[Build] Question -- is it possible to override/replace a core operator?

[bluejack]

Describe the issue

I have read the extensions guidelines and it's not clear. Also, building and linking a shared library is not a trivial project. Before I go too far down the road, I want to see if anyone has done this, and if anyone knows of other examples of this.

Urgency

No response

Target platform

arm, but eventually all

Build script

I'm not quite sure even how to build the shared library yet.

Error / output

I tried a straight up gcc build, but am still working out the build flags. presumably there is a cmake example out there somewhere that would be a better idea.

Visual Studio Version

No response

GCC / Compiler Version

apple clang 15.0.0

[skottmckay]

Yes. If you create a custom operator and register it using the matching domain and name it will override.

onnxruntime/onnxruntime/test/framework/local_kernel_registry_test.cc

Lines 223 to 235 in 549cbc7

	// This tests that a custom op can override an ONNX operator implemented by ORT.
	TEST(CustomKernelTests, CustomKernelWithBuiltInSchema) {
	SessionOptions so;
	so.session_logid = "CustomKernelWithBuiltInSchema";
	// Register a custom kernel that matches the ONNX Mul but is implemented to do an Add so we can validate the
	// custom kernel overrides the ORT Mul kernel
	KernelDefBuilder def;
	def.SetName("Mul")
	.SetDomain(onnxruntime::kOnnxDomain)
	.SinceVersion(7)
	.Provider(onnxruntime::kCpuExecutionProvider)
	.TypeConstraint("T", DataTypeImpl::GetTensorType<float>());