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, 7 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 9ae04b2f20..6bc98873ab 100644
--- a/NEWS
+++ b/NEWS
@@ -32,6 +32,13 @@ Major new features:
   - ffma, ffmal, dfmal and corresponding fMfmafN, fMfmafNx, fMxfmafN and
     fMxfmafNx functions.
 
+* <math.h> functions for floating-point maximum and minimum,
+  corresponding to new operations in IEEE 754-2019, and corresponding
+  <tgmath.h> macros, are added from draft ISO C2X: fmaximum,
+  fmaximum_num, fmaximum_mag, fmaximum_mag_num, fminimum, fminimum_num,
+  fminimum_mag, fminimum_mag_num and corresponding functions for float,
+  long double, _FloatN and _FloatNx.
+
 * The __STDC_IEC_60559_BFP__ and __STDC_IEC_60559_COMPLEX__ macros are
   predefined as specified in TS 18661-1:2014.