Normally you'd save more than just PC as AAPCS (https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aap...) mandates stack to be aligned to 8 bytes for "public interface" functions. But this is is not a "public" function so it's fine to only save lr here.
"bx lr" is only used on it's own when the function doesn't call another function (altering lr), and doesn't need to save any registers.
If you see pop {lr}; bx lr then that's code that's being compiled to explicitly support Armv4 (e.g. Arm7TDMI)
Comments
Normally you'd save more than just PC as AAPCS (https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aap...) mandates stack to be aligned to 8 bytes for "public interface" functions. But this is is not a "public" function so it's fine to only save lr here.
"bx lr" is only used on it's own when the function doesn't call another function (altering lr), and doesn't need to save any registers.
If you see pop {lr}; bx lr then that's code that's being compiled to explicitly support Armv4 (e.g. Arm7TDMI)
EDIT: https://gcc.godbolt.org/z/TadnqescT