"fix style" (#12600)

paddle/fluid/operators/elementwise_op_function.h

@@ -534,8 +534,8 @@ void ElemwiseGradCompute(const framework::ExecutionContext& ctx,
                          const framework::Tensor& dout, int axis,
                          framework::Tensor* dx, framework::Tensor* dy,
                          DX_OP dx_op, DY_OP dy_op) {
-  const framework::DDim x_dim = x.dims();
-  const framework::DDim y_dim = y.dims();
+  const framework::DDim& x_dim = x.dims();
+  const framework::DDim& y_dim = y.dims();
   if (x.dims() == y.dims()) {
     ElemwiseGradComputeNoBroadcast<DeviceContext, T, DX_OP, DY_OP>(
         ctx, x_dim, y_dim, x, y, out, dout, axis, dx, dy, dx_op, dy_op);
@@ -558,19 +558,19 @@ void ElemwiseExplicitGradCompute(const framework::ExecutionContext& ctx,
                                  framework::Tensor* dx, framework::Tensor* dy,
                                  DX_OP dx_op, DY_OP dy_op) {
   if (dy == nullptr) {
-    const framework::DDim dx_dims = dout.dims();
+    const framework::DDim& dx_dims = dout.dims();
     auto dy_dims = dx_dims;
     ElemwiseGradComputeNoBroadcast<DeviceContext, T, DX_OP, DY_OP>(
         ctx, dx_dims, dy_dims, x, y, out, dout, axis, dx, dy, dx_op, dy_op);
   } else {
     if (dout.dims() == dy->dims()) {
-      const framework::DDim dx_dims = dout.dims();
-      const framework::DDim dy_dims = dy->dims();
+      const framework::DDim& dx_dims = dout.dims();
+      const framework::DDim& dy_dims = dy->dims();
       ElemwiseGradComputeNoBroadcast<DeviceContext, T, DX_OP, DY_OP>(
           ctx, dx_dims, dy_dims, x, y, out, dout, axis, dx, dy, dx_op, dy_op);
     } else {  // Y is a scalar
       auto dx_dims = dout.dims();
-      const framework::DDim dy_dims = dy->dims();
+      const framework::DDim& dy_dims = dy->dims();
       ElemwiseGradComputeWithBroadcast<DeviceContext, T, DX_OP, DY_OP>(
           ctx, dx_dims, dy_dims, x, y, out, dout, axis, dx, dy, dx_op, dy_op);
     }