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TopDownClosure.cpp

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00001 //===- TopDownClosure.cpp - Compute the top-down interprocedure closure ---===//
00002 // 
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 // 
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file implements the TDDataStructures class, which represents the
00011 // Top-down Interprocedural closure of the data structure graph over the
00012 // program.  This is useful (but not strictly necessary?) for applications
00013 // like pointer analysis.
00014 //
00015 //===----------------------------------------------------------------------===//
00016 
00017 #include "llvm/Analysis/DataStructure/DataStructure.h"
00018 #include "llvm/Module.h"
00019 #include "llvm/DerivedTypes.h"
00020 #include "llvm/Analysis/DataStructure/DSGraph.h"
00021 #include "llvm/Support/Debug.h"
00022 #include "llvm/ADT/Statistic.h"
00023 using namespace llvm;
00024 
00025 namespace {
00026   RegisterAnalysis<TDDataStructures>   // Register the pass
00027   Y("tddatastructure", "Top-down Data Structure Analysis");
00028 
00029   Statistic<> NumTDInlines("tddatastructures", "Number of graphs inlined");
00030 }
00031 
00032 void TDDataStructures::markReachableFunctionsExternallyAccessible(DSNode *N,
00033                                                    hash_set<DSNode*> &Visited) {
00034   if (!N || Visited.count(N)) return;
00035   Visited.insert(N);
00036 
00037   for (unsigned i = 0, e = N->getNumLinks(); i != e; ++i) {
00038     DSNodeHandle &NH = N->getLink(i*N->getPointerSize());
00039     if (DSNode *NN = NH.getNode()) {
00040       const std::vector<GlobalValue*> &Globals = NN->getGlobals();
00041       for (unsigned G = 0, e = Globals.size(); G != e; ++G)
00042         if (Function *F = dyn_cast<Function>(Globals[G]))
00043           ArgsRemainIncomplete.insert(F);
00044 
00045       markReachableFunctionsExternallyAccessible(NN, Visited);
00046     }
00047   }
00048 }
00049 
00050 
00051 // run - Calculate the top down data structure graphs for each function in the
00052 // program.
00053 //
00054 bool TDDataStructures::runOnModule(Module &M) {
00055   BUDataStructures &BU = getAnalysis<BUDataStructures>();
00056   GlobalsGraph = new DSGraph(BU.getGlobalsGraph());
00057   GlobalsGraph->setPrintAuxCalls();
00058 
00059   // Figure out which functions must not mark their arguments complete because
00060   // they are accessible outside this compilation unit.  Currently, these
00061   // arguments are functions which are reachable by global variables in the
00062   // globals graph.
00063   const DSScalarMap &GGSM = GlobalsGraph->getScalarMap();
00064   hash_set<DSNode*> Visited;
00065   for (DSScalarMap::global_iterator I=GGSM.global_begin(), E=GGSM.global_end();
00066        I != E; ++I)
00067     markReachableFunctionsExternallyAccessible(GGSM.find(*I)->second.getNode(),
00068                                                Visited);
00069 
00070   // Loop over unresolved call nodes.  Any functions passed into (but not
00071   // returned!) from unresolvable call nodes may be invoked outside of the
00072   // current module.
00073   const std::vector<DSCallSite> &Calls = GlobalsGraph->getAuxFunctionCalls();
00074   for (unsigned i = 0, e = Calls.size(); i != e; ++i) {
00075     const DSCallSite &CS = Calls[i];
00076     for (unsigned arg = 0, e = CS.getNumPtrArgs(); arg != e; ++arg)
00077       markReachableFunctionsExternallyAccessible(CS.getPtrArg(arg).getNode(),
00078                                                  Visited);
00079   }
00080   Visited.clear();
00081 
00082   // Functions without internal linkage also have unknown incoming arguments!
00083   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
00084     if (!I->isExternal() && !I->hasInternalLinkage())
00085       ArgsRemainIncomplete.insert(I);
00086 
00087   // We want to traverse the call graph in reverse post-order.  To do this, we
00088   // calculate a post-order traversal, then reverse it.
00089   hash_set<DSGraph*> VisitedGraph;
00090   std::vector<DSGraph*> PostOrder;
00091   const BUDataStructures::ActualCalleesTy &ActualCallees = 
00092     getAnalysis<BUDataStructures>().getActualCallees();
00093 
00094   // Calculate top-down from main...
00095   if (Function *F = M.getMainFunction())
00096     ComputePostOrder(*F, VisitedGraph, PostOrder, ActualCallees);
00097 
00098   // Next calculate the graphs for each unreachable function...
00099   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
00100     ComputePostOrder(*I, VisitedGraph, PostOrder, ActualCallees);
00101 
00102   VisitedGraph.clear();   // Release memory!
00103 
00104   // Visit each of the graphs in reverse post-order now!
00105   while (!PostOrder.empty()) {
00106     inlineGraphIntoCallees(*PostOrder.back());
00107     PostOrder.pop_back();
00108   }
00109 
00110   ArgsRemainIncomplete.clear();
00111   GlobalsGraph->removeTriviallyDeadNodes();
00112 
00113   return false;
00114 }
00115 
00116 
00117 DSGraph &TDDataStructures::getOrCreateDSGraph(Function &F) {
00118   DSGraph *&G = DSInfo[&F];
00119   if (G == 0) { // Not created yet?  Clone BU graph...
00120     G = new DSGraph(getAnalysis<BUDataStructures>().getDSGraph(F));
00121     G->getAuxFunctionCalls().clear();
00122     G->setPrintAuxCalls();
00123     G->setGlobalsGraph(GlobalsGraph);
00124   }
00125   return *G;
00126 }
00127 
00128 
00129 void TDDataStructures::ComputePostOrder(Function &F,hash_set<DSGraph*> &Visited,
00130                                         std::vector<DSGraph*> &PostOrder,
00131                       const BUDataStructures::ActualCalleesTy &ActualCallees) {
00132   if (F.isExternal()) return;
00133   DSGraph &G = getOrCreateDSGraph(F);
00134   if (Visited.count(&G)) return;
00135   Visited.insert(&G);
00136   
00137   // Recursively traverse all of the callee graphs.
00138   const std::vector<DSCallSite> &FunctionCalls = G.getFunctionCalls();
00139 
00140   for (unsigned i = 0, e = FunctionCalls.size(); i != e; ++i) {
00141     Instruction *CallI = FunctionCalls[i].getCallSite().getInstruction();
00142     std::pair<BUDataStructures::ActualCalleesTy::const_iterator,
00143       BUDataStructures::ActualCalleesTy::const_iterator>
00144          IP = ActualCallees.equal_range(CallI);
00145 
00146     for (BUDataStructures::ActualCalleesTy::const_iterator I = IP.first;
00147          I != IP.second; ++I)
00148       ComputePostOrder(*I->second, Visited, PostOrder, ActualCallees);
00149   }
00150 
00151   PostOrder.push_back(&G);
00152 }
00153 
00154 
00155 
00156 
00157 
00158 // releaseMemory - If the pass pipeline is done with this pass, we can release
00159 // our memory... here...
00160 //
00161 // FIXME: This should be releaseMemory and will work fine, except that LoadVN
00162 // has no way to extend the lifetime of the pass, which screws up ds-aa.
00163 //
00164 void TDDataStructures::releaseMyMemory() {
00165   for (hash_map<Function*, DSGraph*>::iterator I = DSInfo.begin(),
00166          E = DSInfo.end(); I != E; ++I) {
00167     I->second->getReturnNodes().erase(I->first);
00168     if (I->second->getReturnNodes().empty())
00169       delete I->second;
00170   }
00171 
00172   // Empty map so next time memory is released, data structures are not
00173   // re-deleted.
00174   DSInfo.clear();
00175   delete GlobalsGraph;
00176   GlobalsGraph = 0;
00177 }
00178 
00179 void TDDataStructures::inlineGraphIntoCallees(DSGraph &Graph) {
00180   // Recompute the Incomplete markers and eliminate unreachable nodes.
00181   Graph.maskIncompleteMarkers();
00182 
00183   // If any of the functions has incomplete incoming arguments, don't mark any
00184   // of them as complete.
00185   bool HasIncompleteArgs = false;
00186   const DSGraph::ReturnNodesTy &GraphReturnNodes = Graph.getReturnNodes();
00187   for (DSGraph::ReturnNodesTy::const_iterator I = GraphReturnNodes.begin(),
00188          E = GraphReturnNodes.end(); I != E; ++I)
00189     if (ArgsRemainIncomplete.count(I->first)) {
00190       HasIncompleteArgs = true;
00191       break;
00192     }
00193 
00194   // Now fold in the necessary globals from the GlobalsGraph.  A global G
00195   // must be folded in if it exists in the current graph (i.e., is not dead)
00196   // and it was not inlined from any of my callers.  If it was inlined from
00197   // a caller, it would have been fully consistent with the GlobalsGraph
00198   // in the caller so folding in is not necessary.  Otherwise, this node came
00199   // solely from this function's BU graph and so has to be made consistent.
00200   // 
00201   Graph.updateFromGlobalGraph();
00202 
00203   // Recompute the Incomplete markers.  Depends on whether args are complete
00204   unsigned Flags
00205     = HasIncompleteArgs ? DSGraph::MarkFormalArgs : DSGraph::IgnoreFormalArgs;
00206   Graph.markIncompleteNodes(Flags | DSGraph::IgnoreGlobals);
00207 
00208   // Delete dead nodes.  Treat globals that are unreachable as dead also.
00209   Graph.removeDeadNodes(DSGraph::RemoveUnreachableGlobals);
00210 
00211   // We are done with computing the current TD Graph! Now move on to
00212   // inlining the current graph into the graphs for its callees, if any.
00213   // 
00214   const std::vector<DSCallSite> &FunctionCalls = Graph.getFunctionCalls();
00215   if (FunctionCalls.empty()) {
00216     DEBUG(std::cerr << "  [TD] No callees for: " << Graph.getFunctionNames()
00217                     << "\n");
00218     return;
00219   }
00220 
00221   // Now that we have information about all of the callees, propagate the
00222   // current graph into the callees.  Clone only the reachable subgraph at
00223   // each call-site, not the entire graph (even though the entire graph
00224   // would be cloned only once, this should still be better on average).
00225   //
00226   DEBUG(std::cerr << "  [TD] Inlining '" << Graph.getFunctionNames() <<"' into "
00227                   << FunctionCalls.size() << " call nodes.\n");
00228 
00229   const BUDataStructures::ActualCalleesTy &ActualCallees =
00230     getAnalysis<BUDataStructures>().getActualCallees();
00231 
00232   // Loop over all the call sites and all the callees at each call site.  Build
00233   // a mapping from called DSGraph's to the call sites in this function that
00234   // invoke them.  This is useful because we can be more efficient if there are
00235   // multiple call sites to the callees in the graph from this caller.
00236   std::multimap<DSGraph*, std::pair<Function*, const DSCallSite*> > CallSites;
00237 
00238   for (unsigned i = 0, e = FunctionCalls.size(); i != e; ++i) {
00239     Instruction *CallI = FunctionCalls[i].getCallSite().getInstruction();
00240     // For each function in the invoked function list at this call site...
00241     std::pair<BUDataStructures::ActualCalleesTy::const_iterator,
00242       BUDataStructures::ActualCalleesTy::const_iterator>
00243           IP = ActualCallees.equal_range(CallI);
00244     // Loop over each actual callee at this call site
00245     for (BUDataStructures::ActualCalleesTy::const_iterator I = IP.first;
00246          I != IP.second; ++I) {
00247       DSGraph& CalleeGraph = getDSGraph(*I->second);
00248       assert(&CalleeGraph != &Graph && "TD need not inline graph into self!");
00249 
00250       CallSites.insert(std::make_pair(&CalleeGraph,
00251                            std::make_pair(I->second, &FunctionCalls[i])));
00252     }
00253   }
00254 
00255   // Now that we built the mapping, actually perform the inlining a callee graph
00256   // at a time.
00257   std::multimap<DSGraph*,std::pair<Function*,const DSCallSite*> >::iterator CSI;
00258   for (CSI = CallSites.begin(); CSI != CallSites.end(); ) {
00259     DSGraph &CalleeGraph = *CSI->first;
00260     // Iterate through all of the call sites of this graph, cloning and merging
00261     // any nodes required by the call.
00262     ReachabilityCloner RC(CalleeGraph, Graph, DSGraph::StripModRefBits);
00263 
00264     // Clone over any global nodes that appear in both graphs.
00265     for (DSScalarMap::global_iterator
00266            SI = CalleeGraph.getScalarMap().global_begin(),
00267            SE = CalleeGraph.getScalarMap().global_end(); SI != SE; ++SI) {
00268       DSScalarMap::const_iterator GI = Graph.getScalarMap().find(*SI);
00269       if (GI != Graph.getScalarMap().end())
00270         RC.merge(CalleeGraph.getNodeForValue(*SI), GI->second);
00271     }
00272 
00273     // Loop over all of the distinct call sites in the caller of the callee.
00274     for (; CSI != CallSites.end() && CSI->first == &CalleeGraph; ++CSI) {
00275       Function &CF = *CSI->second.first;
00276       const DSCallSite &CS = *CSI->second.second;
00277       DEBUG(std::cerr << "     [TD] Resolving arguments for callee graph '"
00278             << CalleeGraph.getFunctionNames()
00279             << "': " << CF.getFunctionType()->getNumParams()
00280             << " args\n          at call site (DSCallSite*) 0x" << &CS << "\n");
00281       
00282       // Get the formal argument and return nodes for the called function and
00283       // merge them with the cloned subgraph.
00284       RC.mergeCallSite(CalleeGraph.getCallSiteForArguments(CF), CS);
00285       ++NumTDInlines;
00286     }
00287   }
00288 
00289   DEBUG(std::cerr << "  [TD] Done inlining into callees for: "
00290         << Graph.getFunctionNames() << " [" << Graph.getGraphSize() << "+"
00291         << Graph.getFunctionCalls().size() << "]\n");
00292 }