Floating Point Fun on Cortex-M Processors
59 points
1/21/1970
5 days ago
by hasheddan
Comments
Neywiny
3 days ago
glitchc
It's unclear why one would ever need to do this. Is it for power savings? What other use-cases would benefit from turning the FPU off between instructions?
3 days ago
russdill
There is overhead, and applications that don't use the FPU avoid that overhead. https://www.netbsd.org/docs/kernel/lazyfpu.html
3 days ago
Neywiny
Yes, for power savings. But I'd need to do a bit of a study on my code to see if it's even worth it. Since the majority of it doesn't use the FPU, it could help. But it might not be worth the effort.
3 days ago
bobmcnamara
Yes, you could turn it off every context switch.
3 days ago
summa_tech
Zephyr support lazy FPU context switches. So the downside from enabling FPU sharing is fairly limited.
3 days ago
Interesting. I was just thinking about this because of another post on floating point. I'm wondering if I can disable the fpu every so often and turn it on only if code needs it and it raises an exception.