LLVM 9.0 RC3 is now out with official RISC-V support, updates to SystemZ and more

Last week, the LLVM team announced the release of LLVM 9.0 RC3, which fixes all the known release blockers. LLVM 9.0 missed its planned release date, which was 28th August. However, with the third RC out, we can expect it to be released soon in the coming weeks along with subprojects like Clang 9.0. LLVM 9.0 will include features like RISC-V official support, gfx10 support for AMDGPU compiler backend, among others.

Announcing the release, the team shared on the LLVM mailing list, “There are currently no open release blockers, which means if nothing new comes up, the final release could ship soon and this is what it would look like (except for more release notes, which are still very welcome).”

What’s new coming in LLVM 9.0

Official support for RISC-V target

In July this year, Alex Bradbury, CTO and Co-Founder of the lowRISC project proposed to make the “experimental” RISC-V LLVM backend “official” for LLVM 9.0. This essentially means that starting with this release, the RISC-V backend will be built by default for LLVM. Developers will be able to use it for standard LLVM/Clang builds out of the box.

Explaining the reason behind this update, Bradbury wrote in the proposal, “As well as being more convenient for end users, this also makes it significantly easier for e.g. Rust/Julia/Swift and other languages using LLVM for code generation to do so using the system-provided LLVM libraries. This will make life easier for those working on RISC-V ports of Linux distros encountering issues with Rust dependencies.”

Updates to the SystemZ target

Starting from LLVM 9.0, the SystemZ target will support the ‘arch13’ architecture. It will include builtins for the new vector instructions, which can be enabled using the ‘-mzvector’ option. The compiler will also support and automatically generate alignment hints on vector load and store instructions.

Updates to the AMDGPU target

In LLVM 9.0, the function call support is enabled by default. Other updates include improved support for 96-bit loads and stores, gfx10 support, and DPP combiner pass enabled by default.