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231 lines
8.2 KiB
C++
231 lines
8.2 KiB
C++
//===- Steensgaard.cpp - Context Insensitive Alias Analysis ---------------===//
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//
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// This pass uses the data structure graphs to implement a simple context
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// insensitive alias analysis. It does this by computing the local analysis
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// graphs for all of the functions, then merging them together into a single big
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// graph without cloning.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/DataStructure.h"
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#include "llvm/Analysis/DSGraph.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Module.h"
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#include "Support/Debug.h"
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namespace {
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class Steens : public Pass, public AliasAnalysis {
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DSGraph *ResultGraph;
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DSGraph *GlobalsGraph; // FIXME: Eliminate globals graph stuff from DNE
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public:
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Steens() : ResultGraph(0), GlobalsGraph(0) {}
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~Steens() {
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releaseMyMemory();
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assert(ResultGraph == 0 && "releaseMemory not called?");
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}
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//------------------------------------------------
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// Implement the Pass API
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//
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// run - Build up the result graph, representing the pointer graph for the
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// program.
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//
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bool run(Module &M);
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virtual void releaseMyMemory() { delete ResultGraph; ResultGraph = 0; }
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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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AU.addRequired<LocalDataStructures>(); // Uses local dsgraph
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AU.addRequired<AliasAnalysis>(); // Chains to another AA impl...
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}
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// print - Implement the Pass::print method...
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void print(std::ostream &O, const Module *M) const {
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assert(ResultGraph && "Result graph has not yet been computed!");
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ResultGraph->writeGraphToFile(O, "steensgaards");
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}
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//------------------------------------------------
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// Implement the AliasAnalysis API
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//
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// alias - This is the only method here that does anything interesting...
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AliasResult alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size);
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private:
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void ResolveFunctionCall(Function *F, const DSCallSite &Call,
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DSNodeHandle &RetVal);
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};
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// Register the pass...
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RegisterOpt<Steens> X("steens-aa",
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"Steensgaard's alias analysis (DSGraph based)");
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// Register as an implementation of AliasAnalysis
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RegisterAnalysisGroup<AliasAnalysis, Steens> Y;
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}
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/// ResolveFunctionCall - Resolve the actual arguments of a call to function F
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/// with the specified call site descriptor. This function links the arguments
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/// and the return value for the call site context-insensitively.
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///
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void Steens::ResolveFunctionCall(Function *F, const DSCallSite &Call,
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DSNodeHandle &RetVal) {
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assert(ResultGraph != 0 && "Result graph not allocated!");
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DSGraph::ScalarMapTy &ValMap = ResultGraph->getScalarMap();
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// Handle the return value of the function...
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if (Call.getRetVal().getNode() && RetVal.getNode())
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RetVal.mergeWith(Call.getRetVal());
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// Loop over all pointer arguments, resolving them to their provided pointers
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unsigned PtrArgIdx = 0;
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for (Function::aiterator AI = F->abegin(), AE = F->aend();
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AI != AE && PtrArgIdx < Call.getNumPtrArgs(); ++AI) {
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DSGraph::ScalarMapTy::iterator I = ValMap.find(AI);
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if (I != ValMap.end()) // If its a pointer argument...
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I->second.mergeWith(Call.getPtrArg(PtrArgIdx++));
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}
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}
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/// run - Build up the result graph, representing the pointer graph for the
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/// program.
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///
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bool Steens::run(Module &M) {
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InitializeAliasAnalysis(this);
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assert(ResultGraph == 0 && "Result graph already allocated!");
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LocalDataStructures &LDS = getAnalysis<LocalDataStructures>();
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// Create a new, empty, graph...
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ResultGraph = new DSGraph();
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GlobalsGraph = new DSGraph();
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ResultGraph->setGlobalsGraph(GlobalsGraph);
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ResultGraph->setPrintAuxCalls();
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// RetValMap - Keep track of the return values for all functions that return
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// valid pointers.
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//
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DSGraph::ReturnNodesTy RetValMap;
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// Loop over the rest of the module, merging graphs for non-external functions
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// into this graph.
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//
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unsigned Count = 0;
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for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
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if (!I->isExternal()) {
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DSGraph::ScalarMapTy ValMap;
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{ // Scope to free NodeMap memory ASAP
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DSGraph::NodeMapTy NodeMap;
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const DSGraph &FDSG = LDS.getDSGraph(*I);
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ResultGraph->cloneInto(FDSG, ValMap, RetValMap, NodeMap);
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}
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// Incorporate the inlined Function's ScalarMap into the global
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// ScalarMap...
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DSGraph::ScalarMapTy &GVM = ResultGraph->getScalarMap();
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for (DSGraph::ScalarMapTy::iterator I = ValMap.begin(),
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E = ValMap.end(); I != E; ++I)
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GVM[I->first].mergeWith(I->second);
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if ((++Count & 1) == 0) // Prune nodes out every other time...
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ResultGraph->removeTriviallyDeadNodes();
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}
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// FIXME: Must recalculate and use the Incomplete markers!!
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// Now that we have all of the graphs inlined, we can go about eliminating
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// call nodes...
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//
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std::vector<DSCallSite> &Calls =
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ResultGraph->getAuxFunctionCalls();
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assert(Calls.empty() && "Aux call list is already in use??");
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// Start with a copy of the original call sites...
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Calls = ResultGraph->getFunctionCalls();
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for (unsigned i = 0; i != Calls.size(); ) {
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DSCallSite &CurCall = Calls[i];
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// Loop over the called functions, eliminating as many as possible...
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std::vector<GlobalValue*> CallTargets;
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if (CurCall.isDirectCall())
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CallTargets.push_back(CurCall.getCalleeFunc());
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else
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CallTargets = CurCall.getCalleeNode()->getGlobals();
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for (unsigned c = 0; c != CallTargets.size(); ) {
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// If we can eliminate this function call, do so!
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bool Eliminated = false;
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if (Function *F = dyn_cast<Function>(CallTargets[c]))
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if (!F->isExternal()) {
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ResolveFunctionCall(F, CurCall, RetValMap[F]);
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Eliminated = true;
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}
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if (Eliminated) {
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CallTargets[c] = CallTargets.back();
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CallTargets.pop_back();
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} else
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++c; // Cannot eliminate this call, skip over it...
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}
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if (CallTargets.empty()) { // Eliminated all calls?
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CurCall = Calls.back(); // Remove entry
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Calls.pop_back();
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} else
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++i; // Skip this call site...
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}
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RetValMap.clear();
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// Update the "incomplete" markers on the nodes, ignoring unknownness due to
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// incoming arguments...
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ResultGraph->maskIncompleteMarkers();
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ResultGraph->markIncompleteNodes(DSGraph::IgnoreFormalArgs);
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// Remove any nodes that are dead after all of the merging we have done...
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// FIXME: We should be able to disable the globals graph for steens!
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ResultGraph->removeDeadNodes(DSGraph::KeepUnreachableGlobals);
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DEBUG(print(std::cerr, &M));
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return false;
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}
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// alias - This is the only method here that does anything interesting...
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AliasAnalysis::AliasResult Steens::alias(const Value *V1, unsigned V1Size,
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const Value *V2, unsigned V2Size) {
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// FIXME: HANDLE Size argument!
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assert(ResultGraph && "Result graph has not been computed yet!");
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DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();
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DSGraph::ScalarMapTy::iterator I = GSM.find(const_cast<Value*>(V1));
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if (I != GSM.end() && I->second.getNode()) {
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DSNodeHandle &V1H = I->second;
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DSGraph::ScalarMapTy::iterator J=GSM.find(const_cast<Value*>(V2));
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if (J != GSM.end() && J->second.getNode()) {
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DSNodeHandle &V2H = J->second;
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// If the two pointers point to different data structure graph nodes, they
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// cannot alias!
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if (V1H.getNode() != V2H.getNode()) // FIXME: Handle incompleteness!
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return NoAlias;
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// FIXME: If the two pointers point to the same node, and the offsets are
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// different, and the LinkIndex vector doesn't alias the section, then the
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// two pointers do not alias. We need access size information for the two
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// accesses though!
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//
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}
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}
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// If we cannot determine alias properties based on our graph, fall back on
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// some other AA implementation.
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//
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return getAnalysis<AliasAnalysis>().alias(V1, V1Size, V2, V2Size);
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}
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