Added exception for warning caused while creating int4 tensor (#461)

Signed-off-by: Hrishith Thadicherla <[email protected]>

Author: hthadicherla

modelopt/onnx/quantization/gs_patching.py

@@ -39,7 +39,14 @@ def _make_constant(
     converted_dtype = (
         dtype if isinstance(values, LazyValues) else onnx.helper.tensor_dtype_to_np_dtype(dtype)
     )
-    if values.dtype != converted_dtype:
+
+    # Allow int8/uint8 as intermediate representation for INT4/UINT4
+    # INT4/UINT4 values are stored as int8/uint8 in numpy arrays and packed during export
+    is_valid_int4_intermediate = (dtype == onnx.TensorProto.INT4 and values.dtype == np.int8) or (
+        dtype == onnx.TensorProto.UINT4 and values.dtype == np.uint8
+    )
+
+    if not is_valid_int4_intermediate and values.dtype != converted_dtype:
         logger.error(
             f"Trying to create tensor with incompatible types: `{values.dtype}`, `{dtype}`"
         )