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 #define DEBUG_TYPE "cgscc-passmgr"
19 #include "llvm/CallGraphSCCPass.h"
20 #include "llvm/IntrinsicInst.h"
21 #include "llvm/Function.h"
22 #include "llvm/PassManagers.h"
23 #include "llvm/Analysis/CallGraph.h"
24 #include "llvm/ADT/SCCIterator.h"
25 #include "llvm/ADT/Statistic.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 static cl::opt<unsigned>
33 MaxIterations("max-cg-scc-iterations", cl::ReallyHidden, cl::init(4));
35 STATISTIC(MaxSCCIterations, "Maximum CGSCCPassMgr iterations on one SCC");
37 //===----------------------------------------------------------------------===//
40 /// CGPassManager manages FPPassManagers and CallGraphSCCPasses.
44 class CGPassManager : public ModulePass, public PMDataManager {
47 explicit CGPassManager()
48 : ModulePass(ID), PMDataManager() { }
50 /// run - Execute all of the passes scheduled for execution. Keep track of
51 /// whether any of the passes modifies the module, and if so, return true.
52 bool runOnModule(Module &M);
54 bool doInitialization(CallGraph &CG);
55 bool doFinalization(CallGraph &CG);
57 /// Pass Manager itself does not invalidate any analysis info.
58 void getAnalysisUsage(AnalysisUsage &Info) const {
59 // CGPassManager walks SCC and it needs CallGraph.
60 Info.addRequired<CallGraph>();
61 Info.setPreservesAll();
64 virtual const char *getPassName() const {
65 return "CallGraph Pass Manager";
68 virtual PMDataManager *getAsPMDataManager() { return this; }
69 virtual Pass *getAsPass() { return this; }
71 // Print passes managed by this manager
72 void dumpPassStructure(unsigned Offset) {
73 errs().indent(Offset*2) << "Call Graph SCC Pass Manager\n";
74 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
75 Pass *P = getContainedPass(Index);
76 P->dumpPassStructure(Offset + 1);
77 dumpLastUses(P, Offset+1);
81 Pass *getContainedPass(unsigned N) {
82 assert(N < PassVector.size() && "Pass number out of range!");
83 return static_cast<Pass *>(PassVector[N]);
86 virtual PassManagerType getPassManagerType() const {
87 return PMT_CallGraphPassManager;
91 bool RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
92 bool &DevirtualizedCall);
94 bool RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
95 CallGraph &CG, bool &CallGraphUpToDate,
96 bool &DevirtualizedCall);
97 bool RefreshCallGraph(CallGraphSCC &CurSCC, CallGraph &CG,
101 } // end anonymous namespace.
103 char CGPassManager::ID = 0;
106 bool CGPassManager::RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
107 CallGraph &CG, bool &CallGraphUpToDate,
108 bool &DevirtualizedCall) {
109 bool Changed = false;
110 PMDataManager *PM = P->getAsPMDataManager();
113 CallGraphSCCPass *CGSP = (CallGraphSCCPass*)P;
114 if (!CallGraphUpToDate) {
115 DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
116 CallGraphUpToDate = true;
120 TimeRegion PassTimer(getPassTimer(CGSP));
121 Changed = CGSP->runOnSCC(CurSCC);
124 // After the CGSCCPass is done, when assertions are enabled, use
125 // RefreshCallGraph to verify that the callgraph was correctly updated.
128 RefreshCallGraph(CurSCC, CG, true);
135 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
136 "Invalid CGPassManager member");
137 FPPassManager *FPP = (FPPassManager*)P;
139 // Run pass P on all functions in the current SCC.
140 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
142 if (Function *F = (*I)->getFunction()) {
143 dumpPassInfo(P, EXECUTION_MSG, ON_FUNCTION_MSG, F->getName());
144 TimeRegion PassTimer(getPassTimer(FPP));
145 Changed |= FPP->runOnFunction(*F);
149 // The function pass(es) modified the IR, they may have clobbered the
151 if (Changed && CallGraphUpToDate) {
152 DEBUG(dbgs() << "CGSCCPASSMGR: Pass Dirtied SCC: "
153 << P->getPassName() << '\n');
154 CallGraphUpToDate = false;
160 /// RefreshCallGraph - Scan the functions in the specified CFG and resync the
161 /// callgraph with the call sites found in it. This is used after
162 /// FunctionPasses have potentially munged the callgraph, and can be used after
163 /// CallGraphSCC passes to verify that they correctly updated the callgraph.
165 /// This function returns true if it devirtualized an existing function call,
166 /// meaning it turned an indirect call into a direct call. This happens when
167 /// a function pass like GVN optimizes away stuff feeding the indirect call.
168 /// This never happens in checking mode.
170 bool CGPassManager::RefreshCallGraph(CallGraphSCC &CurSCC,
171 CallGraph &CG, bool CheckingMode) {
172 DenseMap<Value*, CallGraphNode*> CallSites;
174 DEBUG(dbgs() << "CGSCCPASSMGR: Refreshing SCC with " << CurSCC.size()
176 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
181 bool MadeChange = false;
182 bool DevirtualizedCall = false;
184 // Scan all functions in the SCC.
185 unsigned FunctionNo = 0;
186 for (CallGraphSCC::iterator SCCIdx = CurSCC.begin(), E = CurSCC.end();
187 SCCIdx != E; ++SCCIdx, ++FunctionNo) {
188 CallGraphNode *CGN = *SCCIdx;
189 Function *F = CGN->getFunction();
190 if (F == 0 || F->isDeclaration()) continue;
192 // Walk the function body looking for call sites. Sync up the call sites in
193 // CGN with those actually in the function.
195 // Keep track of the number of direct and indirect calls that were
196 // invalidated and removed.
197 unsigned NumDirectRemoved = 0, NumIndirectRemoved = 0;
199 // Get the set of call sites currently in the function.
200 for (CallGraphNode::iterator I = CGN->begin(), E = CGN->end(); I != E; ) {
201 // If this call site is null, then the function pass deleted the call
202 // entirely and the WeakVH nulled it out.
204 // If we've already seen this call site, then the FunctionPass RAUW'd
205 // one call with another, which resulted in two "uses" in the edge
206 // list of the same call.
207 CallSites.count(I->first) ||
209 // If the call edge is not from a call or invoke, then the function
210 // pass RAUW'd a call with another value. This can happen when
211 // constant folding happens of well known functions etc.
212 !CallSite(I->first)) {
213 assert(!CheckingMode &&
214 "CallGraphSCCPass did not update the CallGraph correctly!");
216 // If this was an indirect call site, count it.
217 if (I->second->getFunction() == 0)
218 ++NumIndirectRemoved;
222 // Just remove the edge from the set of callees, keep track of whether
223 // I points to the last element of the vector.
224 bool WasLast = I + 1 == E;
225 CGN->removeCallEdge(I);
227 // If I pointed to the last element of the vector, we have to bail out:
228 // iterator checking rejects comparisons of the resultant pointer with
236 assert(!CallSites.count(I->first) &&
237 "Call site occurs in node multiple times");
238 CallSites.insert(std::make_pair(I->first, I->second));
242 // Loop over all of the instructions in the function, getting the callsites.
243 // Keep track of the number of direct/indirect calls added.
244 unsigned NumDirectAdded = 0, NumIndirectAdded = 0;
246 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
247 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
248 CallSite CS(cast<Value>(I));
250 Function *Callee = CS.getCalledFunction();
251 if (Callee && Callee->isIntrinsic()) continue;
253 // If this call site already existed in the callgraph, just verify it
254 // matches up to expectations and remove it from CallSites.
255 DenseMap<Value*, CallGraphNode*>::iterator ExistingIt =
256 CallSites.find(CS.getInstruction());
257 if (ExistingIt != CallSites.end()) {
258 CallGraphNode *ExistingNode = ExistingIt->second;
260 // Remove from CallSites since we have now seen it.
261 CallSites.erase(ExistingIt);
263 // Verify that the callee is right.
264 if (ExistingNode->getFunction() == CS.getCalledFunction())
267 // If we are in checking mode, we are not allowed to actually mutate
268 // the callgraph. If this is a case where we can infer that the
269 // callgraph is less precise than it could be (e.g. an indirect call
270 // site could be turned direct), don't reject it in checking mode, and
271 // don't tweak it to be more precise.
272 if (CheckingMode && CS.getCalledFunction() &&
273 ExistingNode->getFunction() == 0)
276 assert(!CheckingMode &&
277 "CallGraphSCCPass did not update the CallGraph correctly!");
279 // If not, we either went from a direct call to indirect, indirect to
280 // direct, or direct to different direct.
281 CallGraphNode *CalleeNode;
282 if (Function *Callee = CS.getCalledFunction()) {
283 CalleeNode = CG.getOrInsertFunction(Callee);
284 // Keep track of whether we turned an indirect call into a direct
286 if (ExistingNode->getFunction() == 0) {
287 DevirtualizedCall = true;
288 DEBUG(dbgs() << " CGSCCPASSMGR: Devirtualized call to '"
289 << Callee->getName() << "'\n");
292 CalleeNode = CG.getCallsExternalNode();
295 // Update the edge target in CGN.
296 CGN->replaceCallEdge(CS, CS, CalleeNode);
301 assert(!CheckingMode &&
302 "CallGraphSCCPass did not update the CallGraph correctly!");
304 // If the call site didn't exist in the CGN yet, add it.
305 CallGraphNode *CalleeNode;
306 if (Function *Callee = CS.getCalledFunction()) {
307 CalleeNode = CG.getOrInsertFunction(Callee);
310 CalleeNode = CG.getCallsExternalNode();
314 CGN->addCalledFunction(CS, CalleeNode);
318 // We scanned the old callgraph node, removing invalidated call sites and
319 // then added back newly found call sites. One thing that can happen is
320 // that an old indirect call site was deleted and replaced with a new direct
321 // call. In this case, we have devirtualized a call, and CGSCCPM would like
322 // to iteratively optimize the new code. Unfortunately, we don't really
323 // have a great way to detect when this happens. As an approximation, we
324 // just look at whether the number of indirect calls is reduced and the
325 // number of direct calls is increased. There are tons of ways to fool this
326 // (e.g. DCE'ing an indirect call and duplicating an unrelated block with a
327 // direct call) but this is close enough.
328 if (NumIndirectRemoved > NumIndirectAdded &&
329 NumDirectRemoved < NumDirectAdded)
330 DevirtualizedCall = true;
332 // After scanning this function, if we still have entries in callsites, then
333 // they are dangling pointers. WeakVH should save us for this, so abort if
335 assert(CallSites.empty() && "Dangling pointers found in call sites map");
337 // Periodically do an explicit clear to remove tombstones when processing
339 if ((FunctionNo & 15) == 15)
343 DEBUG(if (MadeChange) {
344 dbgs() << "CGSCCPASSMGR: Refreshed SCC is now:\n";
345 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
348 if (DevirtualizedCall)
349 dbgs() << "CGSCCPASSMGR: Refresh devirtualized a call!\n";
352 dbgs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n";
357 return DevirtualizedCall;
360 /// RunAllPassesOnSCC - Execute the body of the entire pass manager on the
361 /// specified SCC. This keeps track of whether a function pass devirtualizes
362 /// any calls and returns it in DevirtualizedCall.
363 bool CGPassManager::RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
364 bool &DevirtualizedCall) {
365 bool Changed = false;
367 // CallGraphUpToDate - Keep track of whether the callgraph is known to be
368 // up-to-date or not. The CGSSC pass manager runs two types of passes:
369 // CallGraphSCC Passes and other random function passes. Because other
370 // random function passes are not CallGraph aware, they may clobber the
371 // call graph by introducing new calls or deleting other ones. This flag
372 // is set to false when we run a function pass so that we know to clean up
373 // the callgraph when we need to run a CGSCCPass again.
374 bool CallGraphUpToDate = true;
376 // Run all passes on current SCC.
377 for (unsigned PassNo = 0, e = getNumContainedPasses();
378 PassNo != e; ++PassNo) {
379 Pass *P = getContainedPass(PassNo);
381 // If we're in -debug-pass=Executions mode, construct the SCC node list,
382 // otherwise avoid constructing this string as it is expensive.
383 if (isPassDebuggingExecutionsOrMore()) {
384 std::string Functions;
386 raw_string_ostream OS(Functions);
387 for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
389 if (I != CurSCC.begin()) OS << ", ";
394 dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, Functions);
398 initializeAnalysisImpl(P);
400 // Actually run this pass on the current SCC.
401 Changed |= RunPassOnSCC(P, CurSCC, CG,
402 CallGraphUpToDate, DevirtualizedCall);
405 dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, "");
408 verifyPreservedAnalysis(P);
409 removeNotPreservedAnalysis(P);
410 recordAvailableAnalysis(P);
411 removeDeadPasses(P, "", ON_CG_MSG);
414 // If the callgraph was left out of date (because the last pass run was a
415 // functionpass), refresh it before we move on to the next SCC.
416 if (!CallGraphUpToDate)
417 DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
421 /// run - Execute all of the passes scheduled for execution. Keep track of
422 /// whether any of the passes modifies the module, and if so, return true.
423 bool CGPassManager::runOnModule(Module &M) {
424 CallGraph &CG = getAnalysis<CallGraph>();
425 bool Changed = doInitialization(CG);
427 // Walk the callgraph in bottom-up SCC order.
428 scc_iterator<CallGraph*> CGI = scc_begin(&CG);
430 CallGraphSCC CurSCC(&CGI);
431 while (!CGI.isAtEnd()) {
432 // Copy the current SCC and increment past it so that the pass can hack
433 // on the SCC if it wants to without invalidating our iterator.
434 std::vector<CallGraphNode*> &NodeVec = *CGI;
435 CurSCC.initialize(&NodeVec[0], &NodeVec[0]+NodeVec.size());
438 // At the top level, we run all the passes in this pass manager on the
439 // functions in this SCC. However, we support iterative compilation in the
440 // case where a function pass devirtualizes a call to a function. For
441 // example, it is very common for a function pass (often GVN or instcombine)
442 // to eliminate the addressing that feeds into a call. With that improved
443 // information, we would like the call to be an inline candidate, infer
444 // mod-ref information etc.
446 // Because of this, we allow iteration up to a specified iteration count.
447 // This only happens in the case of a devirtualized call, so we only burn
448 // compile time in the case that we're making progress. We also have a hard
449 // iteration count limit in case there is crazy code.
450 unsigned Iteration = 0;
451 bool DevirtualizedCall = false;
454 dbgs() << " SCCPASSMGR: Re-visiting SCC, iteration #"
455 << Iteration << '\n');
456 DevirtualizedCall = false;
457 Changed |= RunAllPassesOnSCC(CurSCC, CG, DevirtualizedCall);
458 } while (Iteration++ < MaxIterations && DevirtualizedCall);
460 if (DevirtualizedCall)
461 DEBUG(dbgs() << " CGSCCPASSMGR: Stopped iteration after " << Iteration
462 << " times, due to -max-cg-scc-iterations\n");
464 if (Iteration > MaxSCCIterations)
465 MaxSCCIterations = Iteration;
468 Changed |= doFinalization(CG);
474 bool CGPassManager::doInitialization(CallGraph &CG) {
475 bool Changed = false;
476 for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
477 if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
478 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
479 "Invalid CGPassManager member");
480 Changed |= ((FPPassManager*)PM)->doInitialization(CG.getModule());
482 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doInitialization(CG);
489 bool CGPassManager::doFinalization(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)->doFinalization(CG.getModule());
497 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doFinalization(CG);
503 //===----------------------------------------------------------------------===//
504 // CallGraphSCC Implementation
505 //===----------------------------------------------------------------------===//
507 /// ReplaceNode - This informs the SCC and the pass manager that the specified
508 /// Old node has been deleted, and New is to be used in its place.
509 void CallGraphSCC::ReplaceNode(CallGraphNode *Old, CallGraphNode *New) {
510 assert(Old != New && "Should not replace node with self");
511 for (unsigned i = 0; ; ++i) {
512 assert(i != Nodes.size() && "Node not in SCC");
513 if (Nodes[i] != Old) continue;
518 // Update the active scc_iterator so that it doesn't contain dangling
519 // pointers to the old CallGraphNode.
520 scc_iterator<CallGraph*> *CGI = (scc_iterator<CallGraph*>*)Context;
521 CGI->ReplaceNode(Old, New);
525 //===----------------------------------------------------------------------===//
526 // CallGraphSCCPass Implementation
527 //===----------------------------------------------------------------------===//
529 /// Assign pass manager to manage this pass.
530 void CallGraphSCCPass::assignPassManager(PMStack &PMS,
531 PassManagerType PreferredType) {
532 // Find CGPassManager
533 while (!PMS.empty() &&
534 PMS.top()->getPassManagerType() > PMT_CallGraphPassManager)
537 assert(!PMS.empty() && "Unable to handle Call Graph Pass");
540 if (PMS.top()->getPassManagerType() == PMT_CallGraphPassManager)
541 CGP = (CGPassManager*)PMS.top();
543 // Create new Call Graph SCC Pass Manager if it does not exist.
544 assert(!PMS.empty() && "Unable to create Call Graph Pass Manager");
545 PMDataManager *PMD = PMS.top();
547 // [1] Create new Call Graph Pass Manager
548 CGP = new CGPassManager();
550 // [2] Set up new manager's top level manager
551 PMTopLevelManager *TPM = PMD->getTopLevelManager();
552 TPM->addIndirectPassManager(CGP);
554 // [3] Assign manager to manage this new manager. This may create
555 // and push new managers into PMS
557 TPM->schedulePass(P);
559 // [4] Push new manager into PMS
566 /// getAnalysisUsage - For this class, we declare that we require and preserve
567 /// the call graph. If the derived class implements this method, it should
568 /// always explicitly call the implementation here.
569 void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const {
570 AU.addRequired<CallGraph>();
571 AU.addPreserved<CallGraph>();
575 //===----------------------------------------------------------------------===//
576 // PrintCallGraphPass Implementation
577 //===----------------------------------------------------------------------===//
580 /// PrintCallGraphPass - Print a Module corresponding to a call graph.
582 class PrintCallGraphPass : public CallGraphSCCPass {
584 raw_ostream &Out; // raw_ostream to print on.
588 PrintCallGraphPass(const std::string &B, raw_ostream &o)
589 : CallGraphSCCPass(ID), Banner(B), Out(o) {}
591 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
592 AU.setPreservesAll();
595 bool runOnSCC(CallGraphSCC &SCC) {
597 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I)
598 (*I)->getFunction()->print(Out);
603 } // end anonymous namespace.
605 char PrintCallGraphPass::ID = 0;
607 Pass *CallGraphSCCPass::createPrinterPass(raw_ostream &O,
608 const std::string &Banner) const {
609 return new PrintCallGraphPass(Banner, O);