Update libomp build to LLVM 23.1.2

[Czaki]

LLVM 23 removed the legacy standalone openmp build, so build it via the runtimes directory with -DLLVM_ENABLE_RUNTIMES=openmp. Also avoid failing on unset MACOSX_DEPLOYMENT_TARGET under set -u.

Summary by CodeRabbit

• Chores
  • Updated the OpenMP build to use LLVM 23.1.2 and its current runtime layout; the build and installation steps remain in place.
  • Set the macOS build deployment target to 10.15. When the target is unset, the build now displays it as empty.
  • These changes apply to building and packaging; no end-user-facing behavior changes are included.

[coderabbitai]

Navigate logical layers of code changes, visualize relationships, and explore their blast radius.

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: fa52ba0b-82ff-496d-a406-64bbfcb1ca2b

📥 Commits

Reviewing files that changed from the base of the PR and between c2b004d and 78f55ec.

📒 Files selected for processing (1)

• pyproject.toml

Included review availability: This review used your included allowance. Your plan provides up to 1 included review per hour; 0 remain after this review.

---

📝 Walkthrough

Walkthrough

The build script now defaults to LLVM 23.1.2 and configures OpenMP through LLVM’s runtimes directory. It prints an empty deployment-target value when MACOSX_DEPLOYMENT_TARGET is unset. The macOS cibuildwheel configuration sets MACOSX_DEPLOYMENT_TARGET to 10.15.

Changes

OpenMP build configuration

Layer / File(s)	Summary
Update the OpenMP build configuration build_utils/build_libomp.sh, pyproject.toml	The script uses LLVM 23.1.2 by default, enters the LLVM project root, and configures OpenMP through ../runtimes with LLVM_ENABLE_RUNTIMES=openmp. It prints an empty deployment-target value when the variable is unset. The macOS cibuildwheel configuration sets MACOSX_DEPLOYMENT_TARGET to 10.15.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 78f55

The OpenMP build has no verified configuration blocker. macOS wheels target 10.15, with no lower minimum declared by the project.

Architecture Summary

Architecture risk: 🔵 Low · up to 78f55

The change affects 2 systems.

Changed systems: build_utils, pyproject.toml

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — build_utils (service) was modified; 1 changed file maps to changed impact.
• observed — pyproject.toml (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

• observed — Modified behavior in build_utils/build_libomp.sh: The default LLVM version changes from 19.1.1 to 23.1.2. The deployment-target output now expands to an empty value when the variable is unset. The script enters the cloned LLVM project root instead of llvm-project/openmp and configures OpenMP through ../runtimes with LLVM_ENABLE_RUNTIMES=openmp, replacing the standalone CMake source path.
• observed — Modified behavior in pyproject.toml: The macOS cibuildwheel configuration adds a comment about libomp using aligned_alloc and sets MACOSX_DEPLOYMENT_TARGET to 10.15.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely identifies the main change: updating the libomp build to LLVM 23.1.2.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1…
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

🧪 Generate unit tests (beta)

• Commit to this branch
• Create a new PR

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}