Fancy-memcmp Alternatives

fancy-memcmp reviews and mentions

• Out-of-bounds read and write in the glibc's qsort()
  2 projects | news.ycombinator.com | 5 Feb 2024

  Hrm—that's another case of missing isel from gcc/clang (c.f. <https://pp.ipd.kit.edu/firm/selgen>)—my implementation (<https://github.com/moon-chilled/fancy-memcmp/blob/master/mem...>) does it in one less instruction. (An alternative is to skip the xors and do cmp/setcc/setcc/sub/movsx, which matches my approach on instruction count, but relies on good handling of partial renames, which is uarch-dependent. And I can never remember if anybody can eliminate movsx. Otoh it is non-destructive.)

• LLVM's Libc Gets Much Faster memcpy For RISC-V
  3 projects | news.ycombinator.com | 22 May 2023

  I only have experience with their amd64 code.

  > What problems do they have?

  Nothing in particular, just not particularly amazing performance. They work fine. One thing they have going for them is that they typically have separate versions for every interesting architecture feature level/set, whereas e.g. bionic only has sse code. I guess I can point at my own implementations of memset and memcmp (https://github.com/moon-chilled/fancy-memset https://github.com/moon-chilled/fancy-memcmp), both of which employ novel techniques not used by glibc; but I've not yet gotten around to doing proper benchmarks on either.