1/* Copyright (C) 2005-2022 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <stdbool.h>
19#include <math.h>
20#include <complex.h>
21
22attribute_hidden
23long double _Complex
24__divtc3 (long double a, long double b, long double c, long double d)
25{
26 long double denom, ratio, x, y;
27
28 /* ??? We can get better behavior from logarithmic scaling instead of
29 the division. But that would mean starting to link libgcc against
30 libm. We could implement something akin to ldexp/frexp as gcc builtins
31 fairly easily... */
32 if (fabsl (x: c) < fabsl (x: d))
33 {
34 ratio = c / d;
35 denom = (c * ratio) + d;
36 x = ((a * ratio) + b) / denom;
37 y = ((b * ratio) - a) / denom;
38 }
39 else
40 {
41 ratio = d / c;
42 denom = (d * ratio) + c;
43 x = ((b * ratio) + a) / denom;
44 y = (b - (a * ratio)) / denom;
45 }
46
47 /* Recover infinities and zeros that computed as NaN+iNaN; the only cases
48 are nonzero/zero, infinite/finite, and finite/infinite. */
49 if (isnan (x) && isnan (y))
50 {
51 if (denom == 0.0 && (!isnan (a) || !isnan (b)))
52 {
53 x = copysignl (INFINITY, c) * a;
54 y = copysignl (INFINITY, c) * b;
55 }
56 else if ((isinf (a) || isinf (b))
57 && isfinite (c) && isfinite (d))
58 {
59 a = copysignl (isinf (a) ? 1 : 0, a);
60 b = copysignl (isinf (b) ? 1 : 0, b);
61 x = INFINITY * (a * c + b * d);
62 y = INFINITY * (b * c - a * d);
63 }
64 else if ((isinf (c) || isinf (d))
65 && isfinite (a) && isfinite (b))
66 {
67 c = copysignl (isinf (c) ? 1 : 0, c);
68 d = copysignl (isinf (d) ? 1 : 0, d);
69 x = 0.0 * (a * c + b * d);
70 y = 0.0 * (b * c - a * d);
71 }
72 }
73
74 return x + I * y;
75}
76

source code of glibc/math/divtc3.c