[TVMJS] Check DataType.NUMPY2STR when saving array (#17174)

Prior to this commit, the `dtype` string used by
`tvmjs.dump_ndarray_cache` was generated as `str(np_array.dtype)`.
While this works in most cases, there are a few naming differences
between TVM datatypes and numpy datatypes, such as `"float8_e4m3fn"`
in Numpy being equivalent to `"e4m3_float8"` in TVM.

This commit updates `dump_ndarray_cache` to check `DataType.NUMPY2STR`
for the datatype string, allowing round-trip save/load of float8
arrays.

python/tvm/contrib/tvmjs.py

@@ -35,6 +35,7 @@
 
 import tvm
 from tvm._ffi.libinfo import find_lib_path
+from tvm.runtime import DataType
 
 from .emcc import create_tvmjs_wasm
 
@@ -276,7 +277,13 @@ def dump_ndarray_cache(
             v = v.numpy()
 
         # prefer to preserve original dtype, especially if the format was bfloat16
-        dtype = str(origin_v.dtype) if isinstance(origin_v, tvm.nd.NDArray) else str(v.dtype)
+        dtype = origin_v.dtype if isinstance(origin_v, tvm.nd.NDArray) else v.dtype
+
+        if dtype in DataType.NUMPY2STR:
+            dtype = DataType.NUMPY2STR[dtype]
+        else:
+            dtype = str(dtype)
+
         total_bytes += math.prod(v.shape) * np.dtype(v.dtype).itemsize
 
         # convert fp32 to bf16

tests/python/contrib/test_tvmjs.py

@@ -0,0 +1,64 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+"""Test contrib.tvmjs"""
+
+import tempfile
+
+import numpy as np
+import pytest
+
+import tvm.testing
+from tvm.contrib import tvmjs
+
+dtype = tvm.testing.parameter(
+    "int8",
+    "int16",
+    "int32",
+    "int64",
+    "uint8",
+    "uint16",
+    "uint32",
+    "uint64",
+    "float16",
+    "float32",
+    "float64",
+    "float8_e4m3fn",
+    "float8_e5m2",
+)
+
+
+def test_save_load_float8(dtype):
+    if "float8" in dtype or "bfloat16" in dtype:
+        ml_dtypes = pytest.importorskip("ml_dtypes")
+        np_dtype = np.dtype(getattr(ml_dtypes, dtype))
+    else:
+        np_dtype = np.dtype(dtype)
+
+    arr = np.arange(16, dtype=np_dtype)
+
+    with tempfile.TemporaryDirectory(prefix="tvm_") as temp_dir:
+        tvmjs.dump_ndarray_cache({"arr": arr}, temp_dir)
+        cache, _ = tvmjs.load_ndarray_cache(temp_dir, tvm.cpu())
+
+    after_roundtrip = cache["arr"].numpy()
+
+    np.testing.assert_array_equal(arr, after_roundtrip)
+
+
+if __name__ == "__main__":
+    tvm.testing.main()