1 //===- Steensgaard.cpp - Context Insensitive Alias Analysis ---------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass uses the data structure graphs to implement a simple context
11 // insensitive alias analysis. It does this by computing the local analysis
12 // graphs for all of the functions, then merging them together into a single big
13 // graph without cloning.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Analysis/DataStructure/DataStructure.h"
18 #include "llvm/Analysis/DataStructure/DSGraph.h"
19 #include "llvm/Analysis/AliasAnalysis.h"
20 #include "llvm/Analysis/Passes.h"
21 #include "llvm/Module.h"
22 #include "llvm/Support/Debug.h"
26 class Steens : public ModulePass, public AliasAnalysis {
28 DSGraph *GlobalsGraph; // FIXME: Eliminate globals graph stuff from DNE
30 Steens() : ResultGraph(0), GlobalsGraph(0) {}
33 assert(ResultGraph == 0 && "releaseMemory not called?");
36 //------------------------------------------------
37 // Implement the Pass API
40 // run - Build up the result graph, representing the pointer graph for the
43 bool runOnModule(Module &M);
45 virtual void releaseMyMemory() { delete ResultGraph; ResultGraph = 0; }
47 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
48 AliasAnalysis::getAnalysisUsage(AU);
49 AU.setPreservesAll(); // Does not transform code...
50 AU.addRequired<LocalDataStructures>(); // Uses local dsgraph
53 // print - Implement the Pass::print method...
54 void print(std::ostream &O, const Module *M) const {
55 assert(ResultGraph && "Result graph has not yet been computed!");
56 ResultGraph->writeGraphToFile(O, "steensgaards");
59 //------------------------------------------------
60 // Implement the AliasAnalysis API
63 // alias - This is the only method here that does anything interesting...
64 AliasResult alias(const Value *V1, unsigned V1Size,
65 const Value *V2, unsigned V2Size);
68 void ResolveFunctionCall(Function *F, const DSCallSite &Call,
69 DSNodeHandle &RetVal);
72 // Register the pass...
73 RegisterOpt<Steens> X("steens-aa",
74 "Steensgaard's alias analysis (DSGraph based)");
76 // Register as an implementation of AliasAnalysis
77 RegisterAnalysisGroup<AliasAnalysis, Steens> Y;
80 ModulePass *llvm::createSteensgaardPass() { return new Steens(); }
82 /// ResolveFunctionCall - Resolve the actual arguments of a call to function F
83 /// with the specified call site descriptor. This function links the arguments
84 /// and the return value for the call site context-insensitively.
86 void Steens::ResolveFunctionCall(Function *F, const DSCallSite &Call,
87 DSNodeHandle &RetVal) {
88 assert(ResultGraph != 0 && "Result graph not allocated!");
89 DSGraph::ScalarMapTy &ValMap = ResultGraph->getScalarMap();
91 // Handle the return value of the function...
92 if (Call.getRetVal().getNode() && RetVal.getNode())
93 RetVal.mergeWith(Call.getRetVal());
95 // Loop over all pointer arguments, resolving them to their provided pointers
96 unsigned PtrArgIdx = 0;
97 for (Function::aiterator AI = F->abegin(), AE = F->aend();
98 AI != AE && PtrArgIdx < Call.getNumPtrArgs(); ++AI) {
99 DSGraph::ScalarMapTy::iterator I = ValMap.find(AI);
100 if (I != ValMap.end()) // If its a pointer argument...
101 I->second.mergeWith(Call.getPtrArg(PtrArgIdx++));
106 /// run - Build up the result graph, representing the pointer graph for the
109 bool Steens::runOnModule(Module &M) {
110 InitializeAliasAnalysis(this);
111 assert(ResultGraph == 0 && "Result graph already allocated!");
112 LocalDataStructures &LDS = getAnalysis<LocalDataStructures>();
114 // Create a new, empty, graph...
115 ResultGraph = new DSGraph(getTargetData());
116 GlobalsGraph = new DSGraph(getTargetData());
117 ResultGraph->setGlobalsGraph(GlobalsGraph);
118 ResultGraph->setPrintAuxCalls();
120 // RetValMap - Keep track of the return values for all functions that return
123 DSGraph::ReturnNodesTy RetValMap;
125 // Loop over the rest of the module, merging graphs for non-external functions
129 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
130 if (!I->isExternal()) {
131 DSGraph::ScalarMapTy ValMap;
132 { // Scope to free NodeMap memory ASAP
133 DSGraph::NodeMapTy NodeMap;
134 const DSGraph &FDSG = LDS.getDSGraph(*I);
135 ResultGraph->cloneInto(FDSG, ValMap, RetValMap, NodeMap,
136 DSGraph::UpdateInlinedGlobals);
139 // Incorporate the inlined Function's ScalarMap into the global
141 DSGraph::ScalarMapTy &GVM = ResultGraph->getScalarMap();
142 for (DSGraph::ScalarMapTy::iterator I = ValMap.begin(),
143 E = ValMap.end(); I != E; ++I)
144 GVM[I->first].mergeWith(I->second);
146 if ((++Count & 1) == 0) // Prune nodes out every other time...
147 ResultGraph->removeTriviallyDeadNodes();
150 // FIXME: Must recalculate and use the Incomplete markers!!
152 // Now that we have all of the graphs inlined, we can go about eliminating
155 std::list<DSCallSite> &Calls = ResultGraph->getAuxFunctionCalls();
156 assert(Calls.empty() && "Aux call list is already in use??");
158 // Start with a copy of the original call sites.
159 Calls = ResultGraph->getFunctionCalls();
161 for (std::list<DSCallSite>::iterator CI = Calls.begin(), E = Calls.end();
163 DSCallSite &CurCall = *CI++;
165 // Loop over the called functions, eliminating as many as possible...
166 std::vector<GlobalValue*> CallTargets;
167 if (CurCall.isDirectCall())
168 CallTargets.push_back(CurCall.getCalleeFunc());
170 CallTargets = CurCall.getCalleeNode()->getGlobals();
172 for (unsigned c = 0; c != CallTargets.size(); ) {
173 // If we can eliminate this function call, do so!
174 bool Eliminated = false;
175 if (Function *F = dyn_cast<Function>(CallTargets[c]))
176 if (!F->isExternal()) {
177 ResolveFunctionCall(F, CurCall, RetValMap[F]);
181 CallTargets[c] = CallTargets.back();
182 CallTargets.pop_back();
184 ++c; // Cannot eliminate this call, skip over it...
187 if (CallTargets.empty()) { // Eliminated all calls?
188 std::list<DSCallSite>::iterator I = CI;
189 Calls.erase(--I); // Remove entry
195 // Update the "incomplete" markers on the nodes, ignoring unknownness due to
196 // incoming arguments...
197 ResultGraph->maskIncompleteMarkers();
198 ResultGraph->markIncompleteNodes(DSGraph::IgnoreFormalArgs);
200 // Remove any nodes that are dead after all of the merging we have done...
201 // FIXME: We should be able to disable the globals graph for steens!
202 ResultGraph->removeDeadNodes(DSGraph::KeepUnreachableGlobals);
204 DEBUG(print(std::cerr, &M));
208 // alias - This is the only method here that does anything interesting...
209 AliasAnalysis::AliasResult Steens::alias(const Value *V1, unsigned V1Size,
210 const Value *V2, unsigned V2Size) {
211 // FIXME: HANDLE Size argument!
212 assert(ResultGraph && "Result graph has not been computed yet!");
214 DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();
216 DSGraph::ScalarMapTy::iterator I = GSM.find(const_cast<Value*>(V1));
217 if (I != GSM.end() && I->second.getNode()) {
218 DSNodeHandle &V1H = I->second;
219 DSGraph::ScalarMapTy::iterator J=GSM.find(const_cast<Value*>(V2));
220 if (J != GSM.end() && J->second.getNode()) {
221 DSNodeHandle &V2H = J->second;
222 // If the two pointers point to different data structure graph nodes, they
224 if (V1H.getNode() != V2H.getNode()) // FIXME: Handle incompleteness!
227 // FIXME: If the two pointers point to the same node, and the offsets are
228 // different, and the LinkIndex vector doesn't alias the section, then the
229 // two pointers do not alias. We need access size information for the two
235 // If we cannot determine alias properties based on our graph, fall back on
236 // some other AA implementation.
238 return AliasAnalysis::alias(V1, V1Size, V2, V2Size);