[Dominators] Visit affected node candidates found at different root levels

kuhar · kuhar · commit d2e371f046c5 · 2018-01-19T21:27:24.000Z
Summary: This patch attempts to fix the DomTree incremental insertion bug found here [[ https://bugs.llvm.org/show_bug.cgi?id=35969 | PR35969 ]] . When performing an insertion into a piece of unreachable CFG, we may find the same not at different levels. When this happens, the node can turn out to be affected when we find it starting from a node with a lower level in the tree. The level at which we start visitation affects if we consider a node affected or not. This patch tracks the lowest level at which each node was visited during insertion and allows it to be visited multiple times, if it can cause it to be considered affected. Reviewers: brzycki, davide, dberlin, grosser Reviewed By: brzycki Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D42231 llvm-svn: 322993
diff --git a/llvm/include/llvm/Support/GenericDomTreeConstruction.h b/llvm/include/llvm/Support/GenericDomTreeConstruction.h
@@ -628,7 +628,7 @@ struct SemiNCAInfo {
         DecreasingLevel>
         Bucket;  // Queue of tree nodes sorted by level in descending order.
     SmallDenseSet<TreeNodePtr, 8> Affected;
-    SmallDenseSet<TreeNodePtr, 8> Visited;
+    SmallDenseMap<TreeNodePtr, unsigned, 8> Visited;
     SmallVector<TreeNodePtr, 8> AffectedQueue;
     SmallVector<TreeNodePtr, 8> VisitedNotAffectedQueue;
   };
@@ -753,14 +753,16 @@ struct SemiNCAInfo {
 
     while (!II.Bucket.empty()) {
       const TreeNodePtr CurrentNode = II.Bucket.top().second;
+      const unsigned  CurrentLevel = CurrentNode->getLevel();
       II.Bucket.pop();
       DEBUG(dbgs() << "\tAdding to Visited and AffectedQueue: "
                    << BlockNamePrinter(CurrentNode) << "\n");
-      II.Visited.insert(CurrentNode);
+
+      II.Visited.insert({CurrentNode, CurrentLevel});
       II.AffectedQueue.push_back(CurrentNode);
 
       // Discover and collect affected successors of the current node.
-      VisitInsertion(DT, BUI, CurrentNode, CurrentNode->getLevel(), NCD, II);
+      VisitInsertion(DT, BUI, CurrentNode, CurrentLevel, NCD, II);
     }
 
     // Finish by updating immediate dominators and levels.
@@ -772,33 +774,49 @@ struct SemiNCAInfo {
                              const TreeNodePtr TN, const unsigned RootLevel,
                              const TreeNodePtr NCD, InsertionInfo &II) {
     const unsigned NCDLevel = NCD->getLevel();
-    DEBUG(dbgs() << "Visiting " << BlockNamePrinter(TN) << "\n");
+    DEBUG(dbgs() << "Visiting " << BlockNamePrinter(TN) << ",  RootLevel "
+                 << RootLevel << "\n");
 
     SmallVector<TreeNodePtr, 8> Stack = {TN};
     assert(TN->getBlock() && II.Visited.count(TN) && "Preconditions!");
 
+    SmallPtrSet<TreeNodePtr, 8> Processed;
+
     do {
       TreeNodePtr Next = Stack.pop_back_val();
+      DEBUG(dbgs() << " Next: " << BlockNamePrinter(Next) << "\n");
 
       for (const NodePtr Succ :
            ChildrenGetter<IsPostDom>::Get(Next->getBlock(), BUI)) {
         const TreeNodePtr SuccTN = DT.getNode(Succ);
         assert(SuccTN && "Unreachable successor found at reachable insertion");
         const unsigned SuccLevel = SuccTN->getLevel();
 
-        DEBUG(dbgs() << "\tSuccessor " << BlockNamePrinter(Succ)
-                     << ", level = " << SuccLevel << "\n");
+        DEBUG(dbgs() << "\tSuccessor " << BlockNamePrinter(Succ) << ", level = "
+                     << SuccLevel << "\n");
+
+        // Do not process the same node multiple times.
+        if (Processed.count(Next) > 0)
+          continue;
 
         // Succ dominated by subtree From -- not affected.
         // (Based on the lemma 2.5 from the second paper.)
         if (SuccLevel > RootLevel) {
           DEBUG(dbgs() << "\t\tDominated by subtree From\n");
-          if (II.Visited.count(SuccTN) != 0)
-            continue;
+          if (II.Visited.count(SuccTN) != 0) {
+            DEBUG(dbgs() << "\t\t\talready visited at level "
+                         << II.Visited[SuccTN] << "\n\t\t\tcurrent level "
+                         << RootLevel << ")\n");
+
+            // A node can be necessary to visit again if we see it again at
+            // a lower level than before.
+            if (II.Visited[SuccTN] >= RootLevel)
+              continue;
+          }
 
           DEBUG(dbgs() << "\t\tMarking visited not affected "
                        << BlockNamePrinter(Succ) << "\n");
-          II.Visited.insert(SuccTN);
+          II.Visited.insert({SuccTN, RootLevel});
           II.VisitedNotAffectedQueue.push_back(SuccTN);
           Stack.push_back(SuccTN);
         } else if ((SuccLevel > NCDLevel + 1) &&
@@ -809,6 +827,8 @@ struct SemiNCAInfo {
           II.Bucket.push({SuccLevel, SuccTN});
         }
       }
+
+      Processed.insert(Next);
     } while (!Stack.empty());
   }
 
diff --git a/llvm/test/Transforms/JumpThreading/ddt-crash3.ll b/llvm/test/Transforms/JumpThreading/ddt-crash3.ll
@@ -0,0 +1,43 @@
+; RUN: opt < %s -jump-threading -disable-output -verify-dom-info
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@global = external local_unnamed_addr global i64, align 8
+@global.1 = external local_unnamed_addr global i64, align 8
+@global.2 = external local_unnamed_addr global i64, align 8
+
+; Function Attrs: norecurse noreturn nounwind uwtable
+define void @hoge() local_unnamed_addr #0 {
+bb:
+  br label %bb1
+
+bb1:                                              ; preds = %bb26, %bb
+  %tmp = load i64, i64* @global, align 8, !tbaa !1
+  %tmp2 = icmp eq i64 %tmp, 0
+  br i1 %tmp2, label %bb27, label %bb3
+
+bb3:                                              ; preds = %bb1
+  %tmp4 = load i64, i64* @global.1, align 8, !tbaa !1
+  %tmp5 = icmp eq i64 %tmp4, 0
+  br i1 %tmp5, label %bb23, label %bb23
+
+bb23:                                             ; preds = %bb3, %bb3
+  br label %bb26
+
+bb26:                                             ; preds = %bb27, %bb23
+  br label %bb1
+
+bb27:                                             ; preds = %bb1
+  br label %bb26
+}
+
+attributes #0 = { norecurse noreturn nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.ident = !{!0}
+
+!0 = !{!"clang version 7.0.0 "}
+!1 = !{!2, !2, i64 0}
+!2 = !{!"long", !3, i64 0}
+!3 = !{!"omnipotent char", !4, i64 0}
+!4 = !{!"Simple C/C++ TBAA"}
diff --git a/llvm/test/Transforms/JumpThreading/ddt-crash4.ll b/llvm/test/Transforms/JumpThreading/ddt-crash4.ll
@@ -0,0 +1,75 @@
+; RUN: opt < %s -jump-threading -disable-output -verify-dom-info
+@global = external global i64, align 8
+
+define void @f() {
+bb:
+  br label %bb1
+
+bb1:
+  %tmp = load i64, i64* @global, align 8
+  %tmp2 = icmp eq i64 %tmp, 0
+  br i1 %tmp2, label %bb27, label %bb3
+
+bb3:
+  %tmp4 = load i64, i64* @global, align 8
+  %tmp5 = icmp eq i64 %tmp4, 0
+  br i1 %tmp5, label %bb6, label %bb7
+
+bb6:
+  br label %bb7
+
+bb7:
+  %tmp8 = phi i1 [ true, %bb3 ], [ undef, %bb6 ]
+  %tmp9 = select i1 %tmp8, i64 %tmp4, i64 0
+  br i1 false, label %bb10, label %bb23
+
+bb10:
+  %tmp11 = load i64, i64* @global, align 8
+  %tmp12 = icmp slt i64 %tmp11, 5
+  br i1 %tmp12, label %bb13, label %bb17
+
+bb13:
+  br label %bb14
+
+bb14:
+  br i1 undef, label %bb15, label %bb16
+
+bb15:
+  unreachable
+
+bb16:
+  br label %bb10
+
+bb17:
+  br label %bb18
+
+bb18:
+  br i1 undef, label %bb22, label %bb13
+
+bb19:
+  br i1 undef, label %bb20, label %bb21
+
+bb20:
+  unreachable
+
+bb21:
+  br label %bb18
+
+bb22:
+  br label %bb23
+
+bb23:
+  br i1 undef, label %bb24, label %bb13
+
+bb24:
+  br i1 undef, label %bb26, label %bb25
+
+bb25:
+  br label %bb19
+
+bb26:
+  br label %bb1
+
+bb27:
+  br label %bb24
+}
diff --git a/llvm/unittests/IR/DominatorTreeTest.cpp b/llvm/unittests/IR/DominatorTreeTest.cpp
@@ -925,3 +925,28 @@ TEST(DominatorTree, InsertDeleteExhaustive) {
     }
   }
 }
+
+TEST(DominatorTree, InsertIntoIrreducible) {
+  std::vector<CFGBuilder::Arc> Arcs = {
+      {"0", "1"},
+      {"1", "27"}, {"1", "7"},
+      {"10", "18"},
+      {"13", "10"},
+      {"18", "13"}, {"18", "23"},
+      {"23", "13"}, {"23", "24"},
+      {"24", "1"}, {"24", "18"},
+      {"27", "24"}};
+
+  CFGHolder Holder;
+  CFGBuilder B(Holder.F, Arcs, {{Insert, {"7", "23"}}});
+  DominatorTree DT(*Holder.F);
+  EXPECT_TRUE(DT.verify());
+
+  B.applyUpdate();
+  BasicBlock *From = B.getOrAddBlock("7");
+  BasicBlock *To = B.getOrAddBlock("23");
+  DT.insertEdge(From, To);
+
+  EXPECT_TRUE(DT.verify());
+}
+
