2 ms·
Meanwhile, GCC will happily implement bsearch() without cmov instructions and the result will be slower than a custom implementation on which it emits cmov inst
by ryao 1y ago
Meanwhile, GCC will happily implement bsearch() without cmov instructions and the result will be slower than a custom implementation on which it emits cmov instructions. I do not believe anyone has filed a bug report specifically about the inefficient bsearch(), but the bug report I filed a few years ago on inefficient code generation for binary search functions is still open, so I see no point in bothering:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110001 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110001
Binary searches on OpenZFS B-Tree nodes are faster in part because we did not wait for the compiler:
https://github.com/openzfs/zfs/commit/677c6f8457943fe5b56d7aa8807010a104563e4a https://github.com/openzfs/zfs/commit/677c6f8457943fe5b56d7a...
Eliminating comparator function overhead via inlining is also a part of the improvement, which we would not have had because the OpenZFS code is not built with LTO, so even if the compiler fixes that bug, the patch will still have been useful.