llvm/lib/Analysis/LoopAnalysisManager.cpp

   1 //===- LoopAnalysisManager.cpp - Loop analysis management -----------------===//
   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/LoopAnalysisManager.h"
  10 #include "llvm/Analysis/AssumptionCache.h"
  11 #include "llvm/Analysis/LoopInfo.h"
  12 #include "llvm/Analysis/MemorySSA.h"
  13 #include "llvm/Analysis/ScalarEvolution.h"
  14 #include "llvm/IR/Dominators.h"
  15 #include "llvm/IR/PassManagerImpl.h"
  16 #include <optional>
  17
  18 using namespace llvm;
  19
  20 namespace llvm {
  21 // Explicit template instantiations and specialization definitions for core
  22 // template typedefs.
  23 template class AllAnalysesOn<Loop>;
  24 template class AnalysisManager<Loop, LoopStandardAnalysisResults &>;
  25 template class InnerAnalysisManagerProxy<LoopAnalysisManager, Function>;
  26 template class OuterAnalysisManagerProxy<FunctionAnalysisManager, Loop,
  27                                          LoopStandardAnalysisResults &>;
  28
  29 bool LoopAnalysisManagerFunctionProxy::Result::invalidate(
  30     Function &F, const PreservedAnalyses &PA,
  31     FunctionAnalysisManager::Invalidator &Inv) {
  32   // First compute the sequence of IR units covered by this proxy. We will want
  33   // to visit this in postorder, but because this is a tree structure we can do
  34   // this by building a preorder sequence and walking it backwards. We also
  35   // want siblings in forward program order to match the LoopPassManager so we
  36   // get the preorder with siblings reversed.
  37   SmallVector<Loop *, 4> PreOrderLoops = LI->getLoopsInReverseSiblingPreorder();
  38
  39   // If this proxy or the loop info is going to be invalidated, we also need
  40   // to clear all the keys coming from that analysis. We also completely blow
  41   // away the loop analyses if any of the standard analyses provided by the
  42   // loop pass manager go away so that loop analyses can freely use these
  43   // without worrying about declaring dependencies on them etc.
  44   // FIXME: It isn't clear if this is the right tradeoff. We could instead make
  45   // loop analyses declare any dependencies on these and use the more general
  46   // invalidation logic below to act on that.
  47   auto PAC = PA.getChecker<LoopAnalysisManagerFunctionProxy>();
  48   bool invalidateMemorySSAAnalysis = false;
  49   if (MSSAUsed)
  50     invalidateMemorySSAAnalysis = Inv.invalidate<MemorySSAAnalysis>(F, PA);
  51   if (!(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>()) ||
  52       Inv.invalidate<AAManager>(F, PA) ||
  53       Inv.invalidate<AssumptionAnalysis>(F, PA) ||
  54       Inv.invalidate<DominatorTreeAnalysis>(F, PA) ||
  55       Inv.invalidate<LoopAnalysis>(F, PA) ||
  56       Inv.invalidate<ScalarEvolutionAnalysis>(F, PA) ||
  57       invalidateMemorySSAAnalysis) {
  58     // Note that the LoopInfo may be stale at this point, however the loop
  59     // objects themselves remain the only viable keys that could be in the
  60     // analysis manager's cache. So we just walk the keys and forcibly clear
  61     // those results. Note that the order doesn't matter here as this will just
  62     // directly destroy the results without calling methods on them.
  63     for (Loop *L : PreOrderLoops) {
  64       // NB! `L` may not be in a good enough state to run Loop::getName.
  65       InnerAM->clear(*L, "<possibly invalidated loop>");
  66     }
  67
  68     // We also need to null out the inner AM so that when the object gets
  69     // destroyed as invalid we don't try to clear the inner AM again. At that
  70     // point we won't be able to reliably walk the loops for this function and
  71     // only clear results associated with those loops the way we do here.
  72     // FIXME: Making InnerAM null at this point isn't very nice. Most analyses
  73     // try to remain valid during invalidation. Maybe we should add an
  74     // `IsClean` flag?
  75     InnerAM = nullptr;
  76
  77     // Now return true to indicate this *is* invalid and a fresh proxy result
  78     // needs to be built. This is especially important given the null InnerAM.
  79     return true;
  80   }
  81
  82   // Directly check if the relevant set is preserved so we can short circuit
  83   // invalidating loops.
  84   bool AreLoopAnalysesPreserved =
  85       PA.allAnalysesInSetPreserved<AllAnalysesOn<Loop>>();
  86
  87   // Since we have a valid LoopInfo we can actually leave the cached results in
  88   // the analysis manager associated with the Loop keys, but we need to
  89   // propagate any necessary invalidation logic into them. We'd like to
  90   // invalidate things in roughly the same order as they were put into the
  91   // cache and so we walk the preorder list in reverse to form a valid
  92   // postorder.
  93   for (Loop *L : reverse(PreOrderLoops)) {
  94     std::optional<PreservedAnalyses> InnerPA;
  95
  96     // Check to see whether the preserved set needs to be adjusted based on
  97     // function-level analysis invalidation triggering deferred invalidation
  98     // for this loop.
  99     if (auto *OuterProxy =
 100             InnerAM->getCachedResult<FunctionAnalysisManagerLoopProxy>(*L))
 101       for (const auto &OuterInvalidationPair :
 102            OuterProxy->getOuterInvalidations()) {
 103         AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
 104         const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
 105         if (Inv.invalidate(OuterAnalysisID, F, PA)) {
 106           if (!InnerPA)
 107             InnerPA = PA;
 108           for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
 109             InnerPA->abandon(InnerAnalysisID);
 110         }
 111       }
 112
 113     // Check if we needed a custom PA set. If so we'll need to run the inner
 114     // invalidation.
 115     if (InnerPA) {
 116       InnerAM->invalidate(*L, *InnerPA);
 117       continue;
 118     }
 119
 120     // Otherwise we only need to do invalidation if the original PA set didn't
 121     // preserve all Loop analyses.
 122     if (!AreLoopAnalysesPreserved)
 123       InnerAM->invalidate(*L, PA);
 124   }
 125
 126   // Return false to indicate that this result is still a valid proxy.
 127   return false;
 128 }
 129
 130 template <>
 131 LoopAnalysisManagerFunctionProxy::Result
 132 LoopAnalysisManagerFunctionProxy::run(Function &F,
 133                                       FunctionAnalysisManager &AM) {
 134   return Result(*InnerAM, AM.getResult<LoopAnalysis>(F));
 135 }
 136 } // namespace llvm
 137
 138 PreservedAnalyses llvm::getLoopPassPreservedAnalyses() {
 139   PreservedAnalyses PA;
 140   PA.preserve<DominatorTreeAnalysis>();
 141   PA.preserve<LoopAnalysis>();
 142   PA.preserve<LoopAnalysisManagerFunctionProxy>();
 143   PA.preserve<ScalarEvolutionAnalysis>();
 144   return PA;
 145 }