LLVM 15.0.0git Release Notes


These are in-progress notes for the upcoming LLVM 15 release. Release notes for previous releases can be found on the Download Page.


This document contains the release notes for the LLVM Compiler Infrastructure, release 15.0.0git. Here we describe the status of LLVM, including major improvements from the previous release, improvements in various subprojects of LLVM, and some of the current users of the code. All LLVM releases may be downloaded from the LLVM releases web site.

For more information about LLVM, including information about the latest release, please check out the main LLVM web site. If you have questions or comments, the LLVM Developer’s Mailing List is a good place to send them.

Note that if you are reading this file from a Git checkout or the main LLVM web page, this document applies to the next release, not the current one. To see the release notes for a specific release, please see the releases page.

Non-comprehensive list of changes in this release

Update on required toolchains to build LLVM

With LLVM 15.x we will raise the version requirements of the toolchain used to build LLVM. The new requirements are as follows:

  • GCC >= 7.1
  • Clang >= 5.0
  • Apple Clang >= 9.3
  • Visual Studio 2019 >= 16.7

In LLVM 15.x these requirements will be “soft” requirements and the version check can be skipped by passing -DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN=ON to CMake.

With the release of LLVM 16.x these requirements will be hard and LLVM developers can start using C++17 features, making it impossible to build with older versions of these toolchains.

Changes to building LLVM

  • Omitting CMAKE_BUILD_TYPE when using a single configuration generator is now an error. You now have to pass -DCMAKE_BUILD_TYPE=<type> in order to configure LLVM. This is done to help new users of LLVM select the correct type: since building LLVM in Debug mode is very resource intensive, we want to make sure that new users make the choice that lines up with their usage. We have also improved documentation around this setting that should help new users. You can find this documentation here.

Changes to the ARM Backend

  • Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.
  • Added support for the Armv8.1-M PACBTI-M extension.
  • Added support for the Armv9-A, Armv9.1-A and Armv9.2-A architectures.
  • Added support for the Armv8.1-M PACBTI-M extension.
  • Removed the deprecation of ARMv8-A T32 Complex IT blocks. No deprecation warnings will be generated and -mrestrict-it is now always off by default. Previously it was on by default for Armv8 and off for all other architecture versions.

Changes to the RISC-V Backend

  • The Zvfh extension was added.

Changes to the C API

  • Add LLVMGetCastOpcode function to aid users of LLVMBuildCast in resolving the best cast operation given a source value and destination type. This function is a direct wrapper of CastInst::getCastOpcode.

Changes to the Debug Info

During this release …

Other Changes

  • The code for the LLVM Visual Studio integration has been removed. This had been obsolete and abandoned since Visual Studio started including an integration by default in 2019.

Additional Information

A wide variety of additional information is available on the LLVM web page, in particular in the documentation section. The web page also contains versions of the API documentation which is up-to-date with the Git version of the source code. You can access versions of these documents specific to this release by going into the llvm/docs/ directory in the LLVM tree.

If you have any questions or comments about LLVM, please feel free to contact us via the mailing lists.