Changes/LLVM-17

LLVM 17

Summary

Update all llvm sub-projects in Fedora Linux to version 17.

Owner

• Name: Tom Stellard
• Email: <tstellar@redhat.com>

Current status

• Targeted release: Fedora Linux 39
• Last updated: 2023-09-28
• devel thread
• FESCo issue: #3034
• Tracker bug: #2233282
• Release notes tracker: #1042

Detailed Description

All llvm sub-projects in Fedora will be updated to version 17, and there will be a soname version change for the llvm libraries. Compatibility packages clang16, llvm16, and lld16 will be added to ensure that packages that currently depend on clang and llvm version 16 libraries will continue to work.

Other notable changes:

• The Clang Resource Directory will be moved from /usr/lib64/clang/17/ to /usr/lib/clang/17/ this is the location of clang's internal headers and runtime libraries like libomp and compiler-rt. Package owners of packages that read or write this directory will need to update their packages when rebuilding against/with LLVM 17. The %clang_resource_dir helper macro can be used to make this transition smoother, and packages are encouraged to update to use this macro even before the LLVM 17 update.

• Along with the Clang Resource Directory change, compiler-rt will now install its libraries into /usr/lib/clang/17/lib/$TRIPLE/ instead of /usr/lib64/clang/17/lib/

• The macros.clang file with RPM macros will be moved from the clang-devel package to the clang-resource-filesystem package.

LLVM Build Schedule

We will be changing our build schedule slightly from previous Fedora releases. We will now plan to ship a release candidate in Fedora build prior to the Beta Freeze rather than waiting until after.

Important Dates

• July 28: Upstream: 17.0.0-rc1 Release
• Aug 8: Fedora: f39 branch created
• Aug 11: Upstream: 17.0.0-rc2 Release
• Aug 22: Fedora: f39 Beta Freeze
• Aug 25: Upstream: 17.0.0-rc3 Release
• Sep 8: Upstream: 17.0.0 Release
• Oct 10: Fedora: f39 Final Freeze

Plan

1. Build LLVM 17.0.0-rc1 in COPR.
2. Build LLVM 17.0.0-rc1 into a rawhide side-tag in Koji.
3. Build LLVM 17.0.0-rc1 into a f39 side-tag in Koji.
4. Build LLVM 17.0.0-rc2 into a rawhide side-tag in Koji.
5. Build LLVM 17.0.0-rc2 into a f39 side-tag in Koji.
6. Push F39 Bodhi Update with 17.0.0-rc2 (or 17.0.0-rc1 if -rc2 is not ready) prior to the Beta Freeze.
7. Continue building new release candidates and pushing them to stable until the Final Freeze.

We are not planning to push 17.0.0-rc1 into rawhide because the library ABI is not stabilized at that point. Typically, the ABI stabilizes after -rc2, but there are no guarantees from upstream about this. Given the history of minimal ABI changes after -rc2, we feel like it's safe to push -rc2 into rawhide. The worst case scenario would be an ABI change -rc3 that we force us to patch LLVM to maintain compatibility with the -rc2 ABI. This scenario would not require rebuilding LLVM library uses in Fedora, so this would not require much extra work from our team.

Updates after 17.0.0-rc2 will generally be very small and can be done after the Final Freeze is over. If we are late packaging -rc3 or the final release, we will not ask for a Final Freeze exception, unless they contain a fix for a critical release blocking bug.

Benefit to Fedora

New features and bug fixes provided by the latest version of LLVM.

Scope

• Proposal owners:
  • Review existing llvm and clang compatibility packages and orphan any packages that are no longer used.
  • Do scratch builds of Fedora packages that depend on llvm and report issues to package maintainer.

• Other developers:
  • Fix build issues found with LLVM-17 or switch their package to use the llvm16 compat libs. The LLVM team no longer plans to block Bodhi updates on dependent packages that fail to build or run with LLVM-17. There should be around 6-8 weeks between when -rc1 lands in koji and the Final Freeze for package maintainers to fix issues uncovered with the LLVM-17 update.

• Release engineering: [1]

• Policies and guidelines: N/A (not needed for this Change)

• Trademark approval: N/A (not needed for this Change)

• Alignment with Community Initiatives:

Upgrade/compatibility impact

This change should not impact upgradeability.

How To Test

The CI tests for the llvm sub-packages in Fedora will be used to catch regressions that might be potentially introduced by the update to LLVM 17.

Dependencies

Packages that depend on one of the llvm packages will need to be updated to work with LLVM17 or will need to switch to using one of the llvm16 compat packages.

Contingency Plan

• Contingency mechanism: If there are major problems with LLVM 17, the compatibility package provide a way for other packages to continue using LLVM 16.
• Contingency deadline: Beta Freeze
• Blocks release? No

Documentation

Release notes will be added for this change.

Release Notes

LLVM sub-projects in Fedora have been updated to version 17:

• llvm
• clang
• lld
• lldb
• compiler-rt
• libomp
• llvm-test-suite
• libcxx
• python-lit
• flang
• mlir
• polly
• libclc
• llvm-bolt