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| 1 | /* Used by sinf, cosf and sincosf functions. |
|---|---|
| 2 | Copyright (C) 2018-2022 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with the GNU C Library; if not, see |
| 17 | <https://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | /* The constants and polynomials for sine and cosine. */ |
| 20 | typedef struct |
| 21 | { |
| 22 | double sign[4]; /* Sign of sine in quadrants 0..3. */ |
| 23 | double hpi_inv; /* 2 / PI ( * 2^24 if !TOINT_INTRINSICS). */ |
| 24 | double hpi; /* PI / 2. */ |
| 25 | double c0, c1, c2, c3, c4; /* Cosine polynomial. */ |
| 26 | double s1, s2, s3; /* Sine polynomial. */ |
| 27 | } sincos_t; |
| 28 | |
| 29 | /* Compute the sine and cosine of inputs X and X2 (X squared), using the |
| 30 | polynomial P and store the results in SINP and COSP. N is the quadrant, |
| 31 | if odd the cosine and sine polynomials are swapped. */ |
| 32 | static inline void |
| 33 | sincosf_poly (double x, double x2, const sincos_t *p, int n, float *sinp, |
| 34 | float *cosp) |
| 35 | { |
| 36 | double x3, x4, x5, x6, s, c, c1, c2, s1; |
| 37 | |
| 38 | x4 = x2 * x2; |
| 39 | x3 = x2 * x; |
| 40 | c2 = p->c3 + x2 * p->c4; |
| 41 | s1 = p->s2 + x2 * p->s3; |
| 42 | |
| 43 | /* Swap sin/cos result based on quadrant. */ |
| 44 | float *tmp = (n & 1 ? cosp : sinp); |
| 45 | cosp = (n & 1 ? sinp : cosp); |
| 46 | sinp = tmp; |
| 47 | |
| 48 | c1 = p->c0 + x2 * p->c1; |
| 49 | x5 = x3 * x2; |
| 50 | x6 = x4 * x2; |
| 51 | |
| 52 | s = x + x3 * p->s1; |
| 53 | c = c1 + x4 * p->c2; |
| 54 | |
| 55 | *sinp = s + x5 * s1; |
| 56 | *cosp = c + x6 * c2; |
| 57 | } |
| 58 | |
| 59 | /* Return the sine of inputs X and X2 (X squared) using the polynomial P. |
| 60 | N is the quadrant, and if odd the cosine polynomial is used. */ |
| 61 | static inline float |
| 62 | sinf_poly (double x, double x2, const sincos_t *p, int n) |
| 63 | { |
| 64 | double x3, x4, x6, x7, s, c, c1, c2, s1; |
| 65 | |
| 66 | if ((n & 1) == 0) |
| 67 | { |
| 68 | x3 = x * x2; |
| 69 | s1 = p->s2 + x2 * p->s3; |
| 70 | |
| 71 | x7 = x3 * x2; |
| 72 | s = x + x3 * p->s1; |
| 73 | |
| 74 | return s + x7 * s1; |
| 75 | } |
| 76 | else |
| 77 | { |
| 78 | x4 = x2 * x2; |
| 79 | c2 = p->c3 + x2 * p->c4; |
| 80 | c1 = p->c0 + x2 * p->c1; |
| 81 | |
| 82 | x6 = x4 * x2; |
| 83 | c = c1 + x4 * p->c2; |
| 84 | |
| 85 | return c + x6 * c2; |
| 86 | } |
| 87 | } |
| 88 |
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