llvm.org GIT mirror llvm / 8bf2780 lib / Analysis / CGSCCPassManager.cpp
8bf2780

Tree @8bf2780 (Download .tar.gz)

CGSCCPassManager.cpp @8bf2780raw · history · blame

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
//===- CGSCCPassManager.cpp - Managing & running CGSCC passes -------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/CGSCCPassManager.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/InstIterator.h"

using namespace llvm;

// Explicit template instantiations and specialization defininitions for core
// template typedefs.
namespace llvm {

// Explicit instantiations for the core proxy templates.
template class AllAnalysesOn<LazyCallGraph::SCC>;
template class AnalysisManager<LazyCallGraph::SCC, LazyCallGraph &>;
template class PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager,
                           LazyCallGraph &, CGSCCUpdateResult &>;
template class InnerAnalysisManagerProxy<CGSCCAnalysisManager, Module>;
template class OuterAnalysisManagerProxy<ModuleAnalysisManager,
                                         LazyCallGraph::SCC, LazyCallGraph &>;
template class InnerAnalysisManagerProxy<FunctionAnalysisManager,
                                         LazyCallGraph::SCC, LazyCallGraph &>;
template class OuterAnalysisManagerProxy<CGSCCAnalysisManager, Function>;

/// Explicitly specialize the pass manager run method to handle call graph
/// updates.
template <>
PreservedAnalyses
PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager, LazyCallGraph &,
            CGSCCUpdateResult &>::run(LazyCallGraph::SCC &InitialC,
                                      CGSCCAnalysisManager &AM,
                                      LazyCallGraph &G, CGSCCUpdateResult &UR) {
  PreservedAnalyses PA = PreservedAnalyses::all();

  if (DebugLogging)
    dbgs() << "Starting CGSCC pass manager run.\n";

  // The SCC may be refined while we are running passes over it, so set up
  // a pointer that we can update.
  LazyCallGraph::SCC *C = &InitialC;

  for (auto &Pass : Passes) {
    if (DebugLogging)
      dbgs() << "Running pass: " << Pass->name() << " on " << *C << "\n";

    PreservedAnalyses PassPA = Pass->run(*C, AM, G, UR);

    // Update the SCC if necessary.
    C = UR.UpdatedC ? UR.UpdatedC : C;

    // Check that we didn't miss any update scenario.
    assert(!UR.InvalidatedSCCs.count(C) && "Processing an invalid SCC!");
    assert(C->begin() != C->end() && "Cannot have an empty SCC!");

    // Update the analysis manager as each pass runs and potentially
    // invalidates analyses.
    AM.invalidate(*C, PassPA);

    // Finally, we intersect the final preserved analyses to compute the
    // aggregate preserved set for this pass manager.
    PA.intersect(std::move(PassPA));

    // FIXME: Historically, the pass managers all called the LLVM context's
    // yield function here. We don't have a generic way to acquire the
    // context and it isn't yet clear what the right pattern is for yielding
    // in the new pass manager so it is currently omitted.
    // ...getContext().yield();
  }

  // Invaliadtion was handled after each pass in the above loop for the current
  // SCC. Therefore, the remaining analysis results in the AnalysisManager are
  // preserved. We mark this with a set so that we don't need to inspect each
  // one individually.
  PA.preserve<AllAnalysesOn<LazyCallGraph::SCC>>();

  if (DebugLogging)
    dbgs() << "Finished CGSCC pass manager run.\n";

  return PA;
}

bool CGSCCAnalysisManagerModuleProxy::Result::invalidate(
    Module &M, const PreservedAnalyses &PA,
    ModuleAnalysisManager::Invalidator &Inv) {
  // If this proxy or the call graph is going to be invalidated, we also need
  // to clear all the keys coming from that analysis.
  //
  // We also directly invalidate the FAM's module proxy if necessary, and if
  // that proxy isn't preserved we can't preserve this proxy either. We rely on
  // it to handle module -> function analysis invalidation in the face of
  // structural changes and so if it's unavailable we conservatively clear the
  // entire SCC layer as well rather than trying to do invaliadtion ourselves.
  if (!PA.preserved<CGSCCAnalysisManagerModuleProxy>() ||
      Inv.invalidate<LazyCallGraphAnalysis>(M, PA) ||
      Inv.invalidate<FunctionAnalysisManagerModuleProxy>(M, PA)) {
    InnerAM->clear();

    // And the proxy itself should be marked as invalid so that we can observe
    // the new call graph. This isn't strictly necessary because we cheat
    // above, but is still useful.
    return true;
  }

  // Ok, we have a graph, so we can propagate the invalidation down into it.
  for (auto &RC : G->postorder_ref_sccs())
    for (auto &C : RC)
      InnerAM->invalidate(C, PA);

  // Return false to indicate that this result is still a valid proxy.
  return false;
}

template <>
CGSCCAnalysisManagerModuleProxy::Result
CGSCCAnalysisManagerModuleProxy::run(Module &M, ModuleAnalysisManager &AM) {
  // Force the Function analysis manager to also be available so that it can
  // be accessed in an SCC analysis and proxied onward to function passes.
  // FIXME: It is pretty awkward to just drop the result here and assert that
  // we can find it again later.
  (void)AM.getResult<FunctionAnalysisManagerModuleProxy>(M);

  return Result(*InnerAM, AM.getResult<LazyCallGraphAnalysis>(M));
}

AnalysisKey FunctionAnalysisManagerCGSCCProxy::Key;

FunctionAnalysisManagerCGSCCProxy::Result
FunctionAnalysisManagerCGSCCProxy::run(LazyCallGraph::SCC &C,
                                       CGSCCAnalysisManager &AM,
                                       LazyCallGraph &CG) {
  // Collect the FunctionAnalysisManager from the Module layer and use that to
  // build the proxy result.
  //
  // This allows us to rely on the FunctionAnalysisMangaerModuleProxy to
  // invalidate the function analyses.
  auto &MAM = AM.getResult<ModuleAnalysisManagerCGSCCProxy>(C, CG).getManager();
  Module &M = *C.begin()->getFunction().getParent();
  auto *FAMProxy = MAM.getCachedResult<FunctionAnalysisManagerModuleProxy>(M);
  assert(FAMProxy && "The CGSCC pass manager requires that the FAM module "
                     "proxy is run on the module prior to entering the CGSCC "
                     "walk.");

  // Note that we special-case invalidation handling of this proxy in the CGSCC
  // analysis manager's Module proxy. This avoids the need to do anything
  // special here to recompute all of this if ever the FAM's module proxy goes
  // away.
  return Result(FAMProxy->getManager());
}

bool FunctionAnalysisManagerCGSCCProxy::Result::invalidate(
    LazyCallGraph::SCC &C, const PreservedAnalyses &PA,
    CGSCCAnalysisManager::Invalidator &Inv) {
  for (LazyCallGraph::Node &N : C)
    FAM->invalidate(N.getFunction(), PA);

  // This proxy doesn't need to handle invalidation itself. Instead, the
  // module-level CGSCC proxy handles it above by ensuring that if the
  // module-level FAM proxy becomes invalid the entire SCC layer, which
  // includes this proxy, is cleared.
  return false;
}

} // End llvm namespace

namespace {
/// Helper function to update both the \c CGSCCAnalysisManager \p AM and the \c
/// CGSCCPassManager's \c CGSCCUpdateResult \p UR based on a range of newly
/// added SCCs.
///
/// The range of new SCCs must be in postorder already. The SCC they were split
/// out of must be provided as \p C. The current node being mutated and
/// triggering updates must be passed as \p N.
///
/// This function returns the SCC containing \p N. This will be either \p C if
/// no new SCCs have been split out, or it will be the new SCC containing \p N.
template <typename SCCRangeT>
LazyCallGraph::SCC *
incorporateNewSCCRange(const SCCRangeT &NewSCCRange, LazyCallGraph &G,
                       LazyCallGraph::Node &N, LazyCallGraph::SCC *C,
                       CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
                       bool DebugLogging = false) {
  typedef LazyCallGraph::SCC SCC;

  if (NewSCCRange.begin() == NewSCCRange.end())
    return C;

  // Invalidate the analyses of the current SCC and add it to the worklist since
  // it has changed its shape.
  AM.invalidate(*C, PreservedAnalyses::none());
  UR.CWorklist.insert(C);
  if (DebugLogging)
    dbgs() << "Enqueuing the existing SCC in the worklist:" << *C << "\n";

  SCC *OldC = C;
  (void)OldC;

  // Update the current SCC. Note that if we have new SCCs, this must actually
  // change the SCC.
  assert(C != &*NewSCCRange.begin() &&
         "Cannot insert new SCCs without changing current SCC!");
  C = &*NewSCCRange.begin();
  assert(G.lookupSCC(N) == C && "Failed to update current SCC!");

  for (SCC &NewC :
       reverse(make_range(std::next(NewSCCRange.begin()), NewSCCRange.end()))) {
    assert(C != &NewC && "No need to re-visit the current SCC!");
    assert(OldC != &NewC && "Already handled the original SCC!");
    UR.CWorklist.insert(&NewC);
    if (DebugLogging)
      dbgs() << "Enqueuing a newly formed SCC:" << NewC << "\n";
  }
  return C;
}
}

LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForFunctionPass(
    LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
    CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR, bool DebugLogging) {
  typedef LazyCallGraph::Node Node;
  typedef LazyCallGraph::Edge Edge;
  typedef LazyCallGraph::SCC SCC;
  typedef LazyCallGraph::RefSCC RefSCC;

  RefSCC &InitialRC = InitialC.getOuterRefSCC();
  SCC *C = &InitialC;
  RefSCC *RC = &InitialRC;
  Function &F = N.getFunction();

  // Walk the function body and build up the set of retained, promoted, and
  // demoted edges.
  SmallVector<Constant *, 16> Worklist;
  SmallPtrSet<Constant *, 16> Visited;
  SmallPtrSet<Function *, 16> RetainedEdges;
  SmallSetVector<Function *, 4> PromotedRefTargets;
  SmallSetVector<Function *, 4> DemotedCallTargets;

  // First walk the function and handle all called functions. We do this first
  // because if there is a single call edge, whether there are ref edges is
  // irrelevant.
  for (Instruction &I : instructions(F))
    if (auto CS = CallSite(&I))
      if (Function *Callee = CS.getCalledFunction())
        if (Visited.insert(Callee).second && !Callee->isDeclaration()) {
          const Edge *E = N.lookup(*Callee);
          // FIXME: We should really handle adding new calls. While it will
          // make downstream usage more complex, there is no fundamental
          // limitation and it will allow passes within the CGSCC to be a bit
          // more flexible in what transforms they can do. Until then, we
          // verify that new calls haven't been introduced.
          assert(E && "No function transformations should introduce *new* "
                      "call edges! Any new calls should be modeled as "
                      "promoted existing ref edges!");
          RetainedEdges.insert(Callee);
          if (!E->isCall())
            PromotedRefTargets.insert(Callee);
        }

  // Now walk all references.
  for (Instruction &I : instructions(F))
    for (Value *Op : I.operand_values())
      if (Constant *C = dyn_cast<Constant>(Op))
        if (Visited.insert(C).second)
          Worklist.push_back(C);

  LazyCallGraph::visitReferences(Worklist, Visited, [&](Function &Referee) {
    const Edge *E = N.lookup(Referee);
    // FIXME: Similarly to new calls, we also currently preclude
    // introducing new references. See above for details.
    assert(E && "No function transformations should introduce *new* ref "
                "edges! Any new ref edges would require IPO which "
                "function passes aren't allowed to do!");
    RetainedEdges.insert(&Referee);
    if (E->isCall())
      DemotedCallTargets.insert(&Referee);
  });

  // First remove all of the edges that are no longer present in this function.
  // We have to build a list of dead targets first and then remove them as the
  // data structures will all be invalidated by removing them.
  SmallVector<PointerIntPair<Node *, 1, Edge::Kind>, 4> DeadTargets;
  for (Edge &E : N)
    if (!RetainedEdges.count(&E.getFunction()))
      DeadTargets.push_back({E.getNode(), E.getKind()});
  for (auto DeadTarget : DeadTargets) {
    Node &TargetN = *DeadTarget.getPointer();
    bool IsCall = DeadTarget.getInt() == Edge::Call;
    SCC &TargetC = *G.lookupSCC(TargetN);
    RefSCC &TargetRC = TargetC.getOuterRefSCC();

    if (&TargetRC != RC) {
      RC->removeOutgoingEdge(N, TargetN);
      if (DebugLogging)
        dbgs() << "Deleting outgoing edge from '" << N << "' to '" << TargetN
               << "'\n";
      continue;
    }
    if (DebugLogging)
      dbgs() << "Deleting internal " << (IsCall ? "call" : "ref")
             << " edge from '" << N << "' to '" << TargetN << "'\n";

    if (IsCall)
      C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, TargetN), G, N,
                                 C, AM, UR, DebugLogging);

    auto NewRefSCCs = RC->removeInternalRefEdge(N, TargetN);
    if (!NewRefSCCs.empty()) {
      // Note that we don't bother to invalidate analyses as ref-edge
      // connectivity is not really observable in any way and is intended
      // exclusively to be used for ordering of transforms rather than for
      // analysis conclusions.

      // The RC worklist is in reverse postorder, so we first enqueue the
      // current RefSCC as it will remain the parent of all split RefSCCs, then
      // we enqueue the new ones in RPO except for the one which contains the
      // source node as that is the "bottom" we will continue processing in the
      // bottom-up walk.
      UR.RCWorklist.insert(RC);
      if (DebugLogging)
        dbgs() << "Enqueuing the existing RefSCC in the update worklist: "
               << *RC << "\n";
      // Update the RC to the "bottom".
      assert(G.lookupSCC(N) == C && "Changed the SCC when splitting RefSCCs!");
      RC = &C->getOuterRefSCC();
      assert(G.lookupRefSCC(N) == RC && "Failed to update current RefSCC!");
      for (RefSCC *NewRC : reverse(NewRefSCCs))
        if (NewRC != RC) {
          UR.RCWorklist.insert(NewRC);
          if (DebugLogging)
            dbgs() << "Enqueuing a new RefSCC in the update worklist: "
                   << *NewRC << "\n";
        }
    }
  }

  // Next demote all the call edges that are now ref edges. This helps make
  // the SCCs small which should minimize the work below as we don't want to
  // form cycles that this would break.
  for (Function *RefTarget : DemotedCallTargets) {
    Node &TargetN = *G.lookup(*RefTarget);
    SCC &TargetC = *G.lookupSCC(TargetN);
    RefSCC &TargetRC = TargetC.getOuterRefSCC();

    // The easy case is when the target RefSCC is not this RefSCC. This is
    // only supported when the target RefSCC is a child of this RefSCC.
    if (&TargetRC != RC) {
      assert(RC->isAncestorOf(TargetRC) &&
             "Cannot potentially form RefSCC cycles here!");
      RC->switchOutgoingEdgeToRef(N, TargetN);
      if (DebugLogging)
        dbgs() << "Switch outgoing call edge to a ref edge from '" << N
               << "' to '" << TargetN << "'\n";
      continue;
    }

    // Otherwise we are switching an internal call edge to a ref edge. This
    // may split up some SCCs.
    C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, TargetN), G, N, C,
                               AM, UR, DebugLogging);
  }

  // Now promote ref edges into call edges.
  for (Function *CallTarget : PromotedRefTargets) {
    Node &TargetN = *G.lookup(*CallTarget);
    SCC &TargetC = *G.lookupSCC(TargetN);
    RefSCC &TargetRC = TargetC.getOuterRefSCC();

    // The easy case is when the target RefSCC is not this RefSCC. This is
    // only supported when the target RefSCC is a child of this RefSCC.
    if (&TargetRC != RC) {
      assert(RC->isAncestorOf(TargetRC) &&
             "Cannot potentially form RefSCC cycles here!");
      RC->switchOutgoingEdgeToCall(N, TargetN);
      if (DebugLogging)
        dbgs() << "Switch outgoing ref edge to a call edge from '" << N
               << "' to '" << TargetN << "'\n";
      continue;
    }
    if (DebugLogging)
      dbgs() << "Switch an internal ref edge to a call edge from '" << N
             << "' to '" << TargetN << "'\n";

    // Otherwise we are switching an internal ref edge to a call edge. This
    // may merge away some SCCs, and we add those to the UpdateResult. We also
    // need to make sure to update the worklist in the event SCCs have moved
    // before the current one in the post-order sequence.
    auto InitialSCCIndex = RC->find(*C) - RC->begin();
    auto InvalidatedSCCs = RC->switchInternalEdgeToCall(N, TargetN);
    if (!InvalidatedSCCs.empty()) {
      C = &TargetC;
      assert(G.lookupSCC(N) == C && "Failed to update current SCC!");

      // Any analyses cached for this SCC are no longer precise as the shape
      // has changed by introducing this cycle.
      AM.invalidate(*C, PreservedAnalyses::none());

      for (SCC *InvalidatedC : InvalidatedSCCs) {
        assert(InvalidatedC != C && "Cannot invalidate the current SCC!");
        UR.InvalidatedSCCs.insert(InvalidatedC);

        // Also clear any cached analyses for the SCCs that are dead. This
        // isn't really necessary for correctness but can release memory.
        AM.clear(*InvalidatedC);
      }
    }
    auto NewSCCIndex = RC->find(*C) - RC->begin();
    if (InitialSCCIndex < NewSCCIndex) {
      // Put our current SCC back onto the worklist as we'll visit other SCCs
      // that are now definitively ordered prior to the current one in the
      // post-order sequence, and may end up observing more precise context to
      // optimize the current SCC.
      UR.CWorklist.insert(C);
      if (DebugLogging)
        dbgs() << "Enqueuing the existing SCC in the worklist: " << *C << "\n";
      // Enqueue in reverse order as we pop off the back of the worklist.
      for (SCC &MovedC : reverse(make_range(RC->begin() + InitialSCCIndex,
                                            RC->begin() + NewSCCIndex))) {
        UR.CWorklist.insert(&MovedC);
        if (DebugLogging)
          dbgs() << "Enqueuing a newly earlier in post-order SCC: " << MovedC
                 << "\n";
      }
    }
  }

  assert(!UR.InvalidatedSCCs.count(C) && "Invalidated the current SCC!");
  assert(!UR.InvalidatedRefSCCs.count(RC) && "Invalidated the current RefSCC!");
  assert(&C->getOuterRefSCC() == RC && "Current SCC not in current RefSCC!");

  // Record the current RefSCC and SCC for higher layers of the CGSCC pass
  // manager now that all the updates have been applied.
  if (RC != &InitialRC)
    UR.UpdatedRC = RC;
  if (C != &InitialC)
    UR.UpdatedC = C;

  return *C;
}