+// same points-to sets, and location equivalences are those variables that
+// always appear together in points-to sets.
//
// 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.
+// Function constraints are handled as if they were structs with X fields.
+// Thus, an access to argument X of function Y is an access to node index
+// getNode(Y) + X. This representation allows handling of indirect calls
+// without any issues. To wit, an indirect call Y(a,b) is equivalent to
+// *(Y + 1) = a, *(Y + 2) = b.
+// The return node for a function is always located at getNode(F) +
+// CallReturnPos. The arguments start at getNode(F) + CallArgPos.
//
// Future Improvements:
-// This implementation of Andersen's algorithm is extremely slow. To make it
-// scale reasonably well, the inclusion constraints could be sorted (easy),
-// offline variable substitution would be a huge win (straight-forward), and
-// online cycle elimination (trickier) might help as well.
-//
+// Offline detection of online cycles. Use of BDD's.
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "anders-aa"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
+#include "llvm/Support/Compiler.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 "llvm/Analysis/Passes.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SparseBitVector.h"
+#include "llvm/ADT/DenseSet.h"
+#include <algorithm>
#include <set>
+#include <list>
+#include <stack>
+#include <vector>
+#include <queue>
+
+// Determining the actual set of nodes the universal set can consist of is very
+// expensive because it means propagating around very large sets. We rely on
+// other analysis being able to determine which nodes can never be pointed to in
+// order to disambiguate further than "points-to anything".
+#define FULL_UNIVERSAL 0
+
using namespace llvm;
+STATISTIC(NumIters , "Number of iterations to reach convergence");
+STATISTIC(NumConstraints, "Number of constraints");
+STATISTIC(NumNodes , "Number of nodes");
+STATISTIC(NumUnified , "Number of variables unified");
+STATISTIC(NumErased , "Number of redundant constraints erased");
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;
+ const unsigned SelfRep = (unsigned)-1;
+ const unsigned Unvisited = (unsigned)-1;
+ // Position of the function return node relative to the function node.
+ const unsigned CallReturnPos = 1;
+ // Position of the function call node relative to the function node.
+ const unsigned CallFirstArgPos = 2;
+
+ struct BitmapKeyInfo {
+ static inline SparseBitVector<> *getEmptyKey() {
+ return reinterpret_cast<SparseBitVector<> *>(-1);
+ }
+ static inline SparseBitVector<> *getTombstoneKey() {
+ return reinterpret_cast<SparseBitVector<> *>(-2);
+ }
+ static unsigned getHashValue(const SparseBitVector<> *bitmap) {
+ return bitmap->getHashValue();
+ }
+ static bool isEqual(const SparseBitVector<> *LHS,
+ const SparseBitVector<> *RHS) {
+ if (LHS == RHS)
+ return true;
+ else if (LHS == getEmptyKey() || RHS == getEmptyKey()
+ || LHS == getTombstoneKey() || RHS == getTombstoneKey())
+ return false;
+
+ return *LHS == *RHS;
+ }
+
+ static bool isPod() { return true; }
+ };
+
+ class VISIBILITY_HIDDEN Andersens : public ModulePass, public AliasAnalysis,
+ private InstVisitor<Andersens> {
+ struct Node;
+
+ /// 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",
+ /// 'store' for statements like "*A = B", and AddressOf for statements like
+ /// A = alloca; The Offset is applied as *(A + K) = B for stores,
+ /// A = *(B + K) for loads, and A = B + K for copies. It is
+ /// illegal on addressof constraints (because it is statically
+ /// resolvable to A = &C where C = B + K)
+
+ struct Constraint {
+ enum ConstraintType { Copy, Load, Store, AddressOf } Type;
+ unsigned Dest;
+ unsigned Src;
+ unsigned Offset;
+
+ Constraint(ConstraintType Ty, unsigned D, unsigned S, unsigned O = 0)
+ : Type(Ty), Dest(D), Src(S), Offset(O) {
+ assert(Offset == 0 || Ty != AddressOf &&
+ "Offset is illegal on addressof constraints");
+ }
+
+ bool operator==(const Constraint &RHS) const {
+ return RHS.Type == Type
+ && RHS.Dest == Dest
+ && RHS.Src == Src
+ && RHS.Offset == Offset;
+ }
+
+ bool operator!=(const Constraint &RHS) const {
+ return !(*this == RHS);
+ }
+
+ bool operator<(const Constraint &RHS) const {
+ if (RHS.Type != Type)
+ return RHS.Type < Type;
+ else if (RHS.Dest != Dest)
+ return RHS.Dest < Dest;
+ else if (RHS.Src != Src)
+ return RHS.Src < Src;
+ return RHS.Offset < Offset;
+ }
+ };
+
+ // Information DenseSet requires implemented in order to be able to do
+ // it's thing
+ struct PairKeyInfo {
+ static inline std::pair<unsigned, unsigned> getEmptyKey() {
+ return std::make_pair(~0UL, ~0UL);
+ }
+ static inline std::pair<unsigned, unsigned> getTombstoneKey() {
+ return std::make_pair(~0UL - 1, ~0UL - 1);
+ }
+ static unsigned getHashValue(const std::pair<unsigned, unsigned> &P) {
+ return P.first ^ P.second;
+ }
+ static unsigned isEqual(const std::pair<unsigned, unsigned> &LHS,
+ const std::pair<unsigned, unsigned> &RHS) {
+ return LHS == RHS;
+ }
+ };
+
+ struct ConstraintKeyInfo {
+ static inline Constraint getEmptyKey() {
+ return Constraint(Constraint::Copy, ~0UL, ~0UL, ~0UL);
+ }
+ static inline Constraint getTombstoneKey() {
+ return Constraint(Constraint::Copy, ~0UL - 1, ~0UL - 1, ~0UL - 1);
+ }
+ static unsigned getHashValue(const Constraint &C) {
+ return C.Src ^ C.Dest ^ C.Type ^ C.Offset;
+ }
+ static bool isEqual(const Constraint &LHS,
+ const Constraint &RHS) {
+ return LHS.Type == RHS.Type && LHS.Dest == RHS.Dest
+ && LHS.Src == RHS.Src && LHS.Offset == RHS.Offset;
+ }
+ };
+
+ // Node class - This class is used to represent a node in the constraint
+ // graph. Due to various optimizations, it is not always the case that
+ // there is a mapping from a Node to a Value. In particular, we add
+ // artificial Node's that represent the set of pointed-to variables shared
+ // for each location equivalent Node.
+ struct Node {
+ private:
+ static unsigned Counter;
+
public:
- Node() : Val(0) {}
+ Value *Val;
+ SparseBitVector<> *Edges;
+ SparseBitVector<> *PointsTo;
+ SparseBitVector<> *OldPointsTo;
+ std::list<Constraint> Constraints;
+
+ // Pointer and location equivalence labels
+ unsigned PointerEquivLabel;
+ unsigned LocationEquivLabel;
+ // Predecessor edges, both real and implicit
+ SparseBitVector<> *PredEdges;
+ SparseBitVector<> *ImplicitPredEdges;
+ // Set of nodes that point to us, only use for location equivalence.
+ SparseBitVector<> *PointedToBy;
+ // Number of incoming edges, used during variable substitution to early
+ // free the points-to sets
+ unsigned NumInEdges;
+ // True if our points-to set is in the Set2PEClass map
+ bool StoredInHash;
+ // True if our node has no indirect constraints (complex or otherwise)
+ bool Direct;
+ // True if the node is address taken, *or* it is part of a group of nodes
+ // that must be kept together. This is set to true for functions and
+ // their arg nodes, which must be kept at the same position relative to
+ // their base function node.
+ bool AddressTaken;
+
+ // Nodes in cycles (or in equivalence classes) are united together using a
+ // standard union-find representation with path compression. NodeRep
+ // gives the index into GraphNodes for the representative Node.
+ unsigned NodeRep;
+
+ // Modification timestamp. Assigned from Counter.
+ // Used for work list prioritization.
+ unsigned Timestamp;
+
+ Node(bool direct = true) :
+ Val(0), Edges(0), PointsTo(0), OldPointsTo(0),
+ PointerEquivLabel(0), LocationEquivLabel(0), PredEdges(0),
+ ImplicitPredEdges(0), PointedToBy(0), NumInEdges(0),
+ StoredInHash(false), Direct(direct), AddressTaken(false),
+ NodeRep(SelfRep), Timestamp(0) { }
+
Node *setValue(Value *V) {
assert(Val == 0 && "Value already set for this node!");
Val = V;
}
/// 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;
+ bool addPointerTo(unsigned Node) {
+ return PointsTo->test_and_set(Node);
}
/// intersects - Return true if the points-to set of this node intersects
/// 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;
+ bool intersectsIgnoring(Node *N, unsigned) const;
- // Constraint application methods.
- bool copyFrom(Node *N);
- bool loadFrom(Node *N);
- bool storeThrough(Node *N);
+ // Timestamp a node (used for work list prioritization)
+ void Stamp() {
+ Timestamp = Counter++;
+ }
+
+ bool isRep() {
+ return( (int) NodeRep < 0 );
+ }
+ };
+
+ struct WorkListElement {
+ Node* node;
+ unsigned Timestamp;
+ WorkListElement(Node* n, unsigned t) : node(n), Timestamp(t) {}
+
+ // Note that we reverse the sense of the comparison because we
+ // actually want to give low timestamps the priority over high,
+ // whereas priority is typically interpreted as a greater value is
+ // given high priority.
+ bool operator<(const WorkListElement& that) const {
+ return( this->Timestamp > that.Timestamp );
+ }
+ };
+
+ // Priority-queue based work list specialized for Nodes.
+ class WorkList {
+ std::priority_queue<WorkListElement> Q;
+
+ public:
+ void insert(Node* n) {
+ Q.push( WorkListElement(n, n->Timestamp) );
+ }
+
+ // We automatically discard non-representative nodes and nodes
+ // that were in the work list twice (we keep a copy of the
+ // timestamp in the work list so we can detect this situation by
+ // comparing against the node's current timestamp).
+ Node* pop() {
+ while( !Q.empty() ) {
+ WorkListElement x = Q.top(); Q.pop();
+ Node* INode = x.node;
+
+ if( INode->isRep() &&
+ INode->Timestamp == x.Timestamp ) {
+ return(x.node);
+ }
+ }
+ return(0);
+ }
+
+ bool empty() {
+ return Q.empty();
+ }
};
/// GraphNodes - This vector is populated as part of the object
/// ValueNodes - This map indicates the Node that a particular Value* is
/// represented by. This contains entries for all pointers.
- std::map<Value*, unsigned> ValueNodes;
+ DenseMap<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;
+ /// program: globals, alloca's and mallocs.
+ DenseMap<Value*, unsigned> ObjectNodes;
/// ReturnNodes - This map contains an entry for each function in the
/// program that returns a value.
- std::map<Function*, unsigned> ReturnNodes;
+ DenseMap<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;
+ DenseMap<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;
+ // Map from graph node to maximum K value that is allowed (for functions,
+ // this is equivalent to the number of arguments + CallFirstArgPos)
+ std::map<unsigned, unsigned> MaxK;
/// This enum defines the GraphNodes indices that correspond to important
/// fixed sets.
UniversalSet = 0,
NullPtr = 1,
NullObject = 2,
+ NumberSpecialNodes
};
-
+ // Stack for Tarjan's
+ std::stack<unsigned> SCCStack;
+ // Map from Graph Node to DFS number
+ std::vector<unsigned> Node2DFS;
+ // Map from Graph Node to Deleted from graph.
+ std::vector<bool> Node2Deleted;
+ // Same as Node Maps, but implemented as std::map because it is faster to
+ // clear
+ std::map<unsigned, unsigned> Tarjan2DFS;
+ std::map<unsigned, bool> Tarjan2Deleted;
+ // Current DFS number
+ unsigned DFSNumber;
+
+ // Work lists.
+ WorkList w1, w2;
+ WorkList *CurrWL, *NextWL; // "current" and "next" work lists
+
+ // Offline variable substitution related things
+
+ // Temporary rep storage, used because we can't collapse SCC's in the
+ // predecessor graph by uniting the variables permanently, we can only do so
+ // for the successor graph.
+ std::vector<unsigned> VSSCCRep;
+ // Mapping from node to whether we have visited it during SCC finding yet.
+ std::vector<bool> Node2Visited;
+ // During variable substitution, we create unknowns to represent the unknown
+ // value that is a dereference of a variable. These nodes are known as
+ // "ref" nodes (since they represent the value of dereferences).
+ unsigned FirstRefNode;
+ // During HVN, we create represent address taken nodes as if they were
+ // unknown (since HVN, unlike HU, does not evaluate unions).
+ unsigned FirstAdrNode;
+ // Current pointer equivalence class number
+ unsigned PEClass;
+ // Mapping from points-to sets to equivalence classes
+ typedef DenseMap<SparseBitVector<> *, unsigned, BitmapKeyInfo> BitVectorMap;
+ BitVectorMap Set2PEClass;
+ // Mapping from pointer equivalences to the representative node. -1 if we
+ // have no representative node for this pointer equivalence class yet.
+ std::vector<int> PEClass2Node;
+ // Mapping from pointer equivalences to representative node. This includes
+ // pointer equivalent but not location equivalent variables. -1 if we have
+ // no representative node for this pointer equivalence class yet.
+ std::vector<int> PENLEClass2Node;
+
public:
- bool run(Module &M) {
+ static char ID;
+ Andersens() : ModulePass((intptr_t)&ID) {}
+
+ bool runOnModule(Module &M) {
InitializeAliasAnalysis(this);
IdentifyObjects(M);
CollectConstraints(M);
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa-constraints"
DEBUG(PrintConstraints());
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa"
SolveConstraints();
DEBUG(PrintPointsToGraph());
ObjectNodes.clear();
ReturnNodes.clear();
VarargNodes.clear();
- EscapingInternalFunctions.clear();
- std::vector<Constraint>().swap(Constraints);
+ std::vector<Constraint>().swap(Constraints);
return false;
}
//------------------------------------------------
// Implement the AliasAnalysis API
- //
+ //
AliasResult alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size);
+ virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
+ virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
void getMustAliases(Value *P, std::vector<Value*> &RetVals);
bool pointsToConstantMemory(const Value *P);
private:
/// getNode - Return the node corresponding to the specified pointer scalar.
///
- Node *getNode(Value *V) {
+ unsigned getNode(Value *V) {
if (Constant *C = dyn_cast<Constant>(V))
if (!isa<GlobalValue>(C))
return getNodeForConstantPointer(C);
- std::map<Value*, unsigned>::iterator I = ValueNodes.find(V);
+ DenseMap<Value*, unsigned>::iterator I = ValueNodes.find(V);
if (I == ValueNodes.end()) {
+#ifndef NDEBUG
V->dump();
- assert(I != ValueNodes.end() &&
- "Value does not have a node in the points-to graph!");
+#endif
+ assert(0 && "Value does not have a node in the points-to graph!");
}
- return &GraphNodes[I->second];
+ return 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);
+ unsigned getObject(Value *V) {
+ DenseMap<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];
+ return 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);
+ unsigned getReturnNode(Function *F) {
+ DenseMap<Function*, unsigned>::iterator I = ReturnNodes.find(F);
assert(I != ReturnNodes.end() && "Function does not return a value!");
- return &GraphNodes[I->second];
+ return 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);
+ unsigned getVarargNode(Function *F) {
+ DenseMap<Function*, unsigned>::iterator I = VarargNodes.find(F);
assert(I != VarargNodes.end() && "Function does not take var args!");
- return &GraphNodes[I->second];
+ return 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);
+ unsigned getNodeValue(Value &V) {
+ unsigned Index = getNode(&V);
+ GraphNodes[Index].setValue(&V);
+ return Index;
}
+ unsigned UniteNodes(unsigned First, unsigned Second,
+ bool UnionByRank = true);
+ unsigned FindNode(unsigned Node);
+
void IdentifyObjects(Module &M);
void CollectConstraints(Module &M);
+ bool AnalyzeUsesOfFunction(Value *);
+ void CreateConstraintGraph();
+ void OptimizeConstraints();
+ unsigned FindEquivalentNode(unsigned, unsigned);
+ void ClumpAddressTaken();
+ void RewriteConstraints();
+ void HU();
+ void HVN();
+ void UnitePointerEquivalences();
void SolveConstraints();
+ bool QueryNode(unsigned Node);
+ void Condense(unsigned Node);
+ void HUValNum(unsigned Node);
+ void HVNValNum(unsigned Node);
+ unsigned getNodeForConstantPointer(Constant *C);
+ unsigned getNodeForConstantPointerTarget(Constant *C);
+ void AddGlobalInitializerConstraints(unsigned, Constant *C);
- Node *getNodeForConstantPointer(Constant *C);
- Node *getNodeForConstantPointerTarget(Constant *C);
- void AddGlobalInitializerConstraints(Node *N, Constant *C);
void AddConstraintsForNonInternalLinkage(Function *F);
void AddConstraintsForCall(CallSite CS, Function *F);
+ bool AddConstraintsForExternalCall(CallSite CS, Function *F);
void PrintNode(Node *N);
void PrintConstraints();
+ void PrintConstraint(const Constraint &);
+ void PrintLabels();
void PrintPointsToGraph();
//===------------------------------------------------------------------===//
void visitGetElementPtrInst(GetElementPtrInst &GEP);
void visitPHINode(PHINode &PN);
void visitCastInst(CastInst &CI);
+ void visitICmpInst(ICmpInst &ICI) {} // NOOP!
+ void visitFCmpInst(FCmpInst &ICI) {} // NOOP!
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;
+ char Andersens::ID = 0;
+ RegisterPass<Andersens> X("anders-aa",
+ "Andersen's Interprocedural Alias Analysis");
+ RegisterAnalysisGroup<AliasAnalysis> Y(X);
+
+ // Initialize Timestamp Counter (static).
+ unsigned Andersens::Node::Counter = 0;
}
+ModulePass *llvm::createAndersensPass() { return new Andersens(); }
+
//===----------------------------------------------------------------------===//
// 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);
+ Node *N1 = &GraphNodes[FindNode(getNode(const_cast<Value*>(V1)))];
+ Node *N2 = &GraphNodes[FindNode(getNode(const_cast<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]))
+ if (!N1->intersectsIgnoring(N2, NullObject))
return NoAlias;
return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
}
+AliasAnalysis::ModRefResult
+Andersens::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
+ // The only thing useful that we can contribute for mod/ref information is
+ // when calling external function calls: if we know that memory never escapes
+ // from the program, it cannot be modified by an external call.
+ //
+ // NOTE: This is not really safe, at least not when the entire program is not
+ // available. The deal is that the external function could call back into the
+ // program and modify stuff. We ignore this technical niggle for now. This
+ // is, after all, a "research quality" implementation of Andersen's analysis.
+ if (Function *F = CS.getCalledFunction())
+ if (F->isDeclaration()) {
+ Node *N1 = &GraphNodes[FindNode(getNode(P))];
+
+ if (N1->PointsTo->empty())
+ return NoModRef;
+
+ if (!N1->PointsTo->test(UniversalSet))
+ return NoModRef; // P doesn't point to the universal set.
+ }
+
+ return AliasAnalysis::getModRefInfo(CS, P, Size);
+}
+
+AliasAnalysis::ModRefResult
+Andersens::getModRefInfo(CallSite CS1, CallSite CS2) {
+ return AliasAnalysis::getModRefInfo(CS1,CS2);
+}
+
/// 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()));
- }
+ Node *N = &GraphNodes[FindNode(getNode(P))];
+ if (N->PointsTo->count() == 1) {
+ Node *Pointee = &GraphNodes[N->PointsTo->find_first()];
+ // 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);
}
/// 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()) {
+ Node *N = &GraphNodes[FindNode(getNode((Value*)P))];
+ unsigned i;
+
+ for (SparseBitVector<>::iterator bi = N->PointsTo->begin();
+ bi != N->PointsTo->end();
+ ++bi) {
+ i = *bi;
+ Node *Pointee = &GraphNodes[i];
+ if (Value *V = Pointee->getValue()) {
if (!isa<GlobalValue>(V) || (isa<GlobalVariable>(V) &&
!cast<GlobalVariable>(V)->isConstant()))
return AliasAnalysis::pointsToConstantMemory(P);
} else {
- if (*I != &GraphNodes[NullObject])
+ if (i != NullObject)
return AliasAnalysis::pointsToConstantMemory(P);
}
}
++NumObjects;
// Add all the globals first.
- for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I) {
+ for (Module::global_iterator I = M.global_begin(), E = M.global_end();
+ 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.
+ unsigned First = NumObjects;
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++;
+ for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
+ I != E; ++I)
+ {
+ if (isa<PointerType>(I->getType()))
+ ValueNodes[I] = NumObjects++;
+ }
+ MaxK[First] = NumObjects - First;
// 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
if (AllocationInst *AI = dyn_cast<AllocationInst>(&*II))
ObjectNodes[AI] = NumObjects++;
}
+
+ // Calls to inline asm need to be added as well because the callee isn't
+ // referenced anywhere else.
+ if (CallInst *CI = dyn_cast<CallInst>(&*II)) {
+ Value *Callee = CI->getCalledValue();
+ if (isa<InlineAsm>(Callee))
+ ValueNodes[Callee] = NumObjects++;
+ }
}
}
/// getNodeForConstantPointer - Return the node corresponding to the constant
/// pointer itself.
-Andersens::Node *Andersens::getNodeForConstantPointer(Constant *C) {
+unsigned Andersens::getNodeForConstantPointer(Constant *C) {
assert(isa<PointerType>(C->getType()) && "Not a constant pointer!");
- if (isa<ConstantPointerNull>(C))
- return &GraphNodes[NullPtr];
+ if (isa<ConstantPointerNull>(C) || isa<UndefValue>(C))
+ return NullPtr;
else if (GlobalValue *GV = dyn_cast<GlobalValue>(C))
return getNode(GV);
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];
+ case Instruction::IntToPtr:
+ return UniversalSet;
+ case Instruction::BitCast:
+ return getNodeForConstantPointer(CE->getOperand(0));
default:
- std::cerr << "Constant Expr not yet handled: " << *CE << "\n";
+ cerr << "Constant Expr not yet handled: " << *CE << "\n";
assert(0);
}
} else {
/// getNodeForConstantPointerTarget - Return the node POINTED TO by the
/// specified constant pointer.
-Andersens::Node *Andersens::getNodeForConstantPointerTarget(Constant *C) {
+unsigned Andersens::getNodeForConstantPointerTarget(Constant *C) {
assert(isa<PointerType>(C->getType()) && "Not a constant pointer!");
if (isa<ConstantPointerNull>(C))
- return &GraphNodes[NullObject];
+ return NullObject;
else if (GlobalValue *GV = dyn_cast<GlobalValue>(C))
return getObject(GV);
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];
+ case Instruction::IntToPtr:
+ return UniversalSet;
+ case Instruction::BitCast:
+ return getNodeForConstantPointerTarget(CE->getOperand(0));
default:
- std::cerr << "Constant Expr not yet handled: " << *CE << "\n";
+ cerr << "Constant Expr not yet handled: " << *CE << "\n";
assert(0);
}
} else {
/// AddGlobalInitializerConstraints - Add inclusion constraints for the memory
/// object N, which contains values indicated by C.
-void Andersens::AddGlobalInitializerConstraints(Node *N, Constant *C) {
+void Andersens::AddGlobalInitializerConstraints(unsigned NodeIndex,
+ Constant *C) {
if (C->getType()->isFirstClassType()) {
if (isa<PointerType>(C->getType()))
- N->addPointerTo(getNodeForConstantPointer(C));
+ Constraints.push_back(Constraint(Constraint::Copy, NodeIndex,
+ getNodeForConstantPointer(C)));
} else if (C->isNullValue()) {
- N->addPointerTo(&GraphNodes[NullObject]);
+ Constraints.push_back(Constraint(Constraint::Copy, NodeIndex,
+ NullObject));
return;
- } else {
+ } else if (!isa<UndefValue>(C)) {
// 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)));
+ AddGlobalInitializerConstraints(NodeIndex,
+ cast<Constant>(C->getOperand(i)));
}
}
+/// AddConstraintsForNonInternalLinkage - If this function does not have
+/// internal linkage, realize that we can't trust anything passed into or
+/// returned by this function.
void Andersens::AddConstraintsForNonInternalLinkage(Function *F) {
- for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
+ for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); 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]));
+ UniversalSet));
+}
+
+/// AddConstraintsForCall - If this is a call to a "known" function, add the
+/// constraints and return true. If this is a call to an unknown function,
+/// return false.
+bool Andersens::AddConstraintsForExternalCall(CallSite CS, Function *F) {
+ assert(F->isDeclaration() && "Not an external function!");
+
+ // These functions don't induce any points-to constraints.
+ if (F->getName() == "atoi" || F->getName() == "atof" ||
+ F->getName() == "atol" || F->getName() == "atoll" ||
+ F->getName() == "remove" || F->getName() == "unlink" ||
+ F->getName() == "rename" || F->getName() == "memcmp" ||
+ F->getName() == "llvm.memset.i32" ||
+ F->getName() == "llvm.memset.i64" ||
+ F->getName() == "strcmp" || F->getName() == "strncmp" ||
+ F->getName() == "execl" || F->getName() == "execlp" ||
+ F->getName() == "execle" || F->getName() == "execv" ||
+ F->getName() == "execvp" || F->getName() == "chmod" ||
+ F->getName() == "puts" || F->getName() == "write" ||
+ F->getName() == "open" || F->getName() == "create" ||
+ F->getName() == "truncate" || F->getName() == "chdir" ||
+ F->getName() == "mkdir" || F->getName() == "rmdir" ||
+ F->getName() == "read" || F->getName() == "pipe" ||
+ F->getName() == "wait" || F->getName() == "time" ||
+ F->getName() == "stat" || F->getName() == "fstat" ||
+ F->getName() == "lstat" || F->getName() == "strtod" ||
+ F->getName() == "strtof" || F->getName() == "strtold" ||
+ F->getName() == "fopen" || F->getName() == "fdopen" ||
+ F->getName() == "freopen" ||
+ F->getName() == "fflush" || F->getName() == "feof" ||
+ F->getName() == "fileno" || F->getName() == "clearerr" ||
+ F->getName() == "rewind" || F->getName() == "ftell" ||
+ F->getName() == "ferror" || F->getName() == "fgetc" ||
+ F->getName() == "fgetc" || F->getName() == "_IO_getc" ||
+ F->getName() == "fwrite" || F->getName() == "fread" ||
+ F->getName() == "fgets" || F->getName() == "ungetc" ||
+ F->getName() == "fputc" ||
+ F->getName() == "fputs" || F->getName() == "putc" ||
+ F->getName() == "ftell" || F->getName() == "rewind" ||
+ F->getName() == "_IO_putc" || F->getName() == "fseek" ||
+ F->getName() == "fgetpos" || F->getName() == "fsetpos" ||
+ F->getName() == "printf" || F->getName() == "fprintf" ||
+ F->getName() == "sprintf" || F->getName() == "vprintf" ||
+ F->getName() == "vfprintf" || F->getName() == "vsprintf" ||
+ F->getName() == "scanf" || F->getName() == "fscanf" ||
+ F->getName() == "sscanf" || F->getName() == "__assert_fail" ||
+ F->getName() == "modf")
+ return true;
+
+
+ // These functions do induce points-to edges.
+ if (F->getName() == "llvm.memcpy.i32" || F->getName() == "llvm.memcpy.i64" ||
+ F->getName() == "llvm.memmove.i32" ||F->getName() == "llvm.memmove.i64" ||
+ F->getName() == "memmove") {
+
+ // *Dest = *Src, which requires an artificial graph node to represent the
+ // constraint. It is broken up into *Dest = temp, temp = *Src
+ unsigned FirstArg = getNode(CS.getArgument(0));
+ unsigned SecondArg = getNode(CS.getArgument(1));
+ unsigned TempArg = GraphNodes.size();
+ GraphNodes.push_back(Node());
+ Constraints.push_back(Constraint(Constraint::Store,
+ FirstArg, TempArg));
+ Constraints.push_back(Constraint(Constraint::Load,
+ TempArg, SecondArg));
+ return true;
+ }
+
+ // Result = Arg0
+ if (F->getName() == "realloc" || F->getName() == "strchr" ||
+ F->getName() == "strrchr" || F->getName() == "strstr" ||
+ F->getName() == "strtok") {
+ Constraints.push_back(Constraint(Constraint::Copy,
+ getNode(CS.getInstruction()),
+ getNode(CS.getArgument(0))));
+ return true;
+ }
+
+ return false;
}
+
+/// AnalyzeUsesOfFunction - Look at all of the users of the specified function.
+/// If this is used by anything complex (i.e., the address escapes), return
+/// true.
+bool Andersens::AnalyzeUsesOfFunction(Value *V) {
+
+ if (!isa<PointerType>(V->getType())) return true;
+
+ for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
+ if (dyn_cast<LoadInst>(*UI)) {
+ return false;
+ } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
+ if (V == SI->getOperand(1)) {
+ return false;
+ } else if (SI->getOperand(1)) {
+ return true; // Storing the pointer
+ }
+ } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
+ if (AnalyzeUsesOfFunction(GEP)) return true;
+ } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) {
+ // Make sure that this is just the function being called, not that it is
+ // passing into the function.
+ for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
+ if (CI->getOperand(i) == V) return true;
+ } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) {
+ // Make sure that this is just the function being called, not that it is
+ // passing into the function.
+ for (unsigned i = 3, e = II->getNumOperands(); i != e; ++i)
+ if (II->getOperand(i) == V) return true;
+ } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
+ if (CE->getOpcode() == Instruction::GetElementPtr ||
+ CE->getOpcode() == Instruction::BitCast) {
+ if (AnalyzeUsesOfFunction(CE))
+ return true;
+ } else {
+ return true;
+ }
+ } else if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) {
+ if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
+ return true; // Allow comparison against null.
+ } else if (dyn_cast<FreeInst>(*UI)) {
+ return false;
+ } else {
+ return true;
+ }
+ return false;
+}
+
/// 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]);
+ Constraints.push_back(Constraint(Constraint::AddressOf, UniversalSet,
+ UniversalSet));
+ Constraints.push_back(Constraint(Constraint::Store, UniversalSet,
+ UniversalSet));
// Next, the null pointer points to the null object.
- GraphNodes[NullPtr].addPointerTo(&GraphNodes[NullObject]);
+ Constraints.push_back(Constraint(Constraint::AddressOf, NullPtr, NullObject));
// Next, add any constraints on global variables and their initializers.
- for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I) {
+ for (Module::global_iterator I = M.global_begin(), E = M.global_end();
+ 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);
+ unsigned ObjectIndex = getObject(I);
+ Node *Object = &GraphNodes[ObjectIndex];
Object->setValue(I);
- getNodeValue(*I)->addPointerTo(Object);
+ Constraints.push_back(Constraint(Constraint::AddressOf, getNodeValue(*I),
+ ObjectIndex));
if (I->hasInitializer()) {
- AddGlobalInitializerConstraints(Object, I->getInitializer());
+ AddGlobalInitializerConstraints(ObjectIndex, 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]));
+ Constraints.push_back(Constraint(Constraint::Copy, ObjectIndex,
+ 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));
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
// Set up the return value node.
if (isa<PointerType>(F->getFunctionType()->getReturnType()))
- getReturnNode(F)->setValue(F);
+ GraphNodes[getReturnNode(F)].setValue(F);
if (F->getFunctionType()->isVarArg())
- getVarargNode(F)->setValue(F);
+ GraphNodes[getVarargNode(F)].setValue(F);
// Set up incoming argument nodes.
- for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
+ for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
+ I != E; ++I)
if (isa<PointerType>(I->getType()))
getNodeValue(*I);
- if (!F->hasInternalLinkage())
+ // At some point we should just add constraints for the escaping functions
+ // at solve time, but this slows down solving. For now, we simply mark
+ // address taken functions as escaping and treat them as external.
+ if (!F->hasInternalLinkage() || AnalyzeUsesOfFunction(F))
AddConstraintsForNonInternalLinkage(F);
- if (!F->isExternal()) {
+ if (!F->isDeclaration()) {
// 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.
if (isa<PointerType>(F->getFunctionType()->getReturnType()))
Constraints.push_back(Constraint(Constraint::Copy,
getReturnNode(F),
- &GraphNodes[UniversalSet]));
+ 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)
+ for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
+ 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]));
+ UniversalSet));
// Memory objects passed into external function calls can have the
// universal set point to them.
+#if FULL_UNIVERSAL
Constraints.push_back(Constraint(Constraint::Copy,
- &GraphNodes[UniversalSet],
+ UniversalSet,
getNode(I)));
+#else
+ Constraints.push_back(Constraint(Constraint::Copy,
+ getNode(I),
+ UniversalSet));
+#endif
}
// 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]));
+ UniversalSet));
}
}
NumConstraints += Constraints.size();
case Instruction::Br:
case Instruction::Switch:
case Instruction::Unwind:
+ case Instruction::Unreachable:
case Instruction::Free:
- case Instruction::Shl:
- case Instruction::Shr:
+ case Instruction::ICmp:
+ case Instruction::FCmp:
return;
default:
// Is this something we aren't handling yet?
- std::cerr << "Unknown instruction: " << I;
+ cerr << "Unknown instruction: " << I;
abort();
}
}
void Andersens::visitAllocationInst(AllocationInst &AI) {
- getNodeValue(AI)->addPointerTo(getObject(&AI)->setValue(&AI));
+ unsigned ObjectIndex = getObject(&AI);
+ GraphNodes[ObjectIndex].setValue(&AI);
+ Constraints.push_back(Constraint(Constraint::AddressOf, getNodeValue(AI),
+ ObjectIndex));
}
void Andersens::visitReturnInst(ReturnInst &RI) {
void Andersens::visitPHINode(PHINode &PN) {
if (isa<PointerType>(PN.getType())) {
- Node *PNN = getNodeValue(PN);
+ unsigned 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(CI.getOperand(0))));
} else {
// P1 = cast int --> <Copy/P1/Univ>
+#if 0
Constraints.push_back(Constraint(Constraint::Copy, getNodeValue(CI),
- &GraphNodes[UniversalSet]));
+ UniversalSet));
+#else
+ getNodeValue(CI);
+#endif
}
} else if (isa<PointerType>(Op->getType())) {
// int = cast P1 --> <Copy/Univ/P1>
+#if 0
Constraints.push_back(Constraint(Constraint::Copy,
- &GraphNodes[UniversalSet],
+ UniversalSet,
getNode(CI.getOperand(0))));
+#else
+ getNode(CI.getOperand(0));
+#endif
}
}
void Andersens::visitSelectInst(SelectInst &SI) {
if (isa<PointerType>(SI.getType())) {
- Node *SIN = getNodeValue(SI);
+ unsigned 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))));
}
}
-void Andersens::visitVANext(VANextInst &I) {
- // FIXME: Implement
- assert(0 && "vanext not handled yet!");
-}
void Andersens::visitVAArg(VAArgInst &I) {
assert(0 && "vaarg not handled yet!");
}
/// the function pointer has been casted. If this is the case, do something
/// reasonable.
void Andersens::AddConstraintsForCall(CallSite CS, Function *F) {
+ Value *CallValue = CS.getCalledValue();
+ bool IsDeref = F == NULL;
+
+ // If this is a call to an external function, try to handle it directly to get
+ // some taste of context sensitivity.
+ if (F && F->isDeclaration() && AddConstraintsForExternalCall(CS, F))
+ return;
+
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)));
+ unsigned CSN = getNode(CS.getInstruction());
+ if (!F || isa<PointerType>(F->getFunctionType()->getReturnType())) {
+ if (IsDeref)
+ Constraints.push_back(Constraint(Constraint::Load, CSN,
+ getNode(CallValue), CallReturnPos));
+ else
+ Constraints.push_back(Constraint(Constraint::Copy, CSN,
+ getNode(CallValue) + CallReturnPos));
} 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]));
+ UniversalSet));
}
- } else if (isa<PointerType>(F->getFunctionType()->getReturnType())) {
+ } else if (F && isa<PointerType>(F->getFunctionType()->getReturnType())) {
+#if FULL_UNIVERSAL
Constraints.push_back(Constraint(Constraint::Copy,
- &GraphNodes[UniversalSet],
- getReturnNode(F)));
+ UniversalSet,
+ getNode(CallValue) + CallReturnPos));
+#else
+ Constraints.push_back(Constraint(Constraint::Copy,
+ getNode(CallValue) + CallReturnPos,
+ UniversalSet));
+#endif
+
+
}
-
- 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 (F) {
+ // Direct Call
+ Function::arg_iterator AI = F->arg_begin(), AE = F->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),
+ UniversalSet));
+ }
+ } else if (isa<PointerType>((*ArgI)->getType())) {
+#if FULL_UNIVERSAL
+ Constraints.push_back(Constraint(Constraint::Copy,
+ UniversalSet,
+ getNode(*ArgI)));
+#else
+ Constraints.push_back(Constraint(Constraint::Copy,
+ getNode(*ArgI),
+ UniversalSet));
+#endif
+ }
+ } else {
+ //Indirect Call
+ unsigned ArgPos = CallFirstArgPos;
+ for (; ArgI != ArgE; ++ArgI) {
if (isa<PointerType>((*ArgI)->getType())) {
// Copy the actual argument into the formal argument.
- Constraints.push_back(Constraint(Constraint::Copy, getNode(AI),
- getNode(*ArgI)));
+ Constraints.push_back(Constraint(Constraint::Store,
+ getNode(CallValue),
+ getNode(*ArgI), ArgPos++));
} else {
- Constraints.push_back(Constraint(Constraint::Copy, getNode(AI),
- &GraphNodes[UniversalSet]));
+ Constraints.push_back(Constraint(Constraint::Store,
+ getNode (CallValue),
+ UniversalSet, ArgPos++));
}
- } 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())
+ if (F && F->getFunctionType()->isVarArg())
for (; ArgI != ArgE; ++ArgI)
if (isa<PointerType>((*ArgI)->getType()))
Constraints.push_back(Constraint(Constraint::Copy, getVarargNode(F),
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);
+ AddConstraintsForCall(CS, NULL);
}
}
/// 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;
+ return PointsTo->intersects(N->PointsTo);
}
/// 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;
+bool Andersens::Node::intersectsIgnoring(Node *N, unsigned Ignoring) const {
+ // TODO: If we are only going to call this with the same value for Ignoring,
+ // we should move the special values out of the points-to bitmap.
+ bool WeHadIt = PointsTo->test(Ignoring);
+ bool NHadIt = N->PointsTo->test(Ignoring);
+ bool Result = false;
+ if (WeHadIt)
+ PointsTo->reset(Ignoring);
+ if (NHadIt)
+ N->PointsTo->reset(Ignoring);
+ Result = PointsTo->intersects(N->PointsTo);
+ if (WeHadIt)
+ PointsTo->set(Ignoring);
+ if (NHadIt)
+ N->PointsTo->set(Ignoring);
+ return Result;
+}
+
+void dumpToDOUT(SparseBitVector<> *bitmap) {
+#ifndef NDEBUG
+ dump(*bitmap, DOUT);
+#endif
+}
+
+
+/// Clump together address taken variables so that the points-to sets use up
+/// less space and can be operated on faster.
+
+void Andersens::ClumpAddressTaken() {
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa-renumber"
+ std::vector<unsigned> Translate;
+ std::vector<Node> NewGraphNodes;
+
+ Translate.resize(GraphNodes.size());
+ unsigned NewPos = 0;
+
+ for (unsigned i = 0; i < Constraints.size(); ++i) {
+ Constraint &C = Constraints[i];
+ if (C.Type == Constraint::AddressOf) {
+ GraphNodes[C.Src].AddressTaken = true;
+ }
}
- return false;
+ for (unsigned i = 0; i < NumberSpecialNodes; ++i) {
+ unsigned Pos = NewPos++;
+ Translate[i] = Pos;
+ NewGraphNodes.push_back(GraphNodes[i]);
+ DOUT << "Renumbering node " << i << " to node " << Pos << "\n";
+ }
+
+ // I believe this ends up being faster than making two vectors and splicing
+ // them.
+ for (unsigned i = NumberSpecialNodes; i < GraphNodes.size(); ++i) {
+ if (GraphNodes[i].AddressTaken) {
+ unsigned Pos = NewPos++;
+ Translate[i] = Pos;
+ NewGraphNodes.push_back(GraphNodes[i]);
+ DOUT << "Renumbering node " << i << " to node " << Pos << "\n";
+ }
+ }
+
+ for (unsigned i = NumberSpecialNodes; i < GraphNodes.size(); ++i) {
+ if (!GraphNodes[i].AddressTaken) {
+ unsigned Pos = NewPos++;
+ Translate[i] = Pos;
+ NewGraphNodes.push_back(GraphNodes[i]);
+ DOUT << "Renumbering node " << i << " to node " << Pos << "\n";
+ }
+ }
+
+ for (DenseMap<Value*, unsigned>::iterator Iter = ValueNodes.begin();
+ Iter != ValueNodes.end();
+ ++Iter)
+ Iter->second = Translate[Iter->second];
+
+ for (DenseMap<Value*, unsigned>::iterator Iter = ObjectNodes.begin();
+ Iter != ObjectNodes.end();
+ ++Iter)
+ Iter->second = Translate[Iter->second];
+
+ for (DenseMap<Function*, unsigned>::iterator Iter = ReturnNodes.begin();
+ Iter != ReturnNodes.end();
+ ++Iter)
+ Iter->second = Translate[Iter->second];
+
+ for (DenseMap<Function*, unsigned>::iterator Iter = VarargNodes.begin();
+ Iter != VarargNodes.end();
+ ++Iter)
+ Iter->second = Translate[Iter->second];
+
+ for (unsigned i = 0; i < Constraints.size(); ++i) {
+ Constraint &C = Constraints[i];
+ C.Src = Translate[C.Src];
+ C.Dest = Translate[C.Dest];
+ }
+
+ GraphNodes.swap(NewGraphNodes);
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa"
+}
+
+/// The technique used here is described in "Exploiting Pointer and Location
+/// Equivalence to Optimize Pointer Analysis. In the 14th International Static
+/// Analysis Symposium (SAS), August 2007." It is known as the "HVN" algorithm,
+/// and is equivalent to value numbering the collapsed constraint graph without
+/// evaluating unions. This is used as a pre-pass to HU in order to resolve
+/// first order pointer dereferences and speed up/reduce memory usage of HU.
+/// Running both is equivalent to HRU without the iteration
+/// HVN in more detail:
+/// Imagine the set of constraints was simply straight line code with no loops
+/// (we eliminate cycles, so there are no loops), such as:
+/// E = &D
+/// E = &C
+/// E = F
+/// F = G
+/// G = F
+/// Applying value numbering to this code tells us:
+/// G == F == E
+///
+/// For HVN, this is as far as it goes. We assign new value numbers to every
+/// "address node", and every "reference node".
+/// To get the optimal result for this, we use a DFS + SCC (since all nodes in a
+/// cycle must have the same value number since the = operation is really
+/// inclusion, not overwrite), and value number nodes we receive points-to sets
+/// before we value our own node.
+/// The advantage of HU over HVN is that HU considers the inclusion property, so
+/// that if you have
+/// E = &D
+/// E = &C
+/// E = F
+/// F = G
+/// F = &D
+/// G = F
+/// HU will determine that G == F == E. HVN will not, because it cannot prove
+/// that the points to information ends up being the same because they all
+/// receive &D from E anyway.
+
+void Andersens::HVN() {
+ DOUT << "Beginning HVN\n";
+ // Build a predecessor graph. This is like our constraint graph with the
+ // edges going in the opposite direction, and there are edges for all the
+ // constraints, instead of just copy constraints. We also build implicit
+ // edges for constraints are implied but not explicit. I.E for the constraint
+ // a = &b, we add implicit edges *a = b. This helps us capture more cycles
+ for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
+ Constraint &C = Constraints[i];
+ if (C.Type == Constraint::AddressOf) {
+ GraphNodes[C.Src].AddressTaken = true;
+ GraphNodes[C.Src].Direct = false;
+
+ // Dest = &src edge
+ unsigned AdrNode = C.Src + FirstAdrNode;
+ if (!GraphNodes[C.Dest].PredEdges)
+ GraphNodes[C.Dest].PredEdges = new SparseBitVector<>;
+ GraphNodes[C.Dest].PredEdges->set(AdrNode);
+
+ // *Dest = src edge
+ unsigned RefNode = C.Dest + FirstRefNode;
+ if (!GraphNodes[RefNode].ImplicitPredEdges)
+ GraphNodes[RefNode].ImplicitPredEdges = new SparseBitVector<>;
+ GraphNodes[RefNode].ImplicitPredEdges->set(C.Src);
+ } else if (C.Type == Constraint::Load) {
+ if (C.Offset == 0) {
+ // dest = *src edge
+ if (!GraphNodes[C.Dest].PredEdges)
+ GraphNodes[C.Dest].PredEdges = new SparseBitVector<>;
+ GraphNodes[C.Dest].PredEdges->set(C.Src + FirstRefNode);
+ } else {
+ GraphNodes[C.Dest].Direct = false;
+ }
+ } else if (C.Type == Constraint::Store) {
+ if (C.Offset == 0) {
+ // *dest = src edge
+ unsigned RefNode = C.Dest + FirstRefNode;
+ if (!GraphNodes[RefNode].PredEdges)
+ GraphNodes[RefNode].PredEdges = new SparseBitVector<>;
+ GraphNodes[RefNode].PredEdges->set(C.Src);
+ }
+ } else {
+ // Dest = Src edge and *Dest = *Src edge
+ if (!GraphNodes[C.Dest].PredEdges)
+ GraphNodes[C.Dest].PredEdges = new SparseBitVector<>;
+ GraphNodes[C.Dest].PredEdges->set(C.Src);
+ unsigned RefNode = C.Dest + FirstRefNode;
+ if (!GraphNodes[RefNode].ImplicitPredEdges)
+ GraphNodes[RefNode].ImplicitPredEdges = new SparseBitVector<>;
+ GraphNodes[RefNode].ImplicitPredEdges->set(C.Src + FirstRefNode);
+ }
+ }
+ PEClass = 1;
+ // Do SCC finding first to condense our predecessor graph
+ DFSNumber = 0;
+ Node2DFS.insert(Node2DFS.begin(), GraphNodes.size(), 0);
+ Node2Deleted.insert(Node2Deleted.begin(), GraphNodes.size(), false);
+ Node2Visited.insert(Node2Visited.begin(), GraphNodes.size(), false);
+
+ for (unsigned i = 0; i < FirstRefNode; ++i) {
+ unsigned Node = VSSCCRep[i];
+ if (!Node2Visited[Node])
+ HVNValNum(Node);
+ }
+ for (BitVectorMap::iterator Iter = Set2PEClass.begin();
+ Iter != Set2PEClass.end();
+ ++Iter)
+ delete Iter->first;
+ Set2PEClass.clear();
+ Node2DFS.clear();
+ Node2Deleted.clear();
+ Node2Visited.clear();
+ DOUT << "Finished HVN\n";
+
+}
+
+/// This is the workhorse of HVN value numbering. We combine SCC finding at the
+/// same time because it's easy.
+void Andersens::HVNValNum(unsigned NodeIndex) {
+ unsigned MyDFS = DFSNumber++;
+ Node *N = &GraphNodes[NodeIndex];
+ Node2Visited[NodeIndex] = true;
+ Node2DFS[NodeIndex] = MyDFS;
+
+ // First process all our explicit edges
+ if (N->PredEdges)
+ for (SparseBitVector<>::iterator Iter = N->PredEdges->begin();
+ Iter != N->PredEdges->end();
+ ++Iter) {
+ unsigned j = VSSCCRep[*Iter];
+ if (!Node2Deleted[j]) {
+ if (!Node2Visited[j])
+ HVNValNum(j);
+ if (Node2DFS[NodeIndex] > Node2DFS[j])
+ Node2DFS[NodeIndex] = Node2DFS[j];
+ }
+ }
+
+ // Now process all the implicit edges
+ if (N->ImplicitPredEdges)
+ for (SparseBitVector<>::iterator Iter = N->ImplicitPredEdges->begin();
+ Iter != N->ImplicitPredEdges->end();
+ ++Iter) {
+ unsigned j = VSSCCRep[*Iter];
+ if (!Node2Deleted[j]) {
+ if (!Node2Visited[j])
+ HVNValNum(j);
+ if (Node2DFS[NodeIndex] > Node2DFS[j])
+ Node2DFS[NodeIndex] = Node2DFS[j];
+ }
+ }
+
+ // See if we found any cycles
+ if (MyDFS == Node2DFS[NodeIndex]) {
+ while (!SCCStack.empty() && Node2DFS[SCCStack.top()] >= MyDFS) {
+ unsigned CycleNodeIndex = SCCStack.top();
+ Node *CycleNode = &GraphNodes[CycleNodeIndex];
+ VSSCCRep[CycleNodeIndex] = NodeIndex;
+ // Unify the nodes
+ N->Direct &= CycleNode->Direct;
+
+ if (CycleNode->PredEdges) {
+ if (!N->PredEdges)
+ N->PredEdges = new SparseBitVector<>;
+ *(N->PredEdges) |= CycleNode->PredEdges;
+ delete CycleNode->PredEdges;
+ CycleNode->PredEdges = NULL;
+ }
+ if (CycleNode->ImplicitPredEdges) {
+ if (!N->ImplicitPredEdges)
+ N->ImplicitPredEdges = new SparseBitVector<>;
+ *(N->ImplicitPredEdges) |= CycleNode->ImplicitPredEdges;
+ delete CycleNode->ImplicitPredEdges;
+ CycleNode->ImplicitPredEdges = NULL;
+ }
+
+ SCCStack.pop();
+ }
+
+ Node2Deleted[NodeIndex] = true;
+
+ if (!N->Direct) {
+ GraphNodes[NodeIndex].PointerEquivLabel = PEClass++;
+ return;
+ }
+
+ // Collect labels of successor nodes
+ bool AllSame = true;
+ unsigned First = ~0;
+ SparseBitVector<> *Labels = new SparseBitVector<>;
+ bool Used = false;
+
+ if (N->PredEdges)
+ for (SparseBitVector<>::iterator Iter = N->PredEdges->begin();
+ Iter != N->PredEdges->end();
+ ++Iter) {
+ unsigned j = VSSCCRep[*Iter];
+ unsigned Label = GraphNodes[j].PointerEquivLabel;
+ // Ignore labels that are equal to us or non-pointers
+ if (j == NodeIndex || Label == 0)
+ continue;
+ if (First == (unsigned)~0)
+ First = Label;
+ else if (First != Label)
+ AllSame = false;
+ Labels->set(Label);
+ }
+
+ // We either have a non-pointer, a copy of an existing node, or a new node.
+ // Assign the appropriate pointer equivalence label.
+ if (Labels->empty()) {
+ GraphNodes[NodeIndex].PointerEquivLabel = 0;
+ } else if (AllSame) {
+ GraphNodes[NodeIndex].PointerEquivLabel = First;
+ } else {
+ GraphNodes[NodeIndex].PointerEquivLabel = Set2PEClass[Labels];
+ if (GraphNodes[NodeIndex].PointerEquivLabel == 0) {
+ unsigned EquivClass = PEClass++;
+ Set2PEClass[Labels] = EquivClass;
+ GraphNodes[NodeIndex].PointerEquivLabel = EquivClass;
+ Used = true;
+ }
+ }
+ if (!Used)
+ delete Labels;
+ } else {
+ SCCStack.push(NodeIndex);
+ }
+}
+
+/// The technique used here is described in "Exploiting Pointer and Location
+/// Equivalence to Optimize Pointer Analysis. In the 14th International Static
+/// Analysis Symposium (SAS), August 2007." It is known as the "HU" algorithm,
+/// and is equivalent to value numbering the collapsed constraint graph
+/// including evaluating unions.
+void Andersens::HU() {
+ DOUT << "Beginning HU\n";
+ // Build a predecessor graph. This is like our constraint graph with the
+ // edges going in the opposite direction, and there are edges for all the
+ // constraints, instead of just copy constraints. We also build implicit
+ // edges for constraints are implied but not explicit. I.E for the constraint
+ // a = &b, we add implicit edges *a = b. This helps us capture more cycles
+ for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
+ Constraint &C = Constraints[i];
+ if (C.Type == Constraint::AddressOf) {
+ GraphNodes[C.Src].AddressTaken = true;
+ GraphNodes[C.Src].Direct = false;
+
+ GraphNodes[C.Dest].PointsTo->set(C.Src);
+ // *Dest = src edge
+ unsigned RefNode = C.Dest + FirstRefNode;
+ if (!GraphNodes[RefNode].ImplicitPredEdges)
+ GraphNodes[RefNode].ImplicitPredEdges = new SparseBitVector<>;
+ GraphNodes[RefNode].ImplicitPredEdges->set(C.Src);
+ GraphNodes[C.Src].PointedToBy->set(C.Dest);
+ } else if (C.Type == Constraint::Load) {
+ if (C.Offset == 0) {
+ // dest = *src edge
+ if (!GraphNodes[C.Dest].PredEdges)
+ GraphNodes[C.Dest].PredEdges = new SparseBitVector<>;
+ GraphNodes[C.Dest].PredEdges->set(C.Src + FirstRefNode);
+ } else {
+ GraphNodes[C.Dest].Direct = false;
+ }
+ } else if (C.Type == Constraint::Store) {
+ if (C.Offset == 0) {
+ // *dest = src edge
+ unsigned RefNode = C.Dest + FirstRefNode;
+ if (!GraphNodes[RefNode].PredEdges)
+ GraphNodes[RefNode].PredEdges = new SparseBitVector<>;
+ GraphNodes[RefNode].PredEdges->set(C.Src);
+ }
+ } else {
+ // Dest = Src edge and *Dest = *Src edg
+ if (!GraphNodes[C.Dest].PredEdges)
+ GraphNodes[C.Dest].PredEdges = new SparseBitVector<>;
+ GraphNodes[C.Dest].PredEdges->set(C.Src);
+ unsigned RefNode = C.Dest + FirstRefNode;
+ if (!GraphNodes[RefNode].ImplicitPredEdges)
+ GraphNodes[RefNode].ImplicitPredEdges = new SparseBitVector<>;
+ GraphNodes[RefNode].ImplicitPredEdges->set(C.Src + FirstRefNode);
+ }
+ }
+ PEClass = 1;
+ // Do SCC finding first to condense our predecessor graph
+ DFSNumber = 0;
+ Node2DFS.insert(Node2DFS.begin(), GraphNodes.size(), 0);
+ Node2Deleted.insert(Node2Deleted.begin(), GraphNodes.size(), false);
+ Node2Visited.insert(Node2Visited.begin(), GraphNodes.size(), false);
+
+ for (unsigned i = 0; i < FirstRefNode; ++i) {
+ if (FindNode(i) == i) {
+ unsigned Node = VSSCCRep[i];
+ if (!Node2Visited[Node])
+ Condense(Node);
+ }
+ }
+
+ // Reset tables for actual labeling
+ Node2DFS.clear();
+ Node2Visited.clear();
+ Node2Deleted.clear();
+ // Pre-grow our densemap so that we don't get really bad behavior
+ Set2PEClass.resize(GraphNodes.size());
+
+ // Visit the condensed graph and generate pointer equivalence labels.
+ Node2Visited.insert(Node2Visited.begin(), GraphNodes.size(), false);
+ for (unsigned i = 0; i < FirstRefNode; ++i) {
+ if (FindNode(i) == i) {
+ unsigned Node = VSSCCRep[i];
+ if (!Node2Visited[Node])
+ HUValNum(Node);
+ }
+ }
+ // PEClass nodes will be deleted by the deleting of N->PointsTo in our caller.
+ Set2PEClass.clear();
+ DOUT << "Finished HU\n";
+}
+
+
+/// Implementation of standard Tarjan SCC algorithm as modified by Nuutilla.
+void Andersens::Condense(unsigned NodeIndex) {
+ unsigned MyDFS = DFSNumber++;
+ Node *N = &GraphNodes[NodeIndex];
+ Node2Visited[NodeIndex] = true;
+ Node2DFS[NodeIndex] = MyDFS;
+
+ // First process all our explicit edges
+ if (N->PredEdges)
+ for (SparseBitVector<>::iterator Iter = N->PredEdges->begin();
+ Iter != N->PredEdges->end();
+ ++Iter) {
+ unsigned j = VSSCCRep[*Iter];
+ if (!Node2Deleted[j]) {
+ if (!Node2Visited[j])
+ Condense(j);
+ if (Node2DFS[NodeIndex] > Node2DFS[j])
+ Node2DFS[NodeIndex] = Node2DFS[j];
+ }
+ }
+
+ // Now process all the implicit edges
+ if (N->ImplicitPredEdges)
+ for (SparseBitVector<>::iterator Iter = N->ImplicitPredEdges->begin();
+ Iter != N->ImplicitPredEdges->end();
+ ++Iter) {
+ unsigned j = VSSCCRep[*Iter];
+ if (!Node2Deleted[j]) {
+ if (!Node2Visited[j])
+ Condense(j);
+ if (Node2DFS[NodeIndex] > Node2DFS[j])
+ Node2DFS[NodeIndex] = Node2DFS[j];
+ }
+ }
+
+ // See if we found any cycles
+ if (MyDFS == Node2DFS[NodeIndex]) {
+ while (!SCCStack.empty() && Node2DFS[SCCStack.top()] >= MyDFS) {
+ unsigned CycleNodeIndex = SCCStack.top();
+ Node *CycleNode = &GraphNodes[CycleNodeIndex];
+ VSSCCRep[CycleNodeIndex] = NodeIndex;
+ // Unify the nodes
+ N->Direct &= CycleNode->Direct;
+
+ *(N->PointsTo) |= CycleNode->PointsTo;
+ delete CycleNode->PointsTo;
+ CycleNode->PointsTo = NULL;
+ if (CycleNode->PredEdges) {
+ if (!N->PredEdges)
+ N->PredEdges = new SparseBitVector<>;
+ *(N->PredEdges) |= CycleNode->PredEdges;
+ delete CycleNode->PredEdges;
+ CycleNode->PredEdges = NULL;
+ }
+ if (CycleNode->ImplicitPredEdges) {
+ if (!N->ImplicitPredEdges)
+ N->ImplicitPredEdges = new SparseBitVector<>;
+ *(N->ImplicitPredEdges) |= CycleNode->ImplicitPredEdges;
+ delete CycleNode->ImplicitPredEdges;
+ CycleNode->ImplicitPredEdges = NULL;
+ }
+ SCCStack.pop();
+ }
+
+ Node2Deleted[NodeIndex] = true;
+
+ // Set up number of incoming edges for other nodes
+ if (N->PredEdges)
+ for (SparseBitVector<>::iterator Iter = N->PredEdges->begin();
+ Iter != N->PredEdges->end();
+ ++Iter)
+ ++GraphNodes[VSSCCRep[*Iter]].NumInEdges;
+ } else {
+ SCCStack.push(NodeIndex);
+ }
+}
+
+void Andersens::HUValNum(unsigned NodeIndex) {
+ Node *N = &GraphNodes[NodeIndex];
+ Node2Visited[NodeIndex] = true;
+
+ // Eliminate dereferences of non-pointers for those non-pointers we have
+ // already identified. These are ref nodes whose non-ref node:
+ // 1. Has already been visited determined to point to nothing (and thus, a
+ // dereference of it must point to nothing)
+ // 2. Any direct node with no predecessor edges in our graph and with no
+ // points-to set (since it can't point to anything either, being that it
+ // receives no points-to sets and has none).
+ if (NodeIndex >= FirstRefNode) {
+ unsigned j = VSSCCRep[FindNode(NodeIndex - FirstRefNode)];
+ if ((Node2Visited[j] && !GraphNodes[j].PointerEquivLabel)
+ || (GraphNodes[j].Direct && !GraphNodes[j].PredEdges
+ && GraphNodes[j].PointsTo->empty())){
+ return;
+ }
+ }
+ // Process all our explicit edges
+ if (N->PredEdges)
+ for (SparseBitVector<>::iterator Iter = N->PredEdges->begin();
+ Iter != N->PredEdges->end();
+ ++Iter) {
+ unsigned j = VSSCCRep[*Iter];
+ if (!Node2Visited[j])
+ HUValNum(j);
+
+ // If this edge turned out to be the same as us, or got no pointer
+ // equivalence label (and thus points to nothing) , just decrement our
+ // incoming edges and continue.
+ if (j == NodeIndex || GraphNodes[j].PointerEquivLabel == 0) {
+ --GraphNodes[j].NumInEdges;
+ continue;
+ }
+
+ *(N->PointsTo) |= GraphNodes[j].PointsTo;
+
+ // If we didn't end up storing this in the hash, and we're done with all
+ // the edges, we don't need the points-to set anymore.
+ --GraphNodes[j].NumInEdges;
+ if (!GraphNodes[j].NumInEdges && !GraphNodes[j].StoredInHash) {
+ delete GraphNodes[j].PointsTo;
+ GraphNodes[j].PointsTo = NULL;
+ }
+ }
+ // If this isn't a direct node, generate a fresh variable.
+ if (!N->Direct) {
+ N->PointsTo->set(FirstRefNode + NodeIndex);
+ }
+
+ // See If we have something equivalent to us, if not, generate a new
+ // equivalence class.
+ if (N->PointsTo->empty()) {
+ delete N->PointsTo;
+ N->PointsTo = NULL;
+ } else {
+ if (N->Direct) {
+ N->PointerEquivLabel = Set2PEClass[N->PointsTo];
+ if (N->PointerEquivLabel == 0) {
+ unsigned EquivClass = PEClass++;
+ N->StoredInHash = true;
+ Set2PEClass[N->PointsTo] = EquivClass;
+ N->PointerEquivLabel = EquivClass;
+ }
+ } else {
+ N->PointerEquivLabel = PEClass++;
+ }
+ }
+}
+
+/// Rewrite our list of constraints so that pointer equivalent nodes are
+/// replaced by their the pointer equivalence class representative.
+void Andersens::RewriteConstraints() {
+ std::vector<Constraint> NewConstraints;
+ DenseSet<Constraint, ConstraintKeyInfo> Seen;
+
+ PEClass2Node.clear();
+ PENLEClass2Node.clear();
+
+ // We may have from 1 to Graphnodes + 1 equivalence classes.
+ PEClass2Node.insert(PEClass2Node.begin(), GraphNodes.size() + 1, -1);
+ PENLEClass2Node.insert(PENLEClass2Node.begin(), GraphNodes.size() + 1, -1);
+
+ // Rewrite constraints, ignoring non-pointer constraints, uniting equivalent
+ // nodes, and rewriting constraints to use the representative nodes.
+ for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
+ Constraint &C = Constraints[i];
+ unsigned RHSNode = FindNode(C.Src);
+ unsigned LHSNode = FindNode(C.Dest);
+ unsigned RHSLabel = GraphNodes[VSSCCRep[RHSNode]].PointerEquivLabel;
+ unsigned LHSLabel = GraphNodes[VSSCCRep[LHSNode]].PointerEquivLabel;
+
+ // First we try to eliminate constraints for things we can prove don't point
+ // to anything.
+ if (LHSLabel == 0) {
+ DEBUG(PrintNode(&GraphNodes[LHSNode]));
+ DOUT << " is a non-pointer, ignoring constraint.\n";
+ continue;
+ }
+ if (RHSLabel == 0) {
+ DEBUG(PrintNode(&GraphNodes[RHSNode]));
+ DOUT << " is a non-pointer, ignoring constraint.\n";
+ continue;
+ }
+ // This constraint may be useless, and it may become useless as we translate
+ // it.
+ if (C.Src == C.Dest && C.Type == Constraint::Copy)
+ continue;
+
+ C.Src = FindEquivalentNode(RHSNode, RHSLabel);
+ C.Dest = FindEquivalentNode(FindNode(LHSNode), LHSLabel);
+ if (C.Src == C.Dest && C.Type == Constraint::Copy
+ || Seen.count(C))
+ continue;
+
+ Seen.insert(C);
+ NewConstraints.push_back(C);
+ }
+ Constraints.swap(NewConstraints);
+ PEClass2Node.clear();
+}
+
+/// See if we have a node that is pointer equivalent to the one being asked
+/// about, and if so, unite them and return the equivalent node. Otherwise,
+/// return the original node.
+unsigned Andersens::FindEquivalentNode(unsigned NodeIndex,
+ unsigned NodeLabel) {
+ if (!GraphNodes[NodeIndex].AddressTaken) {
+ if (PEClass2Node[NodeLabel] != -1) {
+ // We found an existing node with the same pointer label, so unify them.
+ // We specifically request that Union-By-Rank not be used so that
+ // PEClass2Node[NodeLabel] U= NodeIndex and not the other way around.
+ return UniteNodes(PEClass2Node[NodeLabel], NodeIndex, false);
+ } else {
+ PEClass2Node[NodeLabel] = NodeIndex;
+ PENLEClass2Node[NodeLabel] = NodeIndex;
+ }
+ } else if (PENLEClass2Node[NodeLabel] == -1) {
+ PENLEClass2Node[NodeLabel] = NodeIndex;
+ }
+
+ return NodeIndex;
}
-// 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;
+void Andersens::PrintLabels() {
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ if (i < FirstRefNode) {
+ PrintNode(&GraphNodes[i]);
+ } else if (i < FirstAdrNode) {
+ DOUT << "REF(";
+ PrintNode(&GraphNodes[i-FirstRefNode]);
+ DOUT <<")";
} else {
- // We found a new element to copy over.
- Changed = true;
- Pointees.insert(Pointees.begin()+i, *I);
- ++i; ++I;
+ DOUT << "ADR(";
+ PrintNode(&GraphNodes[i-FirstAdrNode]);
+ DOUT <<")";
+ }
+
+ DOUT << " has pointer label " << GraphNodes[i].PointerEquivLabel
+ << " and SCC rep " << VSSCCRep[i]
+ << " and is " << (GraphNodes[i].Direct ? "Direct" : "Not direct")
+ << "\n";
+ }
+}
+
+/// Optimize the constraints by performing offline variable substitution and
+/// other optimizations.
+void Andersens::OptimizeConstraints() {
+ DOUT << "Beginning constraint optimization\n";
+
+ // Function related nodes need to stay in the same relative position and can't
+ // be location equivalent.
+ for (std::map<unsigned, unsigned>::iterator Iter = MaxK.begin();
+ Iter != MaxK.end();
+ ++Iter) {
+ for (unsigned i = Iter->first;
+ i != Iter->first + Iter->second;
+ ++i) {
+ GraphNodes[i].AddressTaken = true;
+ GraphNodes[i].Direct = false;
}
}
- if (I != E) {
- Pointees.insert(Pointees.end(), I, E);
- Changed = true;
+ ClumpAddressTaken();
+ FirstRefNode = GraphNodes.size();
+ FirstAdrNode = FirstRefNode + GraphNodes.size();
+ GraphNodes.insert(GraphNodes.end(), 2 * GraphNodes.size(),
+ Node(false));
+ VSSCCRep.resize(GraphNodes.size());
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ VSSCCRep[i] = i;
+ }
+ HVN();
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ Node *N = &GraphNodes[i];
+ delete N->PredEdges;
+ N->PredEdges = NULL;
+ delete N->ImplicitPredEdges;
+ N->ImplicitPredEdges = NULL;
}
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa-labels"
+ DEBUG(PrintLabels());
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa"
+ RewriteConstraints();
+ // Delete the adr nodes.
+ GraphNodes.resize(FirstRefNode * 2);
- return Changed;
+ // Now perform HU
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ Node *N = &GraphNodes[i];
+ if (FindNode(i) == i) {
+ N->PointsTo = new SparseBitVector<>;
+ N->PointedToBy = new SparseBitVector<>;
+ // Reset our labels
+ }
+ VSSCCRep[i] = i;
+ N->PointerEquivLabel = 0;
+ }
+ HU();
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa-labels"
+ DEBUG(PrintLabels());
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa"
+ RewriteConstraints();
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ if (FindNode(i) == i) {
+ Node *N = &GraphNodes[i];
+ delete N->PointsTo;
+ delete N->PredEdges;
+ delete N->ImplicitPredEdges;
+ delete N->PointedToBy;
+ }
+ }
+ GraphNodes.erase(GraphNodes.begin() + FirstRefNode, GraphNodes.end());
+ DOUT << "Finished constraint optimization\n";
+ FirstRefNode = 0;
+ FirstAdrNode = 0;
}
-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;
+/// Unite pointer but not location equivalent variables, now that the constraint
+/// graph is built.
+void Andersens::UnitePointerEquivalences() {
+ DOUT << "Uniting remaining pointer equivalences\n";
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ if (GraphNodes[i].AddressTaken && GraphNodes[i].isRep()) {
+ unsigned Label = GraphNodes[i].PointerEquivLabel;
+
+ if (Label && PENLEClass2Node[Label] != -1)
+ UniteNodes(i, PENLEClass2Node[Label]);
+ }
+ }
+ DOUT << "Finished remaining pointer equivalences\n";
+ PENLEClass2Node.clear();
}
-bool Andersens::Node::storeThrough(Node *N) {
- bool Changed = false;
- for (iterator I = begin(), E = end(); I != E; ++I)
- Changed |= (*I)->copyFrom(N);
- return Changed;
+/// Create the constraint graph used for solving points-to analysis.
+///
+void Andersens::CreateConstraintGraph() {
+ for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
+ Constraint &C = Constraints[i];
+ assert (C.Src < GraphNodes.size() && C.Dest < GraphNodes.size());
+ if (C.Type == Constraint::AddressOf)
+ GraphNodes[C.Dest].PointsTo->set(C.Src);
+ else if (C.Type == Constraint::Load)
+ GraphNodes[C.Src].Constraints.push_back(C);
+ else if (C.Type == Constraint::Store)
+ GraphNodes[C.Dest].Constraints.push_back(C);
+ else if (C.Offset != 0)
+ GraphNodes[C.Src].Constraints.push_back(C);
+ else
+ GraphNodes[C.Src].Edges->set(C.Dest);
+ }
}
+// Perform DFS and cycle detection.
+bool Andersens::QueryNode(unsigned Node) {
+ assert(GraphNodes[Node].isRep() && "Querying a non-rep node");
+ unsigned OurDFS = ++DFSNumber;
+ SparseBitVector<> ToErase;
+ SparseBitVector<> NewEdges;
+ Tarjan2DFS[Node] = OurDFS;
+
+ // Changed denotes a change from a recursive call that we will bubble up.
+ // Merged is set if we actually merge a node ourselves.
+ bool Changed = false, Merged = false;
+
+ for (SparseBitVector<>::iterator bi = GraphNodes[Node].Edges->begin();
+ bi != GraphNodes[Node].Edges->end();
+ ++bi) {
+ unsigned RepNode = FindNode(*bi);
+ // If this edge points to a non-representative node but we are
+ // already planning to add an edge to its representative, we have no
+ // need for this edge anymore.
+ if (RepNode != *bi && NewEdges.test(RepNode)){
+ ToErase.set(*bi);
+ continue;
+ }
+
+ // Continue about our DFS.
+ if (!Tarjan2Deleted[RepNode]){
+ if (Tarjan2DFS[RepNode] == 0) {
+ Changed |= QueryNode(RepNode);
+ // May have been changed by QueryNode
+ RepNode = FindNode(RepNode);
+ }
+ if (Tarjan2DFS[RepNode] < Tarjan2DFS[Node])
+ Tarjan2DFS[Node] = Tarjan2DFS[RepNode];
+ }
+
+ // We may have just discovered that this node is part of a cycle, in
+ // which case we can also erase it.
+ if (RepNode != *bi) {
+ ToErase.set(*bi);
+ NewEdges.set(RepNode);
+ }
+ }
+
+ GraphNodes[Node].Edges->intersectWithComplement(ToErase);
+ GraphNodes[Node].Edges |= NewEdges;
+
+ // If this node is a root of a non-trivial SCC, place it on our
+ // worklist to be processed.
+ if (OurDFS == Tarjan2DFS[Node]) {
+ while (!SCCStack.empty() && Tarjan2DFS[SCCStack.top()] >= OurDFS) {
+ Node = UniteNodes(Node, SCCStack.top());
+
+ SCCStack.pop();
+ Merged = true;
+ }
+ Tarjan2Deleted[Node] = true;
+
+ if (Merged)
+ NextWL->insert(&GraphNodes[Node]);
+ } else {
+ SCCStack.push(Node);
+ }
+
+ return(Changed | Merged);
+}
/// 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.
///
+/// We use a variant of the technique called "Lazy Cycle Detection", which is
+/// described in "The Ant and the Grasshopper: Fast and Accurate Pointer
+/// Analysis for Millions of Lines of Code. In Programming Language Design and
+/// Implementation (PLDI), June 2007."
+/// The paper describes performing cycle detection one node at a time, which can
+/// be expensive if there are no cycles, but there are long chains of nodes that
+/// it heuristically believes are cycles (because it will DFS from each node
+/// without state from previous nodes).
+/// Instead, we use the heuristic to build a worklist of nodes to check, then
+/// cycle detect them all at the same time to do this more cheaply. This
+/// catches cycles slightly later than the original technique did, but does it
+/// make significantly cheaper.
+
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!");
+ CurrWL = &w1;
+ NextWL = &w2;
+
+ OptimizeConstraints();
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa-constraints"
+ DEBUG(PrintConstraints());
+#undef DEBUG_TYPE
+#define DEBUG_TYPE "anders-aa"
+
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ Node *N = &GraphNodes[i];
+ N->PointsTo = new SparseBitVector<>;
+ N->OldPointsTo = new SparseBitVector<>;
+ N->Edges = new SparseBitVector<>;
+ }
+ CreateConstraintGraph();
+ UnitePointerEquivalences();
+ assert(SCCStack.empty() && "SCC Stack should be empty by now!");
+ Node2DFS.clear();
+ Node2Deleted.clear();
+ Node2DFS.insert(Node2DFS.begin(), GraphNodes.size(), 0);
+ Node2Deleted.insert(Node2Deleted.begin(), GraphNodes.size(), false);
+ DFSNumber = 0;
+ DenseSet<Constraint, ConstraintKeyInfo> Seen;
+ DenseSet<std::pair<unsigned,unsigned>, PairKeyInfo> EdgesChecked;
+
+ // Order graph and add initial nodes to work list.
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ Node *INode = &GraphNodes[i];
+
+ // Add to work list if it's a representative and can contribute to the
+ // calculation right now.
+ if (INode->isRep() && !INode->PointsTo->empty()
+ && (!INode->Edges->empty() || !INode->Constraints.empty())) {
+ INode->Stamp();
+ CurrWL->insert(INode);
+ }
+ }
+ std::queue<unsigned int> TarjanWL;
+ while( !CurrWL->empty() ) {
+ DOUT << "Starting iteration #" << ++NumIters << "\n";
+
+ Node* CurrNode;
+ unsigned CurrNodeIndex;
+
+ // Actual cycle checking code. We cycle check all of the lazy cycle
+ // candidates from the last iteration in one go.
+ if (!TarjanWL.empty()) {
+ DFSNumber = 0;
+
+ Tarjan2DFS.clear();
+ Tarjan2Deleted.clear();
+ while (!TarjanWL.empty()) {
+ unsigned int ToTarjan = TarjanWL.front();
+ TarjanWL.pop();
+ if (!Tarjan2Deleted[ToTarjan]
+ && GraphNodes[ToTarjan].isRep()
+ && Tarjan2DFS[ToTarjan] == 0)
+ QueryNode(ToTarjan);
}
}
+
+ // Add to work list if it's a representative and can contribute to the
+ // calculation right now.
+ while( (CurrNode = CurrWL->pop()) != NULL ) {
+ CurrNodeIndex = CurrNode - &GraphNodes[0];
+ CurrNode->Stamp();
+
+
+ // Figure out the changed points to bits
+ SparseBitVector<> CurrPointsTo;
+ CurrPointsTo.intersectWithComplement(CurrNode->PointsTo,
+ CurrNode->OldPointsTo);
+ if (CurrPointsTo.empty())
+ continue;
+
+ *(CurrNode->OldPointsTo) |= CurrPointsTo;
+ Seen.clear();
+
+ /* Now process the constraints for this node. */
+ for (std::list<Constraint>::iterator li = CurrNode->Constraints.begin();
+ li != CurrNode->Constraints.end(); ) {
+ li->Src = FindNode(li->Src);
+ li->Dest = FindNode(li->Dest);
+
+ // Delete redundant constraints
+ if( Seen.count(*li) ) {
+ std::list<Constraint>::iterator lk = li; li++;
+
+ CurrNode->Constraints.erase(lk);
+ ++NumErased;
+ continue;
+ }
+ Seen.insert(*li);
+
+ // Src and Dest will be the vars we are going to process.
+ // This may look a bit ugly, but what it does is allow us to process
+ // both store and load constraints with the same code.
+ // Load constraints say that every member of our RHS solution has K
+ // added to it, and that variable gets an edge to LHS. We also union
+ // RHS+K's solution into the LHS solution.
+ // Store constraints say that every member of our LHS solution has K
+ // added to it, and that variable gets an edge from RHS. We also union
+ // RHS's solution into the LHS+K solution.
+ unsigned *Src;
+ unsigned *Dest;
+ unsigned K = li->Offset;
+ unsigned CurrMember;
+ if (li->Type == Constraint::Load) {
+ Src = &CurrMember;
+ Dest = &li->Dest;
+ } else if (li->Type == Constraint::Store) {
+ Src = &li->Src;
+ Dest = &CurrMember;
+ } else {
+ // TODO Handle offseted copy constraint
+ li++;
+ continue;
+ }
+ // TODO: hybrid cycle detection would go here, we should check
+ // if it was a statically detected offline equivalence that
+ // involves pointers , and if so, remove the redundant constraints.
+
+ const SparseBitVector<> &Solution = CurrPointsTo;
+
+ for (SparseBitVector<>::iterator bi = Solution.begin();
+ bi != Solution.end();
+ ++bi) {
+ CurrMember = *bi;
+
+ // Need to increment the member by K since that is where we are
+ // supposed to copy to/from. Note that in positive weight cycles,
+ // which occur in address taking of fields, K can go past
+ // MaxK[CurrMember] elements, even though that is all it could point
+ // to.
+ if (K > 0 && K > MaxK[CurrMember])
+ continue;
+ else
+ CurrMember = FindNode(CurrMember + K);
+
+ // Add an edge to the graph, so we can just do regular bitmap ior next
+ // time. It may also let us notice a cycle.
+#if !FULL_UNIVERSAL
+ if (*Dest < NumberSpecialNodes)
+ continue;
+#endif
+ if (GraphNodes[*Src].Edges->test_and_set(*Dest))
+ if (GraphNodes[*Dest].PointsTo |= *(GraphNodes[*Src].PointsTo))
+ NextWL->insert(&GraphNodes[*Dest]);
- 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);
- }
- }
+ }
+ li++;
+ }
+ SparseBitVector<> NewEdges;
+ SparseBitVector<> ToErase;
+
+ // Now all we have left to do is propagate points-to info along the
+ // edges, erasing the redundant edges.
+ for (SparseBitVector<>::iterator bi = CurrNode->Edges->begin();
+ bi != CurrNode->Edges->end();
+ ++bi) {
+
+ unsigned DestVar = *bi;
+ unsigned Rep = FindNode(DestVar);
+
+ // If we ended up with this node as our destination, or we've already
+ // got an edge for the representative, delete the current edge.
+ if (Rep == CurrNodeIndex ||
+ (Rep != DestVar && NewEdges.test(Rep))) {
+ ToErase.set(DestVar);
+ continue;
+ }
+
+ std::pair<unsigned,unsigned> edge(CurrNodeIndex,Rep);
+
+ // This is where we do lazy cycle detection.
+ // If this is a cycle candidate (equal points-to sets and this
+ // particular edge has not been cycle-checked previously), add to the
+ // list to check for cycles on the next iteration.
+ if (!EdgesChecked.count(edge) &&
+ *(GraphNodes[Rep].PointsTo) == *(CurrNode->PointsTo)) {
+ EdgesChecked.insert(edge);
+ TarjanWL.push(Rep);
+ }
+ // Union the points-to sets into the dest
+#if !FULL_UNIVERSAL
+ if (Rep >= NumberSpecialNodes)
+#endif
+ if (GraphNodes[Rep].PointsTo |= CurrPointsTo) {
+ NextWL->insert(&GraphNodes[Rep]);
+ }
+ // If this edge's destination was collapsed, rewrite the edge.
+ if (Rep != DestVar) {
+ ToErase.set(DestVar);
+ NewEdges.set(Rep);
+ }
}
+ CurrNode->Edges->intersectWithComplement(ToErase);
+ CurrNode->Edges |= NewEdges;
}
+
+ // Switch to other work list.
+ WorkList* t = CurrWL; CurrWL = NextWL; NextWL = t;
+ }
+
+
+ Node2DFS.clear();
+ Node2Deleted.clear();
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ Node *N = &GraphNodes[i];
+ delete N->OldPointsTo;
+ delete N->Edges;
}
}
+//===----------------------------------------------------------------------===//
+// Union-Find
+//===----------------------------------------------------------------------===//
+
+// Unite nodes First and Second, returning the one which is now the
+// representative node. First and Second are indexes into GraphNodes
+unsigned Andersens::UniteNodes(unsigned First, unsigned Second,
+ bool UnionByRank) {
+ assert (First < GraphNodes.size() && Second < GraphNodes.size() &&
+ "Attempting to merge nodes that don't exist");
+
+ Node *FirstNode = &GraphNodes[First];
+ Node *SecondNode = &GraphNodes[Second];
+
+ assert (SecondNode->isRep() && FirstNode->isRep() &&
+ "Trying to unite two non-representative nodes!");
+ if (First == Second)
+ return First;
+
+ if (UnionByRank) {
+ int RankFirst = (int) FirstNode ->NodeRep;
+ int RankSecond = (int) SecondNode->NodeRep;
+
+ // Rank starts at -1 and gets decremented as it increases.
+ // Translation: higher rank, lower NodeRep value, which is always negative.
+ if (RankFirst > RankSecond) {
+ unsigned t = First; First = Second; Second = t;
+ Node* tp = FirstNode; FirstNode = SecondNode; SecondNode = tp;
+ } else if (RankFirst == RankSecond) {
+ FirstNode->NodeRep = (unsigned) (RankFirst - 1);
+ }
+ }
+
+ SecondNode->NodeRep = First;
+#if !FULL_UNIVERSAL
+ if (First >= NumberSpecialNodes)
+#endif
+ if (FirstNode->PointsTo && SecondNode->PointsTo)
+ FirstNode->PointsTo |= *(SecondNode->PointsTo);
+ if (FirstNode->Edges && SecondNode->Edges)
+ FirstNode->Edges |= *(SecondNode->Edges);
+ if (!SecondNode->Constraints.empty())
+ FirstNode->Constraints.splice(FirstNode->Constraints.begin(),
+ SecondNode->Constraints);
+ if (FirstNode->OldPointsTo) {
+ delete FirstNode->OldPointsTo;
+ FirstNode->OldPointsTo = new SparseBitVector<>;
+ }
+
+ // Destroy interesting parts of the merged-from node.
+ delete SecondNode->OldPointsTo;
+ delete SecondNode->Edges;
+ delete SecondNode->PointsTo;
+ SecondNode->Edges = NULL;
+ SecondNode->PointsTo = NULL;
+ SecondNode->OldPointsTo = NULL;
+
+ NumUnified++;
+ DOUT << "Unified Node ";
+ DEBUG(PrintNode(FirstNode));
+ DOUT << " and Node ";
+ DEBUG(PrintNode(SecondNode));
+ DOUT << "\n";
+
+ // TODO: Handle SDT
+ return First;
+}
+// Find the index into GraphNodes of the node representing Node, performing
+// path compression along the way
+unsigned Andersens::FindNode(unsigned NodeIndex) {
+ assert (NodeIndex < GraphNodes.size()
+ && "Attempting to find a node that can't exist");
+ Node *N = &GraphNodes[NodeIndex];
+ if (N->isRep())
+ return NodeIndex;
+ else
+ return (N->NodeRep = FindNode(N->NodeRep));
+}
//===----------------------------------------------------------------------===//
// Debugging Output
void Andersens::PrintNode(Node *N) {
if (N == &GraphNodes[UniversalSet]) {
- std::cerr << "<universal>";
+ cerr << "<universal>";
return;
} else if (N == &GraphNodes[NullPtr]) {
- std::cerr << "<nullptr>";
+ cerr << "<nullptr>";
return;
} else if (N == &GraphNodes[NullObject]) {
- std::cerr << "<null>";
+ cerr << "<null>";
+ return;
+ }
+ if (!N->getValue()) {
+ cerr << "artificial" << (intptr_t) N;
return;
}
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";
+ N == &GraphNodes[getReturnNode(F)]) {
+ cerr << F->getName() << ":retval";
return;
- } else if (F->getFunctionType()->isVarArg() && N == getVarargNode(F)) {
- std::cerr << F->getName() << ":vararg";
+ } else if (F->getFunctionType()->isVarArg() &&
+ N == &GraphNodes[getVarargNode(F)]) {
+ cerr << F->getName() << ":vararg";
return;
}
}
if (Instruction *I = dyn_cast<Instruction>(V))
- std::cerr << I->getParent()->getParent()->getName() << ":";
+ cerr << I->getParent()->getParent()->getName() << ":";
else if (Argument *Arg = dyn_cast<Argument>(V))
- std::cerr << Arg->getParent()->getName() << ":";
+ cerr << Arg->getParent()->getName() << ":";
if (V->hasName())
- std::cerr << V->getName();
+ cerr << V->getName();
else
- std::cerr << "(unnamed)";
+ cerr << "(unnamed)";
if (isa<GlobalValue>(V) || isa<AllocationInst>(V))
- if (N == getObject(V))
- std::cerr << "<mem>";
+ if (N == &GraphNodes[getObject(V)])
+ cerr << "<mem>";
+}
+void Andersens::PrintConstraint(const Constraint &C) {
+ if (C.Type == Constraint::Store) {
+ cerr << "*";
+ if (C.Offset != 0)
+ cerr << "(";
+ }
+ PrintNode(&GraphNodes[C.Dest]);
+ if (C.Type == Constraint::Store && C.Offset != 0)
+ cerr << " + " << C.Offset << ")";
+ cerr << " = ";
+ if (C.Type == Constraint::Load) {
+ cerr << "*";
+ if (C.Offset != 0)
+ cerr << "(";
+ }
+ else if (C.Type == Constraint::AddressOf)
+ cerr << "&";
+ PrintNode(&GraphNodes[C.Src]);
+ if (C.Offset != 0 && C.Type != Constraint::Store)
+ cerr << " + " << C.Offset;
+ if (C.Type == Constraint::Load && C.Offset != 0)
+ cerr << ")";
+ cerr << "\n";
}
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";
- }
+ cerr << "Constraints:\n";
+
+ for (unsigned i = 0, e = Constraints.size(); i != e; ++i)
+ PrintConstraint(Constraints[i]);
}
void Andersens::PrintPointsToGraph() {
- std::cerr << "Points-to graph:\n";
+ 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);
+ if (FindNode (i) != i) {
+ PrintNode(N);
+ cerr << "\t--> same as ";
+ PrintNode(&GraphNodes[FindNode(i)]);
+ cerr << "\n";
+ } else {
+ cerr << "[" << (N->PointsTo->count()) << "] ";
+ PrintNode(N);
+ cerr << "\t--> ";
+
+ bool first = true;
+ for (SparseBitVector<>::iterator bi = N->PointsTo->begin();
+ bi != N->PointsTo->end();
+ ++bi) {
+ if (!first)
+ cerr << ", ";
+ PrintNode(&GraphNodes[*bi]);
+ first = false;
+ }
+ cerr << "\n";
}
- std::cerr << "\n";
}
}
projects / oota-llvm.git / blobdiff