Using gcc eabi 8.2.1 for armv8-m (Cortex M33). Compiling with -fno-omit-frame-pointer does not seem to store the frame pointer in any register. Is this not supported for the armv8-m architecture? I don't see an explicit FP defined for that architecture, but could a register still be reserved and used as FP?
It depends on what instruction set the compiler is set to. For thumb instruction codes, it is R7. For ARM instruction codes it is R11. I am working with an Atmel Cortex M7 that is compiling into thumb instructions. Do a disassembly and see what register interacts with the SP register at the beginning of the function.