Add fmaximum, fminimum functions

C2X adds new <math.h> functions for floating-point maximum and
minimum, corresponding to the new operations that were added in IEEE
754-2019 because of concerns about the old operations not being
associative in the presence of signaling NaNs.  fmaximum and fminimum
handle NaNs like most <math.h> functions (any NaN argument means the
result is a quiet NaN).  fmaximum_num and fminimum_num handle both
quiet and signaling NaNs the way fmax and fmin handle quiet NaNs (if
one argument is a number and the other is a NaN, return the number),
but still raise "invalid" for a signaling NaN argument, making them
exceptions to the normal rule that a function with a floating-point
result raising "invalid" also returns a quiet NaN.  fmaximum_mag,
fminimum_mag, fmaximum_mag_num and fminimum_mag_num are corresponding
functions returning the argument with greatest or least absolute
value.  All these functions also treat +0 as greater than -0.  There
are also corresponding <tgmath.h> type-generic macros.

Add these functions to glibc.  The implementations use type-generic
templates based on those for fmax, fmin, fmaxmag and fminmag, and test
inputs are based on those for those functions with appropriate
adjustments to the expected results.  The RISC-V maintainers might
wish to add optimized versions of fmaximum_num and fminimum_num (for
float and double), since RISC-V (F extension version 2.2 and later)
provides instructions corresponding to those functions - though it
might be at least as useful to add architecture-independent built-in
functions to GCC and teach the RISC-V back end to expand those
functions inline, which is what you generally want for functions that
can be implemented with a single instruction.

Tested for x86_64 and x86, and with build-many-glibcs.py.

1 files changed, 26 insertions, 0 deletions

diff --git a/math/bits/mathcalls.h b/math/bits/mathcalls.h
index dc145b4bcf..ee0c6d7219 100644
--- a/math/bits/mathcalls.h
+++ b/math/bits/mathcalls.h
@@ -378,6 +378,32 @@ __MATHCALLX (fmaxmag,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
 __MATHCALLX (fminmag,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
 #endif
 
+#if __GLIBC_USE (ISOC2X)
+/* Return maximum value from X and Y.  */
+__MATHCALLX (fmaximum,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
+
+/* Return minimum value from X and Y.  */
+__MATHCALLX (fminimum,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
+
+/* Return maximum numeric value from X and Y.  */
+__MATHCALLX (fmaximum_num,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
+
+/* Return minimum numeric value from X and Y.  */
+__MATHCALLX (fminimum_num,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
+
+/* Return value with maximum magnitude.  */
+__MATHCALLX (fmaximum_mag,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
+
+/* Return value with minimum magnitude.  */
+__MATHCALLX (fminimum_mag,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
+
+/* Return numeric value with maximum magnitude.  */
+__MATHCALLX (fmaximum_mag_num,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
+
+/* Return numeric value with minimum magnitude.  */
+__MATHCALLX (fminimum_mag_num,, (_Mdouble_ __x, _Mdouble_ __y), (__const__));
+#endif
+
 #if __GLIBC_USE (IEC_60559_EXT) || __MATH_DECLARING_FLOATN
 /* Total order operation.  */
 __MATHDECL_1 (int, totalorder,, (const _Mdouble_ *__x,