Frame pointers on armv8-m

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?

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