F35 Change: LLVM 13 (Self-Contained Change proposal)

[Ben Cotton]

https://fedoraproject.org/wiki/Changes/LLVM-13

== Summary ==
Update all llvm sub-projects in Fedora to version 13.

== Owner ==
* Name: [[User:tstellar| Tom Stellard]]
* Email: <tstellar(a)redhat.com&gt;


== Detailed Description ==
All llvm sub-projects in Fedora will be updated to version 13, and
there will be a soname version change for the llvm libraries.
Compatibility packages clang12 and llvm12 will be added to ensure that
packages that currently depend on clang and llvm version 12 libraries
will continue to work.


== 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.
** Request a side-tag.
** Build llvm12 and clang12 into the side-tag.
** When the upstream LLVM project releases version 12.0.0-rc1 (Late
July 2021), package this and build it into the side tag.
** Merge side-tag into rawhide prior to the f35 branch date.
** Continue packaging newer release candidates into rawhide and f35
until the final release is complete (Late September 2021)

* Other developers:
** Maintainers of packages that depend on clang-libs or llvm-libs will
need to update their spec files to depend on the clang12 and llvm12
compatibility packages if they want to rebuild their package and it
does not work with LLVM 13 yet.  The key point here is that spec file
changes are only needed if a package is going to be rebuilt after LLVM
13 is added to Fedora.  The compatibility packages will ensure that
already built packages continue to work.

* Release engineering: [https://pagure.io/releng/issues/10179]
* 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
13.

== User Experience ==
Users will benefit from new features and bug-fixes in the latest
version of LLVM.

== Dependencies ==
This change can be made without updating any other packages.  However,
as mention before, packages that need to use LLVM 12 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?):  If there are
major problems with LLVM 13, the compatibility package provide a way
for other packages to continue using LLVM 12.
* 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 13:

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

-- 
Ben Cotton
He / Him / His
Fedora Program Manager
Red Hat
TZ=America/Indiana/Indianapolis