What is new in LLVM 15?

By Arm Ltd

March 2, 2023

LLVM 15.0.0 was released on September 6, followed by a series of minor bug-fixing releases. Other than the regular architecture enablement work, Arm contributed several pieces of functionality. This includes support for frame chains in AArch32, SVE whole-loop scalable auto-vectorization and C/C++ operator support for ACLE types. The release also benefits from numerous performance improvements, both for A-profile and M-profile cores.

Architecture and IP support

LLVM 15 expands support for the A-profile architecture with the new Armv8.8-A and Armv9.3-A extensions. The most relevant change from a toolchain point of view is the addition of new instructions to improve the performance and portability of memcpy() and memset(). These can now be accessed through a series of ACLE intrinsics of the form __builtin_arm_mops*(). For more information on the full extensions, refer to the Arm A-Profile Architecture Developments 2021 blog post.

Another addition worth noting is support for the Arm Cortex-M85 processor. This is the highest-performance M-profile CPU to date, and is also the first CPU to allow the PACBTI Security Extension (optional). More info on the Cortex-M85 is available here. You can build for this CPU by adding -mcpu=cortex-m85 to your command line.

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