Implement C23 log2p1

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.

1 files changed, 1 insertions, 0 deletions

diff --git a/math/gen-tgmath-tests.py b/math/gen-tgmath-tests.py
index d3a7f65899..1131481fad 100755
--- a/math/gen-tgmath-tests.py
+++ b/math/gen-tgmath-tests.py
@@ -743,6 +743,7 @@ class Tests(object):
                 self.add_tests(prefix + fn, ret, ['r'] * args)
         # TS 18661-4 functions.
         self.add_tests('exp10', 'r', ['r'])
+        self.add_tests('log2p1', 'r', ['r'])
         # C23 functions.
         self.add_tests('fmaximum', 'r', ['r', 'r'])
         self.add_tests('fmaximum_mag', 'r', ['r', 'r'])