Fix NchwcTransformer null deref on node with unresolved schema (#28392)

Author: tairenpiao

onnxruntime/core/graph/graph_utils.cc

@@ -396,10 +396,14 @@ bool IsSupportedOptypeVersionAndDomain(const Node& node,
 bool IsSupportedOptypeVersionAndDomain(const Node& node, std::string_view op_type,
                                        gsl::span<const ONNX_NAMESPACE::OperatorSetVersion> versions,
                                        std::string_view domain) {
+#if !defined(ORT_MINIMAL_BUILD)
+  // node.Op() can be null for a node whose schema is not yet resolved.
+  const auto* op_schema = node.Op();
+#endif
   return (node.OpType() == op_type &&
   // we don't have op schemas in the minimal build so there's no way to check the deprecated flag
 #if !defined(ORT_MINIMAL_BUILD)
-          !node.Op()->Deprecated() &&
+          op_schema != nullptr && !op_schema->Deprecated() &&
 #endif
           MatchesOpSinceVersion(node, versions) && MatchesOpSetDomain(node, domain));
 }

onnxruntime/test/optimizer/nchwc_optimizer_test.cc

@@ -236,6 +236,16 @@ void NchwcOptimizerTester(const std::function<void(NchwcTestHelper& helper)>& bu
 
 #ifndef DISABLE_CONTRIB_OPS
 
+// Regression test for #28392: NchwcTransformer must not crash when a node's schema is unresolved (node.Op() == nullptr).
+TEST(NchwcOptimizerTests, MatMulCastDoesNotCrashOnUnresolvedSchema) {
+  SessionOptions session_options;
+  session_options.graph_optimization_level = TransformerLevel::Level3;
+  session_options.session_logid = "NchwcOptimizerTests";
+  InferenceSessionWrapper session{session_options, GetEnvironment()};
+  ASSERT_STATUS_OK(session.Load(ORT_TSTR("testdata/transform/transpose_cast_matmul_fp16.onnx")));
+  ASSERT_STATUS_OK(session.Initialize());
+}
+
 TEST(NchwcOptimizerTests, ConvNchw) {
   auto test_case = [&](const std::string& activation_op_type) {
     auto build_test_case = [&](NchwcTestHelper& helper) {