[None][fix] Generate CUTLASS kernel instantiations without installing cutlass_library

[lucifer1004]

The cutlass_kernels CMake step made cutlass_library importable for the kernel-instantiation generator by running setup_library.py develop --user at configure time. Under externally managed Python environments (conda/pixi/uv, which commonly set PYTHONNOUSERSITE=1) this is self-defeating — the install writes to the user site that the interpreter then refuses to read, and the generator fails with ModuleNotFoundError: cutlass_library. It also mutates the user's home site-packages (~/.local easy-install path entries) as a side effect of building one checkout, leaking state into every other Python environment of that user.

This change drops the develop-install entirely and runs the generator with PYTHONPATH pointing at the vendored CUTLASS python directory. Same generation output, no installation, no mutation outside the build tree.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Build & Tooling
  • Improved CUTLASS kernel generation setup by loading Python tooling directly from the source tree.
  • Removed the requirement to install CUTLASS Python components into the local environment during configuration.
  • Kernel generation now uses an explicitly configured Python import path for more reliable builds.

[coderabbitai]

📝 Walkthrough

Walkthrough

CUTLASS kernel generation no longer installs the Python package during CMake configuration. The generation command now sets PYTHONPATH to the CUTLASS source-tree Python directory and documents this import behavior.

Changes

CUTLASS kernel generation

Layer / File(s)	Summary
Use CUTLASS directly from the source tree cpp/tensorrt_llm/kernels/cutlass_kernels/CMakeLists.txt	Removes the setup_library.py develop --user step and configures generate_kernels.py to import CUTLASS through an explicit source-tree PYTHONPATH.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is specific, concise, and accurately reflects the main change to CUTLASS kernel instantiation generation.
Description check	✅ Passed	It explains the problem and fix clearly, but omits the template's Test Coverage and PR Checklist sections.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

cpp/tensorrt_llm/kernels/cutlass_kernels/CMakeLists.txt (1)

46-46: 🩺 Stability & Availability | 🔵 Trivial | ⚡ Quick win

cmake -E env "PYTHONPATH=..." replaces, not prepends, the existing PYTHONPATH.

This sets PYTHONPATH to only the CUTLASS source-tree dir, discarding any PYTHONPATH the invoking environment already had. If the generation step (or a transitive import in cutlass_library) relies on other entries, those are dropped. Consider preserving them, e.g. --modify PYTHONPATH=path_list_prepend:${cutlass_source_dir}/python (CMake ≥ 3.22) or expanding $ENV{PYTHONPATH}.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@cpp/tensorrt_llm/kernels/cutlass_kernels/CMakeLists.txt` at line 46, Preserve
the caller’s existing PYTHONPATH in the CMake command invoking the CUTLASS
generation step. Update the environment setup around the relevant custom command
to prepend ${cutlass_source_dir}/python using CMake’s path-list modification
support, or explicitly retain $ENV{PYTHONPATH} for compatibility with older
CMake versions.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@cpp/tensorrt_llm/kernels/cutlass_kernels/CMakeLists.txt`:
- Line 46: Preserve the caller’s existing PYTHONPATH in the CMake command
invoking the CUTLASS generation step. Update the environment setup around the
relevant custom command to prepend ${cutlass_source_dir}/python using CMake’s
path-list modification support, or explicitly retain $ENV{PYTHONPATH} for
compatibility with older CMake versions.

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📥 Commits

Reviewing files that changed from the base of the PR and between 6929451 and 41750d1.

📒 Files selected for processing (1)

• cpp/tensorrt_llm/kernels/cutlass_kernels/CMakeLists.txt