Fix ndebug-build unused variable in loop rerolling

llvm-svn: 194941

Author: Hal Finkel

llvm/lib/Transforms/Scalar/LoopRerollPass.cpp

@@ -276,7 +276,7 @@ namespace {
           int Idx = PossibleRedIdx[J1];
           assert(Idx == PossibleRedIdx[J2] &&
                  "Recording pair from different reductions?");
-          Reds.insert(PossibleRedIdx[J1]);
+          Reds.insert(Idx);
         }
       }