[Polly][PM] Improve invalidation in the Scop-Pipeline

Summary:
During code generation for a Scop we modify the IR of a function.
While this shouldn't affect a Scop in the formal sense, the implementation
caches various information about the IR such as SCEV expressions for bounds or
parameters. This cached information needs to be updated or invalidated. To this
end, SPMUpdater allows passes to report when they've invalidated a Scop to the
PassManager, which will then flush and recompute all Scops. This in turn
invalidates all iterators, so references to Scops shouldn't be held.

Reviewers: grosser, Meinersbur, bollu

Reviewed By: grosser

Subscribers: llvm-commits, pollydev

Differential Revision: https://reviews.llvm.org/D36524

llvm-svn: 310551

polly/include/polly/ScopInfo.h

@@ -3044,6 +3044,13 @@ private:
   /// A map of Region to its Scop object containing
   ///        Polly IR of static control part.
   RegionToScopMapTy RegionToScopMap;
+  const DataLayout &DL;
+  ScopDetection &SD;
+  ScalarEvolution &SE;
+  LoopInfo &LI;
+  AliasAnalysis &AA;
+  DominatorTree &DT;
+  AssumptionCache ∾
 
 public:
   ScopInfo(const DataLayout &DL, ScopDetection &SD, ScalarEvolution &SE,
@@ -3063,6 +3070,15 @@ public:
     return nullptr;
   }
 
+  /// Recompute the Scop-Information for a function.
+  ///
+  /// This invalidates any iterators.
+  void recompute();
+
+  /// Handle invalidation explicitly
+  bool invalidate(Function &F, const PreservedAnalyses &PA,
+                  FunctionAnalysisManager::Invalidator &Inv);
+
   iterator begin() { return RegionToScopMap.begin(); }
   iterator end() { return RegionToScopMap.end(); }
   const_iterator begin() const { return RegionToScopMap.begin(); }

polly/include/polly/ScopPass.h

@@ -180,18 +180,26 @@ struct ScopStandardAnalysisResults {
 
 class SPMUpdater {
 public:
-  SPMUpdater(SmallPriorityWorklist<Scop *, 4> &Worklist,
+  SPMUpdater(SmallPriorityWorklist<Region *, 4> &Worklist,
              ScopAnalysisManager &SAM)
-      : Worklist(Worklist), SAM(SAM) {}
+      : Worklist(Worklist), SAM(SAM), InvalidateCurrentScop(false) {}
 
-  void SkipScop(Scop &S) {
-    if (Worklist.erase(&S))
-      SAM.clear(S);
+  bool invalidateCurrentScop() const { return InvalidateCurrentScop; }
+
+  void invalidateScop(Scop &S) {
+    if (&S == CurrentScop)
+      InvalidateCurrentScop = true;
+
+    Worklist.erase(&S.getRegion());
+    SAM.clear(S);
   }
 
 private:
-  SmallPriorityWorklist<Scop *, 4> &Worklist;
+  Scop *CurrentScop;
+  bool InvalidateCurrentScop;
+  SmallPriorityWorklist<Region *, 4> &Worklist;
   ScopAnalysisManager &SAM;
+  template <typename ScopPassT> friend class FunctionToScopPassAdaptor;
 };
 
 template <typename ScopPassT>
@@ -202,10 +210,16 @@ public:
 
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM) {
     PreservedAnalyses PA = PreservedAnalyses::all();
-    auto &Scops = AM.getResult<ScopInfoAnalysis>(F);
-    if (Scops.empty())
+    auto &SD = AM.getResult<ScopAnalysis>(F);
+    auto &SI = AM.getResult<ScopInfoAnalysis>(F);
+    if (SI.empty())
       return PA;
 
+    SmallPriorityWorklist<Region *, 4> Worklist;
+    for (auto &S : SI)
+      if (S.second)
+        Worklist.insert(S.first);
+
     ScopStandardAnalysisResults AR = {AM.getResult<DominatorTreeAnalysis>(F),
                                       AM.getResult<ScopInfoAnalysis>(F),
                                       AM.getResult<ScalarEvolutionAnalysis>(F),
@@ -215,19 +229,23 @@ public:
     ScopAnalysisManager &SAM =
         AM.getResult<ScopAnalysisManagerFunctionProxy>(F).getManager();
 
-    SmallPriorityWorklist<Scop *, 4> Worklist;
     SPMUpdater Updater{Worklist, SAM};
 
-    for (auto &S : Scops)
-      if (auto *scop = S.second.get())
-        Worklist.insert(scop);
-
     while (!Worklist.empty()) {
-      Scop *scop = Worklist.pop_back_val();
+      Region *R = Worklist.pop_back_val();
+      if (!SD.isMaxRegionInScop(*R))
+        continue;
+      Scop *scop = SI.getScop(R);
+      if (!scop)
+        continue;
+      Updater.CurrentScop = scop;
+      Updater.InvalidateCurrentScop = false;
       PreservedAnalyses PassPA = Pass.run(*scop, SAM, AR, Updater);
 
       SAM.invalidate(*scop, PassPA);
       PA.intersect(std::move(PassPA));
+      if (Updater.invalidateCurrentScop())
+        SI.recompute();
     };
 
     PA.preserveSet<AllAnalysesOn<Scop>>();

polly/lib/Analysis/ScopInfo.cpp

@@ -5227,7 +5227,13 @@ INITIALIZE_PASS_END(ScopInfoRegionPass, "polly-scops",
 //===----------------------------------------------------------------------===//
 ScopInfo::ScopInfo(const DataLayout &DL, ScopDetection &SD, ScalarEvolution &SE,
                    LoopInfo &LI, AliasAnalysis &AA, DominatorTree &DT,
-                   AssumptionCache &AC) {
+                   AssumptionCache &AC)
+    : DL(DL), SD(SD), SE(SE), LI(LI), AA(AA), DT(DT), AC(AC) {
+  recompute();
+}
+
+void ScopInfo::recompute() {
+  RegionToScopMap.clear();
   /// Create polyhedral description of scops for all the valid regions of a
   /// function.
   for (auto &It : SD) {
@@ -5248,6 +5254,20 @@ ScopInfo::ScopInfo(const DataLayout &DL, ScopDetection &SD, ScalarEvolution &SE,
   }
 }
 
+bool ScopInfo::invalidate(Function &F, const PreservedAnalyses &PA,
+                          FunctionAnalysisManager::Invalidator &Inv) {
+  // Check whether the analysis, all analyses on functions have been preserved
+  // or anything we're holding references to is being invalidated
+  auto PAC = PA.getChecker<ScopInfoAnalysis>();
+  return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>()) ||
+         Inv.invalidate<ScopAnalysis>(F, PA) ||
+         Inv.invalidate<ScalarEvolutionAnalysis>(F, PA) ||
+         Inv.invalidate<LoopAnalysis>(F, PA) ||
+         Inv.invalidate<AAManager>(F, PA) ||
+         Inv.invalidate<DominatorTreeAnalysis>(F, PA) ||
+         Inv.invalidate<AssumptionAnalysis>(F, PA);
+}
+
 AnalysisKey ScopInfoAnalysis::Key;
 
 ScopInfoAnalysis::Result ScopInfoAnalysis::run(Function &F,

polly/lib/Analysis/ScopPass.cpp

@@ -79,11 +79,11 @@ bool ScopAnalysisManagerFunctionProxy::Result::invalidate(
 
   // First, check whether our ScopInfo is about to be invalidated
   auto PAC = PA.getChecker<ScopAnalysisManagerFunctionProxy>();
-  if (!(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
-        Inv.invalidate<ScopInfoAnalysis>(F, PA) ||
-        Inv.invalidate<ScalarEvolutionAnalysis>(F, PA) ||
-        Inv.invalidate<LoopAnalysis>(F, PA) ||
-        Inv.invalidate<DominatorTreeAnalysis>(F, PA))) {
+  if (!(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>()) ||
+      Inv.invalidate<ScopInfoAnalysis>(F, PA) ||
+      Inv.invalidate<ScalarEvolutionAnalysis>(F, PA) ||
+      Inv.invalidate<LoopAnalysis>(F, PA) ||
+      Inv.invalidate<DominatorTreeAnalysis>(F, PA)) {
 
     // As everything depends on ScopInfo, we must drop all existing results
     for (auto &S : *SI)

polly/lib/CodeGen/CodeGeneration.cpp

@@ -328,8 +328,10 @@ PreservedAnalyses
 polly::CodeGenerationPass::run(Scop &S, ScopAnalysisManager &SAM,
                                ScopStandardAnalysisResults &AR, SPMUpdater &U) {
   auto &AI = SAM.getResult<IslAstAnalysis>(S, AR);
-  if (CodeGen(S, AI, AR.LI, AR.DT, AR.SE, AR.RI))
+  if (CodeGen(S, AI, AR.LI, AR.DT, AR.SE, AR.RI)) {
+    U.invalidateScop(S);
     return PreservedAnalyses::none();
+  }
 
   return PreservedAnalyses::all();
 }