xref: /llvm-project/llvm/lib/Analysis/CGSCCPassManager.cpp (revision 236fda550d36d35a00785938c3e38b0f402aeda6)
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/raw_ostream.h"
29 #include <cassert>
30 #include <optional>
31 
32 #define DEBUG_TYPE "cgscc"
33 
34 using namespace llvm;
35 
36 // Explicit template instantiations and specialization definitions for core
37 // template typedefs.
38 namespace llvm {
39 static cl::opt<bool> AbortOnMaxDevirtIterationsReached(
40     "abort-on-max-devirt-iterations-reached",
41     cl::desc("Abort when the max iterations for devirtualization CGSCC repeat "
42              "pass is reached"));
43 
44 AnalysisKey ShouldNotRunFunctionPassesAnalysis::Key;
45 
46 // Explicit instantiations for the core proxy templates.
47 template class AllAnalysesOn<LazyCallGraph::SCC>;
48 template class AnalysisManager<LazyCallGraph::SCC, LazyCallGraph &>;
49 template class PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager,
50                            LazyCallGraph &, CGSCCUpdateResult &>;
51 template class InnerAnalysisManagerProxy<CGSCCAnalysisManager, Module>;
52 template class OuterAnalysisManagerProxy<ModuleAnalysisManager,
53                                          LazyCallGraph::SCC, LazyCallGraph &>;
54 template class OuterAnalysisManagerProxy<CGSCCAnalysisManager, Function>;
55 
56 /// Explicitly specialize the pass manager run method to handle call graph
57 /// updates.
58 template <>
59 PreservedAnalyses
60 PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager, LazyCallGraph &,
61             CGSCCUpdateResult &>::run(LazyCallGraph::SCC &InitialC,
62                                       CGSCCAnalysisManager &AM,
63                                       LazyCallGraph &G, CGSCCUpdateResult &UR) {
64   // Request PassInstrumentation from analysis manager, will use it to run
65   // instrumenting callbacks for the passes later.
66   PassInstrumentation PI =
67       AM.getResult<PassInstrumentationAnalysis>(InitialC, G);
68 
69   PreservedAnalyses PA = PreservedAnalyses::all();
70 
71   // The SCC may be refined while we are running passes over it, so set up
72   // a pointer that we can update.
73   LazyCallGraph::SCC *C = &InitialC;
74 
75   // Get Function analysis manager from its proxy.
76   FunctionAnalysisManager &FAM =
77       AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(*C)->getManager();
78 
79   for (auto &Pass : Passes) {
80     // Check the PassInstrumentation's BeforePass callbacks before running the
81     // pass, skip its execution completely if asked to (callback returns false).
82     if (!PI.runBeforePass(*Pass, *C))
83       continue;
84 
85     PreservedAnalyses PassPA = Pass->run(*C, AM, G, UR);
86 
87     // Update the SCC if necessary.
88     C = UR.UpdatedC ? UR.UpdatedC : C;
89     if (UR.UpdatedC) {
90       // If C is updated, also create a proxy and update FAM inside the result.
91       auto *ResultFAMCP =
92           &AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, G);
93       ResultFAMCP->updateFAM(FAM);
94     }
95 
96     // Intersect the final preserved analyses to compute the aggregate
97     // preserved set for this pass manager.
98     PA.intersect(PassPA);
99 
100     // If the CGSCC pass wasn't able to provide a valid updated SCC, the
101     // current SCC may simply need to be skipped if invalid.
102     if (UR.InvalidatedSCCs.count(C)) {
103       PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
104       LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
105       break;
106     }
107 
108     // Check that we didn't miss any update scenario.
109     assert(C->begin() != C->end() && "Cannot have an empty SCC!");
110 
111     // Update the analysis manager as each pass runs and potentially
112     // invalidates analyses.
113     AM.invalidate(*C, PassPA);
114 
115     PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
116   }
117 
118   // Before we mark all of *this* SCC's analyses as preserved below, intersect
119   // this with the cross-SCC preserved analysis set. This is used to allow
120   // CGSCC passes to mutate ancestor SCCs and still trigger proper invalidation
121   // for them.
122   UR.CrossSCCPA.intersect(PA);
123 
124   // Invalidation was handled after each pass in the above loop for the current
125   // SCC. Therefore, the remaining analysis results in the AnalysisManager are
126   // preserved. We mark this with a set so that we don't need to inspect each
127   // one individually.
128   PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
129 
130   return PA;
131 }
132 
133 PreservedAnalyses
134 ModuleToPostOrderCGSCCPassAdaptor::run(Module &M, ModuleAnalysisManager &AM) {
135   // Setup the CGSCC analysis manager from its proxy.
136   CGSCCAnalysisManager &CGAM =
137       AM.getResult<CGSCCAnalysisManagerModuleProxy>(M).getManager();
138 
139   // Get the call graph for this module.
140   LazyCallGraph &CG = AM.getResult<LazyCallGraphAnalysis>(M);
141 
142   // Get Function analysis manager from its proxy.
143   FunctionAnalysisManager &FAM =
144       AM.getCachedResult<FunctionAnalysisManagerModuleProxy>(M)->getManager();
145 
146   // We keep worklists to allow us to push more work onto the pass manager as
147   // the passes are run.
148   SmallPriorityWorklist<LazyCallGraph::RefSCC *, 1> RCWorklist;
149   SmallPriorityWorklist<LazyCallGraph::SCC *, 1> CWorklist;
150 
151   // Keep sets for invalidated SCCs that should be skipped when
152   // iterating off the worklists.
153   SmallPtrSet<LazyCallGraph::SCC *, 4> InvalidSCCSet;
154 
155   SmallDenseSet<std::pair<LazyCallGraph::Node *, LazyCallGraph::SCC *>, 4>
156       InlinedInternalEdges;
157 
158   SmallVector<Function *, 4> DeadFunctions;
159 
160   CGSCCUpdateResult UR = {CWorklist,
161                           InvalidSCCSet,
162                           nullptr,
163                           PreservedAnalyses::all(),
164                           InlinedInternalEdges,
165                           DeadFunctions,
166                           {}};
167 
168   // Request PassInstrumentation from analysis manager, will use it to run
169   // instrumenting callbacks for the passes later.
170   PassInstrumentation PI = AM.getResult<PassInstrumentationAnalysis>(M);
171 
172   PreservedAnalyses PA = PreservedAnalyses::all();
173   CG.buildRefSCCs();
174   for (LazyCallGraph::RefSCC &RC :
175        llvm::make_early_inc_range(CG.postorder_ref_sccs())) {
176     assert(RCWorklist.empty() &&
177            "Should always start with an empty RefSCC worklist");
178     // The postorder_ref_sccs range we are walking is lazily constructed, so
179     // we only push the first one onto the worklist. The worklist allows us
180     // to capture *new* RefSCCs created during transformations.
181     //
182     // We really want to form RefSCCs lazily because that makes them cheaper
183     // to update as the program is simplified and allows us to have greater
184     // cache locality as forming a RefSCC touches all the parts of all the
185     // functions within that RefSCC.
186     //
187     // We also eagerly increment the iterator to the next position because
188     // the CGSCC passes below may delete the current RefSCC.
189     RCWorklist.insert(&RC);
190 
191     do {
192       LazyCallGraph::RefSCC *RC = RCWorklist.pop_back_val();
193       assert(CWorklist.empty() &&
194              "Should always start with an empty SCC worklist");
195 
196       LLVM_DEBUG(dbgs() << "Running an SCC pass across the RefSCC: " << *RC
197                         << "\n");
198 
199       // The top of the worklist may *also* be the same SCC we just ran over
200       // (and invalidated for). Keep track of that last SCC we processed due
201       // to SCC update to avoid redundant processing when an SCC is both just
202       // updated itself and at the top of the worklist.
203       LazyCallGraph::SCC *LastUpdatedC = nullptr;
204 
205       // Push the initial SCCs in reverse post-order as we'll pop off the
206       // back and so see this in post-order.
207       for (LazyCallGraph::SCC &C : llvm::reverse(*RC))
208         CWorklist.insert(&C);
209 
210       do {
211         LazyCallGraph::SCC *C = CWorklist.pop_back_val();
212         // Due to call graph mutations, we may have invalid SCCs or SCCs from
213         // other RefSCCs in the worklist. The invalid ones are dead and the
214         // other RefSCCs should be queued above, so we just need to skip both
215         // scenarios here.
216         if (InvalidSCCSet.count(C)) {
217           LLVM_DEBUG(dbgs() << "Skipping an invalid SCC...\n");
218           continue;
219         }
220         if (LastUpdatedC == C) {
221           LLVM_DEBUG(dbgs() << "Skipping redundant run on SCC: " << *C << "\n");
222           continue;
223         }
224         // We used to also check if the current SCC is part of the current
225         // RefSCC and bail if it wasn't, since it should be in RCWorklist.
226         // However, this can cause compile time explosions in some cases on
227         // modules with a huge RefSCC. If a non-trivial amount of SCCs in the
228         // huge RefSCC can become their own child RefSCC, we create one child
229         // RefSCC, bail on the current RefSCC, visit the child RefSCC, revisit
230         // the huge RefSCC, and repeat. By visiting all SCCs in the original
231         // RefSCC we create all the child RefSCCs in one pass of the RefSCC,
232         // rather one pass of the RefSCC creating one child RefSCC at a time.
233 
234         // Ensure we can proxy analysis updates from the CGSCC analysis manager
235         // into the Function analysis manager by getting a proxy here.
236         // This also needs to update the FunctionAnalysisManager, as this may be
237         // the first time we see this SCC.
238         CGAM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, CG).updateFAM(
239             FAM);
240 
241         // Each time we visit a new SCC pulled off the worklist,
242         // a transformation of a child SCC may have also modified this parent
243         // and invalidated analyses. So we invalidate using the update record's
244         // cross-SCC preserved set. This preserved set is intersected by any
245         // CGSCC pass that handles invalidation (primarily pass managers) prior
246         // to marking its SCC as preserved. That lets us track everything that
247         // might need invalidation across SCCs without excessive invalidations
248         // on a single SCC.
249         //
250         // This essentially allows SCC passes to freely invalidate analyses
251         // of any ancestor SCC. If this becomes detrimental to successfully
252         // caching analyses, we could force each SCC pass to manually
253         // invalidate the analyses for any SCCs other than themselves which
254         // are mutated. However, that seems to lose the robustness of the
255         // pass-manager driven invalidation scheme.
256         CGAM.invalidate(*C, UR.CrossSCCPA);
257 
258         do {
259           // Check that we didn't miss any update scenario.
260           assert(!InvalidSCCSet.count(C) && "Processing an invalid SCC!");
261           assert(C->begin() != C->end() && "Cannot have an empty SCC!");
262 
263           LastUpdatedC = UR.UpdatedC;
264           UR.UpdatedC = nullptr;
265 
266           // Check the PassInstrumentation's BeforePass callbacks before
267           // running the pass, skip its execution completely if asked to
268           // (callback returns false).
269           if (!PI.runBeforePass<LazyCallGraph::SCC>(*Pass, *C))
270             continue;
271 
272           PreservedAnalyses PassPA = Pass->run(*C, CGAM, CG, UR);
273 
274           // Update the SCC and RefSCC if necessary.
275           C = UR.UpdatedC ? UR.UpdatedC : C;
276 
277           if (UR.UpdatedC) {
278             // If we're updating the SCC, also update the FAM inside the proxy's
279             // result.
280             CGAM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, CG).updateFAM(
281                 FAM);
282           }
283 
284           // Intersect with the cross-SCC preserved set to capture any
285           // cross-SCC invalidation.
286           UR.CrossSCCPA.intersect(PassPA);
287           // Intersect the preserved set so that invalidation of module
288           // analyses will eventually occur when the module pass completes.
289           PA.intersect(PassPA);
290 
291           // If the CGSCC pass wasn't able to provide a valid updated SCC,
292           // the current SCC may simply need to be skipped if invalid.
293           if (UR.InvalidatedSCCs.count(C)) {
294             PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
295             LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
296             break;
297           }
298 
299           // Check that we didn't miss any update scenario.
300           assert(C->begin() != C->end() && "Cannot have an empty SCC!");
301 
302           // We handle invalidating the CGSCC analysis manager's information
303           // for the (potentially updated) SCC here. Note that any other SCCs
304           // whose structure has changed should have been invalidated by
305           // whatever was updating the call graph. This SCC gets invalidated
306           // late as it contains the nodes that were actively being
307           // processed.
308           CGAM.invalidate(*C, PassPA);
309 
310           PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
311 
312           // The pass may have restructured the call graph and refined the
313           // current SCC and/or RefSCC. We need to update our current SCC and
314           // RefSCC pointers to follow these. Also, when the current SCC is
315           // refined, re-run the SCC pass over the newly refined SCC in order
316           // to observe the most precise SCC model available. This inherently
317           // cannot cycle excessively as it only happens when we split SCCs
318           // apart, at most converging on a DAG of single nodes.
319           // FIXME: If we ever start having RefSCC passes, we'll want to
320           // iterate there too.
321           if (UR.UpdatedC)
322             LLVM_DEBUG(dbgs()
323                        << "Re-running SCC passes after a refinement of the "
324                           "current SCC: "
325                        << *UR.UpdatedC << "\n");
326 
327           // Note that both `C` and `RC` may at this point refer to deleted,
328           // invalid SCC and RefSCCs respectively. But we will short circuit
329           // the processing when we check them in the loop above.
330         } while (UR.UpdatedC);
331       } while (!CWorklist.empty());
332 
333       // We only need to keep internal inlined edge information within
334       // a RefSCC, clear it to save on space and let the next time we visit
335       // any of these functions have a fresh start.
336       InlinedInternalEdges.clear();
337     } while (!RCWorklist.empty());
338   }
339 
340   CG.removeDeadFunctions(DeadFunctions);
341   for (Function *DeadF : DeadFunctions)
342     DeadF->eraseFromParent();
343 
344 #if defined(EXPENSIVE_CHECKS)
345   // Verify that the call graph is still valid.
346   CG.verify();
347 #endif
348 
349   // By definition we preserve the call garph, all SCC analyses, and the
350   // analysis proxies by handling them above and in any nested pass managers.
351   PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
352   PA.preserve<LazyCallGraphAnalysis>();
353   PA.preserve<CGSCCAnalysisManagerModuleProxy>();
354   PA.preserve<FunctionAnalysisManagerModuleProxy>();
355   return PA;
356 }
357 
358 PreservedAnalyses DevirtSCCRepeatedPass::run(LazyCallGraph::SCC &InitialC,
359                                              CGSCCAnalysisManager &AM,
360                                              LazyCallGraph &CG,
361                                              CGSCCUpdateResult &UR) {
362   PreservedAnalyses PA = PreservedAnalyses::all();
363   PassInstrumentation PI =
364       AM.getResult<PassInstrumentationAnalysis>(InitialC, CG);
365 
366   // The SCC may be refined while we are running passes over it, so set up
367   // a pointer that we can update.
368   LazyCallGraph::SCC *C = &InitialC;
369 
370   // Struct to track the counts of direct and indirect calls in each function
371   // of the SCC.
372   struct CallCount {
373     int Direct;
374     int Indirect;
375   };
376 
377   // Put value handles on all of the indirect calls and return the number of
378   // direct calls for each function in the SCC.
379   auto ScanSCC = [](LazyCallGraph::SCC &C,
380                     SmallMapVector<Value *, WeakTrackingVH, 16> &CallHandles) {
381     assert(CallHandles.empty() && "Must start with a clear set of handles.");
382 
383     SmallDenseMap<Function *, CallCount> CallCounts;
384     CallCount CountLocal = {0, 0};
385     for (LazyCallGraph::Node &N : C) {
386       CallCount &Count =
387           CallCounts.insert(std::make_pair(&N.getFunction(), CountLocal))
388               .first->second;
389       for (Instruction &I : instructions(N.getFunction()))
390         if (auto *CB = dyn_cast<CallBase>(&I)) {
391           if (CB->getCalledFunction()) {
392             ++Count.Direct;
393           } else {
394             ++Count.Indirect;
395             CallHandles.insert({CB, WeakTrackingVH(CB)});
396           }
397         }
398     }
399 
400     return CallCounts;
401   };
402 
403   UR.IndirectVHs.clear();
404   // Populate the initial call handles and get the initial call counts.
405   auto CallCounts = ScanSCC(*C, UR.IndirectVHs);
406 
407   for (int Iteration = 0;; ++Iteration) {
408     if (!PI.runBeforePass<LazyCallGraph::SCC>(*Pass, *C))
409       continue;
410 
411     PreservedAnalyses PassPA = Pass->run(*C, AM, CG, UR);
412 
413     PA.intersect(PassPA);
414 
415     // If the CGSCC pass wasn't able to provide a valid updated SCC, the
416     // current SCC may simply need to be skipped if invalid.
417     if (UR.InvalidatedSCCs.count(C)) {
418       PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
419       LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
420       break;
421     }
422 
423     // Update the analysis manager with each run and intersect the total set
424     // of preserved analyses so we're ready to iterate.
425     AM.invalidate(*C, PassPA);
426 
427     PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
428 
429     // If the SCC structure has changed, bail immediately and let the outer
430     // CGSCC layer handle any iteration to reflect the refined structure.
431     if (UR.UpdatedC && UR.UpdatedC != C)
432       break;
433 
434     assert(C->begin() != C->end() && "Cannot have an empty SCC!");
435 
436     // Check whether any of the handles were devirtualized.
437     bool Devirt = llvm::any_of(UR.IndirectVHs, [](auto &P) -> bool {
438       if (P.second) {
439         if (CallBase *CB = dyn_cast<CallBase>(P.second)) {
440           if (CB->getCalledFunction()) {
441             LLVM_DEBUG(dbgs() << "Found devirtualized call: " << *CB << "\n");
442             return true;
443           }
444         }
445       }
446       return false;
447     });
448 
449     // Rescan to build up a new set of handles and count how many direct
450     // calls remain. If we decide to iterate, this also sets up the input to
451     // the next iteration.
452     UR.IndirectVHs.clear();
453     auto NewCallCounts = ScanSCC(*C, UR.IndirectVHs);
454 
455     // If we haven't found an explicit devirtualization already see if we
456     // have decreased the number of indirect calls and increased the number
457     // of direct calls for any function in the SCC. This can be fooled by all
458     // manner of transformations such as DCE and other things, but seems to
459     // work well in practice.
460     if (!Devirt)
461       // Iterate over the keys in NewCallCounts, if Function also exists in
462       // CallCounts, make the check below.
463       for (auto &Pair : NewCallCounts) {
464         auto &CallCountNew = Pair.second;
465         auto CountIt = CallCounts.find(Pair.first);
466         if (CountIt != CallCounts.end()) {
467           const auto &CallCountOld = CountIt->second;
468           if (CallCountOld.Indirect > CallCountNew.Indirect &&
469               CallCountOld.Direct < CallCountNew.Direct) {
470             Devirt = true;
471             break;
472           }
473         }
474       }
475 
476     if (!Devirt) {
477       break;
478     }
479 
480     // Otherwise, if we've already hit our max, we're done.
481     if (Iteration >= MaxIterations) {
482       if (AbortOnMaxDevirtIterationsReached)
483         report_fatal_error("Max devirtualization iterations reached");
484       LLVM_DEBUG(
485           dbgs() << "Found another devirtualization after hitting the max "
486                     "number of repetitions ("
487                  << MaxIterations << ") on SCC: " << *C << "\n");
488       break;
489     }
490 
491     LLVM_DEBUG(
492         dbgs() << "Repeating an SCC pass after finding a devirtualization in: "
493                << *C << "\n");
494 
495     // Move over the new call counts in preparation for iterating.
496     CallCounts = std::move(NewCallCounts);
497   }
498 
499   // Note that we don't add any preserved entries here unlike a more normal
500   // "pass manager" because we only handle invalidation *between* iterations,
501   // not after the last iteration.
502   return PA;
503 }
504 
505 PreservedAnalyses CGSCCToFunctionPassAdaptor::run(LazyCallGraph::SCC &C,
506                                                   CGSCCAnalysisManager &AM,
507                                                   LazyCallGraph &CG,
508                                                   CGSCCUpdateResult &UR) {
509   // Setup the function analysis manager from its proxy.
510   FunctionAnalysisManager &FAM =
511       AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, CG).getManager();
512 
513   SmallVector<LazyCallGraph::Node *, 4> Nodes;
514   for (LazyCallGraph::Node &N : C)
515     Nodes.push_back(&N);
516 
517   // The SCC may get split while we are optimizing functions due to deleting
518   // edges. If this happens, the current SCC can shift, so keep track of
519   // a pointer we can overwrite.
520   LazyCallGraph::SCC *CurrentC = &C;
521 
522   LLVM_DEBUG(dbgs() << "Running function passes across an SCC: " << C << "\n");
523 
524   PreservedAnalyses PA = PreservedAnalyses::all();
525   for (LazyCallGraph::Node *N : Nodes) {
526     // Skip nodes from other SCCs. These may have been split out during
527     // processing. We'll eventually visit those SCCs and pick up the nodes
528     // there.
529     if (CG.lookupSCC(*N) != CurrentC)
530       continue;
531 
532     Function &F = N->getFunction();
533 
534     if (NoRerun && FAM.getCachedResult<ShouldNotRunFunctionPassesAnalysis>(F))
535       continue;
536 
537     PassInstrumentation PI = FAM.getResult<PassInstrumentationAnalysis>(F);
538     if (!PI.runBeforePass<Function>(*Pass, F))
539       continue;
540 
541     PreservedAnalyses PassPA = Pass->run(F, FAM);
542 
543     // We know that the function pass couldn't have invalidated any other
544     // function's analyses (that's the contract of a function pass), so
545     // directly handle the function analysis manager's invalidation here.
546     FAM.invalidate(F, EagerlyInvalidate ? PreservedAnalyses::none() : PassPA);
547 
548     PI.runAfterPass<Function>(*Pass, F, PassPA);
549 
550     // Then intersect the preserved set so that invalidation of module
551     // analyses will eventually occur when the module pass completes.
552     PA.intersect(std::move(PassPA));
553 
554     // If the call graph hasn't been preserved, update it based on this
555     // function pass. This may also update the current SCC to point to
556     // a smaller, more refined SCC.
557     auto PAC = PA.getChecker<LazyCallGraphAnalysis>();
558     if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<Module>>()) {
559       CurrentC = &updateCGAndAnalysisManagerForFunctionPass(CG, *CurrentC, *N,
560                                                             AM, UR, FAM);
561       assert(CG.lookupSCC(*N) == CurrentC &&
562              "Current SCC not updated to the SCC containing the current node!");
563     }
564   }
565 
566   // By definition we preserve the proxy. And we preserve all analyses on
567   // Functions. This precludes *any* invalidation of function analyses by the
568   // proxy, but that's OK because we've taken care to invalidate analyses in
569   // the function analysis manager incrementally above.
570   PA.preserveSet<AllAnalysesOn<Function>>();
571   PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
572 
573   // We've also ensured that we updated the call graph along the way.
574   PA.preserve<LazyCallGraphAnalysis>();
575 
576   return PA;
577 }
578 
579 bool CGSCCAnalysisManagerModuleProxy::Result::invalidate(
580     Module &M, const PreservedAnalyses &PA,
581     ModuleAnalysisManager::Invalidator &Inv) {
582   // If literally everything is preserved, we're done.
583   if (PA.areAllPreserved())
584     return false; // This is still a valid proxy.
585 
586   // If this proxy or the call graph is going to be invalidated, we also need
587   // to clear all the keys coming from that analysis.
588   //
589   // We also directly invalidate the FAM's module proxy if necessary, and if
590   // that proxy isn't preserved we can't preserve this proxy either. We rely on
591   // it to handle module -> function analysis invalidation in the face of
592   // structural changes and so if it's unavailable we conservatively clear the
593   // entire SCC layer as well rather than trying to do invalidation ourselves.
594   auto PAC = PA.getChecker<CGSCCAnalysisManagerModuleProxy>();
595   if (!(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Module>>()) ||
596       Inv.invalidate<LazyCallGraphAnalysis>(M, PA) ||
597       Inv.invalidate<FunctionAnalysisManagerModuleProxy>(M, PA)) {
598     InnerAM->clear();
599 
600     // And the proxy itself should be marked as invalid so that we can observe
601     // the new call graph. This isn't strictly necessary because we cheat
602     // above, but is still useful.
603     return true;
604   }
605 
606   // Directly check if the relevant set is preserved so we can short circuit
607   // invalidating SCCs below.
608   bool AreSCCAnalysesPreserved =
609       PA.allAnalysesInSetPreserved<AllAnalysesOn<LazyCallGraph::SCC>>();
610 
611   // Ok, we have a graph, so we can propagate the invalidation down into it.
612   G->buildRefSCCs();
613   for (auto &RC : G->postorder_ref_sccs())
614     for (auto &C : RC) {
615       std::optional<PreservedAnalyses> InnerPA;
616 
617       // Check to see whether the preserved set needs to be adjusted based on
618       // module-level analysis invalidation triggering deferred invalidation
619       // for this SCC.
620       if (auto *OuterProxy =
621               InnerAM->getCachedResult<ModuleAnalysisManagerCGSCCProxy>(C))
622         for (const auto &OuterInvalidationPair :
623              OuterProxy->getOuterInvalidations()) {
624           AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
625           const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
626           if (Inv.invalidate(OuterAnalysisID, M, PA)) {
627             if (!InnerPA)
628               InnerPA = PA;
629             for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
630               InnerPA->abandon(InnerAnalysisID);
631           }
632         }
633 
634       // Check if we needed a custom PA set. If so we'll need to run the inner
635       // invalidation.
636       if (InnerPA) {
637         InnerAM->invalidate(C, *InnerPA);
638         continue;
639       }
640 
641       // Otherwise we only need to do invalidation if the original PA set didn't
642       // preserve all SCC analyses.
643       if (!AreSCCAnalysesPreserved)
644         InnerAM->invalidate(C, PA);
645     }
646 
647   // Return false to indicate that this result is still a valid proxy.
648   return false;
649 }
650 
651 template <>
652 CGSCCAnalysisManagerModuleProxy::Result
653 CGSCCAnalysisManagerModuleProxy::run(Module &M, ModuleAnalysisManager &AM) {
654   // Force the Function analysis manager to also be available so that it can
655   // be accessed in an SCC analysis and proxied onward to function passes.
656   // FIXME: It is pretty awkward to just drop the result here and assert that
657   // we can find it again later.
658   (void)AM.getResult<FunctionAnalysisManagerModuleProxy>(M);
659 
660   return Result(*InnerAM, AM.getResult<LazyCallGraphAnalysis>(M));
661 }
662 
663 AnalysisKey FunctionAnalysisManagerCGSCCProxy::Key;
664 
665 FunctionAnalysisManagerCGSCCProxy::Result
666 FunctionAnalysisManagerCGSCCProxy::run(LazyCallGraph::SCC &C,
667                                        CGSCCAnalysisManager &AM,
668                                        LazyCallGraph &CG) {
669   // Note: unconditionally getting checking that the proxy exists may get it at
670   // this point. There are cases when this is being run unnecessarily, but
671   // it is cheap and having the assertion in place is more valuable.
672   auto &MAMProxy = AM.getResult<ModuleAnalysisManagerCGSCCProxy>(C, CG);
673   Module &M = *C.begin()->getFunction().getParent();
674   bool ProxyExists =
675       MAMProxy.cachedResultExists<FunctionAnalysisManagerModuleProxy>(M);
676   assert(ProxyExists &&
677          "The CGSCC pass manager requires that the FAM module proxy is run "
678          "on the module prior to entering the CGSCC walk");
679   (void)ProxyExists;
680 
681   // We just return an empty result. The caller will use the updateFAM interface
682   // to correctly register the relevant FunctionAnalysisManager based on the
683   // context in which this proxy is run.
684   return Result();
685 }
686 
687 bool FunctionAnalysisManagerCGSCCProxy::Result::invalidate(
688     LazyCallGraph::SCC &C, const PreservedAnalyses &PA,
689     CGSCCAnalysisManager::Invalidator &Inv) {
690   // If literally everything is preserved, we're done.
691   if (PA.areAllPreserved())
692     return false; // This is still a valid proxy.
693 
694   // All updates to preserve valid results are done below, so we don't need to
695   // invalidate this proxy.
696   //
697   // Note that in order to preserve this proxy, a module pass must ensure that
698   // the FAM has been completely updated to handle the deletion of functions.
699   // Specifically, any FAM-cached results for those functions need to have been
700   // forcibly cleared. When preserved, this proxy will only invalidate results
701   // cached on functions *still in the module* at the end of the module pass.
702   auto PAC = PA.getChecker<FunctionAnalysisManagerCGSCCProxy>();
703   if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<LazyCallGraph::SCC>>()) {
704     for (LazyCallGraph::Node &N : C)
705       FAM->invalidate(N.getFunction(), PA);
706 
707     return false;
708   }
709 
710   // Directly check if the relevant set is preserved.
711   bool AreFunctionAnalysesPreserved =
712       PA.allAnalysesInSetPreserved<AllAnalysesOn<Function>>();
713 
714   // Now walk all the functions to see if any inner analysis invalidation is
715   // necessary.
716   for (LazyCallGraph::Node &N : C) {
717     Function &F = N.getFunction();
718     std::optional<PreservedAnalyses> FunctionPA;
719 
720     // Check to see whether the preserved set needs to be pruned based on
721     // SCC-level analysis invalidation that triggers deferred invalidation
722     // registered with the outer analysis manager proxy for this function.
723     if (auto *OuterProxy =
724             FAM->getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F))
725       for (const auto &OuterInvalidationPair :
726            OuterProxy->getOuterInvalidations()) {
727         AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
728         const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
729         if (Inv.invalidate(OuterAnalysisID, C, PA)) {
730           if (!FunctionPA)
731             FunctionPA = PA;
732           for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
733             FunctionPA->abandon(InnerAnalysisID);
734         }
735       }
736 
737     // Check if we needed a custom PA set, and if so we'll need to run the
738     // inner invalidation.
739     if (FunctionPA) {
740       FAM->invalidate(F, *FunctionPA);
741       continue;
742     }
743 
744     // Otherwise we only need to do invalidation if the original PA set didn't
745     // preserve all function analyses.
746     if (!AreFunctionAnalysesPreserved)
747       FAM->invalidate(F, PA);
748   }
749 
750   // Return false to indicate that this result is still a valid proxy.
751   return false;
752 }
753 
754 } // end namespace llvm
755 
756 /// When a new SCC is created for the graph we first update the
757 /// FunctionAnalysisManager in the Proxy's result.
758 /// As there might be function analysis results cached for the functions now in
759 /// that SCC, two forms of  updates are required.
760 ///
761 /// First, a proxy from the SCC to the FunctionAnalysisManager needs to be
762 /// created so that any subsequent invalidation events to the SCC are
763 /// propagated to the function analysis results cached for functions within it.
764 ///
765 /// Second, if any of the functions within the SCC have analysis results with
766 /// outer analysis dependencies, then those dependencies would point to the
767 /// *wrong* SCC's analysis result. We forcibly invalidate the necessary
768 /// function analyses so that they don't retain stale handles.
769 static void updateNewSCCFunctionAnalyses(LazyCallGraph::SCC &C,
770                                          LazyCallGraph &G,
771                                          CGSCCAnalysisManager &AM,
772                                          FunctionAnalysisManager &FAM) {
773   AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, G).updateFAM(FAM);
774 
775   // Now walk the functions in this SCC and invalidate any function analysis
776   // results that might have outer dependencies on an SCC analysis.
777   for (LazyCallGraph::Node &N : C) {
778     Function &F = N.getFunction();
779 
780     auto *OuterProxy =
781         FAM.getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F);
782     if (!OuterProxy)
783       // No outer analyses were queried, nothing to do.
784       continue;
785 
786     // Forcibly abandon all the inner analyses with dependencies, but
787     // invalidate nothing else.
788     auto PA = PreservedAnalyses::all();
789     for (const auto &OuterInvalidationPair :
790          OuterProxy->getOuterInvalidations()) {
791       const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
792       for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
793         PA.abandon(InnerAnalysisID);
794     }
795 
796     // Now invalidate anything we found.
797     FAM.invalidate(F, PA);
798   }
799 }
800 
801 /// Helper function to update both the \c CGSCCAnalysisManager \p AM and the \c
802 /// CGSCCPassManager's \c CGSCCUpdateResult \p UR based on a range of newly
803 /// added SCCs.
804 ///
805 /// The range of new SCCs must be in postorder already. The SCC they were split
806 /// out of must be provided as \p C. The current node being mutated and
807 /// triggering updates must be passed as \p N.
808 ///
809 /// This function returns the SCC containing \p N. This will be either \p C if
810 /// no new SCCs have been split out, or it will be the new SCC containing \p N.
811 template <typename SCCRangeT>
812 static LazyCallGraph::SCC *
813 incorporateNewSCCRange(const SCCRangeT &NewSCCRange, LazyCallGraph &G,
814                        LazyCallGraph::Node &N, LazyCallGraph::SCC *C,
815                        CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR) {
816   using SCC = LazyCallGraph::SCC;
817 
818   if (NewSCCRange.empty())
819     return C;
820 
821   // Add the current SCC to the worklist as its shape has changed.
822   UR.CWorklist.insert(C);
823   LLVM_DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist:" << *C
824                     << "\n");
825 
826   SCC *OldC = C;
827 
828   // Update the current SCC. Note that if we have new SCCs, this must actually
829   // change the SCC.
830   assert(C != &*NewSCCRange.begin() &&
831          "Cannot insert new SCCs without changing current SCC!");
832   C = &*NewSCCRange.begin();
833   assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
834 
835   // If we had a cached FAM proxy originally, we will want to create more of
836   // them for each SCC that was split off.
837   FunctionAnalysisManager *FAM = nullptr;
838   if (auto *FAMProxy =
839           AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(*OldC))
840     FAM = &FAMProxy->getManager();
841 
842   // We need to propagate an invalidation call to all but the newly current SCC
843   // because the outer pass manager won't do that for us after splitting them.
844   // FIXME: We should accept a PreservedAnalysis from the CG updater so that if
845   // there are preserved analysis we can avoid invalidating them here for
846   // split-off SCCs.
847   // We know however that this will preserve any FAM proxy so go ahead and mark
848   // that.
849   auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
850   PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
851   AM.invalidate(*OldC, PA);
852 
853   // Ensure the now-current SCC's function analyses are updated.
854   if (FAM)
855     updateNewSCCFunctionAnalyses(*C, G, AM, *FAM);
856 
857   for (SCC &NewC : llvm::reverse(llvm::drop_begin(NewSCCRange))) {
858     assert(C != &NewC && "No need to re-visit the current SCC!");
859     assert(OldC != &NewC && "Already handled the original SCC!");
860     UR.CWorklist.insert(&NewC);
861     LLVM_DEBUG(dbgs() << "Enqueuing a newly formed SCC:" << NewC << "\n");
862 
863     // Ensure new SCCs' function analyses are updated.
864     if (FAM)
865       updateNewSCCFunctionAnalyses(NewC, G, AM, *FAM);
866 
867     // Also propagate a normal invalidation to the new SCC as only the current
868     // will get one from the pass manager infrastructure.
869     AM.invalidate(NewC, PA);
870   }
871   return C;
872 }
873 
874 static LazyCallGraph::SCC &updateCGAndAnalysisManagerForPass(
875     LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
876     CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
877     FunctionAnalysisManager &FAM, bool FunctionPass) {
878   using Node = LazyCallGraph::Node;
879   using Edge = LazyCallGraph::Edge;
880   using SCC = LazyCallGraph::SCC;
881   using RefSCC = LazyCallGraph::RefSCC;
882 
883   RefSCC &InitialRC = InitialC.getOuterRefSCC();
884   SCC *C = &InitialC;
885   RefSCC *RC = &InitialRC;
886   Function &F = N.getFunction();
887 
888   // Walk the function body and build up the set of retained, promoted, and
889   // demoted edges.
890   SmallVector<Constant *, 16> Worklist;
891   SmallPtrSet<Constant *, 16> Visited;
892   SmallPtrSet<Node *, 16> RetainedEdges;
893   SmallSetVector<Node *, 4> PromotedRefTargets;
894   SmallSetVector<Node *, 4> DemotedCallTargets;
895   SmallSetVector<Node *, 4> NewCallEdges;
896   SmallSetVector<Node *, 4> NewRefEdges;
897 
898   // First walk the function and handle all called functions. We do this first
899   // because if there is a single call edge, whether there are ref edges is
900   // irrelevant.
901   for (Instruction &I : instructions(F)) {
902     if (auto *CB = dyn_cast<CallBase>(&I)) {
903       if (Function *Callee = CB->getCalledFunction()) {
904         if (Visited.insert(Callee).second && !Callee->isDeclaration()) {
905           Node *CalleeN = G.lookup(*Callee);
906           assert(CalleeN &&
907                  "Visited function should already have an associated node");
908           Edge *E = N->lookup(*CalleeN);
909           assert((E || !FunctionPass) &&
910                  "No function transformations should introduce *new* "
911                  "call edges! Any new calls should be modeled as "
912                  "promoted existing ref edges!");
913           bool Inserted = RetainedEdges.insert(CalleeN).second;
914           (void)Inserted;
915           assert(Inserted && "We should never visit a function twice.");
916           if (!E)
917             NewCallEdges.insert(CalleeN);
918           else if (!E->isCall())
919             PromotedRefTargets.insert(CalleeN);
920         }
921       } else {
922         // We can miss devirtualization if an indirect call is created then
923         // promoted before updateCGAndAnalysisManagerForPass runs.
924         auto *Entry = UR.IndirectVHs.find(CB);
925         if (Entry == UR.IndirectVHs.end())
926           UR.IndirectVHs.insert({CB, WeakTrackingVH(CB)});
927         else if (!Entry->second)
928           Entry->second = WeakTrackingVH(CB);
929       }
930     }
931   }
932 
933   // Now walk all references.
934   for (Instruction &I : instructions(F))
935     for (Value *Op : I.operand_values())
936       if (auto *OpC = dyn_cast<Constant>(Op))
937         if (Visited.insert(OpC).second)
938           Worklist.push_back(OpC);
939 
940   auto VisitRef = [&](Function &Referee) {
941     Node *RefereeN = G.lookup(Referee);
942     assert(RefereeN &&
943            "Visited function should already have an associated node");
944     Edge *E = N->lookup(*RefereeN);
945     assert((E || !FunctionPass) &&
946            "No function transformations should introduce *new* ref "
947            "edges! Any new ref edges would require IPO which "
948            "function passes aren't allowed to do!");
949     bool Inserted = RetainedEdges.insert(RefereeN).second;
950     (void)Inserted;
951     assert(Inserted && "We should never visit a function twice.");
952     if (!E)
953       NewRefEdges.insert(RefereeN);
954     else if (E->isCall())
955       DemotedCallTargets.insert(RefereeN);
956   };
957   LazyCallGraph::visitReferences(Worklist, Visited, VisitRef);
958 
959   // Handle new ref edges.
960   for (Node *RefTarget : NewRefEdges) {
961     SCC &TargetC = *G.lookupSCC(*RefTarget);
962     RefSCC &TargetRC = TargetC.getOuterRefSCC();
963     (void)TargetRC;
964     // TODO: This only allows trivial edges to be added for now.
965 #ifdef EXPENSIVE_CHECKS
966     assert((RC == &TargetRC ||
967            RC->isAncestorOf(TargetRC)) && "New ref edge is not trivial!");
968 #endif
969     RC->insertTrivialRefEdge(N, *RefTarget);
970   }
971 
972   // Handle new call edges.
973   for (Node *CallTarget : NewCallEdges) {
974     SCC &TargetC = *G.lookupSCC(*CallTarget);
975     RefSCC &TargetRC = TargetC.getOuterRefSCC();
976     (void)TargetRC;
977     // TODO: This only allows trivial edges to be added for now.
978 #ifdef EXPENSIVE_CHECKS
979     assert((RC == &TargetRC ||
980            RC->isAncestorOf(TargetRC)) && "New call edge is not trivial!");
981 #endif
982     // Add a trivial ref edge to be promoted later on alongside
983     // PromotedRefTargets.
984     RC->insertTrivialRefEdge(N, *CallTarget);
985   }
986 
987   // Include synthetic reference edges to known, defined lib functions.
988   for (auto *LibFn : G.getLibFunctions())
989     // While the list of lib functions doesn't have repeats, don't re-visit
990     // anything handled above.
991     if (!Visited.count(LibFn))
992       VisitRef(*LibFn);
993 
994   // First remove all of the edges that are no longer present in this function.
995   // The first step makes these edges uniformly ref edges and accumulates them
996   // into a separate data structure so removal doesn't invalidate anything.
997   SmallVector<Node *, 4> DeadTargets;
998   for (Edge &E : *N) {
999     if (RetainedEdges.count(&E.getNode()))
1000       continue;
1001 
1002     SCC &TargetC = *G.lookupSCC(E.getNode());
1003     RefSCC &TargetRC = TargetC.getOuterRefSCC();
1004     if (&TargetRC == RC && E.isCall()) {
1005       if (C != &TargetC) {
1006         // For separate SCCs this is trivial.
1007         RC->switchTrivialInternalEdgeToRef(N, E.getNode());
1008       } else {
1009         // Now update the call graph.
1010         C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, E.getNode()),
1011                                    G, N, C, AM, UR);
1012       }
1013     }
1014 
1015     // Now that this is ready for actual removal, put it into our list.
1016     DeadTargets.push_back(&E.getNode());
1017   }
1018   // Remove the easy cases quickly and actually pull them out of our list.
1019   llvm::erase_if(DeadTargets, [&](Node *TargetN) {
1020     SCC &TargetC = *G.lookupSCC(*TargetN);
1021     RefSCC &TargetRC = TargetC.getOuterRefSCC();
1022 
1023     // We can't trivially remove internal targets, so skip
1024     // those.
1025     if (&TargetRC == RC)
1026       return false;
1027 
1028     LLVM_DEBUG(dbgs() << "Deleting outgoing edge from '" << N << "' to '"
1029                       << *TargetN << "'\n");
1030     RC->removeOutgoingEdge(N, *TargetN);
1031     return true;
1032   });
1033 
1034   // Next demote all the call edges that are now ref edges. This helps make
1035   // the SCCs small which should minimize the work below as we don't want to
1036   // form cycles that this would break.
1037   for (Node *RefTarget : DemotedCallTargets) {
1038     SCC &TargetC = *G.lookupSCC(*RefTarget);
1039     RefSCC &TargetRC = TargetC.getOuterRefSCC();
1040 
1041     // The easy case is when the target RefSCC is not this RefSCC. This is
1042     // only supported when the target RefSCC is a child of this RefSCC.
1043     if (&TargetRC != RC) {
1044 #ifdef EXPENSIVE_CHECKS
1045       assert(RC->isAncestorOf(TargetRC) &&
1046              "Cannot potentially form RefSCC cycles here!");
1047 #endif
1048       RC->switchOutgoingEdgeToRef(N, *RefTarget);
1049       LLVM_DEBUG(dbgs() << "Switch outgoing call edge to a ref edge from '" << N
1050                         << "' to '" << *RefTarget << "'\n");
1051       continue;
1052     }
1053 
1054     // We are switching an internal call edge to a ref edge. This may split up
1055     // some SCCs.
1056     if (C != &TargetC) {
1057       // For separate SCCs this is trivial.
1058       RC->switchTrivialInternalEdgeToRef(N, *RefTarget);
1059       continue;
1060     }
1061 
1062     // Now update the call graph.
1063     C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, *RefTarget), G, N,
1064                                C, AM, UR);
1065   }
1066 
1067   // We added a ref edge earlier for new call edges, promote those to call edges
1068   // alongside PromotedRefTargets.
1069   for (Node *E : NewCallEdges)
1070     PromotedRefTargets.insert(E);
1071 
1072   // Now promote ref edges into call edges.
1073   for (Node *CallTarget : PromotedRefTargets) {
1074     SCC &TargetC = *G.lookupSCC(*CallTarget);
1075     RefSCC &TargetRC = TargetC.getOuterRefSCC();
1076 
1077     // The easy case is when the target RefSCC is not this RefSCC. This is
1078     // only supported when the target RefSCC is a child of this RefSCC.
1079     if (&TargetRC != RC) {
1080 #ifdef EXPENSIVE_CHECKS
1081       assert(RC->isAncestorOf(TargetRC) &&
1082              "Cannot potentially form RefSCC cycles here!");
1083 #endif
1084       RC->switchOutgoingEdgeToCall(N, *CallTarget);
1085       LLVM_DEBUG(dbgs() << "Switch outgoing ref edge to a call edge from '" << N
1086                         << "' to '" << *CallTarget << "'\n");
1087       continue;
1088     }
1089     LLVM_DEBUG(dbgs() << "Switch an internal ref edge to a call edge from '"
1090                       << N << "' to '" << *CallTarget << "'\n");
1091 
1092     // Otherwise we are switching an internal ref edge to a call edge. This
1093     // may merge away some SCCs, and we add those to the UpdateResult. We also
1094     // need to make sure to update the worklist in the event SCCs have moved
1095     // before the current one in the post-order sequence
1096     bool HasFunctionAnalysisProxy = false;
1097     auto InitialSCCIndex = RC->find(*C) - RC->begin();
1098     bool FormedCycle = RC->switchInternalEdgeToCall(
1099         N, *CallTarget, [&](ArrayRef<SCC *> MergedSCCs) {
1100           for (SCC *MergedC : MergedSCCs) {
1101             assert(MergedC != &TargetC && "Cannot merge away the target SCC!");
1102 
1103             HasFunctionAnalysisProxy |=
1104                 AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(
1105                     *MergedC) != nullptr;
1106 
1107             // Mark that this SCC will no longer be valid.
1108             UR.InvalidatedSCCs.insert(MergedC);
1109 
1110             // FIXME: We should really do a 'clear' here to forcibly release
1111             // memory, but we don't have a good way of doing that and
1112             // preserving the function analyses.
1113             auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
1114             PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
1115             AM.invalidate(*MergedC, PA);
1116           }
1117         });
1118 
1119     // If we formed a cycle by creating this call, we need to update more data
1120     // structures.
1121     if (FormedCycle) {
1122       C = &TargetC;
1123       assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
1124 
1125       // If one of the invalidated SCCs had a cached proxy to a function
1126       // analysis manager, we need to create a proxy in the new current SCC as
1127       // the invalidated SCCs had their functions moved.
1128       if (HasFunctionAnalysisProxy)
1129         AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, G).updateFAM(FAM);
1130 
1131       // Any analyses cached for this SCC are no longer precise as the shape
1132       // has changed by introducing this cycle. However, we have taken care to
1133       // update the proxies so it remains valide.
1134       auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
1135       PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
1136       AM.invalidate(*C, PA);
1137     }
1138     auto NewSCCIndex = RC->find(*C) - RC->begin();
1139     // If we have actually moved an SCC to be topologically "below" the current
1140     // one due to merging, we will need to revisit the current SCC after
1141     // visiting those moved SCCs.
1142     //
1143     // It is critical that we *do not* revisit the current SCC unless we
1144     // actually move SCCs in the process of merging because otherwise we may
1145     // form a cycle where an SCC is split apart, merged, split, merged and so
1146     // on infinitely.
1147     if (InitialSCCIndex < NewSCCIndex) {
1148       // Put our current SCC back onto the worklist as we'll visit other SCCs
1149       // that are now definitively ordered prior to the current one in the
1150       // post-order sequence, and may end up observing more precise context to
1151       // optimize the current SCC.
1152       UR.CWorklist.insert(C);
1153       LLVM_DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist: " << *C
1154                         << "\n");
1155       // Enqueue in reverse order as we pop off the back of the worklist.
1156       for (SCC &MovedC : llvm::reverse(make_range(RC->begin() + InitialSCCIndex,
1157                                                   RC->begin() + NewSCCIndex))) {
1158         UR.CWorklist.insert(&MovedC);
1159         LLVM_DEBUG(dbgs() << "Enqueuing a newly earlier in post-order SCC: "
1160                           << MovedC << "\n");
1161       }
1162     }
1163   }
1164 
1165   assert(!UR.InvalidatedSCCs.count(C) && "Invalidated the current SCC!");
1166   assert(&C->getOuterRefSCC() == RC && "Current SCC not in current RefSCC!");
1167 
1168   // Record the current SCC for higher layers of the CGSCC pass manager now that
1169   // all the updates have been applied.
1170   if (C != &InitialC)
1171     UR.UpdatedC = C;
1172 
1173   return *C;
1174 }
1175 
1176 LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForFunctionPass(
1177     LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
1178     CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
1179     FunctionAnalysisManager &FAM) {
1180   return updateCGAndAnalysisManagerForPass(G, InitialC, N, AM, UR, FAM,
1181                                            /* FunctionPass */ true);
1182 }
1183 LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForCGSCCPass(
1184     LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
1185     CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
1186     FunctionAnalysisManager &FAM) {
1187   return updateCGAndAnalysisManagerForPass(G, InitialC, N, AM, UR, FAM,
1188                                            /* FunctionPass */ false);
1189 }
1190