[EP ABI] Add APIs to create control flow kernels for plugin EPs

[adrianlizarraga]

Description

Adds APIs to enable plugin EPs to create and register kernels for control flow operators (If, Loop, and Scan). The implementation provides ORT-managed kernel implementations that handle subgraph execution while allowing EPs to provide device-specific helper functions for operations like tensor concatenation and transposition.

Key changes:

• Adds four EP API functions: CreateIfKernel, CreateLoopKernel, CreateScanKernel, and ReleaseKernelImpl for creating control flow kernel implementations
• Introduces public helper structures (OrtLoopKernelHelper, OrtScanKernelHelper) that EPs implement to provide device-specific operations
• Updates the example kernel-based EP with kernel registrations for all control flow operators and adds corresponding test models.

Motivation and Context

[Copilot]

Pull request overview

This pull request adds APIs to enable plugin execution providers (EPs) to create and register kernels for control flow operators (If, Loop, and Scan). The implementation provides ORT-managed kernel implementations that handle the complex subgraph execution while allowing EPs to provide device-specific helper functions for operations like tensor concatenation and transposition.

Key changes:

• Adds three new OrtEpApi functions: CreateIfKernel, CreateLoopKernel, and CreateScanKernel for creating control flow kernel implementations
• Introduces helper structures (OrtLoopKernelHelper, OrtScanKernelHelper) that EPs implement to provide device-specific operations
• Adds comprehensive test coverage with new ONNX model test cases and execution tests for all three control flow operators

Reviewed changes

Copilot reviewed 28 out of 31 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
onnxruntime/test/testdata/scan_mul.py	Python script to generate test model for Scan operator
onnxruntime/test/testdata/scan_mul.onnx	Binary ONNX test model for Scan operator
onnxruntime/test/testdata/loop_sub_one.py	Python script to generate test model for Loop operator
onnxruntime/test/testdata/loop_sub_one.onnx	Binary ONNX test model for Loop operator
onnxruntime/test/testdata/if_mul.py	Python script to generate test model for If operator
onnxruntime/test/testdata/if_mul.onnx	Binary ONNX test model for If operator
onnxruntime/test/autoep/test_execution.cc	Adds execution tests for If, Loop, and Scan operators with the plugin EP
onnxruntime/test/autoep/library/example_plugin_ep_kernel_registry/kernels/utils.h	Updates kernel creation macro to match new Create signature returning OrtKernelImpl*
onnxruntime/test/autoep/library/example_plugin_ep_kernel_registry/kernels/squeeze.h/cc	Updates Create method signature and adds creator field initialization
onnxruntime/test/autoep/library/example_plugin_ep_kernel_registry/kernels/relu.h/cc	Updates Create method signature and adds creator field initialization
onnxruntime/test/autoep/library/example_plugin_ep_kernel_registry/kernels/binary_op.h/cc	Updates Create method signature and adds creator field initialization
onnxruntime/test/autoep/library/example_plugin_ep_kernel_registry/kernels/scan.h/cc	Implements ScanHelper for Scan operator with transpose helper function
onnxruntime/test/autoep/library/example_plugin_ep_kernel_registry/kernels/loop.h/cc	Implements LoopHelper for Loop operator with concatenation helper function
onnxruntime/test/autoep/library/example_plugin_ep_kernel_registry/kernels/if.h/cc	Implements IfHelper for If operator
onnxruntime/test/autoep/library/example_plugin_ep_kernel_registry/ep_kernel_registration.cc	Registers If, Loop, and Scan kernels with the plugin EP
onnxruntime/test/autoep/library/example_plugin_ep_kernel_registry/ep.cc	Updates GetCapability to claim If, Loop, and Scan operators
onnxruntime/core/session/plugin_ep/ep_kernel_registration.cc	Updates PluginEpOpKernel to derive from IControlFlowKernel and implement SetupSubgraphExecutionInfo
onnxruntime/core/session/plugin_ep/ep_control_flow_kernel_impls.h	Defines control flow kernel implementation classes that wrap CPU EP kernels
onnxruntime/core/session/plugin_ep/ep_control_flow_kernel_impls.cc	Implements control flow kernel wrappers and helper function adapters
onnxruntime/core/session/plugin_ep/ep_api.h	Declares new control flow kernel creation functions
onnxruntime/core/session/plugin_ep/ep_api.cc	Implements control flow kernel creation APIs with validation
onnxruntime/core/providers/cpu/controlflow/loop.h	Changes SetConcatOutputFunc visibility to public
onnxruntime/core/framework/session_state.cc	Updates CreateSubgraphSessionState to handle plugin EPs with control flow operators
include/onnxruntime/core/session/onnxruntime_ep_c_api.h	Adds OrtKernelImplCreator enum, helper structures, and new API function declarations
cmake/onnxruntime_unittests.cmake	Adds new control flow kernel source files to the test build

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[Copilot]

Pull request overview

Copilot reviewed 28 out of 31 changed files in this pull request and generated 4 comments.

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