Index: lib/Transforms/IPO/SampleProfile.cpp
===================================================================
--- lib/Transforms/IPO/SampleProfile.cpp
+++ lib/Transforms/IPO/SampleProfile.cpp
@@ -812,23 +812,31 @@
     // edge is unknown (see setEdgeOrBlockWeight).
     for (unsigned i = 0; i < 2; i++) {
       uint64_t TotalWeight = 0;
-      unsigned NumUnknownEdges = 0;
-      Edge UnknownEdge, SelfReferentialEdge;
+      unsigned NumUnknownEdges = 0, NumTotalEdges = 0;
+      Edge UnknownEdge, SelfReferentialEdge, SingleEdge;
 
       if (i == 0) {
         // First, visit all predecessor edges.
+        NumTotalEdges = Predecessors[BB].size();
         for (auto *Pred : Predecessors[BB]) {
           Edge E = std::make_pair(Pred, BB);
           TotalWeight += visitEdge(E, &NumUnknownEdges, &UnknownEdge);
           if (E.first == E.second)
             SelfReferentialEdge = E;
         }
+        if (NumTotalEdges == 1) {
+          SingleEdge = std::make_pair(Predecessors[BB][0], BB);
+        }
       } else {
         // On the second round, visit all successor edges.
+        NumTotalEdges = Successors[BB].size();
         for (auto *Succ : Successors[BB]) {
           Edge E = std::make_pair(BB, Succ);
           TotalWeight += visitEdge(E, &NumUnknownEdges, &UnknownEdge);
         }
+        if (NumTotalEdges == 1) {
+          SingleEdge = std::make_pair(BB, Successors[BB][0]);
+        }
       }
 
       // After visiting all the edges, there are three cases that we
@@ -857,18 +865,24 @@
       if (NumUnknownEdges <= 1) {
         uint64_t &BBWeight = BlockWeights[EC];
         if (NumUnknownEdges == 0) {
-          // If we already know the weight of all edges, the weight of the
-          // basic block can be computed. It should be no larger than the sum
-          // of all edge weights.
-          if (TotalWeight > BBWeight) {
-            BBWeight = TotalWeight;
+          if (!VisitedBlocks.count(EC)) {
+            // If we already know the weight of all edges, the weight of the
+            // basic block can be computed. It should be no larger than the sum
+            // of all edge weights.
+            if (TotalWeight > BBWeight) {
+              BBWeight = TotalWeight;
+              Changed = true;
+              DEBUG(dbgs() << "All edge weights for " << BB->getName()
+                           << " known. Set weight for block: ";
+                    printBlockWeight(dbgs(), BB););
+            }
+          } else if (NumTotalEdges == 1 &&
+                     EdgeWeights[SingleEdge] < BlockWeights[EC]) {
+            // If there is only one edge for the visited basic block, use the
+            // block weight to adjust edge weight if edge weight is smaller.
+            EdgeWeights[SingleEdge] = BlockWeights[EC];
             Changed = true;
-            DEBUG(dbgs() << "All edge weights for " << BB->getName()
-                         << " known. Set weight for block: ";
-                  printBlockWeight(dbgs(), BB););
           }
-          if (VisitedBlocks.insert(EC).second)
-            Changed = true;
         } else if (NumUnknownEdges == 1 && VisitedBlocks.count(EC)) {
           // If there is a single unknown edge and the block has been
           // visited, then we can compute E's weight.
Index: test/Transforms/SampleProfile/fnptr.ll
===================================================================
--- test/Transforms/SampleProfile/fnptr.ll
+++ test/Transforms/SampleProfile/fnptr.ll
@@ -10,10 +10,10 @@
 
 ; CHECK:   edge for.body3 -> if.then probability is 0x1a4f3959 / 0x80000000 = 20.55%
 ; CHECK:   edge for.body3 -> if.else probability is 0x65b0c6a7 / 0x80000000 = 79.45%
-; CHECK:   edge for.inc -> for.inc12 probability is 0x33d4a4c1 / 0x80000000 = 40.49%
-; CHECK:   edge for.inc -> for.body3 probability is 0x4c2b5b3f / 0x80000000 = 59.51%
-; CHECK:   edge for.inc12 -> for.end14 probability is 0x3f06d04e / 0x80000000 = 49.24%
-; CHECK:   edge for.inc12 -> for.cond1.preheader probability is 0x40f92fb2 / 0x80000000 = 50.76%
+; CHECK:   edge for.inc -> for.inc12 probability is 0x20dc8dc9 / 0x80000000 = 25.67%
+; CHECK:   edge for.inc -> for.body3 probability is 0x5f237237 / 0x80000000 = 74.33%
+; CHECK:   edge for.inc12 -> for.end14 probability is 0x00000000 / 0x80000000 = 0.00%
+; CHECK:   edge for.inc12 -> for.cond1.preheader probability is 0x80000000 / 0x80000000 = 100.00%
 
 ; Original C++ test case.
 ;