Never insert duplicate edges.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41169 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/PredicateSimplifier.cpp b/lib/Transforms/Scalar/PredicateSimplifier.cpp
index 972e875d4b0d04307b652eed3e4b1af836e4343a..e27bac50d7a1b73bc6cebcfd0d4c2a2c593b5cca 100644 (file)
--- a/lib/Transforms/Scalar/PredicateSimplifier.cpp
+++ b/lib/Transforms/Scalar/PredicateSimplifier.cpp
@@ -711,23 +711,27 @@ namespace {
           ++J;
         }
 
-        if (J != E && J->To == n && J->Subtree->dominates(Subtree)) {
+        if (J != E && J->To == n) {
+          assert(J->Subtree->dominates(Subtree));
+
           edge.LV = static_cast<LatticeVal>(J->LV & R);
           assert(validPredicate(edge.LV) && "Invalid union of lattice values.");
-          if (edge.LV != J->LV) {
-
-            // We have to tighten any edge beneath our update.
-            for (iterator K = I; K->To == n; --K) {
-              if (K->Subtree->DominatedBy(Subtree)) {
-                LatticeVal LV = static_cast<LatticeVal>(K->LV & edge.LV);
-                assert(validPredicate(LV) && "Invalid union of lattice values");
-                K->LV = LV;
-              }
-              if (K == B) break;
-            }
 
+          if (edge.LV == J->LV)
+            return; // This update adds nothing new.
+       }
+
+        if (I != B) {
+          // We also have to tighten any edge beneath our update.
+          for (iterator K = I - 1; K->To == n; --K) {
+            if (K->Subtree->DominatedBy(Subtree)) {
+              LatticeVal LV = static_cast<LatticeVal>(K->LV & edge.LV);
+              assert(validPredicate(LV) && "Invalid union of lattice values");
+              K->LV = LV;
+            }
+            if (K == B) break;
           }
-        }
+       }
 
         // Insert new edge at Subtree if it isn't already there.
         if (I == E || I->To != n || Subtree != I->Subtree)