** Description changed: SRU: Backport LLVM 18.1.8 to Ubuntu 24.04 LTS [ Impact ] * A newer Clang/LLVM version will be available for older releases as a - non-default LLVM selection. + non-default LLVM selection. This is particularly requested for building + Firefox. * On newer releases which had an older LLVM 18 release: some general bug fixes and improvements that release note may or may not mention: https://discourse.llvm.org/t/18-1-8-released/79725 (and mostly about PowerPC fixes in 18.1.7). [ Test Plan ] * Run autopkgtests on reverse dependencies. * On LTS releases which don't currently have LLVM 18, we can just examine the builtin unittest results, the unit tests don't need to have a 100% pass rate because that's impossible even for the upstream sometimes. [ Where problems could occur ] * LLVM is a very large piece of software with a lot of moving parts. A lot could go wrong even in a minor release: optimizer misoptimizations, Clang behavior changes, library linkage changes, C/C++ UB (undefined behavior) handling changes, on-disk IR format change (maybe compatible/upgradable), change of "internal" C++ API parameters, and change of C API behaviors. * In the backport, since we will need to apply extra patches for LLVM to compile in an older LTS, more LLVM breakages may happen unnoticed as we don't really care about unittests provided by LLVM (because a lot of them don't function correctly on non-amd64 and non-arm64 platforms; a lot of LIT tests may require the build system to have the same environment as the upstream CI, which is by itself a moving target.). * In Focal backport, a RISC-V patch was added to fix LLVM code generation and internal linker behavior when targeting RISC-V. This is needed because LLVM is by default a cross-compiler that could generate any supported machine code on any supported platform (we also enabled LLVM Orc JIT remoting functionality, which allows LLVM JIT to transform LLVM IR into machine code over the network). This may pose extra risks since our binutils on Focal only supports RISC-V ABI v2.0 while LLVM 18 speaks RISC-V ABI v2.1 (whose linker identity string is incompatible with v2.0, which is quite counter-intuitive). The patch is needed for older binutils to correctly link the RISC-V binaries when the RISC-V targets contains these RISC-V standard CPU extensions: +I (i2p0) +M (i2p0) +A (i2p0) +F (i2p0) +D (i2p0) +Zicsr (i2p0 when using +G with binutils in 20.04, otherwise not understood with i2p1) +Zifencei +Zipause [ Other Info ] * [Noble-only] A test rebuild using these packages was done as described in LP: #2076024. * [Noble-only] The llvm-18 testsuite run during the build doesn't show regressions. * [Noble-only] The update exposes an underlinking of bpftrace, which should be SRUed at the same time. See LP: #2081848
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2075477 Title: SRU: Backport LLVM 18.1.8 to Ubuntu LTS To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/llvm-toolchain-18/+bug/2075477/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
