[llvm-commits] [llvm] r42016 - /llvm/trunk/lib/Analysis/IPA/Andersens.cpp
Daniel Berlin
dberlin at dberlin.org
Sun Sep 16 14:45:03 PDT 2007
Author: dannyb
Date: Sun Sep 16 16:45:02 2007
New Revision: 42016
URL: http://llvm.org/viewvc/llvm-project?rev=42016&view=rev
Log:
Rewrite of andersen's to be about 100x faster, cleaner, and begin to support field sensitivity
Modified:
llvm/trunk/lib/Analysis/IPA/Andersens.cpp
Modified: llvm/trunk/lib/Analysis/IPA/Andersens.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/IPA/Andersens.cpp?rev=42016&r1=42015&r2=42016&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/IPA/Andersens.cpp (original)
+++ llvm/trunk/lib/Analysis/IPA/Andersens.cpp Sun Sep 16 16:45:02 2007
@@ -7,14 +7,11 @@
//
//===----------------------------------------------------------------------===//
//
-// 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.
@@ -29,24 +26,23 @@
// 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 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 equivalence 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 variable substitution, offline detection of online
+// cycles. Use of BDD's.
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "anders-aa"
@@ -62,31 +58,77 @@
#include "llvm/Analysis/Passes.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SparseBitVector.h"
#include <algorithm>
#include <set>
-using namespace llvm;
+#include <list>
+#include <stack>
+#include <vector>
+using namespace llvm;
STATISTIC(NumIters , "Number of iterations to reach convergence");
STATISTIC(NumConstraints , "Number of constraints");
STATISTIC(NumNodes , "Number of nodes");
-STATISTIC(NumEscapingFunctions, "Number of internal functions that escape");
-STATISTIC(NumIndirectCallees , "Number of indirect callees found");
+STATISTIC(NumUnified , "Number of variables unified");
namespace {
+ const unsigned SelfRep = (unsigned)-1;
+ const unsigned Unvisited = (unsigned)-1;
+ // Position of the function return node relative to the function node.
+ const unsigned CallReturnPos = 2;
+ // Position of the function call node relative to the function node.
+ const unsigned CallFirstArgPos = 3;
+
class VISIBILITY_HIDDEN Andersens : public ModulePass, public AliasAnalysis,
private InstVisitor<Andersens> {
- public:
- static char ID; // Class identification, replacement for typeinfo
- Andersens() : ModulePass((intptr_t)&ID) {}
- private:
- /// Node class - This class is used to represent a memory object in the
- /// program, and is the primitive used to build the points-to graph.
- class Node {
- std::vector<Node*> Pointees;
- Value *Val;
- public:
- static const unsigned ID; // Pass identification, replacement for typeid
- Node() : Val(0) {}
+ class 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");
+ }
+ };
+
+ // Node class - This class is used to represent a node
+ // in the constraint graph. Due to various optimizations,
+ // 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 {
+ Value *Val;
+ SparseBitVector<> *Edges;
+ SparseBitVector<> *PointsTo;
+ SparseBitVector<> *OldPointsTo;
+ bool Changed;
+ std::list<Constraint> Constraints;
+
+ // 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
+ // representative for this one.
+ unsigned NodeRep; public:
+
+ Node() : Val(0), Edges(0), PointsTo(0), OldPointsTo(0), Changed(false),
+ NodeRep(SelfRep) {
+ }
+
Node *setValue(Value *V) {
assert(Val == 0 && "Value already set for this node!");
Val = V;
@@ -97,21 +139,11 @@
///
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
@@ -121,12 +153,7 @@
/// intersectsIgnoring - Return true if the points-to set of this node
/// intersects with the points-to set of the specified node on any nodes
/// except for the specified node to ignore.
- bool intersectsIgnoring(Node *N, Node *Ignoring) const;
-
- // Constraint application methods.
- bool copyFrom(Node *N);
- bool loadFrom(Node *N);
- bool storeThrough(Node *N);
+ bool intersectsIgnoring(Node *N, unsigned) const;
};
/// GraphNodes - This vector is populated as part of the object
@@ -152,41 +179,14 @@
/// take variable arguments.
std::map<Function*, unsigned> VarargNodes;
- /// Constraint - Objects of this structure are used to represent the various
- /// constraints identified by the algorithm. The constraints are 'copy',
- /// for statements like "A = B", 'load' for statements like "A = *B", and
- /// 'store' for statements like "*A = B".
- struct Constraint {
- enum ConstraintType { Copy, Load, Store } Type;
- Node *Dest, *Src;
-
- Constraint(ConstraintType Ty, Node *D, Node *S)
- : Type(Ty), Dest(D), Src(S) {}
- };
/// Constraints - This vector contains a list of all of the constraints
/// identified by the program.
std::vector<Constraint> Constraints;
- /// EscapingInternalFunctions - This set contains all of the internal
- /// functions that are found to escape from the program. If the address of
- /// an internal function is passed to an external function or otherwise
- /// escapes from the analyzed portion of the program, we must assume that
- /// any pointer arguments can alias the universal node. This set keeps
- /// track of those functions we are assuming to escape so far.
- std::set<Function*> EscapingInternalFunctions;
-
- /// IndirectCalls - This contains a list of all of the indirect call sites
- /// in the program. Since the call graph is iteratively discovered, we may
- /// need to add constraints to our graph as we find new targets of function
- /// pointers.
- std::vector<CallSite> IndirectCalls;
-
- /// IndirectCallees - For each call site in the indirect calls list, keep
- /// track of the callees that we have discovered so far. As the analysis
- /// proceeds, more callees are discovered, until the call graph finally
- /// stabilizes.
- std::map<CallSite, std::vector<Function*> > IndirectCallees;
+ // 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.
@@ -195,8 +195,24 @@
NullPtr = 1,
NullObject = 2
};
+ // Stack for Tarjans
+ std::stack<unsigned> SCCStack;
+ // Topological Index -> Graph node
+ std::vector<unsigned> Topo2Node;
+ // Graph Node -> Topological Index;
+ std::vector<unsigned> Node2Topo;
+ // Map from Graph Node to DFS number
+ std::vector<unsigned> Node2DFS;
+ // Map from Graph Node to Deleted from graph.
+ std::vector<bool> Node2Deleted;
+ // Current DFS and RPO numbers
+ unsigned DFSNumber;
+ unsigned RPONumber;
public:
+ static char ID;
+ Andersens() : ModulePass((intptr_t)&ID) {}
+
bool runOnModule(Module &M) {
InitializeAliasAnalysis(this);
IdentifyObjects(M);
@@ -210,7 +226,6 @@
ObjectNodes.clear();
ReturnNodes.clear();
VarargNodes.clear();
- EscapingInternalFunctions.clear();
std::vector<Constraint>().swap(Constraints);
return false;
}
@@ -255,7 +270,7 @@
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);
@@ -267,47 +282,55 @@
#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) {
+ unsigned getObject(Value *V) {
std::map<Value*, unsigned>::iterator I = ObjectNodes.find(V);
assert(I != ObjectNodes.end() &&
"Value does not have an object in the points-to graph!");
- return &GraphNodes[I->second];
+ return I->second;
}
/// getReturnNode - Return the node representing the return value for the
/// specified function.
- Node *getReturnNode(Function *F) {
+ unsigned getReturnNode(Function *F) {
std::map<Function*, unsigned>::iterator I = ReturnNodes.find(F);
assert(I != ReturnNodes.end() && "Function does not return a value!");
- return &GraphNodes[I->second];
+ return I->second;
}
/// getVarargNode - Return the node representing the variable arguments
/// formal for the specified function.
- Node *getVarargNode(Function *F) {
+ unsigned getVarargNode(Function *F) {
std::map<Function*, unsigned>::iterator I = VarargNodes.find(F);
assert(I != VarargNodes.end() && "Function does not take var args!");
- return &GraphNodes[I->second];
+ 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);
+ unsigned FindNode(unsigned Node);
+
void IdentifyObjects(Module &M);
void CollectConstraints(Module &M);
+ bool AnalyzeUsesOfFunction(Value *);
+ void CreateConstraintGraph();
void SolveConstraints();
+ void QueryNode(unsigned Node);
- Node *getNodeForConstantPointer(Constant *C);
- Node *getNodeForConstantPointerTarget(Constant *C);
- void AddGlobalInitializerConstraints(Node *N, Constant *C);
+ unsigned getNodeForConstantPointer(Constant *C);
+ unsigned getNodeForConstantPointerTarget(Constant *C);
+ void AddGlobalInitializerConstraints(unsigned, Constant *C);
void AddConstraintsForNonInternalLinkage(Function *F);
void AddConstraintsForCall(CallSite CS, Function *F);
@@ -337,6 +360,7 @@
void visitSelectInst(SelectInst &SI);
void visitVAArg(VAArgInst &I);
void visitInstruction(Instruction &I);
+
};
char Andersens::ID = 0;
@@ -353,12 +377,12 @@
AliasAnalysis::AliasResult Andersens::alias(const Value *V1, unsigned V1Size,
const Value *V2, unsigned V2Size) {
- Node *N1 = getNode(const_cast<Value*>(V1));
- Node *N2 = getNode(const_cast<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);
@@ -376,14 +400,12 @@
// is, after all, a "research quality" implementation of Andersen's analysis.
if (Function *F = CS.getCalledFunction())
if (F->isDeclaration()) {
- Node *N1 = getNode(P);
+ Node *N1 = &GraphNodes[FindNode(getNode(P))];
- if (N1->begin() == N1->end())
- return NoModRef; // P doesn't point to anything.
+ if (N1->PointsTo->empty())
+ return NoModRef;
- // Get the first pointee.
- Node *FirstPointee = *N1->begin();
- if (FirstPointee != &GraphNodes[UniversalSet])
+ if (!N1->PointsTo->test(UniversalSet))
return NoModRef; // P doesn't point to the universal set.
}
@@ -401,30 +423,23 @@
/// 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);
}
@@ -434,14 +449,20 @@
/// 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);
}
}
@@ -483,6 +504,7 @@
// 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()))
@@ -490,11 +512,14 @@
if (F->getFunctionType()->isVarArg())
VarargNodes[F] = NumObjects++;
+
// Add nodes for all of the incoming pointer arguments.
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;
+ MaxK[First + 1] = NumObjects - First - 1;
// 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
@@ -521,11 +546,11 @@
/// 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) || isa<UndefValue>(C))
- return &GraphNodes[NullPtr];
+ return NullPtr;
else if (GlobalValue *GV = dyn_cast<GlobalValue>(C))
return getNode(GV);
else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
@@ -533,7 +558,7 @@
case Instruction::GetElementPtr:
return getNodeForConstantPointer(CE->getOperand(0));
case Instruction::IntToPtr:
- return &GraphNodes[UniversalSet];
+ return UniversalSet;
case Instruction::BitCast:
return getNodeForConstantPointer(CE->getOperand(0));
default:
@@ -548,11 +573,11 @@
/// 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)) {
@@ -560,7 +585,7 @@
case Instruction::GetElementPtr:
return getNodeForConstantPointerTarget(CE->getOperand(0));
case Instruction::IntToPtr:
- return &GraphNodes[UniversalSet];
+ return UniversalSet;
case Instruction::BitCast:
return getNodeForConstantPointerTarget(CE->getOperand(0));
default:
@@ -575,19 +600,22 @@
/// 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->copyFrom(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 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)));
}
}
@@ -600,7 +628,7 @@
// 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
@@ -653,14 +681,20 @@
// These functions do induce points-to edges.
- if (F->getName() == "llvm.memcpy.i32" || F->getName() == "llvm.memcpy.i64" ||
+ if (F->getName() == "llvm.memcpy.i32" || F->getName() == "llvm.memcpy.i64" ||
F->getName() == "llvm.memmove.i32" ||F->getName() == "llvm.memmove.i64" ||
F->getName() == "memmove") {
- // Note: this is a poor approximation, this says Dest = Src, instead of
- // *Dest = *Src.
- Constraints.push_back(Constraint(Constraint::Copy,
- getNode(CS.getArgument(0)),
- getNode(CS.getArgument(1))));
+
+ // *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;
}
@@ -679,49 +713,99 @@
+/// 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::Load, &GraphNodes[UniversalSet],
- // &GraphNodes[UniversalSet]));
- Constraints.push_back(Constraint(Constraint::Store, &GraphNodes[UniversalSet],
- &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::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));
-
+ unsigned ObjectIndex = getObject(F);
+ GraphNodes[ObjectIndex].setValue(F);
+ Constraints.push_back(Constraint(Constraint::AddressOf, getNodeValue(*F),
+ ObjectIndex));
// 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::arg_iterator I = F->arg_begin(), E = F->arg_end();
@@ -729,7 +813,10 @@
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->isDeclaration()) {
@@ -742,7 +829,7 @@
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.
@@ -752,11 +839,11 @@
// 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.
Constraints.push_back(Constraint(Constraint::Copy,
- &GraphNodes[UniversalSet],
+ UniversalSet,
getNode(I)));
}
@@ -764,7 +851,7 @@
// 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();
@@ -795,7 +882,10 @@
}
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) {
@@ -829,7 +919,7 @@
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,
@@ -848,7 +938,7 @@
// P1 = cast int --> <Copy/P1/Univ>
#if 0
Constraints.push_back(Constraint(Constraint::Copy, getNodeValue(CI),
- &GraphNodes[UniversalSet]));
+ UniversalSet));
#else
getNodeValue(CI);
#endif
@@ -857,7 +947,7 @@
// 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));
@@ -867,7 +957,7 @@
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))));
@@ -886,48 +976,72 @@
/// the function pointer has been casted. If this is the case, do something
/// reasonable.
void Andersens::AddConstraintsForCall(CallSite CS, Function *F) {
- // If this is a call to an external function, handle it directly to get some
- // taste of context sensitivity.
- if (F->isDeclaration() && AddConstraintsForExternalCall(CS, 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())) {
Constraints.push_back(Constraint(Constraint::Copy,
- &GraphNodes[UniversalSet],
- getReturnNode(F)));
+ UniversalSet,
+ getNode(CallValue) + CallReturnPos));
}
- Function::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
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())) {
+ Constraints.push_back(Constraint(Constraint::Copy,
+ UniversalSet,
+ getNode(*ArgI)));
+ }
+ } 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),
@@ -942,9 +1056,7 @@
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);
}
}
@@ -955,74 +1067,109 @@
/// 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;
+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;
+}
+
+// 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
- ++I2;
+ GraphNodes[C.Src].Edges->set(C.Dest);
}
- return false;
}
-// Copy constraint: all edges out of the source node get copied to the
-// destination node. This returns true if a change is made.
-bool Andersens::Node::copyFrom(Node *N) {
- // Use a mostly linear-time merge since both of the lists are sorted.
- bool Changed = false;
- iterator I = N->begin(), E = N->end();
- unsigned i = 0;
- while (I != E && i != Pointees.size()) {
- if (Pointees[i] < *I) {
- ++i;
- } else if (Pointees[i] == *I) {
- ++i; ++I;
- } else {
- // We found a new element to copy over.
- Changed = true;
- Pointees.insert(Pointees.begin()+i, *I);
- ++i; ++I;
+// Perform cycle detection, DFS, and RPO finding.
+void Andersens::QueryNode(unsigned Node) {
+ assert(GraphNodes[Node].NodeRep == SelfRep && "Querying a non-rep node");
+ unsigned OurDFS = ++DFSNumber;
+ SparseBitVector<> ToErase;
+ SparseBitVector<> NewEdges;
+ Node2DFS[Node] = OurDFS;
+
+ for (SparseBitVector<>::iterator bi = GraphNodes[Node].Edges->begin();
+ bi != GraphNodes[Node].Edges->end();
+ ++bi) {
+ unsigned RepNode = FindNode(*bi);
+ // If we are going to add an edge to repnode, we have no need for the edge
+ // to e anymore.
+ if (RepNode != *bi && NewEdges.test(RepNode)){
+ ToErase.set(*bi);
+ continue;
+ }
+
+ // Continue about our DFS.
+ if (!Node2Deleted[RepNode]){
+ if (Node2DFS[RepNode] == 0) {
+ QueryNode(RepNode);
+ // May have been changed by query
+ RepNode = FindNode(RepNode);
+ }
+ if (Node2DFS[RepNode] < Node2DFS[Node])
+ Node2DFS[Node] = Node2DFS[RepNode];
+ }
+ // We may have just discovered that e belongs to a cycle, in which case we
+ // can also erase it.
+ if (RepNode != *bi) {
+ ToErase.set(*bi);
+ NewEdges.set(RepNode);
}
}
- if (I != E) {
- Pointees.insert(Pointees.end(), I, E);
- Changed = true;
- }
+ GraphNodes[Node].Edges->intersectWithComplement(ToErase);
+ GraphNodes[Node].Edges |= NewEdges;
- return Changed;
-}
+ // If this node is a root of a non-trivial SCC, place it on our worklist to be
+ // processed
+ if (OurDFS == Node2DFS[Node]) {
+ bool Changed = false;
+ while (!SCCStack.empty() && Node2DFS[SCCStack.top()] >= OurDFS) {
+ Node = UniteNodes(Node, FindNode(SCCStack.top()));
-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;
-}
+ SCCStack.pop();
+ Changed = true;
+ }
+ Node2Deleted[Node] = true;
+ RPONumber++;
-bool Andersens::Node::storeThrough(Node *N) {
- bool Changed = false;
- for (iterator I = begin(), E = end(); I != E; ++I)
- Changed |= (*I)->copyFrom(N);
- return Changed;
+ Topo2Node.at(GraphNodes.size() - RPONumber) = Node;
+ Node2Topo[Node] = GraphNodes.size() - RPONumber;
+ if (Changed)
+ GraphNodes[Node].Changed = true;
+ } else {
+ SCCStack.push(Node);
+ }
}
@@ -1033,73 +1180,257 @@
void Andersens::SolveConstraints() {
bool Changed = true;
unsigned Iteration = 0;
- while (Changed) {
- Changed = false;
- ++NumIters;
- DOUT << "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!");
- }
+ // We create the bitmaps here to avoid getting jerked around by the compiler
+ // creating objects behind our back and wasting lots of memory.
+ 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();
+
+ Topo2Node.insert(Topo2Node.begin(), GraphNodes.size(), Unvisited);
+ Node2Topo.insert(Node2Topo.begin(), GraphNodes.size(), Unvisited);
+ Node2DFS.insert(Node2DFS.begin(), GraphNodes.size(), 0);
+ Node2Deleted.insert(Node2Deleted.begin(), GraphNodes.size(), false);
+ DFSNumber = 0;
+ RPONumber = 0;
+ // Order graph and mark starting nodes as changed.
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ unsigned N = FindNode(i);
+ Node *INode = &GraphNodes[i];
+ if (Node2DFS[N] == 0) {
+ QueryNode(N);
+ // Mark as changed if it's a representation and can contribute to the
+ // calculation right now.
+ if (INode->NodeRep == SelfRep && !INode->PointsTo->empty()
+ && (!INode->Edges->empty() || !INode->Constraints.empty()))
+ INode->Changed = true;
}
+ }
- 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);
- DOUT << "Found escaping internal function: " << F->getName() <<"\n";
- ++NumEscapingFunctions;
- }
+ do {
+ Changed = false;
- // 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);
- DOUT << "Found actual callee '"
- << F->getName() << "' for call: "
- << *CS.getInstruction() << "\n";
- ++NumIndirectCallees;
- KnownCallees.insert(IP, F);
+ ++NumIters;
+ DOUT << "Starting iteration #" << Iteration++ << "!\n";
+ // TODO: In the microoptimization category, we could just make Topo2Node
+ // a fast map and thus only contain the visited nodes.
+ for (unsigned i = 0; i < GraphNodes.size(); ++i) {
+ unsigned CurrNodeIndex = Topo2Node[i];
+ Node *CurrNode;
+
+ // We may not revisit all nodes on every iteration
+ if (CurrNodeIndex == Unvisited)
+ continue;
+ CurrNode = &GraphNodes[CurrNodeIndex];
+ // See if this is a node we need to process on this iteration
+ if (!CurrNode->Changed || CurrNode->NodeRep != SelfRep)
+ continue;
+ CurrNode->Changed = false;
+
+ // Figure out the changed points to bits
+ SparseBitVector<> CurrPointsTo;
+ CurrPointsTo.intersectWithComplement(CurrNode->PointsTo,
+ CurrNode->OldPointsTo);
+ if (CurrPointsTo.empty()){
+ continue;
+ }
+ *(CurrNode->OldPointsTo) |= CurrPointsTo;
+
+ /* 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);
+
+ // TODO: We could delete redundant constraints here.
+ // 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 function.
+ // 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
+ // Node 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 (!GraphNodes[*Src].Edges->test_and_set(*Dest)) {
+ if (GraphNodes[*Dest].PointsTo |= *(GraphNodes[*Src].PointsTo)) {
+ GraphNodes[*Dest].Changed = true;
+ // If we changed a node we've already processed, we need another
+ // iteration.
+ if (Node2Topo[*Dest] <= i)
+ Changed = true;
}
}
+ }
+ 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;
+ }
+ // Union the points-to sets into the dest
+ if (GraphNodes[Rep].PointsTo |= CurrPointsTo) {
+ GraphNodes[Rep].Changed = true;
+ if (Node2Topo[Rep] <= i)
+ Changed = true;
+ }
+ // 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;
}
+ if (Changed) {
+ DFSNumber = RPONumber = 0;
+ Node2Deleted.clear();
+ Topo2Node.clear();
+ Node2Topo.clear();
+ Node2DFS.clear();
+ Topo2Node.insert(Topo2Node.begin(), GraphNodes.size(), Unvisited);
+ Node2Topo.insert(Node2Topo.begin(), GraphNodes.size(), Unvisited);
+ Node2DFS.insert(Node2DFS.begin(), GraphNodes.size(), 0);
+ Node2Deleted.insert(Node2Deleted.begin(), GraphNodes.size(), false);
+ // Rediscover the DFS/Topo ordering, and cycle detect.
+ for (unsigned j = 0; j < GraphNodes.size(); j++) {
+ unsigned JRep = FindNode(j);
+ if (Node2DFS[JRep] == 0)
+ QueryNode(JRep);
+ }
+ }
+
+ } while (Changed);
+
+ Node2Topo.clear();
+ Topo2Node.clear();
+ 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) {
+ assert (First < GraphNodes.size() && Second < GraphNodes.size() &&
+ "Attempting to merge nodes that don't exist");
+ // TODO: implement union by rank
+ Node *FirstNode = &GraphNodes[First];
+ Node *SecondNode = &GraphNodes[Second];
+
+ assert (SecondNode->NodeRep == SelfRep && FirstNode->NodeRep == SelfRep &&
+ "Trying to unite two non-representative nodes!");
+ if (First == Second)
+ return First;
+
+ SecondNode->NodeRep = First;
+ FirstNode->Changed |= SecondNode->Changed;
+ FirstNode->PointsTo |= *(SecondNode->PointsTo);
+ FirstNode->Edges |= *(SecondNode->Edges);
+ FirstNode->Constraints.splice(FirstNode->Constraints.begin(),
+ SecondNode->Constraints);
+ 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->NodeRep == SelfRep)
+ return NodeIndex;
+ else
+ return (N->NodeRep = FindNode(N->NodeRep));
+}
//===----------------------------------------------------------------------===//
// Debugging Output
@@ -1116,15 +1447,20 @@
cerr << "<null>";
return;
}
+ if (!N->getValue()) {
+ cerr << "artificial" << (intptr_t) N;
+ return;
+ }
assert(N->getValue() != 0 && "Never set node label!");
Value *V = N->getValue();
if (Function *F = dyn_cast<Function>(V)) {
if (isa<PointerType>(F->getFunctionType()->getReturnType()) &&
- N == getReturnNode(F)) {
+ N == &GraphNodes[getReturnNode(F)]) {
cerr << F->getName() << ":retval";
return;
- } else if (F->getFunctionType()->isVarArg() && N == getVarargNode(F)) {
+ } else if (F->getFunctionType()->isVarArg() &&
+ N == &GraphNodes[getVarargNode(F)]) {
cerr << F->getName() << ":vararg";
return;
}
@@ -1141,22 +1477,36 @@
cerr << "(unnamed)";
if (isa<GlobalValue>(V) || isa<AllocationInst>(V))
- if (N == getObject(V))
+ if (N == &GraphNodes[getObject(V)])
cerr << "<mem>";
}
void Andersens::PrintConstraints() {
cerr << "Constraints:\n";
+
for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
- cerr << " #" << i << ": ";
- Constraint &C = Constraints[i];
- if (C.Type == Constraint::Store)
+ const Constraint &C = Constraints[i];
+ if (C.Type == Constraint::Store) {
cerr << "*";
- PrintNode(C.Dest);
+ 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)
+ if (C.Type == Constraint::Load) {
cerr << "*";
- PrintNode(C.Src);
+ 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";
}
}
@@ -1165,13 +1515,26 @@
cerr << "Points-to graph:\n";
for (unsigned i = 0, e = GraphNodes.size(); i != e; ++i) {
Node *N = &GraphNodes[i];
- cerr << "[" << (N->end() - N->begin()) << "] ";
- PrintNode(N);
- cerr << "\t--> ";
- for (Node::iterator I = N->begin(), E = N->end(); I != E; ++I) {
- if (I != N->begin()) 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";
}
- cerr << "\n";
}
}
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