src/llvm/lib/Analysis/IPA/CallGraphSCCPass.cpp

   1 //===- CallGraphSCCPass.cpp - Pass that operates BU on call graph ---------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the CallGraphSCCPass class, which is used for passes
  11 // which are implemented as bottom-up traversals on the call graph.  Because
  12 // there may be cycles in the call graph, passes of this type operate on the
  13 // call-graph in SCC order: that is, they process function bottom-up, except for
  14 // recursive functions, which they process all at once.
  15 //
  16 //===----------------------------------------------------------------------===//
  17
  18 #include "llvm/Analysis/CallGraphSCCPass.h"
  19 #include "llvm/ADT/SCCIterator.h"
  20 #include "llvm/ADT/Statistic.h"
  21 #include "llvm/Analysis/CallGraph.h"
  22 #include "llvm/IR/Function.h"
  23 #include "llvm/IR/IntrinsicInst.h"
  24 #include "llvm/IR/LLVMContext.h"
  25 #include "llvm/IR/LegacyPassManagers.h"
  26 #include "llvm/Support/CommandLine.h"
  27 #include "llvm/Support/Debug.h"
  28 #include "llvm/Support/Timer.h"
  29 #include "llvm/Support/raw_ostream.h"
  30 using namespace llvm;
  31
  32 #define DEBUG_TYPE "cgscc-passmgr"
  33
  34 static cl::opt<unsigned>
  35 MaxIterations("max-cg-scc-iterations", cl::ReallyHidden, cl::init(4));
  36
  37 STATISTIC(MaxSCCIterations, "Maximum CGSCCPassMgr iterations on one SCC");
  38
  39 //===----------------------------------------------------------------------===//
  40 // CGPassManager
  41 //
  42 /// CGPassManager manages FPPassManagers and CallGraphSCCPasses.
  43
  44 namespace {
  45
  46 class CGPassManager : public ModulePass, public PMDataManager {
  47 public:
  48   static char ID;
  49   explicit CGPassManager()
  50     : ModulePass(ID), PMDataManager() { }
  51
  52   /// run - Execute all of the passes scheduled for execution.  Keep track of
  53   /// whether any of the passes modifies the module, and if so, return true.
  54   bool runOnModule(Module &M) override;
  55
  56   using ModulePass::doInitialization;
  57   using ModulePass::doFinalization;
  58
  59   bool doInitialization(CallGraph &CG);
  60   bool doFinalization(CallGraph &CG);
  61
  62   /// Pass Manager itself does not invalidate any analysis info.
  63   void getAnalysisUsage(AnalysisUsage &Info) const override {
  64     // CGPassManager walks SCC and it needs CallGraph.
  65     Info.addRequired<CallGraphWrapperPass>();
  66     Info.setPreservesAll();
  67   }
  68
  69   const char *getPassName() const override {
  70     return "CallGraph Pass Manager";
  71   }
  72
  73   PMDataManager *getAsPMDataManager() override { return this; }
  74   Pass *getAsPass() override { return this; }
  75
  76   // Print passes managed by this manager
  77   void dumpPassStructure(unsigned Offset) override {
  78     errs().indent(Offset*2) << "Call Graph SCC Pass Manager\n";
  79     for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
  80       Pass *P = getContainedPass(Index);
  81       P->dumpPassStructure(Offset + 1);
  82       dumpLastUses(P, Offset+1);
  83     }
  84   }
  85
  86   Pass *getContainedPass(unsigned N) {
  87     assert(N < PassVector.size() && "Pass number out of range!");
  88     return static_cast<Pass *>(PassVector[N]);
  89   }
  90
  91   PassManagerType getPassManagerType() const override {
  92     return PMT_CallGraphPassManager;
  93   }
  94
  95 private:
  96   bool RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
  97                          bool &DevirtualizedCall);
  98
  99   bool RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
 100                     CallGraph &CG, bool &CallGraphUpToDate,
 101                     bool &DevirtualizedCall);
 102   bool RefreshCallGraph(CallGraphSCC &CurSCC, CallGraph &CG,
 103                         bool IsCheckingMode);
 104 };
 105
 106 } // end anonymous namespace.
 107
 108 char CGPassManager::ID = 0;
 109
 110
 111 bool CGPassManager::RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
 112                                  CallGraph &CG, bool &CallGraphUpToDate,
 113                                  bool &DevirtualizedCall) {
 114   bool Changed = false;
 115   PMDataManager *PM = P->getAsPMDataManager();
 116
 117   if (!PM) {
 118     CallGraphSCCPass *CGSP = (CallGraphSCCPass*)P;
 119     if (!CallGraphUpToDate) {
 120       DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
 121       CallGraphUpToDate = true;
 122     }
 123
 124     {
 125       TimeRegion PassTimer(getPassTimer(CGSP));
 126       Changed = CGSP->runOnSCC(CurSCC);
 127     }
 128
 129     // After the CGSCCPass is done, when assertions are enabled, use
 130     // RefreshCallGraph to verify that the callgraph was correctly updated.
 131 #ifndef NDEBUG
 132     if (Changed)
 133       RefreshCallGraph(CurSCC, CG, true);
 134 #endif
 135
 136     return Changed;
 137   }
 138
 139
 140   assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
 141          "Invalid CGPassManager member");
 142   FPPassManager *FPP = (FPPassManager*)P;
 143
 144   // Run pass P on all functions in the current SCC.
 145   for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
 146        I != E; ++I) {
 147     if (Function *F = (*I)->getFunction()) {
 148       dumpPassInfo(P, EXECUTION_MSG, ON_FUNCTION_MSG, F->getName());
 149       {
 150         TimeRegion PassTimer(getPassTimer(FPP));
 151         Changed |= FPP->runOnFunction(*F);
 152       }
 153       F->getContext().yield();
 154     }
 155   }
 156
 157   // The function pass(es) modified the IR, they may have clobbered the
 158   // callgraph.
 159   if (Changed && CallGraphUpToDate) {
 160     DEBUG(dbgs() << "CGSCCPASSMGR: Pass Dirtied SCC: "
 161                  << P->getPassName() << '\n');
 162     CallGraphUpToDate = false;
 163   }
 164   return Changed;
 165 }
 166
 167
 168 /// RefreshCallGraph - Scan the functions in the specified CFG and resync the
 169 /// callgraph with the call sites found in it.  This is used after
 170 /// FunctionPasses have potentially munged the callgraph, and can be used after
 171 /// CallGraphSCC passes to verify that they correctly updated the callgraph.
 172 ///
 173 /// This function returns true if it devirtualized an existing function call,
 174 /// meaning it turned an indirect call into a direct call.  This happens when
 175 /// a function pass like GVN optimizes away stuff feeding the indirect call.
 176 /// This never happens in checking mode.
 177 ///
 178 bool CGPassManager::RefreshCallGraph(CallGraphSCC &CurSCC,
 179                                      CallGraph &CG, bool CheckingMode) {
 180   DenseMap<Value*, CallGraphNode*> CallSites;
 181
 182   DEBUG(dbgs() << "CGSCCPASSMGR: Refreshing SCC with " << CurSCC.size()
 183                << " nodes:\n";
 184         for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
 185              I != E; ++I)
 186           (*I)->dump();
 187         );
 188
 189   bool MadeChange = false;
 190   bool DevirtualizedCall = false;
 191
 192   // Scan all functions in the SCC.
 193   unsigned FunctionNo = 0;
 194   for (CallGraphSCC::iterator SCCIdx = CurSCC.begin(), E = CurSCC.end();
 195        SCCIdx != E; ++SCCIdx, ++FunctionNo) {
 196     CallGraphNode *CGN = *SCCIdx;
 197     Function *F = CGN->getFunction();
 198     if (!F || F->isDeclaration()) continue;
 199
 200     // Walk the function body looking for call sites.  Sync up the call sites in
 201     // CGN with those actually in the function.
 202
 203     // Keep track of the number of direct and indirect calls that were
 204     // invalidated and removed.
 205     unsigned NumDirectRemoved = 0, NumIndirectRemoved = 0;
 206
 207     // Get the set of call sites currently in the function.
 208     for (CallGraphNode::iterator I = CGN->begin(), E = CGN->end(); I != E; ) {
 209       // If this call site is null, then the function pass deleted the call
 210       // entirely and the WeakVH nulled it out.
 211       if (!I->first ||
 212           // If we've already seen this call site, then the FunctionPass RAUW'd
 213           // one call with another, which resulted in two "uses" in the edge
 214           // list of the same call.
 215           CallSites.count(I->first) ||
 216
 217           // If the call edge is not from a call or invoke, then the function
 218           // pass RAUW'd a call with another value.  This can happen when
 219           // constant folding happens of well known functions etc.
 220           !CallSite(I->first)) {
 221         assert(!CheckingMode &&
 222                "CallGraphSCCPass did not update the CallGraph correctly!");
 223
 224         // If this was an indirect call site, count it.
 225         if (!I->second->getFunction())
 226           ++NumIndirectRemoved;
 227         else
 228           ++NumDirectRemoved;
 229
 230         // Just remove the edge from the set of callees, keep track of whether
 231         // I points to the last element of the vector.
 232         bool WasLast = I + 1 == E;
 233         CGN->removeCallEdge(I);
 234
 235         // If I pointed to the last element of the vector, we have to bail out:
 236         // iterator checking rejects comparisons of the resultant pointer with
 237         // end.
 238         if (WasLast)
 239           break;
 240         E = CGN->end();
 241         continue;
 242       }
 243
 244       assert(!CallSites.count(I->first) &&
 245              "Call site occurs in node multiple times");
 246
 247       CallSite CS(I->first);
 248       if (CS) {
 249         Function *Callee = CS.getCalledFunction();
 250         // Ignore intrinsics because they're not really function calls.
 251         if (!Callee || !(Callee->isIntrinsic()))
 252           CallSites.insert(std::make_pair(I->first, I->second));
 253       }
 254       ++I;
 255     }
 256
 257     // Loop over all of the instructions in the function, getting the callsites.
 258     // Keep track of the number of direct/indirect calls added.
 259     unsigned NumDirectAdded = 0, NumIndirectAdded = 0;
 260
 261     for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
 262       for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
 263         CallSite CS(cast<Value>(I));
 264         if (!CS) continue;
 265         Function *Callee = CS.getCalledFunction();
 266         if (Callee && Callee->isIntrinsic()) continue;
 267
 268         // If this call site already existed in the callgraph, just verify it
 269         // matches up to expectations and remove it from CallSites.
 270         DenseMap<Value*, CallGraphNode*>::iterator ExistingIt =
 271           CallSites.find(CS.getInstruction());
 272         if (ExistingIt != CallSites.end()) {
 273           CallGraphNode *ExistingNode = ExistingIt->second;
 274
 275           // Remove from CallSites since we have now seen it.
 276           CallSites.erase(ExistingIt);
 277
 278           // Verify that the callee is right.
 279           if (ExistingNode->getFunction() == CS.getCalledFunction())
 280             continue;
 281
 282           // If we are in checking mode, we are not allowed to actually mutate
 283           // the callgraph.  If this is a case where we can infer that the
 284           // callgraph is less precise than it could be (e.g. an indirect call
 285           // site could be turned direct), don't reject it in checking mode, and
 286           // don't tweak it to be more precise.
 287           if (CheckingMode && CS.getCalledFunction() &&
 288               ExistingNode->getFunction() == nullptr)
 289             continue;
 290
 291           assert(!CheckingMode &&
 292                  "CallGraphSCCPass did not update the CallGraph correctly!");
 293
 294           // If not, we either went from a direct call to indirect, indirect to
 295           // direct, or direct to different direct.
 296           CallGraphNode *CalleeNode;
 297           if (Function *Callee = CS.getCalledFunction()) {
 298             CalleeNode = CG.getOrInsertFunction(Callee);
 299             // Keep track of whether we turned an indirect call into a direct
 300             // one.
 301             if (!ExistingNode->getFunction()) {
 302               DevirtualizedCall = true;
 303               DEBUG(dbgs() << "  CGSCCPASSMGR: Devirtualized call to '"
 304                            << Callee->getName() << "'\n");
 305             }
 306           } else {
 307             CalleeNode = CG.getCallsExternalNode();
 308           }
 309
 310           // Update the edge target in CGN.
 311           CGN->replaceCallEdge(CS, CS, CalleeNode);
 312           MadeChange = true;
 313           continue;
 314         }
 315
 316         assert(!CheckingMode &&
 317                "CallGraphSCCPass did not update the CallGraph correctly!");
 318
 319         // If the call site didn't exist in the CGN yet, add it.
 320         CallGraphNode *CalleeNode;
 321         if (Function *Callee = CS.getCalledFunction()) {
 322           CalleeNode = CG.getOrInsertFunction(Callee);
 323           ++NumDirectAdded;
 324         } else {
 325           CalleeNode = CG.getCallsExternalNode();
 326           ++NumIndirectAdded;
 327         }
 328
 329         CGN->addCalledFunction(CS, CalleeNode);
 330         MadeChange = true;
 331       }
 332
 333     // We scanned the old callgraph node, removing invalidated call sites and
 334     // then added back newly found call sites.  One thing that can happen is
 335     // that an old indirect call site was deleted and replaced with a new direct
 336     // call.  In this case, we have devirtualized a call, and CGSCCPM would like
 337     // to iteratively optimize the new code.  Unfortunately, we don't really
 338     // have a great way to detect when this happens.  As an approximation, we
 339     // just look at whether the number of indirect calls is reduced and the
 340     // number of direct calls is increased.  There are tons of ways to fool this
 341     // (e.g. DCE'ing an indirect call and duplicating an unrelated block with a
 342     // direct call) but this is close enough.
 343     if (NumIndirectRemoved > NumIndirectAdded &&
 344         NumDirectRemoved < NumDirectAdded)
 345       DevirtualizedCall = true;
 346
 347     // After scanning this function, if we still have entries in callsites, then
 348     // they are dangling pointers.  WeakVH should save us for this, so abort if
 349     // this happens.
 350     assert(CallSites.empty() && "Dangling pointers found in call sites map");
 351
 352     // Periodically do an explicit clear to remove tombstones when processing
 353     // large scc's.
 354     if ((FunctionNo & 15) == 15)
 355       CallSites.clear();
 356   }
 357
 358   DEBUG(if (MadeChange) {
 359           dbgs() << "CGSCCPASSMGR: Refreshed SCC is now:\n";
 360           for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
 361             I != E; ++I)
 362               (*I)->dump();
 363           if (DevirtualizedCall)
 364             dbgs() << "CGSCCPASSMGR: Refresh devirtualized a call!\n";
 365
 366          } else {
 367            dbgs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n";
 368          }
 369         );
 370   (void)MadeChange;
 371
 372   return DevirtualizedCall;
 373 }
 374
 375 /// RunAllPassesOnSCC -  Execute the body of the entire pass manager on the
 376 /// specified SCC.  This keeps track of whether a function pass devirtualizes
 377 /// any calls and returns it in DevirtualizedCall.
 378 bool CGPassManager::RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
 379                                       bool &DevirtualizedCall) {
 380   bool Changed = false;
 381
 382   // CallGraphUpToDate - Keep track of whether the callgraph is known to be
 383   // up-to-date or not.  The CGSSC pass manager runs two types of passes:
 384   // CallGraphSCC Passes and other random function passes.  Because other
 385   // random function passes are not CallGraph aware, they may clobber the
 386   // call graph by introducing new calls or deleting other ones.  This flag
 387   // is set to false when we run a function pass so that we know to clean up
 388   // the callgraph when we need to run a CGSCCPass again.
 389   bool CallGraphUpToDate = true;
 390
 391   // Run all passes on current SCC.
 392   for (unsigned PassNo = 0, e = getNumContainedPasses();
 393        PassNo != e; ++PassNo) {
 394     Pass *P = getContainedPass(PassNo);
 395
 396     // If we're in -debug-pass=Executions mode, construct the SCC node list,
 397     // otherwise avoid constructing this string as it is expensive.
 398     if (isPassDebuggingExecutionsOrMore()) {
 399       std::string Functions;
 400   #ifndef NDEBUG
 401       raw_string_ostream OS(Functions);
 402       for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
 403            I != E; ++I) {
 404         if (I != CurSCC.begin()) OS << ", ";
 405         (*I)->print(OS);
 406       }
 407       OS.flush();
 408   #endif
 409       dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, Functions);
 410     }
 411     dumpRequiredSet(P);
 412
 413     initializeAnalysisImpl(P);
 414
 415     // Actually run this pass on the current SCC.
 416     Changed |= RunPassOnSCC(P, CurSCC, CG,
 417                             CallGraphUpToDate, DevirtualizedCall);
 418
 419     if (Changed)
 420       dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, "");
 421     dumpPreservedSet(P);
 422
 423     verifyPreservedAnalysis(P);
 424     removeNotPreservedAnalysis(P);
 425     recordAvailableAnalysis(P);
 426     removeDeadPasses(P, "", ON_CG_MSG);
 427   }
 428
 429   // If the callgraph was left out of date (because the last pass run was a
 430   // functionpass), refresh it before we move on to the next SCC.
 431   if (!CallGraphUpToDate)
 432     DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
 433   return Changed;
 434 }
 435
 436 /// run - Execute all of the passes scheduled for execution.  Keep track of
 437 /// whether any of the passes modifies the module, and if so, return true.
 438 bool CGPassManager::runOnModule(Module &M) {
 439   CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
 440   bool Changed = doInitialization(CG);
 441
 442   // Walk the callgraph in bottom-up SCC order.
 443   scc_iterator<CallGraph*> CGI = scc_begin(&CG);
 444
 445   CallGraphSCC CurSCC(&CGI);
 446   while (!CGI.isAtEnd()) {
 447     // Copy the current SCC and increment past it so that the pass can hack
 448     // on the SCC if it wants to without invalidating our iterator.
 449     const std::vector<CallGraphNode *> &NodeVec = *CGI;
 450     CurSCC.initialize(NodeVec.data(), NodeVec.data() + NodeVec.size());
 451     ++CGI;
 452
 453     // At the top level, we run all the passes in this pass manager on the
 454     // functions in this SCC.  However, we support iterative compilation in the
 455     // case where a function pass devirtualizes a call to a function.  For
 456     // example, it is very common for a function pass (often GVN or instcombine)
 457     // to eliminate the addressing that feeds into a call.  With that improved
 458     // information, we would like the call to be an inline candidate, infer
 459     // mod-ref information etc.
 460     //
 461     // Because of this, we allow iteration up to a specified iteration count.
 462     // This only happens in the case of a devirtualized call, so we only burn
 463     // compile time in the case that we're making progress.  We also have a hard
 464     // iteration count limit in case there is crazy code.
 465     unsigned Iteration = 0;
 466     bool DevirtualizedCall = false;
 467     do {
 468       DEBUG(if (Iteration)
 469               dbgs() << "  SCCPASSMGR: Re-visiting SCC, iteration #"
 470                      << Iteration << '\n');
 471       DevirtualizedCall = false;
 472       Changed |= RunAllPassesOnSCC(CurSCC, CG, DevirtualizedCall);
 473     } while (Iteration++ < MaxIterations && DevirtualizedCall);
 474
 475     if (DevirtualizedCall)
 476       DEBUG(dbgs() << "  CGSCCPASSMGR: Stopped iteration after " << Iteration
 477                    << " times, due to -max-cg-scc-iterations\n");
 478
 479     if (Iteration > MaxSCCIterations)
 480       MaxSCCIterations = Iteration;
 481
 482   }
 483   Changed |= doFinalization(CG);
 484   return Changed;
 485 }
 486
 487
 488 /// Initialize CG
 489 bool CGPassManager::doInitialization(CallGraph &CG) {
 490   bool Changed = false;
 491   for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
 492     if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
 493       assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
 494              "Invalid CGPassManager member");
 495       Changed |= ((FPPassManager*)PM)->doInitialization(CG.getModule());
 496     } else {
 497       Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doInitialization(CG);
 498     }
 499   }
 500   return Changed;
 501 }
 502
 503 /// Finalize CG
 504 bool CGPassManager::doFinalization(CallGraph &CG) {
 505   bool Changed = false;
 506   for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
 507     if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
 508       assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
 509              "Invalid CGPassManager member");
 510       Changed |= ((FPPassManager*)PM)->doFinalization(CG.getModule());
 511     } else {
 512       Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doFinalization(CG);
 513     }
 514   }
 515   return Changed;
 516 }
 517
 518 //===----------------------------------------------------------------------===//
 519 // CallGraphSCC Implementation
 520 //===----------------------------------------------------------------------===//
 521
 522 /// ReplaceNode - This informs the SCC and the pass manager that the specified
 523 /// Old node has been deleted, and New is to be used in its place.
 524 void CallGraphSCC::ReplaceNode(CallGraphNode *Old, CallGraphNode *New) {
 525   assert(Old != New && "Should not replace node with self");
 526   for (unsigned i = 0; ; ++i) {
 527     assert(i != Nodes.size() && "Node not in SCC");
 528     if (Nodes[i] != Old) continue;
 529     Nodes[i] = New;
 530     break;
 531   }
 532
 533   // Update the active scc_iterator so that it doesn't contain dangling
 534   // pointers to the old CallGraphNode.
 535   scc_iterator<CallGraph*> *CGI = (scc_iterator<CallGraph*>*)Context;
 536   CGI->ReplaceNode(Old, New);
 537 }
 538
 539
 540 //===----------------------------------------------------------------------===//
 541 // CallGraphSCCPass Implementation
 542 //===----------------------------------------------------------------------===//
 543
 544 /// Assign pass manager to manage this pass.
 545 void CallGraphSCCPass::assignPassManager(PMStack &PMS,
 546                                          PassManagerType PreferredType) {
 547   // Find CGPassManager
 548   while (!PMS.empty() &&
 549          PMS.top()->getPassManagerType() > PMT_CallGraphPassManager)
 550     PMS.pop();
 551
 552   assert(!PMS.empty() && "Unable to handle Call Graph Pass");
 553   CGPassManager *CGP;
 554
 555   if (PMS.top()->getPassManagerType() == PMT_CallGraphPassManager)
 556     CGP = (CGPassManager*)PMS.top();
 557   else {
 558     // Create new Call Graph SCC Pass Manager if it does not exist.
 559     assert(!PMS.empty() && "Unable to create Call Graph Pass Manager");
 560     PMDataManager *PMD = PMS.top();
 561
 562     // [1] Create new Call Graph Pass Manager
 563     CGP = new CGPassManager();
 564
 565     // [2] Set up new manager's top level manager
 566     PMTopLevelManager *TPM = PMD->getTopLevelManager();
 567     TPM->addIndirectPassManager(CGP);
 568
 569     // [3] Assign manager to manage this new manager. This may create
 570     // and push new managers into PMS
 571     Pass *P = CGP;
 572     TPM->schedulePass(P);
 573
 574     // [4] Push new manager into PMS
 575     PMS.push(CGP);
 576   }
 577
 578   CGP->add(this);
 579 }
 580
 581 /// getAnalysisUsage - For this class, we declare that we require and preserve
 582 /// the call graph.  If the derived class implements this method, it should
 583 /// always explicitly call the implementation here.
 584 void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const {
 585   AU.addRequired<CallGraphWrapperPass>();
 586   AU.addPreserved<CallGraphWrapperPass>();
 587 }
 588
 589
 590 //===----------------------------------------------------------------------===//
 591 // PrintCallGraphPass Implementation
 592 //===----------------------------------------------------------------------===//
 593
 594 namespace {
 595   /// PrintCallGraphPass - Print a Module corresponding to a call graph.
 596   ///
 597   class PrintCallGraphPass : public CallGraphSCCPass {
 598     std::string Banner;
 599     raw_ostream &Out;       // raw_ostream to print on.
 600
 601   public:
 602     static char ID;
 603     PrintCallGraphPass(const std::string &B, raw_ostream &o)
 604       : CallGraphSCCPass(ID), Banner(B), Out(o) {}
 605
 606     void getAnalysisUsage(AnalysisUsage &AU) const override {
 607       AU.setPreservesAll();
 608     }
 609
 610     bool runOnSCC(CallGraphSCC &SCC) override {
 611       Out << Banner;
 612       for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
 613         if ((*I)->getFunction())
 614           (*I)->getFunction()->print(Out);
 615         else
 616           Out << "\nPrinting <null> Function\n";
 617       }
 618       return false;
 619     }
 620   };
 621
 622 } // end anonymous namespace.
 623
 624 char PrintCallGraphPass::ID = 0;
 625
 626 Pass *CallGraphSCCPass::createPrinterPass(raw_ostream &O,
 627                                           const std::string &Banner) const {
 628   return new PrintCallGraphPass(Banner, O);
 629 }
 630