!1090 fix mean and var shape in layernorm

Merge pull request !1090 from JichenZhao/layernorm_mean_var_shape

mindspore/ccsrc/operator/prim_nn.cc

@@ -301,7 +301,7 @@ AbstractBasePtr InferImplLayerNorm(const AnalysisEnginePtr &, const PrimitivePtr
 
   // begin_norm_axis and begin_params_axis should be smaller than the size of input_x and >= -1
   ValuePtr bna_ptr = primitive->GetAttr("begin_norm_axis");
-  (void)CheckAxis(op_name, bna_ptr, -1, SizeToInt(input_rank) - 1);
+  int begin_norm_axis = CheckAxis(op_name, bna_ptr, -1, SizeToInt(input_rank) - 1);
 
   ValuePtr bpa_ptr = primitive->GetAttr("begin_params_axis");
   int begin_params_axis = CheckAxis(op_name, bpa_ptr, -1, SizeToInt(input_rank) - 1);
@@ -341,7 +341,13 @@ AbstractBasePtr InferImplLayerNorm(const AnalysisEnginePtr &, const PrimitivePtr
   }
 
   auto mean_var_shape_value = input_shape->shape();
-  mean_var_shape_value[input_rank - 1] = 1;
+  if (begin_norm_axis == -1) {
+    mean_var_shape_value[input_rank - 1] = 1;
+  } else {
+    for (size_t i = begin_norm_axis; i < input_rank; ++i) {
+      mean_var_shape_value[i] = 1;
+    }
+  }
 
   auto mean = input_x->Broaden();
   mean->set_shape(std::make_shared<Shape>(mean_var_shape_value));