What is the purpose of the preprocessor define FLOAT_ABI_HARD in nRF52840 projects?

[owl-wy7n]

What is the purpose of the define FLOAT_ABI_HARD?  I'm seeing it defined in some nRF52840 projects.  I can't seem to find any documentation on it.

[AndreasF]

Hi.

The floating arithmetic can be done both in the FPU or the CPU. On the CPU it takes many more instructions for processing the same information as in the FPU. The given preprocessor instructs the compiler on how to process your float arithmetic. The FPU is still there in the chip, the Application decides whether to use it or not or a combination by instructing the compiler using this preprocessor.

 Best regards,

Andreas