xref: /netbsd-src/lib/libm/ld128/s_sinpil.c (revision cfe182f36bde4c4d81e1607954ce22a67cf35d7a)
1*cfe182f3Schristos /*-
2*cfe182f3Schristos  * Copyright (c) 2017-2023 Steven G. Kargl
3*cfe182f3Schristos  * All rights reserved.
4*cfe182f3Schristos  *
5*cfe182f3Schristos  * Redistribution and use in source and binary forms, with or without
6*cfe182f3Schristos  * modification, are permitted provided that the following conditions
7*cfe182f3Schristos  * are met:
8*cfe182f3Schristos  * 1. Redistributions of source code must retain the above copyright
9*cfe182f3Schristos  *    notice unmodified, this list of conditions, and the following
10*cfe182f3Schristos  *    disclaimer.
11*cfe182f3Schristos  * 2. Redistributions in binary form must reproduce the above copyright
12*cfe182f3Schristos  *    notice, this list of conditions and the following disclaimer in the
13*cfe182f3Schristos  *    documentation and/or other materials provided with the distribution.
14*cfe182f3Schristos  *
15*cfe182f3Schristos  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16*cfe182f3Schristos  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17*cfe182f3Schristos  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18*cfe182f3Schristos  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19*cfe182f3Schristos  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20*cfe182f3Schristos  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21*cfe182f3Schristos  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22*cfe182f3Schristos  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23*cfe182f3Schristos  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24*cfe182f3Schristos  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25*cfe182f3Schristos  */
26*cfe182f3Schristos 
27*cfe182f3Schristos /*
28*cfe182f3Schristos  * See ../src/s_sinpi.c for implementation details.
29*cfe182f3Schristos  */
30*cfe182f3Schristos 
31*cfe182f3Schristos #include "math.h"
32*cfe182f3Schristos #include "math_private.h"
33*cfe182f3Schristos 
34*cfe182f3Schristos /*
35*cfe182f3Schristos  * pi_hi contains the leading 56 bits of a 169 bit approximation for pi.
36*cfe182f3Schristos  */
37*cfe182f3Schristos static const long double
38*cfe182f3Schristos pi_hi = 3.14159265358979322702026593105983920e+00L,
39*cfe182f3Schristos pi_lo = 1.14423774522196636802434264184180742e-17L;
40*cfe182f3Schristos 
41*cfe182f3Schristos #include "k_cospil.h"
42*cfe182f3Schristos #include "k_sinpil.h"
43*cfe182f3Schristos 
44*cfe182f3Schristos static volatile const double vzero = 0;
45*cfe182f3Schristos 
46*cfe182f3Schristos long double
sinpil(long double x)47*cfe182f3Schristos sinpil(long double x)
48*cfe182f3Schristos {
49*cfe182f3Schristos 	long double ai, ar, ax, hi, lo, s;
50*cfe182f3Schristos 
51*cfe182f3Schristos 	ax = fabsl(x);
52*cfe182f3Schristos 
53*cfe182f3Schristos 	if (ax < 1) {
54*cfe182f3Schristos 		if (ax < 0.25) {
55*cfe182f3Schristos 			if (ax < 0x1p-60) {
56*cfe182f3Schristos 				if (x == 0)
57*cfe182f3Schristos 					return (x);
58*cfe182f3Schristos 				hi = (double)x;
59*cfe182f3Schristos 				hi *= 0x1p113L;
60*cfe182f3Schristos 				lo = x * 0x1p113L - hi;
61*cfe182f3Schristos 				s = (pi_lo + pi_hi) * lo + pi_lo * lo +
62*cfe182f3Schristos 				    pi_hi * hi;
63*cfe182f3Schristos 				return (s * 0x1p-113L);
64*cfe182f3Schristos 			}
65*cfe182f3Schristos 
66*cfe182f3Schristos 			s = __kernel_sinpil(ax);
67*cfe182f3Schristos 			return (x < 0 ? -s : s);
68*cfe182f3Schristos 		}
69*cfe182f3Schristos 
70*cfe182f3Schristos 		if (ax < 0.5)
71*cfe182f3Schristos 			s = __kernel_cospil(0.5 - ax);
72*cfe182f3Schristos 		else if (ax < 0.75)
73*cfe182f3Schristos 			s = __kernel_cospil(ax - 0.5);
74*cfe182f3Schristos 		else
75*cfe182f3Schristos 			s = __kernel_sinpil(1 - ax);
76*cfe182f3Schristos 		return (x < 0 ? -s : s);
77*cfe182f3Schristos 	}
78*cfe182f3Schristos 
79*cfe182f3Schristos 	if (ax < 0x1p112) {
80*cfe182f3Schristos 		/* Split ax = ai + ar with 0 <= ar < 1. */
81*cfe182f3Schristos 		FFLOORL128(ax, ai, ar);
82*cfe182f3Schristos 
83*cfe182f3Schristos 		if (ar == 0) {
84*cfe182f3Schristos 			s = 0;
85*cfe182f3Schristos 		} else {
86*cfe182f3Schristos 			if (ar < 0.5) {
87*cfe182f3Schristos 				if (ar <= 0.25)
88*cfe182f3Schristos 					s = __kernel_sinpil(ar);
89*cfe182f3Schristos 				else
90*cfe182f3Schristos 					s = __kernel_cospil(0.5 - ar);
91*cfe182f3Schristos 			} else {
92*cfe182f3Schristos 				if (ar < 0.75)
93*cfe182f3Schristos 					s = __kernel_cospil(ar - 0.5);
94*cfe182f3Schristos 				else
95*cfe182f3Schristos 					s = __kernel_sinpil(1 - ar);
96*cfe182f3Schristos 			}
97*cfe182f3Schristos 
98*cfe182f3Schristos 			s = fmodl(ai, 2.L) == 0 ? s : -s;
99*cfe182f3Schristos 		}
100*cfe182f3Schristos 		return (x < 0 ? -s : s);
101*cfe182f3Schristos 	}
102*cfe182f3Schristos 
103*cfe182f3Schristos 	if (isinf(x) || isnan(x))
104*cfe182f3Schristos 		return (vzero / vzero);
105*cfe182f3Schristos 
106*cfe182f3Schristos 	/*
107*cfe182f3Schristos 	 * |x| >= 0x1p112 is always an integer, so return +-0.
108*cfe182f3Schristos 	 */
109*cfe182f3Schristos 	return (copysignl(0, x));
110*cfe182f3Schristos }
111