Pi4 TARGET_CPU option

easyfab · July 26, 2020 at 4:46 PM

I see that RPi4 is build with TARGET_CPU="cortex-a53"

Is there a reason to not use TARGET_CPU="cortex-a72" ?

Could this make SW decoding faster ?

**HiassofT** · July 28, 2020 at 9:46 AM

Optimizing for cortex-a72 resulted in odd issues, see eg my comment here add support for Raspberry Pi 4 by HiassofT · Pull Request #3597 · LibreELEC/LibreELEC.tv · GitHub

Could be (or have been) some compiler/optimizer bug.

Other LE deveopers noticed similar issues on other devices as well so we stuck to cortex-a53 which works fine.

It's hard to tell if optimizing for cortex-a72 would give any real-world performance improvements and as digging into possible compiler bugs isn't fun we haven't investigated that further.

so long,

Hias

easyfab · July 29, 2020 at 9:57 AM

Thanks for pointing to the bug report.

I tried AV1 decoder ( libdav1d ) but I see it's almost fully optimized with NEON SIMD so it shouldn't really change anything.