alt Hacker NewsI think this call for something similar to "__builtin_expect" or linux' likely()/unlikely().
Not very clean, but better than inserting obscure optimisations in the source.
Replies
purplesyringa • today at 9:59 AM
That would be great, if only it worked as intended! From the perspective of an optimizing compiler, `a == b ? a : b` is worse than `b` regardless of the probability you assign to `a == b`.
ETA: someone on Lobsters (https://lobste.rs/s/1an425/quadrupling_code_performance_with...) noticed that `[[unlikely]]` actually works on LLVM (not on GCC, and with worse codegen on LLVM, but it's still good to know) -- updated the post.
MaxBarraclough • today at 10:00 AM
I was wondering the same thing. Also, could profile-guided optimisation help here?
Assuming compilers are smart enough to insert an unnecessary branch to break the dependency.