fix the case where the buffer for past_state == present_state

[guschmue]

in the case we pass the same buffer for past_state and present_state, dawn complains about the buffer bound as input/RO and the same buffer being bound as output/RW.

[Copilot]

Pull request overview

This PR addresses a WebGPU/Dawn validation issue that occurs when past_state and present_state alias the same underlying buffer, which previously caused the same buffer to be bound twice with incompatible access modes (RO input + RW output). The fix avoids dual-binding by re-routing reads to the output binding (when safe) and, for causal conv, splitting state update into a follow-up dispatch when in-place aliasing is detected.

Changes:

• LinearAttention: when past_state aliases present_state, stop binding initial_state as an input and instead read the initial state from present_state in the shader.
• CausalConvWithState: when conv_state aliases present_state, skip writing present_state in the main convolution shader and run a second shader dispatch to update state in-place.
• Extend shader template parameters / cache hints to account for the new aliasing modes and generated shader variants.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
onnxruntime/contrib_ops/webgpu/bert/linear_attention.wgsl.template	Adds a template-controlled path to load the initial state from present_state when buffers alias.
onnxruntime/contrib_ops/webgpu/bert/linear_attention.h	Extends LinearAttentionProgram to carry the aliasing flag into shader generation.
onnxruntime/contrib_ops/webgpu/bert/linear_attention.cc	Detects aliasing, adjusts bindings, and adds the new template parameter and cache hint component.
onnxruntime/contrib_ops/webgpu/bert/causal_conv_with_state.wgsl.template	Wraps present_state writes with a template flag so it can be disabled when aliasing would cause RO/RW dual-bind.
onnxruntime/contrib_ops/webgpu/bert/causal_conv_with_state.h	Adds an output_present_state flag to the main program and introduces a dedicated update-state program.
onnxruntime/contrib_ops/webgpu/bert/causal_conv_with_state.cc	Detects aliasing, conditionally omits present_state output binding, and runs a second dispatch to update state when needed.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.