[BugFix] Add float4 definitions to cpp/common.h for CPU backend

[ShaobinChen-AH]

Problem

When compiling CPU kernels that use T.copy, the generated code references float4 type which is not defined, causing compilation errors:

Root Cause

The CPU backend uses tl_templates/cpp/common.h which lacked float4 definitions. CUDA backend doesn't need this because float4 is built into CUDA SDK.

Fix

• Add float4 struct definition to src/tl_templates/cpp/common.h
• Add C++ constructors:
  • Default constructor
  • Single float constructor (for broadcast operations)
  • Four floats constructor
• Add make_float4 helper function

Testing

pytest testing/python/cpu/test_tilelang_cpu_gemm.py::test_matmul_with_copy_cython -v
# PASSED


<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

* **New Features**
  * Added vector type support in the backend for enhanced computational operations.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d078d669-e948-4a14-bd06-c00ccc57f495

📥 Commits

Reviewing files that changed from the base of the PR and between 00267e4 and 289ef29.

📒 Files selected for processing (1)

• src/tl_templates/cpp/common.h

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📝 Walkthrough

Walkthrough

Introduces a cross-language float4 vector type with C++ constructors (default, scalar, component-wise) and a C typedef, alongside a make_float4 factory helper function. Replaces a previous "Not Implemented" placeholder in the common header.

Changes

Cohort / File(s)	Summary
Vector Type Definition src/tl_templates/cpp/common.h	Added struct float4 with three constructors (default, single-value, component-wise), C typedef variant, and make_float4() factory function for creating instances across C and C++ code paths.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

• LJC00118
• LeiWang1999
• SiriusNEO

Poem

🐰 A four-float friend now hops through code,
With constructors bright on each abode,
Both C and C++ shall play along,
With make_float4's helper song!
Let vectors dance where CPUs go,
Four components, all aglow! 🎉

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding float4 definitions to cpp/common.h for the CPU backend to fix compilation errors.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[github-actions]

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

Please remember to run pre-commit run --all-files in the root directory of the project to ensure your changes are properly linted and formatted. This will help ensure your contribution passes the format check.

We appreciate you taking this step! Our team will review your contribution, and we look forward to your awesome work! 🚀

[SiriusNEO]

Repeated: #1901