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/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/LegacyPassManagers.h"
25 #include "llvm/IR/LLVMContext.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"
32 #define DEBUG_TYPE "cgscc-passmgr"
34 static cl::opt<unsigned>
35 MaxIterations("max-cg-scc-iterations", cl::ReallyHidden, cl::init(4));
37 STATISTIC(MaxSCCIterations, "Maximum CGSCCPassMgr iterations on one SCC");
39 //===----------------------------------------------------------------------===//
42 /// CGPassManager manages FPPassManagers and CallGraphSCCPasses.
46 class CGPassManager : public ModulePass, public PMDataManager {
49 explicit CGPassManager()
50 : ModulePass(ID), PMDataManager() { }
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;
56 using ModulePass::doInitialization;
57 using ModulePass::doFinalization;
59 bool doInitialization(CallGraph &CG);
60 bool doFinalization(CallGraph &CG);
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();
69 const char *getPassName() const override {
70 return "CallGraph Pass Manager";
73 PMDataManager *getAsPMDataManager() override { return this; }
74 Pass *getAsPass() override { return this; }
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);
86 Pass *getContainedPass(unsigned N) {
87 assert(N < PassVector.size() && "Pass number out of range!");
88 return static_cast<Pass *>(PassVector[N]);
91 PassManagerType getPassManagerType() const override {
92 return PMT_CallGraphPassManager;
96 bool RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
97 bool &DevirtualizedCall);
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);
106 } // end anonymous namespace.
108 char CGPassManager::ID = 0;
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();
118 CallGraphSCCPass *CGSP = (CallGraphSCCPass*)P;
119 if (!CallGraphUpToDate) {
120 DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
121 CallGraphUpToDate = true;
125 TimeRegion PassTimer(getPassTimer(CGSP));
126 Changed = CGSP->runOnSCC(CurSCC);
129 // After the CGSCCPass is done, when assertions are enabled, use
130 // RefreshCallGraph to verify that the callgraph was correctly updated.
133 RefreshCallGraph(CurSCC, CG, true);
140 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
141 "Invalid CGPassManager member");
142 FPPassManager *FPP = (FPPassManager*)P;
144 // Run pass P on all functions in the current SCC.
145 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
147 if (Function *F = (*I)->getFunction()) {
148 dumpPassInfo(P, EXECUTION_MSG, ON_FUNCTION_MSG, F->getName());
150 TimeRegion PassTimer(getPassTimer(FPP));
151 Changed |= FPP->runOnFunction(*F);
153 F->getContext().yield();
157 // The function pass(es) modified the IR, they may have clobbered the
159 if (Changed && CallGraphUpToDate) {
160 DEBUG(dbgs() << "CGSCCPASSMGR: Pass Dirtied SCC: "
161 << P->getPassName() << '\n');
162 CallGraphUpToDate = false;
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.
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.
178 bool CGPassManager::RefreshCallGraph(CallGraphSCC &CurSCC,
179 CallGraph &CG, bool CheckingMode) {
180 DenseMap<Value*, CallGraphNode*> CallSites;
182 DEBUG(dbgs() << "CGSCCPASSMGR: Refreshing SCC with " << CurSCC.size()
184 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
189 bool MadeChange = false;
190 bool DevirtualizedCall = false;
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;
200 // Walk the function body looking for call sites. Sync up the call sites in
201 // CGN with those actually in the function.
203 // Keep track of the number of direct and indirect calls that were
204 // invalidated and removed.
205 unsigned NumDirectRemoved = 0, NumIndirectRemoved = 0;
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.
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) ||
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!");
224 // If this was an indirect call site, count it.
225 if (!I->second->getFunction())
226 ++NumIndirectRemoved;
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);
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
244 assert(!CallSites.count(I->first) &&
245 "Call site occurs in node multiple times");
246 CallSites.insert(std::make_pair(I->first, I->second));
250 // Loop over all of the instructions in the function, getting the callsites.
251 // Keep track of the number of direct/indirect calls added.
252 unsigned NumDirectAdded = 0, NumIndirectAdded = 0;
254 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
255 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
256 CallSite CS(cast<Value>(I));
258 Function *Callee = CS.getCalledFunction();
259 if (Callee && Callee->isIntrinsic()) continue;
261 // If this call site already existed in the callgraph, just verify it
262 // matches up to expectations and remove it from CallSites.
263 DenseMap<Value*, CallGraphNode*>::iterator ExistingIt =
264 CallSites.find(CS.getInstruction());
265 if (ExistingIt != CallSites.end()) {
266 CallGraphNode *ExistingNode = ExistingIt->second;
268 // Remove from CallSites since we have now seen it.
269 CallSites.erase(ExistingIt);
271 // Verify that the callee is right.
272 if (ExistingNode->getFunction() == CS.getCalledFunction())
275 // If we are in checking mode, we are not allowed to actually mutate
276 // the callgraph. If this is a case where we can infer that the
277 // callgraph is less precise than it could be (e.g. an indirect call
278 // site could be turned direct), don't reject it in checking mode, and
279 // don't tweak it to be more precise.
280 if (CheckingMode && CS.getCalledFunction() &&
281 ExistingNode->getFunction() == nullptr)
284 assert(!CheckingMode &&
285 "CallGraphSCCPass did not update the CallGraph correctly!");
287 // If not, we either went from a direct call to indirect, indirect to
288 // direct, or direct to different direct.
289 CallGraphNode *CalleeNode;
290 if (Function *Callee = CS.getCalledFunction()) {
291 CalleeNode = CG.getOrInsertFunction(Callee);
292 // Keep track of whether we turned an indirect call into a direct
294 if (!ExistingNode->getFunction()) {
295 DevirtualizedCall = true;
296 DEBUG(dbgs() << " CGSCCPASSMGR: Devirtualized call to '"
297 << Callee->getName() << "'\n");
300 CalleeNode = CG.getCallsExternalNode();
303 // Update the edge target in CGN.
304 CGN->replaceCallEdge(CS, CS, CalleeNode);
309 assert(!CheckingMode &&
310 "CallGraphSCCPass did not update the CallGraph correctly!");
312 // If the call site didn't exist in the CGN yet, add it.
313 CallGraphNode *CalleeNode;
314 if (Function *Callee = CS.getCalledFunction()) {
315 CalleeNode = CG.getOrInsertFunction(Callee);
318 CalleeNode = CG.getCallsExternalNode();
322 CGN->addCalledFunction(CS, CalleeNode);
326 // We scanned the old callgraph node, removing invalidated call sites and
327 // then added back newly found call sites. One thing that can happen is
328 // that an old indirect call site was deleted and replaced with a new direct
329 // call. In this case, we have devirtualized a call, and CGSCCPM would like
330 // to iteratively optimize the new code. Unfortunately, we don't really
331 // have a great way to detect when this happens. As an approximation, we
332 // just look at whether the number of indirect calls is reduced and the
333 // number of direct calls is increased. There are tons of ways to fool this
334 // (e.g. DCE'ing an indirect call and duplicating an unrelated block with a
335 // direct call) but this is close enough.
336 if (NumIndirectRemoved > NumIndirectAdded &&
337 NumDirectRemoved < NumDirectAdded)
338 DevirtualizedCall = true;
340 // After scanning this function, if we still have entries in callsites, then
341 // they are dangling pointers. WeakVH should save us for this, so abort if
343 assert(CallSites.empty() && "Dangling pointers found in call sites map");
345 // Periodically do an explicit clear to remove tombstones when processing
347 if ((FunctionNo & 15) == 15)
351 DEBUG(if (MadeChange) {
352 dbgs() << "CGSCCPASSMGR: Refreshed SCC is now:\n";
353 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
356 if (DevirtualizedCall)
357 dbgs() << "CGSCCPASSMGR: Refresh devirtualized a call!\n";
360 dbgs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n";
365 return DevirtualizedCall;
368 /// RunAllPassesOnSCC - Execute the body of the entire pass manager on the
369 /// specified SCC. This keeps track of whether a function pass devirtualizes
370 /// any calls and returns it in DevirtualizedCall.
371 bool CGPassManager::RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
372 bool &DevirtualizedCall) {
373 bool Changed = false;
375 // CallGraphUpToDate - Keep track of whether the callgraph is known to be
376 // up-to-date or not. The CGSSC pass manager runs two types of passes:
377 // CallGraphSCC Passes and other random function passes. Because other
378 // random function passes are not CallGraph aware, they may clobber the
379 // call graph by introducing new calls or deleting other ones. This flag
380 // is set to false when we run a function pass so that we know to clean up
381 // the callgraph when we need to run a CGSCCPass again.
382 bool CallGraphUpToDate = true;
384 // Run all passes on current SCC.
385 for (unsigned PassNo = 0, e = getNumContainedPasses();
386 PassNo != e; ++PassNo) {
387 Pass *P = getContainedPass(PassNo);
389 // If we're in -debug-pass=Executions mode, construct the SCC node list,
390 // otherwise avoid constructing this string as it is expensive.
391 if (isPassDebuggingExecutionsOrMore()) {
392 std::string Functions;
394 raw_string_ostream OS(Functions);
395 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
397 if (I != CurSCC.begin()) OS << ", ";
402 dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, Functions);
406 initializeAnalysisImpl(P);
408 // Actually run this pass on the current SCC.
409 Changed |= RunPassOnSCC(P, CurSCC, CG,
410 CallGraphUpToDate, DevirtualizedCall);
413 dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, "");
416 verifyPreservedAnalysis(P);
417 removeNotPreservedAnalysis(P);
418 recordAvailableAnalysis(P);
419 removeDeadPasses(P, "", ON_CG_MSG);
422 // If the callgraph was left out of date (because the last pass run was a
423 // functionpass), refresh it before we move on to the next SCC.
424 if (!CallGraphUpToDate)
425 DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
429 /// run - Execute all of the passes scheduled for execution. Keep track of
430 /// whether any of the passes modifies the module, and if so, return true.
431 bool CGPassManager::runOnModule(Module &M) {
432 CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
433 bool Changed = doInitialization(CG);
435 // Walk the callgraph in bottom-up SCC order.
436 scc_iterator<CallGraph*> CGI = scc_begin(&CG);
438 CallGraphSCC CurSCC(&CGI);
439 while (!CGI.isAtEnd()) {
440 // Copy the current SCC and increment past it so that the pass can hack
441 // on the SCC if it wants to without invalidating our iterator.
442 const std::vector<CallGraphNode *> &NodeVec = *CGI;
443 CurSCC.initialize(NodeVec.data(), NodeVec.data() + NodeVec.size());
446 // At the top level, we run all the passes in this pass manager on the
447 // functions in this SCC. However, we support iterative compilation in the
448 // case where a function pass devirtualizes a call to a function. For
449 // example, it is very common for a function pass (often GVN or instcombine)
450 // to eliminate the addressing that feeds into a call. With that improved
451 // information, we would like the call to be an inline candidate, infer
452 // mod-ref information etc.
454 // Because of this, we allow iteration up to a specified iteration count.
455 // This only happens in the case of a devirtualized call, so we only burn
456 // compile time in the case that we're making progress. We also have a hard
457 // iteration count limit in case there is crazy code.
458 unsigned Iteration = 0;
459 bool DevirtualizedCall = false;
462 dbgs() << " SCCPASSMGR: Re-visiting SCC, iteration #"
463 << Iteration << '\n');
464 DevirtualizedCall = false;
465 Changed |= RunAllPassesOnSCC(CurSCC, CG, DevirtualizedCall);
466 } while (Iteration++ < MaxIterations && DevirtualizedCall);
468 if (DevirtualizedCall)
469 DEBUG(dbgs() << " CGSCCPASSMGR: Stopped iteration after " << Iteration
470 << " times, due to -max-cg-scc-iterations\n");
472 if (Iteration > MaxSCCIterations)
473 MaxSCCIterations = Iteration;
476 Changed |= doFinalization(CG);
482 bool CGPassManager::doInitialization(CallGraph &CG) {
483 bool Changed = false;
484 for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
485 if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
486 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
487 "Invalid CGPassManager member");
488 Changed |= ((FPPassManager*)PM)->doInitialization(CG.getModule());
490 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doInitialization(CG);
497 bool CGPassManager::doFinalization(CallGraph &CG) {
498 bool Changed = false;
499 for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
500 if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
501 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
502 "Invalid CGPassManager member");
503 Changed |= ((FPPassManager*)PM)->doFinalization(CG.getModule());
505 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doFinalization(CG);
511 //===----------------------------------------------------------------------===//
512 // CallGraphSCC Implementation
513 //===----------------------------------------------------------------------===//
515 /// ReplaceNode - This informs the SCC and the pass manager that the specified
516 /// Old node has been deleted, and New is to be used in its place.
517 void CallGraphSCC::ReplaceNode(CallGraphNode *Old, CallGraphNode *New) {
518 assert(Old != New && "Should not replace node with self");
519 for (unsigned i = 0; ; ++i) {
520 assert(i != Nodes.size() && "Node not in SCC");
521 if (Nodes[i] != Old) continue;
526 // Update the active scc_iterator so that it doesn't contain dangling
527 // pointers to the old CallGraphNode.
528 scc_iterator<CallGraph*> *CGI = (scc_iterator<CallGraph*>*)Context;
529 CGI->ReplaceNode(Old, New);
533 //===----------------------------------------------------------------------===//
534 // CallGraphSCCPass Implementation
535 //===----------------------------------------------------------------------===//
537 /// Assign pass manager to manage this pass.
538 void CallGraphSCCPass::assignPassManager(PMStack &PMS,
539 PassManagerType PreferredType) {
540 // Find CGPassManager
541 while (!PMS.empty() &&
542 PMS.top()->getPassManagerType() > PMT_CallGraphPassManager)
545 assert(!PMS.empty() && "Unable to handle Call Graph Pass");
548 if (PMS.top()->getPassManagerType() == PMT_CallGraphPassManager)
549 CGP = (CGPassManager*)PMS.top();
551 // Create new Call Graph SCC Pass Manager if it does not exist.
552 assert(!PMS.empty() && "Unable to create Call Graph Pass Manager");
553 PMDataManager *PMD = PMS.top();
555 // [1] Create new Call Graph Pass Manager
556 CGP = new CGPassManager();
558 // [2] Set up new manager's top level manager
559 PMTopLevelManager *TPM = PMD->getTopLevelManager();
560 TPM->addIndirectPassManager(CGP);
562 // [3] Assign manager to manage this new manager. This may create
563 // and push new managers into PMS
565 TPM->schedulePass(P);
567 // [4] Push new manager into PMS
574 /// getAnalysisUsage - For this class, we declare that we require and preserve
575 /// the call graph. If the derived class implements this method, it should
576 /// always explicitly call the implementation here.
577 void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const {
578 AU.addRequired<CallGraphWrapperPass>();
579 AU.addPreserved<CallGraphWrapperPass>();
583 //===----------------------------------------------------------------------===//
584 // PrintCallGraphPass Implementation
585 //===----------------------------------------------------------------------===//
588 /// PrintCallGraphPass - Print a Module corresponding to a call graph.
590 class PrintCallGraphPass : public CallGraphSCCPass {
592 raw_ostream &Out; // raw_ostream to print on.
596 PrintCallGraphPass(const std::string &B, raw_ostream &o)
597 : CallGraphSCCPass(ID), Banner(B), Out(o) {}
599 void getAnalysisUsage(AnalysisUsage &AU) const override {
600 AU.setPreservesAll();
603 bool runOnSCC(CallGraphSCC &SCC) override {
605 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
606 if ((*I)->getFunction())
607 (*I)->getFunction()->print(Out);
609 Out << "Printing <null> Function";
615 } // end anonymous namespace.
617 char PrintCallGraphPass::ID = 0;
619 Pass *CallGraphSCCPass::createPrinterPass(raw_ostream &O,
620 const std::string &Banner) const {
621 return new PrintCallGraphPass(Banner, O);