On Tue, 7 May 2024 at 15:11, Jonathan Wakely <jwak...@redhat.com> wrote: > > On Tue, 7 May 2024 at 15:06, Jonathan Wakely wrote: > > > > On Tue, 7 May 2024 at 14:57, Jeff Law wrote: > > > > > > > > > > > > On 5/7/24 7:49 AM, Jonathan Wakely wrote: > > > > Do we want this change for RISC-V, to fix PR113578? > > > > > > > > I haven't tested it on RISC-V, only on x86_64-linux (where it doesn't do > > > > anything). > > > > > > > > -- >8 -- > > > > > > > > libstdc++-v3/ChangeLog: > > > > > > > > PR libstdc++/113578 > > > > * include/std/ostream (operator<<(basic_ostream&, float)): > > > > Restore signbit after converting to double. > > > No strong opinion. One could argue that the existence of a > > > conditional like that inherently implies the generic code is dependent > > > on specific processor behavior which probably is unwise. But again, no > > > strong opinion. > > > > Yes, but I'm not aware of any other processors that lose the signbit > > like this, so in practice it's always worked fine to cast the float to > > double. > > The similar glibc fix for strfrom is specific to RISC-V: > https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=0cc0033ef19bd3378445c2b851e53d7255cb1b1e
Looks like I spoke too soon and the same behaviour exists on Apple M1 chips. > > My patch uses copysign unconditionally, to avoid branching on isnan. I > don't know if that's the right choice.
