3 ms·
I am not 100% convinced this will perform as good on every armv8 implementation. Have you tried this on first gen v8 cores such as A53? I think that is the rea
by kramerger 3y ago
I am not 100% convinced this will perform as good on every armv8 implementation. Have you tried this on first gen v8 cores such as A53?
I think that is the reason GCC will not use it, although it may if you set the target CPU with -mcpu=
- monocasa 3y agoConditional moves tend to work even better on small in-order designs than later OoOE cores.
- kramerger 3y agoMy assumption is that larger designs means longer pipelines and that increases the penalty of missed conditional jumps. On a 3 or 5-stage pipeline things are not as bad.
- monocasa 3y agoSort of. The bigger issue is that in larger OoOE cores, the predicate ends up being a speculation barrier if you don't predict it. So you need hardware similar to a branch predictor guessing those predicates. At that point it's easier to just point people towards conditional jumps where you ostensibly have very good branch prediction if you have any sort of predictability and spend your gate budget there where it's more likely to be more generally used.