1 //===- CallGraphSCCPass.cpp - Pass that operates BU on call graph ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
16 //===----------------------------------------------------------------------===//
18 #include "llvm/Analysis/CallGraphSCCPass.h"
19 #include "llvm/ADT/DenseMap.h"
20 #include "llvm/ADT/SCCIterator.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/Analysis/CallGraph.h"
23 #include "llvm/IR/CallSite.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/IR/Intrinsics.h"
26 #include "llvm/IR/LLVMContext.h"
27 #include "llvm/IR/LegacyPassManagers.h"
28 #include "llvm/IR/Module.h"
29 #include "llvm/IR/OptBisect.h"
30 #include "llvm/Pass.h"
31 #include "llvm/Support/CommandLine.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/Support/Timer.h"
34 #include "llvm/Support/raw_ostream.h"
42 #define DEBUG_TYPE "cgscc-passmgr"
44 static cl::opt<unsigned>
45 MaxIterations("max-cg-scc-iterations", cl::ReallyHidden, cl::init(4));
47 STATISTIC(MaxSCCIterations, "Maximum CGSCCPassMgr iterations on one SCC");
49 //===----------------------------------------------------------------------===//
52 /// CGPassManager manages FPPassManagers and CallGraphSCCPasses.
56 class CGPassManager : public ModulePass, public PMDataManager {
60 explicit CGPassManager() : ModulePass(ID), PMDataManager() {}
62 /// Execute all of the passes scheduled for execution. Keep track of
63 /// whether any of the passes modifies the module, and if so, return true.
64 bool runOnModule(Module &M) override;
66 using ModulePass::doInitialization;
67 using ModulePass::doFinalization;
69 bool doInitialization(CallGraph &CG);
70 bool doFinalization(CallGraph &CG);
72 /// Pass Manager itself does not invalidate any analysis info.
73 void getAnalysisUsage(AnalysisUsage &Info) const override {
74 // CGPassManager walks SCC and it needs CallGraph.
75 Info.addRequired<CallGraphWrapperPass>();
76 Info.setPreservesAll();
79 StringRef getPassName() const override { return "CallGraph Pass Manager"; }
81 PMDataManager *getAsPMDataManager() override { return this; }
82 Pass *getAsPass() override { return this; }
84 // Print passes managed by this manager
85 void dumpPassStructure(unsigned Offset) override {
86 errs().indent(Offset*2) << "Call Graph SCC Pass Manager\n";
87 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
88 Pass *P = getContainedPass(Index);
89 P->dumpPassStructure(Offset + 1);
90 dumpLastUses(P, Offset+1);
94 Pass *getContainedPass(unsigned N) {
95 assert(N < PassVector.size() && "Pass number out of range!");
96 return static_cast<Pass *>(PassVector[N]);
99 PassManagerType getPassManagerType() const override {
100 return PMT_CallGraphPassManager;
104 bool RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
105 bool &DevirtualizedCall);
107 bool RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
108 CallGraph &CG, bool &CallGraphUpToDate,
109 bool &DevirtualizedCall);
110 bool RefreshCallGraph(const CallGraphSCC &CurSCC, CallGraph &CG,
111 bool IsCheckingMode);
114 } // end anonymous namespace.
116 char CGPassManager::ID = 0;
118 bool CGPassManager::RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
119 CallGraph &CG, bool &CallGraphUpToDate,
120 bool &DevirtualizedCall) {
121 bool Changed = false;
122 PMDataManager *PM = P->getAsPMDataManager();
123 Module &M = CG.getModule();
126 CallGraphSCCPass *CGSP = (CallGraphSCCPass*)P;
127 if (!CallGraphUpToDate) {
128 DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
129 CallGraphUpToDate = true;
133 unsigned InstrCount = 0;
134 bool EmitICRemark = M.shouldEmitInstrCountChangedRemark();
135 TimeRegion PassTimer(getPassTimer(CGSP));
137 InstrCount = initSizeRemarkInfo(M);
138 Changed = CGSP->runOnSCC(CurSCC);
140 // If the pass modified the module, it may have modified the instruction
141 // count of the module. Try emitting a remark.
143 emitInstrCountChangedRemark(P, M, InstrCount);
146 // After the CGSCCPass is done, when assertions are enabled, use
147 // RefreshCallGraph to verify that the callgraph was correctly updated.
150 RefreshCallGraph(CurSCC, CG, true);
156 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
157 "Invalid CGPassManager member");
158 FPPassManager *FPP = (FPPassManager*)P;
160 // Run pass P on all functions in the current SCC.
161 for (CallGraphNode *CGN : CurSCC) {
162 if (Function *F = CGN->getFunction()) {
163 dumpPassInfo(P, EXECUTION_MSG, ON_FUNCTION_MSG, F->getName());
165 TimeRegion PassTimer(getPassTimer(FPP));
166 Changed |= FPP->runOnFunction(*F);
168 F->getContext().yield();
172 // The function pass(es) modified the IR, they may have clobbered the
174 if (Changed && CallGraphUpToDate) {
175 LLVM_DEBUG(dbgs() << "CGSCCPASSMGR: Pass Dirtied SCC: " << P->getPassName()
177 CallGraphUpToDate = false;
182 /// Scan the functions in the specified CFG and resync the
183 /// callgraph with the call sites found in it. This is used after
184 /// FunctionPasses have potentially munged the callgraph, and can be used after
185 /// CallGraphSCC passes to verify that they correctly updated the callgraph.
187 /// This function returns true if it devirtualized an existing function call,
188 /// meaning it turned an indirect call into a direct call. This happens when
189 /// a function pass like GVN optimizes away stuff feeding the indirect call.
190 /// This never happens in checking mode.
191 bool CGPassManager::RefreshCallGraph(const CallGraphSCC &CurSCC, CallGraph &CG,
193 DenseMap<Value*, CallGraphNode*> CallSites;
195 LLVM_DEBUG(dbgs() << "CGSCCPASSMGR: Refreshing SCC with " << CurSCC.size()
197 for (CallGraphNode *CGN
198 : CurSCC) CGN->dump(););
200 bool MadeChange = false;
201 bool DevirtualizedCall = false;
203 // Scan all functions in the SCC.
204 unsigned FunctionNo = 0;
205 for (CallGraphSCC::iterator SCCIdx = CurSCC.begin(), E = CurSCC.end();
206 SCCIdx != E; ++SCCIdx, ++FunctionNo) {
207 CallGraphNode *CGN = *SCCIdx;
208 Function *F = CGN->getFunction();
209 if (!F || F->isDeclaration()) continue;
211 // Walk the function body looking for call sites. Sync up the call sites in
212 // CGN with those actually in the function.
214 // Keep track of the number of direct and indirect calls that were
215 // invalidated and removed.
216 unsigned NumDirectRemoved = 0, NumIndirectRemoved = 0;
218 // Get the set of call sites currently in the function.
219 for (CallGraphNode::iterator I = CGN->begin(), E = CGN->end(); I != E; ) {
220 // If this call site is null, then the function pass deleted the call
221 // entirely and the WeakTrackingVH nulled it out.
223 // If we've already seen this call site, then the FunctionPass RAUW'd
224 // one call with another, which resulted in two "uses" in the edge
225 // list of the same call.
226 CallSites.count(I->first) ||
228 // If the call edge is not from a call or invoke, or it is a
229 // instrinsic call, then the function pass RAUW'd a call with
230 // another value. This can happen when constant folding happens
231 // of well known functions etc.
232 !CallSite(I->first) ||
233 (CallSite(I->first).getCalledFunction() &&
234 CallSite(I->first).getCalledFunction()->isIntrinsic() &&
236 CallSite(I->first).getCalledFunction()->getIntrinsicID()))) {
237 assert(!CheckingMode &&
238 "CallGraphSCCPass did not update the CallGraph correctly!");
240 // If this was an indirect call site, count it.
241 if (!I->second->getFunction())
242 ++NumIndirectRemoved;
246 // Just remove the edge from the set of callees, keep track of whether
247 // I points to the last element of the vector.
248 bool WasLast = I + 1 == E;
249 CGN->removeCallEdge(I);
251 // If I pointed to the last element of the vector, we have to bail out:
252 // iterator checking rejects comparisons of the resultant pointer with
260 assert(!CallSites.count(I->first) &&
261 "Call site occurs in node multiple times");
263 CallSite CS(I->first);
265 Function *Callee = CS.getCalledFunction();
266 // Ignore intrinsics because they're not really function calls.
267 if (!Callee || !(Callee->isIntrinsic()))
268 CallSites.insert(std::make_pair(I->first, I->second));
273 // Loop over all of the instructions in the function, getting the callsites.
274 // Keep track of the number of direct/indirect calls added.
275 unsigned NumDirectAdded = 0, NumIndirectAdded = 0;
277 for (BasicBlock &BB : *F)
278 for (Instruction &I : BB) {
281 Function *Callee = CS.getCalledFunction();
282 if (Callee && Callee->isIntrinsic()) continue;
284 // If this call site already existed in the callgraph, just verify it
285 // matches up to expectations and remove it from CallSites.
286 DenseMap<Value*, CallGraphNode*>::iterator ExistingIt =
287 CallSites.find(CS.getInstruction());
288 if (ExistingIt != CallSites.end()) {
289 CallGraphNode *ExistingNode = ExistingIt->second;
291 // Remove from CallSites since we have now seen it.
292 CallSites.erase(ExistingIt);
294 // Verify that the callee is right.
295 if (ExistingNode->getFunction() == CS.getCalledFunction())
298 // If we are in checking mode, we are not allowed to actually mutate
299 // the callgraph. If this is a case where we can infer that the
300 // callgraph is less precise than it could be (e.g. an indirect call
301 // site could be turned direct), don't reject it in checking mode, and
302 // don't tweak it to be more precise.
303 if (CheckingMode && CS.getCalledFunction() &&
304 ExistingNode->getFunction() == nullptr)
307 assert(!CheckingMode &&
308 "CallGraphSCCPass did not update the CallGraph correctly!");
310 // If not, we either went from a direct call to indirect, indirect to
311 // direct, or direct to different direct.
312 CallGraphNode *CalleeNode;
313 if (Function *Callee = CS.getCalledFunction()) {
314 CalleeNode = CG.getOrInsertFunction(Callee);
315 // Keep track of whether we turned an indirect call into a direct
317 if (!ExistingNode->getFunction()) {
318 DevirtualizedCall = true;
319 LLVM_DEBUG(dbgs() << " CGSCCPASSMGR: Devirtualized call to '"
320 << Callee->getName() << "'\n");
323 CalleeNode = CG.getCallsExternalNode();
326 // Update the edge target in CGN.
327 CGN->replaceCallEdge(CS, CS, CalleeNode);
332 assert(!CheckingMode &&
333 "CallGraphSCCPass did not update the CallGraph correctly!");
335 // If the call site didn't exist in the CGN yet, add it.
336 CallGraphNode *CalleeNode;
337 if (Function *Callee = CS.getCalledFunction()) {
338 CalleeNode = CG.getOrInsertFunction(Callee);
341 CalleeNode = CG.getCallsExternalNode();
345 CGN->addCalledFunction(CS, CalleeNode);
349 // We scanned the old callgraph node, removing invalidated call sites and
350 // then added back newly found call sites. One thing that can happen is
351 // that an old indirect call site was deleted and replaced with a new direct
352 // call. In this case, we have devirtualized a call, and CGSCCPM would like
353 // to iteratively optimize the new code. Unfortunately, we don't really
354 // have a great way to detect when this happens. As an approximation, we
355 // just look at whether the number of indirect calls is reduced and the
356 // number of direct calls is increased. There are tons of ways to fool this
357 // (e.g. DCE'ing an indirect call and duplicating an unrelated block with a
358 // direct call) but this is close enough.
359 if (NumIndirectRemoved > NumIndirectAdded &&
360 NumDirectRemoved < NumDirectAdded)
361 DevirtualizedCall = true;
363 // After scanning this function, if we still have entries in callsites, then
364 // they are dangling pointers. WeakTrackingVH should save us for this, so
367 assert(CallSites.empty() && "Dangling pointers found in call sites map");
369 // Periodically do an explicit clear to remove tombstones when processing
371 if ((FunctionNo & 15) == 15)
375 LLVM_DEBUG(if (MadeChange) {
376 dbgs() << "CGSCCPASSMGR: Refreshed SCC is now:\n";
377 for (CallGraphNode *CGN : CurSCC)
379 if (DevirtualizedCall)
380 dbgs() << "CGSCCPASSMGR: Refresh devirtualized a call!\n";
382 dbgs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n";
386 return DevirtualizedCall;
389 /// Execute the body of the entire pass manager on the specified SCC.
390 /// This keeps track of whether a function pass devirtualizes
391 /// any calls and returns it in DevirtualizedCall.
392 bool CGPassManager::RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
393 bool &DevirtualizedCall) {
394 bool Changed = false;
396 // Keep track of whether the callgraph is known to be up-to-date or not.
397 // The CGSSC pass manager runs two types of passes:
398 // CallGraphSCC Passes and other random function passes. Because other
399 // random function passes are not CallGraph aware, they may clobber the
400 // call graph by introducing new calls or deleting other ones. This flag
401 // is set to false when we run a function pass so that we know to clean up
402 // the callgraph when we need to run a CGSCCPass again.
403 bool CallGraphUpToDate = true;
405 // Run all passes on current SCC.
406 for (unsigned PassNo = 0, e = getNumContainedPasses();
407 PassNo != e; ++PassNo) {
408 Pass *P = getContainedPass(PassNo);
410 // If we're in -debug-pass=Executions mode, construct the SCC node list,
411 // otherwise avoid constructing this string as it is expensive.
412 if (isPassDebuggingExecutionsOrMore()) {
413 std::string Functions;
415 raw_string_ostream OS(Functions);
416 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
418 if (I != CurSCC.begin()) OS << ", ";
423 dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, Functions);
427 initializeAnalysisImpl(P);
429 // Actually run this pass on the current SCC.
430 Changed |= RunPassOnSCC(P, CurSCC, CG,
431 CallGraphUpToDate, DevirtualizedCall);
434 dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, "");
437 verifyPreservedAnalysis(P);
438 removeNotPreservedAnalysis(P);
439 recordAvailableAnalysis(P);
440 removeDeadPasses(P, "", ON_CG_MSG);
443 // If the callgraph was left out of date (because the last pass run was a
444 // functionpass), refresh it before we move on to the next SCC.
445 if (!CallGraphUpToDate)
446 DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
450 /// Execute all of the passes scheduled for execution. Keep track of
451 /// whether any of the passes modifies the module, and if so, return true.
452 bool CGPassManager::runOnModule(Module &M) {
453 CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
454 bool Changed = doInitialization(CG);
456 // Walk the callgraph in bottom-up SCC order.
457 scc_iterator<CallGraph*> CGI = scc_begin(&CG);
459 CallGraphSCC CurSCC(CG, &CGI);
460 while (!CGI.isAtEnd()) {
461 // Copy the current SCC and increment past it so that the pass can hack
462 // on the SCC if it wants to without invalidating our iterator.
463 const std::vector<CallGraphNode *> &NodeVec = *CGI;
464 CurSCC.initialize(NodeVec);
467 // At the top level, we run all the passes in this pass manager on the
468 // functions in this SCC. However, we support iterative compilation in the
469 // case where a function pass devirtualizes a call to a function. For
470 // example, it is very common for a function pass (often GVN or instcombine)
471 // to eliminate the addressing that feeds into a call. With that improved
472 // information, we would like the call to be an inline candidate, infer
473 // mod-ref information etc.
475 // Because of this, we allow iteration up to a specified iteration count.
476 // This only happens in the case of a devirtualized call, so we only burn
477 // compile time in the case that we're making progress. We also have a hard
478 // iteration count limit in case there is crazy code.
479 unsigned Iteration = 0;
480 bool DevirtualizedCall = false;
482 LLVM_DEBUG(if (Iteration) dbgs()
483 << " SCCPASSMGR: Re-visiting SCC, iteration #" << Iteration
485 DevirtualizedCall = false;
486 Changed |= RunAllPassesOnSCC(CurSCC, CG, DevirtualizedCall);
487 } while (Iteration++ < MaxIterations && DevirtualizedCall);
489 if (DevirtualizedCall)
490 LLVM_DEBUG(dbgs() << " CGSCCPASSMGR: Stopped iteration after "
492 << " times, due to -max-cg-scc-iterations\n");
494 MaxSCCIterations.updateMax(Iteration);
496 Changed |= doFinalization(CG);
501 bool CGPassManager::doInitialization(CallGraph &CG) {
502 bool Changed = false;
503 for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
504 if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
505 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
506 "Invalid CGPassManager member");
507 Changed |= ((FPPassManager*)PM)->doInitialization(CG.getModule());
509 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doInitialization(CG);
516 bool CGPassManager::doFinalization(CallGraph &CG) {
517 bool Changed = false;
518 for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
519 if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
520 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
521 "Invalid CGPassManager member");
522 Changed |= ((FPPassManager*)PM)->doFinalization(CG.getModule());
524 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doFinalization(CG);
530 //===----------------------------------------------------------------------===//
531 // CallGraphSCC Implementation
532 //===----------------------------------------------------------------------===//
534 /// This informs the SCC and the pass manager that the specified
535 /// Old node has been deleted, and New is to be used in its place.
536 void CallGraphSCC::ReplaceNode(CallGraphNode *Old, CallGraphNode *New) {
537 assert(Old != New && "Should not replace node with self");
538 for (unsigned i = 0; ; ++i) {
539 assert(i != Nodes.size() && "Node not in SCC");
540 if (Nodes[i] != Old) continue;
545 // Update the active scc_iterator so that it doesn't contain dangling
546 // pointers to the old CallGraphNode.
547 scc_iterator<CallGraph*> *CGI = (scc_iterator<CallGraph*>*)Context;
548 CGI->ReplaceNode(Old, New);
551 //===----------------------------------------------------------------------===//
552 // CallGraphSCCPass Implementation
553 //===----------------------------------------------------------------------===//
555 /// Assign pass manager to manage this pass.
556 void CallGraphSCCPass::assignPassManager(PMStack &PMS,
557 PassManagerType PreferredType) {
558 // Find CGPassManager
559 while (!PMS.empty() &&
560 PMS.top()->getPassManagerType() > PMT_CallGraphPassManager)
563 assert(!PMS.empty() && "Unable to handle Call Graph Pass");
566 if (PMS.top()->getPassManagerType() == PMT_CallGraphPassManager)
567 CGP = (CGPassManager*)PMS.top();
569 // Create new Call Graph SCC Pass Manager if it does not exist.
570 assert(!PMS.empty() && "Unable to create Call Graph Pass Manager");
571 PMDataManager *PMD = PMS.top();
573 // [1] Create new Call Graph Pass Manager
574 CGP = new CGPassManager();
576 // [2] Set up new manager's top level manager
577 PMTopLevelManager *TPM = PMD->getTopLevelManager();
578 TPM->addIndirectPassManager(CGP);
580 // [3] Assign manager to manage this new manager. This may create
581 // and push new managers into PMS
583 TPM->schedulePass(P);
585 // [4] Push new manager into PMS
592 /// For this class, we declare that we require and preserve the call graph.
593 /// If the derived class implements this method, it should
594 /// always explicitly call the implementation here.
595 void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const {
596 AU.addRequired<CallGraphWrapperPass>();
597 AU.addPreserved<CallGraphWrapperPass>();
600 //===----------------------------------------------------------------------===//
601 // PrintCallGraphPass Implementation
602 //===----------------------------------------------------------------------===//
606 /// PrintCallGraphPass - Print a Module corresponding to a call graph.
608 class PrintCallGraphPass : public CallGraphSCCPass {
610 raw_ostream &OS; // raw_ostream to print on.
615 PrintCallGraphPass(const std::string &B, raw_ostream &OS)
616 : CallGraphSCCPass(ID), Banner(B), OS(OS) {}
618 void getAnalysisUsage(AnalysisUsage &AU) const override {
619 AU.setPreservesAll();
622 bool runOnSCC(CallGraphSCC &SCC) override {
623 bool BannerPrinted = false;
624 auto PrintBannerOnce = [&] () {
628 BannerPrinted = true;
630 for (CallGraphNode *CGN : SCC) {
631 if (Function *F = CGN->getFunction()) {
632 if (!F->isDeclaration() && isFunctionInPrintList(F->getName())) {
636 } else if (isFunctionInPrintList("*")) {
638 OS << "\nPrinting <null> Function\n";
644 StringRef getPassName() const override { return "Print CallGraph IR"; }
647 } // end anonymous namespace.
649 char PrintCallGraphPass::ID = 0;
651 Pass *CallGraphSCCPass::createPrinterPass(raw_ostream &OS,
652 const std::string &Banner) const {
653 return new PrintCallGraphPass(Banner, OS);
656 bool CallGraphSCCPass::skipSCC(CallGraphSCC &SCC) const {
657 return !SCC.getCallGraph().getModule()
660 .shouldRunPass(this, SCC);
663 char DummyCGSCCPass::ID = 0;
665 INITIALIZE_PASS(DummyCGSCCPass, "DummyCGSCCPass", "DummyCGSCCPass", false,