ADD feature check for merge mode and layers order

Author: Enrico Lupi

hls4ml/backends/vitis/passes/feature_check.py

@@ -49,3 +49,41 @@ def transform(self, model, node):
             f'WARNING: "ResourceUnrolled" strategy in "{node.name}" ({node.class_name}) may have unexpected II in'
             'Vitis backend.\nVerify that the final design satisfies the latency/II constraints.'
         )
+
+
+class ValidateBidirectionalMergeMode(OptimizerPass):
+    _unrolled_layer_cls = ['Bidirectional']
+
+    def match(self, node):
+        is_bidirectional_rnn_layer = (
+            len([layer_cls for layer_cls in self._unrolled_layer_cls if layer_cls in node.class_name]) > 0
+        )
+        is_merge_mode_not_concat = node.get_attr('merge_mode', 'concat') != 'concat'
+
+        return is_bidirectional_rnn_layer and is_merge_mode_not_concat
+
+    def transform(self, model, node):
+        merge_mode = node.get_attr('merge_mode', 'concat')
+        print(
+            f'WARNING: "{merge_mode}" merge mode in "{node.name}" ({node.class_name}) is not supported in Vitis backend. '
+            'Switching to "concat" merge mode.'
+        )
+        node.set_attr('merge_mode', 'concat')
+
+
+class ValidateBidirectionalLayerOrder(OptimizerPass):
+    _unrolled_layer_cls = ['Bidirectional']
+
+    def match(self, node):
+        is_bidirectional_rnn_layer = (
+            len([layer_cls for layer_cls in self._unrolled_layer_cls if layer_cls in node.class_name]) > 0
+        )
+        is_layer_order_swapped = node.get_attr('swapped_order', False)
+
+        return is_bidirectional_rnn_layer and is_layer_order_swapped
+
+    def transform(self, model, node):
+        print(
+            f'WARNING: The selected order for forward and backward layers in "{node.name}" ({node.class_name}) is not '
+            'supported in Vitis backend. Switching to forward layer first, backward layer last.'
+        )

hls4ml/backends/vitis/vitis_backend.py

@@ -17,6 +17,8 @@ def _register_flows(self):
             'vitis:validate_conv_implementation',
             'vitis:validate_resource_strategy',
             'vitis:validate_resource_unrolled_strategy',
+            'vitis:validate_bidirectional_merge_mode',
+            'vitis:validate_bidirectional_layer_order',
         ]
         validation_flow = register_flow('validation', validation_passes, requires=['vivado:init_layers'], backend=self.name)