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/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/Support/Debug.h"
26#include "llvm/Support/Timer.h"
27#include "llvm/Support/raw_ostream.h"
28using namespace llvm;
29
30//===----------------------------------------------------------------------===//
31// CGPassManager
32//
33/// CGPassManager manages FPPassManagers and CallGraphSCCPasses.
34
35namespace {
36
37class CGPassManager : public ModulePass, public PMDataManager {
38public:
39 static char ID;
40 explicit CGPassManager(int Depth)
41 : ModulePass(&ID), PMDataManager(Depth) { }
42
43 /// run - Execute all of the passes scheduled for execution. Keep track of
44 /// whether any of the passes modifies the module, and if so, return true.
45 bool runOnModule(Module &M);
46
47 bool doInitialization(CallGraph &CG);
48 bool doFinalization(CallGraph &CG);
49
50 /// Pass Manager itself does not invalidate any analysis info.
51 void getAnalysisUsage(AnalysisUsage &Info) const {
52 // CGPassManager walks SCC and it needs CallGraph.
53 Info.addRequired<CallGraph>();
54 Info.setPreservesAll();
55 }
56
57 virtual const char *getPassName() const {
58 return "CallGraph Pass Manager";
59 }
60
61 virtual PMDataManager *getAsPMDataManager() { return this; }
62 virtual Pass *getAsPass() { return this; }
63
64 // Print passes managed by this manager
65 void dumpPassStructure(unsigned Offset) {
66 errs().indent(Offset*2) << "Call Graph SCC Pass Manager\n";
67 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
68 Pass *P = getContainedPass(Index);
69 P->dumpPassStructure(Offset + 1);
70 dumpLastUses(P, Offset+1);
71 }
72 }
73
74 Pass *getContainedPass(unsigned N) {
75 assert(N < PassVector.size() && "Pass number out of range!");
76 return static_cast<Pass *>(PassVector[N]);
77 }
78
79 virtual PassManagerType getPassManagerType() const {
80 return PMT_CallGraphPassManager;
81 }
82
83private:
84 bool RunPassOnSCC(Pass *P, std::vector<CallGraphNode*> &CurSCC,
85 CallGraph &CG, bool &CallGraphUpToDate);
86 void RefreshCallGraph(std::vector<CallGraphNode*> &CurSCC, CallGraph &CG,
87 bool IsCheckingMode);
88};
89
90/// PrintCallGraphPass - Print a Module corresponding to a call graph.
91///
92class PrintCallGraphPass : public CallGraphSCCPass {
93private:
94 std::string Banner;
95 raw_ostream &Out; // raw_ostream to print on.
96
97public:
98 static char ID;
99 PrintCallGraphPass() : CallGraphSCCPass(&ID), Out(dbgs()) {}
100 PrintCallGraphPass(const std::string &B, raw_ostream &o)
101 : CallGraphSCCPass(&ID), Banner(B), Out(o) {}
102
103 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
104 AU.setPreservesAll();
105 }
106
107 bool runOnSCC(std::vector<CallGraphNode *> &SCC) {
108 Out << Banner;
109 for (std::vector<CallGraphNode *>::iterator n = SCC.begin(), ne = SCC.end();
110 n != ne;
111 ++n) {
112 (*n)->getFunction()->print(Out);
113 }
114 return false;
115 }
116};
117
118} // end anonymous namespace.
119
120char CGPassManager::ID = 0;
121
122char PrintCallGraphPass::ID = 0;
123
124bool CGPassManager::RunPassOnSCC(Pass *P, std::vector<CallGraphNode*> &CurSCC,
125 CallGraph &CG, bool &CallGraphUpToDate) {
126 bool Changed = false;
127 PMDataManager *PM = P->getAsPMDataManager();
128
129 if (PM == 0) {
130 CallGraphSCCPass *CGSP = (CallGraphSCCPass*)P;
131 if (!CallGraphUpToDate) {
132 RefreshCallGraph(CurSCC, CG, false);
133 CallGraphUpToDate = true;
134 }
135
136 {
137 TimeRegion PassTimer(getPassTimer(CGSP));
138 Changed = CGSP->runOnSCC(CurSCC);
139 }
140
141 // After the CGSCCPass is done, when assertions are enabled, use
142 // RefreshCallGraph to verify that the callgraph was correctly updated.
143#ifndef NDEBUG
144 if (Changed)
145 RefreshCallGraph(CurSCC, CG, true);
146#endif
147
148 return Changed;
149 }
150
151
152 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
153 "Invalid CGPassManager member");
154 FPPassManager *FPP = (FPPassManager*)P;
155
156 // Run pass P on all functions in the current SCC.
157 for (unsigned i = 0, e = CurSCC.size(); i != e; ++i) {
158 if (Function *F = CurSCC[i]->getFunction()) {
159 dumpPassInfo(P, EXECUTION_MSG, ON_FUNCTION_MSG, F->getName());
160 TimeRegion PassTimer(getPassTimer(FPP));
161 Changed |= FPP->runOnFunction(*F);
162 }
163 }
164
165 // The function pass(es) modified the IR, they may have clobbered the
166 // callgraph.
167 if (Changed && CallGraphUpToDate) {
168 DEBUG(dbgs() << "CGSCCPASSMGR: Pass Dirtied SCC: "
169 << P->getPassName() << '\n');
170 CallGraphUpToDate = false;
171 }
172 return Changed;
173}
174
175
176/// RefreshCallGraph - Scan the functions in the specified CFG and resync the
177/// callgraph with the call sites found in it. This is used after
178/// FunctionPasses have potentially munged the callgraph, and can be used after
179/// CallGraphSCC passes to verify that they correctly updated the callgraph.
180///
181void CGPassManager::RefreshCallGraph(std::vector<CallGraphNode*> &CurSCC,
182 CallGraph &CG, bool CheckingMode) {
183 DenseMap<Value*, CallGraphNode*> CallSites;
184
185 DEBUG(dbgs() << "CGSCCPASSMGR: Refreshing SCC with " << CurSCC.size()
186 << " nodes:\n";
187 for (unsigned i = 0, e = CurSCC.size(); i != e; ++i)
188 CurSCC[i]->dump();
189 );
190
191 bool MadeChange = false;
192
193 // Scan all functions in the SCC.
194 for (unsigned sccidx = 0, e = CurSCC.size(); sccidx != e; ++sccidx) {
195 CallGraphNode *CGN = CurSCC[sccidx];
196 Function *F = CGN->getFunction();
197 if (F == 0 || F->isDeclaration()) continue;
198
199 // Walk the function body looking for call sites. Sync up the call sites in
200 // CGN with those actually in the function.
201
202 // Get the set of call sites currently in the function.
203 for (CallGraphNode::iterator I = CGN->begin(), E = CGN->end(); I != E; ) {
204 // If this call site is null, then the function pass deleted the call
205 // entirely and the WeakVH nulled it out.
206 if (I->first == 0 ||
207 // If we've already seen this call site, then the FunctionPass RAUW'd
208 // one call with another, which resulted in two "uses" in the edge
209 // list of the same call.
210 CallSites.count(I->first) ||
211
212 // If the call edge is not from a call or invoke, then the function
213 // pass RAUW'd a call with another value. This can happen when
214 // constant folding happens of well known functions etc.
215 CallSite::get(I->first).getInstruction() == 0) {
216 assert(!CheckingMode &&
217 "CallGraphSCCPass did not update the CallGraph correctly!");
218
219 // Just remove the edge from the set of callees, keep track of whether
220 // I points to the last element of the vector.
221 bool WasLast = I + 1 == E;
222 CGN->removeCallEdge(I);
223
224 // If I pointed to the last element of the vector, we have to bail out:
225 // iterator checking rejects comparisons of the resultant pointer with
226 // end.
227 if (WasLast)
228 break;
229 E = CGN->end();
230 continue;
231 }
232
233 assert(!CallSites.count(I->first) &&
234 "Call site occurs in node multiple times");
235 CallSites.insert(std::make_pair(I->first, I->second));
236 ++I;
237 }
238
239 // Loop over all of the instructions in the function, getting the callsites.
240 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
241 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
242 CallSite CS = CallSite::get(I);
243 if (!CS.getInstruction() || isa<DbgInfoIntrinsic>(I)) continue;
244
245 // If this call site already existed in the callgraph, just verify it
246 // matches up to expectations and remove it from CallSites.
247 DenseMap<Value*, CallGraphNode*>::iterator ExistingIt =
248 CallSites.find(CS.getInstruction());
249 if (ExistingIt != CallSites.end()) {
250 CallGraphNode *ExistingNode = ExistingIt->second;
251
252 // Remove from CallSites since we have now seen it.
253 CallSites.erase(ExistingIt);
254
255 // Verify that the callee is right.
256 if (ExistingNode->getFunction() == CS.getCalledFunction())
257 continue;
258
259 // If we are in checking mode, we are not allowed to actually mutate
260 // the callgraph. If this is a case where we can infer that the
261 // callgraph is less precise than it could be (e.g. an indirect call
262 // site could be turned direct), don't reject it in checking mode, and
263 // don't tweak it to be more precise.
264 if (CheckingMode && CS.getCalledFunction() &&
265 ExistingNode->getFunction() == 0)
266 continue;
267
268 assert(!CheckingMode &&
269 "CallGraphSCCPass did not update the CallGraph correctly!");
270
271 // If not, we either went from a direct call to indirect, indirect to
272 // direct, or direct to different direct.
273 CallGraphNode *CalleeNode;
274 if (Function *Callee = CS.getCalledFunction())
275 CalleeNode = CG.getOrInsertFunction(Callee);
276 else
277 CalleeNode = CG.getCallsExternalNode();
278
279 // Update the edge target in CGN.
280 for (CallGraphNode::iterator I = CGN->begin(); ; ++I) {
281 assert(I != CGN->end() && "Didn't find call entry");
282 if (I->first == CS.getInstruction()) {
283 I->second = CalleeNode;
284 break;
285 }
286 }
287 MadeChange = true;
288 continue;
289 }
290
291 assert(!CheckingMode &&
292 "CallGraphSCCPass did not update the CallGraph correctly!");
293
294 // If the call site didn't exist in the CGN yet, add it. We assume that
295 // newly introduced call sites won't be indirect. This could be fixed
296 // in the future.
297 CallGraphNode *CalleeNode;
298 if (Function *Callee = CS.getCalledFunction())
299 CalleeNode = CG.getOrInsertFunction(Callee);
300 else
301 CalleeNode = CG.getCallsExternalNode();
302
303 CGN->addCalledFunction(CS, CalleeNode);
304 MadeChange = true;
305 }
306
307 // After scanning this function, if we still have entries in callsites, then
308 // they are dangling pointers. WeakVH should save us for this, so abort if
309 // this happens.
310 assert(CallSites.empty() && "Dangling pointers found in call sites map");
311
312 // Periodically do an explicit clear to remove tombstones when processing
313 // large scc's.
314 if ((sccidx & 15) == 0)
315 CallSites.clear();
316 }
317
318 DEBUG(if (MadeChange) {
319 dbgs() << "CGSCCPASSMGR: Refreshed SCC is now:\n";
320 for (unsigned i = 0, e = CurSCC.size(); i != e; ++i)
321 CurSCC[i]->dump();
322 } else {
323 dbgs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n";
324 }
325 );
326}
327
328/// run - Execute all of the passes scheduled for execution. Keep track of
329/// whether any of the passes modifies the module, and if so, return true.
330bool CGPassManager::runOnModule(Module &M) {
331 CallGraph &CG = getAnalysis<CallGraph>();
332 bool Changed = doInitialization(CG);
333
334 std::vector<CallGraphNode*> CurSCC;
335
336 // Walk the callgraph in bottom-up SCC order.
337 for (scc_iterator<CallGraph*> CGI = scc_begin(&CG), E = scc_end(&CG);
338 CGI != E;) {
339 // Copy the current SCC and increment past it so that the pass can hack
340 // on the SCC if it wants to without invalidating our iterator.
341 CurSCC = *CGI;
342 ++CGI;
343
344
345 // CallGraphUpToDate - Keep track of whether the callgraph is known to be
346 // up-to-date or not. The CGSSC pass manager runs two types of passes:
347 // CallGraphSCC Passes and other random function passes. Because other
348 // random function passes are not CallGraph aware, they may clobber the
349 // call graph by introducing new calls or deleting other ones. This flag
350 // is set to false when we run a function pass so that we know to clean up
351 // the callgraph when we need to run a CGSCCPass again.
352 bool CallGraphUpToDate = true;
353
354 // Run all passes on current SCC.
355 for (unsigned PassNo = 0, e = getNumContainedPasses();
356 PassNo != e; ++PassNo) {
357 Pass *P = getContainedPass(PassNo);
358
359 // If we're in -debug-pass=Executions mode, construct the SCC node list,
360 // otherwise avoid constructing this string as it is expensive.
361 if (isPassDebuggingExecutionsOrMore()) {
362 std::string Functions;
363#ifndef NDEBUG
364 raw_string_ostream OS(Functions);
365 for (unsigned i = 0, e = CurSCC.size(); i != e; ++i) {
366 if (i) OS << ", ";
367 CurSCC[i]->print(OS);
368 }
369 OS.flush();
370#endif
371 dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, Functions);
372 }
373 dumpRequiredSet(P);
374
375 initializeAnalysisImpl(P);
376
377 // Actually run this pass on the current SCC.
378 Changed |= RunPassOnSCC(P, CurSCC, CG, CallGraphUpToDate);
379
380 if (Changed)
381 dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, "");
382 dumpPreservedSet(P);
383
384 verifyPreservedAnalysis(P);
385 removeNotPreservedAnalysis(P);
386 recordAvailableAnalysis(P);
387 removeDeadPasses(P, "", ON_CG_MSG);
388 }
389
390 // If the callgraph was left out of date (because the last pass run was a
391 // functionpass), refresh it before we move on to the next SCC.
392 if (!CallGraphUpToDate)
393 RefreshCallGraph(CurSCC, CG, false);
394 }
395 Changed |= doFinalization(CG);
396 return Changed;
397}
398
399/// Initialize CG
400bool CGPassManager::doInitialization(CallGraph &CG) {
401 bool Changed = false;
402 for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
403 if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
404 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
405 "Invalid CGPassManager member");
406 Changed |= ((FPPassManager*)PM)->doInitialization(CG.getModule());
407 } else {
408 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doInitialization(CG);
409 }
410 }
411 return Changed;
412}
413
414/// Finalize CG
415bool CGPassManager::doFinalization(CallGraph &CG) {
416 bool Changed = false;
417 for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
418 if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
419 assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
420 "Invalid CGPassManager member");
421 Changed |= ((FPPassManager*)PM)->doFinalization(CG.getModule());
422 } else {
423 Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doFinalization(CG);
424 }
425 }
426 return Changed;
427}
428
429Pass *CallGraphSCCPass::createPrinterPass(raw_ostream &O,
430 const std::string &Banner) const {
431 return new PrintCallGraphPass(Banner, O);
432}
433
434/// Assign pass manager to manage this pass.
435void CallGraphSCCPass::assignPassManager(PMStack &PMS,
436 PassManagerType PreferredType) {
437 // Find CGPassManager
438 while (!PMS.empty() &&
439 PMS.top()->getPassManagerType() > PMT_CallGraphPassManager)
440 PMS.pop();
441
442 assert(!PMS.empty() && "Unable to handle Call Graph Pass");
443 CGPassManager *CGP;
444
445 if (PMS.top()->getPassManagerType() == PMT_CallGraphPassManager)
446 CGP = (CGPassManager*)PMS.top();
447 else {
448 // Create new Call Graph SCC Pass Manager if it does not exist.
449 assert(!PMS.empty() && "Unable to create Call Graph Pass Manager");
450 PMDataManager *PMD = PMS.top();
451
452 // [1] Create new Call Graph Pass Manager
453 CGP = new CGPassManager(PMD->getDepth() + 1);
454
455 // [2] Set up new manager's top level manager
456 PMTopLevelManager *TPM = PMD->getTopLevelManager();
457 TPM->addIndirectPassManager(CGP);
458
459 // [3] Assign manager to manage this new manager. This may create
460 // and push new managers into PMS
461 Pass *P = CGP;
462 TPM->schedulePass(P);
463
464 // [4] Push new manager into PMS
465 PMS.push(CGP);
466 }
467
468 CGP->add(this);
469}
470
471/// getAnalysisUsage - For this class, we declare that we require and preserve
472/// the call graph. If the derived class implements this method, it should
473/// always explicitly call the implementation here.
474void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const {
475 AU.addRequired<CallGraph>();
476 AU.addPreserved<CallGraph>();
477}