Changes/LLVM-16

LLVM 16

Summary

Update all llvm sub-projects in Fedora Linux to version 16.

Owner

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

Current status

• Targeted release: Fedora Linux 38
• Last updated: 2022-12-09
• devel thread
• FESCo issue: #2909
• Tracker bug: #2152199
• Release notes tracker: #935

Detailed Description

All llvm sub-projects in Fedora will be updated to version 16, and there will be a soname version change for the llvm libraries. Compatibility packages clang15 and llvm15 will be added to ensure that packages that currently depend on clang and llvm version 15 libraries will continue to work.

In addition, the default LTO mode for Fedora packages compiling with clang will be changed from "Full LTO" to "Thin LTO". "Thin LTO" uses much less compiler resources than "Full LTO", and is better tested and supported by upstream. Note that this will not be a change to clang itself, but rather a change to the compiler flags for clang in redhat-rpm-config.

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.
  • Build release candidates into @fedora-llvm-team/llvm16 COPR.
  • Build final release (March 2023) into Rawhide and F38 branches.

• Other developers:
  • Maintainers of packages that depend on clang-libs or llvm-libs will need to update their spec files to depend on the clang15 and llvm15 compatibility packages if they want to rebuild their package and it does not work with LLVM 16 yet. The key point here is that spec file changes are only needed if a package is going to be rebuilt after LLVM 16 is added to Fedora. The compatibility packages will ensure that already built packages continue to work.

• Release engineering: [1]

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

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

• Alignment with Objectives:

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 16.

Dependencies

This change can be made without updating any other packages. However, as mention before, packages that need to use LLVM 15 will need to update their spec file on their first rebuild after this change.

Contingency Plan

• Contingency mechanism: (What to do? Who will do it?) Contingency mechanism: (What to do? Who will do it?): If there are major problems with LLVM 16, the compatibility package provide a way for other packages to continue using LLVM 15.
• Contingency deadline: Final 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 16:

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