Fix dst memory allocation in elementwise_add (#21059)

test=develop

paddle/fluid/operators/elementwise/mkldnn/elementwise_add_mkldnn_op.cc

@@ -43,7 +43,6 @@ class EltwiseAddMKLDNNKernel : public framework::OpKernel<T> {
     auto* z = ctx.Output<Tensor>("Out");
     const T* x_data = x->data<T>();
     const T* y_data = y->data<T>();
-    T* z_data = z->mutable_data<T>(ctx.GetPlace());
 
     int axis = ctx.Attr<int>("axis");
 
@@ -92,6 +91,7 @@ class EltwiseAddMKLDNNKernel : public framework::OpKernel<T> {
         _x.ShareDataWith(*x);
       }
 
+      z->mutable_data<T>(ctx.GetPlace());
       auto sum_func = [](T a, T b) -> T { return a + b; };
 
       TransformFunctor<decltype(sum_func), T,
@@ -155,6 +155,9 @@ class EltwiseAddMKLDNNKernel : public framework::OpKernel<T> {
       auto sum_pd = handler.AcquireSumPrimitiveDescriptor(
           {src_x_memory, src_y_memory}, scales, dst_md);
 
+      T* z_data = z->mutable_data<T>(ctx.GetPlace(),
+                                     sum_pd->dst_primitive_desc().get_size());
+
       auto dst_memory = handler.AcquireDstMemoryFromPrimitive(z_data);
 
       std::vector<primitive::at> inputs({*src_x_memory, *src_y_memory});