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/Optional.h"
12 #include "llvm/ADT/STLExtras.h"
13 #include "llvm/ADT/SetVector.h"
14 #include "llvm/ADT/SmallPtrSet.h"
15 #include "llvm/ADT/SmallVector.h"
16 #include "llvm/ADT/iterator_range.h"
17 #include "llvm/Analysis/LazyCallGraph.h"
18 #include "llvm/IR/Constant.h"
19 #include "llvm/IR/InstIterator.h"
20 #include "llvm/IR/Instruction.h"
21 #include "llvm/IR/PassManager.h"
22 #include "llvm/IR/PassManagerImpl.h"
23 #include "llvm/IR/ValueHandle.h"
24 #include "llvm/Support/Casting.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/TimeProfiler.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include <algorithm>
31 #include <cassert>
32 #include <iterator>
33
34 #define DEBUG_TYPE "cgscc"
35
36 using namespace llvm;
37
38 // Explicit template instantiations and specialization definitions for core
39 // template typedefs.
40 namespace llvm {
41
42 static cl::opt<bool> AbortOnMaxDevirtIterationsReached(
43 "abort-on-max-devirt-iterations-reached",
44 cl::desc("Abort when the max iterations for devirtualization CGSCC repeat "
45 "pass is reached"));
46
47 // Explicit instantiations for the core proxy templates.
48 template class AllAnalysesOn<LazyCallGraph::SCC>;
49 template class AnalysisManager<LazyCallGraph::SCC, LazyCallGraph &>;
50 template class PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager,
51 LazyCallGraph &, CGSCCUpdateResult &>;
52 template class InnerAnalysisManagerProxy<CGSCCAnalysisManager, Module>;
53 template class OuterAnalysisManagerProxy<ModuleAnalysisManager,
54 LazyCallGraph::SCC, LazyCallGraph &>;
55 template class OuterAnalysisManagerProxy<CGSCCAnalysisManager, Function>;
56
57 /// Explicitly specialize the pass manager run method to handle call graph
58 /// updates.
59 template <>
60 PreservedAnalyses
61 PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager, LazyCallGraph &,
run(LazyCallGraph::SCC & InitialC,CGSCCAnalysisManager & AM,LazyCallGraph & G,CGSCCUpdateResult & UR)62 CGSCCUpdateResult &>::run(LazyCallGraph::SCC &InitialC,
63 CGSCCAnalysisManager &AM,
64 LazyCallGraph &G, CGSCCUpdateResult &UR) {
65 // Request PassInstrumentation from analysis manager, will use it to run
66 // instrumenting callbacks for the passes later.
67 PassInstrumentation PI =
68 AM.getResult<PassInstrumentationAnalysis>(InitialC, G);
69
70 PreservedAnalyses PA = PreservedAnalyses::all();
71
72 // The SCC may be refined while we are running passes over it, so set up
73 // a pointer that we can update.
74 LazyCallGraph::SCC *C = &InitialC;
75
76 // Get Function analysis manager from its proxy.
77 FunctionAnalysisManager &FAM =
78 AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(*C)->getManager();
79
80 for (auto &Pass : Passes) {
81 // Check the PassInstrumentation's BeforePass callbacks before running the
82 // pass, skip its execution completely if asked to (callback returns false).
83 if (!PI.runBeforePass(*Pass, *C))
84 continue;
85
86 PreservedAnalyses PassPA;
87 {
88 TimeTraceScope TimeScope(Pass->name());
89 PassPA = Pass->run(*C, AM, G, UR);
90 }
91
92 if (UR.InvalidatedSCCs.count(C))
93 PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
94 else
95 PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
96
97 // Update the SCC if necessary.
98 C = UR.UpdatedC ? UR.UpdatedC : C;
99 if (UR.UpdatedC) {
100 // If C is updated, also create a proxy and update FAM inside the result.
101 auto *ResultFAMCP =
102 &AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, G);
103 ResultFAMCP->updateFAM(FAM);
104 }
105
106 // If the CGSCC pass wasn't able to provide a valid updated SCC, the
107 // current SCC may simply need to be skipped if invalid.
108 if (UR.InvalidatedSCCs.count(C)) {
109 LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
110 break;
111 }
112 // Check that we didn't miss any update scenario.
113 assert(C->begin() != C->end() && "Cannot have an empty SCC!");
114
115 // Update the analysis manager as each pass runs and potentially
116 // invalidates analyses.
117 AM.invalidate(*C, PassPA);
118
119 // Finally, we intersect the final preserved analyses to compute the
120 // aggregate preserved set for this pass manager.
121 PA.intersect(std::move(PassPA));
122
123 // FIXME: Historically, the pass managers all called the LLVM context's
124 // yield function here. We don't have a generic way to acquire the
125 // context and it isn't yet clear what the right pattern is for yielding
126 // in the new pass manager so it is currently omitted.
127 // ...getContext().yield();
128 }
129
130 // Before we mark all of *this* SCC's analyses as preserved below, intersect
131 // this with the cross-SCC preserved analysis set. This is used to allow
132 // CGSCC passes to mutate ancestor SCCs and still trigger proper invalidation
133 // for them.
134 UR.CrossSCCPA.intersect(PA);
135
136 // Invalidation was handled after each pass in the above loop for the current
137 // SCC. Therefore, the remaining analysis results in the AnalysisManager are
138 // preserved. We mark this with a set so that we don't need to inspect each
139 // one individually.
140 PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
141
142 return PA;
143 }
144
145 PreservedAnalyses
run(Module & M,ModuleAnalysisManager & AM)146 ModuleToPostOrderCGSCCPassAdaptor::run(Module &M, ModuleAnalysisManager &AM) {
147 // Setup the CGSCC analysis manager from its proxy.
148 CGSCCAnalysisManager &CGAM =
149 AM.getResult<CGSCCAnalysisManagerModuleProxy>(M).getManager();
150
151 // Get the call graph for this module.
152 LazyCallGraph &CG = AM.getResult<LazyCallGraphAnalysis>(M);
153
154 // Get Function analysis manager from its proxy.
155 FunctionAnalysisManager &FAM =
156 AM.getCachedResult<FunctionAnalysisManagerModuleProxy>(M)->getManager();
157
158 // We keep worklists to allow us to push more work onto the pass manager as
159 // the passes are run.
160 SmallPriorityWorklist<LazyCallGraph::RefSCC *, 1> RCWorklist;
161 SmallPriorityWorklist<LazyCallGraph::SCC *, 1> CWorklist;
162
163 // Keep sets for invalidated SCCs and RefSCCs that should be skipped when
164 // iterating off the worklists.
165 SmallPtrSet<LazyCallGraph::RefSCC *, 4> InvalidRefSCCSet;
166 SmallPtrSet<LazyCallGraph::SCC *, 4> InvalidSCCSet;
167
168 SmallDenseSet<std::pair<LazyCallGraph::Node *, LazyCallGraph::SCC *>, 4>
169 InlinedInternalEdges;
170
171 CGSCCUpdateResult UR = {
172 RCWorklist, CWorklist, InvalidRefSCCSet, InvalidSCCSet,
173 nullptr, nullptr, PreservedAnalyses::all(), InlinedInternalEdges,
174 {}};
175
176 // Request PassInstrumentation from analysis manager, will use it to run
177 // instrumenting callbacks for the passes later.
178 PassInstrumentation PI = AM.getResult<PassInstrumentationAnalysis>(M);
179
180 PreservedAnalyses PA = PreservedAnalyses::all();
181 CG.buildRefSCCs();
182 for (auto RCI = CG.postorder_ref_scc_begin(),
183 RCE = CG.postorder_ref_scc_end();
184 RCI != RCE;) {
185 assert(RCWorklist.empty() &&
186 "Should always start with an empty RefSCC worklist");
187 // The postorder_ref_sccs range we are walking is lazily constructed, so
188 // we only push the first one onto the worklist. The worklist allows us
189 // to capture *new* RefSCCs created during transformations.
190 //
191 // We really want to form RefSCCs lazily because that makes them cheaper
192 // to update as the program is simplified and allows us to have greater
193 // cache locality as forming a RefSCC touches all the parts of all the
194 // functions within that RefSCC.
195 //
196 // We also eagerly increment the iterator to the next position because
197 // the CGSCC passes below may delete the current RefSCC.
198 RCWorklist.insert(&*RCI++);
199
200 do {
201 LazyCallGraph::RefSCC *RC = RCWorklist.pop_back_val();
202 if (InvalidRefSCCSet.count(RC)) {
203 LLVM_DEBUG(dbgs() << "Skipping an invalid RefSCC...\n");
204 continue;
205 }
206
207 assert(CWorklist.empty() &&
208 "Should always start with an empty SCC worklist");
209
210 LLVM_DEBUG(dbgs() << "Running an SCC pass across the RefSCC: " << *RC
211 << "\n");
212
213 // The top of the worklist may *also* be the same SCC we just ran over
214 // (and invalidated for). Keep track of that last SCC we processed due
215 // to SCC update to avoid redundant processing when an SCC is both just
216 // updated itself and at the top of the worklist.
217 LazyCallGraph::SCC *LastUpdatedC = nullptr;
218
219 // Push the initial SCCs in reverse post-order as we'll pop off the
220 // back and so see this in post-order.
221 for (LazyCallGraph::SCC &C : llvm::reverse(*RC))
222 CWorklist.insert(&C);
223
224 do {
225 LazyCallGraph::SCC *C = CWorklist.pop_back_val();
226 // Due to call graph mutations, we may have invalid SCCs or SCCs from
227 // other RefSCCs in the worklist. The invalid ones are dead and the
228 // other RefSCCs should be queued above, so we just need to skip both
229 // scenarios here.
230 if (InvalidSCCSet.count(C)) {
231 LLVM_DEBUG(dbgs() << "Skipping an invalid SCC...\n");
232 continue;
233 }
234 if (LastUpdatedC == C) {
235 LLVM_DEBUG(dbgs() << "Skipping redundant run on SCC: " << *C << "\n");
236 continue;
237 }
238 if (&C->getOuterRefSCC() != RC) {
239 LLVM_DEBUG(dbgs() << "Skipping an SCC that is now part of some other "
240 "RefSCC...\n");
241 continue;
242 }
243
244 // Ensure we can proxy analysis updates from the CGSCC analysis manager
245 // into the the Function analysis manager by getting a proxy here.
246 // This also needs to update the FunctionAnalysisManager, as this may be
247 // the first time we see this SCC.
248 CGAM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, CG).updateFAM(
249 FAM);
250
251 // Each time we visit a new SCC pulled off the worklist,
252 // a transformation of a child SCC may have also modified this parent
253 // and invalidated analyses. So we invalidate using the update record's
254 // cross-SCC preserved set. This preserved set is intersected by any
255 // CGSCC pass that handles invalidation (primarily pass managers) prior
256 // to marking its SCC as preserved. That lets us track everything that
257 // might need invalidation across SCCs without excessive invalidations
258 // on a single SCC.
259 //
260 // This essentially allows SCC passes to freely invalidate analyses
261 // of any ancestor SCC. If this becomes detrimental to successfully
262 // caching analyses, we could force each SCC pass to manually
263 // invalidate the analyses for any SCCs other than themselves which
264 // are mutated. However, that seems to lose the robustness of the
265 // pass-manager driven invalidation scheme.
266 CGAM.invalidate(*C, UR.CrossSCCPA);
267
268 do {
269 // Check that we didn't miss any update scenario.
270 assert(!InvalidSCCSet.count(C) && "Processing an invalid SCC!");
271 assert(C->begin() != C->end() && "Cannot have an empty SCC!");
272 assert(&C->getOuterRefSCC() == RC &&
273 "Processing an SCC in a different RefSCC!");
274
275 LastUpdatedC = UR.UpdatedC;
276 UR.UpdatedRC = nullptr;
277 UR.UpdatedC = nullptr;
278
279 // Check the PassInstrumentation's BeforePass callbacks before
280 // running the pass, skip its execution completely if asked to
281 // (callback returns false).
282 if (!PI.runBeforePass<LazyCallGraph::SCC>(*Pass, *C))
283 continue;
284
285 PreservedAnalyses PassPA;
286 {
287 TimeTraceScope TimeScope(Pass->name());
288 PassPA = Pass->run(*C, CGAM, CG, UR);
289 }
290
291 if (UR.InvalidatedSCCs.count(C))
292 PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
293 else
294 PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
295
296 // Update the SCC and RefSCC if necessary.
297 C = UR.UpdatedC ? UR.UpdatedC : C;
298 RC = UR.UpdatedRC ? UR.UpdatedRC : RC;
299
300 if (UR.UpdatedC) {
301 // If we're updating the SCC, also update the FAM inside the proxy's
302 // result.
303 CGAM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, CG).updateFAM(
304 FAM);
305 }
306
307 // If the CGSCC pass wasn't able to provide a valid updated SCC,
308 // the current SCC may simply need to be skipped if invalid.
309 if (UR.InvalidatedSCCs.count(C)) {
310 LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
311 break;
312 }
313 // Check that we didn't miss any update scenario.
314 assert(C->begin() != C->end() && "Cannot have an empty SCC!");
315
316 // We handle invalidating the CGSCC analysis manager's information
317 // for the (potentially updated) SCC here. Note that any other SCCs
318 // whose structure has changed should have been invalidated by
319 // whatever was updating the call graph. This SCC gets invalidated
320 // late as it contains the nodes that were actively being
321 // processed.
322 CGAM.invalidate(*C, PassPA);
323
324 // Then intersect the preserved set so that invalidation of module
325 // analyses will eventually occur when the module pass completes.
326 // Also intersect with the cross-SCC preserved set to capture any
327 // cross-SCC invalidation.
328 UR.CrossSCCPA.intersect(PassPA);
329 PA.intersect(std::move(PassPA));
330
331 // The pass may have restructured the call graph and refined the
332 // current SCC and/or RefSCC. We need to update our current SCC and
333 // RefSCC pointers to follow these. Also, when the current SCC is
334 // refined, re-run the SCC pass over the newly refined SCC in order
335 // to observe the most precise SCC model available. This inherently
336 // cannot cycle excessively as it only happens when we split SCCs
337 // apart, at most converging on a DAG of single nodes.
338 // FIXME: If we ever start having RefSCC passes, we'll want to
339 // iterate there too.
340 if (UR.UpdatedC)
341 LLVM_DEBUG(dbgs()
342 << "Re-running SCC passes after a refinement of the "
343 "current SCC: "
344 << *UR.UpdatedC << "\n");
345
346 // Note that both `C` and `RC` may at this point refer to deleted,
347 // invalid SCC and RefSCCs respectively. But we will short circuit
348 // the processing when we check them in the loop above.
349 } while (UR.UpdatedC);
350 } while (!CWorklist.empty());
351
352 // We only need to keep internal inlined edge information within
353 // a RefSCC, clear it to save on space and let the next time we visit
354 // any of these functions have a fresh start.
355 InlinedInternalEdges.clear();
356 } while (!RCWorklist.empty());
357 }
358
359 // By definition we preserve the call garph, all SCC analyses, and the
360 // analysis proxies by handling them above and in any nested pass managers.
361 PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
362 PA.preserve<LazyCallGraphAnalysis>();
363 PA.preserve<CGSCCAnalysisManagerModuleProxy>();
364 PA.preserve<FunctionAnalysisManagerModuleProxy>();
365 return PA;
366 }
367
run(LazyCallGraph::SCC & InitialC,CGSCCAnalysisManager & AM,LazyCallGraph & CG,CGSCCUpdateResult & UR)368 PreservedAnalyses DevirtSCCRepeatedPass::run(LazyCallGraph::SCC &InitialC,
369 CGSCCAnalysisManager &AM,
370 LazyCallGraph &CG,
371 CGSCCUpdateResult &UR) {
372 PreservedAnalyses PA = PreservedAnalyses::all();
373 PassInstrumentation PI =
374 AM.getResult<PassInstrumentationAnalysis>(InitialC, CG);
375
376 // The SCC may be refined while we are running passes over it, so set up
377 // a pointer that we can update.
378 LazyCallGraph::SCC *C = &InitialC;
379
380 // Struct to track the counts of direct and indirect calls in each function
381 // of the SCC.
382 struct CallCount {
383 int Direct;
384 int Indirect;
385 };
386
387 // Put value handles on all of the indirect calls and return the number of
388 // direct calls for each function in the SCC.
389 auto ScanSCC = [](LazyCallGraph::SCC &C,
390 SmallMapVector<Value *, WeakTrackingVH, 16> &CallHandles) {
391 assert(CallHandles.empty() && "Must start with a clear set of handles.");
392
393 SmallDenseMap<Function *, CallCount> CallCounts;
394 CallCount CountLocal = {0, 0};
395 for (LazyCallGraph::Node &N : C) {
396 CallCount &Count =
397 CallCounts.insert(std::make_pair(&N.getFunction(), CountLocal))
398 .first->second;
399 for (Instruction &I : instructions(N.getFunction()))
400 if (auto *CB = dyn_cast<CallBase>(&I)) {
401 if (CB->getCalledFunction()) {
402 ++Count.Direct;
403 } else {
404 ++Count.Indirect;
405 CallHandles.insert({CB, WeakTrackingVH(CB)});
406 }
407 }
408 }
409
410 return CallCounts;
411 };
412
413 UR.IndirectVHs.clear();
414 // Populate the initial call handles and get the initial call counts.
415 auto CallCounts = ScanSCC(*C, UR.IndirectVHs);
416
417 for (int Iteration = 0;; ++Iteration) {
418 if (!PI.runBeforePass<LazyCallGraph::SCC>(*Pass, *C))
419 continue;
420
421 PreservedAnalyses PassPA = Pass->run(*C, AM, CG, UR);
422
423 if (UR.InvalidatedSCCs.count(C))
424 PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
425 else
426 PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
427
428 // If the SCC structure has changed, bail immediately and let the outer
429 // CGSCC layer handle any iteration to reflect the refined structure.
430 if (UR.UpdatedC && UR.UpdatedC != C) {
431 PA.intersect(std::move(PassPA));
432 break;
433 }
434
435 // Check that we didn't miss any update scenario.
436 assert(!UR.InvalidatedSCCs.count(C) && "Processing an invalid SCC!");
437 assert(C->begin() != C->end() && "Cannot have an empty SCC!");
438
439 // Check whether any of the handles were devirtualized.
440 bool Devirt = llvm::any_of(UR.IndirectVHs, [](auto &P) -> bool {
441 if (P.second) {
442 if (CallBase *CB = dyn_cast<CallBase>(P.second)) {
443 if (CB->getCalledFunction()) {
444 LLVM_DEBUG(dbgs() << "Found devirtualized call: " << *CB << "\n");
445 return true;
446 }
447 }
448 }
449 return false;
450 });
451
452 // Rescan to build up a new set of handles and count how many direct
453 // calls remain. If we decide to iterate, this also sets up the input to
454 // the next iteration.
455 UR.IndirectVHs.clear();
456 auto NewCallCounts = ScanSCC(*C, UR.IndirectVHs);
457
458 // If we haven't found an explicit devirtualization already see if we
459 // have decreased the number of indirect calls and increased the number
460 // of direct calls for any function in the SCC. This can be fooled by all
461 // manner of transformations such as DCE and other things, but seems to
462 // work well in practice.
463 if (!Devirt)
464 // Iterate over the keys in NewCallCounts, if Function also exists in
465 // CallCounts, make the check below.
466 for (auto &Pair : NewCallCounts) {
467 auto &CallCountNew = Pair.second;
468 auto CountIt = CallCounts.find(Pair.first);
469 if (CountIt != CallCounts.end()) {
470 const auto &CallCountOld = CountIt->second;
471 if (CallCountOld.Indirect > CallCountNew.Indirect &&
472 CallCountOld.Direct < CallCountNew.Direct) {
473 Devirt = true;
474 break;
475 }
476 }
477 }
478
479 if (!Devirt) {
480 PA.intersect(std::move(PassPA));
481 break;
482 }
483
484 // Otherwise, if we've already hit our max, we're done.
485 if (Iteration >= MaxIterations) {
486 if (AbortOnMaxDevirtIterationsReached)
487 report_fatal_error("Max devirtualization iterations reached");
488 LLVM_DEBUG(
489 dbgs() << "Found another devirtualization after hitting the max "
490 "number of repetitions ("
491 << MaxIterations << ") on SCC: " << *C << "\n");
492 PA.intersect(std::move(PassPA));
493 break;
494 }
495
496 LLVM_DEBUG(
497 dbgs() << "Repeating an SCC pass after finding a devirtualization in: "
498 << *C << "\n");
499
500 // Move over the new call counts in preparation for iterating.
501 CallCounts = std::move(NewCallCounts);
502
503 // Update the analysis manager with each run and intersect the total set
504 // of preserved analyses so we're ready to iterate.
505 AM.invalidate(*C, PassPA);
506
507 PA.intersect(std::move(PassPA));
508 }
509
510 // Note that we don't add any preserved entries here unlike a more normal
511 // "pass manager" because we only handle invalidation *between* iterations,
512 // not after the last iteration.
513 return PA;
514 }
515
run(LazyCallGraph::SCC & C,CGSCCAnalysisManager & AM,LazyCallGraph & CG,CGSCCUpdateResult & UR)516 PreservedAnalyses CGSCCToFunctionPassAdaptor::run(LazyCallGraph::SCC &C,
517 CGSCCAnalysisManager &AM,
518 LazyCallGraph &CG,
519 CGSCCUpdateResult &UR) {
520 // Setup the function analysis manager from its proxy.
521 FunctionAnalysisManager &FAM =
522 AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, CG).getManager();
523
524 SmallVector<LazyCallGraph::Node *, 4> Nodes;
525 for (LazyCallGraph::Node &N : C)
526 Nodes.push_back(&N);
527
528 // The SCC may get split while we are optimizing functions due to deleting
529 // edges. If this happens, the current SCC can shift, so keep track of
530 // a pointer we can overwrite.
531 LazyCallGraph::SCC *CurrentC = &C;
532
533 LLVM_DEBUG(dbgs() << "Running function passes across an SCC: " << C << "\n");
534
535 PreservedAnalyses PA = PreservedAnalyses::all();
536 for (LazyCallGraph::Node *N : Nodes) {
537 // Skip nodes from other SCCs. These may have been split out during
538 // processing. We'll eventually visit those SCCs and pick up the nodes
539 // there.
540 if (CG.lookupSCC(*N) != CurrentC)
541 continue;
542
543 Function &F = N->getFunction();
544
545 PassInstrumentation PI = FAM.getResult<PassInstrumentationAnalysis>(F);
546 if (!PI.runBeforePass<Function>(*Pass, F))
547 continue;
548
549 PreservedAnalyses PassPA;
550 {
551 TimeTraceScope TimeScope(Pass->name());
552 PassPA = Pass->run(F, FAM);
553 }
554
555 PI.runAfterPass<Function>(*Pass, F, PassPA);
556
557 // We know that the function pass couldn't have invalidated any other
558 // function's analyses (that's the contract of a function pass), so
559 // directly handle the function analysis manager's invalidation here.
560 FAM.invalidate(F, PassPA);
561
562 // Then intersect the preserved set so that invalidation of module
563 // analyses will eventually occur when the module pass completes.
564 PA.intersect(std::move(PassPA));
565
566 // If the call graph hasn't been preserved, update it based on this
567 // function pass. This may also update the current SCC to point to
568 // a smaller, more refined SCC.
569 auto PAC = PA.getChecker<LazyCallGraphAnalysis>();
570 if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<Module>>()) {
571 CurrentC = &updateCGAndAnalysisManagerForFunctionPass(CG, *CurrentC, *N,
572 AM, UR, FAM);
573 assert(CG.lookupSCC(*N) == CurrentC &&
574 "Current SCC not updated to the SCC containing the current node!");
575 }
576 }
577
578 // By definition we preserve the proxy. And we preserve all analyses on
579 // Functions. This precludes *any* invalidation of function analyses by the
580 // proxy, but that's OK because we've taken care to invalidate analyses in
581 // the function analysis manager incrementally above.
582 PA.preserveSet<AllAnalysesOn<Function>>();
583 PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
584
585 // We've also ensured that we updated the call graph along the way.
586 PA.preserve<LazyCallGraphAnalysis>();
587
588 return PA;
589 }
590
invalidate(Module & M,const PreservedAnalyses & PA,ModuleAnalysisManager::Invalidator & Inv)591 bool CGSCCAnalysisManagerModuleProxy::Result::invalidate(
592 Module &M, const PreservedAnalyses &PA,
593 ModuleAnalysisManager::Invalidator &Inv) {
594 // If literally everything is preserved, we're done.
595 if (PA.areAllPreserved())
596 return false; // This is still a valid proxy.
597
598 // If this proxy or the call graph is going to be invalidated, we also need
599 // to clear all the keys coming from that analysis.
600 //
601 // We also directly invalidate the FAM's module proxy if necessary, and if
602 // that proxy isn't preserved we can't preserve this proxy either. We rely on
603 // it to handle module -> function analysis invalidation in the face of
604 // structural changes and so if it's unavailable we conservatively clear the
605 // entire SCC layer as well rather than trying to do invalidation ourselves.
606 auto PAC = PA.getChecker<CGSCCAnalysisManagerModuleProxy>();
607 if (!(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Module>>()) ||
608 Inv.invalidate<LazyCallGraphAnalysis>(M, PA) ||
609 Inv.invalidate<FunctionAnalysisManagerModuleProxy>(M, PA)) {
610 InnerAM->clear();
611
612 // And the proxy itself should be marked as invalid so that we can observe
613 // the new call graph. This isn't strictly necessary because we cheat
614 // above, but is still useful.
615 return true;
616 }
617
618 // Directly check if the relevant set is preserved so we can short circuit
619 // invalidating SCCs below.
620 bool AreSCCAnalysesPreserved =
621 PA.allAnalysesInSetPreserved<AllAnalysesOn<LazyCallGraph::SCC>>();
622
623 // Ok, we have a graph, so we can propagate the invalidation down into it.
624 G->buildRefSCCs();
625 for (auto &RC : G->postorder_ref_sccs())
626 for (auto &C : RC) {
627 Optional<PreservedAnalyses> InnerPA;
628
629 // Check to see whether the preserved set needs to be adjusted based on
630 // module-level analysis invalidation triggering deferred invalidation
631 // for this SCC.
632 if (auto *OuterProxy =
633 InnerAM->getCachedResult<ModuleAnalysisManagerCGSCCProxy>(C))
634 for (const auto &OuterInvalidationPair :
635 OuterProxy->getOuterInvalidations()) {
636 AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
637 const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
638 if (Inv.invalidate(OuterAnalysisID, M, PA)) {
639 if (!InnerPA)
640 InnerPA = PA;
641 for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
642 InnerPA->abandon(InnerAnalysisID);
643 }
644 }
645
646 // Check if we needed a custom PA set. If so we'll need to run the inner
647 // invalidation.
648 if (InnerPA) {
649 InnerAM->invalidate(C, *InnerPA);
650 continue;
651 }
652
653 // Otherwise we only need to do invalidation if the original PA set didn't
654 // preserve all SCC analyses.
655 if (!AreSCCAnalysesPreserved)
656 InnerAM->invalidate(C, PA);
657 }
658
659 // Return false to indicate that this result is still a valid proxy.
660 return false;
661 }
662
663 template <>
664 CGSCCAnalysisManagerModuleProxy::Result
run(Module & M,ModuleAnalysisManager & AM)665 CGSCCAnalysisManagerModuleProxy::run(Module &M, ModuleAnalysisManager &AM) {
666 // Force the Function analysis manager to also be available so that it can
667 // be accessed in an SCC analysis and proxied onward to function passes.
668 // FIXME: It is pretty awkward to just drop the result here and assert that
669 // we can find it again later.
670 (void)AM.getResult<FunctionAnalysisManagerModuleProxy>(M);
671
672 return Result(*InnerAM, AM.getResult<LazyCallGraphAnalysis>(M));
673 }
674
675 AnalysisKey FunctionAnalysisManagerCGSCCProxy::Key;
676
677 FunctionAnalysisManagerCGSCCProxy::Result
run(LazyCallGraph::SCC & C,CGSCCAnalysisManager & AM,LazyCallGraph & CG)678 FunctionAnalysisManagerCGSCCProxy::run(LazyCallGraph::SCC &C,
679 CGSCCAnalysisManager &AM,
680 LazyCallGraph &CG) {
681 // Note: unconditionally getting checking that the proxy exists may get it at
682 // this point. There are cases when this is being run unnecessarily, but
683 // it is cheap and having the assertion in place is more valuable.
684 auto &MAMProxy = AM.getResult<ModuleAnalysisManagerCGSCCProxy>(C, CG);
685 Module &M = *C.begin()->getFunction().getParent();
686 bool ProxyExists =
687 MAMProxy.cachedResultExists<FunctionAnalysisManagerModuleProxy>(M);
688 assert(ProxyExists &&
689 "The CGSCC pass manager requires that the FAM module proxy is run "
690 "on the module prior to entering the CGSCC walk");
691 (void)ProxyExists;
692
693 // We just return an empty result. The caller will use the updateFAM interface
694 // to correctly register the relevant FunctionAnalysisManager based on the
695 // context in which this proxy is run.
696 return Result();
697 }
698
invalidate(LazyCallGraph::SCC & C,const PreservedAnalyses & PA,CGSCCAnalysisManager::Invalidator & Inv)699 bool FunctionAnalysisManagerCGSCCProxy::Result::invalidate(
700 LazyCallGraph::SCC &C, const PreservedAnalyses &PA,
701 CGSCCAnalysisManager::Invalidator &Inv) {
702 // If literally everything is preserved, we're done.
703 if (PA.areAllPreserved())
704 return false; // This is still a valid proxy.
705
706 // All updates to preserve valid results are done below, so we don't need to
707 // invalidate this proxy.
708 //
709 // Note that in order to preserve this proxy, a module pass must ensure that
710 // the FAM has been completely updated to handle the deletion of functions.
711 // Specifically, any FAM-cached results for those functions need to have been
712 // forcibly cleared. When preserved, this proxy will only invalidate results
713 // cached on functions *still in the module* at the end of the module pass.
714 auto PAC = PA.getChecker<FunctionAnalysisManagerCGSCCProxy>();
715 if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<LazyCallGraph::SCC>>()) {
716 for (LazyCallGraph::Node &N : C)
717 FAM->invalidate(N.getFunction(), PA);
718
719 return false;
720 }
721
722 // Directly check if the relevant set is preserved.
723 bool AreFunctionAnalysesPreserved =
724 PA.allAnalysesInSetPreserved<AllAnalysesOn<Function>>();
725
726 // Now walk all the functions to see if any inner analysis invalidation is
727 // necessary.
728 for (LazyCallGraph::Node &N : C) {
729 Function &F = N.getFunction();
730 Optional<PreservedAnalyses> FunctionPA;
731
732 // Check to see whether the preserved set needs to be pruned based on
733 // SCC-level analysis invalidation that triggers deferred invalidation
734 // registered with the outer analysis manager proxy for this function.
735 if (auto *OuterProxy =
736 FAM->getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F))
737 for (const auto &OuterInvalidationPair :
738 OuterProxy->getOuterInvalidations()) {
739 AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
740 const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
741 if (Inv.invalidate(OuterAnalysisID, C, PA)) {
742 if (!FunctionPA)
743 FunctionPA = PA;
744 for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
745 FunctionPA->abandon(InnerAnalysisID);
746 }
747 }
748
749 // Check if we needed a custom PA set, and if so we'll need to run the
750 // inner invalidation.
751 if (FunctionPA) {
752 FAM->invalidate(F, *FunctionPA);
753 continue;
754 }
755
756 // Otherwise we only need to do invalidation if the original PA set didn't
757 // preserve all function analyses.
758 if (!AreFunctionAnalysesPreserved)
759 FAM->invalidate(F, PA);
760 }
761
762 // Return false to indicate that this result is still a valid proxy.
763 return false;
764 }
765
766 } // end namespace llvm
767
768 /// When a new SCC is created for the graph we first update the
769 /// FunctionAnalysisManager in the Proxy's result.
770 /// As there might be function analysis results cached for the functions now in
771 /// that SCC, two forms of updates are required.
772 ///
773 /// First, a proxy from the SCC to the FunctionAnalysisManager needs to be
774 /// created so that any subsequent invalidation events to the SCC are
775 /// propagated to the function analysis results cached for functions within it.
776 ///
777 /// Second, if any of the functions within the SCC have analysis results with
778 /// outer analysis dependencies, then those dependencies would point to the
779 /// *wrong* SCC's analysis result. We forcibly invalidate the necessary
780 /// function analyses so that they don't retain stale handles.
updateNewSCCFunctionAnalyses(LazyCallGraph::SCC & C,LazyCallGraph & G,CGSCCAnalysisManager & AM,FunctionAnalysisManager & FAM)781 static void updateNewSCCFunctionAnalyses(LazyCallGraph::SCC &C,
782 LazyCallGraph &G,
783 CGSCCAnalysisManager &AM,
784 FunctionAnalysisManager &FAM) {
785 AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, G).updateFAM(FAM);
786
787 // Now walk the functions in this SCC and invalidate any function analysis
788 // results that might have outer dependencies on an SCC analysis.
789 for (LazyCallGraph::Node &N : C) {
790 Function &F = N.getFunction();
791
792 auto *OuterProxy =
793 FAM.getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F);
794 if (!OuterProxy)
795 // No outer analyses were queried, nothing to do.
796 continue;
797
798 // Forcibly abandon all the inner analyses with dependencies, but
799 // invalidate nothing else.
800 auto PA = PreservedAnalyses::all();
801 for (const auto &OuterInvalidationPair :
802 OuterProxy->getOuterInvalidations()) {
803 const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
804 for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
805 PA.abandon(InnerAnalysisID);
806 }
807
808 // Now invalidate anything we found.
809 FAM.invalidate(F, PA);
810 }
811 }
812
813 /// Helper function to update both the \c CGSCCAnalysisManager \p AM and the \c
814 /// CGSCCPassManager's \c CGSCCUpdateResult \p UR based on a range of newly
815 /// added SCCs.
816 ///
817 /// The range of new SCCs must be in postorder already. The SCC they were split
818 /// out of must be provided as \p C. The current node being mutated and
819 /// triggering updates must be passed as \p N.
820 ///
821 /// This function returns the SCC containing \p N. This will be either \p C if
822 /// no new SCCs have been split out, or it will be the new SCC containing \p N.
823 template <typename SCCRangeT>
824 static LazyCallGraph::SCC *
incorporateNewSCCRange(const SCCRangeT & NewSCCRange,LazyCallGraph & G,LazyCallGraph::Node & N,LazyCallGraph::SCC * C,CGSCCAnalysisManager & AM,CGSCCUpdateResult & UR)825 incorporateNewSCCRange(const SCCRangeT &NewSCCRange, LazyCallGraph &G,
826 LazyCallGraph::Node &N, LazyCallGraph::SCC *C,
827 CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR) {
828 using SCC = LazyCallGraph::SCC;
829
830 if (NewSCCRange.empty())
831 return C;
832
833 // Add the current SCC to the worklist as its shape has changed.
834 UR.CWorklist.insert(C);
835 LLVM_DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist:" << *C
836 << "\n");
837
838 SCC *OldC = C;
839
840 // Update the current SCC. Note that if we have new SCCs, this must actually
841 // change the SCC.
842 assert(C != &*NewSCCRange.begin() &&
843 "Cannot insert new SCCs without changing current SCC!");
844 C = &*NewSCCRange.begin();
845 assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
846
847 // If we had a cached FAM proxy originally, we will want to create more of
848 // them for each SCC that was split off.
849 FunctionAnalysisManager *FAM = nullptr;
850 if (auto *FAMProxy =
851 AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(*OldC))
852 FAM = &FAMProxy->getManager();
853
854 // We need to propagate an invalidation call to all but the newly current SCC
855 // because the outer pass manager won't do that for us after splitting them.
856 // FIXME: We should accept a PreservedAnalysis from the CG updater so that if
857 // there are preserved analysis we can avoid invalidating them here for
858 // split-off SCCs.
859 // We know however that this will preserve any FAM proxy so go ahead and mark
860 // that.
861 PreservedAnalyses PA;
862 PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
863 AM.invalidate(*OldC, PA);
864
865 // Ensure the now-current SCC's function analyses are updated.
866 if (FAM)
867 updateNewSCCFunctionAnalyses(*C, G, AM, *FAM);
868
869 for (SCC &NewC : llvm::reverse(llvm::drop_begin(NewSCCRange))) {
870 assert(C != &NewC && "No need to re-visit the current SCC!");
871 assert(OldC != &NewC && "Already handled the original SCC!");
872 UR.CWorklist.insert(&NewC);
873 LLVM_DEBUG(dbgs() << "Enqueuing a newly formed SCC:" << NewC << "\n");
874
875 // Ensure new SCCs' function analyses are updated.
876 if (FAM)
877 updateNewSCCFunctionAnalyses(NewC, G, AM, *FAM);
878
879 // Also propagate a normal invalidation to the new SCC as only the current
880 // will get one from the pass manager infrastructure.
881 AM.invalidate(NewC, PA);
882 }
883 return C;
884 }
885
updateCGAndAnalysisManagerForPass(LazyCallGraph & G,LazyCallGraph::SCC & InitialC,LazyCallGraph::Node & N,CGSCCAnalysisManager & AM,CGSCCUpdateResult & UR,FunctionAnalysisManager & FAM,bool FunctionPass)886 static LazyCallGraph::SCC &updateCGAndAnalysisManagerForPass(
887 LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
888 CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
889 FunctionAnalysisManager &FAM, bool FunctionPass) {
890 using Node = LazyCallGraph::Node;
891 using Edge = LazyCallGraph::Edge;
892 using SCC = LazyCallGraph::SCC;
893 using RefSCC = LazyCallGraph::RefSCC;
894
895 RefSCC &InitialRC = InitialC.getOuterRefSCC();
896 SCC *C = &InitialC;
897 RefSCC *RC = &InitialRC;
898 Function &F = N.getFunction();
899
900 // Walk the function body and build up the set of retained, promoted, and
901 // demoted edges.
902 SmallVector<Constant *, 16> Worklist;
903 SmallPtrSet<Constant *, 16> Visited;
904 SmallPtrSet<Node *, 16> RetainedEdges;
905 SmallSetVector<Node *, 4> PromotedRefTargets;
906 SmallSetVector<Node *, 4> DemotedCallTargets;
907 SmallSetVector<Node *, 4> NewCallEdges;
908 SmallSetVector<Node *, 4> NewRefEdges;
909
910 // First walk the function and handle all called functions. We do this first
911 // because if there is a single call edge, whether there are ref edges is
912 // irrelevant.
913 for (Instruction &I : instructions(F)) {
914 if (auto *CB = dyn_cast<CallBase>(&I)) {
915 if (Function *Callee = CB->getCalledFunction()) {
916 if (Visited.insert(Callee).second && !Callee->isDeclaration()) {
917 Node *CalleeN = G.lookup(*Callee);
918 assert(CalleeN &&
919 "Visited function should already have an associated node");
920 Edge *E = N->lookup(*CalleeN);
921 assert((E || !FunctionPass) &&
922 "No function transformations should introduce *new* "
923 "call edges! Any new calls should be modeled as "
924 "promoted existing ref edges!");
925 bool Inserted = RetainedEdges.insert(CalleeN).second;
926 (void)Inserted;
927 assert(Inserted && "We should never visit a function twice.");
928 if (!E)
929 NewCallEdges.insert(CalleeN);
930 else if (!E->isCall())
931 PromotedRefTargets.insert(CalleeN);
932 }
933 } else {
934 // We can miss devirtualization if an indirect call is created then
935 // promoted before updateCGAndAnalysisManagerForPass runs.
936 auto *Entry = UR.IndirectVHs.find(CB);
937 if (Entry == UR.IndirectVHs.end())
938 UR.IndirectVHs.insert({CB, WeakTrackingVH(CB)});
939 else if (!Entry->second)
940 Entry->second = WeakTrackingVH(CB);
941 }
942 }
943 }
944
945 // Now walk all references.
946 for (Instruction &I : instructions(F))
947 for (Value *Op : I.operand_values())
948 if (auto *OpC = dyn_cast<Constant>(Op))
949 if (Visited.insert(OpC).second)
950 Worklist.push_back(OpC);
951
952 auto VisitRef = [&](Function &Referee) {
953 Node *RefereeN = G.lookup(Referee);
954 assert(RefereeN &&
955 "Visited function should already have an associated node");
956 Edge *E = N->lookup(*RefereeN);
957 assert((E || !FunctionPass) &&
958 "No function transformations should introduce *new* ref "
959 "edges! Any new ref edges would require IPO which "
960 "function passes aren't allowed to do!");
961 bool Inserted = RetainedEdges.insert(RefereeN).second;
962 (void)Inserted;
963 assert(Inserted && "We should never visit a function twice.");
964 if (!E)
965 NewRefEdges.insert(RefereeN);
966 else if (E->isCall())
967 DemotedCallTargets.insert(RefereeN);
968 };
969 LazyCallGraph::visitReferences(Worklist, Visited, VisitRef);
970
971 // Handle new ref edges.
972 for (Node *RefTarget : NewRefEdges) {
973 SCC &TargetC = *G.lookupSCC(*RefTarget);
974 RefSCC &TargetRC = TargetC.getOuterRefSCC();
975 (void)TargetRC;
976 // TODO: This only allows trivial edges to be added for now.
977 #ifdef EXPENSIVE_CHECKS
978 assert((RC == &TargetRC ||
979 RC->isAncestorOf(TargetRC)) && "New ref edge is not trivial!");
980 #endif
981 RC->insertTrivialRefEdge(N, *RefTarget);
982 }
983
984 // Handle new call edges.
985 for (Node *CallTarget : NewCallEdges) {
986 SCC &TargetC = *G.lookupSCC(*CallTarget);
987 RefSCC &TargetRC = TargetC.getOuterRefSCC();
988 (void)TargetRC;
989 // TODO: This only allows trivial edges to be added for now.
990 #ifdef EXPENSIVE_CHECKS
991 assert((RC == &TargetRC ||
992 RC->isAncestorOf(TargetRC)) && "New call edge is not trivial!");
993 #endif
994 // Add a trivial ref edge to be promoted later on alongside
995 // PromotedRefTargets.
996 RC->insertTrivialRefEdge(N, *CallTarget);
997 }
998
999 // Include synthetic reference edges to known, defined lib functions.
1000 for (auto *LibFn : G.getLibFunctions())
1001 // While the list of lib functions doesn't have repeats, don't re-visit
1002 // anything handled above.
1003 if (!Visited.count(LibFn))
1004 VisitRef(*LibFn);
1005
1006 // First remove all of the edges that are no longer present in this function.
1007 // The first step makes these edges uniformly ref edges and accumulates them
1008 // into a separate data structure so removal doesn't invalidate anything.
1009 SmallVector<Node *, 4> DeadTargets;
1010 for (Edge &E : *N) {
1011 if (RetainedEdges.count(&E.getNode()))
1012 continue;
1013
1014 SCC &TargetC = *G.lookupSCC(E.getNode());
1015 RefSCC &TargetRC = TargetC.getOuterRefSCC();
1016 if (&TargetRC == RC && E.isCall()) {
1017 if (C != &TargetC) {
1018 // For separate SCCs this is trivial.
1019 RC->switchTrivialInternalEdgeToRef(N, E.getNode());
1020 } else {
1021 // Now update the call graph.
1022 C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, E.getNode()),
1023 G, N, C, AM, UR);
1024 }
1025 }
1026
1027 // Now that this is ready for actual removal, put it into our list.
1028 DeadTargets.push_back(&E.getNode());
1029 }
1030 // Remove the easy cases quickly and actually pull them out of our list.
1031 llvm::erase_if(DeadTargets, [&](Node *TargetN) {
1032 SCC &TargetC = *G.lookupSCC(*TargetN);
1033 RefSCC &TargetRC = TargetC.getOuterRefSCC();
1034
1035 // We can't trivially remove internal targets, so skip
1036 // those.
1037 if (&TargetRC == RC)
1038 return false;
1039
1040 LLVM_DEBUG(dbgs() << "Deleting outgoing edge from '" << N << "' to '"
1041 << *TargetN << "'\n");
1042 RC->removeOutgoingEdge(N, *TargetN);
1043 return true;
1044 });
1045
1046 // Now do a batch removal of the internal ref edges left.
1047 auto NewRefSCCs = RC->removeInternalRefEdge(N, DeadTargets);
1048 if (!NewRefSCCs.empty()) {
1049 // The old RefSCC is dead, mark it as such.
1050 UR.InvalidatedRefSCCs.insert(RC);
1051
1052 // Note that we don't bother to invalidate analyses as ref-edge
1053 // connectivity is not really observable in any way and is intended
1054 // exclusively to be used for ordering of transforms rather than for
1055 // analysis conclusions.
1056
1057 // Update RC to the "bottom".
1058 assert(G.lookupSCC(N) == C && "Changed the SCC when splitting RefSCCs!");
1059 RC = &C->getOuterRefSCC();
1060 assert(G.lookupRefSCC(N) == RC && "Failed to update current RefSCC!");
1061
1062 // The RC worklist is in reverse postorder, so we enqueue the new ones in
1063 // RPO except for the one which contains the source node as that is the
1064 // "bottom" we will continue processing in the bottom-up walk.
1065 assert(NewRefSCCs.front() == RC &&
1066 "New current RefSCC not first in the returned list!");
1067 for (RefSCC *NewRC : llvm::reverse(llvm::drop_begin(NewRefSCCs))) {
1068 assert(NewRC != RC && "Should not encounter the current RefSCC further "
1069 "in the postorder list of new RefSCCs.");
1070 UR.RCWorklist.insert(NewRC);
1071 LLVM_DEBUG(dbgs() << "Enqueuing a new RefSCC in the update worklist: "
1072 << *NewRC << "\n");
1073 }
1074 }
1075
1076 // Next demote all the call edges that are now ref edges. This helps make
1077 // the SCCs small which should minimize the work below as we don't want to
1078 // form cycles that this would break.
1079 for (Node *RefTarget : DemotedCallTargets) {
1080 SCC &TargetC = *G.lookupSCC(*RefTarget);
1081 RefSCC &TargetRC = TargetC.getOuterRefSCC();
1082
1083 // The easy case is when the target RefSCC is not this RefSCC. This is
1084 // only supported when the target RefSCC is a child of this RefSCC.
1085 if (&TargetRC != RC) {
1086 #ifdef EXPENSIVE_CHECKS
1087 assert(RC->isAncestorOf(TargetRC) &&
1088 "Cannot potentially form RefSCC cycles here!");
1089 #endif
1090 RC->switchOutgoingEdgeToRef(N, *RefTarget);
1091 LLVM_DEBUG(dbgs() << "Switch outgoing call edge to a ref edge from '" << N
1092 << "' to '" << *RefTarget << "'\n");
1093 continue;
1094 }
1095
1096 // We are switching an internal call edge to a ref edge. This may split up
1097 // some SCCs.
1098 if (C != &TargetC) {
1099 // For separate SCCs this is trivial.
1100 RC->switchTrivialInternalEdgeToRef(N, *RefTarget);
1101 continue;
1102 }
1103
1104 // Now update the call graph.
1105 C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, *RefTarget), G, N,
1106 C, AM, UR);
1107 }
1108
1109 // We added a ref edge earlier for new call edges, promote those to call edges
1110 // alongside PromotedRefTargets.
1111 for (Node *E : NewCallEdges)
1112 PromotedRefTargets.insert(E);
1113
1114 // Now promote ref edges into call edges.
1115 for (Node *CallTarget : PromotedRefTargets) {
1116 SCC &TargetC = *G.lookupSCC(*CallTarget);
1117 RefSCC &TargetRC = TargetC.getOuterRefSCC();
1118
1119 // The easy case is when the target RefSCC is not this RefSCC. This is
1120 // only supported when the target RefSCC is a child of this RefSCC.
1121 if (&TargetRC != RC) {
1122 #ifdef EXPENSIVE_CHECKS
1123 assert(RC->isAncestorOf(TargetRC) &&
1124 "Cannot potentially form RefSCC cycles here!");
1125 #endif
1126 RC->switchOutgoingEdgeToCall(N, *CallTarget);
1127 LLVM_DEBUG(dbgs() << "Switch outgoing ref edge to a call edge from '" << N
1128 << "' to '" << *CallTarget << "'\n");
1129 continue;
1130 }
1131 LLVM_DEBUG(dbgs() << "Switch an internal ref edge to a call edge from '"
1132 << N << "' to '" << *CallTarget << "'\n");
1133
1134 // Otherwise we are switching an internal ref edge to a call edge. This
1135 // may merge away some SCCs, and we add those to the UpdateResult. We also
1136 // need to make sure to update the worklist in the event SCCs have moved
1137 // before the current one in the post-order sequence
1138 bool HasFunctionAnalysisProxy = false;
1139 auto InitialSCCIndex = RC->find(*C) - RC->begin();
1140 bool FormedCycle = RC->switchInternalEdgeToCall(
1141 N, *CallTarget, [&](ArrayRef<SCC *> MergedSCCs) {
1142 for (SCC *MergedC : MergedSCCs) {
1143 assert(MergedC != &TargetC && "Cannot merge away the target SCC!");
1144
1145 HasFunctionAnalysisProxy |=
1146 AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(
1147 *MergedC) != nullptr;
1148
1149 // Mark that this SCC will no longer be valid.
1150 UR.InvalidatedSCCs.insert(MergedC);
1151
1152 // FIXME: We should really do a 'clear' here to forcibly release
1153 // memory, but we don't have a good way of doing that and
1154 // preserving the function analyses.
1155 auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
1156 PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
1157 AM.invalidate(*MergedC, PA);
1158 }
1159 });
1160
1161 // If we formed a cycle by creating this call, we need to update more data
1162 // structures.
1163 if (FormedCycle) {
1164 C = &TargetC;
1165 assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
1166
1167 // If one of the invalidated SCCs had a cached proxy to a function
1168 // analysis manager, we need to create a proxy in the new current SCC as
1169 // the invalidated SCCs had their functions moved.
1170 if (HasFunctionAnalysisProxy)
1171 AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, G).updateFAM(FAM);
1172
1173 // Any analyses cached for this SCC are no longer precise as the shape
1174 // has changed by introducing this cycle. However, we have taken care to
1175 // update the proxies so it remains valide.
1176 auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
1177 PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
1178 AM.invalidate(*C, PA);
1179 }
1180 auto NewSCCIndex = RC->find(*C) - RC->begin();
1181 // If we have actually moved an SCC to be topologically "below" the current
1182 // one due to merging, we will need to revisit the current SCC after
1183 // visiting those moved SCCs.
1184 //
1185 // It is critical that we *do not* revisit the current SCC unless we
1186 // actually move SCCs in the process of merging because otherwise we may
1187 // form a cycle where an SCC is split apart, merged, split, merged and so
1188 // on infinitely.
1189 if (InitialSCCIndex < NewSCCIndex) {
1190 // Put our current SCC back onto the worklist as we'll visit other SCCs
1191 // that are now definitively ordered prior to the current one in the
1192 // post-order sequence, and may end up observing more precise context to
1193 // optimize the current SCC.
1194 UR.CWorklist.insert(C);
1195 LLVM_DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist: " << *C
1196 << "\n");
1197 // Enqueue in reverse order as we pop off the back of the worklist.
1198 for (SCC &MovedC : llvm::reverse(make_range(RC->begin() + InitialSCCIndex,
1199 RC->begin() + NewSCCIndex))) {
1200 UR.CWorklist.insert(&MovedC);
1201 LLVM_DEBUG(dbgs() << "Enqueuing a newly earlier in post-order SCC: "
1202 << MovedC << "\n");
1203 }
1204 }
1205 }
1206
1207 assert(!UR.InvalidatedSCCs.count(C) && "Invalidated the current SCC!");
1208 assert(!UR.InvalidatedRefSCCs.count(RC) && "Invalidated the current RefSCC!");
1209 assert(&C->getOuterRefSCC() == RC && "Current SCC not in current RefSCC!");
1210
1211 // Record the current RefSCC and SCC for higher layers of the CGSCC pass
1212 // manager now that all the updates have been applied.
1213 if (RC != &InitialRC)
1214 UR.UpdatedRC = RC;
1215 if (C != &InitialC)
1216 UR.UpdatedC = C;
1217
1218 return *C;
1219 }
1220
updateCGAndAnalysisManagerForFunctionPass(LazyCallGraph & G,LazyCallGraph::SCC & InitialC,LazyCallGraph::Node & N,CGSCCAnalysisManager & AM,CGSCCUpdateResult & UR,FunctionAnalysisManager & FAM)1221 LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForFunctionPass(
1222 LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
1223 CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
1224 FunctionAnalysisManager &FAM) {
1225 return updateCGAndAnalysisManagerForPass(G, InitialC, N, AM, UR, FAM,
1226 /* FunctionPass */ true);
1227 }
updateCGAndAnalysisManagerForCGSCCPass(LazyCallGraph & G,LazyCallGraph::SCC & InitialC,LazyCallGraph::Node & N,CGSCCAnalysisManager & AM,CGSCCUpdateResult & UR,FunctionAnalysisManager & FAM)1228 LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForCGSCCPass(
1229 LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
1230 CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
1231 FunctionAnalysisManager &FAM) {
1232 return updateCGAndAnalysisManagerForPass(G, InitialC, N, AM, UR, FAM,
1233 /* FunctionPass */ false);
1234 }
1235