Arm Cortex-M85 Enablement Makes It Into GCC 13 With PACBTI Support
GCC 13 recently entered stage four development while this code was allowed to land as it shouldn't regress existing Arm processor support. Along with preparing the Arm Cortex-M85 target itself, this brings other Armv8.1-M work as well as enabling the Pointer Authentication and Branch Target Identification (PACBTI) extension with the compiler-side bits.
As part of the patch series, the -mbranch-protection compiler option is added for Arm to enable code generation for pointer signing and authentication instructions with function prologues and epilogues. Another patch also prepares Arm pointer authentication for the stack unwinding runtime.
All of this Armv8.1-M work and ultimately enabling -mpcu=cortex-m85 usage is now in GCC Git for the GCC 13.1 stable release likely to be out in the March~April timeframe.