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BottomUpClosure.cpp

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00001 //===- BottomUpClosure.cpp - Compute bottom-up interprocedural 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 BUDataStructures class, which represents the
00011 // Bottom-Up Interprocedural closure of the data structure graph over the
00012 // program.  This is useful for applications like pool allocation, but **not**
00013 // applications like alias analysis.
00014 //
00015 //===----------------------------------------------------------------------===//
00016 
00017 #include "llvm/Analysis/DataStructure/DataStructure.h"
00018 #include "llvm/Module.h"
00019 #include "llvm/ADT/Statistic.h"
00020 #include "llvm/Support/Debug.h"
00021 #include "DSCallSiteIterator.h"
00022 using namespace llvm;
00023 
00024 namespace {
00025   Statistic<> MaxSCC("budatastructure", "Maximum SCC Size in Call Graph");
00026   Statistic<> NumBUInlines("budatastructures", "Number of graphs inlined");
00027   Statistic<> NumCallEdges("budatastructures", "Number of 'actual' call edges");
00028   
00029   RegisterAnalysis<BUDataStructures>
00030   X("budatastructure", "Bottom-up Data Structure Analysis");
00031 }
00032 
00033 using namespace DS;
00034 
00035 // run - Calculate the bottom up data structure graphs for each function in the
00036 // program.
00037 //
00038 bool BUDataStructures::runOnModule(Module &M) {
00039   LocalDataStructures &LocalDSA = getAnalysis<LocalDataStructures>();
00040   GlobalsGraph = new DSGraph(LocalDSA.getGlobalsGraph());
00041   GlobalsGraph->setPrintAuxCalls();
00042 
00043   Function *MainFunc = M.getMainFunction();
00044   if (MainFunc)
00045     calculateReachableGraphs(MainFunc);
00046 
00047   // Calculate the graphs for any functions that are unreachable from main...
00048   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
00049     if (!I->isExternal() && !DSInfo.count(I)) {
00050 #ifndef NDEBUG
00051       if (MainFunc)
00052         std::cerr << "*** Function unreachable from main: "
00053                   << I->getName() << "\n";
00054 #endif
00055       calculateReachableGraphs(I);    // Calculate all graphs...
00056     }
00057 
00058   NumCallEdges += ActualCallees.size();
00059 
00060   // At the end of the bottom-up pass, the globals graph becomes complete.
00061   // FIXME: This is not the right way to do this, but it is sorta better than
00062   // nothing!  In particular, externally visible globals and unresolvable call
00063   // nodes at the end of the BU phase should make things that they point to
00064   // incomplete in the globals graph.
00065   // 
00066   GlobalsGraph->removeTriviallyDeadNodes();
00067   GlobalsGraph->maskIncompleteMarkers();
00068   return false;
00069 }
00070 
00071 void BUDataStructures::calculateReachableGraphs(Function *F) {
00072   std::vector<Function*> Stack;
00073   hash_map<Function*, unsigned> ValMap;
00074   unsigned NextID = 1;
00075   calculateGraphs(F, Stack, NextID, ValMap);
00076 }
00077 
00078 DSGraph &BUDataStructures::getOrCreateGraph(Function *F) {
00079   // Has the graph already been created?
00080   DSGraph *&Graph = DSInfo[F];
00081   if (Graph) return *Graph;
00082 
00083   // Copy the local version into DSInfo...
00084   Graph = new DSGraph(getAnalysis<LocalDataStructures>().getDSGraph(*F));
00085 
00086   Graph->setGlobalsGraph(GlobalsGraph);
00087   Graph->setPrintAuxCalls();
00088 
00089   // Start with a copy of the original call sites...
00090   Graph->getAuxFunctionCalls() = Graph->getFunctionCalls();
00091   return *Graph;
00092 }
00093 
00094 unsigned BUDataStructures::calculateGraphs(Function *F,
00095                                            std::vector<Function*> &Stack,
00096                                            unsigned &NextID, 
00097                                      hash_map<Function*, unsigned> &ValMap) {
00098   assert(!ValMap.count(F) && "Shouldn't revisit functions!");
00099   unsigned Min = NextID++, MyID = Min;
00100   ValMap[F] = Min;
00101   Stack.push_back(F);
00102 
00103   // FIXME!  This test should be generalized to be any function that we have
00104   // already processed, in the case when there isn't a main or there are
00105   // unreachable functions!
00106   if (F->isExternal()) {   // sprintf, fprintf, sscanf, etc...
00107     // No callees!
00108     Stack.pop_back();
00109     ValMap[F] = ~0;
00110     return Min;
00111   }
00112 
00113   DSGraph &Graph = getOrCreateGraph(F);
00114 
00115   // The edges out of the current node are the call site targets...
00116   for (DSCallSiteIterator I = DSCallSiteIterator::begin_aux(Graph),
00117          E = DSCallSiteIterator::end_aux(Graph); I != E; ++I) {
00118     Function *Callee = *I;
00119     unsigned M;
00120     // Have we visited the destination function yet?
00121     hash_map<Function*, unsigned>::iterator It = ValMap.find(Callee);
00122     if (It == ValMap.end())  // No, visit it now.
00123       M = calculateGraphs(Callee, Stack, NextID, ValMap);
00124     else                    // Yes, get it's number.
00125       M = It->second;
00126     if (M < Min) Min = M;
00127   }
00128 
00129   assert(ValMap[F] == MyID && "SCC construction assumption wrong!");
00130   if (Min != MyID)
00131     return Min;         // This is part of a larger SCC!
00132 
00133   // If this is a new SCC, process it now.
00134   if (Stack.back() == F) {           // Special case the single "SCC" case here.
00135     DEBUG(std::cerr << "Visiting single node SCC #: " << MyID << " fn: "
00136                     << F->getName() << "\n");
00137     Stack.pop_back();
00138     DSGraph &G = getDSGraph(*F);
00139     DEBUG(std::cerr << "  [BU] Calculating graph for: " << F->getName()<< "\n");
00140     calculateGraph(G);
00141     DEBUG(std::cerr << "  [BU] Done inlining: " << F->getName() << " ["
00142                     << G.getGraphSize() << "+" << G.getAuxFunctionCalls().size()
00143                     << "]\n");
00144 
00145     if (MaxSCC < 1) MaxSCC = 1;
00146 
00147     // Should we revisit the graph?
00148     if (DSCallSiteIterator::begin_aux(G) != DSCallSiteIterator::end_aux(G)) {
00149       ValMap.erase(F);
00150       return calculateGraphs(F, Stack, NextID, ValMap);
00151     } else {
00152       ValMap[F] = ~0U;
00153     }
00154     return MyID;
00155 
00156   } else {
00157     // SCCFunctions - Keep track of the functions in the current SCC
00158     //
00159     hash_set<DSGraph*> SCCGraphs;
00160 
00161     Function *NF;
00162     std::vector<Function*>::iterator FirstInSCC = Stack.end();
00163     DSGraph *SCCGraph = 0;
00164     do {
00165       NF = *--FirstInSCC;
00166       ValMap[NF] = ~0U;
00167 
00168       // Figure out which graph is the largest one, in order to speed things up
00169       // a bit in situations where functions in the SCC have widely different
00170       // graph sizes.
00171       DSGraph &NFGraph = getDSGraph(*NF);
00172       SCCGraphs.insert(&NFGraph);
00173       // FIXME: If we used a better way of cloning graphs (ie, just splice all
00174       // of the nodes into the new graph), this would be completely unneeded!
00175       if (!SCCGraph || SCCGraph->getGraphSize() < NFGraph.getGraphSize())
00176         SCCGraph = &NFGraph;
00177     } while (NF != F);
00178 
00179     std::cerr << "Calculating graph for SCC #: " << MyID << " of size: "
00180               << SCCGraphs.size() << "\n";
00181 
00182     // Compute the Max SCC Size...
00183     if (MaxSCC < SCCGraphs.size())
00184       MaxSCC = SCCGraphs.size();
00185 
00186     // First thing first, collapse all of the DSGraphs into a single graph for
00187     // the entire SCC.  We computed the largest graph, so clone all of the other
00188     // (smaller) graphs into it.  Discard all of the old graphs.
00189     //
00190     for (hash_set<DSGraph*>::iterator I = SCCGraphs.begin(),
00191            E = SCCGraphs.end(); I != E; ++I) {
00192       DSGraph &G = **I;
00193       if (&G != SCCGraph) {
00194         {
00195           DSGraph::NodeMapTy NodeMap;
00196           SCCGraph->cloneInto(G, SCCGraph->getScalarMap(),
00197                               SCCGraph->getReturnNodes(), NodeMap);
00198         }
00199         // Update the DSInfo map and delete the old graph...
00200         for (DSGraph::ReturnNodesTy::iterator I = G.getReturnNodes().begin(),
00201                E = G.getReturnNodes().end(); I != E; ++I)
00202           DSInfo[I->first] = SCCGraph;
00203         delete &G;
00204       }
00205     }
00206 
00207     // Clean up the graph before we start inlining a bunch again...
00208     SCCGraph->removeDeadNodes(DSGraph::KeepUnreachableGlobals);
00209 
00210     // Now that we have one big happy family, resolve all of the call sites in
00211     // the graph...
00212     calculateGraph(*SCCGraph);
00213     DEBUG(std::cerr << "  [BU] Done inlining SCC  [" << SCCGraph->getGraphSize()
00214                     << "+" << SCCGraph->getAuxFunctionCalls().size() << "]\n");
00215 
00216     std::cerr << "DONE with SCC #: " << MyID << "\n";
00217 
00218     // We never have to revisit "SCC" processed functions...
00219     
00220     // Drop the stuff we don't need from the end of the stack
00221     Stack.erase(FirstInSCC, Stack.end());
00222     return MyID;
00223   }
00224 
00225   return MyID;  // == Min
00226 }
00227 
00228 
00229 // releaseMemory - If the pass pipeline is done with this pass, we can release
00230 // our memory... here...
00231 //
00232 void BUDataStructures::releaseMemory() {
00233   for (hash_map<Function*, DSGraph*>::iterator I = DSInfo.begin(),
00234          E = DSInfo.end(); I != E; ++I) {
00235     I->second->getReturnNodes().erase(I->first);
00236     if (I->second->getReturnNodes().empty())
00237       delete I->second;
00238   }
00239 
00240   // Empty map so next time memory is released, data structures are not
00241   // re-deleted.
00242   DSInfo.clear();
00243   delete GlobalsGraph;
00244   GlobalsGraph = 0;
00245 }
00246 
00247 void BUDataStructures::calculateGraph(DSGraph &Graph) {
00248   // Move our call site list into TempFCs so that inline call sites go into the
00249   // new call site list and doesn't invalidate our iterators!
00250   std::vector<DSCallSite> TempFCs;
00251   std::vector<DSCallSite> &AuxCallsList = Graph.getAuxFunctionCalls();
00252   TempFCs.swap(AuxCallsList);
00253 
00254   DSGraph::ReturnNodesTy &ReturnNodes = Graph.getReturnNodes();
00255 
00256   // Loop over all of the resolvable call sites
00257   unsigned LastCallSiteIdx = ~0U;
00258   for (DSCallSiteIterator I = DSCallSiteIterator::begin(TempFCs),
00259          E = DSCallSiteIterator::end(TempFCs); I != E; ++I) {
00260     // If we skipped over any call sites, they must be unresolvable, copy them
00261     // to the real call site list.
00262     LastCallSiteIdx++;
00263     for (; LastCallSiteIdx < I.getCallSiteIdx(); ++LastCallSiteIdx)
00264       AuxCallsList.push_back(TempFCs[LastCallSiteIdx]);
00265     LastCallSiteIdx = I.getCallSiteIdx();
00266     
00267     // Resolve the current call...
00268     Function *Callee = *I;
00269     DSCallSite CS = I.getCallSite();
00270 
00271     if (Callee->isExternal()) {
00272       // Ignore this case, simple varargs functions we cannot stub out!
00273     } else if (ReturnNodes.count(Callee)) {
00274       // Self recursion... simply link up the formal arguments with the
00275       // actual arguments...
00276       DEBUG(std::cerr << "    Self Inlining: " << Callee->getName() << "\n");
00277 
00278       // Handle self recursion by resolving the arguments and return value
00279       Graph.mergeInGraph(CS, *Callee, Graph, 0);
00280 
00281     } else {
00282       ActualCallees.insert(std::make_pair(CS.getCallSite().getInstruction(),
00283                                           Callee));
00284 
00285       // Get the data structure graph for the called function.
00286       //
00287       DSGraph &GI = getDSGraph(*Callee);  // Graph to inline
00288 
00289       DEBUG(std::cerr << "    Inlining graph for " << Callee->getName()
00290             << "[" << GI.getGraphSize() << "+"
00291             << GI.getAuxFunctionCalls().size() << "] into '"
00292             << Graph.getFunctionNames() << "' [" << Graph.getGraphSize() << "+"
00293             << Graph.getAuxFunctionCalls().size() << "]\n");
00294       Graph.mergeInGraph(CS, *Callee, GI,
00295                          DSGraph::KeepModRefBits | 
00296                          DSGraph::StripAllocaBit | DSGraph::DontCloneCallNodes);
00297       ++NumBUInlines;
00298 
00299 #if 0
00300       Graph.writeGraphToFile(std::cerr, "bu_" + F.getName() + "_after_" +
00301                              Callee->getName());
00302 #endif
00303     }
00304   }
00305 
00306   // Make sure to catch any leftover unresolvable calls...
00307   for (++LastCallSiteIdx; LastCallSiteIdx < TempFCs.size(); ++LastCallSiteIdx)
00308     AuxCallsList.push_back(TempFCs[LastCallSiteIdx]);
00309 
00310   TempFCs.clear();
00311 
00312   // Recompute the Incomplete markers
00313   assert(Graph.getInlinedGlobals().empty());
00314   Graph.maskIncompleteMarkers();
00315   Graph.markIncompleteNodes(DSGraph::MarkFormalArgs);
00316 
00317   // Delete dead nodes.  Treat globals that are unreachable but that can
00318   // reach live nodes as live.
00319   Graph.removeDeadNodes(DSGraph::KeepUnreachableGlobals);
00320 
00321   // When this graph is finalized, clone the globals in the graph into the
00322   // globals graph to make sure it has everything, from all graphs.
00323   DSScalarMap &MainSM = Graph.getScalarMap();
00324   ReachabilityCloner RC(*GlobalsGraph, Graph, DSGraph::StripAllocaBit);
00325 
00326   // Clone everything reachable from globals in the function graph into the
00327   // globals graph.
00328   for (DSScalarMap::global_iterator I = MainSM.global_begin(),
00329          E = MainSM.global_end(); I != E; ++I) 
00330     RC.getClonedNH(MainSM[*I]);
00331 
00332   //Graph.writeGraphToFile(std::cerr, "bu_" + F.getName());
00333 }