[Eltwise] reflect latest hlslib updates

src/finn/custom_op/fpgadataflow/eltwise.py

@@ -59,6 +59,15 @@ class StreamingEltwise(HLSCustomOp):
         my_attrs.update(super().get_nodeattr_types())
         return my_attrs
 
+    def get_eltwise_op_lambda(self):
+        eltwise_op = self.get_nodeattr("eltwiseOp")
+        eltwise_ops = {
+            "Add": "[](auto a, auto b) { return  a + b; }",
+            "Sub": "[](auto a, auto b) { return  a - b; }",
+            "AbsDiff": "[](auto a, auto b) { return  a>b? a-b : b-a; }",
+        }
+        return eltwise_ops[eltwise_op]
+
     def get_normal_input_shape(self, ind=0):
         ich = self.get_nodeattr("NumChannels")
         vecs = list(self.get_nodeattr("numInputVectors"))
@@ -338,7 +347,8 @@ class StreamingEltwise(HLSCustomOp):
         slice_in0 = "Slice<%s>" % elem_hls_type_0
         slice_in1 = "Slice<%s>" % elem_hls_type_1
         slice_out = "Slice<%s>" % out_hls_type
-        eltwise_op_str = "%sEltwiseFunction<%s, %s, %s>()" % (
+        eltwise_op_str = self.get_eltwise_op_lambda()
+        "%sEltwiseFunction<%s, %s, %s>()" % (
             op,
             elem_hls_type_0,
             elem_hls_type_1,