Latest revision as of 17:03, 12 December 2024

LLVM 20

This is a proposed Change for Fedora Linux.
This document represents a proposed Change. As part of the Changes process, proposals are publicly announced in order to receive community feedback. This proposal will only be implemented if approved by the Fedora Engineering Steering Committee.

Summary

Update all llvm sub-projects in Fedora Linux to version 20.

Owner

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

Current status

Targeted release: Fedora Linux 42
Last updated: 2024-12-12
Announced
[F42 Change Proposal: LLVM 20 (system-wide) Discussion thread]
FESCo issue: <will be assigned by the Wrangler>
Tracker bug: <will be assigned by the Wrangler>
Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

All llvm sub-projects in Fedora will be updated to version 20. There will be a soname version change for the llvm libraries, and an llvm19 compat package added to ensure that packages that currently depend on clang and llvm version 19 libraries will continue to work.

Other notable changes:

Install Prefix Changes The install prefix for all new llvm packages will be /usr/lib64/llvm$VERSION/ instead of /usr/. There will be symlinks for each binary and library added to /usr/ which point to the corresponding binary in /usr/lib64/llvm$VERSION/ The goal of this change is to reduce the differences between the compat and non-compat versions so that it it easier for packages that depend on llvm to switch between the two.

Merging more packages into llvm In Fedora 41, we merged the clang, libomp, compiler-rt, lld, python-lit, and lldb packages into the llvm srpm. For Fedora 42, we will also be merging llvm-bolt, polly, libcxx, and mlir into the llvm srpm.

Planned Schedule

Our plan is to push 20.1.0-rc3 into Fedora 42 as a Beta Freeze exception. Updates after 20.1.0-rc3 will generally be very small and can be done after the Beta Freeze is over. If we are late packaging releases after 20.1.0-rc3, we will not ask for a Final Freeze exception, unless they contain a fix for a critical release blocking bug.

We are not planning to push 20.1.0-rc1 into rawhide because the library ABI is not stabilized at that point. Typically, the ABI stabilizes after -rc3, but there are no guarantees from upstream about this. Given the history of minimal ABI changes after -rc3, we feel like it's safe to push -rc3 into rawhide and Fedora 42. The worst case scenario would be an ABI change in -rc4 or the final release that would force us to patch LLVM to maintain compatibility with the -rc3 ABI. This scenario would not require rebuilding LLVM library users in Fedora, so it would merely be a self-contained change to LLVM.

Important Dates

Jan 31: Begin building LLVM 20.1.0-rc1 in COPR.
Feb 4: Fedora f42 branches created
Feb 11: Begin building LLVM 20.1.0-rc2 in COPR.
Feb 18: Fedora f42 beta freeze
Feb 25: Begin building LLVM 20.1.0-rc3 in Rawhide and f42 side-tags.
Feb 25-> Mar 11: Request Beta Freeze Exception and push 20.1.0-rc3 into f42 stable.
Mar 11: Begin building LLVM 20.1.0-rc4 in Rawhide side-tag.
Mar 25: Begin building LLVM 20.1.0 in Rawhide and 42 side-tags.
Apr 1: Fedora f42 final freeze

Feedback

Benefit to Fedora

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

Scope

Proposal owners:
- Build and test early release candidates of LLVM 20 in COPR.
- Build and test later release candidates of LLVM 20 in koji.

Other developers:
- Fix build issues found with LLVM-20 or switch their package to use the llvm19 compat libs. The LLVM team will not block Bodhi updates on dependent packages that fail to build or run with LLVM-20. There should be around 6-8 weeks between when -rc1 lands in the koji side-tag and the Final Freeze for package maintainers to fix issues uncovered with the LLVM-20 update.

Release engineering: #Releng issue number

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

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

Alignment with the Fedora Strategy:

Upgrade/compatibility impact

Early Testing (Optional)

Do you require 'QA Blueprint' support? Y/N

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 20.

User Experience

Dependencies

Packages that depend on one of the llvm packages will need to be updated to work with LLVM20 or will need to switch to using one of the llvm19 compat packages.

Contingency Plan

Contingency mechanism: (What to do? Who will do it?)If there are major problems with LLVM 20, the compatibility package provide a way for other packages to continue using LLVM 19.
Contingency deadline: Final Freeze
Blocks release? No

Documentation

LLVM sub-projects in Fedora have been updated to version 20:

llvm (now includes polly, llvm-bolt, libcxx, mlir)
flang
libclc
llvm-test-suite

Release Notes

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-{{admon/important | Comments and Explanations | The page source contains comments providing guidance to fill out each section. They are invisible when viewing this page. To read it, choose the "view source" link.<br/> '''Copy the source to a ''new page'' before making changes!  DO NOT EDIT THIS TEMPLATE FOR YOUR CHANGE PROPOSAL.'''}}
-{{admon/tip | Guidance | For details on how to fill out this form, see the [https://docs.fedoraproject.org/en-US/program_management/changes_guide/ documentation].}}
-{{admon/tip | Report issues | To report an issue with this template, file an issue in the [https://pagure.io/fedora-pgm/pgm_docs pgm_docs repo].}}
 <!-- The actual name of your proposed change page should look something like: Changes/Your_Change_Proposal_Name.  This keeps all change proposals in the same namespace -->
@@ Line 29: / Line 23: @@
 == Current status ==
-[[Category:ChangePageIncomplete]]
+[[Category:ChangeAnnounced]]
 <!-- When your change proposal page is completed and ready for review and announcement -->
 <!-- remove Category:ChangePageIncomplete and change it to Category:ChangeReadyForWrangler -->
@@ Line 47: / Line 41: @@
 ON_QA -> change is fully code complete
 -->
-* [Announced]
+* [https://lists.fedoraproject.org/archives/list/devel-announce@lists.fedoraproject.org/thread/C35IAMXMZMJD3GKE5B6LW6ZRGYE5QEI7/ Announced]
-* [<will be assigned by the Wrangler> Discussion thread]
+* [F42 Change Proposal: LLVM 20 (system-wide) Discussion thread]
 * FESCo issue: <will be assigned by the Wrangler>
 * Tracker bug: <will be assigned by the Wrangler>
@@ Line 56: / Line 50: @@
 <!-- Expand on the summary, if appropriate.  A couple sentences suffices to explain the goal, but the more details you can provide the better. -->
-All llvm sub-projects in Fedora will be updated to version 20.  We will also be '''retiring the llvm package and replacing it with the llvm20 package.'''  In the future, all new versions of llvm will be distributed as a separate package with the version in its name (e.g. llvm21, llvm22, etc.)
+All llvm sub-projects in Fedora will be updated to version 20.  There will be a soname version change for the llvm libraries, and an llvm19 compat package added to ensure that packages that currently depend on clang and llvm version 19 libraries will continue to work.
-There will be a soname version change for the llvm libraries, and an llvm19 compat package added to ensure that packages that currently depend on clang and llvm version 19 libraries will continue to work.  Any compatibility packages we added for Fedora 42 will be retired or orphaned before the Fedora 43 branch date. As stated in the LLVM-19 change proposal, we plan to retire or orphan these older compatibility packages prior to the Fedora 42 branch date:
-* llvm18
-* clang18
-* lld18
-* compiler-rt18
-* libomp18
 Other notable changes:
-* '''Retring the unversioned package name''' We are going to be moving to a python-style package naming scheme where each new major version of llvm will be it's own package with the version number embedded in the name (e.g. llvm20).
+* '''Install Prefix Changes''' The install prefix for all new  llvm packages will be /usr/lib64/llvm$VERSION/ instead of /usr/.  There will be symlinks for each binary and library added to /usr/ which point to the corresponding binary in /usr/lib64/llvm$VERSION/  The goal of this change is to reduce the differences between the compat and non-compat versions so that it it easier for packages that depend on llvm to switch between the two.
-The install prefix for all new  llvm packages will be /usr/lib64/llvm$VERSION/ instead of /usr/.  There will be one version of llvm designated as the main version.  In the main version, there will be symlinks for each binary and library added to /usr/ which point to the corresponding binary in /usr/lib64/llvm$VERSION/
-The main version will have an SRPM name of llvm$VERSION, but the binary RPMs will be unversioned (e.g. llvm instead of llvm$VERSION), and they will have provides llvm(major) = $VERSION, which will allow any packages that depend on LLVM to pin their dependencies to a specific version.
-The goal of this change is to reduce the differences between the compat and non-compat versions so that it it easier for packages that depend on llvm to switch between the two.
+* '''Merging more packages into llvm'''  In Fedora 41, we merged the clang, libomp, compiler-rt, lld, python-lit, and lldb packages into the llvm srpm.  For Fedora 42, we will also be merging llvm-bolt, polly, libcxx, and mlir into the llvm srpm.
-* '''Merging more packages into llvm20'''  In Fedora 41, we merged the clang, libomp, compiler-rt, lld, python-lit, and lldb packages into the llvm srpm.  For Fedora 42, we will also be merging llvm-bolt, polly, libcxx, and mlir into the llvm20 srpm.
 === Planned Schedule ===
@@ Line 131: / Line 112: @@
 * Proposal owners:
 <!-- What work do the feature owners have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->
-** Review existing llvm and clang compatibility packages and orphan any packages that are no longer used.
 ** Build and test early release candidates of LLVM 20 in COPR.
+** Build and test later release candidates of LLVM 20 in koji.
 * Other developers: <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
@@ Line 195: / Line 176: @@
 <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+Packages that depend on one of the llvm packages will need to be updated to work with LLVM20 or will need to switch to using one of the llvm19 compat packages.
 == Contingency Plan ==
 <!-- If you cannot complete your feature by the final development freeze, what is the backup plan?  This might be as simple as "Revert the shipped configuration".  Or it might not (e.g. rebuilding a number of dependent packages).  If you feature is not completed in time we want to assure others that other parts of Fedora will not be in jeopardy.  -->
-* Contingency mechanism: (What to do?  Who will do it?) N/A (not a System Wide Change)  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Contingency mechanism: (What to do?  Who will do it?)If there are major problems with LLVM 20, the compatibility package provide a way for other packages to continue using LLVM 19.  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 <!-- When is the last time the contingency mechanism can be put in place?  This will typically be the beta freeze. -->
-* Contingency deadline: N/A (not a System Wide Change)  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Contingency deadline: Final Freeze  <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 <!-- Does finishing this feature block the release, or can we ship with the feature in incomplete state? -->
-* Blocks release? N/A (not a System Wide Change), Yes/No <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
+* Blocks release? No <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 == Documentation ==
@@ Line 211: / Line 191: @@
 <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
-N/A (not a System Wide Change)
+LLVM sub-projects in Fedora have been updated to version 20:
+* llvm (now includes polly, llvm-bolt, libcxx, mlir)
+* flang
+* libclc
+* llvm-test-suite
 == Release Notes ==

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