[TRTLLM-13141][feat] Add backend-agnostic SourceIdentity gate for weight sharing (#14878)

Signed-off-by: Chien-Chun Hung <2679986+chienchunhung@users.noreply.github.com>

Author: chienchunhung

tensorrt_llm/_torch/memory/gpu_memory_backend.py

@@ -0,0 +1,35 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed 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.
+"""Backend-agnostic weight-sharing utilities (MX, GMS, ...)."""
+
+from tensorrt_llm._torch.weight_sharing.source_identity import (
+    SOURCE_IDENTITY_FORMAT_VERSION,
+    IdentityCheckDecision,
+    IdentityCheckPolicy,
+    IdentityMatchResult,
+    SourceIdentity,
+    SourceIdentityMismatchError,
+    check_weight_sharing_compatibility,
+)
+
+__all__ = [
+    "SOURCE_IDENTITY_FORMAT_VERSION",
+    "SourceIdentity",
+    "IdentityMatchResult",
+    "IdentityCheckPolicy",
+    "IdentityCheckDecision",
+    "SourceIdentityMismatchError",
+    "check_weight_sharing_compatibility",
+]