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.

66 files changed, 3634 insertions, 11 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.
 
diff --git a/manual/arith.texi b/manual/arith.texi
index 6a158e624d..edb9cfdafb 100644
--- a/manual/arith.texi
+++ b/manual/arith.texi
@@ -2097,8 +2097,8 @@ and @var{y}.  It is similar to the expression
 @end smallexample
 except that @var{x} and @var{y} are only evaluated once.
 
-If an argument is NaN, the other argument is returned.  If both arguments
-are NaN, NaN is returned.
+If an argument is a quiet NaN, the other argument is returned.  If both arguments
+are NaN, or either is a signaling NaN, NaN is returned.
 @end deftypefun
 
 @deftypefun double fmax (double @var{x}, double @var{y})
@@ -2113,8 +2113,58 @@ are NaN, NaN is returned.
 The @code{fmax} function returns the greater of the two values @var{x}
 and @var{y}.
 
-If an argument is NaN, the other argument is returned.  If both arguments
-are NaN, NaN is returned.
+If an argument is a quiet NaN, the other argument is returned.  If both arguments
+are NaN, or either is a signaling NaN, NaN is returned.
+@end deftypefun
+
+@deftypefun double fminimum (double @var{x}, double @var{y})
+@deftypefunx float fminimumf (float @var{x}, float @var{y})
+@deftypefunx {long double} fminimuml (long double @var{x}, long double @var{y})
+@deftypefunx _FloatN fminimumfN (_Float@var{N} @var{x}, _Float@var{N} @var{y})
+@deftypefunx _FloatNx fminimumfNx (_Float@var{N}x @var{x}, _Float@var{N}x @var{y})
+@standards{C2X, math.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+The @code{fminimum} function returns the lesser of the two values @var{x}
+and @var{y}.  Unlike @code{fmin}, if either argument is a NaN, NaN is returned.
+Positive zero is treated as greater than negative zero.
+@end deftypefun
+
+@deftypefun double fmaximum (double @var{x}, double @var{y})
+@deftypefunx float fmaximumf (float @var{x}, float @var{y})
+@deftypefunx {long double} fmaximuml (long double @var{x}, long double @var{y})
+@deftypefunx _FloatN fmaximumfN (_Float@var{N} @var{x}, _Float@var{N} @var{y})
+@deftypefunx _FloatNx fmaximumfNx (_Float@var{N}x @var{x}, _Float@var{N}x @var{y})
+@standards{C2X, math.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+The @code{fmaximum} function returns the greater of the two values @var{x}
+and @var{y}.  Unlike @code{fmax}, if either argument is a NaN, NaN is returned.
+Positive zero is treated as greater than negative zero.
+@end deftypefun
+
+@deftypefun double fminimum_num (double @var{x}, double @var{y})
+@deftypefunx float fminimum_numf (float @var{x}, float @var{y})
+@deftypefunx {long double} fminimum_numl (long double @var{x}, long double @var{y})
+@deftypefunx _FloatN fminimum_numfN (_Float@var{N} @var{x}, _Float@var{N} @var{y})
+@deftypefunx _FloatNx fminimum_numfNx (_Float@var{N}x @var{x}, _Float@var{N}x @var{y})
+@standards{C2X, math.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+The @code{fminimum_num} function returns the lesser of the two values
+@var{x} and @var{y}.  If one argument is a number and the other is a
+NaN, even a signaling NaN, the number is returned.  Positive zero is
+treated as greater than negative zero.
+@end deftypefun
+
+@deftypefun double fmaximum_num (double @var{x}, double @var{y})
+@deftypefunx float fmaximum_numf (float @var{x}, float @var{y})
+@deftypefunx {long double} fmaximum_numl (long double @var{x}, long double @var{y})
+@deftypefunx _FloatN fmaximum_numfN (_Float@var{N} @var{x}, _Float@var{N} @var{y})
+@deftypefunx _FloatNx fmaximum_numfNx (_Float@var{N}x @var{x}, _Float@var{N}x @var{y})
+@standards{C2X, math.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+The @code{fmaximum_num} function returns the greater of the two values
+@var{x} and @var{y}.  If one argument is a number and the other is a
+NaN, even a signaling NaN, the number is returned.  Positive zero is
+treated as greater than negative zero.
 @end deftypefun
 
 @deftypefun double fminmag (double @var{x}, double @var{y})
@@ -2147,6 +2197,58 @@ have the same absolute value, or either is NaN, they behave the same
 as the @code{fmax} functions.
 @end deftypefun
 
+@deftypefun double fminimum_mag (double @var{x}, double @var{y})
+@deftypefunx float fminimum_magf (float @var{x}, float @var{y})
+@deftypefunx {long double} fminimum_magl (long double @var{x}, long double @var{y})
+@deftypefunx _FloatN fminimum_magfN (_Float@var{N} @var{x}, _Float@var{N} @var{y})
+@deftypefunx _FloatNx fminimum_magfNx (_Float@var{N}x @var{x}, _Float@var{N}x @var{y})
+@standards{C2X, math.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+These functions return whichever of the two values @var{x} and @var{y}
+has the smaller absolute value.  If both have the same absolute value,
+or either is NaN, they behave the same as the @code{fminimum}
+functions.
+@end deftypefun
+
+@deftypefun double fmaximum_mag (double @var{x}, double @var{y})
+@deftypefunx float fmaximum_magf (float @var{x}, float @var{y})
+@deftypefunx {long double} fmaximum_magl (long double @var{x}, long double @var{y})
+@deftypefunx _FloatN fmaximum_magfN (_Float@var{N} @var{x}, _Float@var{N} @var{y})
+@deftypefunx _FloatNx fmaximum_magfNx (_Float@var{N}x @var{x}, _Float@var{N}x @var{y})
+@standards{C2X, math.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+These functions return whichever of the two values @var{x} and @var{y}
+has the greater absolute value.  If both have the same absolute value,
+or either is NaN, they behave the same as the @code{fmaximum}
+functions.
+@end deftypefun
+
+@deftype