fix softmax bw and table_size in non-bit-exact case

Author: calad0i

hls4ml/backends/vivado/passes/core_templates.py

@@ -225,6 +225,10 @@ def format(self, node):
         params.setdefault('n_outer', 1)
         params.setdefault('exp_scale', 1.0)
         params.setdefault('parallelization_factor', -1)
+        if params['accum_t'].name == 'model_default_t':  # type: ignore
+            params['accum_t'] = params['exp_table_t']
+        if params['inv_inp_t'].name == 'model_default_t':  # type: ignore
+            params['inv_inp_t'] = params['exp_table_t']
 
         if 'inp_norm_t' not in params:
             input_t = node.get_input_variable().type.precision

hls4ml/model/optimizer/passes/bit_exact.py

@@ -552,6 +552,9 @@ def _(node: Softmax):
     if not node.attributes.get('_bit_exact', False):
         # Softmax is not bit-exact by default
         warn(f'Softmax layer {node.name} is converted from a frontend not supporting bit-exact softmax.')
+        accum_t = node.attributes['accum_t']
+        default_register_precision(node)
+        node.attributes['accum_t'] = accum_t
         return
 
     inv_inp_t: FixedPrecisionType = node.attributes['inv_inp_t'].precision