Re: Implement C23 log2p1

[Carlos O'Donell <carlos@redhat.com>]

On 4/8/24 17:19, Joseph Myers wrote:
> C23 adds various <math.h> function families originally defined in TS
> 18661-4.  Add the log2p1 functions (log2(1+x): like log1p, but for
> base-2 logarithms).
> 
> This illustrates the intended structure of implementations of all
> these function families: define them initially with a type-generic
> template implementation.  If someone wishes to add type-specific
> implementations, it is likely such implementations can be both faster
> and more accurate than the type-generic one and can then override it
> for types for which they are implemented (adding benchmarks would be
> desirable in such cases to demonstrate that a new implementation is
> indeed faster).
> 
> The test inputs are copied from those for log1p.  Note that these
> changes make gen-auto-libm-tests depend on MPFR 4.2 (or later).
> 
> The bulk of the changes are fairly generic for any such new function.
> (sysdeps/powerpc/nofpu/Makefile only needs changing for those
> type-generic templates that use fabs.)
> 
> Tested for x86_64 and x86, and with build-many-glibcs.py.

This fails CI for glibc:
https://patchwork.sourceware.org/project/glibc/patch/41a4a6c9-4942-a9be-9459-1aaeb44ffee8@redhat.com/

Please review the results and work with Linaro to ensure this passes.

-- 
Cheers,
Carlos.