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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17052 91177308-0d34-0410-b5e6-96231b3b80d8
1040 lines
39 KiB
C++
1040 lines
39 KiB
C++
//===- Andersens.cpp - Andersen's Interprocedural Alias Analysis ----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines a very simple implementation of Andersen's interprocedural
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// alias analysis. This implementation does not include any of the fancy
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// features that make Andersen's reasonably efficient (like cycle elimination or
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// variable substitution), but it should be useful for getting precision
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// numbers and can be extended in the future.
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//
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// In pointer analysis terms, this is a subset-based, flow-insensitive,
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// field-insensitive, and context-insensitive algorithm pointer algorithm.
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//
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// This algorithm is implemented as three stages:
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// 1. Object identification.
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// 2. Inclusion constraint identification.
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// 3. Inclusion constraint solving.
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//
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// The object identification stage identifies all of the memory objects in the
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// program, which includes globals, heap allocated objects, and stack allocated
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// objects.
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//
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// The inclusion constraint identification stage finds all inclusion constraints
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// in the program by scanning the program, looking for pointer assignments and
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// other statements that effect the points-to graph. For a statement like "A =
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// B", this statement is processed to indicate that A can point to anything that
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// B can point to. Constraints can handle copies, loads, and stores.
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//
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// The inclusion constraint solving phase iteratively propagates the inclusion
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// constraints until a fixed point is reached. This is an O(N^3) algorithm.
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//
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// In the initial pass, all indirect function calls are completely ignored. As
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// the analysis discovers new targets of function pointers, it iteratively
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// resolves a precise (and conservative) call graph. Also related, this
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// analysis initially assumes that all internal functions have known incoming
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// pointers. If we find that an internal function's address escapes outside of
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// the program, we update this assumption.
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//
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// Future Improvements:
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// This implementation of Andersen's algorithm is extremely slow. To make it
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// scale reasonably well, the inclusion constraints could be sorted (easy),
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// offline variable substitution would be a huge win (straight-forward), and
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// online cycle elimination (trickier) might help as well.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "anders-aa"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/InstIterator.h"
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#include "llvm/Support/InstVisitor.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/Statistic.h"
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#include <set>
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using namespace llvm;
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namespace {
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Statistic<>
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NumIters("anders-aa", "Number of iterations to reach convergence");
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Statistic<>
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NumConstraints("anders-aa", "Number of constraints");
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Statistic<>
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NumNodes("anders-aa", "Number of nodes");
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Statistic<>
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NumEscapingFunctions("anders-aa", "Number of internal functions that escape");
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Statistic<>
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NumIndirectCallees("anders-aa", "Number of indirect callees found");
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class Andersens : public ModulePass, public AliasAnalysis,
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private InstVisitor<Andersens> {
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/// Node class - This class is used to represent a memory object in the
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/// program, and is the primitive used to build the points-to graph.
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class Node {
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std::vector<Node*> Pointees;
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Value *Val;
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public:
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Node() : Val(0) {}
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Node *setValue(Value *V) {
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assert(Val == 0 && "Value already set for this node!");
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Val = V;
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return this;
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}
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/// getValue - Return the LLVM value corresponding to this node.
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Value *getValue() const { return Val; }
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typedef std::vector<Node*>::const_iterator iterator;
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iterator begin() const { return Pointees.begin(); }
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iterator end() const { return Pointees.end(); }
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/// addPointerTo - Add a pointer to the list of pointees of this node,
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/// returning true if this caused a new pointer to be added, or false if
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/// we already knew about the points-to relation.
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bool addPointerTo(Node *N) {
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std::vector<Node*>::iterator I = std::lower_bound(Pointees.begin(),
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Pointees.end(),
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N);
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if (I != Pointees.end() && *I == N)
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return false;
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Pointees.insert(I, N);
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return true;
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}
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/// intersects - Return true if the points-to set of this node intersects
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/// with the points-to set of the specified node.
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bool intersects(Node *N) const;
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/// intersectsIgnoring - Return true if the points-to set of this node
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/// intersects with the points-to set of the specified node on any nodes
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/// except for the specified node to ignore.
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bool intersectsIgnoring(Node *N, Node *Ignoring) const;
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// Constraint application methods.
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bool copyFrom(Node *N);
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bool loadFrom(Node *N);
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bool storeThrough(Node *N);
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};
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/// GraphNodes - This vector is populated as part of the object
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/// identification stage of the analysis, which populates this vector with a
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/// node for each memory object and fills in the ValueNodes map.
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std::vector<Node> GraphNodes;
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/// ValueNodes - This map indicates the Node that a particular Value* is
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/// represented by. This contains entries for all pointers.
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std::map<Value*, unsigned> ValueNodes;
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/// ObjectNodes - This map contains entries for each memory object in the
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/// program: globals, alloca's and mallocs.
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std::map<Value*, unsigned> ObjectNodes;
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/// ReturnNodes - This map contains an entry for each function in the
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/// program that returns a value.
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std::map<Function*, unsigned> ReturnNodes;
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/// VarargNodes - This map contains the entry used to represent all pointers
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/// passed through the varargs portion of a function call for a particular
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/// function. An entry is not present in this map for functions that do not
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/// take variable arguments.
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std::map<Function*, unsigned> VarargNodes;
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/// Constraint - Objects of this structure are used to represent the various
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/// constraints identified by the algorithm. The constraints are 'copy',
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/// for statements like "A = B", 'load' for statements like "A = *B", and
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/// 'store' for statements like "*A = B".
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struct Constraint {
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enum ConstraintType { Copy, Load, Store } Type;
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Node *Dest, *Src;
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Constraint(ConstraintType Ty, Node *D, Node *S)
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: Type(Ty), Dest(D), Src(S) {}
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};
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/// Constraints - This vector contains a list of all of the constraints
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/// identified by the program.
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std::vector<Constraint> Constraints;
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/// EscapingInternalFunctions - This set contains all of the internal
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/// functions that are found to escape from the program. If the address of
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/// an internal function is passed to an external function or otherwise
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/// escapes from the analyzed portion of the program, we must assume that
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/// any pointer arguments can alias the universal node. This set keeps
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/// track of those functions we are assuming to escape so far.
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std::set<Function*> EscapingInternalFunctions;
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/// IndirectCalls - This contains a list of all of the indirect call sites
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/// in the program. Since the call graph is iteratively discovered, we may
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/// need to add constraints to our graph as we find new targets of function
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/// pointers.
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std::vector<CallSite> IndirectCalls;
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/// IndirectCallees - For each call site in the indirect calls list, keep
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/// track of the callees that we have discovered so far. As the analysis
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/// proceeds, more callees are discovered, until the call graph finally
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/// stabilizes.
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std::map<CallSite, std::vector<Function*> > IndirectCallees;
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/// This enum defines the GraphNodes indices that correspond to important
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/// fixed sets.
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enum {
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UniversalSet = 0,
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NullPtr = 1,
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NullObject = 2,
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};
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public:
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bool runOnModule(Module &M) {
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InitializeAliasAnalysis(this);
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IdentifyObjects(M);
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CollectConstraints(M);
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DEBUG(PrintConstraints());
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SolveConstraints();
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DEBUG(PrintPointsToGraph());
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// Free the constraints list, as we don't need it to respond to alias
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// requests.
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ObjectNodes.clear();
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ReturnNodes.clear();
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VarargNodes.clear();
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EscapingInternalFunctions.clear();
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std::vector<Constraint>().swap(Constraints);
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return false;
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}
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void releaseMemory() {
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// FIXME: Until we have transitively required passes working correctly,
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// this cannot be enabled! Otherwise, using -count-aa with the pass
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// causes memory to be freed too early. :(
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#if 0
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// The memory objects and ValueNodes data structures at the only ones that
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// are still live after construction.
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std::vector<Node>().swap(GraphNodes);
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ValueNodes.clear();
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#endif
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AliasAnalysis::getAnalysisUsage(AU);
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AU.setPreservesAll(); // Does not transform code
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}
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//------------------------------------------------
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// Implement the AliasAnalysis API
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//
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AliasResult alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size);
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void getMustAliases(Value *P, std::vector<Value*> &RetVals);
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bool pointsToConstantMemory(const Value *P);
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virtual void deleteValue(Value *V) {
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ValueNodes.erase(V);
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getAnalysis<AliasAnalysis>().deleteValue(V);
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}
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virtual void copyValue(Value *From, Value *To) {
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ValueNodes[To] = ValueNodes[From];
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getAnalysis<AliasAnalysis>().copyValue(From, To);
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}
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private:
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/// getNode - Return the node corresponding to the specified pointer scalar.
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///
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Node *getNode(Value *V) {
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if (Constant *C = dyn_cast<Constant>(V))
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if (!isa<GlobalValue>(C))
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return getNodeForConstantPointer(C);
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std::map<Value*, unsigned>::iterator I = ValueNodes.find(V);
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if (I == ValueNodes.end()) {
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V->dump();
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assert(I != ValueNodes.end() &&
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"Value does not have a node in the points-to graph!");
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}
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return &GraphNodes[I->second];
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}
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/// getObject - Return the node corresponding to the memory object for the
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/// specified global or allocation instruction.
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Node *getObject(Value *V) {
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std::map<Value*, unsigned>::iterator I = ObjectNodes.find(V);
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assert(I != ObjectNodes.end() &&
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"Value does not have an object in the points-to graph!");
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return &GraphNodes[I->second];
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}
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/// getReturnNode - Return the node representing the return value for the
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/// specified function.
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Node *getReturnNode(Function *F) {
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std::map<Function*, unsigned>::iterator I = ReturnNodes.find(F);
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assert(I != ReturnNodes.end() && "Function does not return a value!");
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return &GraphNodes[I->second];
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}
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/// getVarargNode - Return the node representing the variable arguments
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/// formal for the specified function.
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Node *getVarargNode(Function *F) {
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std::map<Function*, unsigned>::iterator I = VarargNodes.find(F);
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assert(I != VarargNodes.end() && "Function does not take var args!");
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return &GraphNodes[I->second];
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}
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/// getNodeValue - Get the node for the specified LLVM value and set the
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/// value for it to be the specified value.
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Node *getNodeValue(Value &V) {
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return getNode(&V)->setValue(&V);
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}
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void IdentifyObjects(Module &M);
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void CollectConstraints(Module &M);
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void SolveConstraints();
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Node *getNodeForConstantPointer(Constant *C);
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Node *getNodeForConstantPointerTarget(Constant *C);
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void AddGlobalInitializerConstraints(Node *N, Constant *C);
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void AddConstraintsForNonInternalLinkage(Function *F);
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void AddConstraintsForCall(CallSite CS, Function *F);
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void PrintNode(Node *N);
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void PrintConstraints();
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void PrintPointsToGraph();
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//===------------------------------------------------------------------===//
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// Instruction visitation methods for adding constraints
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//
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friend class InstVisitor<Andersens>;
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void visitReturnInst(ReturnInst &RI);
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void visitInvokeInst(InvokeInst &II) { visitCallSite(CallSite(&II)); }
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void visitCallInst(CallInst &CI) { visitCallSite(CallSite(&CI)); }
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void visitCallSite(CallSite CS);
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void visitAllocationInst(AllocationInst &AI);
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void visitLoadInst(LoadInst &LI);
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void visitStoreInst(StoreInst &SI);
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void visitGetElementPtrInst(GetElementPtrInst &GEP);
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void visitPHINode(PHINode &PN);
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void visitCastInst(CastInst &CI);
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void visitSelectInst(SelectInst &SI);
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void visitVANext(VANextInst &I);
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void visitVAArg(VAArgInst &I);
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void visitInstruction(Instruction &I);
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};
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RegisterOpt<Andersens> X("anders-aa",
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"Andersen's Interprocedural Alias Analysis");
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RegisterAnalysisGroup<AliasAnalysis, Andersens> Y;
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}
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//===----------------------------------------------------------------------===//
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// AliasAnalysis Interface Implementation
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//===----------------------------------------------------------------------===//
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AliasAnalysis::AliasResult Andersens::alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size) {
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Node *N1 = getNode((Value*)V1);
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Node *N2 = getNode((Value*)V2);
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// Check to see if the two pointers are known to not alias. They don't alias
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// if their points-to sets do not intersect.
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if (!N1->intersectsIgnoring(N2, &GraphNodes[NullObject]))
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return NoAlias;
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return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
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}
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/// getMustAlias - We can provide must alias information if we know that a
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/// pointer can only point to a specific function or the null pointer.
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/// Unfortunately we cannot determine must-alias information for global
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/// variables or any other memory memory objects because we do not track whether
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/// a pointer points to the beginning of an object or a field of it.
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void Andersens::getMustAliases(Value *P, std::vector<Value*> &RetVals) {
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Node *N = getNode(P);
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Node::iterator I = N->begin();
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if (I != N->end()) {
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// If there is exactly one element in the points-to set for the object...
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++I;
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if (I == N->end()) {
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Node *Pointee = *N->begin();
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// If a function is the only object in the points-to set, then it must be
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// the destination. Note that we can't handle global variables here,
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// because we don't know if the pointer is actually pointing to a field of
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// the global or to the beginning of it.
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if (Value *V = Pointee->getValue()) {
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if (Function *F = dyn_cast<Function>(V))
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RetVals.push_back(F);
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} else {
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// If the object in the points-to set is the null object, then the null
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// pointer is a must alias.
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if (Pointee == &GraphNodes[NullObject])
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RetVals.push_back(Constant::getNullValue(P->getType()));
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}
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}
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}
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AliasAnalysis::getMustAliases(P, RetVals);
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}
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/// pointsToConstantMemory - If we can determine that this pointer only points
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/// to constant memory, return true. In practice, this means that if the
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/// pointer can only point to constant globals, functions, or the null pointer,
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/// return true.
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///
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bool Andersens::pointsToConstantMemory(const Value *P) {
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Node *N = getNode((Value*)P);
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for (Node::iterator I = N->begin(), E = N->end(); I != E; ++I) {
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if (Value *V = (*I)->getValue()) {
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if (!isa<GlobalValue>(V) || (isa<GlobalVariable>(V) &&
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!cast<GlobalVariable>(V)->isConstant()))
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return AliasAnalysis::pointsToConstantMemory(P);
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} else {
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if (*I != &GraphNodes[NullObject])
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return AliasAnalysis::pointsToConstantMemory(P);
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}
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}
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return true;
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}
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//===----------------------------------------------------------------------===//
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// Object Identification Phase
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//===----------------------------------------------------------------------===//
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/// IdentifyObjects - This stage scans the program, adding an entry to the
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/// GraphNodes list for each memory object in the program (global stack or
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/// heap), and populates the ValueNodes and ObjectNodes maps for these objects.
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///
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void Andersens::IdentifyObjects(Module &M) {
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unsigned NumObjects = 0;
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// Object #0 is always the universal set: the object that we don't know
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// anything about.
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assert(NumObjects == UniversalSet && "Something changed!");
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++NumObjects;
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// Object #1 always represents the null pointer.
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assert(NumObjects == NullPtr && "Something changed!");
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++NumObjects;
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// Object #2 always represents the null object (the object pointed to by null)
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assert(NumObjects == NullObject && "Something changed!");
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++NumObjects;
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// Add all the globals first.
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for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I) {
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ObjectNodes[I] = NumObjects++;
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ValueNodes[I] = NumObjects++;
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}
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// Add nodes for all of the functions and the instructions inside of them.
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for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
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// The function itself is a memory object.
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ValueNodes[F] = NumObjects++;
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ObjectNodes[F] = NumObjects++;
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if (isa<PointerType>(F->getFunctionType()->getReturnType()))
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ReturnNodes[F] = NumObjects++;
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if (F->getFunctionType()->isVarArg())
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VarargNodes[F] = NumObjects++;
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// Add nodes for all of the incoming pointer arguments.
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for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
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if (isa<PointerType>(I->getType()))
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ValueNodes[I] = NumObjects++;
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// Scan the function body, creating a memory object for each heap/stack
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// allocation in the body of the function and a node to represent all
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// pointer values defined by instructions and used as operands.
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for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) {
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// If this is an heap or stack allocation, create a node for the memory
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// object.
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if (isa<PointerType>(II->getType())) {
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ValueNodes[&*II] = NumObjects++;
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if (AllocationInst *AI = dyn_cast<AllocationInst>(&*II))
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ObjectNodes[AI] = NumObjects++;
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}
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}
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}
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// Now that we know how many objects to create, make them all now!
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GraphNodes.resize(NumObjects);
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NumNodes += NumObjects;
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}
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//===----------------------------------------------------------------------===//
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// Constraint Identification Phase
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//===----------------------------------------------------------------------===//
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/// getNodeForConstantPointer - Return the node corresponding to the constant
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/// pointer itself.
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Andersens::Node *Andersens::getNodeForConstantPointer(Constant *C) {
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assert(isa<PointerType>(C->getType()) && "Not a constant pointer!");
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if (isa<ConstantPointerNull>(C))
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return &GraphNodes[NullPtr];
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else if (GlobalValue *GV = dyn_cast<GlobalValue>(C))
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return getNode(GV);
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else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
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switch (CE->getOpcode()) {
|
|
case Instruction::GetElementPtr:
|
|
return getNodeForConstantPointer(CE->getOperand(0));
|
|
case Instruction::Cast:
|
|
if (isa<PointerType>(CE->getOperand(0)->getType()))
|
|
return getNodeForConstantPointer(CE->getOperand(0));
|
|
else
|
|
return &GraphNodes[UniversalSet];
|
|
default:
|
|
std::cerr << "Constant Expr not yet handled: " << *CE << "\n";
|
|
assert(0);
|
|
}
|
|
} else {
|
|
assert(0 && "Unknown constant pointer!");
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// getNodeForConstantPointerTarget - Return the node POINTED TO by the
|
|
/// specified constant pointer.
|
|
Andersens::Node *Andersens::getNodeForConstantPointerTarget(Constant *C) {
|
|
assert(isa<PointerType>(C->getType()) && "Not a constant pointer!");
|
|
|
|
if (isa<ConstantPointerNull>(C))
|
|
return &GraphNodes[NullObject];
|
|
else if (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];
|
|
default:
|
|
std::cerr << "Constant Expr not yet handled: " << *CE << "\n";
|
|
assert(0);
|
|
}
|
|
} else {
|
|
assert(0 && "Unknown constant pointer!");
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// AddGlobalInitializerConstraints - Add inclusion constraints for the memory
|
|
/// object N, which contains values indicated by C.
|
|
void Andersens::AddGlobalInitializerConstraints(Node *N, Constant *C) {
|
|
if (C->getType()->isFirstClassType()) {
|
|
if (isa<PointerType>(C->getType()))
|
|
N->addPointerTo(getNodeForConstantPointer(C));
|
|
} else if (C->isNullValue()) {
|
|
N->addPointerTo(&GraphNodes[NullObject]);
|
|
return;
|
|
} else {
|
|
// If this is an array or struct, include constraints for each element.
|
|
assert(isa<ConstantArray>(C) || isa<ConstantStruct>(C));
|
|
for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
|
|
AddGlobalInitializerConstraints(N, cast<Constant>(C->getOperand(i)));
|
|
}
|
|
}
|
|
|
|
void Andersens::AddConstraintsForNonInternalLinkage(Function *F) {
|
|
for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
|
|
if (isa<PointerType>(I->getType()))
|
|
// If this is an argument of an externally accessible function, the
|
|
// incoming pointer might point to anything.
|
|
Constraints.push_back(Constraint(Constraint::Copy, getNode(I),
|
|
&GraphNodes[UniversalSet]));
|
|
}
|
|
|
|
|
|
/// CollectConstraints - This stage scans the program, adding a constraint to
|
|
/// the Constraints list for each instruction in the program that induces a
|
|
/// constraint, and setting up the initial points-to graph.
|
|
///
|
|
void Andersens::CollectConstraints(Module &M) {
|
|
// First, the universal set points to itself.
|
|
GraphNodes[UniversalSet].addPointerTo(&GraphNodes[UniversalSet]);
|
|
|
|
// Next, the null pointer points to the null object.
|
|
GraphNodes[NullPtr].addPointerTo(&GraphNodes[NullObject]);
|
|
|
|
// Next, add any constraints on global variables and their initializers.
|
|
for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I) {
|
|
// Associate the address of the global object as pointing to the memory for
|
|
// the global: &G = <G memory>
|
|
Node *Object = getObject(I);
|
|
Object->setValue(I);
|
|
getNodeValue(*I)->addPointerTo(Object);
|
|
|
|
if (I->hasInitializer()) {
|
|
AddGlobalInitializerConstraints(Object, I->getInitializer());
|
|
} else {
|
|
// If it doesn't have an initializer (i.e. it's defined in another
|
|
// translation unit), it points to the universal set.
|
|
Constraints.push_back(Constraint(Constraint::Copy, Object,
|
|
&GraphNodes[UniversalSet]));
|
|
}
|
|
}
|
|
|
|
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
|
|
// Make the function address point to the function object.
|
|
getNodeValue(*F)->addPointerTo(getObject(F)->setValue(F));
|
|
|
|
// Set up the return value node.
|
|
if (isa<PointerType>(F->getFunctionType()->getReturnType()))
|
|
getReturnNode(F)->setValue(F);
|
|
if (F->getFunctionType()->isVarArg())
|
|
getVarargNode(F)->setValue(F);
|
|
|
|
// Set up incoming argument nodes.
|
|
for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
|
|
if (isa<PointerType>(I->getType()))
|
|
getNodeValue(*I);
|
|
|
|
if (!F->hasInternalLinkage())
|
|
AddConstraintsForNonInternalLinkage(F);
|
|
|
|
if (!F->isExternal()) {
|
|
// Scan the function body, creating a memory object for each heap/stack
|
|
// allocation in the body of the function and a node to represent all
|
|
// pointer values defined by instructions and used as operands.
|
|
visit(F);
|
|
} else {
|
|
// External functions that return pointers return the universal set.
|
|
if (isa<PointerType>(F->getFunctionType()->getReturnType()))
|
|
Constraints.push_back(Constraint(Constraint::Copy,
|
|
getReturnNode(F),
|
|
&GraphNodes[UniversalSet]));
|
|
|
|
// Any pointers that are passed into the function have the universal set
|
|
// stored into them.
|
|
for (Function::aiterator I = F->abegin(), E = F->aend(); I != E; ++I)
|
|
if (isa<PointerType>(I->getType())) {
|
|
// Pointers passed into external functions could have anything stored
|
|
// through them.
|
|
Constraints.push_back(Constraint(Constraint::Store, getNode(I),
|
|
&GraphNodes[UniversalSet]));
|
|
// Memory objects passed into external function calls can have the
|
|
// universal set point to them.
|
|
Constraints.push_back(Constraint(Constraint::Copy,
|
|
&GraphNodes[UniversalSet],
|
|
getNode(I)));
|
|
}
|
|
|
|
// If this is an external varargs function, it can also store pointers
|
|
// into any pointers passed through the varargs section.
|
|
if (F->getFunctionType()->isVarArg())
|
|
Constraints.push_back(Constraint(Constraint::Store, getVarargNode(F),
|
|
&GraphNodes[UniversalSet]));
|
|
}
|
|
}
|
|
NumConstraints += Constraints.size();
|
|
}
|
|
|
|
|
|
void Andersens::visitInstruction(Instruction &I) {
|
|
#ifdef NDEBUG
|
|
return; // This function is just a big assert.
|
|
#endif
|
|
if (isa<BinaryOperator>(I))
|
|
return;
|
|
// Most instructions don't have any effect on pointer values.
|
|
switch (I.getOpcode()) {
|
|
case Instruction::Br:
|
|
case Instruction::Switch:
|
|
case Instruction::Unwind:
|
|
case Instruction::Unreachable:
|
|
case Instruction::Free:
|
|
case Instruction::Shl:
|
|
case Instruction::Shr:
|
|
return;
|
|
default:
|
|
// Is this something we aren't handling yet?
|
|
std::cerr << "Unknown instruction: " << I;
|
|
abort();
|
|
}
|
|
}
|
|
|
|
void Andersens::visitAllocationInst(AllocationInst &AI) {
|
|
getNodeValue(AI)->addPointerTo(getObject(&AI)->setValue(&AI));
|
|
}
|
|
|
|
void Andersens::visitReturnInst(ReturnInst &RI) {
|
|
if (RI.getNumOperands() && isa<PointerType>(RI.getOperand(0)->getType()))
|
|
// return V --> <Copy/retval{F}/v>
|
|
Constraints.push_back(Constraint(Constraint::Copy,
|
|
getReturnNode(RI.getParent()->getParent()),
|
|
getNode(RI.getOperand(0))));
|
|
}
|
|
|
|
void Andersens::visitLoadInst(LoadInst &LI) {
|
|
if (isa<PointerType>(LI.getType()))
|
|
// P1 = load P2 --> <Load/P1/P2>
|
|
Constraints.push_back(Constraint(Constraint::Load, getNodeValue(LI),
|
|
getNode(LI.getOperand(0))));
|
|
}
|
|
|
|
void Andersens::visitStoreInst(StoreInst &SI) {
|
|
if (isa<PointerType>(SI.getOperand(0)->getType()))
|
|
// store P1, P2 --> <Store/P2/P1>
|
|
Constraints.push_back(Constraint(Constraint::Store,
|
|
getNode(SI.getOperand(1)),
|
|
getNode(SI.getOperand(0))));
|
|
}
|
|
|
|
void Andersens::visitGetElementPtrInst(GetElementPtrInst &GEP) {
|
|
// P1 = getelementptr P2, ... --> <Copy/P1/P2>
|
|
Constraints.push_back(Constraint(Constraint::Copy, getNodeValue(GEP),
|
|
getNode(GEP.getOperand(0))));
|
|
}
|
|
|
|
void Andersens::visitPHINode(PHINode &PN) {
|
|
if (isa<PointerType>(PN.getType())) {
|
|
Node *PNN = getNodeValue(PN);
|
|
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
|
|
// P1 = phi P2, P3 --> <Copy/P1/P2>, <Copy/P1/P3>, ...
|
|
Constraints.push_back(Constraint(Constraint::Copy, PNN,
|
|
getNode(PN.getIncomingValue(i))));
|
|
}
|
|
}
|
|
|
|
void Andersens::visitCastInst(CastInst &CI) {
|
|
Value *Op = CI.getOperand(0);
|
|
if (isa<PointerType>(CI.getType())) {
|
|
if (isa<PointerType>(Op->getType())) {
|
|
// P1 = cast P2 --> <Copy/P1/P2>
|
|
Constraints.push_back(Constraint(Constraint::Copy, getNodeValue(CI),
|
|
getNode(CI.getOperand(0))));
|
|
} else {
|
|
// P1 = cast int --> <Copy/P1/Univ>
|
|
Constraints.push_back(Constraint(Constraint::Copy, getNodeValue(CI),
|
|
&GraphNodes[UniversalSet]));
|
|
}
|
|
} else if (isa<PointerType>(Op->getType())) {
|
|
// int = cast P1 --> <Copy/Univ/P1>
|
|
Constraints.push_back(Constraint(Constraint::Copy,
|
|
&GraphNodes[UniversalSet],
|
|
getNode(CI.getOperand(0))));
|
|
}
|
|
}
|
|
|
|
void Andersens::visitSelectInst(SelectInst &SI) {
|
|
if (isa<PointerType>(SI.getType())) {
|
|
Node *SIN = getNodeValue(SI);
|
|
// P1 = select C, P2, P3 ---> <Copy/P1/P2>, <Copy/P1/P3>
|
|
Constraints.push_back(Constraint(Constraint::Copy, SIN,
|
|
getNode(SI.getOperand(1))));
|
|
Constraints.push_back(Constraint(Constraint::Copy, SIN,
|
|
getNode(SI.getOperand(2))));
|
|
}
|
|
}
|
|
|
|
void Andersens::visitVANext(VANextInst &I) {
|
|
// FIXME: Implement
|
|
assert(0 && "vanext not handled yet!");
|
|
}
|
|
void Andersens::visitVAArg(VAArgInst &I) {
|
|
assert(0 && "vaarg not handled yet!");
|
|
}
|
|
|
|
/// AddConstraintsForCall - Add constraints for a call with actual arguments
|
|
/// specified by CS to the function specified by F. Note that the types of
|
|
/// arguments might not match up in the case where this is an indirect call and
|
|
/// the function pointer has been casted. If this is the case, do something
|
|
/// reasonable.
|
|
void Andersens::AddConstraintsForCall(CallSite CS, Function *F) {
|
|
if (isa<PointerType>(CS.getType())) {
|
|
Node *CSN = getNode(CS.getInstruction());
|
|
if (isa<PointerType>(F->getFunctionType()->getReturnType())) {
|
|
Constraints.push_back(Constraint(Constraint::Copy, CSN,
|
|
getReturnNode(F)));
|
|
} else {
|
|
// If the function returns a non-pointer value, handle this just like we
|
|
// treat a nonpointer cast to pointer.
|
|
Constraints.push_back(Constraint(Constraint::Copy, CSN,
|
|
&GraphNodes[UniversalSet]));
|
|
}
|
|
} else if (isa<PointerType>(F->getFunctionType()->getReturnType())) {
|
|
Constraints.push_back(Constraint(Constraint::Copy,
|
|
&GraphNodes[UniversalSet],
|
|
getReturnNode(F)));
|
|
}
|
|
|
|
Function::aiterator AI = F->abegin(), AE = F->aend();
|
|
CallSite::arg_iterator ArgI = CS.arg_begin(), ArgE = CS.arg_end();
|
|
for (; AI != AE && ArgI != ArgE; ++AI, ++ArgI)
|
|
if (isa<PointerType>(AI->getType())) {
|
|
if (isa<PointerType>((*ArgI)->getType())) {
|
|
// Copy the actual argument into the formal argument.
|
|
Constraints.push_back(Constraint(Constraint::Copy, getNode(AI),
|
|
getNode(*ArgI)));
|
|
} else {
|
|
Constraints.push_back(Constraint(Constraint::Copy, getNode(AI),
|
|
&GraphNodes[UniversalSet]));
|
|
}
|
|
} else if (isa<PointerType>((*ArgI)->getType())) {
|
|
Constraints.push_back(Constraint(Constraint::Copy,
|
|
&GraphNodes[UniversalSet],
|
|
getNode(*ArgI)));
|
|
}
|
|
|
|
// Copy all pointers passed through the varargs section to the varargs node.
|
|
if (F->getFunctionType()->isVarArg())
|
|
for (; ArgI != ArgE; ++ArgI)
|
|
if (isa<PointerType>((*ArgI)->getType()))
|
|
Constraints.push_back(Constraint(Constraint::Copy, getVarargNode(F),
|
|
getNode(*ArgI)));
|
|
// If more arguments are passed in than we track, just drop them on the floor.
|
|
}
|
|
|
|
void Andersens::visitCallSite(CallSite CS) {
|
|
if (isa<PointerType>(CS.getType()))
|
|
getNodeValue(*CS.getInstruction());
|
|
|
|
if (Function *F = CS.getCalledFunction()) {
|
|
AddConstraintsForCall(CS, F);
|
|
} else {
|
|
// We don't handle indirect call sites yet. Keep track of them for when we
|
|
// discover the call graph incrementally.
|
|
IndirectCalls.push_back(CS);
|
|
}
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Constraint Solving Phase
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
/// intersects - Return true if the points-to set of this node intersects
|
|
/// with the points-to set of the specified node.
|
|
bool Andersens::Node::intersects(Node *N) const {
|
|
iterator I1 = begin(), I2 = N->begin(), E1 = end(), E2 = N->end();
|
|
while (I1 != E1 && I2 != E2) {
|
|
if (*I1 == *I2) return true;
|
|
if (*I1 < *I2)
|
|
++I1;
|
|
else
|
|
++I2;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// intersectsIgnoring - Return true if the points-to set of this node
|
|
/// intersects with the points-to set of the specified node on any nodes
|
|
/// except for the specified node to ignore.
|
|
bool Andersens::Node::intersectsIgnoring(Node *N, Node *Ignoring) const {
|
|
iterator I1 = begin(), I2 = N->begin(), E1 = end(), E2 = N->end();
|
|
while (I1 != E1 && I2 != E2) {
|
|
if (*I1 == *I2) {
|
|
if (*I1 != Ignoring) return true;
|
|
++I1; ++I2;
|
|
} else if (*I1 < *I2)
|
|
++I1;
|
|
else
|
|
++I2;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
// Copy constraint: all edges out of the source node get copied to the
|
|
// destination node. This returns true if a change is made.
|
|
bool Andersens::Node::copyFrom(Node *N) {
|
|
// Use a mostly linear-time merge since both of the lists are sorted.
|
|
bool Changed = false;
|
|
iterator I = N->begin(), E = N->end();
|
|
unsigned i = 0;
|
|
while (I != E && i != Pointees.size()) {
|
|
if (Pointees[i] < *I) {
|
|
++i;
|
|
} else if (Pointees[i] == *I) {
|
|
++i; ++I;
|
|
} else {
|
|
// We found a new element to copy over.
|
|
Changed = true;
|
|
Pointees.insert(Pointees.begin()+i, *I);
|
|
++i; ++I;
|
|
}
|
|
}
|
|
|
|
if (I != E) {
|
|
Pointees.insert(Pointees.end(), I, E);
|
|
Changed = true;
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
bool Andersens::Node::loadFrom(Node *N) {
|
|
bool Changed = false;
|
|
for (iterator I = N->begin(), E = N->end(); I != E; ++I)
|
|
Changed |= copyFrom(*I);
|
|
return Changed;
|
|
}
|
|
|
|
bool Andersens::Node::storeThrough(Node *N) {
|
|
bool Changed = false;
|
|
for (iterator I = begin(), E = end(); I != E; ++I)
|
|
Changed |= (*I)->copyFrom(N);
|
|
return Changed;
|
|
}
|
|
|
|
|
|
/// SolveConstraints - This stage iteratively processes the constraints list
|
|
/// propagating constraints (adding edges to the Nodes in the points-to graph)
|
|
/// until a fixed point is reached.
|
|
///
|
|
void Andersens::SolveConstraints() {
|
|
bool Changed = true;
|
|
unsigned Iteration = 0;
|
|
while (Changed) {
|
|
Changed = false;
|
|
++NumIters;
|
|
DEBUG(std::cerr << "Starting iteration #" << Iteration++ << "!\n");
|
|
|
|
// Loop over all of the constraints, applying them in turn.
|
|
for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
|
|
Constraint &C = Constraints[i];
|
|
switch (C.Type) {
|
|
case Constraint::Copy:
|
|
Changed |= C.Dest->copyFrom(C.Src);
|
|
break;
|
|
case Constraint::Load:
|
|
Changed |= C.Dest->loadFrom(C.Src);
|
|
break;
|
|
case Constraint::Store:
|
|
Changed |= C.Dest->storeThrough(C.Src);
|
|
break;
|
|
default:
|
|
assert(0 && "Unknown constraint!");
|
|
}
|
|
}
|
|
|
|
if (Changed) {
|
|
// Check to see if any internal function's addresses have been passed to
|
|
// external functions. If so, we have to assume that their incoming
|
|
// arguments could be anything. If there are any internal functions in
|
|
// the universal node that we don't know about, we must iterate.
|
|
for (Node::iterator I = GraphNodes[UniversalSet].begin(),
|
|
E = GraphNodes[UniversalSet].end(); I != E; ++I)
|
|
if (Function *F = dyn_cast_or_null<Function>((*I)->getValue()))
|
|
if (F->hasInternalLinkage() &&
|
|
EscapingInternalFunctions.insert(F).second) {
|
|
// We found a function that is just now escaping. Mark it as if it
|
|
// didn't have internal linkage.
|
|
AddConstraintsForNonInternalLinkage(F);
|
|
DEBUG(std::cerr << "Found escaping internal function: "
|
|
<< F->getName() << "\n");
|
|
++NumEscapingFunctions;
|
|
}
|
|
|
|
// Check to see if we have discovered any new callees of the indirect call
|
|
// sites. If so, add constraints to the analysis.
|
|
for (unsigned i = 0, e = IndirectCalls.size(); i != e; ++i) {
|
|
CallSite CS = IndirectCalls[i];
|
|
std::vector<Function*> &KnownCallees = IndirectCallees[CS];
|
|
Node *CN = getNode(CS.getCalledValue());
|
|
|
|
for (Node::iterator NI = CN->begin(), E = CN->end(); NI != E; ++NI)
|
|
if (Function *F = dyn_cast_or_null<Function>((*NI)->getValue())) {
|
|
std::vector<Function*>::iterator IP =
|
|
std::lower_bound(KnownCallees.begin(), KnownCallees.end(), F);
|
|
if (IP == KnownCallees.end() || *IP != F) {
|
|
// Add the constraints for the call now.
|
|
AddConstraintsForCall(CS, F);
|
|
DEBUG(std::cerr << "Found actual callee '"
|
|
<< F->getName() << "' for call: "
|
|
<< *CS.getInstruction() << "\n");
|
|
++NumIndirectCallees;
|
|
KnownCallees.insert(IP, F);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// Debugging Output
|
|
//===----------------------------------------------------------------------===//
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void Andersens::PrintNode(Node *N) {
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if (N == &GraphNodes[UniversalSet]) {
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std::cerr << "<universal>";
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return;
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} else if (N == &GraphNodes[NullPtr]) {
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std::cerr << "<nullptr>";
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return;
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} else if (N == &GraphNodes[NullObject]) {
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std::cerr << "<null>";
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return;
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}
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assert(N->getValue() != 0 && "Never set node label!");
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Value *V = N->getValue();
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if (Function *F = dyn_cast<Function>(V)) {
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if (isa<PointerType>(F->getFunctionType()->getReturnType()) &&
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N == getReturnNode(F)) {
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std::cerr << F->getName() << ":retval";
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return;
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} else if (F->getFunctionType()->isVarArg() && N == getVarargNode(F)) {
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std::cerr << F->getName() << ":vararg";
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return;
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}
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}
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if (Instruction *I = dyn_cast<Instruction>(V))
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std::cerr << I->getParent()->getParent()->getName() << ":";
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else if (Argument *Arg = dyn_cast<Argument>(V))
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std::cerr << Arg->getParent()->getName() << ":";
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if (V->hasName())
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std::cerr << V->getName();
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else
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std::cerr << "(unnamed)";
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if (isa<GlobalValue>(V) || isa<AllocationInst>(V))
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if (N == getObject(V))
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std::cerr << "<mem>";
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}
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void Andersens::PrintConstraints() {
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std::cerr << "Constraints:\n";
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for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
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std::cerr << " #" << i << ": ";
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Constraint &C = Constraints[i];
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if (C.Type == Constraint::Store)
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std::cerr << "*";
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PrintNode(C.Dest);
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std::cerr << " = ";
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if (C.Type == Constraint::Load)
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std::cerr << "*";
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PrintNode(C.Src);
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std::cerr << "\n";
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}
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}
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void Andersens::PrintPointsToGraph() {
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std::cerr << "Points-to graph:\n";
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for (unsigned i = 0, e = GraphNodes.size(); i != e; ++i) {
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Node *N = &GraphNodes[i];
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std::cerr << "[" << (N->end() - N->begin()) << "] ";
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PrintNode(N);
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std::cerr << "\t--> ";
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for (Node::iterator I = N->begin(), E = N->end(); I != E; ++I) {
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if (I != N->begin()) std::cerr << ", ";
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PrintNode(*I);
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}
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std::cerr << "\n";
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}
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}
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