[PH] Replace uses of AssertingVH from members of analysis results with

a lazy-asserting PoisoningVH.

AssertVH is fundamentally incompatible with cache-invalidation of
analysis results. The invaliadtion happens after the AssertingVH has
already fired. Instead, use a PoisoningVH that will assert if the
dangling handle is ever used rather than merely be assigned or
destroyed.

This patch also removes all of the (numerous) doomed attempts to work
around this fundamental incompatibility. It is a pretty significant
simplification IMO.

The most interesting change is in the Inliner where we still do some
clearing because we don't want to rely on the coarse grained
invalidation strategy of the containing pass manager. However, I prefer
the approach that contains this logic to the cleanup phase of the
Inliner, and I think we could enhance the CGSCC analysis management
layer to make this even better in the future if desired.

The rest is straight cleanup.

I've also added a test for one of the harder cases to work around: when
a *module analysis* contains many AssertingVHes pointing at functions.

Differential Revision: https://reviews.llvm.org/D29006

llvm-svn: 292928

llvm/include/llvm/Analysis/CallGraph.h

@@ -272,7 +272,7 @@ class CallGraphNode {
 private:
   friend class CallGraph;
 
-  AssertingVH<Function> F;
+  Function *F;
 
   std::vector<CallRecord> CalledFunctions;
 

llvm/include/llvm/Analysis/ScalarEvolution.h

@@ -600,14 +600,14 @@ class ScalarEvolution {
   /// Information about the number of times a particular loop exit may be
   /// reached before exiting the loop.
   struct ExitNotTakenInfo {
-    AssertingVH<BasicBlock> ExitingBlock;
+    PoisoningVH<BasicBlock> ExitingBlock;
     const SCEV *ExactNotTaken;
     std::unique_ptr<SCEVUnionPredicate> Predicate;
     bool hasAlwaysTruePredicate() const {
       return !Predicate || Predicate->isAlwaysTrue();
     }
 
-    explicit ExitNotTakenInfo(AssertingVH<BasicBlock> ExitingBlock,
+    explicit ExitNotTakenInfo(PoisoningVH<BasicBlock> ExitingBlock,
                               const SCEV *ExactNotTaken,
                               std::unique_ptr<SCEVUnionPredicate> Predicate)
         : ExitingBlock(ExitingBlock), ExactNotTaken(ExactNotTaken),

llvm/lib/Analysis/LazyValueInfo.cpp

@@ -366,7 +366,7 @@ namespace {
     struct ValueCacheEntryTy {
       ValueCacheEntryTy(Value *V, LazyValueInfoCache *P) : Handle(V, P) {}
       LVIValueHandle Handle;
-      SmallDenseMap<AssertingVH<BasicBlock>, LVILatticeVal, 4> BlockVals;
+      SmallDenseMap<PoisoningVH<BasicBlock>, LVILatticeVal, 4> BlockVals;
     };
 
     /// This is all of the cached information for all values,
@@ -375,13 +375,13 @@ namespace {
 
     /// This tracks, on a per-block basis, the set of values that are
     /// over-defined at the end of that block.
-    typedef DenseMap<AssertingVH<BasicBlock>, SmallPtrSet<Value *, 4>>
+    typedef DenseMap<PoisoningVH<BasicBlock>, SmallPtrSet<Value *, 4>>
         OverDefinedCacheTy;
     OverDefinedCacheTy OverDefinedCache;
 
     /// Keep track of all blocks that we have ever seen, so we
     /// don't spend time removing unused blocks from our caches.
-    DenseSet<AssertingVH<BasicBlock> > SeenBlocks;
+    DenseSet<PoisoningVH<BasicBlock> > SeenBlocks;
 
   public:
     void insertResult(Value *Val, BasicBlock *BB, const LVILatticeVal &Result) {
@@ -464,10 +464,10 @@ void LazyValueInfoCache::eraseValue(Value *V) {
     SmallPtrSetImpl<Value *> &ValueSet = I.second;
     ValueSet.erase(V);
     if (ValueSet.empty())
-      ToErase.push_back(I.first);
+      ToErase.push_back(&*I.first);
   }
   for (auto &BB : ToErase)
-    OverDefinedCache.erase(BB);
+    OverDefinedCache.erase(&*BB);
 
   ValueCache.erase(V);
 }
@@ -480,7 +480,7 @@ void LVIValueHandle::deleted() {
 
 void LazyValueInfoCache::eraseBlock(BasicBlock *BB) {
   // Shortcut if we have never seen this block.
-  DenseSet<AssertingVH<BasicBlock> >::iterator I = SeenBlocks.find(BB);
+  DenseSet<PoisoningVH<BasicBlock> >::iterator I = SeenBlocks.find(BB);
   if (I == SeenBlocks.end())
     return;
   SeenBlocks.erase(I);

llvm/lib/Transforms/IPO/FunctionAttrs.cpp

@@ -1275,16 +1275,9 @@ PreservedAnalyses
 ReversePostOrderFunctionAttrsPass::run(Module &M, ModuleAnalysisManager &AM) {
   auto &CG = AM.getResult<CallGraphAnalysis>(M);
 
-  bool Changed = deduceFunctionAttributeInRPO(M, CG);
-
-  // CallGraphAnalysis holds AssertingVH and must be invalidated eagerly so
-  // that other passes don't delete stuff from under it.
-  // FIXME: We need to invalidate this to avoid PR28400. Is there a better
-  // solution?
-  AM.invalidate<CallGraphAnalysis>(M);
-
-  if (!Changed)
+  if (!deduceFunctionAttributeInRPO(M, CG))
     return PreservedAnalyses::all();
+
   PreservedAnalyses PA;
   PA.preserve<CallGraphAnalysis>();
   return PA;

llvm/lib/Transforms/IPO/GlobalDCE.cpp

@@ -144,29 +144,13 @@ PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) {
       }
     }
 
-  // Because we may have cached analyses for functions we take extra care when
-  // deleting them if there is an active proxy. If there isn't, then we get to
-  // assume that everything in the function AM has been cleared already.
-  // FIXME: Note that all of this will happen automatically when this pass
-  // finishes. Unfortuantely there are analyses which hold asserting VHs to
-  // IR units. We could make those weak VHs that would assert if ever used
-  // without asserting eagerly and then all of this knowledge of the analysis
-  // manager could go away.
-  FunctionAnalysisManager *FAM = nullptr;
-  if (auto *FAMProxy =
-          MAM.getCachedResult<FunctionAnalysisManagerModuleProxy>(M))
-    FAM = &FAMProxy->getManager();
-
   // The second pass drops the bodies of functions which are dead...
   std::vector<Function *> DeadFunctions;
   for (Function &F : M)
     if (!AliveGlobals.count(&F)) {
       DeadFunctions.push_back(&F);         // Keep track of dead globals
-      if (!F.isDeclaration()) {
-        if (FAM)
-          FAM->clear(F);
+      if (!F.isDeclaration())
         F.deleteBody();
-      }
     }
 
   // The third pass drops targets of aliases which are dead...

llvm/lib/Transforms/IPO/Inliner.cpp

@@ -887,11 +887,10 @@ PreservedAnalyses InlinerPass::run(LazyCallGraph::SCC &InitialC,
         // made dead by this operation on other functions).
         Callee.removeDeadConstantUsers();
         if (Callee.use_empty()) {
-          // Clear all analyses and the body and queue the function itself for
-          // deletion when we finish inlining and call graph updates.
+          // Clear the body and queue the function itself for deletion when we
+          // finish inlining and call graph updates.
           // Note that after this point, it is an error to do anything other
           // than use the callee's address or delete it.
-          FAM.clear(Callee);
           Callee.dropAllReferences();
           assert(find(DeadFunctions, &Callee) == DeadFunctions.end() &&
                  "Cannot put cause a function to become dead twice!");
@@ -939,8 +938,13 @@ PreservedAnalyses InlinerPass::run(LazyCallGraph::SCC &InitialC,
   // sets.
   for (Function *DeadF : DeadFunctions) {
     // Get the necessary information out of the call graph and nuke the
-    // function there.
+    // function there. Also, cclear out any cached analyses.
     auto &DeadC = *CG.lookupSCC(*CG.lookup(*DeadF));
+    FunctionAnalysisManager &FAM =
+        AM.getResult<FunctionAnalysisManagerCGSCCProxy>(DeadC, CG)
+            .getManager();
+    FAM.clear(*DeadF);
+    AM.clear(DeadC);
     auto &DeadRC = DeadC.getOuterRefSCC();
     CG.removeDeadFunction(*DeadF);
 

llvm/lib/Transforms/Scalar/AlignmentFromAssumptions.cpp

@@ -438,13 +438,7 @@ AlignmentFromAssumptionsPass::run(Function &F, FunctionAnalysisManager &AM) {
   AssumptionCache &AC = AM.getResult<AssumptionAnalysis>(F);
   ScalarEvolution &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
   DominatorTree &DT = AM.getResult<DominatorTreeAnalysis>(F);
-  bool Changed = runImpl(F, AC, &SE, &DT);
-
-  // FIXME: We need to invalidate this to avoid PR28400. Is there a better
-  // solution?
-  AM.invalidate<ScalarEvolutionAnalysis>(F);
-
-  if (!Changed)
+  if (!runImpl(F, AC, &SE, &DT))
     return PreservedAnalyses::all();
 
   PreservedAnalyses PA;

llvm/lib/Transforms/Scalar/NaryReassociate.cpp

@@ -156,13 +156,7 @@ PreservedAnalyses NaryReassociatePass::run(Function &F,
   auto *TLI = &AM.getResult<TargetLibraryAnalysis>(F);
   auto *TTI = &AM.getResult<TargetIRAnalysis>(F);
 
-  bool Changed = runImpl(F, AC, DT, SE, TLI, TTI);
-
-  // FIXME: We need to invalidate this to avoid PR28400. Is there a better
-  // solution?
-  AM.invalidate<ScalarEvolutionAnalysis>(F);
-
-  if (!Changed)
+  if (!runImpl(F, AC, DT, SE, TLI, TTI))
     return PreservedAnalyses::all();
 
   PreservedAnalyses PA;

llvm/lib/Transforms/Utils/LoopSimplify.cpp

@@ -853,12 +853,9 @@ PreservedAnalyses LoopSimplifyPass::run(Function &F,
   for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
     Changed |= simplifyLoop(*I, DT, LI, SE, AC, /*PreserveLCSSA*/ false);
 
-  // FIXME: We need to invalidate this to avoid PR28400. Is there a better
-  // solution?
-  AM.invalidate<ScalarEvolutionAnalysis>(F);
-
   if (!Changed)
     return PreservedAnalyses::all();
+
   PreservedAnalyses PA;
   PA.preserve<DominatorTreeAnalysis>();
   PA.preserve<LoopAnalysis>();

llvm/test/Other/new-pm-defaults.ll

@@ -91,8 +91,6 @@
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LoopStandardAnalysisResults{{.*}}>
-; CHECK-O-NEXT: Invalidating analysis: ScalarEvolutionAnalysis
-; CHECK-O-NEXT: Running analysis: ScalarEvolutionAnalysis
 ; CHECK-O-NEXT: Starting Loop pass manager run.
 ; CHECK-O-NEXT: Finished Loop pass manager run.
 ; CHECK-Os-NEXT: Running pass: MergedLoadStoreMotionPass
@@ -120,7 +118,6 @@
 ; CHECK-O-NEXT: Running pass: EliminateAvailableExternallyPass
 ; CHECK-O-NEXT: Running pass: ReversePostOrderFunctionAttrsPass
 ; CHECK-O-NEXT: Running analysis: CallGraphAnalysis
-; CHECK-O-NEXT: Invalidating analysis: CallGraphAnalysis
 ; CHECK-O-NEXT: Running pass: ModuleToFunctionPassAdaptor<{{.*}}PassManager{{.*}}>
 ; CHECK-O-NEXT: Starting llvm::Function pass manager run.
 ; CHECK-O-NEXT: Running pass: Float2IntPass
@@ -133,7 +130,6 @@
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O-NEXT: Running pass: AlignmentFromAssumptionsPass
-; CHECK-O-NEXT: Invalidating analysis: ScalarEvolutionAnalysis
 ; CHECK-O-NEXT: Finished llvm::Function pass manager run.
 ; CHECK-O-NEXT: Running pass: GlobalDCEPass
 ; CHECK-O-NEXT: Running pass: ConstantMergePass

llvm/test/Other/new-pm-lto-defaults.ll

@@ -37,7 +37,6 @@
 ; CHECK-O-NEXT: Running analysis: TargetLibraryAnalysis
 ; CHECK-O-NEXT: Running pass: ReversePostOrderFunctionAttrsPass
 ; CHECK-O-NEXT: Running analysis: CallGraphAnalysis
-; CHECK-O-NEXT: Invalidating analysis: CallGraphAnalysis
 ; CHECK-O-NEXT: Running pass: GlobalSplitPass
 ; CHECK-O-NEXT: Running pass: WholeProgramDevirtPass
 ; CHECK-O2-NEXT: Running pass: GlobalOptPass

llvm/test/Transforms/GlobalDCE/crash-assertingvh.ll

@@ -3,6 +3,7 @@
 ; to assert when global DCE deletes the body of the function.
 ;
 ; RUN: opt -disable-output < %s -passes='module(function(jump-threading),globaldce)'
+; RUN: opt -disable-output < %s -passes='module(rpo-functionattrs,globaldce)'
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"

llvm/test/Transforms/Inline/clear-analyses.ll

@@ -1,8 +1,7 @@
-; Test that the inliner clears analyses which may hold references to function
-; bodies when it decides to delete them after inlining the last caller.
-; We check this by using correlated-propagation to populate LVI with basic
-; block references that would dangle if we failed to clear the inlined function
-; body.
+; Test that when a pass like correlated-propagation populates an analysis such
+; as LVI with references back into the IR of a function that the inliner will
+; delete, this doesn't crash or go awry despite the inliner clearing the analyses
+; separately from when it deletes the function.
 ;
 ; RUN: opt -debug-pass-manager -S < %s 2>&1 \
 ; RUN:     -passes='cgscc(inline,function(correlated-propagation))' \