[Optimization] merge matmul and add

[BingooYang]

Motivation

性能优化

Modifications

将UnquantizedLinearMethod中的matmul和add用linear替换。
带bias情况基本上有加速，不带bias情况小shape下性能有下降（主要是python层if等调度开销，linear内部实现也是matmul）。

Usage or Command

无

Accuracy Tests

精度保持一致

Checklist

• [ x ] Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
  • You can add new tags based on the PR content, but the semantics must be clear.
• [ x ] Format your code, run pre-commit before commit.
• [ x ] Add unit tests. Please write the reason in this PR if no unit tests.
• [ x ] Provide accuracy results.
• [ x ] If the current PR is submitting to the release branch, make sure the PR has been submitted to the develop branch, then cherry-pick it to the release branch with the [Cherry-Pick] PR tag.

[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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[BingooYang]

/re-run all-failed

[BingooYang]

/re-run all-failed

[BingooYang]

/re-run all-failed

[PaddlePaddle-bot]

🤖 AI Code Review | 2026-04-03 17:42 CST

📋 Review 摘要

PR 概述：将 UnquantizedLinearMethod.apply() 中的 paddle.matmul + paddle.add 优化为 paddle.nn.functional.linear，减少算子调用开销。

变更范围：model_executor/layers/linear.py（核心优化）、测试 baseline 路径更新

影响面 Tag：OP Optimization

问题

未发现阻塞性问题。

✅ 代码分析

检查项	结果
PR 标题规范	✅ 包含 [Optimization] Tag
PR 描述完整性	✅ Motivation/Modifications 已填写，附带性能对比图
代码逻辑正确性	✅ PaddlePaddle 的 F.linear(x, weight, bias) 计算公式为 x @ weight + bias，与原 matmul + add 实现等价
新增 assert 检查	✅ 验证 bias shape 与 weight 最后一维匹配，有助于提前发现配置错误
测试覆盖	✅ baseline 已更新（0402 → 0403），精度验证通过

总体评价

代码变更逻辑正确，性能优化合理。带 bias 情况使用 F.linear 可减少 Python 层调度开销；不带 bias 情况保持使用 matmul 避免小 shape 下的性能损失，符合 PR 描述中的性能分析结论。