xref: /freebsd/contrib/llvm-project/llvm/lib/Analysis/CGSCCPassManager.cpp (revision 7fdf597e96a02165cfe22ff357b857d5fa15ed8a)
1 //===- CGSCCPassManager.cpp - Managing & running CGSCC passes -------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "llvm/Analysis/CGSCCPassManager.h"
10 #include "llvm/ADT/ArrayRef.h"
11 #include "llvm/ADT/PriorityWorklist.h"
12 #include "llvm/ADT/STLExtras.h"
13 #include "llvm/ADT/SetVector.h"
14 #include "llvm/ADT/SmallPtrSet.h"
15 #include "llvm/ADT/SmallVector.h"
16 #include "llvm/ADT/iterator_range.h"
17 #include "llvm/Analysis/LazyCallGraph.h"
18 #include "llvm/IR/Constant.h"
19 #include "llvm/IR/InstIterator.h"
20 #include "llvm/IR/Instruction.h"
21 #include "llvm/IR/PassManager.h"
22 #include "llvm/IR/PassManagerImpl.h"
23 #include "llvm/IR/ValueHandle.h"
24 #include "llvm/Support/Casting.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/TimeProfiler.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include <cassert>
31 #include <iterator>
32 #include <optional>
33 
34 #define DEBUG_TYPE "cgscc"
35 
36 using namespace llvm;
37 
38 // Explicit template instantiations and specialization definitions for core
39 // template typedefs.
40 namespace llvm {
41 static cl::opt<bool> AbortOnMaxDevirtIterationsReached(
42     "abort-on-max-devirt-iterations-reached",
43     cl::desc("Abort when the max iterations for devirtualization CGSCC repeat "
44              "pass is reached"));
45 
46 AnalysisKey ShouldNotRunFunctionPassesAnalysis::Key;
47 
48 // Explicit instantiations for the core proxy templates.
49 template class AllAnalysesOn<LazyCallGraph::SCC>;
50 template class AnalysisManager<LazyCallGraph::SCC, LazyCallGraph &>;
51 template class PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager,
52                            LazyCallGraph &, CGSCCUpdateResult &>;
53 template class InnerAnalysisManagerProxy<CGSCCAnalysisManager, Module>;
54 template class OuterAnalysisManagerProxy<ModuleAnalysisManager,
55                                          LazyCallGraph::SCC, LazyCallGraph &>;
56 template class OuterAnalysisManagerProxy<CGSCCAnalysisManager, Function>;
57 
58 /// Explicitly specialize the pass manager run method to handle call graph
59 /// updates.
60 template <>
61 PreservedAnalyses
62 PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager, LazyCallGraph &,
63             CGSCCUpdateResult &>::run(LazyCallGraph::SCC &InitialC,
64                                       CGSCCAnalysisManager &AM,
65                                       LazyCallGraph &G, CGSCCUpdateResult &UR) {
66   // Request PassInstrumentation from analysis manager, will use it to run
67   // instrumenting callbacks for the passes later.
68   PassInstrumentation PI =
69       AM.getResult<PassInstrumentationAnalysis>(InitialC, G);
70 
71   PreservedAnalyses PA = PreservedAnalyses::all();
72 
73   // The SCC may be refined while we are running passes over it, so set up
74   // a pointer that we can update.
75   LazyCallGraph::SCC *C = &InitialC;
76 
77   // Get Function analysis manager from its proxy.
78   FunctionAnalysisManager &FAM =
79       AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(*C)->getManager();
80 
81   for (auto &Pass : Passes) {
82     // Check the PassInstrumentation's BeforePass callbacks before running the
83     // pass, skip its execution completely if asked to (callback returns false).
84     if (!PI.runBeforePass(*Pass, *C))
85       continue;
86 
87     PreservedAnalyses PassPA = Pass->run(*C, AM, G, UR);
88 
89     // Update the SCC if necessary.
90     C = UR.UpdatedC ? UR.UpdatedC : C;
91     if (UR.UpdatedC) {
92       // If C is updated, also create a proxy and update FAM inside the result.
93       auto *ResultFAMCP =
94           &AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, G);
95       ResultFAMCP->updateFAM(FAM);
96     }
97 
98     // Intersect the final preserved analyses to compute the aggregate
99     // preserved set for this pass manager.
100     PA.intersect(PassPA);
101 
102     // If the CGSCC pass wasn't able to provide a valid updated SCC, the
103     // current SCC may simply need to be skipped if invalid.
104     if (UR.InvalidatedSCCs.count(C)) {
105       PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
106       LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
107       break;
108     }
109 
110     // Check that we didn't miss any update scenario.
111     assert(C->begin() != C->end() && "Cannot have an empty SCC!");
112 
113     // Update the analysis manager as each pass runs and potentially
114     // invalidates analyses.
115     AM.invalidate(*C, PassPA);
116 
117     PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
118   }
119 
120   // Before we mark all of *this* SCC's analyses as preserved below, intersect
121   // this with the cross-SCC preserved analysis set. This is used to allow
122   // CGSCC passes to mutate ancestor SCCs and still trigger proper invalidation
123   // for them.
124   UR.CrossSCCPA.intersect(PA);
125 
126   // Invalidation was handled after each pass in the above loop for the current
127   // SCC. Therefore, the remaining analysis results in the AnalysisManager are
128   // preserved. We mark this with a set so that we don't need to inspect each
129   // one individually.
130   PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
131 
132   return PA;
133 }
134 
135 PreservedAnalyses
136 ModuleToPostOrderCGSCCPassAdaptor::run(Module &M, ModuleAnalysisManager &AM) {
137   // Setup the CGSCC analysis manager from its proxy.
138   CGSCCAnalysisManager &CGAM =
139       AM.getResult<CGSCCAnalysisManagerModuleProxy>(M).getManager();
140 
141   // Get the call graph for this module.
142   LazyCallGraph &CG = AM.getResult<LazyCallGraphAnalysis>(M);
143 
144   // Get Function analysis manager from its proxy.
145   FunctionAnalysisManager &FAM =
146       AM.getCachedResult<FunctionAnalysisManagerModuleProxy>(M)->getManager();
147 
148   // We keep worklists to allow us to push more work onto the pass manager as
149   // the passes are run.
150   SmallPriorityWorklist<LazyCallGraph::RefSCC *, 1> RCWorklist;
151   SmallPriorityWorklist<LazyCallGraph::SCC *, 1> CWorklist;
152 
153   // Keep sets for invalidated SCCs that should be skipped when
154   // iterating off the worklists.
155   SmallPtrSet<LazyCallGraph::SCC *, 4> InvalidSCCSet;
156 
157   SmallDenseSet<std::pair<LazyCallGraph::Node *, LazyCallGraph::SCC *>, 4>
158       InlinedInternalEdges;
159 
160   SmallVector<Function *, 4> DeadFunctions;
161 
162   CGSCCUpdateResult UR = {CWorklist,
163                           InvalidSCCSet,
164                           nullptr,
165                           PreservedAnalyses::all(),
166                           InlinedInternalEdges,
167                           DeadFunctions,
168                           {}};
169 
170   // Request PassInstrumentation from analysis manager, will use it to run
171   // instrumenting callbacks for the passes later.
172   PassInstrumentation PI = AM.getResult<PassInstrumentationAnalysis>(M);
173 
174   PreservedAnalyses PA = PreservedAnalyses::all();
175   CG.buildRefSCCs();
176   for (LazyCallGraph::RefSCC &RC :
177        llvm::make_early_inc_range(CG.postorder_ref_sccs())) {
178     assert(RCWorklist.empty() &&
179            "Should always start with an empty RefSCC worklist");
180     // The postorder_ref_sccs range we are walking is lazily constructed, so
181     // we only push the first one onto the worklist. The worklist allows us
182     // to capture *new* RefSCCs created during transformations.
183     //
184     // We really want to form RefSCCs lazily because that makes them cheaper
185     // to update as the program is simplified and allows us to have greater
186     // cache locality as forming a RefSCC touches all the parts of all the
187     // functions within that RefSCC.
188     //
189     // We also eagerly increment the iterator to the next position because
190     // the CGSCC passes below may delete the current RefSCC.
191     RCWorklist.insert(&RC);
192 
193     do {
194       LazyCallGraph::RefSCC *RC = RCWorklist.pop_back_val();
195       assert(CWorklist.empty() &&
196              "Should always start with an empty SCC worklist");
197 
198       LLVM_DEBUG(dbgs() << "Running an SCC pass across the RefSCC: " << *RC
199                         << "\n");
200 
201       // The top of the worklist may *also* be the same SCC we just ran over
202       // (and invalidated for). Keep track of that last SCC we processed due
203       // to SCC update to avoid redundant processing when an SCC is both just
204       // updated itself and at the top of the worklist.
205       LazyCallGraph::SCC *LastUpdatedC = nullptr;
206 
207       // Push the initial SCCs in reverse post-order as we'll pop off the
208       // back and so see this in post-order.
209       for (LazyCallGraph::SCC &C : llvm::reverse(*RC))
210         CWorklist.insert(&C);
211 
212       do {
213         LazyCallGraph::SCC *C = CWorklist.pop_back_val();
214         // Due to call graph mutations, we may have invalid SCCs or SCCs from
215         // other RefSCCs in the worklist. The invalid ones are dead and the
216         // other RefSCCs should be queued above, so we just need to skip both
217         // scenarios here.
218         if (InvalidSCCSet.count(C)) {
219           LLVM_DEBUG(dbgs() << "Skipping an invalid SCC...\n");
220           continue;
221         }
222         if (LastUpdatedC == C) {
223           LLVM_DEBUG(dbgs() << "Skipping redundant run on SCC: " << *C << "\n");
224           continue;
225         }
226         // We used to also check if the current SCC is part of the current
227         // RefSCC and bail if it wasn't, since it should be in RCWorklist.
228         // However, this can cause compile time explosions in some cases on
229         // modules with a huge RefSCC. If a non-trivial amount of SCCs in the
230         // huge RefSCC can become their own child RefSCC, we create one child
231         // RefSCC, bail on the current RefSCC, visit the child RefSCC, revisit
232         // the huge RefSCC, and repeat. By visiting all SCCs in the original
233         // RefSCC we create all the child RefSCCs in one pass of the RefSCC,
234         // rather one pass of the RefSCC creating one child RefSCC at a time.
235 
236         // Ensure we can proxy analysis updates from the CGSCC analysis manager
237         // into the Function analysis manager by getting a proxy here.
238         // This also needs to update the FunctionAnalysisManager, as this may be
239         // the first time we see this SCC.
240         CGAM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, CG).updateFAM(
241             FAM);
242 
243         // Each time we visit a new SCC pulled off the worklist,
244         // a transformation of a child SCC may have also modified this parent
245         // and invalidated analyses. So we invalidate using the update record's
246         // cross-SCC preserved set. This preserved set is intersected by any
247         // CGSCC pass that handles invalidation (primarily pass managers) prior
248         // to marking its SCC as preserved. That lets us track everything that
249         // might need invalidation across SCCs without excessive invalidations
250         // on a single SCC.
251         //
252         // This essentially allows SCC passes to freely invalidate analyses
253         // of any ancestor SCC. If this becomes detrimental to successfully
254         // caching analyses, we could force each SCC pass to manually
255         // invalidate the analyses for any SCCs other than themselves which
256         // are mutated. However, that seems to lose the robustness of the
257         // pass-manager driven invalidation scheme.
258         CGAM.invalidate(*C, UR.CrossSCCPA);
259 
260         do {
261           // Check that we didn't miss any update scenario.
262           assert(!InvalidSCCSet.count(C) && "Processing an invalid SCC!");
263           assert(C->begin() != C->end() && "Cannot have an empty SCC!");
264 
265           LastUpdatedC = UR.UpdatedC;
266           UR.UpdatedC = nullptr;
267 
268           // Check the PassInstrumentation's BeforePass callbacks before
269           // running the pass, skip its execution completely if asked to
270           // (callback returns false).
271           if (!PI.runBeforePass<LazyCallGraph::SCC>(*Pass, *C))
272             continue;
273 
274           PreservedAnalyses PassPA = Pass->run(*C, CGAM, CG, UR);
275 
276           // Update the SCC and RefSCC if necessary.
277           C = UR.UpdatedC ? UR.UpdatedC : C;
278 
279           if (UR.UpdatedC) {
280             // If we're updating the SCC, also update the FAM inside the proxy's
281             // result.
282             CGAM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, CG).updateFAM(
283                 FAM);
284           }
285 
286           // Intersect with the cross-SCC preserved set to capture any
287           // cross-SCC invalidation.
288           UR.CrossSCCPA.intersect(PassPA);
289           // Intersect the preserved set so that invalidation of module
290           // analyses will eventually occur when the module pass completes.
291           PA.intersect(PassPA);
292 
293           // If the CGSCC pass wasn't able to provide a valid updated SCC,
294           // the current SCC may simply need to be skipped if invalid.
295           if (UR.InvalidatedSCCs.count(C)) {
296             PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
297             LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
298             break;
299           }
300 
301           // Check that we didn't miss any update scenario.
302           assert(C->begin() != C->end() && "Cannot have an empty SCC!");
303 
304           // We handle invalidating the CGSCC analysis manager's information
305           // for the (potentially updated) SCC here. Note that any other SCCs
306           // whose structure has changed should have been invalidated by
307           // whatever was updating the call graph. This SCC gets invalidated
308           // late as it contains the nodes that were actively being
309           // processed.
310           CGAM.invalidate(*C, PassPA);
311 
312           PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
313 
314           // The pass may have restructured the call graph and refined the
315           // current SCC and/or RefSCC. We need to update our current SCC and
316           // RefSCC pointers to follow these. Also, when the current SCC is
317           // refined, re-run the SCC pass over the newly refined SCC in order
318           // to observe the most precise SCC model available. This inherently
319           // cannot cycle excessively as it only happens when we split SCCs
320           // apart, at most converging on a DAG of single nodes.
321           // FIXME: If we ever start having RefSCC passes, we'll want to
322           // iterate there too.
323           if (UR.UpdatedC)
324             LLVM_DEBUG(dbgs()
325                        << "Re-running SCC passes after a refinement of the "
326                           "current SCC: "
327                        << *UR.UpdatedC << "\n");
328 
329           // Note that both `C` and `RC` may at this point refer to deleted,
330           // invalid SCC and RefSCCs respectively. But we will short circuit
331           // the processing when we check them in the loop above.
332         } while (UR.UpdatedC);
333       } while (!CWorklist.empty());
334 
335       // We only need to keep internal inlined edge information within
336       // a RefSCC, clear it to save on space and let the next time we visit
337       // any of these functions have a fresh start.
338       InlinedInternalEdges.clear();
339     } while (!RCWorklist.empty());
340   }
341 
342   CG.removeDeadFunctions(DeadFunctions);
343   for (Function *DeadF : DeadFunctions)
344     DeadF->eraseFromParent();
345 
346 #if defined(EXPENSIVE_CHECKS)
347   // Verify that the call graph is still valid.
348   CG.verify();
349 #endif
350 
351   // By definition we preserve the call garph, all SCC analyses, and the
352   // analysis proxies by handling them above and in any nested pass managers.
353   PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
354   PA.preserve<LazyCallGraphAnalysis>();
355   PA.preserve<CGSCCAnalysisManagerModuleProxy>();
356   PA.preserve<FunctionAnalysisManagerModuleProxy>();
357   return PA;
358 }
359 
360 PreservedAnalyses DevirtSCCRepeatedPass::run(LazyCallGraph::SCC &InitialC,
361                                              CGSCCAnalysisManager &AM,
362                                              LazyCallGraph &CG,
363                                              CGSCCUpdateResult &UR) {
364   PreservedAnalyses PA = PreservedAnalyses::all();
365   PassInstrumentation PI =
366       AM.getResult<PassInstrumentationAnalysis>(InitialC, CG);
367 
368   // The SCC may be refined while we are running passes over it, so set up
369   // a pointer that we can update.
370   LazyCallGraph::SCC *C = &InitialC;
371 
372   // Struct to track the counts of direct and indirect calls in each function
373   // of the SCC.
374   struct CallCount {
375     int Direct;
376     int Indirect;
377   };
378 
379   // Put value handles on all of the indirect calls and return the number of
380   // direct calls for each function in the SCC.
381   auto ScanSCC = [](LazyCallGraph::SCC &C,
382                     SmallMapVector<Value *, WeakTrackingVH, 16> &CallHandles) {
383     assert(CallHandles.empty() && "Must start with a clear set of handles.");
384 
385     SmallDenseMap<Function *, CallCount> CallCounts;
386     CallCount CountLocal = {0, 0};
387     for (LazyCallGraph::Node &N : C) {
388       CallCount &Count =
389           CallCounts.insert(std::make_pair(&N.getFunction(), CountLocal))
390               .first->second;
391       for (Instruction &I : instructions(N.getFunction()))
392         if (auto *CB = dyn_cast<CallBase>(&I)) {
393           if (CB->getCalledFunction()) {
394             ++Count.Direct;
395           } else {
396             ++Count.Indirect;
397             CallHandles.insert({CB, WeakTrackingVH(CB)});
398           }
399         }
400     }
401 
402     return CallCounts;
403   };
404 
405   UR.IndirectVHs.clear();
406   // Populate the initial call handles and get the initial call counts.
407   auto CallCounts = ScanSCC(*C, UR.IndirectVHs);
408 
409   for (int Iteration = 0;; ++Iteration) {
410     if (!PI.runBeforePass<LazyCallGraph::SCC>(*Pass, *C))
411       continue;
412 
413     PreservedAnalyses PassPA = Pass->run(*C, AM, CG, UR);
414 
415     PA.intersect(PassPA);
416 
417     // If the CGSCC pass wasn't able to provide a valid updated SCC, the
418     // current SCC may simply need to be skipped if invalid.
419     if (UR.InvalidatedSCCs.count(C)) {
420       PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
421       LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
422       break;
423     }
424 
425     // Update the analysis manager with each run and intersect the total set
426     // of preserved analyses so we're ready to iterate.
427     AM.invalidate(*C, PassPA);
428 
429     PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
430 
431     // If the SCC structure has changed, bail immediately and let the outer
432     // CGSCC layer handle any iteration to reflect the refined structure.
433     if (UR.UpdatedC && UR.UpdatedC != C)
434       break;
435 
436     assert(C->begin() != C->end() && "Cannot have an empty SCC!");
437 
438     // Check whether any of the handles were devirtualized.
439     bool Devirt = llvm::any_of(UR.IndirectVHs, [](auto &P) -> bool {
440       if (P.second) {
441         if (CallBase *CB = dyn_cast<CallBase>(P.second)) {
442           if (CB->getCalledFunction()) {
443             LLVM_DEBUG(dbgs() << "Found devirtualized call: " << *CB << "\n");
444             return true;
445           }
446         }
447       }
448       return false;
449     });
450 
451     // Rescan to build up a new set of handles and count how many direct
452     // calls remain. If we decide to iterate, this also sets up the input to
453     // the next iteration.
454     UR.IndirectVHs.clear();
455     auto NewCallCounts = ScanSCC(*C, UR.IndirectVHs);
456 
457     // If we haven't found an explicit devirtualization already see if we
458     // have decreased the number of indirect calls and increased the number
459     // of direct calls for any function in the SCC. This can be fooled by all
460     // manner of transformations such as DCE and other things, but seems to
461     // work well in practice.
462     if (!Devirt)
463       // Iterate over the keys in NewCallCounts, if Function also exists in
464       // CallCounts, make the check below.
465       for (auto &Pair : NewCallCounts) {
466         auto &CallCountNew = Pair.second;
467         auto CountIt = CallCounts.find(Pair.first);
468         if (CountIt != CallCounts.end()) {
469           const auto &CallCountOld = CountIt->second;
470           if (CallCountOld.Indirect > CallCountNew.Indirect &&
471               CallCountOld.Direct < CallCountNew.Direct) {
472             Devirt = true;
473             break;
474           }
475         }
476       }
477 
478     if (!Devirt) {
479       break;
480     }
481 
482     // Otherwise, if we've already hit our max, we're done.
483     if (Iteration >= MaxIterations) {
484       if (AbortOnMaxDevirtIterationsReached)
485         report_fatal_error("Max devirtualization iterations reached");
486       LLVM_DEBUG(
487           dbgs() << "Found another devirtualization after hitting the max "
488                     "number of repetitions ("
489                  << MaxIterations << ") on SCC: " << *C << "\n");
490       break;
491     }
492 
493     LLVM_DEBUG(
494         dbgs() << "Repeating an SCC pass after finding a devirtualization in: "
495                << *C << "\n");
496 
497     // Move over the new call counts in preparation for iterating.
498     CallCounts = std::move(NewCallCounts);
499   }
500 
501   // Note that we don't add any preserved entries here unlike a more normal
502   // "pass manager" because we only handle invalidation *between* iterations,
503   // not after the last iteration.
504   return PA;
505 }
506 
507 PreservedAnalyses CGSCCToFunctionPassAdaptor::run(LazyCallGraph::SCC &C,
508                                                   CGSCCAnalysisManager &AM,
509                                                   LazyCallGraph &CG,
510                                                   CGSCCUpdateResult &UR) {
511   // Setup the function analysis manager from its proxy.
512   FunctionAnalysisManager &FAM =
513       AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, CG).getManager();
514 
515   SmallVector<LazyCallGraph::Node *, 4> Nodes;
516   for (LazyCallGraph::Node &N : C)
517     Nodes.push_back(&N);
518 
519   // The SCC may get split while we are optimizing functions due to deleting
520   // edges. If this happens, the current SCC can shift, so keep track of
521   // a pointer we can overwrite.
522   LazyCallGraph::SCC *CurrentC = &C;
523 
524   LLVM_DEBUG(dbgs() << "Running function passes across an SCC: " << C << "\n");
525 
526   PreservedAnalyses PA = PreservedAnalyses::all();
527   for (LazyCallGraph::Node *N : Nodes) {
528     // Skip nodes from other SCCs. These may have been split out during
529     // processing. We'll eventually visit those SCCs and pick up the nodes
530     // there.
531     if (CG.lookupSCC(*N) != CurrentC)
532       continue;
533 
534     Function &F = N->getFunction();
535 
536     if (NoRerun && FAM.getCachedResult<ShouldNotRunFunctionPassesAnalysis>(F))
537       continue;
538 
539     PassInstrumentation PI = FAM.getResult<PassInstrumentationAnalysis>(F);
540     if (!PI.runBeforePass<Function>(*Pass, F))
541       continue;
542 
543     PreservedAnalyses PassPA = Pass->run(F, FAM);
544 
545     // We know that the function pass couldn't have invalidated any other
546     // function's analyses (that's the contract of a function pass), so
547     // directly handle the function analysis manager's invalidation here.
548     FAM.invalidate(F, EagerlyInvalidate ? PreservedAnalyses::none() : PassPA);
549 
550     PI.runAfterPass<Function>(*Pass, F, PassPA);
551 
552     // Then intersect the preserved set so that invalidation of module
553     // analyses will eventually occur when the module pass completes.
554     PA.intersect(std::move(PassPA));
555 
556     // If the call graph hasn't been preserved, update it based on this
557     // function pass. This may also update the current SCC to point to
558     // a smaller, more refined SCC.
559     auto PAC = PA.getChecker<LazyCallGraphAnalysis>();
560     if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<Module>>()) {
561       CurrentC = &updateCGAndAnalysisManagerForFunctionPass(CG, *CurrentC, *N,
562                                                             AM, UR, FAM);
563       assert(CG.lookupSCC(*N) == CurrentC &&
564              "Current SCC not updated to the SCC containing the current node!");
565     }
566   }
567 
568   // By definition we preserve the proxy. And we preserve all analyses on
569   // Functions. This precludes *any* invalidation of function analyses by the
570   // proxy, but that's OK because we've taken care to invalidate analyses in
571   // the function analysis manager incrementally above.
572   PA.preserveSet<AllAnalysesOn<Function>>();
573   PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
574 
575   // We've also ensured that we updated the call graph along the way.
576   PA.preserve<LazyCallGraphAnalysis>();
577 
578   return PA;
579 }
580 
581 bool CGSCCAnalysisManagerModuleProxy::Result::invalidate(
582     Module &M, const PreservedAnalyses &PA,
583     ModuleAnalysisManager::Invalidator &Inv) {
584   // If literally everything is preserved, we're done.
585   if (PA.areAllPreserved())
586     return false; // This is still a valid proxy.
587 
588   // If this proxy or the call graph is going to be invalidated, we also need
589   // to clear all the keys coming from that analysis.
590   //
591   // We also directly invalidate the FAM's module proxy if necessary, and if
592   // that proxy isn't preserved we can't preserve this proxy either. We rely on
593   // it to handle module -> function analysis invalidation in the face of
594   // structural changes and so if it's unavailable we conservatively clear the
595   // entire SCC layer as well rather than trying to do invalidation ourselves.
596   auto PAC = PA.getChecker<CGSCCAnalysisManagerModuleProxy>();
597   if (!(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Module>>()) ||
598       Inv.invalidate<LazyCallGraphAnalysis>(M, PA) ||
599       Inv.invalidate<FunctionAnalysisManagerModuleProxy>(M, PA)) {
600     InnerAM->clear();
601 
602     // And the proxy itself should be marked as invalid so that we can observe
603     // the new call graph. This isn't strictly necessary because we cheat
604     // above, but is still useful.
605     return true;
606   }
607 
608   // Directly check if the relevant set is preserved so we can short circuit
609   // invalidating SCCs below.
610   bool AreSCCAnalysesPreserved =
611       PA.allAnalysesInSetPreserved<AllAnalysesOn<LazyCallGraph::SCC>>();
612 
613   // Ok, we have a graph, so we can propagate the invalidation down into it.
614   G->buildRefSCCs();
615   for (auto &RC : G->postorder_ref_sccs())
616     for (auto &C : RC) {
617       std::optional<PreservedAnalyses> InnerPA;
618 
619       // Check to see whether the preserved set needs to be adjusted based on
620       // module-level analysis invalidation triggering deferred invalidation
621       // for this SCC.
622       if (auto *OuterProxy =
623               InnerAM->getCachedResult<ModuleAnalysisManagerCGSCCProxy>(C))
624         for (const auto &OuterInvalidationPair :
625              OuterProxy->getOuterInvalidations()) {
626           AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
627           const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
628           if (Inv.invalidate(OuterAnalysisID, M, PA)) {
629             if (!InnerPA)
630               InnerPA = PA;
631             for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
632               InnerPA->abandon(InnerAnalysisID);
633           }
634         }
635 
636       // Check if we needed a custom PA set. If so we'll need to run the inner
637       // invalidation.
638       if (InnerPA) {
639         InnerAM->invalidate(C, *InnerPA);
640         continue;
641       }
642 
643       // Otherwise we only need to do invalidation if the original PA set didn't
644       // preserve all SCC analyses.
645       if (!AreSCCAnalysesPreserved)
646         InnerAM->invalidate(C, PA);
647     }
648 
649   // Return false to indicate that this result is still a valid proxy.
650   return false;
651 }
652 
653 template <>
654 CGSCCAnalysisManagerModuleProxy::Result
655 CGSCCAnalysisManagerModuleProxy::run(Module &M, ModuleAnalysisManager &AM) {
656   // Force the Function analysis manager to also be available so that it can
657   // be accessed in an SCC analysis and proxied onward to function passes.
658   // FIXME: It is pretty awkward to just drop the result here and assert that
659   // we can find it again later.
660   (void)AM.getResult<FunctionAnalysisManagerModuleProxy>(M);
661 
662   return Result(*InnerAM, AM.getResult<LazyCallGraphAnalysis>(M));
663 }
664 
665 AnalysisKey FunctionAnalysisManagerCGSCCProxy::Key;
666 
667 FunctionAnalysisManagerCGSCCProxy::Result
668 FunctionAnalysisManagerCGSCCProxy::run(LazyCallGraph::SCC &C,
669                                        CGSCCAnalysisManager &AM,
670                                        LazyCallGraph &CG) {
671   // Note: unconditionally getting checking that the proxy exists may get it at
672   // this point. There are cases when this is being run unnecessarily, but
673   // it is cheap and having the assertion in place is more valuable.
674   auto &MAMProxy = AM.getResult<ModuleAnalysisManagerCGSCCProxy>(C, CG);
675   Module &M = *C.begin()->getFunction().getParent();
676   bool ProxyExists =
677       MAMProxy.cachedResultExists<FunctionAnalysisManagerModuleProxy>(M);
678   assert(ProxyExists &&
679          "The CGSCC pass manager requires that the FAM module proxy is run "
680          "on the module prior to entering the CGSCC walk");
681   (void)ProxyExists;
682 
683   // We just return an empty result. The caller will use the updateFAM interface
684   // to correctly register the relevant FunctionAnalysisManager based on the
685   // context in which this proxy is run.
686   return Result();
687 }
688 
689 bool FunctionAnalysisManagerCGSCCProxy::Result::invalidate(
690     LazyCallGraph::SCC &C, const PreservedAnalyses &PA,
691     CGSCCAnalysisManager::Invalidator &Inv) {
692   // If literally everything is preserved, we're done.
693   if (PA.areAllPreserved())
694     return false; // This is still a valid proxy.
695 
696   // All updates to preserve valid results are done below, so we don't need to
697   // invalidate this proxy.
698   //
699   // Note that in order to preserve this proxy, a module pass must ensure that
700   // the FAM has been completely updated to handle the deletion of functions.
701   // Specifically, any FAM-cached results for those functions need to have been
702   // forcibly cleared. When preserved, this proxy will only invalidate results
703   // cached on functions *still in the module* at the end of the module pass.
704   auto PAC = PA.getChecker<FunctionAnalysisManagerCGSCCProxy>();
705   if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<LazyCallGraph::SCC>>()) {
706     for (LazyCallGraph::Node &N : C)
707       FAM->invalidate(N.getFunction(), PA);
708 
709     return false;
710   }
711 
712   // Directly check if the relevant set is preserved.
713   bool AreFunctionAnalysesPreserved =
714       PA.allAnalysesInSetPreserved<AllAnalysesOn<Function>>();
715 
716   // Now walk all the functions to see if any inner analysis invalidation is
717   // necessary.
718   for (LazyCallGraph::Node &N : C) {
719     Function &F = N.getFunction();
720     std::optional<PreservedAnalyses> FunctionPA;
721 
722     // Check to see whether the preserved set needs to be pruned based on
723     // SCC-level analysis invalidation that triggers deferred invalidation
724     // registered with the outer analysis manager proxy for this function.
725     if (auto *OuterProxy =
726             FAM->getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F))
727       for (const auto &OuterInvalidationPair :
728            OuterProxy->getOuterInvalidations()) {
729         AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
730         const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
731         if (Inv.invalidate(OuterAnalysisID, C, PA)) {
732           if (!FunctionPA)
733             FunctionPA = PA;
734           for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
735             FunctionPA->abandon(InnerAnalysisID);
736         }
737       }
738 
739     // Check if we needed a custom PA set, and if so we'll need to run the
740     // inner invalidation.
741     if (FunctionPA) {
742       FAM->invalidate(F, *FunctionPA);
743       continue;
744     }
745 
746     // Otherwise we only need to do invalidation if the original PA set didn't
747     // preserve all function analyses.
748     if (!AreFunctionAnalysesPreserved)
749       FAM->invalidate(F, PA);
750   }
751 
752   // Return false to indicate that this result is still a valid proxy.
753   return false;
754 }
755 
756 } // end namespace llvm
757 
758 /// When a new SCC is created for the graph we first update the
759 /// FunctionAnalysisManager in the Proxy's result.
760 /// As there might be function analysis results cached for the functions now in
761 /// that SCC, two forms of  updates are required.
762 ///
763 /// First, a proxy from the SCC to the FunctionAnalysisManager needs to be
764 /// created so that any subsequent invalidation events to the SCC are
765 /// propagated to the function analysis results cached for functions within it.
766 ///
767 /// Second, if any of the functions within the SCC have analysis results with
768 /// outer analysis dependencies, then those dependencies would point to the
769 /// *wrong* SCC's analysis result. We forcibly invalidate the necessary
770 /// function analyses so that they don't retain stale handles.
771 static void updateNewSCCFunctionAnalyses(LazyCallGraph::SCC &C,
772                                          LazyCallGraph &G,
773                                          CGSCCAnalysisManager &AM,
774                                          FunctionAnalysisManager &FAM) {
775   AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, G).updateFAM(FAM);
776 
777   // Now walk the functions in this SCC and invalidate any function analysis
778   // results that might have outer dependencies on an SCC analysis.
779   for (LazyCallGraph::Node &N : C) {
780     Function &F = N.getFunction();
781 
782     auto *OuterProxy =
783         FAM.getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F);
784     if (!OuterProxy)
785       // No outer analyses were queried, nothing to do.
786       continue;
787 
788     // Forcibly abandon all the inner analyses with dependencies, but
789     // invalidate nothing else.
790     auto PA = PreservedAnalyses::all();
791     for (const auto &OuterInvalidationPair :
792          OuterProxy->getOuterInvalidations()) {
793       const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
794       for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
795         PA.abandon(InnerAnalysisID);
796     }
797 
798     // Now invalidate anything we found.
799     FAM.invalidate(F, PA);
800   }
801 }
802 
803 /// Helper function to update both the \c CGSCCAnalysisManager \p AM and the \c
804 /// CGSCCPassManager's \c CGSCCUpdateResult \p UR based on a range of newly
805 /// added SCCs.
806 ///
807 /// The range of new SCCs must be in postorder already. The SCC they were split
808 /// out of must be provided as \p C. The current node being mutated and
809 /// triggering updates must be passed as \p N.
810 ///
811 /// This function returns the SCC containing \p N. This will be either \p C if
812 /// no new SCCs have been split out, or it will be the new SCC containing \p N.
813 template <typename SCCRangeT>
814 static LazyCallGraph::SCC *
815 incorporateNewSCCRange(const SCCRangeT &NewSCCRange, LazyCallGraph &G,
816                        LazyCallGraph::Node &N, LazyCallGraph::SCC *C,
817                        CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR) {
818   using SCC = LazyCallGraph::SCC;
819 
820   if (NewSCCRange.empty())
821     return C;
822 
823   // Add the current SCC to the worklist as its shape has changed.
824   UR.CWorklist.insert(C);
825   LLVM_DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist:" << *C
826                     << "\n");
827 
828   SCC *OldC = C;
829 
830   // Update the current SCC. Note that if we have new SCCs, this must actually
831   // change the SCC.
832   assert(C != &*NewSCCRange.begin() &&
833          "Cannot insert new SCCs without changing current SCC!");
834   C = &*NewSCCRange.begin();
835   assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
836 
837   // If we had a cached FAM proxy originally, we will want to create more of
838   // them for each SCC that was split off.
839   FunctionAnalysisManager *FAM = nullptr;
840   if (auto *FAMProxy =
841           AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(*OldC))
842     FAM = &FAMProxy->getManager();
843 
844   // We need to propagate an invalidation call to all but the newly current SCC
845   // because the outer pass manager won't do that for us after splitting them.
846   // FIXME: We should accept a PreservedAnalysis from the CG updater so that if
847   // there are preserved analysis we can avoid invalidating them here for
848   // split-off SCCs.
849   // We know however that this will preserve any FAM proxy so go ahead and mark
850   // that.
851   auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
852   PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
853   AM.invalidate(*OldC, PA);
854 
855   // Ensure the now-current SCC's function analyses are updated.
856   if (FAM)
857     updateNewSCCFunctionAnalyses(*C, G, AM, *FAM);
858 
859   for (SCC &NewC : llvm::reverse(llvm::drop_begin(NewSCCRange))) {
860     assert(C != &NewC && "No need to re-visit the current SCC!");
861     assert(OldC != &NewC && "Already handled the original SCC!");
862     UR.CWorklist.insert(&NewC);
863     LLVM_DEBUG(dbgs() << "Enqueuing a newly formed SCC:" << NewC << "\n");
864 
865     // Ensure new SCCs' function analyses are updated.
866     if (FAM)
867       updateNewSCCFunctionAnalyses(NewC, G, AM, *FAM);
868 
869     // Also propagate a normal invalidation to the new SCC as only the current
870     // will get one from the pass manager infrastructure.
871     AM.invalidate(NewC, PA);
872   }
873   return C;
874 }
875 
876 static LazyCallGraph::SCC &updateCGAndAnalysisManagerForPass(
877     LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
878     CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
879     FunctionAnalysisManager &FAM, bool FunctionPass) {
880   using Node = LazyCallGraph::Node;
881   using Edge = LazyCallGraph::Edge;
882   using SCC = LazyCallGraph::SCC;
883   using RefSCC = LazyCallGraph::RefSCC;
884 
885   RefSCC &InitialRC = InitialC.getOuterRefSCC();
886   SCC *C = &InitialC;
887   RefSCC *RC = &InitialRC;
888   Function &F = N.getFunction();
889 
890   // Walk the function body and build up the set of retained, promoted, and
891   // demoted edges.
892   SmallVector<Constant *, 16> Worklist;
893   SmallPtrSet<Constant *, 16> Visited;
894   SmallPtrSet<Node *, 16> RetainedEdges;
895   SmallSetVector<Node *, 4> PromotedRefTargets;
896   SmallSetVector<Node *, 4> DemotedCallTargets;
897   SmallSetVector<Node *, 4> NewCallEdges;
898   SmallSetVector<Node *, 4> NewRefEdges;
899 
900   // First walk the function and handle all called functions. We do this first
901   // because if there is a single call edge, whether there are ref edges is
902   // irrelevant.
903   for (Instruction &I : instructions(F)) {
904     if (auto *CB = dyn_cast<CallBase>(&I)) {
905       if (Function *Callee = CB->getCalledFunction()) {
906         if (Visited.insert(Callee).second && !Callee->isDeclaration()) {
907           Node *CalleeN = G.lookup(*Callee);
908           assert(CalleeN &&
909                  "Visited function should already have an associated node");
910           Edge *E = N->lookup(*CalleeN);
911           assert((E || !FunctionPass) &&
912                  "No function transformations should introduce *new* "
913                  "call edges! Any new calls should be modeled as "
914                  "promoted existing ref edges!");
915           bool Inserted = RetainedEdges.insert(CalleeN).second;
916           (void)Inserted;
917           assert(Inserted && "We should never visit a function twice.");
918           if (!E)
919             NewCallEdges.insert(CalleeN);
920           else if (!E->isCall())
921             PromotedRefTargets.insert(CalleeN);
922         }
923       } else {
924         // We can miss devirtualization if an indirect call is created then
925         // promoted before updateCGAndAnalysisManagerForPass runs.
926         auto *Entry = UR.IndirectVHs.find(CB);
927         if (Entry == UR.IndirectVHs.end())
928           UR.IndirectVHs.insert({CB, WeakTrackingVH(CB)});
929         else if (!Entry->second)
930           Entry->second = WeakTrackingVH(CB);
931       }
932     }
933   }
934 
935   // Now walk all references.
936   for (Instruction &I : instructions(F))
937     for (Value *Op : I.operand_values())
938       if (auto *OpC = dyn_cast<Constant>(Op))
939         if (Visited.insert(OpC).second)
940           Worklist.push_back(OpC);
941 
942   auto VisitRef = [&](Function &Referee) {
943     Node *RefereeN = G.lookup(Referee);
944     assert(RefereeN &&
945            "Visited function should already have an associated node");
946     Edge *E = N->lookup(*RefereeN);
947     assert((E || !FunctionPass) &&
948            "No function transformations should introduce *new* ref "
949            "edges! Any new ref edges would require IPO which "
950            "function passes aren't allowed to do!");
951     bool Inserted = RetainedEdges.insert(RefereeN).second;
952     (void)Inserted;
953     assert(Inserted && "We should never visit a function twice.");
954     if (!E)
955       NewRefEdges.insert(RefereeN);
956     else if (E->isCall())
957       DemotedCallTargets.insert(RefereeN);
958   };
959   LazyCallGraph::visitReferences(Worklist, Visited, VisitRef);
960 
961   // Handle new ref edges.
962   for (Node *RefTarget : NewRefEdges) {
963     SCC &TargetC = *G.lookupSCC(*RefTarget);
964     RefSCC &TargetRC = TargetC.getOuterRefSCC();
965     (void)TargetRC;
966     // TODO: This only allows trivial edges to be added for now.
967 #ifdef EXPENSIVE_CHECKS
968     assert((RC == &TargetRC ||
969            RC->isAncestorOf(TargetRC)) && "New ref edge is not trivial!");
970 #endif
971     RC->insertTrivialRefEdge(N, *RefTarget);
972   }
973 
974   // Handle new call edges.
975   for (Node *CallTarget : NewCallEdges) {
976     SCC &TargetC = *G.lookupSCC(*CallTarget);
977     RefSCC &TargetRC = TargetC.getOuterRefSCC();
978     (void)TargetRC;
979     // TODO: This only allows trivial edges to be added for now.
980 #ifdef EXPENSIVE_CHECKS
981     assert((RC == &TargetRC ||
982            RC->isAncestorOf(TargetRC)) && "New call edge is not trivial!");
983 #endif
984     // Add a trivial ref edge to be promoted later on alongside
985     // PromotedRefTargets.
986     RC->insertTrivialRefEdge(N, *CallTarget);
987   }
988 
989   // Include synthetic reference edges to known, defined lib functions.
990   for (auto *LibFn : G.getLibFunctions())
991     // While the list of lib functions doesn't have repeats, don't re-visit
992     // anything handled above.
993     if (!Visited.count(LibFn))
994       VisitRef(*LibFn);
995 
996   // First remove all of the edges that are no longer present in this function.
997   // The first step makes these edges uniformly ref edges and accumulates them
998   // into a separate data structure so removal doesn't invalidate anything.
999   SmallVector<Node *, 4> DeadTargets;
1000   for (Edge &E : *N) {
1001     if (RetainedEdges.count(&E.getNode()))
1002       continue;
1003 
1004     SCC &TargetC = *G.lookupSCC(E.getNode());
1005     RefSCC &TargetRC = TargetC.getOuterRefSCC();
1006     if (&TargetRC == RC && E.isCall()) {
1007       if (C != &TargetC) {
1008         // For separate SCCs this is trivial.
1009         RC->switchTrivialInternalEdgeToRef(N, E.getNode());
1010       } else {
1011         // Now update the call graph.
1012         C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, E.getNode()),
1013                                    G, N, C, AM, UR);
1014       }
1015     }
1016 
1017     // Now that this is ready for actual removal, put it into our list.
1018     DeadTargets.push_back(&E.getNode());
1019   }
1020   // Remove the easy cases quickly and actually pull them out of our list.
1021   llvm::erase_if(DeadTargets, [&](Node *TargetN) {
1022     SCC &TargetC = *G.lookupSCC(*TargetN);
1023     RefSCC &TargetRC = TargetC.getOuterRefSCC();
1024 
1025     // We can't trivially remove internal targets, so skip
1026     // those.
1027     if (&TargetRC == RC)
1028       return false;
1029 
1030     LLVM_DEBUG(dbgs() << "Deleting outgoing edge from '" << N << "' to '"
1031                       << *TargetN << "'\n");
1032     RC->removeOutgoingEdge(N, *TargetN);
1033     return true;
1034   });
1035 
1036   // Next demote all the call edges that are now ref edges. This helps make
1037   // the SCCs small which should minimize the work below as we don't want to
1038   // form cycles that this would break.
1039   for (Node *RefTarget : DemotedCallTargets) {
1040     SCC &TargetC = *G.lookupSCC(*RefTarget);
1041     RefSCC &TargetRC = TargetC.getOuterRefSCC();
1042 
1043     // The easy case is when the target RefSCC is not this RefSCC. This is
1044     // only supported when the target RefSCC is a child of this RefSCC.
1045     if (&TargetRC != RC) {
1046 #ifdef EXPENSIVE_CHECKS
1047       assert(RC->isAncestorOf(TargetRC) &&
1048              "Cannot potentially form RefSCC cycles here!");
1049 #endif
1050       RC->switchOutgoingEdgeToRef(N, *RefTarget);
1051       LLVM_DEBUG(dbgs() << "Switch outgoing call edge to a ref edge from '" << N
1052                         << "' to '" << *RefTarget << "'\n");
1053       continue;
1054     }
1055 
1056     // We are switching an internal call edge to a ref edge. This may split up
1057     // some SCCs.
1058     if (C != &TargetC) {
1059       // For separate SCCs this is trivial.
1060       RC->switchTrivialInternalEdgeToRef(N, *RefTarget);
1061       continue;
1062     }
1063 
1064     // Now update the call graph.
1065     C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, *RefTarget), G, N,
1066                                C, AM, UR);
1067   }
1068 
1069   // We added a ref edge earlier for new call edges, promote those to call edges
1070   // alongside PromotedRefTargets.
1071   for (Node *E : NewCallEdges)
1072     PromotedRefTargets.insert(E);
1073 
1074   // Now promote ref edges into call edges.
1075   for (Node *CallTarget : PromotedRefTargets) {
1076     SCC &TargetC = *G.lookupSCC(*CallTarget);
1077     RefSCC &TargetRC = TargetC.getOuterRefSCC();
1078 
1079     // The easy case is when the target RefSCC is not this RefSCC. This is
1080     // only supported when the target RefSCC is a child of this RefSCC.
1081     if (&TargetRC != RC) {
1082 #ifdef EXPENSIVE_CHECKS
1083       assert(RC->isAncestorOf(TargetRC) &&
1084              "Cannot potentially form RefSCC cycles here!");
1085 #endif
1086       RC->switchOutgoingEdgeToCall(N, *CallTarget);
1087       LLVM_DEBUG(dbgs() << "Switch outgoing ref edge to a call edge from '" << N
1088                         << "' to '" << *CallTarget << "'\n");
1089       continue;
1090     }
1091     LLVM_DEBUG(dbgs() << "Switch an internal ref edge to a call edge from '"
1092                       << N << "' to '" << *CallTarget << "'\n");
1093 
1094     // Otherwise we are switching an internal ref edge to a call edge. This
1095     // may merge away some SCCs, and we add those to the UpdateResult. We also
1096     // need to make sure to update the worklist in the event SCCs have moved
1097     // before the current one in the post-order sequence
1098     bool HasFunctionAnalysisProxy = false;
1099     auto InitialSCCIndex = RC->find(*C) - RC->begin();
1100     bool FormedCycle = RC->switchInternalEdgeToCall(
1101         N, *CallTarget, [&](ArrayRef<SCC *> MergedSCCs) {
1102           for (SCC *MergedC : MergedSCCs) {
1103             assert(MergedC != &TargetC && "Cannot merge away the target SCC!");
1104 
1105             HasFunctionAnalysisProxy |=
1106                 AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(
1107                     *MergedC) != nullptr;
1108 
1109             // Mark that this SCC will no longer be valid.
1110             UR.InvalidatedSCCs.insert(MergedC);
1111 
1112             // FIXME: We should really do a 'clear' here to forcibly release
1113             // memory, but we don't have a good way of doing that and
1114             // preserving the function analyses.
1115             auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
1116             PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
1117             AM.invalidate(*MergedC, PA);
1118           }
1119         });
1120 
1121     // If we formed a cycle by creating this call, we need to update more data
1122     // structures.
1123     if (FormedCycle) {
1124       C = &TargetC;
1125       assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
1126 
1127       // If one of the invalidated SCCs had a cached proxy to a function
1128       // analysis manager, we need to create a proxy in the new current SCC as
1129       // the invalidated SCCs had their functions moved.
1130       if (HasFunctionAnalysisProxy)
1131         AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, G).updateFAM(FAM);
1132 
1133       // Any analyses cached for this SCC are no longer precise as the shape
1134       // has changed by introducing this cycle. However, we have taken care to
1135       // update the proxies so it remains valide.
1136       auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
1137       PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
1138       AM.invalidate(*C, PA);
1139     }
1140     auto NewSCCIndex = RC->find(*C) - RC->begin();
1141     // If we have actually moved an SCC to be topologically "below" the current
1142     // one due to merging, we will need to revisit the current SCC after
1143     // visiting those moved SCCs.
1144     //
1145     // It is critical that we *do not* revisit the current SCC unless we
1146     // actually move SCCs in the process of merging because otherwise we may
1147     // form a cycle where an SCC is split apart, merged, split, merged and so
1148     // on infinitely.
1149     if (InitialSCCIndex < NewSCCIndex) {
1150       // Put our current SCC back onto the worklist as we'll visit other SCCs
1151       // that are now definitively ordered prior to the current one in the
1152       // post-order sequence, and may end up observing more precise context to
1153       // optimize the current SCC.
1154       UR.CWorklist.insert(C);
1155       LLVM_DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist: " << *C
1156                         << "\n");
1157       // Enqueue in reverse order as we pop off the back of the worklist.
1158       for (SCC &MovedC : llvm::reverse(make_range(RC->begin() + InitialSCCIndex,
1159                                                   RC->begin() + NewSCCIndex))) {
1160         UR.CWorklist.insert(&MovedC);
1161         LLVM_DEBUG(dbgs() << "Enqueuing a newly earlier in post-order SCC: "
1162                           << MovedC << "\n");
1163       }
1164     }
1165   }
1166 
1167   assert(!UR.InvalidatedSCCs.count(C) && "Invalidated the current SCC!");
1168   assert(&C->getOuterRefSCC() == RC && "Current SCC not in current RefSCC!");
1169 
1170   // Record the current SCC for higher layers of the CGSCC pass manager now that
1171   // all the updates have been applied.
1172   if (C != &InitialC)
1173     UR.UpdatedC = C;
1174 
1175   return *C;
1176 }
1177 
1178 LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForFunctionPass(
1179     LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
1180     CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
1181     FunctionAnalysisManager &FAM) {
1182   return updateCGAndAnalysisManagerForPass(G, InitialC, N, AM, UR, FAM,
1183                                            /* FunctionPass */ true);
1184 }
1185 LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForCGSCCPass(
1186     LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
1187     CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
1188     FunctionAnalysisManager &FAM) {
1189   return updateCGAndAnalysisManagerForPass(G, InitialC, N, AM, UR, FAM,
1190                                            /* FunctionPass */ false);
1191 }
1192