Chapter 5. Changes in LLVM Toolset 21.1.8

Red Hat Enterprise Linux is distributed with LLVM Toolset version 21.1.8.

LLVM Toolset 21.1.8:
- Upstream LLVM 21.1.8 is the last planned release in the LLVM 21.1.x line.
- Maintenance fixes include corrections in ExtractAPI typedef formatting, the SelectOptimize pass for large integer immediates, and the WebAssembly back end (handling of locals).
- ClangFormat includes regression and crash fixes for star annotation before lambdas, AlignArrayOfStructures, and qualifier placement with override.
- The Realtime Sanitizer (RTSan) handles attributed IR function declarations more reliably.
- Compiler-rt includes a sanitizer build fix for 32-bit x86 on Haiku. This change does not affect typical Red Hat Enterprise Linux builds but reflects upstream stabilization.
LLVM 21 (when you migrate from LLVM Toolset 20):
- LLVM 21 introduces IR and attribute updates, including replacing nocapture with captures(none) in LLVM IR. Bitcode is upgraded automatically; tools that parse LLVM IR as text might need updates.
- Clang and the LLVM back ends include further C and C++ conformance work, target-specific improvements, and debugger updates. Review the upstream notes if you rely on specific language options, warning behavior, or CPU tuning models.

For LLVM 21.1.8 source and the list of cherry-picked changes, see the LLVM 21.1.8 release announcement and the llvmorg-21.1.8 tag on GitHub. For the LLVM 21.1 feature set, see the LLVM release notes and Clang release notes.

LLVM Toolset is a rolling Application Stream, and only the latest version is supported. For more information, see the Red Hat Enterprise Linux Application Streams Life Cycle document.