[Feature] add Dflash on Ascend

[chenaoxuan]

Purpose

Test Plan

Test Result

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.

💬 Join our developer Slack at https://slack.vllm.ai to discuss your PR in #pr-reviews, coordinate on features in #feat- channels, or join special interest groups in #sig- channels.

Just a reminder: PRs would not trigger full CI run by default. Instead, it would only run fastcheck CI which starts running only a small and essential subset of CI tests to quickly catch errors.

You ask your reviewers to trigger select CI tests on top of fastcheck CI.

Once the PR is approved and ready to go, your PR reviewer(s) can run CI to test the changes comprehensively before merging.

To run CI, PR reviewers can either: Add ready label to the PR or enable auto-merge.

If you have any questions, please reach out to us on Slack at https://slack.vllm.ai.

🚀

[mergify]

Documentation preview: https://vllm--36764.org.readthedocs.build/en/36764/

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @chenaoxuan.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[mergify]

Documentation preview: https://vllm--36764.org.readthedocs.build/en/36764/

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @chenaoxuan.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[gemini-code-assist]

Code Review

This pull request introduces a new speculative decoding method named "dflash" for Qwen3 models. The changes involve defining a new DFlashQwen3ForCausalLM model, integrating "dflash" into the speculative configuration types, hash computation, method detection, and argument verification. It also adds specific auxiliary hidden state layer configurations for "dflash" within the Qwen3 model and adjusts position tensor initialization in the speculative decoding framework. Review comments indicate a type hint violation in get_eagle3_aux_hidden_state_layers where a list is returned instead of a tuple for the "dflash" method, and a potential side effect in Qwen3Model's __init__ due to an in-place modification of self.config.eagle_config when updating drafter_config.

[gemini-code-assist]

The function get_eagle3_aux_hidden_state_layers is type-hinted to return a tuple[int, ...], but for the dflash method, it returns a list. This violates the type hint and could lead to unexpected behavior. Please return a tuple instead.

Suggested change

	return [1, 9, 17, 25, 33]
	return (1, 9, 17, 25, 33)

[gemini-code-assist]

The update method is called on drafter_config, which might be a direct reference to self.config.eagle_config. This can lead to an unintended in-place modification of self.config.eagle_config, which could have side effects elsewhere. To avoid this, you should create a copy of eagle_config before updating it.

Suggested change

	drafter_config = getattr(self.config, "eagle_config", {})
	drafter_config.update(getattr(self.config, "dflash_config", {}))
	drafter_config = getattr(self.config, "eagle_config", {}).copy()
	drafter_config.update(getattr(self.config, "dflash_config", {}))

[benchislett]

Please leave as a draft PR until it is functional and ready-for-review, at which time you should include a PR description and unit tests.