Create RUN_KERNEL macro for DepthwiseConvS8

- As in ConvS8, make a little macro for invoking the different flavours
  of the kernel.

Change-Id: Iac354ca2928b64423f79ef1a8e5cf3a70d98a96e

tflm/opt/depthwise_conv_s8.cc

diff --git a/tflm/opt/depthwise_conv_s8.cc b/tflm/opt/depthwise_conv_s8.cc
index 1b450b5..b839c6f 100644
--- a/tflm/opt/depthwise_conv_s8.cc
+++ b/tflm/opt/depthwise_conv_s8.cc
@@ -1236,40 +1236,38 @@
   TFLITE_DCHECK_EQ(output_depth, input_depth * depth_multiplier);
   TFLITE_DCHECK_EQ(bias_shape.FlatSize(), output_depth);
 
+#define RUN_KERNEL(kernel) { \
+  kernel(params, output_multiplier, output_shift, input_shape, input_data, \
+       filter_shape, filter_data, bias_shape, bias_data, output_shape, \
+       output_data \
+  ); \
+  return; \
+}
+
   if (depth_multiplier == 1 &&
       dilation_height_factor == 1 && dilation_width_factor == 1 &&
       stride_height <= 2 && stride_width <= 2) {
-    // generic implementation by default
-    auto fn = DepthwiseConvS8Generic;
-
     // special case of output depth = 32n
     if (output_depth % 32 == 0) {
       if (filter_width == 5 && filter_height == 5) {
         if (stride_width <= 1 && stride_height <= 1) {
-          fn = DepthwiseConvS85x5D32_Stride1;
-        } else {
-          fn = DepthwiseConvS85x5D32;
+          RUN_KERNEL(DepthwiseConvS85x5D32_Stride1);
         }
-      } else if (filter_width == 3 && filter_height == 3 && pad_width <= 1 && pad_height <= 1 && stride_width == 1 && stride_height == 1) {
-        fn = DepthwiseConvS83x3D32_Stride1;
-      } else if (filter_width == 3 && filter_height == 3 && pad_width <= 1 && pad_height <= 1) {
-        fn = DepthwiseConvS83x3D32;
-      } else {
-        fn = DepthwiseConvS8D32;
+        RUN_KERNEL(DepthwiseConvS85x5D32);
+      } if (filter_width == 3 && filter_height == 3 && pad_width <= 1 && pad_height <= 1 && stride_width == 1 && stride_height == 1) {
+        RUN_KERNEL(DepthwiseConvS83x3D32_Stride1);
+      } if (filter_width == 3 && filter_height == 3 && pad_width <= 1 && pad_height <= 1) {
+        RUN_KERNEL(DepthwiseConvS83x3D32);
       }
+      RUN_KERNEL(DepthwiseConvS8D32);
     }
 
-    fn(params, output_multiplier, output_shift, input_shape, input_data,
-       filter_shape, filter_data, bias_shape, bias_data, output_shape,
-       output_data);
-    return;
+    RUN_KERNEL(DepthwiseConvS8Generic);
   }
 
-  // Use reference implementation
-  tflite::reference_integer_ops::DepthwiseConvPerChannel(
-      params, output_multiplier, output_shift, input_shape, input_data,
-      filter_shape, filter_data, bias_shape, bias_data, output_shape,
-      output_data);
+  RUN_KERNEL(tflite::reference_integer_ops::DepthwiseConvPerChannel);
+
+#undef RUN_KERNEL
 }
 
 }  // namespace kelvin::opt