Hacker News new | ask | show | jobs
by devit 2434 days ago
Rust references should in general optimize better because they give stronger aliasing guarantees.

Even for slices, using get_unchecked(1..) to get a smaller subslice without bounds checking might be better than pointer arithmetic as long as the slice lengths get optimized away (i.e. they are never used and never passed to non-inlined functions).
2 comments
littlestymaar 2433 days ago
> Rust references should in general optimize better because they give stronger aliasing guarantees.

AFAIK this does not work atm due to a codegen bug in llvm (which can also affect code using restrict in C in some cases). This bug will get fixed one day, but most likely another bug will be revealed at this point… This part of LLVM was never really used in C as much as in Rust, so they keep finding bugs in it. Hopefully it will get fine in the long run, but I'm not holding my breath.

link
diamondlovesyou 2434 days ago
You can just pass a reference/mut ref to the first element of the slice. This is actually how the generated kernels in my Rav1e PR do it, just for the aliasing reason you mentioned.
link