On Sat, 20 Sep 2025, Jon Turney wrote: > On 13/08/2025 18:33, Jeremy Drake via Cygwin-patches wrote: > > On Tue, 5 Aug 2025, Thirumalai Nagalingam wrote: > > > > > Hi all, > > > > > > This patch adds support for the `fsqrt` instruction on AArch64 platforms > > > in the `__FLT_ABI(sqrt)` implementation. > > > > This looks OK as far as it goes, but I have a few thoughts. > > > > From the comments, it appears this code originally came from mingw-w64. > > Their current version of this code has aarch64 implementations. The > > difference with this one is they have a version for float as well as > > double. The versions here seem to only be used for long double (which on > > aarch64 is the same as double). > > > > Given that long double is the same as double on aarch64, might it make > > sense to redirect/alias the long double names to the double > > implementations in the def file (cygwin.din) on aarch64, rather than > > providing two different implementations (one in newlib for double and one > > in this cygwin/math directory for long double)? It seems like that's > > asking for subtle discrepancies between the implementations. I'm not > > seeing any obvious preprocesor-like operations in gendef (mingw-w64 uses > > cpp to preprocess .def.in => .def files for arch-specific #ifdefs) so > > maybe this would be more complicated. > > Sorry about the long delay looking into this. > > So, I was about to apply Thiru's v2 patch, since that all seems reasonable to > me. But now I'm not so sure... > > I think that a good goal is to keep this file aligned with the mingw-w64 > version, if possible. > > If I'm understanding correctly, if we do that, this problem goes away, but at > the cost that fsqrtd and fsqrtl are potentially different (although surely > since it all boils down to a single instruction, that's never going to happen > :) )?
Right. Also, I expect whatever is done will need to be done with all the rest of the long double functions in winsup/cygwin/math also. I don't know if sqrt was intended as an exemplar before moving forward with the others, or if they really just had issues with this one.
