LCOV - code coverage report
Current view: top level - lib/Analysis - CGSCCPassManager.cpp (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 213 215 99.1 %
Date: 2017-09-14 15:23:50 Functions: 11 11 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- CGSCCPassManager.cpp - Managing & running CGSCC passes -------------===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : 
      10             : #include "llvm/Analysis/CGSCCPassManager.h"
      11             : #include "llvm/ADT/ArrayRef.h"
      12             : #include "llvm/ADT/Optional.h"
      13             : #include "llvm/ADT/STLExtras.h"
      14             : #include "llvm/ADT/SetVector.h"
      15             : #include "llvm/ADT/SmallPtrSet.h"
      16             : #include "llvm/ADT/SmallVector.h"
      17             : #include "llvm/ADT/iterator_range.h"
      18             : #include "llvm/Analysis/LazyCallGraph.h"
      19             : #include "llvm/IR/CallSite.h"
      20             : #include "llvm/IR/Constant.h"
      21             : #include "llvm/IR/InstIterator.h"
      22             : #include "llvm/IR/Instruction.h"
      23             : #include "llvm/IR/PassManager.h"
      24             : #include "llvm/Support/Casting.h"
      25             : #include "llvm/Support/Debug.h"
      26             : #include "llvm/Support/raw_ostream.h"
      27             : #include <algorithm>
      28             : #include <cassert>
      29             : #include <iterator>
      30             : 
      31             : #define DEBUG_TYPE "cgscc"
      32             : 
      33             : using namespace llvm;
      34             : 
      35             : // Explicit template instantiations and specialization defininitions for core
      36             : // template typedefs.
      37             : namespace llvm {
      38             : 
      39             : // Explicit instantiations for the core proxy templates.
      40             : template class AllAnalysesOn<LazyCallGraph::SCC>;
      41             : template class AnalysisManager<LazyCallGraph::SCC, LazyCallGraph &>;
      42             : template class PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager,
      43             :                            LazyCallGraph &, CGSCCUpdateResult &>;
      44             : template class InnerAnalysisManagerProxy<CGSCCAnalysisManager, Module>;
      45             : template class OuterAnalysisManagerProxy<ModuleAnalysisManager,
      46             :                                          LazyCallGraph::SCC, LazyCallGraph &>;
      47             : template class OuterAnalysisManagerProxy<CGSCCAnalysisManager, Function>;
      48             : 
      49             : /// Explicitly specialize the pass manager run method to handle call graph
      50             : /// updates.
      51             : template <>
      52             : PreservedAnalyses
      53         888 : PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager, LazyCallGraph &,
      54             :             CGSCCUpdateResult &>::run(LazyCallGraph::SCC &InitialC,
      55             :                                       CGSCCAnalysisManager &AM,
      56             :                                       LazyCallGraph &G, CGSCCUpdateResult &UR) {
      57             :   PreservedAnalyses PA = PreservedAnalyses::all();
      58             : 
      59         888 :   if (DebugLogging)
      60         177 :     dbgs() << "Starting CGSCC pass manager run.\n";
      61             : 
      62             :   // The SCC may be refined while we are running passes over it, so set up
      63             :   // a pointer that we can update.
      64         888 :   LazyCallGraph::SCC *C = &InitialC;
      65             : 
      66        4962 :   for (auto &Pass : Passes) {
      67        1410 :     if (DebugLogging)
      68         760 :       dbgs() << "Running pass: " << Pass->name() << " on " << *C << "\n";
      69             : 
      70        2820 :     PreservedAnalyses PassPA = Pass->run(*C, AM, G, UR);
      71             : 
      72             :     // Update the SCC if necessary.
      73        1410 :     C = UR.UpdatedC ? UR.UpdatedC : C;
      74             : 
      75             :     // Check that we didn't miss any update scenario.
      76             :     assert(!UR.InvalidatedSCCs.count(C) && "Processing an invalid SCC!");
      77             :     assert(C->begin() != C->end() && "Cannot have an empty SCC!");
      78             : 
      79             :     // Update the analysis manager as each pass runs and potentially
      80             :     // invalidates analyses.
      81        1410 :     AM.invalidate(*C, PassPA);
      82             : 
      83             :     // Finally, we intersect the final preserved analyses to compute the
      84             :     // aggregate preserved set for this pass manager.
      85        1410 :     PA.intersect(std::move(PassPA));
      86             : 
      87             :     // FIXME: Historically, the pass managers all called the LLVM context's
      88             :     // yield function here. We don't have a generic way to acquire the
      89             :     // context and it isn't yet clear what the right pattern is for yielding
      90             :     // in the new pass manager so it is currently omitted.
      91             :     // ...getContext().yield();
      92             :   }
      93             : 
      94             :   // Invaliadtion was handled after each pass in the above loop for the current
      95             :   // SCC. Therefore, the remaining analysis results in the AnalysisManager are
      96             :   // preserved. We mark this with a set so that we don't need to inspect each
      97             :   // one individually.
      98         888 :   PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
      99             : 
     100         888 :   if (DebugLogging)
     101         177 :     dbgs() << "Finished CGSCC pass manager run.\n";
     102             : 
     103         888 :   return PA;
     104             : }
     105             : 
     106         172 : bool CGSCCAnalysisManagerModuleProxy::Result::invalidate(
     107             :     Module &M, const PreservedAnalyses &PA,
     108             :     ModuleAnalysisManager::Invalidator &Inv) {
     109             :   // If literally everything is preserved, we're done.
     110             :   if (PA.areAllPreserved())
     111             :     return false; // This is still a valid proxy.
     112             : 
     113             :   // If this proxy or the call graph is going to be invalidated, we also need
     114             :   // to clear all the keys coming from that analysis.
     115             :   //
     116             :   // We also directly invalidate the FAM's module proxy if necessary, and if
     117             :   // that proxy isn't preserved we can't preserve this proxy either. We rely on
     118             :   // it to handle module -> function analysis invalidation in the face of
     119             :   // structural changes and so if it's unavailable we conservatively clear the
     120             :   // entire SCC layer as well rather than trying to do invalidation ourselves.
     121         172 :   auto PAC = PA.getChecker<CGSCCAnalysisManagerModuleProxy>();
     122         344 :   if (!(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Module>>()) ||
     123         482 :       Inv.invalidate<LazyCallGraphAnalysis>(M, PA) ||
     124         155 :       Inv.invalidate<FunctionAnalysisManagerModuleProxy>(M, PA)) {
     125          34 :     InnerAM->clear();
     126             : 
     127             :     // And the proxy itself should be marked as invalid so that we can observe
     128             :     // the new call graph. This isn't strictly necessary because we cheat
     129             :     // above, but is still useful.
     130          17 :     return true;
     131             :   }
     132             : 
     133             :   // Directly check if the relevant set is preserved so we can short circuit
     134             :   // invalidating SCCs below.
     135             :   bool AreSCCAnalysesPreserved =
     136         155 :       PA.allAnalysesInSetPreserved<AllAnalysesOn<LazyCallGraph::SCC>>();
     137             : 
     138             :   // Ok, we have a graph, so we can propagate the invalidation down into it.
     139         155 :   G->buildRefSCCs();
     140        1494 :   for (auto &RC : G->postorder_ref_sccs())
     141        3602 :     for (auto &C : RC) {
     142        1220 :       Optional<PreservedAnalyses> InnerPA;
     143             : 
     144             :       // Check to see whether the preserved set needs to be adjusted based on
     145             :       // module-level analysis invalidation triggering deferred invalidation
     146             :       // for this SCC.
     147             :       if (auto *OuterProxy =
     148        1224 :               InnerAM->getCachedResult<ModuleAnalysisManagerCGSCCProxy>(C))
     149             :         for (const auto &OuterInvalidationPair :
     150        1214 :              OuterProxy->getOuterInvalidations()) {
     151          14 :           AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
     152          14 :           const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
     153          14 :           if (Inv.invalidate(OuterAnalysisID, M, PA)) {
     154          14 :             if (!InnerPA)
     155          14 :               InnerPA = PA;
     156          56 :             for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
     157          14 :               InnerPA->abandon(InnerAnalysisID);
     158             :           }
     159             :         }
     160             : 
     161             :       // Check if we needed a custom PA set. If so we'll need to run the inner
     162             :       // invalidation.
     163         631 :       if (InnerPA) {
     164          28 :         InnerAM->invalidate(C, *InnerPA);
     165          14 :         continue;
     166             :       }
     167             : 
     168             :       // Otherwise we only need to do invalidation if the original PA set didn't
     169             :       // preserve all SCC analyses.
     170         603 :       if (!AreSCCAnalysesPreserved)
     171          18 :         InnerAM->invalidate(C, PA);
     172             :     }
     173             : 
     174             :   // Return false to indicate that this result is still a valid proxy.
     175         155 :   return false;
     176             : }
     177             : 
     178             : template <>
     179             : CGSCCAnalysisManagerModuleProxy::Result
     180         214 : CGSCCAnalysisManagerModuleProxy::run(Module &M, ModuleAnalysisManager &AM) {
     181             :   // Force the Function analysis manager to also be available so that it can
     182             :   // be accessed in an SCC analysis and proxied onward to function passes.
     183             :   // FIXME: It is pretty awkward to just drop the result here and assert that
     184             :   // we can find it again later.
     185         214 :   (void)AM.getResult<FunctionAnalysisManagerModuleProxy>(M);
     186             : 
     187         214 :   return Result(*InnerAM, AM.getResult<LazyCallGraphAnalysis>(M));
     188             : }
     189             : 
     190             : AnalysisKey FunctionAnalysisManagerCGSCCProxy::Key;
     191             : 
     192             : FunctionAnalysisManagerCGSCCProxy::Result
     193         750 : FunctionAnalysisManagerCGSCCProxy::run(LazyCallGraph::SCC &C,
     194             :                                        CGSCCAnalysisManager &AM,
     195             :                                        LazyCallGraph &CG) {
     196             :   // Collect the FunctionAnalysisManager from the Module layer and use that to
     197             :   // build the proxy result.
     198             :   //
     199             :   // This allows us to rely on the FunctionAnalysisMangaerModuleProxy to
     200             :   // invalidate the function analyses.
     201        1500 :   auto &MAM = AM.getResult<ModuleAnalysisManagerCGSCCProxy>(C, CG).getManager();
     202        1500 :   Module &M = *C.begin()->getFunction().getParent();
     203         750 :   auto *FAMProxy = MAM.getCachedResult<FunctionAnalysisManagerModuleProxy>(M);
     204             :   assert(FAMProxy && "The CGSCC pass manager requires that the FAM module "
     205             :                      "proxy is run on the module prior to entering the CGSCC "
     206             :                      "walk.");
     207             : 
     208             :   // Note that we special-case invalidation handling of this proxy in the CGSCC
     209             :   // analysis manager's Module proxy. This avoids the need to do anything
     210             :   // special here to recompute all of this if ever the FAM's module proxy goes
     211             :   // away.
     212         750 :   return Result(FAMProxy->getManager());
     213             : }
     214             : 
     215         624 : bool FunctionAnalysisManagerCGSCCProxy::Result::invalidate(
     216             :     LazyCallGraph::SCC &C, const PreservedAnalyses &PA,
     217             :     CGSCCAnalysisManager::Invalidator &Inv) {
     218             :   // If literally everything is preserved, we're done.
     219             :   if (PA.areAllPreserved())
     220             :     return false; // This is still a valid proxy.
     221             : 
     222             :   // If this proxy isn't marked as preserved, then even if the result remains
     223             :   // valid, the key itself may no longer be valid, so we clear everything.
     224             :   //
     225             :   // Note that in order to preserve this proxy, a module pass must ensure that
     226             :   // the FAM has been completely updated to handle the deletion of functions.
     227             :   // Specifically, any FAM-cached results for those functions need to have been
     228             :   // forcibly cleared. When preserved, this proxy will only invalidate results
     229             :   // cached on functions *still in the module* at the end of the module pass.
     230         624 :   auto PAC = PA.getChecker<FunctionAnalysisManagerCGSCCProxy>();
     231         624 :   if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<LazyCallGraph::SCC>>()) {
     232         942 :     for (LazyCallGraph::Node &N : C)
     233         163 :       FAM->clear(N.getFunction());
     234             : 
     235             :     return true;
     236             :   }
     237             : 
     238             :   // Directly check if the relevant set is preserved.
     239             :   bool AreFunctionAnalysesPreserved =
     240         470 :       PA.allAnalysesInSetPreserved<AllAnalysesOn<Function>>();
     241             : 
     242             :   // Now walk all the functions to see if any inner analysis invalidation is
     243             :   // necessary.
     244        3258 :   for (LazyCallGraph::Node &N : C) {
     245         689 :     Function &F = N.getFunction();
     246        1369 :     Optional<PreservedAnalyses> FunctionPA;
     247             : 
     248             :     // Check to see whether the preserved set needs to be pruned based on
     249             :     // SCC-level analysis invalidation that triggers deferred invalidation
     250             :     // registered with the outer analysis manager proxy for this function.
     251             :     if (auto *OuterProxy =
     252         724 :             FAM->getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F))
     253             :       for (const auto &OuterInvalidationPair :
     254          70 :            OuterProxy->getOuterInvalidations()) {
     255          10 :         AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
     256          10 :         const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
     257          10 :         if (Inv.invalidate(OuterAnalysisID, C, PA)) {
     258           9 :           if (!FunctionPA)
     259           9 :             FunctionPA = PA;
     260          36 :           for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
     261           9 :             FunctionPA->abandon(InnerAnalysisID);
     262             :         }
     263             :       }
     264             : 
     265             :     // Check if we needed a custom PA set, and if so we'll need to run the
     266             :     // inner invalidation.
     267         698 :     if (FunctionPA) {
     268          18 :       FAM->invalidate(F, *FunctionPA);
     269           9 :       continue;
     270             :     }
     271             : 
     272             :     // Otherwise we only need to do invalidation if the original PA set didn't
     273             :     // preserve all function analyses.
     274         680 :     if (!AreFunctionAnalysesPreserved)
     275         407 :       FAM->invalidate(F, PA);
     276             :   }
     277             : 
     278             :   // Return false to indicate that this result is still a valid proxy.
     279             :   return false;
     280             : }
     281             : 
     282             : } // end namespace llvm
     283             : 
     284             : /// When a new SCC is created for the graph and there might be function
     285             : /// analysis results cached for the functions now in that SCC two forms of
     286             : /// updates are required.
     287             : ///
     288             : /// First, a proxy from the SCC to the FunctionAnalysisManager needs to be
     289             : /// created so that any subsequent invalidation events to the SCC are
     290             : /// propagated to the function analysis results cached for functions within it.
     291             : ///
     292             : /// Second, if any of the functions within the SCC have analysis results with
     293             : /// outer analysis dependencies, then those dependencies would point to the
     294             : /// *wrong* SCC's analysis result. We forcibly invalidate the necessary
     295             : /// function analyses so that they don't retain stale handles.
     296          46 : static void updateNewSCCFunctionAnalyses(LazyCallGraph::SCC &C,
     297             :                                          LazyCallGraph &G,
     298             :                                          CGSCCAnalysisManager &AM) {
     299             :   // Get the relevant function analysis manager.
     300             :   auto &FAM =
     301          92 :       AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, G).getManager();
     302             : 
     303             :   // Now walk the functions in this SCC and invalidate any function analysis
     304             :   // results that might have outer dependencies on an SCC analysis.
     305         308 :   for (LazyCallGraph::Node &N : C) {
     306          62 :     Function &F = N.getFunction();
     307             : 
     308             :     auto *OuterProxy =
     309           2 :         FAM.getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F);
     310          60 :     if (!OuterProxy)
     311             :       // No outer analyses were queried, nothing to do.
     312          60 :       continue;
     313             : 
     314             :     // Forcibly abandon all the inner analyses with dependencies, but
     315             :     // invalidate nothing else.
     316           4 :     auto PA = PreservedAnalyses::all();
     317             :     for (const auto &OuterInvalidationPair :
     318           4 :          OuterProxy->getOuterInvalidations()) {
     319           2 :       const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
     320           8 :       for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
     321           2 :         PA.abandon(InnerAnalysisID);
     322             :     }
     323             : 
     324             :     // Now invalidate anything we found.
     325           2 :     FAM.invalidate(F, PA);
     326             :   }
     327          46 : }
     328             : 
     329             : /// Helper function to update both the \c CGSCCAnalysisManager \p AM and the \c
     330             : /// CGSCCPassManager's \c CGSCCUpdateResult \p UR based on a range of newly
     331             : /// added SCCs.
     332             : ///
     333             : /// The range of new SCCs must be in postorder already. The SCC they were split
     334             : /// out of must be provided as \p C. The current node being mutated and
     335             : /// triggering updates must be passed as \p N.
     336             : ///
     337             : /// This function returns the SCC containing \p N. This will be either \p C if
     338             : /// no new SCCs have been split out, or it will be the new SCC containing \p N.
     339             : template <typename SCCRangeT>
     340             : static LazyCallGraph::SCC *
     341          45 : incorporateNewSCCRange(const SCCRangeT &NewSCCRange, LazyCallGraph &G,
     342             :                        LazyCallGraph::Node &N, LazyCallGraph::SCC *C,
     343             :                        CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR) {
     344             :   using SCC = LazyCallGraph::SCC;
     345             : 
     346          45 :   if (NewSCCRange.begin() == NewSCCRange.end())
     347          13 :     return C;
     348             : 
     349             :   // Add the current SCC to the worklist as its shape has changed.
     350          32 :   UR.CWorklist.insert(C);
     351             :   DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist:" << *C << "\n");
     352             : 
     353          32 :   SCC *OldC = C;
     354             : 
     355             :   // Update the current SCC. Note that if we have new SCCs, this must actually
     356             :   // change the SCC.
     357             :   assert(C != &*NewSCCRange.begin() &&
     358             :          "Cannot insert new SCCs without changing current SCC!");
     359          64 :   C = &*NewSCCRange.begin();
     360             :   assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
     361             : 
     362             :   // If we had a cached FAM proxy originally, we will want to create more of
     363             :   // them for each SCC that was split off.
     364          32 :   bool NeedFAMProxy =
     365          32 :       AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(*OldC) != nullptr;
     366             : 
     367             :   // We need to propagate an invalidation call to all but the newly current SCC
     368             :   // because the outer pass manager won't do that for us after splitting them.
     369             :   // FIXME: We should accept a PreservedAnalysis from the CG updater so that if
     370             :   // there are preserved ananalyses we can avoid invalidating them here for
     371             :   // split-off SCCs.
     372             :   // We know however that this will preserve any FAM proxy so go ahead and mark
     373             :   // that.
     374          64 :   PreservedAnalyses PA;
     375          32 :   PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
     376          32 :   AM.invalidate(*OldC, PA);
     377             : 
     378             :   // Ensure the now-current SCC's function analyses are updated.
     379          32 :   if (NeedFAMProxy)
     380          32 :     updateNewSCCFunctionAnalyses(*C, G, AM);
     381             : 
     382         220 :   for (SCC &NewC : llvm::reverse(make_range(std::next(NewSCCRange.begin()),
     383             :                                             NewSCCRange.end()))) {
     384             :     assert(C != &NewC && "No need to re-visit the current SCC!");
     385             :     assert(OldC != &NewC && "Already handled the original SCC!");
     386          14 :     UR.CWorklist.insert(&NewC);
     387             :     DEBUG(dbgs() << "Enqueuing a newly formed SCC:" << NewC << "\n");
     388             : 
     389             :     // Ensure new SCCs' function analyses are updated.
     390          14 :     if (NeedFAMProxy)
     391          14 :       updateNewSCCFunctionAnalyses(NewC, G, AM);
     392             : 
     393             :     // Also propagate a normal invalidation to the new SCC as only the current
     394             :     // will get one from the pass manager infrastructure.
     395          14 :     AM.invalidate(NewC, PA);
     396             :   }
     397          32 :   return C;
     398             : }
     399             : 
     400         387 : LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForFunctionPass(
     401             :     LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
     402             :     CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR) {
     403             :   using Node = LazyCallGraph::Node;
     404             :   using Edge = LazyCallGraph::Edge;
     405             :   using SCC = LazyCallGraph::SCC;
     406             :   using RefSCC = LazyCallGraph::RefSCC;
     407             : 
     408         387 :   RefSCC &InitialRC = InitialC.getOuterRefSCC();
     409         387 :   SCC *C = &InitialC;
     410         387 :   RefSCC *RC = &InitialRC;
     411         387 :   Function &F = N.getFunction();
     412             : 
     413             :   // Walk the function body and build up the set of retained, promoted, and
     414             :   // demoted edges.
     415         774 :   SmallVector<Constant *, 16> Worklist;
     416         774 :   SmallPtrSet<Constant *, 16> Visited;
     417         774 :   SmallPtrSet<Node *, 16> RetainedEdges;
     418         774 :   SmallSetVector<Node *, 4> PromotedRefTargets;
     419         774 :   SmallSetVector<Node *, 4> DemotedCallTargets;
     420             : 
     421             :   // First walk the function and handle all called functions. We do this first
     422             :   // because if there is a single call edge, whether there are ref edges is
     423             :   // irrelevant.
     424        8894 :   for (Instruction &I : instructions(F))
     425        8120 :     if (auto CS = CallSite(&I))
     426        1767 :       if (Function *Callee = CS.getCalledFunction())
     427        1767 :         if (Visited.insert(Callee).second && !Callee->isDeclaration()) {
     428         162 :           Node &CalleeN = *G.lookup(*Callee);
     429         162 :           Edge *E = N->lookup(CalleeN);
     430             :           // FIXME: We should really handle adding new calls. While it will
     431             :           // make downstream usage more complex, there is no fundamental
     432             :           // limitation and it will allow passes within the CGSCC to be a bit
     433             :           // more flexible in what transforms they can do. Until then, we
     434             :           // verify that new calls haven't been introduced.
     435             :           assert(E && "No function transformations should introduce *new* "
     436             :                       "call edges! Any new calls should be modeled as "
     437             :                       "promoted existing ref edges!");
     438         162 :           bool Inserted = RetainedEdges.insert(&CalleeN).second;
     439             :           (void)Inserted;
     440             :           assert(Inserted && "We should never visit a function twice.");
     441         162 :           if (!E->isCall())
     442          58 :             PromotedRefTargets.insert(&CalleeN);
     443             :         }
     444             : 
     445             :   // Now walk all references.
     446        8894 :   for (Instruction &I : instructions(F))
     447       24710 :     for (Value *Op : I.operand_values())
     448        6265 :       if (auto *C = dyn_cast<Constant>(Op))
     449        3038 :         if (Visited.insert(C).second)
     450         691 :           Worklist.push_back(C);
     451             : 
     452          61 :   auto VisitRef = [&](Function &Referee) {
     453         122 :     Node &RefereeN = *G.lookup(Referee);
     454         122 :     Edge *E = N->lookup(RefereeN);
     455             :     // FIXME: Similarly to new calls, we also currently preclude
     456             :     // introducing new references. See above for details.
     457             :     assert(E && "No function transformations should introduce *new* ref "
     458             :                 "edges! Any new ref edges would require IPO which "
     459             :                 "function passes aren't allowed to do!");
     460          61 :     bool Inserted = RetainedEdges.insert(&RefereeN).second;
     461             :     (void)Inserted;
     462             :     assert(Inserted && "We should never visit a function twice.");
     463          61 :     if (E->isCall())
     464          13 :       DemotedCallTargets.insert(&RefereeN);
     465         448 :   };
     466         387 :   LazyCallGraph::visitReferences(Worklist, Visited, VisitRef);
     467             : 
     468             :   // Include synthetic reference edges to known, defined lib functions.
     469         795 :   for (auto *F : G.getLibFunctions())
     470             :     // While the list of lib functions doesn't have repeats, don't re-visit
     471             :     // anything handled above.
     472          21 :     if (!Visited.count(F))
     473          19 :       VisitRef(*F);
     474             : 
     475             :   // First remove all of the edges that are no longer present in this function.
     476             :   // The first step makes these edges uniformly ref edges and accumulates them
     477             :   // into a separate data structure so removal doesn't invalidate anything.
     478         774 :   SmallVector<Node *, 4> DeadTargets;
     479        1277 :   for (Edge &E : *N) {
     480         503 :     if (RetainedEdges.count(&E.getNode()))
     481         223 :       continue;
     482             : 
     483         560 :     SCC &TargetC = *G.lookupSCC(E.getNode());
     484         280 :     RefSCC &TargetRC = TargetC.getOuterRefSCC();
     485         321 :     if (&TargetRC == RC && E.isCall()) {
     486          37 :       if (C != &TargetC) {
     487             :         // For separate SCCs this is trivial.
     488           4 :         RC->switchTrivialInternalEdgeToRef(N, E.getNode());
     489             :       } else {
     490             :         // Now update the call graph.
     491          70 :         C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, E.getNode()),
     492             :                                    G, N, C, AM, UR);
     493             :       }
     494             :     }
     495             : 
     496             :     // Now that this is ready for actual removal, put it into our list.
     497         280 :     DeadTargets.push_back(&E.getNode());
     498             :   }
     499             :   // Remove the easy cases quickly and actually pull them out of our list.
     500         774 :   DeadTargets.erase(
     501         387 :       llvm::remove_if(DeadTargets,
     502         280 :                       [&](Node *TargetN) {
     503         560 :                         SCC &TargetC = *G.lookupSCC(*TargetN);
     504         280 :                         RefSCC &TargetRC = TargetC.getOuterRefSCC();
     505             : 
     506             :                         // We can't trivially remove internal targets, so skip
     507             :                         // those.
     508         280 :                         if (&TargetRC == RC)
     509             :                           return false;
     510             : 
     511         239 :                         RC->removeOutgoingEdge(N, *TargetN);
     512             :                         DEBUG(dbgs() << "Deleting outgoing edge from '" << N
     513             :                                      << "' to '" << TargetN << "'\n");
     514         239 :                         return true;
     515             :                       }),
     516         387 :       DeadTargets.end());
     517             : 
     518             :   // Now do a batch removal of the internal ref edges left.
     519        1161 :   auto NewRefSCCs = RC->removeInternalRefEdge(N, DeadTargets);
     520         387 :   if (!NewRefSCCs.empty()) {
     521             :     // The old RefSCC is dead, mark it as such.
     522          17 :     UR.InvalidatedRefSCCs.insert(RC);
     523             : 
     524             :     // Note that we don't bother to invalidate analyses as ref-edge
     525             :     // connectivity is not really observable in any way and is intended
     526             :     // exclusively to be used for ordering of transforms rather than for
     527             :     // analysis conclusions.
     528             : 
     529             :     // Update RC to the "bottom".
     530             :     assert(G.lookupSCC(N) == C && "Changed the SCC when splitting RefSCCs!");
     531          17 :     RC = &C->getOuterRefSCC();
     532             :     assert(G.lookupRefSCC(N) == RC && "Failed to update current RefSCC!");
     533             : 
     534             :     // The RC worklist is in reverse postorder, so we enqueue the new ones in
     535             :     // RPO except for the one which contains the source node as that is the
     536             :     // "bottom" we will continue processing in the bottom-up walk.
     537             :     assert(NewRefSCCs.front() == RC &&
     538             :            "New current RefSCC not first in the returned list!");
     539          34 :     for (RefSCC *NewRC : llvm::reverse(make_range(std::next(NewRefSCCs.begin()),
     540         165 :                                                   NewRefSCCs.end()))) {
     541             :       assert(NewRC != RC && "Should not encounter the current RefSCC further "
     542             :                             "in the postorder list of new RefSCCs.");
     543          23 :       UR.RCWorklist.insert(NewRC);
     544             :       DEBUG(dbgs() << "Enqueuing a new RefSCC in the update worklist: "
     545             :                    << *NewRC << "\n");
     546             :     }
     547             :   }
     548             : 
     549             :   // Next demote all the call edges that are now ref edges. This helps make
     550             :   // the SCCs small which should minimize the work below as we don't want to
     551             :   // form cycles that this would break.
     552        1174 :   for (Node *RefTarget : DemotedCallTargets) {
     553          13 :     SCC &TargetC = *G.lookupSCC(*RefTarget);
     554          13 :     RefSCC &TargetRC = TargetC.getOuterRefSCC();
     555             : 
     556             :     // The easy case is when the target RefSCC is not this RefSCC. This is
     557             :     // only supported when the target RefSCC is a child of this RefSCC.
     558          16 :     if (&TargetRC != RC) {
     559             :       assert(RC->isAncestorOf(TargetRC) &&
     560             :              "Cannot potentially form RefSCC cycles here!");
     561           3 :       RC->switchOutgoingEdgeToRef(N, *RefTarget);
     562             :       DEBUG(dbgs() << "Switch outgoing call edge to a ref edge from '" << N
     563             :                    << "' to '" << *RefTarget << "'\n");
     564           3 :       continue;
     565             :     }
     566             : 
     567             :     // We are switching an internal call edge to a ref edge. This may split up
     568             :     // some SCCs.
     569          10 :     if (C != &TargetC) {
     570             :       // For separate SCCs this is trivial.
     571           0 :       RC->switchTrivialInternalEdgeToRef(N, *RefTarget);
     572           0 :       continue;
     573             :     }
     574             : 
     575             :     // Now update the call graph.
     576          10 :     C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, *RefTarget), G, N,
     577             :                                C, AM, UR);
     578             :   }
     579             : 
     580             :   // Now promote ref edges into call edges.
     581        1219 :   for (Node *CallTarget : PromotedRefTargets) {
     582          58 :     SCC &TargetC = *G.lookupSCC(*CallTarget);
     583          58 :     RefSCC &TargetRC = TargetC.getOuterRefSCC();
     584             : 
     585             :     // The easy case is when the target RefSCC is not this RefSCC. This is
     586             :     // only supported when the target RefSCC is a child of this RefSCC.
     587          61 :     if (&TargetRC != RC) {
     588             :       assert(RC->isAncestorOf(TargetRC) &&
     589             :              "Cannot potentially form RefSCC cycles here!");
     590           3 :       RC->switchOutgoingEdgeToCall(N, *CallTarget);
     591             :       DEBUG(dbgs() << "Switch outgoing ref edge to a call edge from '" << N
     592             :                    << "' to '" << *CallTarget << "'\n");
     593           3 :       continue;
     594             :     }
     595             :     DEBUG(dbgs() << "Switch an internal ref edge to a call edge from '" << N
     596             :                  << "' to '" << *CallTarget << "'\n");
     597             : 
     598             :     // Otherwise we are switching an internal ref edge to a call edge. This
     599             :     // may merge away some SCCs, and we add those to the UpdateResult. We also
     600             :     // need to make sure to update the worklist in the event SCCs have moved
     601             :     // before the current one in the post-order sequence
     602          55 :     bool HasFunctionAnalysisProxy = false;
     603         220 :     auto InitialSCCIndex = RC->find(*C) - RC->begin();
     604         165 :     bool FormedCycle = RC->switchInternalEdgeToCall(
     605          22 :         N, *CallTarget, [&](ArrayRef<SCC *> MergedSCCs) {
     606          66 :           for (SCC *MergedC : MergedSCCs) {
     607             :             assert(MergedC != &TargetC && "Cannot merge away the target SCC!");
     608             : 
     609          22 :             HasFunctionAnalysisProxy |=
     610          66 :                 AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(
     611          22 :                     *MergedC) != nullptr;
     612             : 
     613             :             // Mark that this SCC will no longer be valid.
     614          22 :             UR.InvalidatedSCCs.insert(MergedC);
     615             : 
     616             :             // FIXME: We should really do a 'clear' here to forcibly release
     617             :             // memory, but we don't have a good way of doing that and
     618             :             // preserving the function analyses.
     619          44 :             auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
     620          22 :             PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
     621          22 :             AM.invalidate(*MergedC, PA);
     622             :           }
     623          77 :         });
     624             : 
     625             :     // If we formed a cycle by creating this call, we need to update more data
     626             :     // structures.
     627          55 :     if (FormedCycle) {
     628          20 :       C = &TargetC;
     629             :       assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
     630             : 
     631             :       // If one of the invalidated SCCs had a cached proxy to a function
     632             :       // analysis manager, we need to create a proxy in the new current SCC as
     633             :       // the invaliadted SCCs had their functions moved.
     634          20 :       if (HasFunctionAnalysisProxy)
     635          20 :         AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, G);
     636             : 
     637             :       // Any analyses cached for this SCC are no longer precise as the shape
     638             :       // has changed by introducing this cycle. However, we have taken care to
     639             :       // update the proxies so it remains valide.
     640          40 :       auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
     641          20 :       PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
     642          20 :       AM.invalidate(*C, PA);
     643             :     }
     644         220 :     auto NewSCCIndex = RC->find(*C) - RC->begin();
     645             :     // If we have actually moved an SCC to be topologically "below" the current
     646             :     // one due to merging, we will need to revisit the current SCC after
     647             :     // visiting those moved SCCs.
     648             :     //
     649             :     // It is critical that we *do not* revisit the current SCC unless we
     650             :     // actually move SCCs in the process of merging because otherwise we may
     651             :     // form a cycle where an SCC is split apart, merged, split, merged and so
     652             :     // on infinitely.
     653          55 :     if (InitialSCCIndex < NewSCCIndex) {
     654             :       // Put our current SCC back onto the worklist as we'll visit other SCCs
     655             :       // that are now definitively ordered prior to the current one in the
     656             :       // post-order sequence, and may end up observing more precise context to
     657             :       // optimize the current SCC.
     658           2 :       UR.CWorklist.insert(C);
     659             :       DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist: " << *C
     660             :                    << "\n");
     661             :       // Enqueue in reverse order as we pop off the back of the worklist.
     662           6 :       for (SCC &MovedC : llvm::reverse(make_range(RC->begin() + InitialSCCIndex,
     663          20 :                                                   RC->begin() + NewSCCIndex))) {
     664           2 :         UR.CWorklist.insert(&MovedC);
     665             :         DEBUG(dbgs() << "Enqueuing a newly earlier in post-order SCC: "
     666             :                      << MovedC << "\n");
     667             :       }
     668             :     }
     669             :   }
     670             : 
     671             :   assert(!UR.InvalidatedSCCs.count(C) && "Invalidated the current SCC!");
     672             :   assert(!UR.InvalidatedRefSCCs.count(RC) && "Invalidated the current RefSCC!");
     673             :   assert(&C->getOuterRefSCC() == RC && "Current SCC not in current RefSCC!");
     674             : 
     675             :   // Record the current RefSCC and SCC for higher layers of the CGSCC pass
     676             :   // manager now that all the updates have been applied.
     677         387 :   if (RC != &InitialRC)
     678          17 :     UR.UpdatedRC = RC;
     679         387 :   if (C != &InitialC)
     680          36 :     UR.UpdatedC = C;
     681             : 
     682         774 :   return *C;
     683             : }

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