CallGraphSCCPass.cpp revision d3bd0821b00f1100ab98454264c8775ace826f0d
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#define DEBUG_TYPE "cgscc-passmgr" 19#include "llvm/CallGraphSCCPass.h" 20#include "llvm/Analysis/CallGraph.h" 21#include "llvm/ADT/SCCIterator.h" 22#include "llvm/PassManagers.h" 23#include "llvm/Function.h" 24#include "llvm/Support/Debug.h" 25#include "llvm/IntrinsicInst.h" 26#include "llvm/Support/raw_ostream.h" 27using namespace llvm; 28 29//===----------------------------------------------------------------------===// 30// CGPassManager 31// 32/// CGPassManager manages FPPassManagers and CalLGraphSCCPasses. 33 34namespace { 35 36class CGPassManager : public ModulePass, public PMDataManager { 37public: 38 static char ID; 39 explicit CGPassManager(int Depth) 40 : ModulePass(&ID), PMDataManager(Depth) { } 41 42 /// run - Execute all of the passes scheduled for execution. Keep track of 43 /// whether any of the passes modifies the module, and if so, return true. 44 bool runOnModule(Module &M); 45 46 bool doInitialization(CallGraph &CG); 47 bool doFinalization(CallGraph &CG); 48 49 /// Pass Manager itself does not invalidate any analysis info. 50 void getAnalysisUsage(AnalysisUsage &Info) const { 51 // CGPassManager walks SCC and it needs CallGraph. 52 Info.addRequired<CallGraph>(); 53 Info.setPreservesAll(); 54 } 55 56 virtual const char *getPassName() const { 57 return "CallGraph Pass Manager"; 58 } 59 60 // Print passes managed by this manager 61 void dumpPassStructure(unsigned Offset) { 62 errs().indent(Offset*2) << "Call Graph SCC Pass Manager\n"; 63 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 64 Pass *P = getContainedPass(Index); 65 P->dumpPassStructure(Offset + 1); 66 dumpLastUses(P, Offset+1); 67 } 68 } 69 70 Pass *getContainedPass(unsigned N) { 71 assert(N < PassVector.size() && "Pass number out of range!"); 72 return static_cast<Pass *>(PassVector[N]); 73 } 74 75 virtual PassManagerType getPassManagerType() const { 76 return PMT_CallGraphPassManager; 77 } 78 79private: 80 bool RunPassOnSCC(Pass *P, std::vector<CallGraphNode*> &CurSCC, 81 CallGraph &CG, bool &CallGraphUpToDate); 82 void RefreshCallGraph(std::vector<CallGraphNode*> &CurSCC, CallGraph &CG, 83 bool IsCheckingMode); 84}; 85 86} // end anonymous namespace. 87 88char CGPassManager::ID = 0; 89 90bool CGPassManager::RunPassOnSCC(Pass *P, std::vector<CallGraphNode*> &CurSCC, 91 CallGraph &CG, bool &CallGraphUpToDate) { 92 bool Changed = false; 93 if (CallGraphSCCPass *CGSP = dynamic_cast<CallGraphSCCPass*>(P)) { 94 if (!CallGraphUpToDate) { 95 RefreshCallGraph(CurSCC, CG, false); 96 CallGraphUpToDate = true; 97 } 98 99 StartPassTimer(CGSP); 100 Changed = CGSP->runOnSCC(CurSCC); 101 StopPassTimer(CGSP); 102 103 // After the CGSCCPass is done, when assertions are enabled, use 104 // RefreshCallGraph to verify that the callgraph was correctly updated. 105#ifndef NDEBUG 106 if (Changed) 107 RefreshCallGraph(CurSCC, CG, true); 108#endif 109 110 return Changed; 111 } 112 113 StartPassTimer(P); 114 FPPassManager *FPP = dynamic_cast<FPPassManager *>(P); 115 assert(FPP && "Invalid CGPassManager member"); 116 117 // Run pass P on all functions in the current SCC. 118 for (unsigned i = 0, e = CurSCC.size(); i != e; ++i) { 119 if (Function *F = CurSCC[i]->getFunction()) { 120 dumpPassInfo(P, EXECUTION_MSG, ON_FUNCTION_MSG, F->getName()); 121 Changed |= FPP->runOnFunction(*F); 122 } 123 } 124 StopPassTimer(P); 125 126 // The function pass(es) modified the IR, they may have clobbered the 127 // callgraph. 128 if (Changed && CallGraphUpToDate) { 129 DEBUG(errs() << "CGSCCPASSMGR: Pass Dirtied SCC: " 130 << P->getPassName() << '\n'); 131 CallGraphUpToDate = false; 132 } 133 return Changed; 134} 135 136 137/// RefreshCallGraph - Scan the functions in the specified CFG and resync the 138/// callgraph with the call sites found in it. This is used after 139/// FunctionPasses have potentially munged the callgraph, and can be used after 140/// CallGraphSCC passes to verify that they correctly updated the callgraph. 141/// 142void CGPassManager::RefreshCallGraph(std::vector<CallGraphNode*> &CurSCC, 143 CallGraph &CG, bool CheckingMode) { 144 DenseMap<Value*, CallGraphNode*> CallSites; 145 146 DEBUG(errs() << "CGSCCPASSMGR: Refreshing SCC with " << CurSCC.size() 147 << " nodes:\n"; 148 for (unsigned i = 0, e = CurSCC.size(); i != e; ++i) 149 CurSCC[i]->dump(); 150 ); 151 152 bool MadeChange = false; 153 154 // Scan all functions in the SCC. 155 for (unsigned sccidx = 0, e = CurSCC.size(); sccidx != e; ++sccidx) { 156 CallGraphNode *CGN = CurSCC[sccidx]; 157 Function *F = CGN->getFunction(); 158 if (F == 0 || F->isDeclaration()) continue; 159 160 // Walk the function body looking for call sites. Sync up the call sites in 161 // CGN with those actually in the function. 162 163 // Get the set of call sites currently in the function. 164 for (CallGraphNode::iterator I = CGN->begin(), E = CGN->end(); I != E; ) { 165 // If this call site is null, then the function pass deleted the call 166 // entirely and the WeakVH nulled it out. 167 if (I->first == 0 || 168 // If we've already seen this call site, then the FunctionPass RAUW'd 169 // one call with another, which resulted in two "uses" in the edge 170 // list of the same call. 171 CallSites.count(I->first) || 172 173 // If the call edge is not from a call or invoke, then the function 174 // pass RAUW'd a call with another value. This can happen when 175 // constant folding happens of well known functions etc. 176 CallSite::get(I->first).getInstruction() == 0) { 177 assert(!CheckingMode && 178 "CallGraphSCCPass did not update the CallGraph correctly!"); 179 180 // Just remove the edge from the set of callees, keep track of whether 181 // I points to the last element of the vector. 182 bool WasLast = I + 1 == E; 183 CGN->removeCallEdge(I); 184 185 // If I pointed to the last element of the vector, we have to bail out: 186 // iterator checking rejects comparisons of the resultant pointer with 187 // end. 188 if (WasLast) 189 break; 190 E = CGN->end(); 191 continue; 192 } 193 194 assert(!CallSites.count(I->first) && 195 "Call site occurs in node multiple times"); 196 CallSites.insert(std::make_pair(I->first, I->second)); 197 ++I; 198 } 199 200 // Loop over all of the instructions in the function, getting the callsites. 201 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) 202 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 203 CallSite CS = CallSite::get(I); 204 if (!CS.getInstruction() || isa<DbgInfoIntrinsic>(I)) continue; 205 206 // If this call site already existed in the callgraph, just verify it 207 // matches up to expectations and remove it from CallSites. 208 DenseMap<Value*, CallGraphNode*>::iterator ExistingIt = 209 CallSites.find(CS.getInstruction()); 210 if (ExistingIt != CallSites.end()) { 211 CallGraphNode *ExistingNode = ExistingIt->second; 212 213 // Remove from CallSites since we have now seen it. 214 CallSites.erase(ExistingIt); 215 216 // Verify that the callee is right. 217 if (ExistingNode->getFunction() == CS.getCalledFunction()) 218 continue; 219 220 // If we are in checking mode, we are not allowed to actually mutate 221 // the callgraph. If this is a case where we can infer that the 222 // callgraph is less precise than it could be (e.g. an indirect call 223 // site could be turned direct), don't reject it in checking mode, and 224 // don't tweak it to be more precise. 225 if (CheckingMode && CS.getCalledFunction() && 226 ExistingNode->getFunction() == 0) 227 continue; 228 229 assert(!CheckingMode && 230 "CallGraphSCCPass did not update the CallGraph correctly!"); 231 232 // If not, we either went from a direct call to indirect, indirect to 233 // direct, or direct to different direct. 234 CallGraphNode *CalleeNode; 235 if (Function *Callee = CS.getCalledFunction()) 236 CalleeNode = CG.getOrInsertFunction(Callee); 237 else 238 CalleeNode = CG.getCallsExternalNode(); 239 240 // Update the edge target in CGN. 241 for (CallGraphNode::iterator I = CGN->begin(); ; ++I) { 242 assert(I != CGN->end() && "Didn't find call entry"); 243 if (I->first == CS.getInstruction()) { 244 I->second = CalleeNode; 245 break; 246 } 247 } 248 MadeChange = true; 249 continue; 250 } 251 252 assert(!CheckingMode && 253 "CallGraphSCCPass did not update the CallGraph correctly!"); 254 255 // If the call site didn't exist in the CGN yet, add it. We assume that 256 // newly introduced call sites won't be indirect. This could be fixed 257 // in the future. 258 CallGraphNode *CalleeNode; 259 if (Function *Callee = CS.getCalledFunction()) 260 CalleeNode = CG.getOrInsertFunction(Callee); 261 else 262 CalleeNode = CG.getCallsExternalNode(); 263 264 CGN->addCalledFunction(CS, CalleeNode); 265 MadeChange = true; 266 } 267 268 // After scanning this function, if we still have entries in callsites, then 269 // they are dangling pointers. WeakVH should save us for this, so abort if 270 // this happens. 271 assert(CallSites.empty() && "Dangling pointers found in call sites map"); 272 273 // Periodically do an explicit clear to remove tombstones when processing 274 // large scc's. 275 if ((sccidx & 15) == 0) 276 CallSites.clear(); 277 } 278 279 DEBUG(if (MadeChange) { 280 errs() << "CGSCCPASSMGR: Refreshed SCC is now:\n"; 281 for (unsigned i = 0, e = CurSCC.size(); i != e; ++i) 282 CurSCC[i]->dump(); 283 } else { 284 errs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n"; 285 } 286 ); 287} 288 289/// run - Execute all of the passes scheduled for execution. Keep track of 290/// whether any of the passes modifies the module, and if so, return true. 291bool CGPassManager::runOnModule(Module &M) { 292 CallGraph &CG = getAnalysis<CallGraph>(); 293 bool Changed = doInitialization(CG); 294 295 std::vector<CallGraphNode*> CurSCC; 296 297 // Walk the callgraph in bottom-up SCC order. 298 for (scc_iterator<CallGraph*> CGI = scc_begin(&CG), E = scc_end(&CG); 299 CGI != E;) { 300 // Copy the current SCC and increment past it so that the pass can hack 301 // on the SCC if it wants to without invalidating our iterator. 302 CurSCC = *CGI; 303 ++CGI; 304 305 306 // CallGraphUpToDate - Keep track of whether the callgraph is known to be 307 // up-to-date or not. The CGSSC pass manager runs two types of passes: 308 // CallGraphSCC Passes and other random function passes. Because other 309 // random function passes are not CallGraph aware, they may clobber the 310 // call graph by introducing new calls or deleting other ones. This flag 311 // is set to false when we run a function pass so that we know to clean up 312 // the callgraph when we need to run a CGSCCPass again. 313 bool CallGraphUpToDate = true; 314 315 // Run all passes on current SCC. 316 for (unsigned PassNo = 0, e = getNumContainedPasses(); 317 PassNo != e; ++PassNo) { 318 Pass *P = getContainedPass(PassNo); 319 320 dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, ""); 321 dumpRequiredSet(P); 322 323 initializeAnalysisImpl(P); 324 325 // Actually run this pass on the current SCC. 326 Changed |= RunPassOnSCC(P, CurSCC, CG, CallGraphUpToDate); 327 328 if (Changed) 329 dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, ""); 330 dumpPreservedSet(P); 331 332 verifyPreservedAnalysis(P); 333 removeNotPreservedAnalysis(P); 334 recordAvailableAnalysis(P); 335 removeDeadPasses(P, "", ON_CG_MSG); 336 } 337 338 // If the callgraph was left out of date (because the last pass run was a 339 // functionpass), refresh it before we move on to the next SCC. 340 if (!CallGraphUpToDate) 341 RefreshCallGraph(CurSCC, CG, false); 342 } 343 Changed |= doFinalization(CG); 344 return Changed; 345} 346 347/// Initialize CG 348bool CGPassManager::doInitialization(CallGraph &CG) { 349 bool Changed = false; 350 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 351 Pass *P = getContainedPass(Index); 352 if (CallGraphSCCPass *CGSP = dynamic_cast<CallGraphSCCPass *>(P)) { 353 Changed |= CGSP->doInitialization(CG); 354 } else { 355 FPPassManager *FP = dynamic_cast<FPPassManager *>(P); 356 assert (FP && "Invalid CGPassManager member"); 357 Changed |= FP->doInitialization(CG.getModule()); 358 } 359 } 360 return Changed; 361} 362 363/// Finalize CG 364bool CGPassManager::doFinalization(CallGraph &CG) { 365 bool Changed = false; 366 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 367 Pass *P = getContainedPass(Index); 368 if (CallGraphSCCPass *CGSP = dynamic_cast<CallGraphSCCPass *>(P)) { 369 Changed |= CGSP->doFinalization(CG); 370 } else { 371 FPPassManager *FP = dynamic_cast<FPPassManager *>(P); 372 assert (FP && "Invalid CGPassManager member"); 373 Changed |= FP->doFinalization(CG.getModule()); 374 } 375 } 376 return Changed; 377} 378 379/// Assign pass manager to manage this pass. 380void CallGraphSCCPass::assignPassManager(PMStack &PMS, 381 PassManagerType PreferredType) { 382 // Find CGPassManager 383 while (!PMS.empty() && 384 PMS.top()->getPassManagerType() > PMT_CallGraphPassManager) 385 PMS.pop(); 386 387 assert (!PMS.empty() && "Unable to handle Call Graph Pass"); 388 CGPassManager *CGP = dynamic_cast<CGPassManager *>(PMS.top()); 389 390 // Create new Call Graph SCC Pass Manager if it does not exist. 391 if (!CGP) { 392 393 assert (!PMS.empty() && "Unable to create Call Graph Pass Manager"); 394 PMDataManager *PMD = PMS.top(); 395 396 // [1] Create new Call Graph Pass Manager 397 CGP = new CGPassManager(PMD->getDepth() + 1); 398 399 // [2] Set up new manager's top level manager 400 PMTopLevelManager *TPM = PMD->getTopLevelManager(); 401 TPM->addIndirectPassManager(CGP); 402 403 // [3] Assign manager to manage this new manager. This may create 404 // and push new managers into PMS 405 Pass *P = dynamic_cast<Pass *>(CGP); 406 TPM->schedulePass(P); 407 408 // [4] Push new manager into PMS 409 PMS.push(CGP); 410 } 411 412 CGP->add(this); 413} 414 415/// getAnalysisUsage - For this class, we declare that we require and preserve 416/// the call graph. If the derived class implements this method, it should 417/// always explicitly call the implementation here. 418void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const { 419 AU.addRequired<CallGraph>(); 420 AU.addPreserved<CallGraph>(); 421} 422