[hitlin37]

trying to understand a bit more about bitcode concept. Since a developer submits a bitcode for apple watch, does that mean he can't optimize his own app for performance?

FWIK, on android you can still optimize your app at assembly level and i think that's what motivates developers at times. Remember the iphone camera high speed shot app, that was hand coded to be fast on iphone.

[monocasa]

Bitcode can contain inline assembly still. Additionally, bitcode is significantly more tied to the target architecture than the author is assuming.