CallGraphSCCPass.cpp revision b3020d7a08b951adff8d102b27aaa0bc2a7156da
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. 181 bool wasLast = I + 1 == E; 182 CGN->removeCallEdge(I); 183 if (wasLast) 184 // I is now a singular iterator, do not compare with E. 185 break; 186 E = CGN->end(); 187 continue; 188 } 189 190 assert(!CallSites.count(I->first) && 191 "Call site occurs in node multiple times"); 192 CallSites.insert(std::make_pair(I->first, I->second)); 193 ++I; 194 } 195 196 // Loop over all of the instructions in the function, getting the callsites. 197 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) 198 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { 199 CallSite CS = CallSite::get(I); 200 if (!CS.getInstruction() || isa<DbgInfoIntrinsic>(I)) continue; 201 202 // If this call site already existed in the callgraph, just verify it 203 // matches up to expectations and remove it from CallSites. 204 DenseMap<Value*, CallGraphNode*>::iterator ExistingIt = 205 CallSites.find(CS.getInstruction()); 206 if (ExistingIt != CallSites.end()) { 207 CallGraphNode *ExistingNode = ExistingIt->second; 208 209 // Remove from CallSites since we have now seen it. 210 CallSites.erase(ExistingIt); 211 212 // Verify that the callee is right. 213 if (ExistingNode->getFunction() == CS.getCalledFunction()) 214 continue; 215 216 // If we are in checking mode, we are not allowed to actually mutate 217 // the callgraph. If this is a case where we can infer that the 218 // callgraph is less precise than it could be (e.g. an indirect call 219 // site could be turned direct), don't reject it in checking mode, and 220 // don't tweak it to be more precise. 221 if (CheckingMode && CS.getCalledFunction() && 222 ExistingNode->getFunction() == 0) 223 continue; 224 225 assert(!CheckingMode && 226 "CallGraphSCCPass did not update the CallGraph correctly!"); 227 228 // If not, we either went from a direct call to indirect, indirect to 229 // direct, or direct to different direct. 230 CallGraphNode *CalleeNode; 231 if (Function *Callee = CS.getCalledFunction()) 232 CalleeNode = CG.getOrInsertFunction(Callee); 233 else 234 CalleeNode = CG.getCallsExternalNode(); 235 236 // Update the edge target in CGN. 237 for (CallGraphNode::iterator I = CGN->begin(); ; ++I) { 238 assert(I != CGN->end() && "Didn't find call entry"); 239 if (I->first == CS.getInstruction()) { 240 I->second = CalleeNode; 241 break; 242 } 243 } 244 MadeChange = true; 245 continue; 246 } 247 248 assert(!CheckingMode && 249 "CallGraphSCCPass did not update the CallGraph correctly!"); 250 251 // If the call site didn't exist in the CGN yet, add it. We assume that 252 // newly introduced call sites won't be indirect. This could be fixed 253 // in the future. 254 CallGraphNode *CalleeNode; 255 if (Function *Callee = CS.getCalledFunction()) 256 CalleeNode = CG.getOrInsertFunction(Callee); 257 else 258 CalleeNode = CG.getCallsExternalNode(); 259 260 CGN->addCalledFunction(CS, CalleeNode); 261 MadeChange = true; 262 } 263 264 // After scanning this function, if we still have entries in callsites, then 265 // they are dangling pointers. WeakVH should save us for this, so abort if 266 // this happens. 267 assert(CallSites.empty() && "Dangling pointers found in call sites map"); 268 269 // Periodically do an explicit clear to remove tombstones when processing 270 // large scc's. 271 if ((sccidx & 15) == 0) 272 CallSites.clear(); 273 } 274 275 DEBUG(if (MadeChange) { 276 errs() << "CGSCCPASSMGR: Refreshed SCC is now:\n"; 277 for (unsigned i = 0, e = CurSCC.size(); i != e; ++i) 278 CurSCC[i]->dump(); 279 } else { 280 errs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n"; 281 } 282 ); 283} 284 285/// run - Execute all of the passes scheduled for execution. Keep track of 286/// whether any of the passes modifies the module, and if so, return true. 287bool CGPassManager::runOnModule(Module &M) { 288 CallGraph &CG = getAnalysis<CallGraph>(); 289 bool Changed = doInitialization(CG); 290 291 std::vector<CallGraphNode*> CurSCC; 292 293 // Walk the callgraph in bottom-up SCC order. 294 for (scc_iterator<CallGraph*> CGI = scc_begin(&CG), E = scc_end(&CG); 295 CGI != E;) { 296 // Copy the current SCC and increment past it so that the pass can hack 297 // on the SCC if it wants to without invalidating our iterator. 298 CurSCC = *CGI; 299 ++CGI; 300 301 302 // CallGraphUpToDate - Keep track of whether the callgraph is known to be 303 // up-to-date or not. The CGSSC pass manager runs two types of passes: 304 // CallGraphSCC Passes and other random function passes. Because other 305 // random function passes are not CallGraph aware, they may clobber the 306 // call graph by introducing new calls or deleting other ones. This flag 307 // is set to false when we run a function pass so that we know to clean up 308 // the callgraph when we need to run a CGSCCPass again. 309 bool CallGraphUpToDate = true; 310 311 // Run all passes on current SCC. 312 for (unsigned PassNo = 0, e = getNumContainedPasses(); 313 PassNo != e; ++PassNo) { 314 Pass *P = getContainedPass(PassNo); 315 316 dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, ""); 317 dumpRequiredSet(P); 318 319 initializeAnalysisImpl(P); 320 321 // Actually run this pass on the current SCC. 322 Changed |= RunPassOnSCC(P, CurSCC, CG, CallGraphUpToDate); 323 324 if (Changed) 325 dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, ""); 326 dumpPreservedSet(P); 327 328 verifyPreservedAnalysis(P); 329 removeNotPreservedAnalysis(P); 330 recordAvailableAnalysis(P); 331 removeDeadPasses(P, "", ON_CG_MSG); 332 } 333 334 // If the callgraph was left out of date (because the last pass run was a 335 // functionpass), refresh it before we move on to the next SCC. 336 if (!CallGraphUpToDate) 337 RefreshCallGraph(CurSCC, CG, false); 338 } 339 Changed |= doFinalization(CG); 340 return Changed; 341} 342 343/// Initialize CG 344bool CGPassManager::doInitialization(CallGraph &CG) { 345 bool Changed = false; 346 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 347 Pass *P = getContainedPass(Index); 348 if (CallGraphSCCPass *CGSP = dynamic_cast<CallGraphSCCPass *>(P)) { 349 Changed |= CGSP->doInitialization(CG); 350 } else { 351 FPPassManager *FP = dynamic_cast<FPPassManager *>(P); 352 assert (FP && "Invalid CGPassManager member"); 353 Changed |= FP->doInitialization(CG.getModule()); 354 } 355 } 356 return Changed; 357} 358 359/// Finalize CG 360bool CGPassManager::doFinalization(CallGraph &CG) { 361 bool Changed = false; 362 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 363 Pass *P = getContainedPass(Index); 364 if (CallGraphSCCPass *CGSP = dynamic_cast<CallGraphSCCPass *>(P)) { 365 Changed |= CGSP->doFinalization(CG); 366 } else { 367 FPPassManager *FP = dynamic_cast<FPPassManager *>(P); 368 assert (FP && "Invalid CGPassManager member"); 369 Changed |= FP->doFinalization(CG.getModule()); 370 } 371 } 372 return Changed; 373} 374 375/// Assign pass manager to manage this pass. 376void CallGraphSCCPass::assignPassManager(PMStack &PMS, 377 PassManagerType PreferredType) { 378 // Find CGPassManager 379 while (!PMS.empty() && 380 PMS.top()->getPassManagerType() > PMT_CallGraphPassManager) 381 PMS.pop(); 382 383 assert (!PMS.empty() && "Unable to handle Call Graph Pass"); 384 CGPassManager *CGP = dynamic_cast<CGPassManager *>(PMS.top()); 385 386 // Create new Call Graph SCC Pass Manager if it does not exist. 387 if (!CGP) { 388 389 assert (!PMS.empty() && "Unable to create Call Graph Pass Manager"); 390 PMDataManager *PMD = PMS.top(); 391 392 // [1] Create new Call Graph Pass Manager 393 CGP = new CGPassManager(PMD->getDepth() + 1); 394 395 // [2] Set up new manager's top level manager 396 PMTopLevelManager *TPM = PMD->getTopLevelManager(); 397 TPM->addIndirectPassManager(CGP); 398 399 // [3] Assign manager to manage this new manager. This may create 400 // and push new managers into PMS 401 Pass *P = dynamic_cast<Pass *>(CGP); 402 TPM->schedulePass(P); 403 404 // [4] Push new manager into PMS 405 PMS.push(CGP); 406 } 407 408 CGP->add(this); 409} 410 411/// getAnalysisUsage - For this class, we declare that we require and preserve 412/// the call graph. If the derived class implements this method, it should 413/// always explicitly call the implementation here. 414void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const { 415 AU.addRequired<CallGraph>(); 416 AU.addPreserved<CallGraph>(); 417} 418