On Wed, Jun 19, 2019 at 11:55:41PM +0000, Vineet Gupta wrote: > FWIW I tried to avoid all of this by using the 2 byte NOP_S and B_S variants > which > ensures we can never straddle cache line so the alignment issue goes away. > There's > a nice code size reduction too - see [1] . But I get build link errors in > networking code around DO_ONCE where the unlikely code is too much and offset > can't be encoded in signed 10 bits which B_S is allowed.
Yeah, so on x86 we have a 2 byte and a 5 byte relative jump and have the exact same issue. We're currently using 5 byte jumps unconditionally for the same reason. Getting it to use the 2 byte one where possible is a 'fun' project for someone with spare time at some point. It might need a GCC plugin to pull off, I've not put too much tought into it.
