Implement C23 atanpi

C23 adds various <math.h> function families originally defined in TS
18661-4.  Add the atanpi functions (atan(x)/pi).

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

math/Makefile

@@ -95,6 +95,7 @@ gen-libm-calls = \
   k_casinhF \
   s_acospiF \
   s_asinpiF \
+  s_atanpiF \
   s_cacosF  \
   s_cacoshF \
   s_canonicalizeF \
@@ -626,6 +627,7 @@ libm-test-funcs-auto = \
   atan \
   atan2 \
   atanh \
+  atanpi \
   cabs \
   cacos \
   cacosh \
@@ -936,6 +938,7 @@ tgmath3-macros = \
   atan \
   atan2 \
   atanh \
+  atanpi \
   carg \
   cbrt \
   ceil \
@@ -1320,6 +1323,7 @@ CFLAGS-s_asinpi.c += -fno-builtin-asinpil
 CFLAGS-s_atan.c += -fno-builtin-atanl
 CFLAGS-w_atan2.c += -fno-builtin-atan2l
 CFLAGS-w_atanh.c += -fno-builtin-atanhl
+CFLAGS-s_atanpi.c += -fno-builtin-atanpil
 CFLAGS-s_cabs.c += -fno-builtin-cabsl
 CFLAGS-s_cacos.c += -fno-builtin-cacosl
 CFLAGS-s_cacosh.c += -fno-builtin-cacoshl
@@ -1463,6 +1467,7 @@ CFLAGS-s_asinpi.c += -fno-builtin-asinpif32x -fno-builtin-asinpif64
 CFLAGS-s_atan.c += -fno-builtin-atanf32x -fno-builtin-atanf64
 CFLAGS-w_atan2.c += -fno-builtin-atan2f32x -fno-builtin-atan2f64
 CFLAGS-w_atanh.c += -fno-builtin-atanhf32x -fno-builtin-atanhf64
+CFLAGS-s_atanpi.c += -fno-builtin-atanpif32x -fno-builtin-atanpif64
 CFLAGS-s_cabs.c += -fno-builtin-cabsf32x -fno-builtin-cabsf64
 CFLAGS-s_cacos.c += -fno-builtin-cacosf32x -fno-builtin-cacosf64
 CFLAGS-s_cacosh.c += -fno-builtin-cacoshf32x -fno-builtin-cacoshf64
@@ -1592,6 +1597,7 @@ CFLAGS-s_asinpif.c += -fno-builtin-asinpif32
 CFLAGS-s_atanf.c += -fno-builtin-atanf32
 CFLAGS-w_atan2f.c += -fno-builtin-atan2f32
 CFLAGS-w_atanhf.c += -fno-builtin-atanhf32
+CFLAGS-s_atanpif.c += -fno-builtin-atanpif32
 CFLAGS-s_cabsf.c += -fno-builtin-cabsf32
 CFLAGS-s_cacosf.c += -fno-builtin-cacosf32
 CFLAGS-s_cacoshf.c += -fno-builtin-cacoshf32

math/Versions

@@ -657,12 +657,14 @@ libm {
     # Functions not involving _Float64x or _Float128, for all configurations.
     acospi; acospif; acospil; acospif32; acospif64; acospif32x;
     asinpi; asinpif; asinpil; asinpif32; asinpif64; asinpif32x;
+    atanpi; atanpif; atanpil; atanpif32; atanpif64; atanpif32x;
     cospi; cospif; cospil; cospif32; cospif64; cospif32x;
     sinpi; sinpif; sinpil; sinpif32; sinpif64; sinpif32x;
     tanpi; tanpif; tanpil; tanpif32; tanpif64; tanpif32x;
     # Functions involving _Float64x or _Float128, for some configurations.
     acospif64x; acospif128;
     asinpif64x; asinpif128;
+    atanpif64x; atanpif128;
     cospif64x; cospif128;
     sinpif64x; sinpif128;
     tanpif64x; tanpif128;

math/auto-libm-test-in

@@ -748,6 +748,46 @@ atanh -min
 atanh min_subnorm
 atanh -min_subnorm
 
+atanpi 0
+atanpi -0
+atanpi max
+atanpi -max
+atanpi 1
+atanpi -1
+atanpi 0.75
+atanpi 0x1p-5
+atanpi 0x1p-10
+atanpi 0x1p-15
+atanpi 0x1p-20
+atanpi 0x1p-25
+atanpi 0x1p-30
+atanpi 0x1p-35
+atanpi 0x1p-40
+atanpi 0x1p-45
+atanpi 0x1p-50
+atanpi 0x1p-55
+atanpi 0x1p-60
+atanpi 2.5
+atanpi 10
+atanpi 1e6
+atanpi 0x1p31
+atanpi 0x1p-100
+atanpi 0x1p-600
+atanpi 0x1p-10000
+atanpi -0x3.b02d84p-4
+atanpi -0x3.3fb708p-4
+atanpi -0x2.3249ap+0
+atanpi -0x1.363f46p+0
+atanpi -0x1.ad4c0ap+0
+atanpi -0x3.eb8e18p+0
+atanpi 0x3.53c188p+0
+atanpi -0x1.58c83p+0
+atanpi 0x1.626772p-1
+atanpi min
+atanpi -min
+atanpi min_subnorm
+atanpi -min_subnorm
+
 # cabs (x,y) == cabs (y,x).
 cabs 0.75 12.390625
 # cabs (x,y) == cabs (-x,y).

math/bits/mathcalls.h

@@ -70,6 +70,8 @@ __MATHCALL_VEC (tan,, (_Mdouble_ __x));
 __MATHCALL (acospi,, (_Mdouble_ __x));
 /* Arc sine of X, divided by pi.  */
 __MATHCALL (asinpi,, (_Mdouble_ __x));
+/* Arc tangent of X, divided by pi.  */
+__MATHCALL (atanpi,, (_Mdouble_ __x));
 
 /* Cosine of pi * X.  */
 __MATHCALL (cospi,, (_Mdouble_ __x));

math/gen-auto-libm-tests.c

@@ -539,6 +539,7 @@ static test_function test_functions[] =
     FUNC_mpfr_f_f ("atan", mpfr_atan, false),
     FUNC_mpfr_ff_f ("atan2", mpfr_atan2, false),
     FUNC_mpfr_f_f ("atanh", mpfr_atanh, false),
+    FUNC_mpfr_f_f ("atanpi", mpfr_atanpi, false),
     FUNC_mpc_c_f ("cabs", mpc_abs, false),
     FUNC_mpc_c_c ("cacos", mpc_acos, false),
     FUNC_mpc_c_c ("cacosh", mpc_acosh, false),

math/gen-tgmath-tests.py

@@ -744,6 +744,7 @@ class Tests(object):
         # TS 18661-4 functions.
         self.add_tests('acospi', 'r', ['r'])
         self.add_tests('asinpi', 'r', ['r'])
+        self.add_tests('atanpi', 'r', ['r'])
         self.add_tests('cospi', 'r', ['r'])
         self.add_tests('exp10', 'r', ['r'])
         self.add_tests('exp2m1', 'r', ['r'])

math/libm-test-atanpi.inc

@@ -0,0 +1,49 @@
+/* Test atanpi.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include "libm-test-driver.c"
+
+static const struct test_f_f_data atanpi_test_data[] =
+  {
+    TEST_f_f (atanpi, plus_infty, 0.5, ERRNO_UNCHANGED),
+    TEST_f_f (atanpi, minus_infty, -0.5, ERRNO_UNCHANGED),
+    TEST_f_f (atanpi, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (atanpi, -qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_f_f (atanpi, snan_value, qnan_value, INVALID_EXCEPTION),
+    TEST_f_f (atanpi, -snan_value, qnan_value, INVALID_EXCEPTION),
+
+    AUTO_TESTS_f_f (atanpi),
+  };
+
+static void
+atanpi_test (void)
+{
+  ALL_RM_TEST (atanpi, 0, atanpi_test_data, RUN_TEST_LOOP_f_f, END);
+}
+
+static void
+do_test (void)
+{
+  atanpi_test ();
+}
+
+/*
+ * Local Variables:
+ * mode:c
+ * End:
+ */

math/s_atanpi_template.c

@@ -0,0 +1,39 @@
+/* Return arc tangent of X, divided by pi.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <math.h>
+#include <math-narrow-eval.h>
+#include <math-underflow.h>
+
+FLOAT
+M_DECL_FUNC (__atanpi) (FLOAT x)
+{
+  FLOAT ret = math_narrow_eval (M_SUF (__atan) (x) / M_MLIT (M_PI));
+  if (__glibc_likely (!isnan (x)))
+    math_check_force_underflow (ret);
+  if (x != 0 && ret == 0)
+    __set_errno (ERANGE);
+  /* Ensure that rounding away from zero for both atan and the
+     division cannot yield a return value from atanpi with absolute
+     value greater than 0.5.  */
+  return (isgreater (M_FABS (ret), M_LIT (0.5))
+	  ? M_COPYSIGN (M_LIT (0.5), ret)
+	  : ret);
+}
+declare_mgen_alias (__atanpi, atanpi);

math/test-tgmath.c

@@ -48,7 +48,7 @@ volatile int count_cdouble;
 volatile int count_cfloat;
 volatile int count_cldouble;
 
-#define NCALLS     178
+#define NCALLS     180
 #define NCALLS_INT 4
 #define NCCALLS    47
 
@@ -241,6 +241,7 @@ F(compile_test) (void)
   b = asin (asin (a));
   a = tan (tan (x));
   b = tanpi (tanpi (x));
+  b = atanpi (atanpi (a));
   b = atan (atan (a));
   c = atan2 (atan2 (a, c), atan2 (b, x));
   a = cosh (cosh (x));
@@ -365,6 +366,7 @@ F(compile_test) (void)
       a = tan (y);
       a = tanpi (y);
       a = atan (y);
+      a = atanpi (y);
       a = atan2 (y, y);
       a = cosh (y);
       a = acosh (y);
@@ -565,6 +567,14 @@ TYPE
   return x + y;
 }
 
+TYPE
+(F(atanpi)) (TYPE x)
+{
+  ++count;
+  P ();
+  return x;
+}
+
 TYPE
 (F(cosh)) (TYPE x)
 {

math/tgmath.h

@@ -822,6 +822,8 @@
 # define acospi(Val) __TGMATH_UNARY_REAL_ONLY (Val, acospi)
 /* Arc sine of X, divided by pi..  */
 # define asinpi(Val) __TGMATH_UNARY_REAL_ONLY (Val, asinpi)
+/* Arc tangent of X, divided by pi.  */
+# define atanpi(Val) __TGMATH_UNARY_REAL_ONLY (Val, atanpi)
 
 /* Cosine of pi * X.  */
 # define cospi(Val) __TGMATH_UNARY_REAL_ONLY (Val, cospi)