Plugin EP: Fix bug that incorrectly assigned duplicate MetDef IDs to fused nodes in different GraphViews

[adrianlizarraga]

Description

Fixes a bug where PluginExecutionProvider::GetCapability() incorrectly assigned duplicate MetaDef IDs to fused nodes that live in different GraphViewer instances (e.g., the then/else branches of an If node).

The root cause was that GetCapability() created a new ModelMetadefIdGenerator on every invocation. Since the graph partitioner calls GetCapability() once per subgraph, the generator's monotonic counter reset each time, producing colliding IDs across subgraphs. This caused session creation to fail with:

Failed to add kernel for example_ep_9433721956998717990_0 example_ep example_ep: Conflicting with a registered kernel with op versions. the since version is: 1

Fix

• Promoted ModelMetadefIdGenerator to an instance member of PluginExecutionProvider so the same generator is reused across all GetCapability() calls, ensuring unique MetaDef IDs.
  • This is also consistent with how existing provider-bridge EPs create and use a single generator instance.
  • Bonus perf improvement: No longer recomputes the entire model's hash on every call to GetCapability().

Testing

Example EP changes:

• Refactored SaveConstantInitializers() → TrySaveConstantInitializer() to save initializers per-node-input instead of via graph.GetInitializers(), which doesn't return initializers defined in parent or sibling subgraphs.
• Extracted CopiesConstantInitializers() helper to deduplicate the condition for drop_constant_initializers.

Unit testing:

• Added unit test called CompilingPluginEp_MultiSubgraphs_DuplicateMetaDefIdBug — runs an If model with Mul nodes in both branches, verifying that both fused nodes receive unique MetaDef IDs and the session creates/runs successfully.

Credit to @apwojcik for finding the bug.

[Copilot]

Pull request overview

Fixes a bug where PluginExecutionProvider::GetCapability() created a new ModelMetadefIdGenerator per invocation, causing duplicate MetaDef IDs for fused nodes across different subgraphs (e.g., If branches). Also refactors the example plugin EP's initializer saving logic.

Changes:

• Promoted ModelMetadefIdGenerator from a local variable in GetCapability() to an instance member of PluginExecutionProvider to ensure unique IDs across calls.
• Refactored example EP's SaveConstantInitializers() into CopiesConstantInitializers() and TrySaveConstantInitializer() to handle initializers from parent/sibling subgraphs.
• Added unit test CompilingPluginEp_MultiSubgraphs_DuplicateMetaDefIdBug verifying the fix with an If model.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
onnxruntime/core/session/plugin_ep/ep_plugin_provider_interfaces.h	Added metadef_id_generator_ as instance member
onnxruntime/core/session/plugin_ep/ep_plugin_provider_interfaces.cc	Use instance member instead of local generator; moved include to header
onnxruntime/test/autoep/library/example_plugin_ep/ep.h	Replaced SaveConstantInitializers with CopiesConstantInitializers and TrySaveConstantInitializer
onnxruntime/test/autoep/library/example_plugin_ep/ep.cc	Implemented refactored methods; moved initializer saving to CompileImpl per-input
onnxruntime/test/autoep/test_execution.cc	Added regression test for duplicate MetaDef ID bug

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