LLVM Clang 15.0 Adds Arm Cortex-M85 Support

Support for Arm's Cortex-M85 based on Armv8.1-M has been added for the LLVM 15.0 compiler release this fall.

The Arm Cortex-M85 was announced back in April as the company's newest MCU-class core that offers significantly better performance than the Cortex M7 and M55 cores but for workloads not needing Cortex A-class performance. The Arm Cortex-M85 should be popular for next-gen IoT devices with better performance while also increasing security by supporting the Pointer Authentication and Branch Target Identification (PACBTI) extensions. The Helium vector extensions also continue to be available with the M85, Armv8-M TrustZone is present by default with the M85, and other improvements over prior Cortex-M designs.

Arm Cortex-M85

With LLVM/Clang already having support for Armv8.1-M, the Cortex-M85 enablement isn't too big. The newly added LLVM Git exposes the "-mcpu=cortex-m85" option for targeting the Cortex-M85 cores. By default the MVE and PACBTI extensions are enabled when targeting the M85 with Clang.

LLVM/Clang Arm Cortex-M85 details for those interested via this commit. LLVM 15.0 is planned for release in September. As of writing the Arm Cortex-M85 enablement hasn't yet landed in the GCC compiler but presumably that M85 patch will be coming in short order.