2 files changed, 14 insertions, 3 deletions
diff --git a/Eigen/src/Core/ProductEvaluators.h b/Eigen/src/Core/ProductEvaluators.h
index 792b1811c..6b32c508b 100644
--- a/Eigen/src/Core/ProductEvaluators.h
+++ b/Eigen/src/Core/ProductEvaluators.h
@@ -256,7 +256,7 @@ struct generic_product_impl<Lhs,Rhs,DenseShape,DenseShape,InnerProduct>
   {
     dst.coeffRef(0,0) += (lhs.transpose().cwiseProduct(rhs)).sum();
   }
-  
+
   template<typename Dst>
   static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void subTo(Dst& dst, const Lhs& lhs, const Rhs& rhs)
   { dst.coeffRef(0,0) -= (lhs.transpose().cwiseProduct(rhs)).sum(); }
@@ -375,6 +375,11 @@ struct generic_product_impl<Lhs,Rhs,DenseShape,DenseShape,GemvProduct>
   template<typename Dest>
   static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void scaleAndAddTo(Dest& dst, const Lhs& lhs, const Rhs& rhs, const Scalar& alpha)
   {
+    // Fallback to inner product if both the lhs and rhs is a runtime vector.
+    if (lhs.rows() == 1 && rhs.cols() == 1) {
+      dst.coeffRef(0,0) += alpha * (lhs.row(0).transpose().cwiseProduct(rhs.col(0)).sum());
+      return;
+    } 
     LhsNested actual_lhs(lhs);
     RhsNested actual_rhs(rhs);
     internal::gemv_dense_selector<Side,
diff --git a/Eigen/src/Core/products/GeneralMatrixMatrix.h b/Eigen/src/Core/products/GeneralMatrixMatrix.h
index 508c05c97..8cdf14702 100644
--- a/Eigen/src/Core/products/GeneralMatrixMatrix.h
+++ b/Eigen/src/Core/products/GeneralMatrixMatrix.h
@@ -471,15 +471,21 @@ struct generic_product_impl<Lhs,Rhs,DenseShape,DenseShape,GemmProduct>
     if(a_lhs.cols()==0 || a_lhs.rows()==0 || a_rhs.cols()==0)
       return;
 
-    // Fallback to GEMV if either the lhs or rhs is a runtime vector
-    if (dst.cols() == 1)
+    if (dst.cols() == 1 && dst.rows() == 1) {
+      // Fallback to inner product if both the lhs and rhs is a runtime vector.
+      dst.coeffRef(0,0) += alpha * (a_lhs.row(0).transpose().cwiseProduct(a_rhs.col(0)).sum());
+      return;
+    }
+    else if (dst.cols() == 1)
     {
+      // Fallback to GEMV if either the lhs or rhs is a runtime vector
       typename Dest::ColXpr dst_vec(dst.col(0));
       return internal::generic_product_impl<Lhs,typename Rhs::ConstColXpr,DenseShape,DenseShape,GemvProduct>
         ::scaleAndAddTo(dst_vec, a_lhs, a_rhs.col(0), alpha);
     }
     else if (dst.rows() == 1)
     {
+      // Fallback to GEMV if either the lhs or rhs is a runtime vector
       typename Dest::RowXpr dst_vec(dst.row(0));
       return internal::generic_product_impl<typename Lhs::ConstRowXpr,Rhs,DenseShape,DenseShape,GemvProduct>
         ::scaleAndAddTo(dst_vec, a_lhs.row(0), a_rhs, alpha);