lib/Analysis/DataStructure/TopDownClosure.cpp

   1 //===- TopDownClosure.cpp - Compute the top-down interprocedure closure ---===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   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.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the TDDataStructures class, which represents the
  11 // Top-down Interprocedural closure of the data structure graph over the
  12 // program.  This is useful (but not strictly necessary?) for applications
  13 // like pointer analysis.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "llvm/Analysis/DataStructure/DataStructure.h"
  18 #include "llvm/Module.h"
  19 #include "llvm/DerivedTypes.h"
  20 #include "llvm/Analysis/DataStructure/DSGraph.h"
  21 #include "llvm/Support/Debug.h"
  22 #include "llvm/Support/Timer.h"
  23 #include "llvm/ADT/Statistic.h"
  24 #include <iostream>
  25 using namespace llvm;
  26
  27 #if 0
  28 #define TIME_REGION(VARNAME, DESC) \
  29    NamedRegionTimer VARNAME(DESC)
  30 #else
  31 #define TIME_REGION(VARNAME, DESC)
  32 #endif
  33
  34 namespace {
  35   RegisterAnalysis<TDDataStructures>   // Register the pass
  36   Y("tddatastructure", "Top-down Data Structure Analysis");
  37
  38   Statistic<> NumTDInlines("tddatastructures", "Number of graphs inlined");
  39 }
  40
  41 void TDDataStructures::markReachableFunctionsExternallyAccessible(DSNode *N,
  42                                                    hash_set<DSNode*> &Visited) {
  43   if (!N || Visited.count(N)) return;
  44   Visited.insert(N);
  45
  46   for (unsigned i = 0, e = N->getNumLinks(); i != e; ++i) {
  47     DSNodeHandle &NH = N->getLink(i*N->getPointerSize());
  48     if (DSNode *NN = NH.getNode()) {
  49       std::vector<Function*> Functions;
  50       NN->addFullFunctionList(Functions);
  51       ArgsRemainIncomplete.insert(Functions.begin(), Functions.end());
  52       markReachableFunctionsExternallyAccessible(NN, Visited);
  53     }
  54   }
  55 }
  56
  57
  58 // run - Calculate the top down data structure graphs for each function in the
  59 // program.
  60 //
  61 bool TDDataStructures::runOnModule(Module &M) {
  62   BUInfo = &getAnalysis<BUDataStructures>();
  63   GlobalECs = BUInfo->getGlobalECs();
  64   GlobalsGraph = new DSGraph(BUInfo->getGlobalsGraph(), GlobalECs);
  65   GlobalsGraph->setPrintAuxCalls();
  66
  67   // Figure out which functions must not mark their arguments complete because
  68   // they are accessible outside this compilation unit.  Currently, these
  69   // arguments are functions which are reachable by global variables in the
  70   // globals graph.
  71   const DSScalarMap &GGSM = GlobalsGraph->getScalarMap();
  72   hash_set<DSNode*> Visited;
  73   for (DSScalarMap::global_iterator I=GGSM.global_begin(), E=GGSM.global_end();
  74        I != E; ++I) {
  75     DSNode *N = GGSM.find(*I)->second.getNode();
  76     if (N->isIncomplete())
  77       markReachableFunctionsExternallyAccessible(N, Visited);
  78   }
  79
  80   // Loop over unresolved call nodes.  Any functions passed into (but not
  81   // returned!) from unresolvable call nodes may be invoked outside of the
  82   // current module.
  83   for (DSGraph::afc_iterator I = GlobalsGraph->afc_begin(),
  84          E = GlobalsGraph->afc_end(); I != E; ++I)
  85     for (unsigned arg = 0, e = I->getNumPtrArgs(); arg != e; ++arg)
  86       markReachableFunctionsExternallyAccessible(I->getPtrArg(arg).getNode(),
  87                                                  Visited);
  88   Visited.clear();
  89
  90   // Functions without internal linkage also have unknown incoming arguments!
  91   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  92     if (!I->isExternal() && !I->hasInternalLinkage())
  93       ArgsRemainIncomplete.insert(I);
  94
  95   // We want to traverse the call graph in reverse post-order.  To do this, we
  96   // calculate a post-order traversal, then reverse it.
  97   hash_set<DSGraph*> VisitedGraph;
  98   std::vector<DSGraph*> PostOrder;
  99
 100 #if 0
 101 {TIME_REGION(XXX, "td:Copy graphs");
 102
 103   // Visit each of the graphs in reverse post-order now!
 104   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
 105     if (!I->isExternal())
 106       getOrCreateDSGraph(*I);
 107   return false;
 108 }
 109 #endif
 110
 111
 112 {TIME_REGION(XXX, "td:Compute postorder");
 113
 114   // Calculate top-down from main...
 115   if (Function *F = M.getMainFunction())
 116     ComputePostOrder(*F, VisitedGraph, PostOrder);
 117
 118   // Next calculate the graphs for each unreachable function...
 119   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
 120     ComputePostOrder(*I, VisitedGraph, PostOrder);
 121
 122   VisitedGraph.clear();   // Release memory!
 123 }
 124
 125 {TIME_REGION(XXX, "td:Inline stuff");
 126
 127   // Visit each of the graphs in reverse post-order now!
 128   while (!PostOrder.empty()) {
 129     InlineCallersIntoGraph(*PostOrder.back());
 130     PostOrder.pop_back();
 131   }
 132 }
 133
 134   // Free the IndCallMap.
 135   while (!IndCallMap.empty()) {
 136     delete IndCallMap.begin()->second;
 137     IndCallMap.erase(IndCallMap.begin());
 138   }
 139
 140
 141   ArgsRemainIncomplete.clear();
 142   GlobalsGraph->removeTriviallyDeadNodes();
 143
 144   return false;
 145 }
 146
 147
 148 DSGraph &TDDataStructures::getOrCreateDSGraph(Function &F) {
 149   DSGraph *&G = DSInfo[&F];
 150   if (G == 0) { // Not created yet?  Clone BU graph...
 151     G = new DSGraph(getAnalysis<BUDataStructures>().getDSGraph(F), GlobalECs,
 152                     DSGraph::DontCloneAuxCallNodes);
 153     assert(G->getAuxFunctionCalls().empty() && "Cloned aux calls?");
 154     G->setPrintAuxCalls();
 155     G->setGlobalsGraph(GlobalsGraph);
 156
 157     // Note that this graph is the graph for ALL of the function in the SCC, not
 158     // just F.
 159     for (DSGraph::retnodes_iterator RI = G->retnodes_begin(),
 160            E = G->retnodes_end(); RI != E; ++RI)
 161       if (RI->first != &F)
 162         DSInfo[RI->first] = G;
 163   }
 164   return *G;
 165 }
 166
 167
 168 void TDDataStructures::ComputePostOrder(Function &F,hash_set<DSGraph*> &Visited,
 169                                         std::vector<DSGraph*> &PostOrder) {
 170   if (F.isExternal()) return;
 171   DSGraph &G = getOrCreateDSGraph(F);
 172   if (Visited.count(&G)) return;
 173   Visited.insert(&G);
 174
 175   // Recursively traverse all of the callee graphs.
 176   for (DSGraph::fc_iterator CI = G.fc_begin(), CE = G.fc_end(); CI != CE; ++CI){
 177     Instruction *CallI = CI->getCallSite().getInstruction();
 178     for (BUDataStructures::callee_iterator I = BUInfo->callee_begin(CallI),
 179            E = BUInfo->callee_end(CallI); I != E; ++I)
 180       ComputePostOrder(*I->second, Visited, PostOrder);
 181   }
 182
 183   PostOrder.push_back(&G);
 184 }
 185
 186
 187
 188
 189
 190 // releaseMemory - If the pass pipeline is done with this pass, we can release
 191 // our memory... here...
 192 //
 193 // FIXME: This should be releaseMemory and will work fine, except that LoadVN
 194 // has no way to extend the lifetime of the pass, which screws up ds-aa.
 195 //
 196 void TDDataStructures::releaseMyMemory() {
 197   for (hash_map<Function*, DSGraph*>::iterator I = DSInfo.begin(),
 198          E = DSInfo.end(); I != E; ++I) {
 199     I->second->getReturnNodes().erase(I->first);
 200     if (I->second->getReturnNodes().empty())
 201       delete I->second;
 202   }
 203
 204   // Empty map so next time memory is released, data structures are not
 205   // re-deleted.
 206   DSInfo.clear();
 207   delete GlobalsGraph;
 208   GlobalsGraph = 0;
 209 }
 210
 211 /// InlineCallersIntoGraph - Inline all of the callers of the specified DS graph
 212 /// into it, then recompute completeness of nodes in the resultant graph.
 213 void TDDataStructures::InlineCallersIntoGraph(DSGraph &DSG) {
 214   // Inline caller graphs into this graph.  First step, get the list of call
 215   // sites that call into this graph.
 216   std::vector<CallerCallEdge> EdgesFromCaller;
 217   std::map<DSGraph*, std::vector<CallerCallEdge> >::iterator
 218     CEI = CallerEdges.find(&DSG);
 219   if (CEI != CallerEdges.end()) {
 220     std::swap(CEI->second, EdgesFromCaller);
 221     CallerEdges.erase(CEI);
 222   }
 223
 224   // Sort the caller sites to provide a by-caller-graph ordering.
 225   std::sort(EdgesFromCaller.begin(), EdgesFromCaller.end());
 226
 227
 228   // Merge information from the globals graph into this graph.  FIXME: This is
 229   // stupid.  Instead of us cloning information from the GG into this graph,
 230   // then having RemoveDeadNodes clone it back, we should do all of this as a
 231   // post-pass over all of the graphs.  We need to take cloning out of
 232   // removeDeadNodes and gut removeDeadNodes at the same time first though. :(
 233   {
 234     DSGraph &GG = *DSG.getGlobalsGraph();
 235     ReachabilityCloner RC(DSG, GG,
 236                           DSGraph::DontCloneCallNodes |
 237                           DSGraph::DontCloneAuxCallNodes);
 238     for (DSScalarMap::global_iterator
 239            GI = DSG.getScalarMap().global_begin(),
 240            E = DSG.getScalarMap().global_end(); GI != E; ++GI)
 241       RC.getClonedNH(GG.getNodeForValue(*GI));
 242   }
 243
 244   DEBUG(std::cerr << "[TD] Inlining callers into '" << DSG.getFunctionNames()
 245         << "'\n");
 246
 247   // Iteratively inline caller graphs into this graph.
 248   while (!EdgesFromCaller.empty()) {
 249     DSGraph &CallerGraph = *EdgesFromCaller.back().CallerGraph;
 250
 251     // Iterate through all of the call sites of this graph, cloning and merging
 252     // any nodes required by the call.
 253     ReachabilityCloner RC(DSG, CallerGraph,
 254                           DSGraph::DontCloneCallNodes |
 255                           DSGraph::DontCloneAuxCallNodes);
 256
 257     // Inline all call sites from this caller graph.
 258     do {
 259       const DSCallSite &CS = *EdgesFromCaller.back().CS;
 260       Function &CF = *EdgesFromCaller.back().CalledFunction;
 261       DEBUG(std::cerr << "   [TD] Inlining graph into Fn '"
 262             << CF.getName() << "' from ");
 263       if (CallerGraph.getReturnNodes().empty())
 264         DEBUG(std::cerr << "SYNTHESIZED INDIRECT GRAPH");
 265       else
 266         DEBUG (std::cerr << "Fn '"
 267                << CS.getCallSite().getInstruction()->
 268                getParent()->getParent()->getName() << "'");
 269       DEBUG(std::cerr << ": " << CF.getFunctionType()->getNumParams()
 270             << " args\n");
 271
 272       // Get the formal argument and return nodes for the called function and
 273       // merge them with the cloned subgraph.
 274       DSCallSite T1 = DSG.getCallSiteForArguments(CF);
 275       RC.mergeCallSite(T1, CS);
 276       ++NumTDInlines;
 277
 278       EdgesFromCaller.pop_back();
 279     } while (!EdgesFromCaller.empty() &&
 280              EdgesFromCaller.back().CallerGraph == &CallerGraph);
 281   }
 282
 283
 284   // Next, now that this graph is finalized, we need to recompute the
 285   // incompleteness markers for this graph and remove unreachable nodes.
 286   DSG.maskIncompleteMarkers();
 287
 288   // If any of the functions has incomplete incoming arguments, don't mark any
 289   // of them as complete.
 290   bool HasIncompleteArgs = false;
 291   for (DSGraph::retnodes_iterator I = DSG.retnodes_begin(),
 292          E = DSG.retnodes_end(); I != E; ++I)
 293     if (ArgsRemainIncomplete.count(I->first)) {
 294       HasIncompleteArgs = true;
 295       break;
 296     }
 297
 298   // Recompute the Incomplete markers.  Depends on whether args are complete
 299   unsigned Flags
 300     = HasIncompleteArgs ? DSGraph::MarkFormalArgs : DSGraph::IgnoreFormalArgs;
 301   DSG.markIncompleteNodes(Flags | DSGraph::IgnoreGlobals);
 302
 303   // Delete dead nodes.  Treat globals that are unreachable as dead also.
 304   DSG.removeDeadNodes(DSGraph::RemoveUnreachableGlobals);
 305
 306   // We are done with computing the current TD Graph!  Finally, before we can
 307   // finish processing this function, we figure out which functions it calls and
 308   // records these call graph edges, so that we have them when we process the
 309   // callee graphs.
 310   if (DSG.fc_begin() == DSG.fc_end()) return;
 311
 312   // Loop over all the call sites and all the callees at each call site, and add
 313   // edges to the CallerEdges structure for each callee.
 314   for (DSGraph::fc_iterator CI = DSG.fc_begin(), E = DSG.fc_end();
 315        CI != E; ++CI) {
 316
 317     // Handle direct calls efficiently.
 318     if (CI->isDirectCall()) {
 319       if (!CI->getCalleeFunc()->isExternal() &&
 320           !DSG.getReturnNodes().count(CI->getCalleeFunc()))
 321         CallerEdges[&getDSGraph(*CI->getCalleeFunc())]
 322           .push_back(CallerCallEdge(&DSG, &*CI, CI->getCalleeFunc()));
 323       continue;
 324     }
 325
 326     Instruction *CallI = CI->getCallSite().getInstruction();
 327     // For each function in the invoked function list at this call site...
 328     BUDataStructures::callee_iterator IPI =
 329       BUInfo->callee_begin(CallI), IPE = BUInfo->callee_end(CallI);
 330
 331     // Skip over all calls to this graph (SCC calls).
 332     while (IPI != IPE && &getDSGraph(*IPI->second) == &DSG)
 333       ++IPI;
 334
 335     // All SCC calls?
 336     if (IPI == IPE) continue;
 337
 338     Function *FirstCallee = IPI->second;
 339     ++IPI;
 340
 341     // Skip over more SCC calls.
 342     while (IPI != IPE && &getDSGraph(*IPI->second) == &DSG)
 343       ++IPI;
 344
 345     // If there is exactly one callee from this call site, remember the edge in
 346     // CallerEdges.
 347     if (IPI == IPE) {
 348       if (!FirstCallee->isExternal())
 349         CallerEdges[&getDSGraph(*FirstCallee)]
 350           .push_back(CallerCallEdge(&DSG, &*CI, FirstCallee));
 351       continue;
 352     }
 353
 354     // Otherwise, there are multiple callees from this call site, so it must be
 355     // an indirect call.  Chances are that there will be other call sites with
 356     // this set of targets.  If so, we don't want to do M*N inlining operations,
 357     // so we build up a new, private, graph that represents the calls of all
 358     // calls to this set of functions.
 359     std::vector<Function*> Callees;
 360     for (BUDataStructures::ActualCalleesTy::const_iterator I =
 361            BUInfo->callee_begin(CallI), E = BUInfo->callee_end(CallI);
 362          I != E; ++I)
 363       if (!I->second->isExternal())
 364         Callees.push_back(I->second);
 365     std::sort(Callees.begin(), Callees.end());
 366
 367     std::map<std::vector<Function*>, DSGraph*>::iterator IndCallRecI =
 368       IndCallMap.lower_bound(Callees);
 369
 370     DSGraph *IndCallGraph;
 371
 372     // If we already have this graph, recycle it.
 373     if (IndCallRecI != IndCallMap.end() && IndCallRecI->first == Callees) {
 374       std::cerr << "  [TD] *** Reuse of indcall graph for " << Callees.size()
 375                 << " callees!\n";
 376       IndCallGraph = IndCallRecI->second;
 377     } else {
 378       // Otherwise, create a new DSGraph to represent this.
 379       IndCallGraph = new DSGraph(DSG.getGlobalECs(), DSG.getTargetData());
 380
 381       // Make a nullary dummy call site, which will eventually get some content
 382       // merged into it.  The actual callee function doesn't matter here, so we
 383       // just pass it something to keep the ctor happy.
 384       std::vector<DSNodeHandle> ArgDummyVec;
 385       DSCallSite DummyCS(CI->getCallSite(), DSNodeHandle(), Callees[0]/*dummy*/,
 386                          ArgDummyVec);
 387       IndCallGraph->getFunctionCalls().push_back(DummyCS);
 388
 389       IndCallRecI = IndCallMap.insert(IndCallRecI,
 390                                       std::make_pair(Callees, IndCallGraph));
 391
 392       // Additionally, make sure that each of the callees inlines this graph
 393       // exactly once.
 394       DSCallSite *NCS = &IndCallGraph->getFunctionCalls().front();
 395       for (unsigned i = 0, e = Callees.size(); i != e; ++i) {
 396         DSGraph& CalleeGraph = getDSGraph(*Callees[i]);
 397         if (&CalleeGraph != &DSG)
 398           CallerEdges[&CalleeGraph].push_back(CallerCallEdge(IndCallGraph, NCS,
 399                                                              Callees[i]));
 400       }
 401     }
 402
 403     // Now that we know which graph to use for this, merge the caller
 404     // information into the graph, based on information from the call site.
 405     ReachabilityCloner RC(*IndCallGraph, DSG, 0);
 406     RC.mergeCallSite(IndCallGraph->getFunctionCalls().front(), *CI);
 407   }
 408 }
 409
 410
 411 static const Function *getFnForValue(const Value *V) {
 412   if (const Instruction *I = dyn_cast<Instruction>(V))
 413     return I->getParent()->getParent();
 414   else if (const Argument *A = dyn_cast<Argument>(V))
 415     return A->getParent();
 416   else if (const BasicBlock *BB = dyn_cast<BasicBlock>(V))
 417     return BB->getParent();
 418   return 0;
 419 }
 420
 421 void TDDataStructures::deleteValue(Value *V) {
 422   if (const Function *F = getFnForValue(V)) {  // Function local value?
 423     // If this is a function local value, just delete it from the scalar map!
 424     getDSGraph(*F).getScalarMap().eraseIfExists(V);
 425     return;
 426   }
 427
 428   if (Function *F = dyn_cast<Function>(V)) {
 429     assert(getDSGraph(*F).getReturnNodes().size() == 1 &&
 430            "cannot handle scc's");
 431     delete DSInfo[F];
 432     DSInfo.erase(F);
 433     return;
 434   }
 435
 436   assert(!isa<GlobalVariable>(V) && "Do not know how to delete GV's yet!");
 437 }
 438
 439 void TDDataStructures::copyValue(Value *From, Value *To) {
 440   if (From == To) return;
 441   if (const Function *F = getFnForValue(From)) {  // Function local value?
 442     // If this is a function local value, just delete it from the scalar map!
 443     getDSGraph(*F).getScalarMap().copyScalarIfExists(From, To);
 444     return;
 445   }
 446
 447   if (Function *FromF = dyn_cast<Function>(From)) {
 448     Function *ToF = cast<Function>(To);
 449     assert(!DSInfo.count(ToF) && "New Function already exists!");
 450     DSGraph *NG = new DSGraph(getDSGraph(*FromF), GlobalECs);
 451     DSInfo[ToF] = NG;
 452     assert(NG->getReturnNodes().size() == 1 && "Cannot copy SCC's yet!");
 453
 454     // Change the Function* is the returnnodes map to the ToF.
 455     DSNodeHandle Ret = NG->retnodes_begin()->second;
 456     NG->getReturnNodes().clear();
 457     NG->getReturnNodes()[ToF] = Ret;
 458     return;
 459   }
 460
 461   if (const Function *F = getFnForValue(To)) {
 462     DSGraph &G = getDSGraph(*F);
 463     G.getScalarMap().copyScalarIfExists(From, To);
 464     return;
 465   }
 466
 467   std::cerr << *From;
 468   std::cerr << *To;
 469   assert(0 && "Do not know how to copy this yet!");
 470   abort();
 471 }