1 //===- CGSCCPassManager.h - Call graph pass management ----------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// This header provides classes for managing passes over SCCs of the call
12 /// graph. These passes form an important component of LLVM's interprocedural
13 /// optimizations. Because they operate on the SCCs of the call graph, and they
14 /// traverse the graph in post-order, they can effectively do pair-wise
15 /// interprocedural optimizations for all call edges in the program while
16 /// incrementally refining it and improving the context of these pair-wise
17 /// optimizations. At each call site edge, the callee has already been
18 /// optimized as much as is possible. This in turn allows very accurate
19 /// analysis of it for IPO.
21 /// A secondary more general goal is to be able to isolate optimization on
22 /// unrelated parts of the IR module. This is useful to ensure our
23 /// optimizations are principled and don't miss oportunities where refinement
24 /// of one part of the module influence transformations in another part of the
25 /// module. But this is also useful if we want to parallelize the optimizations
26 /// across common large module graph shapes which tend to be very wide and have
27 /// large regions of unrelated cliques.
29 /// To satisfy these goals, we use the LazyCallGraph which provides two graphs
30 /// nested inside each other (and built lazily from the bottom-up): the call
31 /// graph proper, and a reference graph. The reference graph is super set of
32 /// the call graph and is a conservative approximation of what could through
33 /// scalar or CGSCC transforms *become* the call graph. Using this allows us to
34 /// ensure we optimize functions prior to them being introduced into the call
35 /// graph by devirtualization or other technique, and thus ensures that
36 /// subsequent pair-wise interprocedural optimizations observe the optimized
37 /// form of these functions. The (potentially transitive) reference
38 /// reachability used by the reference graph is a conservative approximation
39 /// that still allows us to have independent regions of the graph.
41 /// FIXME: There is one major drawback of the reference graph: in its naive
42 /// form it is quadratic because it contains a distinct edge for each
43 /// (potentially indirect) reference, even if are all through some common
44 /// global table of function pointers. This can be fixed in a number of ways
45 /// that essentially preserve enough of the normalization. While it isn't
46 /// expected to completely preclude the usability of this, it will need to be
50 /// All of these issues are made substantially more complex in the face of
51 /// mutations to the call graph while optimization passes are being run. When
52 /// mutations to the call graph occur we want to achieve two different things:
54 /// - We need to update the call graph in-flight and invalidate analyses
55 /// cached on entities in the graph. Because of the cache-based analysis
56 /// design of the pass manager, it is essential to have stable identities for
57 /// the elements of the IR that passes traverse, and to invalidate any
58 /// analyses cached on these elements as the mutations take place.
60 /// - We want to preserve the incremental and post-order traversal of the
61 /// graph even as it is refined and mutated. This means we want optimization
62 /// to observe the most refined form of the call graph and to do so in
65 /// To address this, the CGSCC manager uses both worklists that can be expanded
66 /// by passes which transform the IR, and provides invalidation tests to skip
67 /// entries that become dead. This extra data is provided to every SCC pass so
68 /// that it can carefully update the manager's traversal as the call graph
71 /// We also provide support for running function passes within the CGSCC walk,
72 /// and there we provide automatic update of the call graph including of the
73 /// pass manager to reflect call graph changes that fall out naturally as part
74 /// of scalar transformations.
76 /// The patterns used to ensure the goals of post-order visitation of the fully
79 /// 1) Sink toward the "bottom" as the graph is refined. This means that any
80 /// iteration continues in some valid post-order sequence after the mutation
81 /// has altered the structure.
83 /// 2) Enqueue in post-order, including the current entity. If the current
84 /// entity's shape changes, it and everything after it in post-order needs
85 /// to be visited to observe that shape.
87 //===----------------------------------------------------------------------===//
89 #ifndef LLVM_ANALYSIS_CGSCCPASSMANAGER_H
90 #define LLVM_ANALYSIS_CGSCCPASSMANAGER_H
92 #include "llvm/ADT/DenseSet.h"
93 #include "llvm/ADT/PriorityWorklist.h"
94 #include "llvm/ADT/STLExtras.h"
95 #include "llvm/ADT/SmallPtrSet.h"
96 #include "llvm/ADT/SmallVector.h"
97 #include "llvm/Analysis/LazyCallGraph.h"
98 #include "llvm/IR/CallSite.h"
99 #include "llvm/IR/Function.h"
100 #include "llvm/IR/InstIterator.h"
101 #include "llvm/IR/PassManager.h"
102 #include "llvm/IR/ValueHandle.h"
103 #include "llvm/Support/Debug.h"
104 #include "llvm/Support/raw_ostream.h"
111 struct CGSCCUpdateResult;
114 // Allow debug logging in this inline function.
115 #define DEBUG_TYPE "cgscc"
117 /// Extern template declaration for the analysis set for this IR unit.
118 extern template class AllAnalysesOn<LazyCallGraph::SCC>;
120 extern template class AnalysisManager<LazyCallGraph::SCC, LazyCallGraph &>;
122 /// The CGSCC analysis manager.
124 /// See the documentation for the AnalysisManager template for detail
125 /// documentation. This type serves as a convenient way to refer to this
126 /// construct in the adaptors and proxies used to integrate this into the larger
127 /// pass manager infrastructure.
128 using CGSCCAnalysisManager =
129 AnalysisManager<LazyCallGraph::SCC, LazyCallGraph &>;
131 // Explicit specialization and instantiation declarations for the pass manager.
132 // See the comments on the definition of the specialization for details on how
133 // it differs from the primary template.
136 PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager, LazyCallGraph &,
137 CGSCCUpdateResult &>::run(LazyCallGraph::SCC &InitialC,
138 CGSCCAnalysisManager &AM,
139 LazyCallGraph &G, CGSCCUpdateResult &UR);
140 extern template class PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager,
141 LazyCallGraph &, CGSCCUpdateResult &>;
143 /// The CGSCC pass manager.
145 /// See the documentation for the PassManager template for details. It runs
146 /// a sequence of SCC passes over each SCC that the manager is run over. This
147 /// type serves as a convenient way to refer to this construct.
148 using CGSCCPassManager =
149 PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager, LazyCallGraph &,
150 CGSCCUpdateResult &>;
152 /// An explicit specialization of the require analysis template pass.
153 template <typename AnalysisT>
154 struct RequireAnalysisPass<AnalysisT, LazyCallGraph::SCC, CGSCCAnalysisManager,
155 LazyCallGraph &, CGSCCUpdateResult &>
156 : PassInfoMixin<RequireAnalysisPass<AnalysisT, LazyCallGraph::SCC,
157 CGSCCAnalysisManager, LazyCallGraph &,
158 CGSCCUpdateResult &>> {
159 PreservedAnalyses run(LazyCallGraph::SCC &C, CGSCCAnalysisManager &AM,
160 LazyCallGraph &CG, CGSCCUpdateResult &) {
161 (void)AM.template getResult<AnalysisT>(C, CG);
162 return PreservedAnalyses::all();
166 /// A proxy from a \c CGSCCAnalysisManager to a \c Module.
167 using CGSCCAnalysisManagerModuleProxy =
168 InnerAnalysisManagerProxy<CGSCCAnalysisManager, Module>;
170 /// We need a specialized result for the \c CGSCCAnalysisManagerModuleProxy so
171 /// it can have access to the call graph in order to walk all the SCCs when
172 /// invalidating things.
173 template <> class CGSCCAnalysisManagerModuleProxy::Result {
175 explicit Result(CGSCCAnalysisManager &InnerAM, LazyCallGraph &G)
176 : InnerAM(&InnerAM), G(&G) {}
178 /// Accessor for the analysis manager.
179 CGSCCAnalysisManager &getManager() { return *InnerAM; }
181 /// Handler for invalidation of the Module.
183 /// If the proxy analysis itself is preserved, then we assume that the set of
184 /// SCCs in the Module hasn't changed. Thus any pointers to SCCs in the
185 /// CGSCCAnalysisManager are still valid, and we don't need to call \c clear
186 /// on the CGSCCAnalysisManager.
188 /// Regardless of whether this analysis is marked as preserved, all of the
189 /// analyses in the \c CGSCCAnalysisManager are potentially invalidated based
190 /// on the set of preserved analyses.
191 bool invalidate(Module &M, const PreservedAnalyses &PA,
192 ModuleAnalysisManager::Invalidator &Inv);
195 CGSCCAnalysisManager *InnerAM;
199 /// Provide a specialized run method for the \c CGSCCAnalysisManagerModuleProxy
200 /// so it can pass the lazy call graph to the result.
202 CGSCCAnalysisManagerModuleProxy::Result
203 CGSCCAnalysisManagerModuleProxy::run(Module &M, ModuleAnalysisManager &AM);
205 // Ensure the \c CGSCCAnalysisManagerModuleProxy is provided as an extern
207 extern template class InnerAnalysisManagerProxy<CGSCCAnalysisManager, Module>;
209 extern template class OuterAnalysisManagerProxy<
210 ModuleAnalysisManager, LazyCallGraph::SCC, LazyCallGraph &>;
212 /// A proxy from a \c ModuleAnalysisManager to an \c SCC.
213 using ModuleAnalysisManagerCGSCCProxy =
214 OuterAnalysisManagerProxy<ModuleAnalysisManager, LazyCallGraph::SCC,
217 /// Support structure for SCC passes to communicate updates the call graph back
218 /// to the CGSCC pass manager infrsatructure.
220 /// The CGSCC pass manager runs SCC passes which are allowed to update the call
221 /// graph and SCC structures. This means the structure the pass manager works
222 /// on is mutating underneath it. In order to support that, there needs to be
223 /// careful communication about the precise nature and ramifications of these
224 /// updates to the pass management infrastructure.
226 /// All SCC passes will have to accept a reference to the management layer's
227 /// update result struct and use it to reflect the results of any CG updates
230 /// Passes which do not change the call graph structure in any way can just
231 /// ignore this argument to their run method.
232 struct CGSCCUpdateResult {
233 /// Worklist of the RefSCCs queued for processing.
235 /// When a pass refines the graph and creates new RefSCCs or causes them to
236 /// have a different shape or set of component SCCs it should add the RefSCCs
237 /// to this worklist so that we visit them in the refined form.
239 /// This worklist is in reverse post-order, as we pop off the back in order
240 /// to observe RefSCCs in post-order. When adding RefSCCs, clients should add
241 /// them in reverse post-order.
242 SmallPriorityWorklist<LazyCallGraph::RefSCC *, 1> &RCWorklist;
244 /// Worklist of the SCCs queued for processing.
246 /// When a pass refines the graph and creates new SCCs or causes them to have
247 /// a different shape or set of component functions it should add the SCCs to
248 /// this worklist so that we visit them in the refined form.
250 /// Note that if the SCCs are part of a RefSCC that is added to the \c
251 /// RCWorklist, they don't need to be added here as visiting the RefSCC will
252 /// be sufficient to re-visit the SCCs within it.
254 /// This worklist is in reverse post-order, as we pop off the back in order
255 /// to observe SCCs in post-order. When adding SCCs, clients should add them
256 /// in reverse post-order.
257 SmallPriorityWorklist<LazyCallGraph::SCC *, 1> &CWorklist;
259 /// The set of invalidated RefSCCs which should be skipped if they are found
260 /// in \c RCWorklist.
262 /// This is used to quickly prune out RefSCCs when they get deleted and
263 /// happen to already be on the worklist. We use this primarily to avoid
264 /// scanning the list and removing entries from it.
265 SmallPtrSetImpl<LazyCallGraph::RefSCC *> &InvalidatedRefSCCs;
267 /// The set of invalidated SCCs which should be skipped if they are found
270 /// This is used to quickly prune out SCCs when they get deleted and happen
271 /// to already be on the worklist. We use this primarily to avoid scanning
272 /// the list and removing entries from it.
273 SmallPtrSetImpl<LazyCallGraph::SCC *> &InvalidatedSCCs;
275 /// If non-null, the updated current \c RefSCC being processed.
277 /// This is set when a graph refinement takes place an the "current" point in
278 /// the graph moves "down" or earlier in the post-order walk. This will often
279 /// cause the "current" RefSCC to be a newly created RefSCC object and the
280 /// old one to be added to the above worklist. When that happens, this
281 /// pointer is non-null and can be used to continue processing the "top" of
282 /// the post-order walk.
283 LazyCallGraph::RefSCC *UpdatedRC;
285 /// If non-null, the updated current \c SCC being processed.
287 /// This is set when a graph refinement takes place an the "current" point in
288 /// the graph moves "down" or earlier in the post-order walk. This will often
289 /// cause the "current" SCC to be a newly created SCC object and the old one
290 /// to be added to the above worklist. When that happens, this pointer is
291 /// non-null and can be used to continue processing the "top" of the
293 LazyCallGraph::SCC *UpdatedC;
295 /// A hacky area where the inliner can retain history about inlining
296 /// decisions that mutated the call graph's SCC structure in order to avoid
297 /// infinite inlining. See the comments in the inliner's CG update logic.
299 /// FIXME: Keeping this here seems like a big layering issue, we should look
300 /// for a better technique.
301 SmallDenseSet<std::pair<LazyCallGraph::Node *, LazyCallGraph::SCC *>, 4>
302 &InlinedInternalEdges;
305 /// The core module pass which does a post-order walk of the SCCs and
306 /// runs a CGSCC pass over each one.
308 /// Designed to allow composition of a CGSCCPass(Manager) and
309 /// a ModulePassManager. Note that this pass must be run with a module analysis
310 /// manager as it uses the LazyCallGraph analysis. It will also run the
311 /// \c CGSCCAnalysisManagerModuleProxy analysis prior to running the CGSCC
312 /// pass over the module to enable a \c FunctionAnalysisManager to be used
313 /// within this run safely.
314 template <typename CGSCCPassT>
315 class ModuleToPostOrderCGSCCPassAdaptor
316 : public PassInfoMixin<ModuleToPostOrderCGSCCPassAdaptor<CGSCCPassT>> {
318 explicit ModuleToPostOrderCGSCCPassAdaptor(CGSCCPassT Pass)
319 : Pass(std::move(Pass)) {}
321 // We have to explicitly define all the special member functions because MSVC
322 // refuses to generate them.
323 ModuleToPostOrderCGSCCPassAdaptor(
324 const ModuleToPostOrderCGSCCPassAdaptor &Arg)
327 ModuleToPostOrderCGSCCPassAdaptor(ModuleToPostOrderCGSCCPassAdaptor &&Arg)
328 : Pass(std::move(Arg.Pass)) {}
330 friend void swap(ModuleToPostOrderCGSCCPassAdaptor &LHS,
331 ModuleToPostOrderCGSCCPassAdaptor &RHS) {
332 std::swap(LHS.Pass, RHS.Pass);
335 ModuleToPostOrderCGSCCPassAdaptor &
336 operator=(ModuleToPostOrderCGSCCPassAdaptor RHS) {
341 /// Runs the CGSCC pass across every SCC in the module.
342 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM) {
343 // Setup the CGSCC analysis manager from its proxy.
344 CGSCCAnalysisManager &CGAM =
345 AM.getResult<CGSCCAnalysisManagerModuleProxy>(M).getManager();
347 // Get the call graph for this module.
348 LazyCallGraph &CG = AM.getResult<LazyCallGraphAnalysis>(M);
350 // We keep worklists to allow us to push more work onto the pass manager as
351 // the passes are run.
352 SmallPriorityWorklist<LazyCallGraph::RefSCC *, 1> RCWorklist;
353 SmallPriorityWorklist<LazyCallGraph::SCC *, 1> CWorklist;
355 // Keep sets for invalidated SCCs and RefSCCs that should be skipped when
356 // iterating off the worklists.
357 SmallPtrSet<LazyCallGraph::RefSCC *, 4> InvalidRefSCCSet;
358 SmallPtrSet<LazyCallGraph::SCC *, 4> InvalidSCCSet;
360 SmallDenseSet<std::pair<LazyCallGraph::Node *, LazyCallGraph::SCC *>, 4>
361 InlinedInternalEdges;
363 CGSCCUpdateResult UR = {RCWorklist, CWorklist, InvalidRefSCCSet,
364 InvalidSCCSet, nullptr, nullptr,
365 InlinedInternalEdges};
367 PreservedAnalyses PA = PreservedAnalyses::all();
369 for (auto RCI = CG.postorder_ref_scc_begin(),
370 RCE = CG.postorder_ref_scc_end();
372 assert(RCWorklist.empty() &&
373 "Should always start with an empty RefSCC worklist");
374 // The postorder_ref_sccs range we are walking is lazily constructed, so
375 // we only push the first one onto the worklist. The worklist allows us
376 // to capture *new* RefSCCs created during transformations.
378 // We really want to form RefSCCs lazily because that makes them cheaper
379 // to update as the program is simplified and allows us to have greater
380 // cache locality as forming a RefSCC touches all the parts of all the
381 // functions within that RefSCC.
383 // We also eagerly increment the iterator to the next position because
384 // the CGSCC passes below may delete the current RefSCC.
385 RCWorklist.insert(&*RCI++);
388 LazyCallGraph::RefSCC *RC = RCWorklist.pop_back_val();
389 if (InvalidRefSCCSet.count(RC)) {
390 LLVM_DEBUG(dbgs() << "Skipping an invalid RefSCC...\n");
394 assert(CWorklist.empty() &&
395 "Should always start with an empty SCC worklist");
397 LLVM_DEBUG(dbgs() << "Running an SCC pass across the RefSCC: " << *RC
400 // Push the initial SCCs in reverse post-order as we'll pop off the
401 // back and so see this in post-order.
402 for (LazyCallGraph::SCC &C : llvm::reverse(*RC))
403 CWorklist.insert(&C);
406 LazyCallGraph::SCC *C = CWorklist.pop_back_val();
407 // Due to call graph mutations, we may have invalid SCCs or SCCs from
408 // other RefSCCs in the worklist. The invalid ones are dead and the
409 // other RefSCCs should be queued above, so we just need to skip both
411 if (InvalidSCCSet.count(C)) {
412 LLVM_DEBUG(dbgs() << "Skipping an invalid SCC...\n");
415 if (&C->getOuterRefSCC() != RC) {
417 << "Skipping an SCC that is now part of some other "
423 // Check that we didn't miss any update scenario.
424 assert(!InvalidSCCSet.count(C) && "Processing an invalid SCC!");
425 assert(C->begin() != C->end() && "Cannot have an empty SCC!");
426 assert(&C->getOuterRefSCC() == RC &&
427 "Processing an SCC in a different RefSCC!");
429 UR.UpdatedRC = nullptr;
430 UR.UpdatedC = nullptr;
431 PreservedAnalyses PassPA = Pass.run(*C, CGAM, CG, UR);
433 // Update the SCC and RefSCC if necessary.
434 C = UR.UpdatedC ? UR.UpdatedC : C;
435 RC = UR.UpdatedRC ? UR.UpdatedRC : RC;
437 // If the CGSCC pass wasn't able to provide a valid updated SCC,
438 // the current SCC may simply need to be skipped if invalid.
439 if (UR.InvalidatedSCCs.count(C)) {
441 << "Skipping invalidated root or island SCC!\n");
444 // Check that we didn't miss any update scenario.
445 assert(C->begin() != C->end() && "Cannot have an empty SCC!");
447 // We handle invalidating the CGSCC analysis manager's information
448 // for the (potentially updated) SCC here. Note that any other SCCs
449 // whose structure has changed should have been invalidated by
450 // whatever was updating the call graph. This SCC gets invalidated
451 // late as it contains the nodes that were actively being
453 CGAM.invalidate(*C, PassPA);
455 // Then intersect the preserved set so that invalidation of module
456 // analyses will eventually occur when the module pass completes.
457 PA.intersect(std::move(PassPA));
459 // The pass may have restructured the call graph and refined the
460 // current SCC and/or RefSCC. We need to update our current SCC and
461 // RefSCC pointers to follow these. Also, when the current SCC is
462 // refined, re-run the SCC pass over the newly refined SCC in order
463 // to observe the most precise SCC model available. This inherently
464 // cannot cycle excessively as it only happens when we split SCCs
465 // apart, at most converging on a DAG of single nodes.
466 // FIXME: If we ever start having RefSCC passes, we'll want to
467 // iterate there too.
470 << "Re-running SCC passes after a refinement of the "
472 << *UR.UpdatedC << "\n");
474 // Note that both `C` and `RC` may at this point refer to deleted,
475 // invalid SCC and RefSCCs respectively. But we will short circuit
476 // the processing when we check them in the loop above.
477 } while (UR.UpdatedC);
478 } while (!CWorklist.empty());
480 // We only need to keep internal inlined edge information within
481 // a RefSCC, clear it to save on space and let the next time we visit
482 // any of these functions have a fresh start.
483 InlinedInternalEdges.clear();
484 } while (!RCWorklist.empty());
487 // By definition we preserve the call garph, all SCC analyses, and the
488 // analysis proxies by handling them above and in any nested pass managers.
489 PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
490 PA.preserve<LazyCallGraphAnalysis>();
491 PA.preserve<CGSCCAnalysisManagerModuleProxy>();
492 PA.preserve<FunctionAnalysisManagerModuleProxy>();
500 /// A function to deduce a function pass type and wrap it in the
501 /// templated adaptor.
502 template <typename CGSCCPassT>
503 ModuleToPostOrderCGSCCPassAdaptor<CGSCCPassT>
504 createModuleToPostOrderCGSCCPassAdaptor(CGSCCPassT Pass) {
505 return ModuleToPostOrderCGSCCPassAdaptor<CGSCCPassT>(std::move(Pass));
508 /// A proxy from a \c FunctionAnalysisManager to an \c SCC.
510 /// When a module pass runs and triggers invalidation, both the CGSCC and
511 /// Function analysis manager proxies on the module get an invalidation event.
512 /// We don't want to fully duplicate responsibility for most of the
513 /// invalidation logic. Instead, this layer is only responsible for SCC-local
514 /// invalidation events. We work with the module's FunctionAnalysisManager to
515 /// invalidate function analyses.
516 class FunctionAnalysisManagerCGSCCProxy
517 : public AnalysisInfoMixin<FunctionAnalysisManagerCGSCCProxy> {
521 explicit Result(FunctionAnalysisManager &FAM) : FAM(&FAM) {}
523 /// Accessor for the analysis manager.
524 FunctionAnalysisManager &getManager() { return *FAM; }
526 bool invalidate(LazyCallGraph::SCC &C, const PreservedAnalyses &PA,
527 CGSCCAnalysisManager::Invalidator &Inv);
530 FunctionAnalysisManager *FAM;
533 /// Computes the \c FunctionAnalysisManager and stores it in the result proxy.
534 Result run(LazyCallGraph::SCC &C, CGSCCAnalysisManager &AM, LazyCallGraph &);
537 friend AnalysisInfoMixin<FunctionAnalysisManagerCGSCCProxy>;
539 static AnalysisKey Key;
542 extern template class OuterAnalysisManagerProxy<CGSCCAnalysisManager, Function>;
544 /// A proxy from a \c CGSCCAnalysisManager to a \c Function.
545 using CGSCCAnalysisManagerFunctionProxy =
546 OuterAnalysisManagerProxy<CGSCCAnalysisManager, Function>;
548 /// Helper to update the call graph after running a function pass.
550 /// Function passes can only mutate the call graph in specific ways. This
551 /// routine provides a helper that updates the call graph in those ways
552 /// including returning whether any changes were made and populating a CG
553 /// update result struct for the overall CGSCC walk.
554 LazyCallGraph::SCC &updateCGAndAnalysisManagerForFunctionPass(
555 LazyCallGraph &G, LazyCallGraph::SCC &C, LazyCallGraph::Node &N,
556 CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR);
558 /// Adaptor that maps from a SCC to its functions.
560 /// Designed to allow composition of a FunctionPass(Manager) and
561 /// a CGSCCPassManager. Note that if this pass is constructed with a pointer
562 /// to a \c CGSCCAnalysisManager it will run the
563 /// \c FunctionAnalysisManagerCGSCCProxy analysis prior to running the function
564 /// pass over the SCC to enable a \c FunctionAnalysisManager to be used
565 /// within this run safely.
566 template <typename FunctionPassT>
567 class CGSCCToFunctionPassAdaptor
568 : public PassInfoMixin<CGSCCToFunctionPassAdaptor<FunctionPassT>> {
570 explicit CGSCCToFunctionPassAdaptor(FunctionPassT Pass)
571 : Pass(std::move(Pass)) {}
573 // We have to explicitly define all the special member functions because MSVC
574 // refuses to generate them.
575 CGSCCToFunctionPassAdaptor(const CGSCCToFunctionPassAdaptor &Arg)
578 CGSCCToFunctionPassAdaptor(CGSCCToFunctionPassAdaptor &&Arg)
579 : Pass(std::move(Arg.Pass)) {}
581 friend void swap(CGSCCToFunctionPassAdaptor &LHS,
582 CGSCCToFunctionPassAdaptor &RHS) {
583 std::swap(LHS.Pass, RHS.Pass);
586 CGSCCToFunctionPassAdaptor &operator=(CGSCCToFunctionPassAdaptor RHS) {
591 /// Runs the function pass across every function in the module.
592 PreservedAnalyses run(LazyCallGraph::SCC &C, CGSCCAnalysisManager &AM,
593 LazyCallGraph &CG, CGSCCUpdateResult &UR) {
594 // Setup the function analysis manager from its proxy.
595 FunctionAnalysisManager &FAM =
596 AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, CG).getManager();
598 SmallVector<LazyCallGraph::Node *, 4> Nodes;
599 for (LazyCallGraph::Node &N : C)
602 // The SCC may get split while we are optimizing functions due to deleting
603 // edges. If this happens, the current SCC can shift, so keep track of
604 // a pointer we can overwrite.
605 LazyCallGraph::SCC *CurrentC = &C;
607 LLVM_DEBUG(dbgs() << "Running function passes across an SCC: " << C
610 PreservedAnalyses PA = PreservedAnalyses::all();
611 for (LazyCallGraph::Node *N : Nodes) {
612 // Skip nodes from other SCCs. These may have been split out during
613 // processing. We'll eventually visit those SCCs and pick up the nodes
615 if (CG.lookupSCC(*N) != CurrentC)
618 PreservedAnalyses PassPA = Pass.run(N->getFunction(), FAM);
620 // We know that the function pass couldn't have invalidated any other
621 // function's analyses (that's the contract of a function pass), so
622 // directly handle the function analysis manager's invalidation here.
623 FAM.invalidate(N->getFunction(), PassPA);
625 // Then intersect the preserved set so that invalidation of module
626 // analyses will eventually occur when the module pass completes.
627 PA.intersect(std::move(PassPA));
629 // If the call graph hasn't been preserved, update it based on this
630 // function pass. This may also update the current SCC to point to
631 // a smaller, more refined SCC.
632 auto PAC = PA.getChecker<LazyCallGraphAnalysis>();
633 if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<Module>>()) {
634 CurrentC = &updateCGAndAnalysisManagerForFunctionPass(CG, *CurrentC, *N,
637 CG.lookupSCC(*N) == CurrentC &&
638 "Current SCC not updated to the SCC containing the current node!");
642 // By definition we preserve the proxy. And we preserve all analyses on
643 // Functions. This precludes *any* invalidation of function analyses by the
644 // proxy, but that's OK because we've taken care to invalidate analyses in
645 // the function analysis manager incrementally above.
646 PA.preserveSet<AllAnalysesOn<Function>>();
647 PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
649 // We've also ensured that we updated the call graph along the way.
650 PA.preserve<LazyCallGraphAnalysis>();
659 /// A function to deduce a function pass type and wrap it in the
660 /// templated adaptor.
661 template <typename FunctionPassT>
662 CGSCCToFunctionPassAdaptor<FunctionPassT>
663 createCGSCCToFunctionPassAdaptor(FunctionPassT Pass) {
664 return CGSCCToFunctionPassAdaptor<FunctionPassT>(std::move(Pass));
667 /// A helper that repeats an SCC pass each time an indirect call is refined to
668 /// a direct call by that pass.
670 /// While the CGSCC pass manager works to re-visit SCCs and RefSCCs as they
671 /// change shape, we may also want to repeat an SCC pass if it simply refines
672 /// an indirect call to a direct call, even if doing so does not alter the
673 /// shape of the graph. Note that this only pertains to direct calls to
674 /// functions where IPO across the SCC may be able to compute more precise
675 /// results. For intrinsics, we assume scalar optimizations already can fully
676 /// reason about them.
678 /// This repetition has the potential to be very large however, as each one
679 /// might refine a single call site. As a consequence, in practice we use an
680 /// upper bound on the number of repetitions to limit things.
681 template <typename PassT>
682 class DevirtSCCRepeatedPass
683 : public PassInfoMixin<DevirtSCCRepeatedPass<PassT>> {
685 explicit DevirtSCCRepeatedPass(PassT Pass, int MaxIterations)
686 : Pass(std::move(Pass)), MaxIterations(MaxIterations) {}
688 /// Runs the wrapped pass up to \c MaxIterations on the SCC, iterating
689 /// whenever an indirect call is refined.
690 PreservedAnalyses run(LazyCallGraph::SCC &InitialC, CGSCCAnalysisManager &AM,
691 LazyCallGraph &CG, CGSCCUpdateResult &UR) {
692 PreservedAnalyses PA = PreservedAnalyses::all();
694 // The SCC may be refined while we are running passes over it, so set up
695 // a pointer that we can update.
696 LazyCallGraph::SCC *C = &InitialC;
698 // Collect value handles for all of the indirect call sites.
699 SmallVector<WeakTrackingVH, 8> CallHandles;
701 // Struct to track the counts of direct and indirect calls in each function
708 // Put value handles on all of the indirect calls and return the number of
709 // direct calls for each function in the SCC.
710 auto ScanSCC = [](LazyCallGraph::SCC &C,
711 SmallVectorImpl<WeakTrackingVH> &CallHandles) {
712 assert(CallHandles.empty() && "Must start with a clear set of handles.");
714 SmallVector<CallCount, 4> CallCounts;
715 for (LazyCallGraph::Node &N : C) {
716 CallCounts.push_back({0, 0});
717 CallCount &Count = CallCounts.back();
718 for (Instruction &I : instructions(N.getFunction()))
719 if (auto CS = CallSite(&I)) {
720 if (CS.getCalledFunction()) {
724 CallHandles.push_back(WeakTrackingVH(&I));
732 // Populate the initial call handles and get the initial call counts.
733 auto CallCounts = ScanSCC(*C, CallHandles);
735 for (int Iteration = 0;; ++Iteration) {
736 PreservedAnalyses PassPA = Pass.run(*C, AM, CG, UR);
738 // If the SCC structure has changed, bail immediately and let the outer
739 // CGSCC layer handle any iteration to reflect the refined structure.
740 if (UR.UpdatedC && UR.UpdatedC != C) {
741 PA.intersect(std::move(PassPA));
745 // Check that we didn't miss any update scenario.
746 assert(!UR.InvalidatedSCCs.count(C) && "Processing an invalid SCC!");
747 assert(C->begin() != C->end() && "Cannot have an empty SCC!");
748 assert((int)CallCounts.size() == C->size() &&
749 "Cannot have changed the size of the SCC!");
751 // Check whether any of the handles were devirtualized.
752 auto IsDevirtualizedHandle = [&](WeakTrackingVH &CallH) {
755 auto CS = CallSite(CallH);
759 // If the call is still indirect, leave it alone.
760 Function *F = CS.getCalledFunction();
764 LLVM_DEBUG(dbgs() << "Found devirutalized call from "
765 << CS.getParent()->getParent()->getName() << " to "
766 << F->getName() << "\n");
768 // We now have a direct call where previously we had an indirect call,
769 // so iterate to process this devirtualization site.
772 bool Devirt = llvm::any_of(CallHandles, IsDevirtualizedHandle);
774 // Rescan to build up a new set of handles and count how many direct
775 // calls remain. If we decide to iterate, this also sets up the input to
776 // the next iteration.
778 auto NewCallCounts = ScanSCC(*C, CallHandles);
780 // If we haven't found an explicit devirtualization already see if we
781 // have decreased the number of indirect calls and increased the number
782 // of direct calls for any function in the SCC. This can be fooled by all
783 // manner of transformations such as DCE and other things, but seems to
784 // work well in practice.
786 for (int i = 0, Size = C->size(); i < Size; ++i)
787 if (CallCounts[i].Indirect > NewCallCounts[i].Indirect &&
788 CallCounts[i].Direct < NewCallCounts[i].Direct) {
794 PA.intersect(std::move(PassPA));
798 // Otherwise, if we've already hit our max, we're done.
799 if (Iteration >= MaxIterations) {
801 dbgs() << "Found another devirtualization after hitting the max "
802 "number of repetitions ("
803 << MaxIterations << ") on SCC: " << *C << "\n");
804 PA.intersect(std::move(PassPA));
810 << "Repeating an SCC pass after finding a devirtualization in: " << *C
813 // Move over the new call counts in preparation for iterating.
814 CallCounts = std::move(NewCallCounts);
816 // Update the analysis manager with each run and intersect the total set
817 // of preserved analyses so we're ready to iterate.
818 AM.invalidate(*C, PassPA);
819 PA.intersect(std::move(PassPA));
822 // Note that we don't add any preserved entries here unlike a more normal
823 // "pass manager" because we only handle invalidation *between* iterations,
824 // not after the last iteration.
833 /// A function to deduce a function pass type and wrap it in the
834 /// templated adaptor.
835 template <typename PassT>
836 DevirtSCCRepeatedPass<PassT> createDevirtSCCRepeatedPass(PassT Pass,
838 return DevirtSCCRepeatedPass<PassT>(std::move(Pass), MaxIterations);
841 // Clear out the debug logging macro.
844 } // end namespace llvm
846 #endif // LLVM_ANALYSIS_CGSCCPASSMANAGER_H